G2Cdb::Gene report

Gene id
Gene symbol
Homo sapiens
gamma-aminobutyric acid (GABA) B receptor, 2
G00000067 (Mus musculus)

Databases (7)

ENSG00000136928 (Ensembl human gene)
9568 (Entrez Gene)
407 (G2Cdb plasticity & disease)
GABBR2 (GeneCards)
607340 (OMIM)
Marker Symbol
HGNC:4507 (HGNC)
Protein Sequence
O75899 (UniProt)

Synonyms (3)

  • GPRC3B
  • HG20

Literature (32)

Pubmed - other

  • Association and interaction analyses of GABBR1 and GABBR2 with nicotine dependence in European- and African-American populations.

    Li MD, Mangold JE, Seneviratne C, Chen GB, Ma JZ, Lou XY and Payne TJ

    Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, Charlottesville, Virginia, USA. Ming_Li@virginia.edu

    Previous studies have demonstrated that the gamma-aminobutyric acid type B (GABA(B)) receptor plays an essential role in modulating neurotransmitter release and regulating the activity of ion channels and adenyl cyclase. However, whether the naturally occurring polymorphisms in the two GABA(B) receptor subunit genes interact with each other to alter susceptibility to nicotine dependence (ND) remains largely unknown. In this study, we genotyped 5 and 33 single nucleotide polymorphisms (SNPs) for GABA(B) receptor subunit 1 and 2 genes (GABBR1, GABBR2), respectively, in a sample of 2037 individuals from 602 nuclear families of African- American (AA) or European-American (EA) origin. We conducted association analyses to determine (1) the association of each subunit gene with ND at both the individual SNP and haplotype levels and (2) the collective effect(s) of SNPs in both GABA(B) subunits on the development of ND. Several individual SNPs and haplotypes in GABBR2 were significantly associated with ND in both ethnic samples. Two haplotypes in AAs and one haplotype in EAs showed a protective effect against ND, whilst two other haplotypes in AAs and three haplotypes in EAs showed a risk effect for developing ND. Interestingly, these significant haplotypes were confined to two regions of GABBR2 in the AA and EA samples. Additionally, we found two minor haplotypes in GABBR1 to be positively associated with Heaviness of Smoking Index (HSI) in the EA sample. Finally, we demonstrated the presence of epistasis between GABBR1 and GABBR2 for developing ND. The variants of GABBR1 and GABBR2 are significantly associated with ND, and the involvement of GABBR1 is most likely through its interaction with GABBR2, whereas GABBR2 polymorphisms directly alter susceptibility to ND. Future studies are needed with more dense SNP coverage of GABBR1 and GABBR2 to verify the epistatic effects of the two subunit genes.

    Funded by: NIDA NIH HHS: R01 DA012844, R01 DA025095, R01DA012844, R01DA025095

    PloS one 2009;4;9;e7055

  • 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

  • Determination of genetic predisposition to patent ductus arteriosus in preterm infants.

    Dagle JM, Lepp NT, Cooper ME, Schaa KL, Kelsey KJ, Orr KL, Caprau D, Zimmerman CR, Steffen KM, Johnson KJ, Marazita ML and Murray JC

    Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA. john-dagle@uiowa.edu

    Objective: Patent ductus arteriosus is a common morbidity associated with preterm birth. The incidence of patent ductus arteriosus increases with decreasing gestational age to approximately 70% in infants born at 25 weeks' gestation. Our major goal was to determine if genetic risk factors play a role in patent ductus arteriosus seen in preterm infants.

    Methodology: We investigated whether single-nucleotide polymorphisms in genes that regulate smooth muscle contraction, xenobiotic detoxification, inflammation, and other processes are markers for persistent patency of ductus arteriosus. Initially, 377 single-nucleotide polymorphisms from 130 genes of interest were evaluated in DNA samples collected from 204 infants with a gestational age of <32 weeks. A family-based association test was performed on genotyping data to evaluate overtransmission of alleles.

    Results: P values of <.01 were detected for genetic variations found in 7 genes. This prompted additional analysis with an additional set of 162 infants, focusing on the 7 markers with initial P values of <.01, and 1 genetic variant in the angiotensin II type I receptor previously shown to be related to patent ductus arteriosus. Of the initial positive signals, single-nucleotide polymorphisms in the transcription factor AP-2 beta and tumor necrosis factor receptor-associated factor 1 genes remained significant. Additional haplotype analysis revealed genetic variations in prostacyclin synthase to be associated with patent ductus arteriosus. An angiotensin II type I receptor polymorphism previously reported to be associated with patent ductus arteriosus after prophylactic indomethacin administration was not associated with the presence of a patent ductus arteriosus in our population.

    Conclusions: Overall, our data support a role for genetic variations in transcription factor AP-2 beta, tumor necrosis factor receptor-associated factor 1, and prostacyclin synthase in the persistent patency of the ductus arteriosus seen in preterm infants.

    Funded by: NCRR NIH HHS: M01 RR000059, M01 RR000059-466795; NICHD NIH HHS: R01 HD052953, R01 HD052953-01, T32 HD041922, T32 HD041922-02; NIEHS NIH HHS: P30 ES005605, P30 ES005605-170010, P30 ES005605-180010, P30 ES05605

    Pediatrics 2009;123;4;1116-23

  • Findings from bipolar disorder genome-wide association studies replicate in a Finnish bipolar family-cohort.

    Ollila HM, Soronen P, Silander K, Palo OM, Kieseppä T, Kaunisto MA, Lönnqvist J, Peltonen L, Partonen T and Paunio T

    Funded by: Wellcome Trust: 089061

    Molecular psychiatry 2009;14;4;351-3

  • Expression of GABA(B) receptors is altered in brains of subjects with autism.

    Fatemi SH, Folsom TD, Reutiman TJ and Thuras PD

    Department of Psychiatry, Division of Neuroscience Research, University of Minnesota Medical School, Minneapolis, MN 55455, USA. fatem002@umn.edu

    Autism is a neurodevelopmental disorder that is often comorbid with seizures. Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in brain. GABA(B) receptors play an important role in maintaining excitatory-inhibitory balance in brain and alterations may lead to seizures. We compared levels of GABA(B) receptor subunits GABA(B) receptor 1 (GABBR1) and GABA(B) receptor 2 (GABBR2) in cerebellum, Brodmann's area 9 (BA9), and BA40 of subjects with autism and matched controls. Levels of GABBR1 were significantly decreased in BA9, BA40, and cerebellum, while GABBR2 was significantly reduced in the cerebellum. The presence of seizure disorder did not have a significant impact on the observed reductions in GABA(B) receptor subunit expression. Decreases in GABA(B) receptor subunits may help explain the presence of seizures that are often comorbid with autism, as well as cognitive difficulties prevalent in autism.

