G2Cdb::Gene report

Gene id
G00001312
Gene symbol
GRIK2 (HGNC)
Species
Homo sapiens
Description
glutamate receptor, ionotropic, kainate 2
Orthologue
G00000063 (Mus musculus)

Databases (8)

Curated Gene
OTTHUMG00000016328 (Vega human gene)
Gene
ENSG00000164418 (Ensembl human gene)
2898 (Entrez Gene)
17 (G2Cdb plasticity & disease)
GRIK2 (GeneCards)
Literature
138244 (OMIM)
Marker Symbol
HGNC:4580 (HGNC)
Protein Sequence
Q13002 (UniProt)

Synonyms (1)

  • MRT6

Diseases (6)

Disease Nervous effect Mutations Found Literature Mutations Type Genetic association?
D00000166: Schizophrenia Y Y (8942465) Repeat polymorphism (RP) N
D00000184: Huntington's disease Y Y (9108071) Repeat polymorphism (RP) Y
D00000184: Huntington's disease Y Y (10522893) Repeat polymorphism (RP) Y
D00000177: Autism Y Y (11920157) Single nucleotide polymorphism (SNP) Y
D00000166: Schizophrenia Y Y (12467946) Single nucleotide polymorphism (SNP) N
D00000308: Oculodentodigital dysplasia N Y (12584438) Single nucleotide polymorphism (SNP) ?
D00000184: Huntington's disease Y Y (12821179) Repeat polymorphism (RP) Y
D00000184: Huntington's disease Y Y (14755452) Repeat polymorphism (RP) Y
D00000174: Obsessive-compulsive disorder Y Y (15094479) Single nucleotide polymorphism (SNP) Y
D00000001: Acute lymphocytic leukaemia N Y (15205317) Single nucleotide polymorphism (SNP) Y
D00000166: Schizophrenia Y Y (15305151) Unknown (?) Y
D00000177: Autism Y Y (15389769) Single nucleotide polymorphism (SNP) Y
D00000184: Huntington's disease Y Y (16959037) Single nucleotide polymorphism (SNP) N
D00000184: Huntington's disease Y Y (17018562) Repeat polymorphism (RP) N

References

  • Replication of twelve association studies for Huntington's disease residual age of onset in large Venezuelan kindreds.

    Andresen JM, Gayán J, Cherny SS, Brocklebank D, Alkorta-Aranburu G, Addis EA, US-Venezuela Collaborative Research Group, Cardon LR, Housman DE and Wexler NS

    Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. jma@mit.edu

    Background: The major determinant of age of onset in Huntington's disease is the length of the causative triplet CAG repeat. Significant variance remains, however, in residual age of onset even after repeat length is factored out. Many genetic polymorphisms have previously shown evidence of association with age of onset of Huntington's disease in several different populations.

    Objective: To replicate these genetic association tests in 443 affected people from a large set of kindreds from Venezuela.

    Methods: Previously tested polymorphisms were analysed in the HD gene itself (HD), the GluR6 kainate glutamate receptor (GRIK2), apolipoprotein E (APOE), the transcriptional coactivator CA150 (TCERG1), the ubiquitin carboxy-terminal hydrolase L1 (UCHL1), p53 (TP53), caspase-activated DNase (DFFB), and the NR2A and NR2B glutamate receptor subunits (GRIN2A, GRIN2B).

    Results: The GRIN2A single-nucleotide polymorphism explains a small but considerable amount of additional variance in residual age of onset in our sample. The TCERG1 microsatellite shows a trend towards association but does not reach statistical significance, perhaps because of the uninformative nature of the polymorphism caused by extreme allele frequencies. We did not replicate the genetic association of any of the other genes.

    Conclusions: GRIN2A and TCERG1 may show true association with residual age of onset for Huntington's disease. The most surprising negative result is for the GRIK2 (TAA)(n) polymorphism, which has previously shown association with age of onset in four independent populations with Huntington's disease. The lack of association in the Venezuelan kindreds may be due to the extremely low frequency of the key (TAA)(16) allele in this population.

    Journal of medical genetics 2007;44;1;44-50

  • Genetic analysis of the GRIK2 modifier effect in Huntington's disease.

    Zeng W, Gillis T, Hakky M, Djoussé L, Myers RH, MacDonald ME and Gusella JF

    Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, USA. wzeng@coh.org

    Background: In Huntington's disease (HD), age at neurological onset is inversely correlated with the length of the CAG trinucleotide repeat mutation, but can be modified by genetic factors beyond the HD gene. Association of a relatively infrequent 16 TAA allele of a trinucleotide repeat polymorphism in the GRIK2 3'UTR with earlier than expected age at neurological onset has been suggested to reflect linkage disequilibrium with a functional polymorphism in GRIK2 or an adjacent gene.

    Results: We have tested this hypothesis by sequencing all GRIK2 exons, the exon-flanking sequences and 3'UTR in several individuals who were crucial to demonstrating the modifier effect, as they showed much earlier age at neurological onset than would be expected from the length of their HD CAG mutation. Though ten known SNPs were detected, no sequence variants were found in coding or adjacent sequence that could explain the modifier effect by linkage disequilibrium with the 16 TAA allele. Haplotype analysis using microsatellites, known SNPs and new variants discovered in the 3'UTR argues against a common ancestral origin for the 16 TAA repeat alleles in these individuals.

    Conclusion: These data suggest that the modifier effect is actually due to the TAA repeat itself, possibly via a functional consequence on the GRIK2 mRNA.

    Funded by: NINDS NIH HHS: NS16367, P50 NS016367

    BMC neuroscience 2006;7;62

  • Family-based association study between autism and glutamate receptor 6 gene in Chinese Han trios.

    Shuang M, Liu J, Jia MX, Yang JZ, Wu SP, Gong XH, Ling YS, Ruan Y, Yang XL and Zhang D

    Institute of Mental Health, Peking University, Beijing, China.

    The glutamate pathways are involved in diverse processes such as learning and memory, epilepsy, and they play important roles in neural plasticity, neural development, and neurodegeneration. It has been proposed that autism could be a hypoglutamatergic disorder. Recently, Jamain et al. reported that the glutamate receptor 6 (GluR6 or GRIK2) is in linkage disequilibrium with autism. In the present study, the transmission disequilibrium test (TDT) and the haplotype transmission were performed to analyze the four SNPs (SNP1: rs995640; SNP2: rs2227281; SNP3: rs2227283; SNP4: rs2235076) of GluR6 in 174 Chinese Han parent-offspring trios. The TDT demonstrated that the two SNPs (SNP2 and SNP3) showed preferential transmission (TDT P = 0.032). The global chi(2) test for haplotype transmission also revealed an association between GluR6 and autism (chi(2) = 10.78, df = 3, P = 0.013). Our results suggested that GluR6 is in linkage disequilibrium with autism.

    American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics 2004;131B;1;48-50

  • Maternal transmission disequilibrium of the glutamate receptor GRIK2 in schizophrenia.

    Bah J, Quach H, Ebstein RP, Segman RH, Melke J, Jamain S, Rietschel M, Modai I, Kanas K, Karni O, Lerer B, Gourion D, Krebs MO, Etain B, Schürhoff F, Szöke A, Leboyer M and Bourgeron T

    Human Genetics and Cognitive Functions, Universite Paris 7, Institut Pasteur, 25, rue du docteur Roux, 75724 Paris Cedex 15, France.

    Schizophrenia is characterized by thought disorders, hallucinations and delusions. Genetic studies have shown a high linkage at chromosome 6q16-21. Among the genes located in this region is the glutamate receptor ionotropic kainate 2 gene (GRIK2 or GLUR6), a functional candidate for susceptibility to schizophrenia. In this study, transmission of GRIK2 was evaluated in 356 schizophrenic patients from three different clinical centers. Whereas paternal transmission shows equilibrium, we observed maternal transmission disequilibrium of GRIK2 in the largest population (p=0.03), which was still significant when all populations were added (p=0.05). These results are similar to the maternal GRIK2 transmission disequilibrium previously reported for autism, and support the presence of a susceptibility gene for schizophrenia at 6q16.

    Neuroreport 2004;15;12;1987-91

  • A fluorescence in situ hybridization map of 6q deletions in acute lymphocytic leukemia: identification and analysis of a candidate tumor suppressor gene.

    Sinclair PB, Sorour A, Martineau M, Harrison CJ, Mitchell WA, O'Neill E and Foroni L

    Haematology Department, Royal Free and University College School of Medicine, London, United Kingdom.

    With the objective of identifying candidate tumor suppressor genes, we used fluorescence in situ hybridization to map leukemia-related deletions of the long arm of chromosome 6 (6q). Twenty of 24 deletions overlapped to define a 4.8-Mb region of minimal deletion between markers D6S1510 and D6S1692 within chromosome 6 band q16. Using reverse transcription-PCR, we found evidence of expression in hematopoietic cells for 3 of 15 genes in the region (GRIK2, C6orf111, and CCNC). Comparison between our own and published deletion data singled out GRIK2 as the gene most frequently affected by deletions of 6q in acute lymphocytic leukemia (ALL). Sequence analysis of GRIK2 in 14 ALL cases carrying heterozygous 6q deletions revealed a constitutional and paternally inherited C to G substitution in exon 6 encoding for an amino acid change in one patient. The substitution was absent among 232 normal alleles tested, leaving open the possibility that heterozygous carriers of such mutations may be susceptible to ALL. Although low in all normal hematopoietic tissues, quantitative reverse transcription-PCR showed higher baseline GRIK2 expression in thymus and T cells than other lineages. Among T-cell ALL patients, 6q deletion was associated with a statistically significant reduction in GRIK2 expression (P = 0.0001). By contrast, elevated GRIK2 expression was measured in the myelomonocytic line THP-1 and in one patient with common ALL. Finally, we detected significant levels of GRIK2 expression in prostate, kidney, trachea, and lung, raising the possibility that this gene may be protective against multiple tumor types.

    Cancer research 2004;64;12;4089-98

  • Frequency and transmission of glutamate receptors GRIK2 and GRIK3 polymorphisms in patients with obsessive compulsive disorder.

    Delorme R, Krebs MO, Chabane N, Roy I, Millet B, Mouren-Simeoni MC, Maier W, Bourgeron T and Leboyer M

    INSERM U 513, Faculté de Médecine, 8 rue du Général Sarrail, 94010 Créteil, France. delorme@im3.inserm.fr

    Several lines of evidence suggest that obsessive compulsive disorder (OCD) could be the consequence of glutamatergic dysfunction. We performed a case-control study in 156 patients and 141 controls and the transmission disequilibrium test in 124 parent-offspring trios to search for association between OCD and two kainate receptors, GRIK2 and GRIK3. Using three single nucleotide polymorphisms (SNP) in GRIK2 and one in GRIK3, we found no evidence for association in case-control or family-based analyses. Only the GRIK2 SNP I867, recently associated with autism, was less transmitted than expected (p < 0.03), supporting a functional role for this variant. These findings suggest the need for further investigation of the role of GRIK2 in OCD.

    Neuroreport 2004;15;4;699-702

  • The gender effect in juvenile Huntington disease patients of Italian origin.

    Cannella M, Gellera C, Maglione V, Giallonardo P, Cislaghi G, Muglia M, Quattrone A, Pierelli F, Di Donato S and Squitieri F

    Neurological Institute IRCCS Neuromed, Pozzilli (IS), Italy.

    We analyzed a population of juvenile Huntington disease (HD) subjects of Italian origin (n = 57). The main aim of this study was to analyze the gender effect of the affected parent on age at onset and clinical presentation of offspring with juvenile HD. We also analyzed molecular features of the disease, including CAG mutation length and GluR6 gene polymorphism, according to the affected parent's gender. The mutation length was longer in paternally than in maternally transmitted HD juvenile patients (P = 0.025), nevertheless a similar mean early onset in the two groups (P > 0.05). This data was even enforced by that obtained from the whole cohort of patients included in the databank (n = 600) where, in the presence of increased mean parent-child CAG repeat change in paternal vs. maternal meiotic transmissions (+7.3 vs. +0.7 CAG, P = 0.0002), the mean parent-child year-of-onset change was similar in the two groups (-10.4 and -7.0 years, P > 0.05). A lower TAA-triplet in GluR6 was associated with an earlier age at onset in juvenile patients (P = 0.031, R2 = 0.10). When we added the GluR6 effect on age at onset to the CAG expanded number effect (P = 0.0001, R2 = 0.68) by multiple regression approach, the coefficient of determination R2 increased to 0.81. This effect in addition to the expanded CAG repeat number, found in juvenile and not in adult patients, was slightly enforced by paternal compared to maternal transmissions (R2=0.82). Our findings suggest the occurrence of a weaker effect of the paternal mutation on juvenile age at onset in our population, possibly amplified by other genetic factors, such as the TAA-triplet length in the GluR6 gene.

    American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics 2004;125B;1;92-8

  • Modulation of age at onset in Huntington's disease and spinocerebellar ataxia type 2 patients originated from eastern India.

    Chattopadhyay B, Ghosh S, Gangopadhyay PK, Das SK, Roy T, Sinha KK, Jha DK, Mukherjee SC, Chakraborty A, Singhal BS, Bhattacharya AK and Bhattacharyya NP

    Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata 700 064, India.

    To identify the genetic modifier(s) that might alter the age at onset in Huntington's disease (HD) we have analyzed variations in GluR6 kainate receptor (GluR6), CA150 gene, Delta2642 and polymorphic CCG repeat variation in huntingtin (htt) gene in 77 HD patients and normal individuals. In addition, variation in the RAI1 gene was analyzed in 30 spinocerebellar ataxia (SCA2) patients and normal individuals to show the possible influence on the age at onset. Multiple regression analysis indicated that variation in GluR6 and CCG repeat genotype might explain 6.2% and 3.1%, respectively, of the variability in the age at onset in HD. Similar analysis with SCA2 patients indicated that RAI1 might explain about 13% of the variability in the age at onset. Specific alleles in GluR6 and CA150 locus were only observed in HD patients.

    Neuroscience letters 2003;345;2;93-6

  • Association study of polymorphisms in the GluR6 kainate receptor gene (GRIK2) with schizophrenia.

    Shibata H, Shibata A, Ninomiya H, Tashiro N and Fukumaki Y

    Division of Disease Genes, Research Center for Genetic Information, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.

    The glutamatergic dysfunction hypothesis of schizophrenia suggests genes involved in glutamatergic transmission as candidates for schizophrenia-susceptibility genes. The GluR6 kainate receptor gene GRIK2 is located on chromosome 6q16.3-q21, a schizophrenia susceptibility region, as suggested by multiple linkage studies. We examined 15 SNPs evenly distributed in the entire GRIK2 region (>700 kb) in Japanese patients with schizophrenia (n=100) and controls (n=100). Neither genotype nor allele frequency showed a significant association with the disorder. We constructed 2-SNP haplotypes from the 15 SNPs. Although we observed three long linkage disequilibrium blocks (>150 kb) within the GRIK2 region, none of the pairwise haplotypes showed a significant association with the disorder. Therefore, we conclude that GRIK2 does not play a major role in the pathogenesis of schizophrenia in the Japanese population.

    Psychiatry research 2002;113;1-2;59-67

  • Linkage and association of the glutamate receptor 6 gene with autism.