    Funded by: NICHD NIH HHS: 5R01HD052074-01A2, R01 HD052074, R01 HD052074-02; NIMH NIH HHS: R24 MH068855

    Cerebellum (London, England) 2009;8;1;64-9

  • Candidate gene/loci studies in cleft lip/palate and dental anomalies finds novel susceptibility genes for clefts.

    Vieira AR, McHenry TG, Daack-Hirsch S, Murray JC and Marazita ML

    Department of 1Oral Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA. arv11@dental.pitt.edu

    Purpose: We revisited 42 families with two or more cleft-affected siblings who participated in previous studies. Complete dental information was collected to test the hypothesis that dental anomalies are part of the cleft phenotype spectrum, and can provide new opportunities for identification of cleft susceptibility genes.

    Methods: Genotypes from 1489 single nucleotide polymorphism markers located in 150 candidate genes/loci were reanalyzed. Two sets of association analyses were carried out. First, we ran the analysis solely on the cleft status. Second, we assigned affection to any cleft or dental anomaly (tooth agenesis, supernumerary teeth, and microdontia) and repeated the analysis.

    Results: Significant over-transmission was seen for a single nucleotide polymorphism in ankyrin repeat and sterile alpha motif domain containing 6 (rs4742741, 9q22.33; P = 0.0004) when a dental anomaly phenotype was included in the analysis. Significant over-transmission was also seen for a single nucleotide polymorphism in ERBB2 (rs1810132, 17q21.1; P = 0.0006). In the clefts only data, the most significant result was also for ERBB2 (P = 0.0006). Other markers with suggestive P values included interferon regulatory factor 6 and 6q21-q23 loci. In contrast to the above results, suggestive over-transmission of markers in GART, DPF3, and neurexin 3 were seen only when the dental anomaly phenotype was included in the analysis.

    Conclusions: These findings support the hypothesis that some loci may contribute to both clefts and congenital dental anomalies. Thus, including dental anomalies information in the genetics analysis of cleft lip and palate will provide new opportunities to map susceptibility loci for clefts.

    Funded by: NHGRI NIH HHS: N01HG65403; NIDCR NIH HHS: P50 DE016215, P50 DE016215-04, P50 DE016215-05, P50-DE016215, R01 DE016148, R01-DE016148, R21 DE016718, R21-DE016718, R37 DE008559, R37 DE008559-18, R37 DE008559-19, R37-DE08559

    Genetics in medicine : official journal of the American College of Medical Genetics 2008;10;9;668-74

  • Gamma-aminobutyric acid receptor genes and nicotine dependence: evidence for association from a case-control study.

    Agrawal A, Pergadia ML, Saccone SF, Hinrichs AL, Lessov-Schlaggar CN, Saccone NL, Neuman RJ, Breslau N, Johnson E, Hatsukami D, Montgomery GW, Heath AC, Martin NG, Goate AM, Rice JP, Bierut LJ and Madden PA

    Department of Psychiatry, Washington University School of Medicine, St Louis, MO 63110, USA. arpana@wustl.edu

    Aims: The gamma-aminobutyric acid receptor A (GABRA) gene clusters on chromosomes 4 and 5 have been examined previously for their association with alcohol and drug dependence phenotypes. Compelling evidence suggests that GABRA2 is associated with alcohol and drug dependence. However, no study has investigated whether genes in the GABA(A) gene clusters are associated with nicotine dependence, an important phenotype with a high correlation to persistent smoking, the single most preventable cause of mortality world-wide.

    Design: Using data on 1050 nicotine-dependent cases and 879 non-dependent smoking controls, we used logistic regression to examine the association between single nucleotide polymorphisms (SNPs) in 13 genes in the GABA(A) receptor system as well as GABBR2 (a GABA(B) gene).

    Findings: We found evidence for association between four SNPs in GABRA4, two SNPs in GABRA2 and one SNP in GABRE with nicotine dependence. These included a synonymous polymorphism in GABRA2 (rs279858), lying in a highly conserved region, which has been shown previously to be associated with alcohol and drug dependence. A non-synonymous polymorphism (rs16859834/rs2229940) in GABRA4, also highly conserved, was associated at P-value of 0.03. Significant haplotypes associated with nicotine dependence were found for GABRA2. No evidence for epistatic interactions were noted. Our study did not find evidence for an association between GABBR2 gene and nicotine dependence.

    Conclusions: Given the potential role of compounds that enhance GABAergic neurotransmission in smoking cessation research, these findings have enormous potential for informing the wider field of addiction research.

    Funded by: NCI NIH HHS: CA89392; NIDA NIH HHS: DA015129, DA019951, DA12854, K01DA015129, K08 DA019951, K08 DA019951-03, N01DA-0-7079; PHS HHS: HHSN271200477471C

    Addiction (Abingdon, England) 2008;103;6;1027-38

  • GABAB receptor association with the PDZ scaffold Mupp1 alters receptor stability and function.

    Balasubramanian S, Fam SR and Hall RA

    Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.

    gamma-Aminobutyric acid, type B (GABA(B)) receptors are heterodimeric G protein-coupled receptors that mediate slow inhibitory synaptic transmission in the central nervous system. To identify novel interacting partners that might regulate GABA(B) receptor (GABA(B)R) functionality, we screened the GABA(B)R2 carboxyl terminus against a recently created proteomic array of 96 distinct PDZ (PSD-95/Dlg/ZO-1 homology) domains. The screen identified three specific PDZ domains that exhibit interactions with GABA(B)R2: Mupp1 PDZ13, PAPIN PDZ1, and Erbin PDZ. Biochemical analysis confirmed that full-length Mupp1 and PAPIN interact with GABA(B)R2 in cells. Disruption of the GABA(B)R2 interaction with PDZ scaffolds by a point mutation to the carboxyl terminus of the receptor dramatically decreased receptor stability and attenuated the duration of GABA(B) receptor signaling. The effects of mutating the GABA(B)R2 carboxyl terminus on receptor stability and signaling were mimicked by small interference RNA knockdown of endogenous Mupp1. These findings reveal that GABA(B) receptor stability and signaling can be modulated via GABA(B)R2 interactions with the PDZ scaffold protein Mupp1, which may contribute to cell-specific regulation of GABA(B) receptors in the central nervous system.

    Funded by: NINDS NIH HHS: NS45644

    The Journal of biological chemistry 2007;282;6;4162-71

  • Functional expression of the GABAB receptor in human airway smooth muscle.

    Osawa Y, Xu D, Sternberg D, Sonett JR, D'Armiento J, Panettieri RA and Emala CW

    Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, 630 W. 168th St., P&S Box 46, New York, NY 10032, USA.

    gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system and exerts its actions via both ionotropic (GABA(A)/GABA(C)) and metabotropic (GABA(B)) receptors (R). In addition to their location on neurons, GABA and functional GABA(B) receptors have been detected in nonneuronal cells in peripheral tissue. Although the GABA(B)R has been shown to function as a prejunctional inhibitory receptor on parasympathetic nerves in the lung, the expression and functional coupling of GABA(B) receptors to G(i) in airway smooth muscle itself have never been described. We detected the mRNA encoding multiple-splice variants of the GABA(B)R1 and GABA(B)R2 in total RNA isolated from native human and guinea pig airway smooth muscle and from RNA isolated from cultured human airway smooth muscle (HASM) cells. Immunoblots identified the GABA(B)R1 and GABA(B)R2 proteins in human native and cultured airway smooth muscle. The GABA(B)R1 protein was immunohistochemically localized to airway smooth muscle in guinea pig tracheal rings. Baclofen, a GABA(B)R agonist, elicited a concentration-dependent stimulation of [(35)S]GTPgammaS binding in HASM homogenates that was abrogated by the GABA(B)R antagonist CGP-35348. Baclofen also inhibited adenylyl cyclase activity and induced ERK phosphorylation in HASM. Another GABA(B)R agonist, SKF-97541, mimicked while pertussis toxin blocked baclofen's effect on ERK phosphorylation, implicating G(i) protein coupling. Functional GABA(B) receptors are expressed in HASM. GABA may modulate an uncharacterized signaling cascade via GABA(B) receptors coupled to the G(i) protein in airway smooth muscle.

    Funded by: NHLBI NIH HHS: HL-58519

    American journal of physiology. Lung cellular and molecular physiology 2006;291;5;L923-31

  • Coordinated action of NSF and PKC regulates GABAB receptor signaling efficacy.

    Pontier SM, Lahaie N, Ginham R, St-Gelais F, Bonin H, Bell DJ, Flynn H, Trudeau LE, McIlhinney J, White JH and Bouvier M

    Département de Biochimie and Groupe de Recherche Universitaire sur le Médicament, Institut de recherche en immunologie et Cancérologie, Université de Montréal, Montréal, Qc, Canada.

    The obligatory heterodimerization of the GABAB receptor (GBR) raises fundamental questions about molecular mechanisms controlling its signaling efficacy. Here, we show that NEM sensitive fusion (NSF) protein interacts directly with the GBR heterodimer both in rat brain synaptosomes and in CHO cells, forming a ternary complex that can be regulated by agonist stimulation. Inhibition of NSF binding with a peptide derived from GBR2 (TAT-Pep-27) did not affect basal signaling activity but almost completely abolished agonist-promoted GBR desensitization in both CHO cells and hippocampal slices. Taken with the role of PKC in the desensitization process, our observation that TAT-Pep-27 prevented both agonist-promoted recruitment of PKC and receptor phosphorylation suggests that NSF is a priming factor required for GBR desensitization. Given that GBR desensitization does not involve receptor internalization, the NSF/PKC coordinated action revealed herein suggests that NSF can regulate GPCR signalling efficacy independently of its role in membrane trafficking. The functional interaction between three bona fide regulators of neurotransmitter release, such as GBR, NSF and PKC, could shed new light on the modulation of presynaptic GBR action.

    Funded by: Medical Research Council: MC_U138162357

    The EMBO journal 2006;25;12;2698-709

  • Towards a proteome-scale map of the human protein-protein interaction network.

    Rual JF, Venkatesan K, Hao T, Hirozane-Kishikawa T, Dricot A, Li N, Berriz GF, Gibbons FD, Dreze M, Ayivi-Guedehoussou N, Klitgord N, Simon C, Boxem M, Milstein S, Rosenberg J, Goldberg DS, Zhang LV, Wong SL, Franklin G, Li S, Albala JS, Lim J, Fraughton C, Llamosas E, Cevik S, Bex C, Lamesch P, Sikorski RS, Vandenhaute J, Zoghbi HY, Smolyar A, Bosak S, Sequerra R, Doucette-Stamm L, Cusick ME, Hill DE, Roth FP and Vidal M

    Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston, Massachusetts 02115, USA.

    Systematic mapping of protein-protein interactions, or 'interactome' mapping, was initiated in model organisms, starting with defined biological processes and then expanding to the scale of the proteome. Although far from complete, such maps have revealed global topological and dynamic features of interactome networks that relate to known biological properties, suggesting that a human interactome map will provide insight into development and disease mechanisms at a systems level. Here we describe an initial version of a proteome-scale map of human binary protein-protein interactions. Using a stringent, high-throughput yeast two-hybrid system, we tested pairwise interactions among the products of approximately 8,100 currently available Gateway-cloned open reading frames and detected approximately 2,800 interactions. This data set, called CCSB-HI1, has a verification rate of approximately 78% as revealed by an independent co-affinity purification assay, and correlates significantly with other biological attributes. The CCSB-HI1 data set increases by approximately 70% the set of available binary interactions within the tested space and reveals more than 300 new connections to over 100 disease-associated proteins. This work represents an important step towards a systematic and comprehensive human interactome project.

    Funded by: NCI NIH HHS: R33 CA132073; NHGRI NIH HHS: P50 HG004233, R01 HG001715, RC4 HG006066, U01 HG001715; NHLBI NIH HHS: U01 HL098166

    Nature 2005;437;7062;1173-8

  • A human protein-protein interaction network: a resource for annotating the proteome.

    Stelzl U, Worm U, Lalowski M, Haenig C, Brembeck FH, Goehler H, Stroedicke M, Zenkner M, Schoenherr A, Koeppen S, Timm J, Mintzlaff S, Abraham C, Bock N, Kietzmann S, Goedde A, Toksöz E, Droege A, Krobitsch S, Korn B, Birchmeier W, Lehrach H and Wanker EE

    Max Delbrueck Center for Molecular Medicine, 13092 Berlin-Buch, Germany.

    Protein-protein interaction maps provide a valuable framework for a better understanding of the functional organization of the proteome. To detect interacting pairs of human proteins systematically, a protein matrix of 4456 baits and 5632 preys was screened by automated yeast two-hybrid (Y2H) interaction mating. We identified 3186 mostly novel interactions among 1705 proteins, resulting in a large, highly connected network. Independent pull-down and co-immunoprecipitation assays validated the overall quality of the Y2H interactions. Using topological and GO criteria, a scoring system was developed to define 911 high-confidence interactions among 401 proteins. Furthermore, the network was searched for interactions linking uncharacterized gene products and human disease proteins to regulatory cellular pathways. Two novel Axin-1 interactions were validated experimentally, characterizing ANP32A and CRMP1 as modulators of Wnt signaling. Systematic human protein interaction screens can lead to a more comprehensive understanding of protein function and cellular processes.

    Cell 2005;122;6;957-68

  • Phosphoproteomic analysis of synaptosomes from human cerebral cortex.

    DeGiorgis JA, Jaffe H, Moreira JE, Carlotti CG, Leite JP, Pant HC and Dosemeci A

    Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.