    Jamain S, Betancur C, Quach H, Philippe A, Fellous M, Giros B, Gillberg C, Leboyer M, Bourgeron T and Paris Autism Research International Sibpair (PARIS) Study

    Laboratoire d'Immunogénétique Humaine, INSERM E021, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris cedex 15, France.

    A genome scan was previously performed and pointed to chromosome 6q21 as a candidate region for autism. This region contains the glutamate receptor 6 (GluR6 or GRIK2) gene, a functional candidate for the syndrome. Glutamate is the principal excitatory neurotransmitter in the brain and is directly involved in cognitive functions such as memory and learning. We used two different approaches, the affected sib-pair (ASP) method and the transmission disequilibrium test (TDT), to investigate the linkage and association between GluR6 and autism. The ASP method, conducted with additional markers on the 51 original families and in eight new sibling pairs, showed a significant excess of allele sharing, generating an elevated multipoint maximum LOD score (ASPEX MLS = 3.28). TDT analysis, performed in the ASP families and in an independent data set of 107 parent-offspring trios, indicated a significant maternal transmission disequilibrium (TDTall P = 0.0004). Furthermore, TDT analysis (with only one affected proband per family) showed significant association between GluR6 and autism (TDT association P = 0.008). In contrast to maternal transmission, paternal transmission of GluR6 alleles was as expected in the absence of linkage, suggesting a maternal effect such as imprinting. Mutation screening was performed in 33 affected individuals, revealing several nucleotide polymorphisms (SNPs), including one amino acid change (M867I) in a highly conserved domain of the intracytoplasmic C-terminal region of the protein. This change is found in 8% of the autistic subjects and in 4% of the control population and seems to be more maternally transmitted than expected to autistic males (P = 0.007). Taken together, these data suggest that GluR6 is in linkage disequilibrium with autism.

    Molecular psychiatry 2002;7;3;302-10

  • Physical map of the chromosome 6q22 region containing the oculodentodigital dysplasia locus: analysis of thirteen candidate genes and identification of novel ESTs and DNA polymorphisms.

    Boyadjiev SA, Chowdry AB, Shapiro RE, Paznekas WA, Wandstrat AE, Choi JW, Kasch L, Zhang G, Wollnik B, Burgess CE, Schalling M, Lovett M and Jabs EW

    McKusick-Nathans Institute of Genetic Medicine, Center for Craniofacial Development and Disorders, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.

    Oculodentodigital dysplasia (ODDD) is an autosomal dominant condition with congenital anomalies of the craniofacial and limb regions and neurodegeneration. Genetic anticipation for the dysmorphic and neurologic features has been inferred in a few families. Our previous linkage studies have refined the ODDD candidate region to chromosome 6q22-->q23. In an attempt to clone the ODDD gene, we created a yeast artificial chromosome contig with 31 redundant clones spanning the region and identified and ordered candidate genes and markers. Fluorescent IN SITU hybridization mapped two of these YAC clones to chromosome 6q22.2 telomeric to a known 6q21 fragile site, excluding it as a possible cause of the suggested anticipation. We performed mutation analysis on thirteen candidate genes - GRIK2, HDAC2, COL10A1, PTD013, KPNA5, PIST, ROS1, BRD7, PLN, HSF2, PKIB, FABP7, and HEY2. Although no mutations were found, we identified 44 polymorphisms, including 28 single nucleotide polymorphisms. Direct cDNA selection was performed and fifty-five clones were found to contain sequences that were not previously reported as known genes or ESTs. These clones and polymorphisms will assist in the further characterization of this region and identification of disease genes.

    Funded by: NCRR NIH HHS: M01 RR00052; NHGRI NIH HHS: R01 HG00368; NICHD NIH HHS: R01 HD24061; NIDCR NIH HHS: R01 DE13849; NIGMS NIH HHS: T32 GM7471

    Cytogenetic and genome research 2002;98;1;29-37

  • Evidence for the GluR6 gene associated with younger onset age of Huntington's disease.

    MacDonald ME, Vonsattel JP, Shrinidhi J, Couropmitree NN, Cupples LA, Bird ED, Gusella JF and Myers RH

    Molecular Neurogenetics Unit, Massachusetts General Hospital, Harvard Medical School, Boston, USA.

    Huntington's disease (HD) is attributed to a triplet CAG repeat mutation, and about half of the variation in onset age can be explained by the size of the repeat expansion. Recently, a TAA repeat polymorphism in close linkage to the kainate receptor, GluR6, was reported related to onset age in HD. We examined this polymorphism in 258 unrelated HD-affected persons (172 from a clinic sample and 86 from a postmortem series). This study confirms that the 155 allele is associated with younger onset age of HD and suggests that it is in linkage disequilibrium with a variant of the GluR6 gene or another gene in this region.

    Funded by: NINDS NIH HHS: NS31862, R0-1NS16367

    Neurology 1999;53;6;1330-2

  • Genotypes at the GluR6 kainate receptor locus are associated with variation in the age of onset of Huntington disease.

    Rubinsztein DC, Leggo J, Chiano M, Dodge A, Norbury G, Rosser E and Craufurd D

    East Anglian Medical Genetics Service Molecular Genetics Laboratory, Addenbrooke's NHS Trust, Cambridge, United Kingdom.

    Huntington disease (HD) is associated with abnormal expansions of a CAG repeat close to the 5' end of the IT15 gene. We have assembled a set of 293 HD subjects whose ages of onset were known and sized their HD CAG repeats. These repeats accounted for 69% of the variance of age of onset when we used the most parsimonious model, which relates the logarithm of age of onset to a function of CAG repeat number. Since other familial factors have been proposed to influence the age of onset of HD, we have examined a number of candidate loci. The CAG repeat number on normal chromosomes, the delta2642 polymorphism in the HD gene, and apolipoprotein E genotypes did not affect the age of onset of HD. Although mitochondrial energy production defects in HD have led to suggestions that variants in the mitochondrial genome may be associated with clinical variability in HD, this suggestion was not supported by our preliminary experiments that examined the DdeI mitochondrial restriction fragment length polymorphism at position 10,394. Excitotoxicity has been a favored mechanism to explain the cell death in HD, particularly since intrastriatal injection of excitatory amino acids in animals creates HD-like pathology. Accordingly, we investigated the GluR6 kainate receptor. Of the variance in the age of onset of HD that was not accounted for by the CAG repeats, 13% could be attributed to GluR6 genotype variation. These data implicate GluR6-mediated excitotoxicity in the pathogenesis of HD and highlight the potential importance of this process in other polyglutamine repeat expansion diseases.

    Proceedings of the National Academy of Sciences of the United States of America 1997;94;8;3872-6

  • Lack of evidence for close linkage of the glutamate GluR6 receptor gene with schizophrenia.

    Chen AC, Kalsi G, Brynjolfsson J, Sigmundsson T, Curtis D, Butler R, Read T, Murphy P, Petursson H, Barnard EA and Gurling HM

    Department of Psychiatry, University College London Medical School, U.K.

    Objective: Previous research has consistently implicated genetic factors in the pathogenesis of schizophrenia. It has been hypothesized that an abnormality in glutamatergic function is of etiologic importance in schizophrenia, and therefore the glutamate receptor family of genes are potential susceptibility loci for schizophrenia. To test this hypothesis the authors sought to detect linkage between the GluR6 glutamate receptor gene and schizophrenia.

    Method: Twenty-three English and Icelandic families containing multiple cases of schizophrenia were genotyped with a microsatellite trinucleotide repeat polymorphism localized at the GluR6 glutamate receptor locus. Lod scores, model-free linkage analysis, and extended relative pair analysis were used to test for linkage.

    Results: No statistically significant evidence of linkage between GluR6 and schizophrenia was found.

    Conclusions: The results do not support the hypothesis that GluR6 allelic variants provide a major gene contribution to the etiology of schizophrenia in a large proportion of these pedigrees.

    Funded by: Wellcome Trust

    The American journal of psychiatry 1996;153;12;1634-6

Literature (62)

Pubmed - human_disease

  • Family-based association study between autism and glutamate receptor 6 gene in Chinese Han trios.

    Shuang M, Liu J, Jia MX, Yang JZ, Wu SP, Gong XH, Ling YS, Ruan Y, Yang XL and Zhang D

    Institute of Mental Health, Peking University, Beijing, China.

    The glutamate pathways are involved in diverse processes such as learning and memory, epilepsy, and they play important roles in neural plasticity, neural development, and neurodegeneration. It has been proposed that autism could be a hypoglutamatergic disorder. Recently, Jamain et al. reported that the glutamate receptor 6 (GluR6 or GRIK2) is in linkage disequilibrium with autism. In the present study, the transmission disequilibrium test (TDT) and the haplotype transmission were performed to analyze the four SNPs (SNP1: rs995640; SNP2: rs2227281; SNP3: rs2227283; SNP4: rs2235076) of GluR6 in 174 Chinese Han parent-offspring trios. The TDT demonstrated that the two SNPs (SNP2 and SNP3) showed preferential transmission (TDT P = 0.032). The global chi(2) test for haplotype transmission also revealed an association between GluR6 and autism (chi(2) = 10.78, df = 3, P = 0.013). Our results suggested that GluR6 is in linkage disequilibrium with autism.

    American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics 2004;131B;1;48-50

  • A fluorescence in situ hybridization map of 6q deletions in acute lymphocytic leukemia: identification and analysis of a candidate tumor suppressor gene.

    Sinclair PB, Sorour A, Martineau M, Harrison CJ, Mitchell WA, O'Neill E and Foroni L

    Haematology Department, Royal Free and University College School of Medicine, London, United Kingdom.

    With the objective of identifying candidate tumor suppressor genes, we used fluorescence in situ hybridization to map leukemia-related deletions of the long arm of chromosome 6 (6q). Twenty of 24 deletions overlapped to define a 4.8-Mb region of minimal deletion between markers D6S1510 and D6S1692 within chromosome 6 band q16. Using reverse transcription-PCR, we found evidence of expression in hematopoietic cells for 3 of 15 genes in the region (GRIK2, C6orf111, and CCNC). Comparison between our own and published deletion data singled out GRIK2 as the gene most frequently affected by deletions of 6q in acute lymphocytic leukemia (ALL). Sequence analysis of GRIK2 in 14 ALL cases carrying heterozygous 6q deletions revealed a constitutional and paternally inherited C to G substitution in exon 6 encoding for an amino acid change in one patient. The substitution was absent among 232 normal alleles tested, leaving open the possibility that heterozygous carriers of such mutations may be susceptible to ALL. Although low in all normal hematopoietic tissues, quantitative reverse transcription-PCR showed higher baseline GRIK2 expression in thymus and T cells than other lineages. Among T-cell ALL patients, 6q deletion was associated with a statistically significant reduction in GRIK2 expression (P = 0.0001). By contrast, elevated GRIK2 expression was measured in the myelomonocytic line THP-1 and in one patient with common ALL. Finally, we detected significant levels of GRIK2 expression in prostate, kidney, trachea, and lung, raising the possibility that this gene may be protective against multiple tumor types.

    Cancer research 2004;64;12;4089-98

  • The gender effect in juvenile Huntington disease patients of Italian origin.

    Cannella M, Gellera C, Maglione V, Giallonardo P, Cislaghi G, Muglia M, Quattrone A, Pierelli F, Di Donato S and Squitieri F

    Neurological Institute IRCCS Neuromed, Pozzilli (IS), Italy.

    We analyzed a population of juvenile Huntington disease (HD) subjects of Italian origin (n = 57). The main aim of this study was to analyze the gender effect of the affected parent on age at onset and clinical presentation of offspring with juvenile HD. We also analyzed molecular features of the disease, including CAG mutation length and GluR6 gene polymorphism, according to the affected parent's gender. The mutation length was longer in paternally than in maternally transmitted HD juvenile patients (P = 0.025), nevertheless a similar mean early onset in the two groups (P > 0.05). This data was even enforced by that obtained from the whole cohort of patients included in the databank (n = 600) where, in the presence of increased mean parent-child CAG repeat change in paternal vs. maternal meiotic transmissions (+7.3 vs. +0.7 CAG, P = 0.0002), the mean parent-child year-of-onset change was similar in the two groups (-10.4 and -7.0 years, P > 0.05). A lower TAA-triplet in GluR6 was associated with an earlier age at onset in juvenile patients (P = 0.031, R2 = 0.10). When we added the GluR6 effect on age at onset to the CAG expanded number effect (P = 0.0001, R2 = 0.68) by multiple regression approach, the coefficient of determination R2 increased to 0.81. This effect in addition to the expanded CAG repeat number, found in juvenile and not in adult patients, was slightly enforced by paternal compared to maternal transmissions (R2=0.82). Our findings suggest the occurrence of a weaker effect of the paternal mutation on juvenile age at onset in our population, possibly amplified by other genetic factors, such as the TAA-triplet length in the GluR6 gene.

    American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics 2004;125B;1;92-8

  • Association study of polymorphisms in the GluR6 kainate receptor gene (GRIK2) with schizophrenia.

    Shibata H, Shibata A, Ninomiya H, Tashiro N and Fukumaki Y

    Division of Disease Genes, Research Center for Genetic Information, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.

    The glutamatergic dysfunction hypothesis of schizophrenia suggests genes involved in glutamatergic transmission as candidates for schizophrenia-susceptibility genes. The GluR6 kainate receptor gene GRIK2 is located on chromosome 6q16.3-q21, a schizophrenia susceptibility region, as suggested by multiple linkage studies. We examined 15 SNPs evenly distributed in the entire GRIK2 region (>700 kb) in Japanese patients with schizophrenia (n=100) and controls (n=100). Neither genotype nor allele frequency showed a significant association with the disorder. We constructed 2-SNP haplotypes from the 15 SNPs. Although we observed three long linkage disequilibrium blocks (>150 kb) within the GRIK2 region, none of the pairwise haplotypes showed a significant association with the disorder. Therefore, we conclude that GRIK2 does not play a major role in the pathogenesis of schizophrenia in the Japanese population.

    Psychiatry research 2002;113;1-2;59-67

  • Physical map of the chromosome 6q22 region containing the oculodentodigital dysplasia locus: analysis of thirteen candidate genes and identification of novel ESTs and DNA polymorphisms.

    Boyadjiev SA, Chowdry AB, Shapiro RE, Paznekas WA, Wandstrat AE, Choi JW, Kasch L, Zhang G, Wollnik B, Burgess CE, Schalling M, Lovett M and Jabs EW

    McKusick-Nathans Institute of Genetic Medicine, Center for Craniofacial Development and Disorders, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.

    Oculodentodigital dysplasia (ODDD) is an autosomal dominant condition with congenital anomalies of the craniofacial and limb regions and neurodegeneration. Genetic anticipation for the dysmorphic and neurologic features has been inferred in a few families. Our previous linkage studies have refined the ODDD candidate region to chromosome 6q22-->q23. In an attempt to clone the ODDD gene, we created a yeast artificial chromosome contig with 31 redundant clones spanning the region and identified and ordered candidate genes and markers. Fluorescent IN SITU hybridization mapped two of these YAC clones to chromosome 6q22.2 telomeric to a known 6q21 fragile site, excluding it as a possible cause of the suggested anticipation. We performed mutation analysis on thirteen candidate genes - GRIK2, HDAC2, COL10A1, PTD013, KPNA5, PIST, ROS1, BRD7, PLN, HSF2, PKIB, FABP7, and HEY2. Although no mutations were found, we identified 44 polymorphisms, including 28 single nucleotide polymorphisms. Direct cDNA selection was performed and fifty-five clones were found to contain sequences that were not previously reported as known genes or ESTs. These clones and polymorphisms will assist in the further characterization of this region and identification of disease genes.