    Protein phosphorylation is a crucial post-translational modification mechanism in the regulation of synaptic organization and function. Here, we analyzed synaptosome fractions from human cerebral cortex obtained during therapeutic surgery. To minimize changes in the phosphorylation state of proteins, the tissue was homogenized within two minutes of excision. Synaptosomal proteins were digested with trypsin and phosphopeptides were isolated by immobilized metal affinity chromatography and analyzed by liquid chromatography and tandem mass spectrometry. The method allowed the detection of residues on synaptic proteins that were presumably phosphorylated in the intact cell, including synapsin 1, syntaxin 1, and SNIP, PSD-93, NCAM, GABA-B receptor, chaperone molecules, and protein kinases. Some of the residues identified are the same or homologous to sites that had been previously described to be phosphorylated in mammals whereas others appear to be novel sites which, to our knowledge, have not been reported previously. The study shows that new phosphoproteomic strategies can be used to analyze subcellular fractions from small amounts of tissue for the identification of phosphorylated residues for research and potentially for diagnostic purposes.

    Journal of proteome research 2005;4;2;306-15

  • Evidence for a single heptahelical domain being turned on upon activation of a dimeric GPCR.

    Hlavackova V, Goudet C, Kniazeff J, Zikova A, Maurel D, Vol C, Trojanova J, Prézeau L, Pin JP and Blahos J

    Department of Molecular Pharmacology, Institute of Experimental Medicine, Czech Academy of Science, Prague, Czech Republic.

    G-protein-coupled receptors (GPCRs) have been shown to form dimers, but the relevance of this phenomenon in G-protein activation is not known. Among the large GPCR family, metabotropic glutamate (mGlu) receptors are constitutive dimers. Here we examined whether both heptahelical domains (HDs) are turned on upon full receptor activation. To that aim, we measured G-protein coupling efficacy of dimeric mGlu receptors in which one subunit bears specific mutations. We show that a mutation in the third intracellular loop (i3 loop) known to prevent G-protein activation in a single subunit decreases coupling efficacy. However, when a single HD is blocked in its inactive state using an inverse agonist, 2-methyl-6-(phenylethynyl)pyridine (MPEP), no decrease in receptor activity is observed. Interestingly, in a receptor dimer in which the subunit that binds MPEP is mutated in its i3 loop, MPEP enhances agonist-induced activity, reflecting a 'better' activation of the adjacent HD. These data are consistent with a model in which a single HD is turned on upon activation of such homodimeric receptors and raise important issues in deciphering the functional role of GPCR dimer formation for G-protein activation.

    The EMBO journal 2005;24;3;499-509

  • The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).

    Gerhard DS, Wagner L, Feingold EA, Shenmen CM, Grouse LH, Schuler G, Klein SL, Old S, Rasooly R, Good P, Guyer M, Peck AM, Derge JG, Lipman D, Collins FS, Jang W, Sherry S, Feolo M, Misquitta L, Lee E, Rotmistrovsky K, Greenhut SF, Schaefer CF, Buetow K, Bonner TI, Haussler D, Kent J, Kiekhaus M, Furey T, Brent M, Prange C, Schreiber K, Shapiro N, Bhat NK, Hopkins RF, Hsie F, Driscoll T, Soares MB, Casavant TL, Scheetz TE, Brown-stein MJ, Usdin TB, Toshiyuki S, Carninci P, Piao Y, Dudekula DB, Ko MS, Kawakami K, Suzuki Y, Sugano S, Gruber CE, Smith MR, Simmons B, Moore T, Waterman R, Johnson SL, Ruan Y, Wei CL, Mathavan S, Gunaratne PH, Wu J, Garcia AM, Hulyk SW, Fuh E, Yuan Y, Sneed A, Kowis C, Hodgson A, Muzny DM, McPherson J, Gibbs RA, Fahey J, Helton E, Ketteman M, Madan A, Rodrigues S, Sanchez A, Whiting M, Madari A, Young AC, Wetherby KD, Granite SJ, Kwong PN, Brinkley CP, Pearson RL, Bouffard GG, Blakesly RW, Green ED, Dickson MC, Rodriguez AC, Grimwood J, Schmutz J, Myers RM, Butterfield YS, Griffith M, Griffith OL, Krzywinski MI, Liao N, Morin R, Morrin R, Palmquist D, Petrescu AS, Skalska U, Smailus DE, Stott JM, Schnerch A, Schein JE, Jones SJ, Holt RA, Baross A, Marra MA, Clifton S, Makowski KA, Bosak S, Malek J and MGC Project Team

    The National Institutes of Health's Mammalian Gene Collection (MGC) project was designed to generate and sequence a publicly accessible cDNA resource containing a complete open reading frame (ORF) for every human and mouse gene. The project initially used a random strategy to select clones from a large number of cDNA libraries from diverse tissues. Candidate clones were chosen based on 5'-EST sequences, and then fully sequenced to high accuracy and analyzed by algorithms developed for this project. Currently, more than 11,000 human and 10,000 mouse genes are represented in MGC by at least one clone with a full ORF. The random selection approach is now reaching a saturation point, and a transition to protocols targeted at the missing transcripts is now required to complete the mouse and human collections. Comparison of the sequence of the MGC clones to reference genome sequences reveals that most cDNA clones are of very high sequence quality, although it is likely that some cDNAs may carry missense variants as a consequence of experimental artifact, such as PCR, cloning, or reverse transcriptase errors. Recently, a rat cDNA component was added to the project, and ongoing frog (Xenopus) and zebrafish (Danio) cDNA projects were expanded to take advantage of the high-throughput MGC pipeline.

    Funded by: PHS HHS: N01-C0-12400

    Genome research 2004;14;10B;2121-7

  • DNA sequence and analysis of human chromosome 9.