    Funded by: NCRR NIH HHS: M01 RR00052; NHGRI NIH HHS: R01 HG00368; NICHD NIH HHS: R01 HD24061; NIDCR NIH HHS: R01 DE13849; NIGMS NIH HHS: T32 GM7471

    Cytogenetic and genome research 2002;98;1;29-37

  • Evidence for the GluR6 gene associated with younger onset age of Huntington's disease.

    MacDonald ME, Vonsattel JP, Shrinidhi J, Couropmitree NN, Cupples LA, Bird ED, Gusella JF and Myers RH

    Molecular Neurogenetics Unit, Massachusetts General Hospital, Harvard Medical School, Boston, USA.

    Huntington's disease (HD) is attributed to a triplet CAG repeat mutation, and about half of the variation in onset age can be explained by the size of the repeat expansion. Recently, a TAA repeat polymorphism in close linkage to the kainate receptor, GluR6, was reported related to onset age in HD. We examined this polymorphism in 258 unrelated HD-affected persons (172 from a clinic sample and 86 from a postmortem series). This study confirms that the 155 allele is associated with younger onset age of HD and suggests that it is in linkage disequilibrium with a variant of the GluR6 gene or another gene in this region.

    Funded by: NINDS NIH HHS: NS31862, R0-1NS16367

    Neurology 1999;53;6;1330-2

  • Lack of evidence for close linkage of the glutamate GluR6 receptor gene with schizophrenia.

    Chen AC, Kalsi G, Brynjolfsson J, Sigmundsson T, Curtis D, Butler R, Read T, Murphy P, Petursson H, Barnard EA and Gurling HM

    Department of Psychiatry, University College London Medical School, U.K.

    Objective: Previous research has consistently implicated genetic factors in the pathogenesis of schizophrenia. It has been hypothesized that an abnormality in glutamatergic function is of etiologic importance in schizophrenia, and therefore the glutamate receptor family of genes are potential susceptibility loci for schizophrenia. To test this hypothesis the authors sought to detect linkage between the GluR6 glutamate receptor gene and schizophrenia.

    Method: Twenty-three English and Icelandic families containing multiple cases of schizophrenia were genotyped with a microsatellite trinucleotide repeat polymorphism localized at the GluR6 glutamate receptor locus. Lod scores, model-free linkage analysis, and extended relative pair analysis were used to test for linkage.

    Results: No statistically significant evidence of linkage between GluR6 and schizophrenia was found.

    Conclusions: The results do not support the hypothesis that GluR6 allelic variants provide a major gene contribution to the etiology of schizophrenia in a large proportion of these pedigrees.

    Funded by: Wellcome Trust

    The American journal of psychiatry 1996;153;12;1634-6

Pubmed - other

  • Differential regulation of kainate receptor trafficking by phosphorylation of distinct sites on GluR6.

    Nasu-Nishimura Y, Jaffe H, Isaac JT and Roche KW

    NINDS, National Institutes of Health, Bethesda, Maryland 20892, USA.

    Kainate receptors are widely expressed in the brain, and are present at pre- and postsynaptic sites where they play a prominent role in synaptic plasticity and the regulation of network activity. Within individual neurons, kainate receptors of different subunit compositions are targeted to various locations where they serve distinct functional roles. Despite this complex targeting, relatively little is known about the molecular mechanisms regulating kainate receptor subunit trafficking. Here we investigate the role of phosphorylation in the trafficking of the GluR6 kainate receptor subunit. We identify two specific residues on the GluR6 C terminus, Ser(846) and Ser(868), which are phosphorylated by protein kinase C (PKC) and dramatically regulate GluR6 surface expression. By using GluR6 containing phosphomimetic and nonphosphorylatable mutations for these sites expressed in heterologous cells or in neurons lacking endogenous GluR6, we show that phosphorylation of Ser(846) or Ser(868) regulates receptor trafficking through the biosynthetic pathway. Additionally, Ser(846) phosphorylation dynamically regulates endocytosis of GluR6 at the plasma membrane. Our findings thus demonstrate that phosphorylation of PKC sites on GluR6 regulates surface expression of GluR6 at distinct intracellular trafficking pathways, providing potential molecular mechanisms for the PKC-dependent regulation of synaptic kainate receptor function observed during various forms of synaptic plasticity.

    Funded by: Intramural NIH HHS

    The Journal of biological chemistry 2010;285;4;2847-56

  • Identification of new putative susceptibility genes for several psychiatric disorders by association analysis of regulatory and non-synonymous SNPs of 306 genes involved in neurotransmission and neurodevelopment.

    Gratacòs M, Costas J, de Cid R, Bayés M, González JR, Baca-García E, de Diego Y, Fernández-Aranda F, Fernández-Piqueras J, Guitart M, Martín-Santos R, Martorell L, Menchón JM, Roca M, Sáiz-Ruiz J, Sanjuán J, Torrens M, Urretavizcaya M, Valero J, Vilella E, Estivill X, Carracedo A and Psychiatric Genetics Network Group

    CIBER en Epidemiología y Salud Pública (CIBERESP), Instituto de Salud Carlos III, Madrid, Spain.

    A fundamental difficulty in human genetics research is the identification of the spectrum of genetic variants that contribute to the susceptibility to common/complex disorders. We tested here the hypothesis that functional genetic variants may confer susceptibility to several related common disorders. We analyzed five main psychiatric diagnostic categories (substance-abuse, anxiety, eating, psychotic, and mood disorders) and two different control groups, representing a total of 3,214 samples, for 748 promoter and non-synonymous single nucleotide polymorphisms (SNPs) at 306 genes involved in neurotransmission and/or neurodevelopment. We identified strong associations to individual disorders, such as growth hormone releasing hormone (GHRH) with anxiety disorders, prolactin regulatory element (PREB) with eating disorders, ionotropic kainate glutamate receptor 5 (GRIK5) with bipolar disorder and several SNPs associated to several disorders, that may represent individual and related disease susceptibility factors. Remarkably, a functional SNP, rs945032, located in the promoter region of the bradykinin receptor B2 gene (BDKRB2) was associated to three disorders (panic disorder, substance abuse, and bipolar disorder), and two additional BDKRB2 SNPs to obsessive-compulsive disorder and major depression, providing evidence for common variants of susceptibility to several related psychiatric disorders. The association of BDKRB2 (odd ratios between 1.65 and 3.06) to several psychiatric disorders supports the view that a common genetic variant could confer susceptibility to clinically related phenotypes, and defines a new functional hint in the pathophysiology of psychiatric diseases.

    American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics 2009;150B;6;808-16

  • Energetics of glutamate receptor ligand binding domain dimer assembly are modulated by allosteric ions.

    Chaudhry C, Plested AJ, Schuck P and Mayer ML

    Laboratory of Cellular and Molecular Neurophysiology, Porter Neuroscience Research Center, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.

    The activity of many ligand-gated ion channels and cell surface receptors is modulated by small molecules and ions, but an understanding of the underlying molecular mechanisms is scarce. For kainate, but not AMPA subtype glutamate receptors, the binding of Na(+) and Cl(-) ions to discrete, electrostatically coupled sites in the extracellular ligand binding domain (LBD) dimer assembly regulates the rate of entry into the desensitized state, which occurs when the dimer interface ruptures and the channel closes. Studies on glutamate receptors have defined the LBD dimer assembly as a key functional unit that controls activation and desensitization. Here we use analytical ultracentrifugation to probe the energetic effects of allosteric ions on kainate receptor dimer stability in solution, using a GluR6 mutant that desensitizes slowly. Our results show that sodium and chloride ions modulate kainate receptor dimer affinity as much as 50-fold, and that removal of either Cl(-) or Na(+) disrupts the dimer. The applicability of a similar allosteric mechanism for modulation of delta2 glutamate receptors by Ca(2+) was also tested. Our results indicate that ions can contribute substantial free energy to active state stabilization in both these receptors, and provide quantitative measurements of the energetic consequences of allosteric ion binding to a ligand-gated ion channel.

    Funded by: Intramural NIH HHS

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;30;12329-34

  • Genetic and clinical predictors of sexual dysfunction in citalopram-treated depressed patients.

    Perlis RH, Laje G, Smoller JW, Fava M, Rush AJ and McMahon FJ

    Department of Psychiatry, Massachusetts General Hospital, Boston, MA, USA. rperlis@partners.org

    Sexual dysfunction is a major contributor to treatment discontinuation and nonadherence among patients treated with selective serotonin reuptake inhibitors (SSRIs). The mechanisms by which depressive symptoms in general, as well as SSRI exposure in particular, may worsen sexual function are not known. We examined genetic polymorphisms, including those of the serotonin and glutamate systems, for association with erectile dysfunction, anorgasmia, and decreased libido during citalopram treatment. Clinical data were drawn from a nested case-control cohort derived from the STAR(*)D study, a multicenter, prospective, effectiveness trial in outpatients with nonpsychotic major depressive disorder (MDD). Self-reports of erectile dysfunction, decreased libido, or difficulty achieving orgasm based on the Patient-Rated Inventory of Side Effects were examined among Caucasian subjects (n=1473) for whom DNA and adverse effect measures were available, and who were treated openly with citalopram for up to 14 weeks. Of 1473 participants, 799 (54%) reported decreased libido; 525 (36%) reported difficulty achieving orgasm. Of 574 men, 211 (37%) reported erectile dysfunction. Using a set-based test for association, single nucleotide polymorphisms in glutamatergic genes were associated with decreased libido (GRIA3; GRIK2), difficulty achieving orgasm (GRIA1), and difficulty achieving erection (GRIN3A) (experiment-wide permuted p<0.05 for each). Evidence of association persisted after adjustment for baseline clinical and sociodemographic differences. Likewise, evidence of association was similar when the cohort was limited to those who did not report a given adverse event at the first post-baseline visit (ie, those whose adverse events were known to be treatment emergent). These hypothesis-generating analyses suggest the potential for glutamatergic treatment targets for sexual dysfunction during major depressive episodes.

    Funded by: NIMH NIH HHS: K23 MH067060

    Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology 2009;34;7;1819-28

  • Functional characterization and in silico docking of full and partial GluK2 kainate receptor agonists.

    Fay AM, Corbeil CR, Brown P, Moitessier N and Bowie D

    Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada.

    Two structural models have been developed to explain how agonist binding leads to ionotropic glutamate receptor (iGluR) activation. At alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) iGluRs, full and partial agonists close the agonist-binding domain (ABD) to different degrees whereas agonist-induced domain closure is apparently fixed at N-methyl-D-aspartate receptors. Although kainate (KA) iGluRs are thought to behave like AMPA receptors, the issue has not been formally tested because of the paucity of available receptor agonists. Here we identify a series of structurally related full and partial agonists at GluK2 (formerly GluR6) KARs and predict their docking mode using the in silico ligand-docking program FITTED. As expected, the neurotransmitter L-Glu behaved as a full agonist but modest reduction (e.g., L-serine or L-aspartate) or elongation (e.g., L-alpha-aminoadipate) in chain length generated weak partial agonists. It is noteworthy that in silico ligand-docking predicted that most partial agonists select for the closed and not, as expected, the open or intermediate conformations of the GluK2 ABD. Experiments using concanavalin-A to directly report conformations in the intact GluK2 receptor support this prediction with the full agonist, L-Glu, indistinguishable in this regard from weak partial agonists, D- and L-Asp. Exceptions to this were KA and domoate, which failed to elicit full closure as a result of steric hindrance by a key tyrosine residue. Our data suggest that alternative structural models need to be considered to describe agonist behavior at KARs. Finally, our study identifies the responsiveness to several neurotransmitter candidates establishing the possibility that endogenous amino acids other than L-Glu may regulate native KARs at central synapses.

    Molecular pharmacology 2009;75;5;1096-107

  • Genome-wide association study of smoking initiation and current smoking.

    Vink JM, Smit AB, de Geus EJ, Sullivan P, Willemsen G, Hottenga JJ, Smit JH, Hoogendijk WJ, Zitman FG, Peltonen L, Kaprio J, Pedersen NL, Magnusson PK, Spector TD, Kyvik KO, Morley KI, Heath AC, Martin NG, Westendorp RG, Slagboom PE, Tiemeier H, Hofman A, Uitterlinden AG, Aulchenko YS, Amin N, van Duijn C, Penninx BW and Boomsma DI

    Department of Biological Psychology, Center for Neurogenomic and Cognitive Research, VU University Amsterdam, The Netherlands. jm.vink@psy.vu.nl

    For the identification of genes associated with smoking initiation and current smoking, genome-wide association analyses were carried out in 3497 subjects. Significant genes that replicated in three independent samples (n = 405, 5810, and 1648) were visualized into a biologically meaningful network showing cellular location and direct interaction of their proteins. Several interesting groups of proteins stood out, including glutamate receptors (e.g., GRIN2B, GRIN2A, GRIK2, GRM8), proteins involved in tyrosine kinase receptor signaling (e.g., NTRK2, GRB14), transporters (e.g., SLC1A2, SLC9A9) and cell-adhesion molecules (e.g., CDH23). We conclude that a network-based genome-wide association approach can identify genes influencing smoking behavior.

    Funded by: NIMH NIH HHS: MH074027, MH077139, MH081802, R01 MH074027, R01 MH077139, R01 MH081802; Wellcome Trust

    American journal of human genetics 2009;84;3;367-79

  • Genome-wide association study of biochemical traits in Korcula Island, Croatia.

    Zemunik T, Boban M, Lauc G, Janković S, Rotim K, Vatavuk Z, Bencić G, Dogas Z, Boraska V, Torlak V, Susac J, Zobić I, Rudan D, Pulanić D, Modun D, Mudnić I, Gunjaca G, Budimir D, Hayward C, Vitart V, Wright AF, Campbell H and Rudan I

    University of Split School of Medicine, Soltanska 2, 21000 Split, Croatia.

    Aim: To identify genetic variants underlying biochemical traits--total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, uric acid, albumin, and fibrinogen, in a genome-wide association study in an isolated population where rare variants of larger effect may be more easily identified.

    Methods: The study included 944 adult inhabitants of the island of Korcula, as a part of larger DNA-based genetic epidemiological study in 2007. Biochemical measurements were performed in a single laboratory with stringent internal and external quality control procedures. Examinees were genotyped using Human Hap370CNV chip by Illumina, with a genome-wide scan containing 346027 single nucleotide polymorphisms (SNP).

    Results: A total of 31 SNPs were associated with 7 investigated traits at the level of P<1.00 x 10(-5). Nine of SNPs implicated the role of SLC2A9 in uric acid regulation (P=4.10 x 10(-6)-2.58 x 10(-12)), as previously found in other populations. All 22 remaining associations fell into the P=1.00 x 10(-5)-1.00 x 10(-6) significance range. One of them replicated the association between cholesteryl ester transfer protein (CETP) and HDL, and 7 associations were more than 100 kilobases away from the closest known gene. Nearby SNPs, rs4767631 and rs10444502, in gene kinase suppressor of ras 2 (KSR2) on chromosome 12 were associated with LDL cholesterol levels, and rs10444502 in the same gene with total cholesterol levels. Similarly, rs2839619 in gene PBX/knotted 1 homeobox 1 (PKNOX1) on chromosome 21 was associated with total and LDL cholesterol levels. The remaining 9 findings implied possible associations between phosphatidylethanolamine N-methyltransferase (PEMT) gene and total cholesterol; USP46, RAP1GDS1, and ZCCHC16 genes and triglycerides; BCAT1 and SLC14A2 genes and albumin; and NR3C2, GRIK2, and PCSK2 genes and fibrinogen.

    Conclusion: Although this study was underpowered for most of the reported associations to reach formal threshold of genome-wide significance under the assumption of independent multiple testing, replications of previous findings and consistency of association between the identified variants and more than one studied trait make such findings interesting for further functional follow-up studies. Changed allele frequencies in isolate population may contribute to identifying variants that would not be easily identified in much larger samples in outbred populations.

    Funded by: Medical Research Council: MC_U127561128

    Croatian medical journal 2009;50;1;23-33

  • The BTB/kelch protein, KRIP6, modulates the interaction of PICK1 with GluR6 kainate receptors.

    Laezza F, Wilding TJ, Sequeira S, Craig AM and Huettner JE

    Department of Cell Biology and Physiology, Washington University, St Louis, MO 63110, USA. flaezza@wustl.edu

    Neuronal proteins of the BTB/kelch and PDZ domain families interact with different regions of the cytoplasmic C-terminal domain of the GluR6 kainate receptor subunit. The BTB/kelch protein KRIP6 binds within a 58 amino acid segment of GluR6 proximal to the plasma membrane. In contrast, PDZ domain proteins, such as PICK1 and PSD95, interact with the last 4 residues of the GluR6 C-terminus. KRIP6 reduces peak currents mediated by recombinant GluR6 receptors and by native kainate receptors in neurons, whereas PICK1 stabilizes kainate receptors at synapses. Thus, protein-protein interactions at the C-terminal domain of GluR6 are important for regulating kainate receptor physiology. Here, we show by co-clustering and co-immunoprecipitation that KRIP6 interacts with PICK1 in heterologous cells. In addition, we demonstrate a novel modulation of GluR6 receptors by PICK1 resulting in increased peak current and relative desensitization of GluR6-mediated currents, phenotypes opposite to those produced by KRIP6. Importantly, these effects cancel out when KRIP6 and PICK1 are co-expressed together with GluR6. KRIP6 and PICK1 strongly co-cluster and co-immunoprecipitate regardless of the presence of GluR6. Immunofluorescence analysis reveals that GluR6 can either join the KRIP6-PICK1 clusters or remain separate; however, co-expression of KRIP6 reduces the fraction of PICK1 that co-immunoprecipitates with GluR6. Taken together, these results indicate that, in addition to a previously demonstrated direct interaction with the GluR6 C-terminal domain, KRIP6 regulates kainate receptors by inhibiting PICK1 modulation via competition or a mutual blocking effect.

    Funded by: NINDS NIH HHS: NS30888, NS39286, R01 NS030888, R01 NS030888-13, R01 NS039286

    Neuropharmacology 2008;55;7;1131-9

  • Luminescence resonance energy transfer investigation of conformational changes in the ligand binding domain of a kainate receptor.

    Du M, Rambhadran A and Jayaraman V

    Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030, USA.

    The apo state structure of the isolated ligand binding domain of the GluR6 subunit and the conformational changes induced by agonist binding to this protein have been investigated by luminescence resonance energy transfer (LRET) measurements. The LRET-based distances show that agonist binding induces cleft closure, and the extent of cleft closure is proportional to the extent of activation over a wide range of activations, thus establishing that the cleft closure conformational change is one of the mechanisms by which the agonist mediates receptor activation. The LRET distances also provide insight into the apo state structure, for which there is currently no crystal structure available. The distance change between the glutamate-bound state and the apo state is similar to that observed between the glutamate-bound and antagonist UBP-310-bound form of the GluR5 ligand binding domain, indicating that the cleft for the apo state of the GluR6 ligand binding domain should be similar to the UBP-310-bound form of GluR5. This observation implies that te apo state of GluR6 undergoes a cleft closure of 29-30 degrees upon binding full agonists, one of the largest observed in the glutamate receptor family.

    Funded by: NIGMS NIH HHS: R01 GM073102, R01 GM073102-02, R01 GM073102-03, R01GM073102

    The Journal of biological chemistry 2008;283;40;27074-8

  • Mutations to the kainate receptor subunit GluR6 binding pocket that selectively affect domoate binding.

    Zhang Y, Nayeem N and Green T

    Department of Pharmacology, School of Biomedical Sciences, University of Liverpool, Ashton Street, Liverpool L69 3GE, UK.

    Kainate receptor responses to domoate are characterized by large steady-state currents and slow deactivation kinetics. To improve our understanding of these responses, we mutated residues at the mouth of the agonist binding pocket of GluR6 using whole-cell electrophysiology to characterize the effects of the mutants. We identified two residues where mutations had significant ligand-specific effects. One, Met691, forms a hydrogen bond that seems to facilitate domoate binding by affecting the main-chain conformation. We found that mutation of Met691 to alanine significantly attenuated responses to domoate but had no effect on responses to glutamate, confirming the importance of this main-chain interaction in GluR6. The second residue, Val685, is located at the mouth of the binding pocket, adjacent to the domoate side-arm. Mutation of Val685 to glutamine increased the rate of decay from steady-state responses to domoate by more than 50-fold but had no effect on the rate or extent of desensitization or on the kinetics of responses to either glutamate or kainate. The V685Q mutant also significantly reduced the potencies of both glutamate (peak) and domoate (peak and steady-state). Empirical analysis using a basic kinetic model indicated that the V685Q phenotype could be fully explained by faster ligand dissociation. The V685Q mutant accelerated receptor deactivation without affecting either desensitization or gating, making it a potentially useful tool for further dissection of ligand binding and gating in kainate receptors.

    Funded by: Medical Research Council: G0200084

    Molecular pharmacology 2008;74;4;1163-9

  • Genetic markers within glutamate receptors associated with antidepressant treatment-emergent suicidal ideation.

    Menke A, Lucae S, Kloiber S, Horstmann S, Bettecken T, Uhr M, Ripke S, Ising M, Müller-Myhsok B, Holsboer F and Binder EB

    The American journal of psychiatry 2008;165;7;917-8

  • Molecular genetics of successful smoking cessation: convergent genome-wide association study results.

    Uhl GR, Liu QR, Drgon T, Johnson C, Walther D, Rose JE, David SP, Niaura R and Lerman C

    Molecular Neurobiology Research Branch, National Institutes of Health-Intramural Research Program, National Institute on Drug Abuse, 333 Cassell Dr, Ste 3510, Baltimore, MD 21224, USA. guhl@intra.nida.nih.gov

    Context: Smoking remains a major public health problem. Twin studies indicate that the ability to quit smoking is substantially heritable, with genetics that overlap modestly with the genetics of vulnerability to dependence on addictive substances.

    Objectives: To identify replicated genes that facilitate smokers' abilities to achieve and sustain abstinence from smoking (herein after referred to as quit-success genes) found in more than 2 genome-wide association (GWA) studies of successful vs unsuccessful abstainers, and, secondarily, to nominate genes for selective involvement in smoking cessation success with bupropion hydrochloride vs nicotine replacement therapy (NRT).

    Design: The GWA results in subjects from 3 centers, with secondary analyses of NRT vs bupropion responders.

    Setting: Outpatient smoking cessation trial participants from 3 centers.

    Participants: European American smokers who successfully vs unsuccessfully abstain from smoking with biochemical confirmation in a smoking cessation trial using NRT, bupropion, or placebo (N = 550).

    Quit-success genes, reproducibly identified by clustered nominally positive single-nucleotide polymorphisms (SNPs) in more than 2 independent samples with significant P values based on Monte Carlo simulation trials. The NRT-selective genes were nominated by clustered SNPs that display much larger t values for NRT vs placebo comparisons. The bupropion-selective genes were nominated by bupropion-selective results.

    Results: Variants in quit-success genes are likely to alter cell adhesion, enzymatic, transcriptional, structural, and DNA, RNA, and/or protein-handling functions. Quit-success genes are identified by clustered nominally positive SNPs from more than 2 samples and are unlikely to represent chance observations (Monte Carlo P< .0003). These genes display modest overlap with genes identified in GWA studies of dependence on addictive substances and memory.

    Conclusions: These results support polygenic genetics for success in abstaining from smoking, overlap with genetics of substance dependence and memory, and nominate gene variants for selective influences on therapeutic responses to bupropion vs NRT. Molecular genetics should help match the types and/or intensity of antismoking treatments with the smokers most likely to benefit from them.

    Funded by: Intramural NIH HHS; NCI NIH HHS: P50 CA084719, P50CA/DA84718, P50CA84719, R01 CA063562, R01CA 63562; NHLBI NIH HHS: HL32318; NIDA NIH HHS: 1K08 DA14276-05, DA08511, K08 DA014276, K08 DA014276-01A2, K08 DA014276-02, K08 DA014276-03, K08 DA014276-04, K08 DA014276-05

    Archives of general psychiatry 2008;65;6;683-93

  • Human GluR6c, a functional splicing variants of GluR6, is mainly expressed in non-nervous cells.

    Barbon A, Gervasoni A, LaVia L, Orlandi C, Jaskolski F, Perrais D and Barlati S

    Division of Biology and Genetics, Department of Biomedical Sciences and Biotechnologies, University of Brescia, Viale Europa 11, 25123 Brescia, Italy.

    Kainate-type glutamate receptors (KARs) are receptor channels with a variety of distinct physiological functions in synaptic transmission, depending on their sub-cellular location in functional neuronal compartments. The kainate receptor subunit GluR6 presents different splice variants involving the C-terminal domain, namely GluR6a, GluR6b and GluR6c. In this study, we report the analysis of the three human splicing isoforms and in particular of the uncharacterized hGluR6c. When expressed in COS-7 cells, hGluR6a receptor subunit was highly present on the surface of the plasma membrane, whereas hGluR6b and hGluRc were poorly transported to the membrane. Electrophysiological studies of homomeric receptors showed that hGluR6c subunit can generate functional receptors with characteristics similar to the GluR6b variant. mRNA expression analysis demonstrated that hGluR6c variant is mainly expressed in non-neuronal cells and barely expressed in neuronal ones. Interestingly, undifferentiated NT2 cells expressing only the hGluR6c isoform, during neuronal differentiation induced by retinoic acid, increased the expression level of the neuronal form hGluR6a with a parallel decreased of hGluR6c. Overall, our data indicate that hGluR6c might have unique properties in non-nervous cells and in the first stages of CNS development.

    Neuroscience letters 2008;434;1;77-82

  • Glutamate receptor 6 gene (GluR6 or GRIK2) polymorphisms in the Indian population: a genetic association study on autism spectrum disorder.

    Dutta S, Das S, Guhathakurta S, Sen B, Sinha S, Chatterjee A, Ghosh S, Ahmed S, Ghosh S and Usha R

    Manovikas Biomedical Research & Diagnostic Centre, Kolkata , 700 107, India.

    Autism is a neurodevelopmental disorder with early manifestation. It is a multifactorial disorder and several susceptible chromosomal regions for autism are identified through genome scan studies. The gene coding for glutamate receptor 6 (GluR6 or GRIK2) has been suggested as a candidate gene for autism based on its localization in the autism specific region on chromosome 6q21 and the involvement of receptor protein in cognitive functions like learning and memory. Despite its importance, so far no studies have been carried out on possible involvement of GluR6 with autism in the Indian population. Therefore in the present study, we have performed genetic analysis of three markers of GluR6 (SNP1: rs2227281, SNP2: rs2227283, SNP3: rs2235076) for possible association with autism through population, and family-based (TDT and HHRR) approaches. DSM-IV criteria and CARS/ADI-R have been utilized for diagnosis. Genotyping analysis for the SNPs has been carried out in 101 probands with autism spectrum disorder, 180 parents and 152 controls from different regions of India. Since the minor allele frequency of SNP3 was too low, the association studies have been carried out only for SNP1 and SNP2. Even though two earlier studies have shown association of these markers with autism, the present case-control and TDT, as well as HHRR analyses have not demonstrated any biased transmission of alleles or haplotypes to the affected offspring. Thus our results suggest that these markers of GluR6 are unlikely to be associated with autism in the Indian population.

    Cellular and molecular neurobiology 2007;27;8;1035-47

  • Functional consequences of natural substitutions in the GluR6 kainate receptor subunit ligand-binding site.

    Kistler T and Fleck MW

    Albany Medical College, Center for Neuroscience and Neuropharmacology, Albany, New York, USA.

    Differences in binding-site residues of GluR2 (AMPAR) and GluR6 (KAR) subunits have been identified that might account for their functional and pharmacological differences. Specifically, residues A518, A689 and N721 in GluR6 replace highly conserved threonine and serine residues found in other ionotropic glutamate receptor (iGluR) subunits. To define how these natural substitutions impact GluR6 function, we used patch clamp recording with ultrafast perfusion to characterize the effects of A518T, A689S and N721T on agonist potency, efficacy and response kinetics. We find these natural substitutions impact GluR6 function less than would be expected from reverse mutations in other iGluRs. There was little effect of individual or combined mutations on glutamate potency, deactivation or desensitization kinetics. Altered recovery kinetics were seen that were greatest after combined mutations. Kainate potency and response kinetics were also unchanged in the mutants, whereas kainate efficacy was reduced in A518T and increased the T/S/T mutant relative glutamate. Notably, A518T and A689S mutation permitted AMPA to bind as a weak competitive antagonist and the effects of these mutations were additive. N721T mutation further enhanced AMPA binding, allowing AMPA to activate and fully desensitize the receptors. Alternative mutations altering side chain length at position 518 produced far greater changes in glutamate affinity and response kinetics than did the natural mutations. We conclude that these nonconserved residues in GluR6 define the size of the agonist-binding pocket, exerting a steric influence on the bound agonist and the extent of binding-domain closure that can influence agonist potency, deactivation, desensitization and recovery kinetics.

    Funded by: NINDS NIH HHS: NS40347

    Channels (Austin, Tex.) 2007;1;6;417-28

  • A defect in the ionotropic glutamate receptor 6 gene (GRIK2) is associated with autosomal recessive mental retardation.

    Motazacker MM, Rost BR, Hucho T, Garshasbi M, Kahrizi K, Ullmann R, Abedini SS, Nieh SE, Amini SH, Goswami C, Tzschach A, Jensen LR, Schmitz D, Ropers HH, Najmabadi H and Kuss AW

    Max Planck Institute for Molecular Genetics, Charité Universitätsmedizin Berlin, Berlin, Germany.

    Nonsyndromic mental retardation is one of the most important unresolved problems in genetic health care. Autosomal forms are far more common than X-linked forms, but, in contrast to the latter, they are still largely unexplored. Here, we report a complex mutation in the ionotropic glutamate receptor 6 gene (GRIK2, also called "GLUR6") that cosegregates with moderate-to-severe nonsyndromic autosomal recessive mental retardation in a large, consanguineous Iranian family. The predicted gene product lacks the first ligand-binding domain, the adjacent transmembrane domain, and the putative pore loop, suggesting a complete loss of function of the GLU(K6) protein, which is supported by electrophysiological data. This finding provides the first proof that GLU(K6) is indispensable for higher brain functions in humans, and future studies of this and other ionotropic kainate receptors will shed more light on the pathophysiology of mental retardation.