    Humphray SJ, Oliver K, Hunt AR, Plumb RW, Loveland JE, Howe KL, Andrews TD, Searle S, Hunt SE, Scott CE, Jones MC, Ainscough R, Almeida JP, Ambrose KD, Ashwell RI, Babbage AK, Babbage S, Bagguley CL, Bailey J, Banerjee R, Barker DJ, Barlow KF, Bates K, Beasley H, Beasley O, Bird CP, Bray-Allen S, Brown AJ, Brown JY, Burford D, Burrill W, Burton J, Carder C, Carter NP, Chapman JC, Chen Y, Clarke G, Clark SY, Clee CM, Clegg S, Collier RE, Corby N, Crosier M, Cummings AT, Davies J, Dhami P, Dunn M, Dutta I, Dyer LW, Earthrowl ME, Faulkner L, Fleming CJ, Frankish A, Frankland JA, French L, Fricker DG, Garner P, Garnett J, Ghori J, Gilbert JG, Glison C, Grafham DV, Gribble S, Griffiths C, Griffiths-Jones S, Grocock R, Guy J, Hall RE, Hammond S, Harley JL, Harrison ES, Hart EA, Heath PD, Henderson CD, Hopkins BL, Howard PJ, Howden PJ, Huckle E, Johnson C, Johnson D, Joy AA, Kay M, Keenan S, Kershaw JK, Kimberley AM, King A, Knights A, Laird GK, Langford C, Lawlor S, Leongamornlert DA, Leversha M, Lloyd C, Lloyd DM, Lovell J, Martin S, Mashreghi-Mohammadi M, Matthews L, McLaren S, McLay KE, McMurray A, Milne S, Nickerson T, Nisbett J, Nordsiek G, Pearce AV, Peck AI, Porter KM, Pandian R, Pelan S, Phillimore B, Povey S, Ramsey Y, Rand V, Scharfe M, Sehra HK, Shownkeen R, Sims SK, Skuce CD, Smith M, Steward CA, Swarbreck D, Sycamore N, Tester J, Thorpe A, Tracey A, Tromans A, Thomas DW, Wall M, Wallis JM, West AP, Whitehead SL, Willey DL, Williams SA, Wilming L, Wray PW, Young L, Ashurst JL, Coulson A, Blöcker H, Durbin R, Sulston JE, Hubbard T, Jackson MJ, Bentley DR, Beck S, Rogers J and Dunham I

    The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK. sjh@sanger.ac.uk

    Chromosome 9 is highly structurally polymorphic. It contains the largest autosomal block of heterochromatin, which is heteromorphic in 6-8% of humans, whereas pericentric inversions occur in more than 1% of the population. The finished euchromatic sequence of chromosome 9 comprises 109,044,351 base pairs and represents >99.6% of the region. Analysis of the sequence reveals many intra- and interchromosomal duplications, including segmental duplications adjacent to both the centromere and the large heterochromatic block. We have annotated 1,149 genes, including genes implicated in male-to-female sex reversal, cancer and neurodegenerative disease, and 426 pseudogenes. The chromosome contains the largest interferon gene cluster in the human genome. There is also a region of exceptionally high gene and G + C content including genes paralogous to those in the major histocompatibility complex. We have also detected recently duplicated genes that exhibit different rates of sequence divergence, presumably reflecting natural selection.

    Nature 2004;429;6990;369-74

  • Hetero-oligomerization between GABAA and GABAB receptors regulates GABAB receptor trafficking.

    Balasubramanian S, Teissére JA, Raju DV and Hall RA

    Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.

    The neurotransmitter gamma-aminobutyric acid (GABA) mediates inhibitory signaling in the brain via stimulation of both GABA(A) receptors (GABA(A)R), which are chloride-permeant ion channels, and GABA(B) receptors (GABA(B)R), which signal through coupling to G proteins. Here we report physical interactions between these two different classes of GABA receptor. Association of the GABA(B) receptor 1 (GABA(B)R1) with the GABA(A) receptor gamma2S subunit robustly promotes cell surface expression of GABA(B)R1 in the absence of GABA(B)R2, a closely related GABA(B) receptor that is usually required for efficient trafficking of GABA(B)R1 to the cell surface. The GABA(B)R1/gamma2S complex is not detectably functional when expressed alone, as assessed in both ERK activation assays and physiological analyses in oocytes. However, the gamma2S subunit associates not only with GABA(B)R1 alone but also with the functional GABA(B)R1/GABA(B)R2 heterodimer to markedly enhance GABA(B) receptor internalization in response to agonist stimulation. These findings reveal that the GABA(B)R1/gamma2S interaction results in the regulation of multiple aspects of GABA(B) receptor trafficking, allowing for cross-talk between these two distinct classes of GABA receptor.

    Funded by: NINDS NIH HHS: R01-NS45644

    The Journal of biological chemistry 2004;279;18;18840-50

  • Comparative cellular distribution of GABAA and GABAB receptors in the human basal ganglia: immunohistochemical colocalization of the alpha 1 subunit of the GABAA receptor, and the GABABR1 and GABABR2 receptor subunits.

    Waldvogel HJ, Billinton A, White JH, Emson PC and Faull RL

    Department of Anatomy with Radiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand. h.waldvogel@auckland.ac.nz

    The GABA(B) receptor is a G-protein linked metabotropic receptor that is comprised of two major subunits, GABA(B)R1 and GABA(B)R2. In this study, the cellular distribution of the GABA(B)R1 and GABA(B)R2 subunits was investigated in the normal human basal ganglia using single and double immunohistochemical labeling techniques on fixed human brain tissue. The results showed that the GABA(B) receptor subunits GABA(B)R1 and GABA(B)R2 were both found on the same neurons and followed the same distribution patterns. In the striatum, these subunits were found on the five major types of interneurons based on morphology and neurochemical labeling (types 1, 2, 3, 5, 6) and showed weak labeling on the projection neurons (type 4). In the globus pallidus, intense GABA(B)R1 and GABA(B)R2 subunit labeling was found in large pallidal neurons, and in the substantia nigra, both pars compacta and pars reticulata neurons were labeled for both receptor subunits. Studies investigating the colocalization of the GABA(A) alpha(1) subunit and GABA(B) receptor subunits showed that the GABA(A) receptor alpha(1) subunit and the GABA(B)R1 subunit were found together on GABAergic striatal interneurons (type 1 parvalbumin, type 2 calretinin, and type 3 GAD neurons) and on neurons in the globus pallidus and substantia nigra pars reticulata. GABA(B)R1 and GABA(B)R2 were found on substantia nigra pars compacta neurons but the GABA(A) receptor alpha(1) subunit was absent from these neurons. The results of this study provide the morphological basis for GABAergic transmission within the human basal ganglia and provides evidence that GABA acts through both GABA(A) and GABA(B) receptors. That is, GABA acts through GABA(B) receptors, which are located on most of the cell types of the striatum, globus pallidus, and substantia nigra. GABA also acts through GABA(A) receptors containing the alpha(1) subunit on specific striatal GABAergic interneurons and on output neurons of the globus pallidus and substantia nigra pars reticulata.

    The Journal of comparative neurology 2004;470;4;339-56

  • Characterization of GABAB receptor in the human colon.

    Uezono Y, Kaibara M, Hayashi H, Kawakami S, Enjoji A, Kanematsu T and Taniyama K

    Division of Pharmacology, Department of Translational Medical Sciences, Nagasaki University Graduate School of Biomedical Sciences, Japan.

    Characterization of the GABA(B) receptor in the human colon was performed by the reverse transcription-polymerase chain reaction (RT-PCR). mRNAs for both subunits of the GABA(B) receptor, GABA(B1) and GABA(B2), were detected in the human colon. The GABA(B1(e)) isoform was detected in the human colon, but not in the brain, and the other isoforms, except GABA(B1(d)), were detected in both tissues. Thus, the GABA(B) receptor may be present as a heterodimer with subunits of GABA(B1) and GABA(B2) in the human colon.