    American journal of human genetics 2007;81;4;792-8

  • Family-based association study between GRIK2 polymorphisms and autism spectrum disorders in the Korean trios.

    Kim SA, Kim JH, Park M, Cho IH and Yoo HJ

    Department of Pharmacology, School of Medicine, Eulji University, Daejeon, Republic of Korea.

    Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with strong genetic components. The present study comprises the detection of four single nucleotide polymorphisms (SNPs) in GRIK2 followed by a family-based association analysis of the SNPs in 126 Korean ASD trios by using the transmission disequilibrium test (TDT) and haplotype analysis. We found preferential transmission of the C allele at the rs3213607 (P<0.001) of GRIK2 in ASD and haplotype analysis revealed that one haplotype demonstrated a significant association (P=0.023). These results suggest a potential association between GRIK2 and ASD in the Korean population.

    Neuroscience research 2007;58;3;332-5

  • Identification of C-terminal domain residues involved in protein kinase A-mediated potentiation of kainate receptor subtype 6.

    Kornreich BG, Niu L, Roberson MS and Oswald RE

    Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA.

    Glutamate receptors are the major excitatory receptors in the vertebrate CNS and have been implicated in a number of physiological and pathological processes. Previous work has shown that glutamate receptor function may be modulated by protein kinase A (PKA)-mediated phosphorylation, although the molecular mechanism of this potentiation has remained unclear. We have investigated the phosphorylation of specific amino acid residues in the C-terminal cytoplasmic domain of the rat kainate receptor subtype 6 (GluR6) as a possible mechanism for regulation of receptor function. The C-terminal tail of rat GluR6 can be phosphorylated by PKA on serine residues as demonstrated using [gamma-32P]ATP kinase assays. Whole cell recordings of transiently transfected human embryonic kidney (HEK) 293 cells showed that phosphorylation by PKA potentiates whole cell currents in wildtype GluR6 and that removal of the cytoplasmic C-terminal domain abolishes this potentiation. This suggested that the C-terminal domain may contain residue(s) involved in the PKA-mediated potentiation. Single mutations of each serine residue in the C-terminal domain (S815A, S825A, S828A, and S837A) and a truncation after position 855, which removes all threonines (T856, T864, and T875) from the domain, do not abolish PKA potentiation. However, the S825A/S837A mutation, but no other double mutation, abolishes potentiation. These results demonstrate that phosphorylation of the C-terminal tail of GluR6 by PKA leads to potentiation of whole cell response, and the combination of S825 and S837 in the C-terminal domain is a vital component of the mechanism of GluR6 potentiation by PKA.

    Funded by: NCRR NIH HHS: K01 RR000155, K01 RR000155-04

    Neuroscience 2007;146;3;1158-68

  • Replication of twelve association studies for Huntington's disease residual age of onset in large Venezuelan kindreds.

    Andresen JM, Gayán J, Cherny SS, Brocklebank D, Alkorta-Aranburu G, Addis EA, US-Venezuela Collaborative Research Group, Cardon LR, Housman DE and Wexler NS

    Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. jma@mit.edu

    Background: The major determinant of age of onset in Huntington's disease is the length of the causative triplet CAG repeat. Significant variance remains, however, in residual age of onset even after repeat length is factored out. Many genetic polymorphisms have previously shown evidence of association with age of onset of Huntington's disease in several different populations.

    Objective: To replicate these genetic association tests in 443 affected people from a large set of kindreds from Venezuela.

    Methods: Previously tested polymorphisms were analysed in the HD gene itself (HD), the GluR6 kainate glutamate receptor (GRIK2), apolipoprotein E (APOE), the transcriptional coactivator CA150 (TCERG1), the ubiquitin carboxy-terminal hydrolase L1 (UCHL1), p53 (TP53), caspase-activated DNase (DFFB), and the NR2A and NR2B glutamate receptor subunits (GRIN2A, GRIN2B).

    Results: The GRIN2A single-nucleotide polymorphism explains a small but considerable amount of additional variance in residual age of onset in our sample. The TCERG1 microsatellite shows a trend towards association but does not reach statistical significance, perhaps because of the uninformative nature of the polymorphism caused by extreme allele frequencies. We did not replicate the genetic association of any of the other genes.

    Conclusions: GRIN2A and TCERG1 may show true association with residual age of onset for Huntington's disease. The most surprising negative result is for the GRIK2 (TAA)(n) polymorphism, which has previously shown association with age of onset in four independent populations with Huntington's disease. The lack of association in the Venezuelan kindreds may be due to the extremely low frequency of the key (TAA)(16) allele in this population.

    Journal of medical genetics 2007;44;1;44-50

  • Genetic analysis of the GRIK2 modifier effect in Huntington's disease.

    Zeng W, Gillis T, Hakky M, Djoussé L, Myers RH, MacDonald ME and Gusella JF

    Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, USA. wzeng@coh.org

    Background: In Huntington's disease (HD), age at neurological onset is inversely correlated with the length of the CAG trinucleotide repeat mutation, but can be modified by genetic factors beyond the HD gene. Association of a relatively infrequent 16 TAA allele of a trinucleotide repeat polymorphism in the GRIK2 3'UTR with earlier than expected age at neurological onset has been suggested to reflect linkage disequilibrium with a functional polymorphism in GRIK2 or an adjacent gene.

    Results: We have tested this hypothesis by sequencing all GRIK2 exons, the exon-flanking sequences and 3'UTR in several individuals who were crucial to demonstrating the modifier effect, as they showed much earlier age at neurological onset than would be expected from the length of their HD CAG mutation. Though ten known SNPs were detected, no sequence variants were found in coding or adjacent sequence that could explain the modifier effect by linkage disequilibrium with the 16 TAA allele. Haplotype analysis using microsatellites, known SNPs and new variants discovered in the 3'UTR argues against a common ancestral origin for the 16 TAA repeat alleles in these individuals.

    Conclusion: These data suggest that the modifier effect is actually due to the TAA repeat itself, possibly via a functional consequence on the GRIK2 mRNA.

    Funded by: NINDS NIH HHS: NS16367, P50 NS016367

    BMC neuroscience 2006;7;62

  • Genetic analysis of candidate genes modifying the age-at-onset in Huntington's disease.

    Metzger S, Bauer P, Tomiuk J, Laccone F, Didonato S, Gellera C, Mariotti C, Lange HW, Weirich-Schwaiger H, Wenning GK, Seppi K, Melegh B, Havasi V, Balikó L, Wieczorek S, Zaremba J, Hoffman-Zacharska D, Sulek A, Basak AN, Soydan E, Zidovska J, Kebrdlova V, Pandolfo M, Ribaï P, Kadasi L, Kvasnicova M, Weber BH, Kreuz F, Dose M, Stuhrmann M and Riess O

    Department of Medical Genetics, University of Tübingen, Calwerstrasse 7, 72076, Tübingen, Germany.

    The expansion of a polymorphic CAG repeat in the HD gene encoding huntingtin has been identified as the major cause of Huntington's disease (HD) and determines 42-73% of the variance in the age-at-onset of the disease. Polymorphisms in huntingtin interacting or associated genes are thought to modify the course of the disease. To identify genetic modifiers influencing the age at disease onset, we searched for polymorphic markers in the GRIK2, TBP, BDNF, HIP1 and ZDHHC17 genes and analysed seven of them by association studies in 980 independent European HD patients. Screening for unknown sequence variations we found besides several silent variations three polymorphisms in the ZDHHC17 gene. These and polymorphisms in the GRIK2, TBP and BDNF genes were analysed with respect to their association with the HD age-at-onset. Although some of the factors have been defined as genetic modifier factors in previous studies, none of the genes encoding GRIK2, TBP, BDNF and ZDHHC17 could be identified as a genetic modifier for HD.

    Human genetics 2006;120;2;285-92

  • Functional significance of the kainate receptor GluR6(M836I) mutation that is linked to autism.

    Strutz-Seebohm N, Korniychuk G, Schwarz R, Baltaev R, Ureche ON, Mack AF, Ma ZL, Hollmann M, Lang F and Seebohm G

    Department of Physiology I, University of Tuebingen, Tuebingen, Germany.

    Previous studies revealed a linkage of the kainate receptor GluR6 with autism, a pervasive developmental disorder. Mutational screening in autistic patients disclosed the amino acid exchange M836I in a highly conserved domain of the cytoplasmic C-terminal region of GluR6. Here, we show that this mutation leads to GluR6 gain-of-function. By using the two-electrode voltage clamp technique we observed a significant increase of current amplitudes of mutant GluR6 compared to wild type GluR6. Western blotting of oocytes injected with mutant or wild type GluR6 cRNA and transfection of EGFP-tagged GluR6 receptors into COS-7 cells revealed an enhanced plasma membrane expression of GluR6(M836I) compared to wild type GluR6. Membrane expression of GluR6(M836I) but not of wild type GluR6 seems to be regulated by Rab11 as indicated by our finding that GluR6(M836I) but not wild type GluR6 showed increased current amplitudes and protein expression when coexpressed with Rab11. Furthermore, injection of GTP plus Rab11A protein into oocytes increased current amplitudes in GluR6(M836I) but not in wild type GluR6. By contrast, Rab5 downregulated the currents in oocytes expressing wild type GluR6 but had only little, statistically not significant effects on currents in oocytes expressing GluR6(M836I). Our data on altered functional properties of GluR6(M836I) provide a functional basis for the postulated linkage of GluR6 to autism. Furthermore, we identified new mechanisms determining the plasma membrane abundance of wild type GluR6 and GluR6(M836I).

    Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology 2006;18;4-5;287-94

  • Assessing the role of GLUK5 and GLUK6 at hippocampal mossy fiber synapses.

    Breustedt J and Schmitz D

    Neurowissenschaftliches Forschungszentrum, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany.

    It has been suggested recently that presynaptic kainate receptors (KARs) are involved in short-term and long-term synaptic plasticity at hippocampal mossy fiber synapses. Using genetic deletion and pharmacology, we here assess the role of GLU(K5) and GLU(K6) in synaptic plasticity at hippocampal mossy fiber synapses. We found that the kainate-induced facilitation was completely abolished in the GLU(K6)-/- mice, whereas it was unaffected in the GLU(K5)-/-. Consistent with this finding, synaptic facilitation was reduced in the GLU(K6)(-/-) and was normal in the GLU(K5)-/-. In agreement with these results and ruling out any compensatory effects in the genetic deletion models, application of the GLU(K5)-specific antagonist LY382884 [(3S,4aR,6S,8aR)-6-(4-carboxyphenyl)methyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylic acid] did not affect short-term and long-term synaptic plasticity at the hippocampal mossy fiber synapses. We therefore conclude that the facilitatory effects of kainate on mossy fiber synaptic transmission are mediated by GLU(K6)-containing KARs.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2004;24;45;10093-8

  • Maternal transmission disequilibrium of the glutamate receptor GRIK2 in schizophrenia.

    Bah J, Quach H, Ebstein RP, Segman RH, Melke J, Jamain S, Rietschel M, Modai I, Kanas K, Karni O, Lerer B, Gourion D, Krebs MO, Etain B, Schürhoff F, Szöke A, Leboyer M and Bourgeron T

    Human Genetics and Cognitive Functions, Universite Paris 7, Institut Pasteur, 25, rue du docteur Roux, 75724 Paris Cedex 15, France.

    Schizophrenia is characterized by thought disorders, hallucinations and delusions. Genetic studies have shown a high linkage at chromosome 6q16-21. Among the genes located in this region is the glutamate receptor ionotropic kainate 2 gene (GRIK2 or GLUR6), a functional candidate for susceptibility to schizophrenia. In this study, transmission of GRIK2 was evaluated in 356 schizophrenic patients from three different clinical centers. Whereas paternal transmission shows equilibrium, we observed maternal transmission disequilibrium of GRIK2 in the largest population (p=0.03), which was still significant when all populations were added (p=0.05). These results are similar to the maternal GRIK2 transmission disequilibrium previously reported for autism, and support the presence of a susceptibility gene for schizophrenia at 6q16.

    Neuroreport 2004;15;12;1987-91

  • Frequency and transmission of glutamate receptors GRIK2 and GRIK3 polymorphisms in patients with obsessive compulsive disorder.

    Delorme R, Krebs MO, Chabane N, Roy I, Millet B, Mouren-Simeoni MC, Maier W, Bourgeron T and Leboyer M

    INSERM U 513, Faculté de Médecine, 8 rue du Général Sarrail, 94010 Créteil, France. delorme@im3.inserm.fr

    Several lines of evidence suggest that obsessive compulsive disorder (OCD) could be the consequence of glutamatergic dysfunction. We performed a case-control study in 156 patients and 141 controls and the transmission disequilibrium test in 124 parent-offspring trios to search for association between OCD and two kainate receptors, GRIK2 and GRIK3. Using three single nucleotide polymorphisms (SNP) in GRIK2 and one in GRIK3, we found no evidence for association in case-control or family-based analyses. Only the GRIK2 SNP I867, recently associated with autism, was less transmitted than expected (p < 0.03), supporting a functional role for this variant. These findings suggest the need for further investigation of the role of GRIK2 in OCD.

    Neuroreport 2004;15;4;699-702

  • Channel-opening kinetics of GluR6 kainate receptor.

    Li G, Oswald RE and Niu L

    Department of Chemistry, Center for Neuroscience Research, University at Albany, State University of New York, Albany, New York 12222, USA.

    GluR6 is an ionotropic glutamate receptor subunit of the kainate subtype. It plays an essential role in synaptic plasticity and epilepsy. We expressed this recombinant receptor in HEK-293 cells and characterized the glutamate-induced channel-opening reaction, using a laser-pulse photolysis technique with the caged glutamate (gamma-O-(alpha-carboxy-2-nitrobenzyl)glutamate). This technique permits glutamate to be liberated photolytically from the caged glutamate with a time constant of approximately 30 micros. Prior to laser photolysis, the caged glutamate did not activate the GluR6 channel, nor did it inhibit or potentiate the glutamate response. At the transmembrane voltage of -60 mV, pH 7.4 and 22 degrees C, the channel-opening and -closing rate constants were determined to be (1.1 +/- 0. 4) x 10(4) and (4.2 +/- 0.2) x 10(2) s(-1), respectively. The intrinsic dissociation constant of glutamate and the channel-opening probability were found to be 450 +/- 200 microM and 0.96, respectively. These constants are derived from a minimal kinetic mechanism of the channel activation involving the binding of two glutamate molecules. This mechanism describes the time course of the open-channel form of the receptor as a function of glutamate concentration. On the basis of the channel-opening rate constants obtained, the shortest rise time (20-80% of the receptor current response) or the fastest time by which the GluR6Q channel can open is predicted to be 120 micros. The open-channel form of the receptor determines the transmembrane voltage change, which in turn controls synaptic signal transmission between two neurons. The comparison of the channel-opening kinetic rate constants between GluR6Q and GluR2Q(flip), reported in the companion paper, suggests that at a glutamate concentration of 100 microM, for instance, the integrated neuronal signal will be dominated by a slower GluR6Q receptor response, as compared to the GluR2Q(flip) component.