    Journal of pharmacological sciences 2004;94;2;211-3

  • Increased expression of gamma-aminobutyric acid type B receptors in the hippocampus of patients with temporal lobe epilepsy.

    Furtinger S, Pirker S, Czech T, Baumgartner C and Sperk G

    Department of Pharmacology, University of Innsbruck, 6020 Innsbruck, Austria.

    Malfunctioning of the GABA-ergic system has been postulated as a possible cause of epilepsy. We investigated changes in the mRNA expression of the GABA(B) receptor subtypes GABA(B)-R1 and GABA(B)-R2 and of GABA(B) receptor binding in the hippocampus of patients with temporal lobe epilepsy (TLE) compared with post-mortem controls. In patients with Ammon's horn sclerosis, significant decreases in [3H]CG54626A binding were observed in subfields CA1 and CA3 of the hippocampus proper and the dentate hilus. On the other hand, both GABA(B) receptor mRNAs and receptor binding were enhanced after correction for neuronal loss in dentate granule cells and in the molecular layer, respectively, and the subiculum of patients with and without hippocampal sclerosis. These increases were even more pronounced when correcting the values for cell losses in the respective areas and indicated also increased expression of GABA(B)-R in the dentate hilus. Increased expression of both subtypes of GABA(B) receptors indicates augmented presynaptic inhibition of glutamate release as a possible protective mechanism in TLE.

    Neuroscience letters 2003;352;2;141-5

  • Oligomerization of G-protein-coupled receptors shown by selective co-immunoprecipitation.

    Salim K, Fenton T, Bacha J, Urien-Rodriguez H, Bonnert T, Skynner HA, Watts E, Kerby J, Heald A, Beer M, McAllister G and Guest PC

    Neuroscience Research Centre, Merck Sharp & Dohme Research Laboratories, Harlow, Essex CM20 2QR, United Kingdom. kamran_salim@merck.com

    Recent studies have shown that G-protein-coupled receptors (GPCRs) can assemble as high molecular weight homo- and hetero-oligomeric complexes. This can result in altered receptor-ligand binding, signaling, or intracellular trafficking. We have co-transfected HEK-293 cells with differentially epitope-tagged GPCRs from different subfamilies and determined whether oligomeric complexes were formed by co-immunoprecipitation and immunoblot analysis. This gave the surprising result that the 5HT(1A) receptor was capable of forming hetero-oligomers with all GPCRs tested including the 5HT(1B), 5HT(1D), EDG(1), EDG(3), GPR(26), and GABA(B2) receptors. The testing of other GPCR combinations showed similar results with hetero-oligomer formation occurring for the 5HT(1D) with the 5HT(1B) and EDG(1) receptor. Control studies showed that these complexes were present in co-transfected cells before the time of lysis and that the hetero-oligomers were comprised of GPCRs at discrete stoichiometries. These findings suggest that GPCRs have a natural tendency to form oligomers when co-transfected into cells. Future studies should therefore investigate the presence and physiological role of GPCR hetero-oligomers in cells in which they are endogenously expressed.

    The Journal of biological chemistry 2002;277;18;15482-5

  • Tamalin, a PDZ domain-containing protein, links a protein complex formation of group 1 metabotropic glutamate receptors and the guanine nucleotide exchange factor cytohesins.

    Kitano J, Kimura K, Yamazaki Y, Soda T, Shigemoto R, Nakajima Y and Nakanishi S

    Department of Biological Sciences, Faculty of Medicine, Graduate School of Biostudies, Kyoto University, Kyoto, 606-8501, Japan.

    In this investigation, we report identification and characterization of a 95 kDa postsynaptic density protein (PSD-95)/discs-large/ZO-1 (PDZ) domain-containing protein termed tamalin, also recently named GRP1-associated scaffold protein (GRASP), that interacts with group 1 metabotropic glutamate receptors (mGluRs). The yeast two-hybrid system and in vitro pull-down assays indicated that the PDZ domain-containing, amino-terminal half of tamalin directly binds to the class I PDZ-binding motif of group 1 mGluRs. The C-terminal half of tamalin also bound to cytohesins, the members of guanine nucleotide exchange factors (GEFs) specific for the ADP-ribosylation factor (ARF) family of small GTP-binding proteins. Tamalin mRNA is expressed predominantly in the telencephalic region and highly overlaps with the expression of group 1 mGluR mRNAs. Both tamalin and cytohesin-2 were enriched and codistributed with mGluR1a in postsynaptic membrane fractions. Importantly, recombinant and native mGluR1a/tamalin/cytohesin-2 complexes were coimmunoprecipitated from transfected COS-7 cells and rat brain tissue, respectively. Transfection of tamalin and mutant tamalin lacking a cytohesin-binding domain caused an increase and decrease in cell-surface expression of mGluR1a in COS-7 cells, respectively. Furthermore, adenovirus-mediated expression of tamalin and dominant-negative tamalin facilitated and reduced the neuritic distribution of endogenous mGluR5 in cultured hippocampal neurons, respectively. The results indicate that tamalin plays a key role in the association of group 1 mGluRs with the ARF-specific GEF proteins and contributes to intracellular trafficking and the macromolecular organization of group 1 mGluRs at synapses.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2002;22;4;1280-9

  • The GABAB receptor interacts directly with the related transcription factors CREB2 and ATFx.

    White JH, McIllhinney RA, Wise A, Ciruela F, Chan WY, Emson PC, Billinton A and Marshall FH

    Receptor Systems, Molecular Pharmacology Department, Glaxo Wellcome Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, United Kingdom. Jw6155@glaxowellcome.co.uk

    gamma-Aminobutyric acid type B (GABA(B)) receptors mediate the metabotropic actions of the inhibitory neurotransmitter GABA. These seven-transmembrane receptors are known to signal primarily through activation of G proteins to modulate the action of ion channels or second messengers. The functional GABA(B) receptor is made up of a heterodimer consisting of two subunits, GABA(B)-R1 and GABA(B)-R2, which interact via coiled-coil domains in their C-terminal tails. By using a yeast two-hybrid approach, we have identified direct interactions between the C-terminal tails of GABA(B)-R1 and GABA(B)-R2 with two related transcription factors, CREB2 (ATF4) and ATFx. In primary neuronal cultures as well in recombinant Chinese hamster ovary cells expressing GABA(B) receptors, CREB2 is localized within the cytoplasm as well as the nucleus. Activation of the GABA(B) receptor by the specific agonist baclofen leads to a marked translocation and accumulation of CREB2 from the cytoplasm into the nucleus. We demonstrate that receptor stimulation results in activation of transcription from a CREB2 responsive reporter gene. Such a signaling mechanism is unique among Family C G protein-coupled receptors and, in the case of the GABA(B) receptor and CREB2, may play a role in long-term changes in the nervous system.