    Biochemistry 2003;42;42;12367-75

  • Distribution of kainate receptor subunits at hippocampal mossy fiber synapses.

    Darstein M, Petralia RS, Swanson GT, Wenthold RJ and Heinemann SF

    Molecular Neurobiology, The Salk Institute for Biological Studies, La Jolla, California 92037, USA. melanie.darstein@anat.uni-freiburg.de

    Kainate receptors function as mediators of postsynaptic currents and as presynaptic modulators of synaptic transmission at mossy fiber synapses. Despite intense research into the physiological properties of mossy fiber kainate receptors, their subunit composition in the presynaptic and postsynaptic compartments is unclear. Here we describe the distribution of kainate receptor subunits in mossy fiber synapses using subunit-selective antibodies and knock-out mice. We provide morphological evidence for the presynaptic localization of KA1 and KA2 receptor subunits at mossy fiber synapses. Immunogold staining for KA1 and KA2 was commonly seen at synaptic contacts and in vesicular structures. Postsynaptic labeling in dendritic spines was also observed. Although KA1 predominantly showed presynaptic localization, KA2 was concentrated to a greater degree on postsynaptic membranes. Both subunits coimmunoprecipitated from hippocampal membrane extracts with GluR6 but not GluR7 subunits. These results demonstrate that KA1 and KA2 subunits are localized presynaptically and postsynaptically at mossy fiber synapses where they most likely coassemble with GluR6 subunits to form functional heteromeric kainate receptor complexes.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2003;23;22;8013-9

  • Modulation of age at onset in Huntington's disease and spinocerebellar ataxia type 2 patients originated from eastern India.

    Chattopadhyay B, Ghosh S, Gangopadhyay PK, Das SK, Roy T, Sinha KK, Jha DK, Mukherjee SC, Chakraborty A, Singhal BS, Bhattacharya AK and Bhattacharyya NP

    Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata 700 064, India.

    To identify the genetic modifier(s) that might alter the age at onset in Huntington's disease (HD) we have analyzed variations in GluR6 kainate receptor (GluR6), CA150 gene, Delta2642 and polymorphic CCG repeat variation in huntingtin (htt) gene in 77 HD patients and normal individuals. In addition, variation in the RAI1 gene was analyzed in 30 spinocerebellar ataxia (SCA2) patients and normal individuals to show the possible influence on the age at onset. Multiple regression analysis indicated that variation in GluR6 and CCG repeat genotype might explain 6.2% and 3.1%, respectively, of the variability in the age at onset in HD. Similar analysis with SCA2 patients indicated that RAI1 might explain about 13% of the variability in the age at onset. Specific alleles in GluR6 and CA150 locus were only observed in HD patients.

    Neuroscience letters 2003;345;2;93-6

  • Rapid and differential regulation of AMPA and kainate receptors at hippocampal mossy fibre synapses by PICK1 and GRIP.

    Hirbec H, Francis JC, Lauri SE, Braithwaite SP, Coussen F, Mulle C, Dev KK, Coutinho V, Meyer G, Isaac JT, Collingridge GL, Henley JM and Couthino V

    MRC Centre for Synaptic Plasticity, Department of Anatomy, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, United Kingdom.

    We identified four PDZ domain-containing proteins, syntenin, PICK1, GRIP, and PSD95, as interactors with the kainate receptor (KAR) subunits GluR5(2b,) GluR5(2c), and GluR6. Of these, we show that both GRIP and PICK1 interactions are required to maintain KAR-mediated synaptic function at mossy fiber-CA3 synapses. In addition, PKC alpha can phosphorylate ct-GluR5(2b) at residues S880 and S886, and PKC activity is required to maintain KAR-mediated synaptic responses. We propose that PICK1 targets PKC alpha to phosphorylate KARs, causing their stabilization at the synapse by an interaction with GRIP. Importantly, this mechanism is not involved in the constitutive recycling of AMPA receptors since blockade of PDZ interactions can simultaneously increase AMPAR- and decrease KAR-mediated synaptic transmission at the same population of synapses.

    Funded by: Medical Research Council: G9629038; Wellcome Trust: 059917

    Neuron 2003;37;4;625-38

  • Heteromer formation of delta2 glutamate receptors with AMPA or kainate receptors.

    Kohda K, Kamiya Y, Matsuda S, Kato K, Umemori H and Yuzaki M

    Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 332 North Lauderdale, Memphis, TN 38105, USA.

    The delta2 glutamate receptor (GluRdelta2) is predominantly expressed in the postsynaptic densities of parallel fiber-Purkinje cell synapses and plays a crucial role in cerebellar function. However, the mechanisms by which GluRdelta2 participates in cerebellar functions are largely unknown because GluRdelta2 does not bind glutamate analogs. We investigated the possibility that GluRdelta2 may be involved in channel formation together with other glutamate receptor families. We transiently expressed lurcher mutant AMPA receptor GluR1(Lc) and kainate receptor GluR6(Lc) in HEK293 cells. Cells expressing these constitutively active channels displayed a rectifying current-voltage (I-V) relationship. However, when cells were co-transfected with GluRdelta2(Lc), which had the arginine residue in the channel pore region, cells displayed a linear I-V relationship, a result that indicates GluRdelta2(Lc) formed functional heteromeric channels with GluR1(Lc) or GluR6(Lc). Assembly of GluRdelta2 with GluR1 or GluR6 was further confirmed by co-immunoprecipitation assays in HEK293 cells. In addition, GluRdelta2 receptors were partially co-immunoprecipitated from cerebellar synaptosomal fractions by antibodies against GluR2 or KA2. In contrast to lurcher channels, expression of wild-type GluRdelta2 significantly reduced the glutamate-induced current of the wild-type GluR1 receptors without affecting channel properties, such as current kinetics, dose-response relationship, and single-channel conductance. Thus, the heteromeric channel created by the association of wild-type GluR1 and GluRdelta2 may not be gated by glutamate and does not participate in glutamate-induced currents. These results suggest that GluRdelta2 and AMPA or kainate receptors can assemble to form heteromeric receptors in vitro and could modify glutamate signaling in vivo. These findings may help explain the role of GluRdelta2.

    Funded by: NCI NIH HHS: CA 21765; NINDS NIH HHS: NS 36925

    Brain research. Molecular brain research 2003;110;1;27-37

  • Selective binding of synapse-associated protein 97 to GluR-A alpha-amino-5-hydroxy-3-methyl-4-isoxazole propionate receptor subunit is determined by a novel sequence motif.

    Cai C, Coleman SK, Niemi K and Keinänen K

    Department of Biosciences, Division of Biochemistry, University of Helsinki, Helsinki FIN-00014, Finland.

    A family of four closely related PDZ domain-containing membrane-associated guanylate kinase homologues (MAGUKs) is involved in the regulation of the amount and functional state of ionotropic glutamate receptors in excitatory synapses. To understand the mechanisms that determine the specificity of these interactions, we examined the structural basis of the highly selective association between the ionotropic GluR subunit GluR-A and synapse-associated protein 97 (SAP97). The C terminus of GluR-A bound to the PDZ domains of SAP97, but not to those of three related MAGUKs, PSD-93, PSD-95, and SAP102. Experiments with single PDZ domains indicated that the strongest contribution was by the second PDZ domain. Unexpectedly, mutation analysis of the GluR-A C terminus revealed that a tripeptide sequence SSG at position -9 to -11 plays an essential role in this binding, in addition to a C-terminal type I PDZ binding motif (leucine at C terminus and threonine at the -2 position). Analysis of the in vitro MAGUK-binding properties of a GluR-D mutant with a one-residue deletion at the C terminus provides further support for the view that an SSG sequence located N-terminally from a type I PDZ binding motif can mediate selective binding to SAP97 and suggest the existence of a novel variation of the PDZ domain-peptide interaction.

    The Journal of biological chemistry 2002;277;35;31484-90

  • Recruitment of the kainate receptor subunit glutamate receptor 6 by cadherin/catenin complexes.

    Coussen F, Normand E, Marchal C, Costet P, Choquet D, Lambert M, Mège RM and Mulle C

    Centre National de la Recherche Scientifique Unité Mixte de Recherche 5091, Institut François Magendie, Paris 75005, France.

    Kainate receptors modulate synaptic transmission by acting either at presynaptic or at postsynaptic sites. The precise localization of kainate receptors as well as the mechanisms of targeting and stabilization of these receptors in neurons are largely unknown. We have generated transgenic mice expressing the kainate receptor subunit glutamate receptor 6 (GluR6) bearing an extracellular myc epitope (myc-GluR6), in forebrain neurons, in which it assembles with endogenous kainate receptor subunits. In transgenic mice crossed with GluR6-deficient mice, myc-GluR6 efficiently rescues the missing subunit. Immunoprecipitation of transgenic brain extracts with anti-myc antibodies demonstrates an interaction with cadherins, beta-catenin, and p120 catenin, as well as with the associated proteins calcium calmodulin-dependent serine kinase and Velis, but not with alpha-catenin. In glutathione S-transferase-pulldown experiments, beta-catenin interacts, although indirectly, with the last 14 aa of GluR6. Transfected myc-GluR6 colocalizes with beta-catenin at cell-cell junctions in non-neuronal cells. Finally, activation of N-cadherins by ligand-covered latex beads recruits GluR6 to cadherin/catenin complexes. These results suggest an important role for cadherin/catenin complexes in the stabilization of kainate receptors at the synaptic membrane during synapse formation and remodeling.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2002;22;15;6426-36

  • The PDZ proteins PICK1, GRIP, and syntenin bind multiple glutamate receptor subtypes. Analysis of PDZ binding motifs.

    Hirbec H, Perestenko O, Nishimune A, Meyer G, Nakanishi S, Henley JM and Dev KK

    Department of Anatomy, Medical Research Council Centre of Synaptic Plasticity, Medical School, University of Bristol, Bristol BS8 1TD, United Kingdom.

    Using sequence homology searches, yeast two-hybrid assays and glutathione S-transferase (GST)-pull-down approaches we have identified a series of glutamate receptor subunits that interact differentially with the PDZ proteins GRIP, PICK1, and syntenin. GST-pull-down experiments identified more interactions than detected by yeast two-hybrid assays. We report several receptor-protein interactions, strong ones include: (i) GRIP and syntenin with mGluR7a, mGluR4a, and mGluR6; (ii) PICK1 and GRIP with mGluR3; and (iii) syntenin with all forms of GluR1-4 and mGluR7b. We further characterized the novel mGluR7a-GRIP interaction found both in yeast two-hybrid and GST-pull-down assays and observed that mGluR7a localization overlapped with GRIP with in hippocampal neurons. The wide range of targets for PICK1, GRIP, and syntenin suggests they may represent a molecular mechanism that can concentrate and/or regulate a number of different receptors at a common site on a synapse. These data also suggest that the structural determinants involved in PDZ interactions are more complex than originally envisaged.

    Funded by: Medical Research Council: G9629038

    The Journal of biological chemistry 2002;277;18;15221-4

  • The PDZ1 domain of SAP90. Characterization of structure and binding.

    Piserchio A, Pellegrini M, Mehta S, Blackman SM, Garcia EP, Marshall J and Mierke DF

    Department of Chemistry, Division of Biology and Medicine, Brown University, Providence, RI 02912, USA.

    The structural features of the PDZ1 domain of the synapse-associated protein SAP90 have been characterized by NMR. A comparison with the structures of the PDZ2 and PDZ3 domains of SAP90 illustrates significant differences, which may account for the unique binding properties of these homologous domains. Within the postsynaptic density, SAP90 functions as a molecular scaffold with a number of the protein-protein interactions mediated through the PDZ1 domain. Here, using fluorescence anisotropy and NMR chemical shift analysis, we have characterized the association of PDZ1 to the C-terminal peptides of the GluR6 subunit of the kainate receptor, voltage-gated K(+) channel Kv1.4, and microtubule-associate protein CRIPT, all of which are known to associate with SAP90. The latter two, which possess the consensus sequence for binding to PDZ domains (T/S-X-V-oh), have low micromolar binding affinities (1.5-15 microm). The C terminus of GluR6, RLPGKETMA-oh, lacking the consensus sequence, binds to PDZ1 of SAP90 with an affinity of 160 microm. The NMR data illustrate that although all three peptides occupy the binding groove capped by the GLGF loop of PDZ1, specific differences are present, consistent with the variation in binding affinities.

    The Journal of biological chemistry 2002;277;9;6967-73

  • Linkage and association of the glutamate receptor 6 gene with autism.

    Jamain S, Betancur C, Quach H, Philippe A, Fellous M, Giros B, Gillberg C, Leboyer M, Bourgeron T and Paris Autism Research International Sibpair (PARIS) Study

    Laboratoire d'Immunogénétique Humaine, INSERM E021, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris cedex 15, France.

    A genome scan was previously performed and pointed to chromosome 6q21 as a candidate region for autism. This region contains the glutamate receptor 6 (GluR6 or GRIK2) gene, a functional candidate for the syndrome. Glutamate is the principal excitatory neurotransmitter in the brain and is directly involved in cognitive functions such as memory and learning. We used two different approaches, the affected sib-pair (ASP) method and the transmission disequilibrium test (TDT), to investigate the linkage and association between GluR6 and autism. The ASP method, conducted with additional markers on the 51 original families and in eight new sibling pairs, showed a significant excess of allele sharing, generating an elevated multipoint maximum LOD score (ASPEX MLS = 3.28). TDT analysis, performed in the ASP families and in an independent data set of 107 parent-offspring trios, indicated a significant maternal transmission disequilibrium (TDTall P = 0.0004). Furthermore, TDT analysis (with only one affected proband per family) showed significant association between GluR6 and autism (TDT association P = 0.008). In contrast to maternal transmission, paternal transmission of GluR6 alleles was as expected in the absence of linkage, suggesting a maternal effect such as imprinting. Mutation screening was performed in 33 affected individuals, revealing several nucleotide polymorphisms (SNPs), including one amino acid change (M867I) in a highly conserved domain of the intracytoplasmic C-terminal region of the protein. This change is found in 8% of the autistic subjects and in 4% of the control population and seems to be more maternally transmitted than expected to autistic males (P = 0.007). Taken together, these data suggest that GluR6 is in linkage disequilibrium with autism.

    Molecular psychiatry 2002;7;3;302-10

  • Genomic organization of the human GRIK2 gene and evidence for multiple splicing variants.

    Barbon A, Vallini I and Barlati S

    Division of Biology and Genetics, Department of Biomedical Sciences and Biotechnologies, Brescia University Medical School, via Valsabbina 19, 25123 Brescia, Italy.

    Fast excitatory transmission in the vertebrate central nervous system is mediated mainly by L-glutamate. Here we present the genomic organization of the human GRIK2 gene, which codes for the kainate GluR6 receptor subunit, deduced from sequence data present in the public databases and analyzed by bioinformatic tools. By similarity search using the human GluR6 cDNA sequence against non-redundant databases, we found three positive entries (AP002528, AP002529, and AP002530 deposited by Hirakawa et al., 2000) which are part of a BAC contig of about 1 Mb spanning region 6q21. The GRIK2 gene was found to be split into 17 exons, covering about 670 kb of the region. The availability of the data on the genomic organization allowed the study of GRIK2 gene expression by RT-PCR analysis which was performed on human teratocarcinoma cell cultures (NT2) and on mRNA obtained from human hippocampus (Clontech). The study gives evidence for several different splicing variants in addition to the previously cloned human GluR6 cDNA (ID: U16126). The splicing mechanism leading to the different isoforms involves exons 11, 12 and 16. The mRNA containing exon 16 at the 3' end is the homolog to the mouse GluR6-2. The translation of this mRNA would code for a different intracellular C-terminus, as compared to that coded by the known human isoform. The newly identify isoform is the predominant form expressed in human teratocarcinoma NT2 cells. All the newly identified mRNAs isoforms are expressed in NT2 cells and in human hippocampus mRNA at variable levels and would be responsible for the production of five different putative GluR6 receptor subunits, some differing in the C-terminal domains (mouse homolog) and some lacking specific transmembrane domains.

    Gene 2001;274;1-2;187-97

  • Molecular mechanisms regulating the differential association of kainate receptor subunits with SAP90/PSD-95 and SAP97.

    Mehta S, Wu H, Garner CC and Marshall J

    Department Of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, Rhode Island 02912, USA.

    Recent studies have demonstrated that kainate receptors are associated with members of the SAP90/PSD-95 family (synapse-associated proteins (SAPs)) in neurons and that SAP90 can cluster and modify the electrophysiological properties of GluR6/KA2 kainate receptors when co-expressed in transfected cells. In vivo, SAP90 tightly binds kainate receptor subunits, while SAP97 is only weakly associated, suggesting that this glutamate receptor differentially associates with SAP90/PSD-95 family members. Here, green fluorescent protein (GFP)-tagged chimeras and deletion mutants of SAP97 and SAP90 were employed to define the molecular mechanism underlying their differential association with kainate receptors. Our results show that a weak interaction between GluR6 and the PDZ1 domain of SAP97 can account for the weak association of GluR6 with the full-length SAP97 observed in vivo. Expression studies in HEK293 cells and in vitro binding studies further show that although the individual Src homology 3 and guanylate kinase domains in SAP97 can interact with the C-terminal tail of KA2 subunit, specific intramolecular interactions in SAP97 (e.g. the SAP97 N terminus (S97N) binding to the Src homology 3 domain) interfere with KA2 binding to the full-length molecule. Because receptor subunits are known to segregate to different parts of the neuron, our results imply that differential association of kainate receptors with SAP family proteins may be one mechanism of subcellular localization.

    Funded by: NIA NIH HHS: AG 06569-09, AG 12978-02, AG12978-02; NICHD NIH HHS: P50 HD32901

    The Journal of biological chemistry 2001;276;19;16092-9

  • The introduction of MR in the Nordic countries with special reference to Norway: central control versus local initiatives.

    Smith HJ

    Department of Radiology, The National Hospital, University of Oslo, Oslo, Norway. h.j.smith@rh.uio.no

    The introduction of MR technology in Norway differed from that in Denmark, Finland and Sweden. In the latter countries, decisions were made at county or local level while in Norway the process was steered by the government and the national health authorities. For several reasons the steering was not very successful, and the intention of buying one MR unit ended with the purchase of five units. As a counter-reaction, for seven years only university hospitals were allowed to purchase MR equipment. In 1993, the strict regulations were abolished, and during the succeeding years all four Nordic countries experienced similar exponential growth in the number of MR units.

    Journal of magnetic resonance imaging : JMRI 2001;13;4;639-44

  • Subtype-specific assembly of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor subunits is mediated by their n-terminal domains.

    Leuschner WD and Hoch W

    Max-Planck-Institut für Entwicklungsbiologie, Abteilung Biochemie, Spemannstrasse 35, D-72076 Tübingen, Germany.

    Glutamate receptors (GluR) are oligomeric protein complexes formed by the assembly of four or perhaps five subunits. The rules that govern the selectivity of this process are not well understood. Here, we expressed combinations of subunits from two related GluR subfamilies in COS7 cells, the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and kainate receptors. By co-immunoprecipitation experiments, we assessed the ability of AMPA receptor subunits to assemble into multimeric complexes. Subunits GluR1-4 associated with indistinguishable efficiency with each other, whereas the kainate receptor subunits GluR6 and 7 showed a much lower degree of association with GluR1. Using chimeric receptors and truncation fragments of subunits, we show that this assembly specificity is determined by N-terminal regions of these subunits and that the most N-terminal domain of GluR2 together with a membrane anchor efficiently associates with GluR1.

    The Journal of biological chemistry 1999;274;24;16907-16

  • SAP90 binds and clusters kainate receptors causing incomplete desensitization.

    Garcia EP, Mehta S, Blair LA, Wells DG, Shang J, Fukushima T, Fallon JR, Garner CC and Marshall J

    Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, Rhode Island 02912, USA.

    The mechanism of kainate receptor targeting and clustering is still unresolved. Here, we demonstrate that members of the SAP90/PSD-95 family colocalize and associate with kainate receptors. SAP90 and SAP102 coimmunoprecipitate with both KA2 and GluR6, but only SAP97 coimmunoprecipitates with GluR6. Similar to NMDA receptors, GluR6 clustering is mediated by the interaction of its C-terminal amino acid sequence, ETMA, with the PDZ1 domain of SAP90. In contrast, the KA2 C-terminal region binds to, and is clustered by, the SH3 and GK domains of SAP90. Finally, we show that SAP90 coexpressed with GluR6 or GluR6/KA2 receptors alters receptor function by reducing desensitization. These studies suggest that the organization and electrophysiological properties of synaptic kainate receptors are modified by association with members of the SAP90/PSD-95 family.

    Funded by: NICHD NIH HHS: R01 HD023924, R01 HD052083; NINDS NIH HHS: R29 NS 33914-02

    Neuron 1998;21;4;727-39

  • RNA editing of brain glutamate receptor channels: mechanism and physiology.

    Seeburg PH, Higuchi M and Sprengel R

    Max-Planck Institute for Medical Research, Department of Molecular Neuroscience, Jahnstr. 29, 69120 Heidelberg, Germany. seeburg@mpimp-heidelberg.mpg.de

    Glutamate-gated cation selective channels mediate fast excitatory neurotransmission in the mammalian brain. Functionally critical channel positions contain amino acid residues not predicted from the exonic sequence for the channel subunits. The codons for these residues are created in the respective primary gene transcripts by the site selective deamination of adenosine to inosine. This type of RNA editing requires a short double-stranded RNA structure formed by the exonic sequence around the adenosine targeted for deamination with a complementary sequence in the downstream intron and hence, it precedes splicing. Candidate enzymes for nuclear transcript editing currently comprise three molecularly cloned mammalian RNA-dependent adenosine deaminases. Two of these are expressed in most body tissues, perhaps indicating that adenosine deamination in transcripts is more global than has been recognized. Indeed, numerous mRNAs in different tissues may contain inosine residues and encode proteins with amino acid substitutions and different properties relative to the exonically encoded forms. If so, RNA editing by adenosine deamination may significantly enlarge the functional repertoire of the mammalian genome.

    Brain research. Brain research reviews 1998;26;2-3;217-29

  • Expression and heteromeric interactions of non-N-methyl-D-aspartate glutamate receptor subunits in the developing and adult cerebellum.

    Ripellino JA, Neve RL and Howe JR

    Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520-8066, USA.

    The localization and expression of ionotropic non-N-methyl-D-aspartate glutamate receptors (GluR) were investigated in the developing and adult rat cerebellum using subunit-specific polyclonal antibodies for immunocytochemical, immunoblot and immunoprecipitation studies. In P7 animals, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor immunoreactivity was detected in all layers of the cerebellar cortex with the exception of the external granule cell layer. Antibodies against the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor subunits GluR1 and GluR4 gave strong immunoreactive staining of Bergmann glia in both young and adult animals, and both antibodies showed prominent staining of the molecular layer in the adult cerebellum. Dense immunoreactive staining of Purkinje cell somata and dendrites was obtained with anti-GluR2/3/4c in both the developing and adult cerebellum. Whereas each of the three alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor antibodies stained the internal, but not the external, granule cell layer, immunostaining for the kainate-type subunits GluR6/7 and KA2 was detected in both the external and internal granule cell layers. as well as in the molecular layer in both P7 and adult cerebellum. Immunoblot analysis of total cerebellar protein indicated that the level of GluR4 expression increased 15-fold from P1 to P18, whereas the expression of the KA2 subunit protein was nine-fold lower in adult cerebellum than it was at P1. The expression of GluR1 increased moderately (two-fold) from P1 to adult. Subunit interactions between GluR1 and GluR4, as well as between GluR6/7 and KA2, were demonstrated in immunoprecipitation experiments; and the GluR4 and KA2 subunits appear to be present exclusively in heteromeric assemblies with GluR1 and GluR6/7, respectively. The results show that the various alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate- and kainate-type subunits are differentially expressed during cerebellar development and further define the possible subunit composition of non-N-methyl-D-aspartate receptors in the major cerebellar cell types.

    Funded by: NICHD NIH HHS: HD24236; NINDS NIH HHS: NS12327, NS30996

    Neuroscience 1998;82;2;485-97

  • Genotypes at the GluR6 kainate receptor locus are associated with variation in the age of onset of Huntington disease.

    Rubinsztein DC, Leggo J, Chiano M, Dodge A, Norbury G, Rosser E and Craufurd D

    East Anglian Medical Genetics Service Molecular Genetics Laboratory, Addenbrooke's NHS Trust, Cambridge, United Kingdom.

    Huntington disease (HD) is associated with abnormal expansions of a CAG repeat close to the 5' end of the IT15 gene. We have assembled a set of 293 HD subjects whose ages of onset were known and sized their HD CAG repeats. These repeats accounted for 69% of the variance of age of onset when we used the most parsimonious model, which relates the logarithm of age of onset to a function of CAG repeat number. Since other familial factors have been proposed to influence the age of onset of HD, we have examined a number of candidate loci. The CAG repeat number on normal chromosomes, the delta2642 polymorphism in the HD gene, and apolipoprotein E genotypes did not affect the age of onset of HD. Although mitochondrial energy production defects in HD have led to suggestions that variants in the mitochondrial genome may be associated with clinical variability in HD, this suggestion was not supported by our preliminary experiments that examined the DdeI mitochondrial restriction fragment length polymorphism at position 10,394. Excitotoxicity has been a favored mechanism to explain the cell death in HD, particularly since intrastriatal injection of excitatory amino acids in animals creates HD-like pathology. Accordingly, we investigated the GluR6 kainate receptor. Of the variance in the age of onset of HD that was not accounted for by the CAG repeats, 13% could be attributed to GluR6 genotype variation. These data implicate GluR6-mediated excitotoxicity in the pathogenesis of HD and highlight the potential importance of this process in other polyglutamine repeat expansion diseases.

    Proceedings of the National Academy of Sciences of the United States of America 1997;94;8;3872-6

  • Distribution of kainate receptor subunit mRNAs in human hippocampus, neocortex and cerebellum, and bilateral reduction of hippocampal GluR6 and KA2 transcripts in schizophrenia.

    Porter RH, Eastwood SL and Harrison PJ

    University Department of Psychiatry, Warneford Hospital, Oxford, UK.

    The mRNAs encoding kainic acid (KA) preferring glutamate receptor subunits (GluR5-7, KA1 and KA2) are differentially expressed in rat brain. We have used regional and cellular in situ hybridization histochemistry with subunit-specific 35S-labelled oligodeoxyribonucleotides to examine these mRNAs in adult human hippocampus, neocortex and cerebellum. GluR5 mRNA was detected only in Purkinje cells and a few scattered hippocampal neurons. GluR6 mRNA was relatively abundant in all areas, notably in dentate gyrus, pyramidal neurons of CA3, and cerebellar granule cells, as well as being present in superficial and deep laminae of the neocortex. Moderate signal for GluR7 mRNA was seen in deep laminae of the neocortex with a weak signal in the dentate gyrus; in dipped sections GluR7 mRNA was also apparent over some pyramidal and non-pyramidal cells in hippocampus and over putative cerebellar stellate/basket cells. KA1 mRNA was detected in the dentate gyrus but not reliably elsewhere. The expression profile and abundance of KA2 mRNA was similar to that of GluR6 mRNA. For all five transcripts, concurrent hybridization of rat brain sections produced the anticipated distribution of signal. The data indicate that the regional and cellular distribution of KA receptor subunit mRNAs in human hippocampus, neocortex and cerebellum largely parallels that in the corresponding areas of rat brain, albeit at lower levels, especially with regard to GluR5 and KA1 transcripts. In schizophrenia there is a partial loss of hippocampal non-NMDA receptors, but there are no data concerning KA receptor subunit expression. KA2 and GluR6 mRNAs were sufficiently abundant for a comparison in the left and right hippocampus between 11 schizophrenics and 13 controls. Using film autoradiography, both mRNAs were significantly reduced in the schizophrenics, having controlled for the effects of brain pH, post mortem interval and age. GluR6 mRNA was also quantitated in cerebellum, wherein no differences were found between cases and controls. In conjunction with earlier findings of reduced hippocampal GluR1 and GluR2 expression and a loss of [3H]KA binding sites, these data show that schizophrenia is associated with impaired expression of both AMPA- and KA-preferring ionotropic glutamate receptors. These deficits are likely to contribute to the glutamatergic component of the disease pathophysiology.

    Funded by: Wellcome Trust

    Brain research 1997;751;2;217-31

  • Palmitoylation of the GluR6 kainate receptor.

    Pickering DS, Taverna FA, Salter MW and Hampson DR

    Medical Research Council Group on Nerve Cells and Synapses, University of Toronto, ON, Canada.

    The G-protein-coupled metabotropic glutamate receptor mGluR1 alpha and the ionotropic glutamate receptor GluR6 were examined for posttranslational palmitoylation. Recombinant receptors were expressed in baculovirus-infected insect cells or in human embryonic kidney cells and were metabolically labeled with [3H]palmitic acid. The metabotropic mGluR1 alpha receptor was not labeled whereas the GluR6 kainate receptor was labeled after incubation with [3H]palmitate. The [3H]palmitate labeling of GluR6 was eliminated by treatment with hydroxylamine, indicating that the labeling was due to palmitoylation at a cysteine residue via a thioester bond. Site-directed mutagenesis was used to demonstrate that palmitoylation of GluR6 occurs at two cysteine residues, C827 and C840, located in the carboxyl-terminal domain of the molecule. A comparison of the electrophysiological properties of the wild-type and unpalmitoylated mutant receptor (C827A, C840A) showed that the kainate-gated currents produced by the unpalmitoylated mutant receptor were indistinguishable from those of the wild-type GluR6. The unpalmitoylated mutant was a better substrate for protein kinase C than the wild-type GluR6 receptor. These data indicate that palmitoylation may not modulate kainate channel function directly but instead affect function indirectly by regulating the phosphorylation state of the receptor.

    Proceedings of the National Academy of Sciences of the United States of America 1995;92;26;12090-4

  • Refinement of map position of the human GluR6 kainate receptor gene (GRIK2) and lack of association and linkage with idiopathic generalized epilepsies.

    Sander T, Janz D, Ramel C, Ross CA, Paschen W, Hildmann T, Wienker TF, Bianchi A, Bauer G, Sailer U et al.