    Proceedings of the National Academy of Sciences of the United States of America 2000;97;25;13967-72

  • Coexpression of full-length gamma-aminobutyric acid(B) (GABA(B)) receptors with truncated receptors and metabotropic glutamate receptor 4 supports the GABA(B) heterodimer as the functional receptor.

    Sullivan R, Chateauneuf A, Coulombe N, Kolakowski LF, Johnson MP, Hebert TE, Ethier N, Belley M, Metters K, Abramovitz M, O'Neill GP and Ng GY

    Department of Biochemistry, Molecular Biology and Chemistry, Merck Frosst Center for Therapeutic Research, Kirkland, Quebec, Canada.

    Direct evidence is lacking to show whether the gamma-aminobutyric acid (GABA)(B) gb1-gb2 heterodimer is the signaling form of the receptor. In this study, we tested whether gb1a or gb2 subunits when coexpressed with truncated receptors or metabotropic glutamate receptor mGluR4 could form functional GABA receptors. Coexpression of the ligand binding N-terminal domain of gb1a or the C-terminal portion of gb1a composing the seven-transmembrane segments and intracellular loops with gb2 could not reconstitute functional receptors. We next examined whether mGluR4, which forms homodimers and is structurally related to GABA(B), could act as a surrogate coreceptor for gb1 or gb2. The coexpression of mGluR4 and gb1a led to the expression of gb1a monomers on cell surface membranes as determined by immunoblot analysis and flow cytometry. However, mGluR4-gb1a heterodimers were not formed, and membrane-expressed gb1a monomers were not functionally coupled to adenylyl cyclase in human embryonic kidney 293 cells or activated inwardly rectifying potassium (Kir) channels in Xenopus oocytes. Similarly, the coexpression of mGluR4 and gb2 led to nonfunctional GABA receptors. GABA-activated distal signaling events resulted only after the coexpression and heterodimerization of gb1 and gb2. Taken together with the truncated receptor studies, the data suggest that a high degree of structural specificity is required to form the functional GABA(B) receptor that is a gb1-gb2 heterodimer.

    The Journal of pharmacology and experimental therapeutics 2000;293;2;460-7

  • Distribution of the GABA(B) receptor subunit gb2 in rat CNS.

    Clark JA, Mezey E, Lam AS and Bonner TI

    Laboratory of Genetics, National Institute of Mental Health, 36 Convent Drive, MSC 4094, Bethesda, MD, USA. janet@codon.nih.gov

    We have identified and isolated human and rat cDNAs for a novel receptor, gb2, with 38% homology to the GABA(B) receptors gb1a and gb1b. These receptors comprise a new subfamily of seven transmembrane G protein-coupled receptors (GPCRs) that share structure and sequence similarities with the metabotropic glutamate receptors. In situ hybridization histochemistry using an antisense probe to this novel receptor mRNA shows a distribution in rat CNS nearly identical to that for the gb1 receptor, although some regions showed significant differences. Specifically, message levels for gb2 were virtually absent in the caudate/putamen, and significantly lower in the medial basal hypothalamus, septum and brainstem as compared with gb1 message levels. In contrast to gb1, gb2 mRNA was never detected in white matter suggesting that gb2 message is found exclusively in neurons. Finally, in rat brain regions showing significant overlap of message for gb1 and gb2, the transcripts are often found in the same cells. Data from our previous work showing that coexpression of gb2 with gb1 is necessary for expression of a functional receptor together with the detailed anatomical data presented here indicate that native GABA(B) receptors function as heteromeric proteins, the most abundant form being the gb1/gb2 receptor. However, the more limited distribution of gb2 receptor mRNA suggests that there are brain regions where GABA(B) receptors are composed of gb1 and as yet unidentified family members.

    Brain research 2000;860;1-2;41-52

  • Identification of a GABAB receptor subunit, gb2, required for functional GABAB receptor activity.

    Ng GY, Clark J, Coulombe N, Ethier N, Hebert TE, Sullivan R, Kargman S, Chateauneuf A, Tsukamoto N, McDonald T, Whiting P, Mezey E, Johnson MP, Liu Q, Kolakowski LF, Evans JF, Bonner TI and O'Neill GP

    Merck Frosst Center for Therapeutic Research, Kirkland, Quebec H9H 3L1, Canada. gordon_ng@merck.com

    G protein-coupled receptors are commonly thought to bind their cognate ligands and elicit functional responses primarily as monomeric receptors. In studying the recombinant gamma-aminobutyric acid, type B (GABAB) receptor (gb1a) and a GABAB-like orphan receptor (gb2), we observed that both receptors are functionally inactive when expressed individually in multiple heterologous systems. Characterization of the tissue distribution of each of the receptors by in situ hybridization histochemistry in rat brain revealed co-localization of gb1 and gb2 transcripts in many brain regions, suggesting the hypothesis that gb1 and gb2 may interact in vivo. In three established functional systems (inwardly rectifying K+ channel currents in Xenopus oocytes, melanophore pigment aggregation, and direct cAMP measurements in HEK-293 cells), GABA mediated a functional response in cells coexpressing gb1a and gb2 but not in cells expressing either receptor individually. This GABA activity could be blocked with the GABAB receptor antagonist CGP71872. In COS-7 cells coexpressing gb1a and gb2 receptors, co-immunoprecipitation of gb1a and gb2 receptors was demonstrated, indicating that gb1a and gb2 act as subunits in the formation of a functional GABAB receptor.

    The Journal of biological chemistry 1999;274;12;7607-10

  • Cloning of a novel G-protein-coupled receptor GPR 51 resembling GABAB receptors expressed predominantly in nervous tissues and mapped proximal to the hereditary sensory neuropathy type 1 locus on chromosome 9.

    Ng GY, McDonald T, Bonnert T, Rigby M, Heavens R, Whiting P, Chateauneuf A, Coulombe N, Kargman S, Caskey T, Evans J, O'neill GP and Liu Q

    Department of Biochemistry and Molecular Biology, Merck Frosst Center for Therapeutic Research, 16711 TransCanada Highway, Kirkland, Quebec, H9H 3L1, Canada.gordon_ng@merck.com

    Query of the expressed sequence tag database with the rat metabotropic GABABR1A receptor amino acid sequence using the TFASTA algorithm revealed two partial cDNA fragments whose sequence information was then used to isolate by PCR a novel full-length human cDNA encoding a putative G-protein-coupled receptor (GPCR), termed GPR 51. Sequence analysis revealed that it encoded a protein of 941 amino acids, similar in size and homology to GABAB receptors followed by metabotropic glutamate receptors but not other GPCRs. GPR 51 expressed in COS-1 cells showed no specific binding for [3H](+)baclofen and when expressed in Xenopus oocyte and Xenopus melanophore functional assays showed no activity to GABA, (-)baclofen, and glutamic acid. Northern blot analysis and in situ hybridization revealed that GPR 51 transcripts were predominantly expressed in the central nervous system with highest abundance in the cortex, thalamus, hippocampus, amygdala, cerebellum, and spinal cord. In contrast, GPR 51 receptor transcripts were almost not detected in the peripheral tissues. Gene GPR 51 was localized by radiation hybrid mapping to chromosome 9, 4.81 cR from the WI-8684 marker, and proximal to the hereditary sensory neuropathy type 1 locus.

    Genomics 1999;56;3;288-95

  • Molecular identification of the human GABABR2: cell surface expression and coupling to adenylyl cyclase in the absence of GABABR1.

    Martin SC, Russek SJ and Farb DH

    Department of Pharmacology, Boston University School of Medicine, 715 Albany Street, Boston, Massachusetts, 02118-2394, USA.

    We have identified a gene encoding a GABAB receptor, the human GABABR2, located on chromosome 9q22.1, that is distinct from the recently reported rat GABABR1. GABABR2 structurally resembles GABABR1 (35% identity), having seven transmembrane domains and a large extracellular region, but differs in having a longer carboxy-terminal tail. GABABR2 is localized to the cell surface in transfected COS cells, and negatively couples to adenylyl cyclase in response to GABA, baclofen, and 3-aminopropyl(methyl)phosphinic acid in CHO cells lacking GABABR1. Baclofen action is inhibited by the GABABR antagonist, 2-hydroxysaclofen. The human GABABR2 and GABABR1 genes are differentially expressed in the nervous system, with the greatest difference being detected in the striatum in which GABABR1 but not GABABR2 mRNA transcripts are detected. GABABR2 and GABABR1 mRNAs are also coexpressed in various brain regions such as the Purkinje cell layer of the cerebellum. Identification of a functional homomeric GABABR2 coupled to adenylyl cyclase suggests that the complexity of GABAB pharmacological data is at least in part due to the presence of more than one receptor and opens avenues for future research leading to an understanding of metabotropic GABA receptor signal transduction mechanisms.

    Molecular and cellular neurosciences 1999;13;3;180-91

  • GABA(B)-receptor subtypes assemble into functional heteromeric complexes.

    Kaupmann K, Malitschek B, Schuler V, Heid J, Froestl W, Beck P, Mosbacher J, Bischoff S, Kulik A, Shigemoto R, Karschin A and Bettler B

    Novartis Pharma AG, TA Nervous System, Basel, Switzerland.

    B-type receptors for the neurotransmitter GABA (gamma-aminobutyric acid) inhibit neuronal activity through G-protein-coupled second-messenger systems, which regulate the release of neurotransmitters and the activity of ion channels and adenylyl cyclase. Physiological and biochemical studies show that there are differences in drug efficiencies at different GABA(B) receptors, so it is expected that GABA(B)-receptor (GABA(B)R) subtypes exist. Two GABA(B)-receptor splice variants have been cloned (GABA(B)R1a and GABA(B)R1b), but native GABA(B) receptors and recombinant receptors showed unexplained differences in agonist-binding potencies. Moreover, the activation of presumed effector ion channels in heterologous cells expressing the recombinant receptors proved difficult. Here we describe a new GABA(B) receptor subtype, GABA(B)R2, which does not bind available GABA(B) antagonists with measurable potency. GABA(B)R1a, GABA(B)R1b and GABA(B)R2 alone do not activate Kir3-type potassium channels efficiently, but co-expression of these receptors yields a robust coupling to activation of Kir3 channels. We provide evidence for the assembly of heteromeric GABA(B) receptors in vivo and show that GABA(B)R2 and GABA(B)R1a/b proteins immunoprecipitate and localize together at dendritic spines. The heteromeric receptor complexes exhibit a significant increase in agonist- and partial-agonist-binding potencies as compared with individual receptors and probably represent the predominant native GABA(B) receptor. Heteromeric assembly among G-protein-coupled receptors has not, to our knowledge, been described before.

    Nature 1998;396;6712;683-7

  • Heterodimerization is required for the formation of a functional GABA(B) receptor.

    White JH, Wise A, Main MJ, Green A, Fraser NJ, Disney GH, Barnes AA, Emson P, Foord SM and Marshall FH

    Receptor Systems, Molecular Pharmacology Unit, GlaxoWellcome, Medicines Research Centre, Stevenage, Hertfordshire, UK.

    GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the mammalian central nervous system, where it exerts its effects through ionotropic (GABA(A/C)) receptors to produce fast synaptic inhibition and metabotropic (GABA(B)) receptors to produce slow, prolonged inhibitory signals. The gene encoding a GABA(B) receptor (GABA(B)R1) has been cloned; however, when expressed in mammalian cells this receptor is retained as an immature glycoprotein on intracellular membranes and exhibits low affinity for agonists compared with the endogenous receptor on brain membranes. Here we report the cloning of a complementary DNA encoding a new subtype of the GABAB receptor (GABA(B)R2), which we identified by mining expressed-sequence-tag databases. Yeast two-hybrid screening showed that this new GABA(B)R2-receptor subtype forms heterodimers with GABA(B)R1 through an interaction at their intracellular carboxy-terminal tails. Upon expression with GABA(B)R2 in HEK293T cells, GABA(B)R1 is terminally glycosylated and expressed at the cell surface. Co-expression of the two receptors produces a fully functional GABA(B) receptor at the cell surface; this receptor binds GABA with a high affinity equivalent to that of the endogenous brain receptor. These results indicate that, in vivo, functional brain GABA(B) receptors may be heterodimers composed of GABA(B)R1 and GABA(B)R2.

    Nature 1998;396;6712;679-82

  • GABAB receptors.

    Kerr DI and Ong J

    Department of Anaesthesia and Intensive Care, University of Adelaide, Australia.

    GABAB receptors are a distinct subclass of receptors for the major inhibitory transmitter 4-aminobutanoic acid (GABA) that mediate depression of synaptic transmission and contribute to the inhibition controlling neuronal excitability. The development of specific agonists and antagonists for these receptors has led to a better understanding of their physiology and pharmacology, highlighting their diverse coupling to different intracellular effectors through Gi/G(o) proteins. This review emphasises our current knowledge of the neurophysiology and neurochemistry of GABAB receptors, including their heterogeneity, as well as the therapeutic potential of drugs acting at these sites.

    Pharmacology & therapeutics 1995;67;2;187-246

Gene lists (6)

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
L00000016 G2C Homo sapiens Human PSP Human orthologues of mouse PSP adapted from Collins et al (2006) 1121
L00000059 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-CONSENSUS Human cortex PSD consensus 748
L00000061 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-CONSENSUS Mouse cortex PSD consensus (ortho) 984
L00000069 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-FULL Human cortex biopsy PSD full list 1461
L00000071 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-FULL Mouse cortex PSD full list (ortho) 1556
© 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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