    Department of Psychiatry, University Hospital Rudolf Virchow, Berlin, Germany.

    Hereditary factors play a major role in the etiology of idiopathic generalized epilepsies (IGEs). The pivotal function of glutamate receptors (GluRs) in excitatory neurotransmission implicates their involvement in epileptogenesis and genetic susceptibility to IGEs. A trinucleotide repeat polymorphism detected in the 3' untranslated region of the kainate-selective GluR6 receptor gene (GRIK2) on chromosome 6 makes it possible to perform linkage and association studies with this high-ranking candidate gene. The present study tested the hypothesis that allelic variants of GRIK2 contribute to the genetic susceptibility to the common IGEs. Linkage and association analyses were conducted in 63 families ascertained through IGE patients with juvenile myoclonic epilepsy, juvenile absence epilepsy, or childhood absence epilepsy. Our linkage and association results suggest that allelic variants of GRIK2 are not involved in the expression of the common familial IGEs, and radiation hybrid mapping assigns GRIK2 to the chromosomal region 6q16.3-q21. This localization excludes GRIK2 as a candidate for the putative IGE susceptibility locus "EJM1" on the short arm of chromosome 6.

    Funded by: NIMH NIH HHS: MH50763

    Neurology 1995;45;9;1713-20

  • RNA editing of human kainate receptor subunits.

    Nutt SL and Kamboj RK

    Allelix Biopharmaceuticals Inc., Mississauga, Ontario, Canada.

    RNA editing has been shown to be critical in generating the molecular diversity of rodent kainate receptors. We have examined cDNAs derived from various human brain sources to assess the occurrence and extent of RNA editing in human brain. Comparison of genomic and cDNA sequences revealed extensive editing of the human EAA4 (GluR6) mRNA at the isoleucine/valine, tyrosine/cysteine sites of the transmembrane I region, and the glutamine/arginine site of the transmembrane II region. Of the eight potential molecular variants generated by the nucleotide exchange, five were observed in the tissues examined. The distribution of the various RNA editing combinations were not uniform, and displayed tissue and/or age dependent distribution. Editing of the glutamine/arginine site was also confirmed for EAA3 (GluR5), which displays a significantly higher extent of editing in specific human brain regions compared with rodent whole brain. Hence, it can be concluded that RNA editing is a determinant of the phenotype of human kainate receptor complexes.

    Neuroreport 1994;5;18;2625-9

  • RNA editing of the glutamate receptor subunits GluR2 and GluR6 in human brain tissue.

    Paschen W, Hedreen JC and Ross CA

    Department of Psychiatry and Neuroscience, Johns Hopkins University, School of Medicine, Baltimore.

    Editing of mRNA in the coding region of the second transmembrane domain of glutamate receptor subunits GluR2, GluR5, and GluR6 involves a change of the base A in genomic DNA to the base G in mRNA as described in rat brain. To determine whether this reaction occurs in humans as well as rats, we studied RNA editing of GluR2 and GluR6 in human brain. We compared the extent of editing in controls and cases with Huntington's disease. To assay the extent of editing in brain RNA, first strand cDNA was amplified using the polymerase chain reaction yielding a product across the region of the second transmembrane spanning segment in which editing takes place in rats. The PCR product was incubated with the restriction enzyme BbvI, which recognizes the sequence GCAGC present in the nonedited sequence of the mRNA in subunits GluR2 and GluR6. Thus, BbvI cuts the nonedited version but leaves the edited version intact. As in the rat, the GluR2 subunit mRNA was completely edited in human brain. The GluR6 subunit was nearly completely edited in all gray matter structures investigated including cortex, striatum, thalamus, hippocampus, amygdala, and cerebellum with extent of editing ranging from 89% in the cerebellum to 95% in the cortex and striatum. No significant differences in the extent of RNA editing were apparent in control versus Huntington's disease brains. To compare the extent of editing in neurons and glia in the brain, editing in cerebral cortex (predominantly gray matter and thus neurons) was compared with editing in corpus callosum (white matter and thus nearly completely glial cells).(ABSTRACT TRUNCATED AT 250 WORDS)

    Funded by: NINDS NIH HHS: NS 16376

    Journal of neurochemistry 1994;63;5;1596-602

  • A transmembrane model for an ionotropic glutamate receptor predicted on the basis of the location of asparagine-linked oligosaccharides.

    Taverna FA, Wang LY, MacDonald JF and Hampson DR

    Medical Research Council Group on Nerve Cells and Synapses, University of Toronto, Ontario, Canada.

    Several different models have been proposed for the transmembrane structure of receptors for the neurotransmitter L-glutamate. In this study, the sites of N-linked oligosaccharides on GluR6, a member of the kainate class of ionotropic glutamate receptors, were examined. Site-directed mutagenesis was utilized to alter the consensus sequence at three potential sites for N-linked glycosylation in the carboxyl-terminal half of the molecule. The presence of a carbohydrate substitution was monitored by shifts in the relative molecular weight of the mutant receptors on immunoblots. Molecular weight shifts were observed for the mutants N515Q and N720Q and for two companion mutants, T517A and T722A, which also eliminate the consensus sequence for N-linked glycosylation. No shift in molecular weight was observed in the the mutant N574Q. These results indicate that asparagines 515 and 720 are glycosylated and thus are likely located extracellularly. In immunocytochemical analyses of GluR6 expressed in baculovirus-infected cells, permeabilization with detergents was required for immunostaining with a carboxyl-terminal antibody, indicating that the carboxyl terminus is located intracellularly. Electrophysiological recordings of the mutant receptors expressed in human embryonic kidney cells demonstrated that the amplitudes of the kainate-activated currents mediated by the N574Q, N720Q, and the T722A mutants were not significantly different from currents mediated by wild type GluR6 receptors, while the currents mediated by the N515Q and T517A mutants were significantly depressed. Based on these findings, we propose a model for the transmembrane topology of GluR6.

    The Journal of biological chemistry 1994;269;19;14159-64

  • Transmembrane topology of the glutamate receptor subunit GluR6.

    Roche KW, Raymond LA, Blackstone C and Huganir RL

    Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.

    Ionotropic glutamate receptors mediate most rapid excitatory synaptic transmission in the mammalian central nervous system. These receptors are divided into alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), kainate, and N-methyl-D-aspartate receptors based on pharmacological and electrophysiological characteristics. Ionotropic receptor subunits are integral membrane proteins that have been proposed to have a large extracellular ligand-binding N-terminal domain, four hydrophobic transmembrane domains, and an extracellular C-terminal domain. In this study we have shown that both AMPA receptor subunits (GluR1-4) and kainate receptor subunits (GluR6/7) are glycosylated in adult rat brain; however, the kainate receptor subunits are glycosylated to a greater extent. Examination of the sequences of AMPA and kainate receptors revealed that kainate receptors have several additional consensus sites for N-linked glycosylation; interestingly, one of these is located in the proposed major intracellular loop of the receptor subunits. To test the proposed transmembrane topology model for these receptors, we have used site-specific mutagenesis of the GluR6 subunit to remove the consensus glycosylation site located within the proposed intracellular loop. Mutagenesis of this site demonstrates that it is glycosylated in transiently transfected human embryonic kidney cells, which express functional kainate receptors. Since N-linked glycosylation has only been found to occur on extracellular domains of plasma membrane proteins, these results suggest that the proposed transmembrane topology model for the glutamate receptor subunits is incorrect. Combining these results with other recent data, we have proposed an alternative transmembrane topology model.

    Funded by: NIGMS NIH HHS: GM-07309

    The Journal of biological chemistry 1994;269;16;11679-82

  • Human GluR6 kainate receptor (GRIK2): molecular cloning, expression, polymorphism, and chromosomal assignment.

    Paschen W, Blackstone CD, Huganir RL and Ross CA

    Laboratory of Molecular Neurobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.

    Glutamate receptors mediate the majority of excitatory neurotransmission in the brain, and molecular cloning studies have revealed several distinct families. Because neuropathological states and possibly human disorders may involve kainate-preferring glutamate receptors, we have isolated a cDNA clone for the human GluR6 kainate-preferring receptor. This clone shows a very high sequence similarity with that of the rat, except for a part of the 3' untranslated region in which there is a TAA triplet repeat. When the protein was overexpressed in human embryonic kidney 293 cells, it had a molecular weight, an antibody recognition, and a glutamate ligand-binding profile similar to those of the rat GluR6 receptor. Northern analysis showed expression in both human cerebral and cerebellar cortices. By PCR analysis of rodent-human monochromosomal cell lines, the human GluR6 could be assigned to chromosome 6. The length of the TAA triplet repeat was polymorphic in the normal population, with at least four alleles and an observed heterozygosity of about 45%. These studies should provide the basis for expression or linkage studies of the GluR6 kainate receptor in human disease or neuropathologic states.

    Genomics 1994;20;3;435-40

  • Biochemical and assembly properties of GluR6 and KA2, two members of the kainate receptor family, determined with subunit-specific antibodies.

    Wenthold RJ, Trumpy VA, Zhu WS and Petralia RS

    Laboratory of Neurochemistry, National Institute of Deafness and Communication Disease, National Institutes of Health, Bethesda, Maryland 20892.

    To examine subunit assembly and biochemical properties of two members of the kainate family of glutamate receptors (GluR), antibodies were made to synthetic peptides corresponding to the carboxyl termini of GluR6 and KA2. Immunoblot analysis of membranes from human embryonic kidney cells transfected with glutamate receptor cDNAs showed that these antibodies are selective for their respective receptor subunit except that the antibody to GluR6 also recognizes GluR7, which is expected due to the sequence homology between the two subunits at the carboxyl terminus. In transfected cell membranes, immunoblot analysis with the antibody to GluR6 showed a major immunoreactive band at 118 kDa and minor bands at 103 and 28 kDa. The 103-kDa band appears to be a deglycosylated form of GluR6 since deglycosylation eliminates staining at 118 kDa and increases staining of the 103-kDa band. Immunoblot analysis of KA2 transfected cell membranes shows a major band at 123 kDa and minor bands at 109 and 37 kDa. Deglycosylation converts the 123-kDa band into a 109-kDa band. Analysis of brain tissues shows that both antibodies label single major bands which migrate at the same molecular masses as those from transfected cell membranes, 118 and 123 kDa for GluR6 and KA2, respectively. Immunoprecipitation studies showed that antibodies to GluR6 and KA2 selectively immunoprecipitated [3H]kainate binding activity, but not 3H-labeled alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA) binding activity, from Triton X-100-solubilized rat brain membranes. Furthermore, each antibody coimmunoprecipitated GluR6 and KA2 from cells co-transfected with GluR6 and KA2 cDNAs and from detergent-solubilized rat brain membranes, indicating that these two subunits can coassemble into a molecular complex. Interestingly, GluR1 and GluR2, subunits of the AMPA receptor, also co-immunoprecipitated with GluR6 in cells co-transfected with GluR6 and GluR1 or GluR2 cD-NAs. Such complexes appear to be present to a limited extent in the brain.

    The Journal of biological chemistry 1994;269;2;1332-9

  • Functional expression and pharmacological characterization of the human EAA4 (GluR6) glutamate receptor: a kainate selective channel subunit.

    Hoo KH, Nutt SL, Fletcher EJ, Elliott CE, Korczak B, Deverill RM, Rampersad V, Fantaske RP and Kamboj RK

    Allelix Biopharmaceuticals Inc., Mississauga, Ontario, Canada.

    A cDNA encoding an ionotropic glutamate receptor subunit protein humEAA4 (GluR6), has been cloned from a human fetal brain library. This cDNA when expressed in COS or HEK-293 cells is associated with high-affinity kainate receptor binding and ion channel formation. We have successfully established cell lines stably expressing humEAA4 in HEK-293 cells This is the first report of the establishment of stable cell lines expressing a glutamate receptor channel. The relative potency of compounds for displacing [3H]-kainate binding to humEAA4 receptors expressed in COS or HEK-293 cells is domoate > kainate > quisqualate > 6-cyano-7-nitroquinoxaline-2,3-dione > L-glutamate = 6,7- dinitroquinoxaline-2,3-dione > dihydrokainate. Applications of kainate, glutamate, and domoate but not AMPA evoked rapidly desensitizing currents in cells expressing homo-oligomeric humEAA4 in a concentration dependent manner. The order of potency was: domoate > kainate > L-glutamate. Although AMPA did not itself activate humEAA4 receptors it did reduce, to a limited extent, kainate-evoked responses. AMPA may therefore be a weak partial agonist for this receptor. To date this effect has not been demonstrated with rat GluR6. It is possible that subtle species differences may exist in the nature of agonist receptor interaction. Kainate evoked currents were attenuated by the quinoxalinediones CNQX and DNQX but not by DAP5. The receptor desensitization was attenuated on application of concanavalin A. Ion-permeability studies indicated that the receptor-linked ion channel is permeable to both Na+ and Ca2+ ions.

    Receptors & channels 1994;2;4;327-37

  • Phosphorylation and modulation of recombinant GluR6 glutamate receptors by cAMP-dependent protein kinase.

    Raymond LA, Blackstone CD and Huganir RL

    Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.

    Glutamate-gated ion channels mediate most excitatory synaptic transmission in the central nervous system and play crucial roles in synaptic plasticity, neuronal development and some neuropathological conditions. These ionotropic glutamate receptors have been classified according to their preferred agonists as NMDA (N-methyl-D-aspartate), AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate) and KA (kainate) receptors. On the basis of sequence similarity and pharmacological properties, the recently cloned glutamate receptor subunits have been assigned as components of NMDA (NMDAR1, 2A-D), AMPA (GluR1-4) and KA (GluR5-7, KA1, KA2) receptors. Protein phosphorylation of glutamate receptors by protein kinase C and cyclic AMP-dependent protein kinase (PKA) has been suggested to regulate their function, possibly playing a prominent role in certain forms of synaptic plasticity such as long-term potentiation and long-term depression. Here we report that the GluR6 glutamate receptor, transiently expressed in mammalian cells, is directly phosphorylated by PKA, and that intracellularly applied PKA increases the amplitude of the glutamate response. Site-specific mutagenesis of the serine residue (Ser 684) representing a PKA consensus site completely eliminates PKA-mediated phosphorylation of this site as well as the potentiation of the glutamate response. These results provide evidence that direct phosphorylation of glutamate receptors modulates their function.

    Nature 1993;361;6413;637-41

Gene lists (5)

Gene List Source Species Name Description Gene count
L00000009 G2C Homo sapiens Human PSD Human orthologues of mouse PSD adapted from Collins et al (2006) 1080
L00000015 G2C Homo sapiens Human NRC Human orthologues of mouse NRC adapted from Collins et al (2006) 186
L00000016 G2C Homo sapiens Human PSP Human orthologues of mouse PSP adapted from Collins et al (2006) 1121
L00000032 G2C Homo sapiens Pocklington H1 Human orthologues of cluster 1 (mouse) from Pocklington et al (2006) 21
L00000049 G2C Homo sapiens TAP-PSD-95-CORE TAP-PSD-95 pull-down core list (ortho) 120
© G2C 2014. The Genes to Cognition Programme received funding from The Wellcome Trust and the EU FP7 Framework Programmes:
EUROSPIN (FP7-HEALTH-241498), SynSys (FP7-HEALTH-242167) and GENCODYS (FP7-HEALTH-241995).

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