text:
G2Cdb::Gene report
- Gene id
- Gene symbol
- Species
- Homo sapiens
- Description
- discs, large homolog 2 (Drosophila)
- Orthologue
- G00000010 (Mus musculus)
Databases (7)
Synonyms (3)
- chapsyn-110
Literature (52)
Pubmed - other
Evaluation of DLG2 as a positional candidate for disposition index in African-Americans from the IRAS Family Study.
Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
Aims: Evaluate discs large homolog 2 (DLG2) as a positional candidate gene for disposition index (DI) in the Insulin Resistance Atherosclerosis Family Study (IRAS-FS) African-American sample.
Methods: SNPs (n=193) were selected for genotyping in 580 African-American individuals using a modified tagging algorithm. Follow-up genotyping was carried out within regions associated with DI. A subset of highly associated, uncorrelated SNPs was used as covariates in the linkage analysis to assess their contribution to linkage.
Results: Evidence of association with DI was observed at the DLG2 locus (admixture-adjusted P=0.050-8.7 x 10(-5)) with additional signals observed in follow-up genotyping of 17 SNPs (P=0.033-0.0012). Inclusion of highly associated, uncorrelated SNPs as covariates in the linkage analysis explained linkage at the DLG2 locus (90.8 cM) and reduced the maximal LOD score (72.0 cM) from 4.37 to 3.71.
Conclusions: Evidence of association and an observed contribution to evidence for linkage to DI was observed for SNPs in DLG2 genotyped on the African-American individuals from the IRAS-FS. Although not the only gene in the region, these results suggest that variation at the DLG2 locus contributes to maintenance of glucose homeostasis through regulation of insulin sensitivity and beta-cell function as measured by DI.
Funded by: NHGRI NIH HHS: N01HG65403; NHLBI NIH HHS: HL060894, HL060931, HL060944, HL061019, HL061210, R01 HL060894, R01 HL060894-01A1, R01 HL060931, R01 HL060931-01A1, R01 HL060944, R01 HL060944-01A1, R01 HL061019, R01 HL061019-06A1, R01 HL061210, R01 HL061210-01A1; NIDDK NIH HHS: R01 DK029867
Diabetes research and clinical practice 2010;87;1;69-76
PUBMED: 19931931; PMC: 2818538; DOI: 10.1016/j.diabres.2009.10.015
Structure of the first PDZ domain of human PSD-93.
Biostructural Research, Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
The crystal structure of the PDZ1 domain of human PSD-93 has been determined to 2.0 A resolution. The PDZ1 domain forms a crystallographic trimer that is also predicted to be stable in solution. The main contributions to the stabilization of the trimer seem to arise from interactions involving the PDZ1-PDZ2 linker region at the extreme C-terminus of PDZ1, implying that the oligomerization that is observed is not of biological significance in full-length PSD-93. Comparison of the structures of the binding cleft of PSD-93 PDZ1 with the previously reported structures of PSD-93 PDZ2 and PDZ3 as well as of the closely related human PSD-95 PDZ1 shows that they are very similar in terms of amino-acid composition. However, the cleft is significantly narrower in PSD-95. This could be part of the basis of peptide selectivity between PSD-93 PDZ1 and PSD-95 PDZ1.
Acta crystallographica. Section F, Structural biology and crystallization communications 2009;65;Pt 12;1254-7
Identification of SH3 domain interaction partners of human FasL (CD178) by phage display screening.
Institute of Immunology, Christian-Albrechts-University of Kiel, D-24105 Kiel, Germany. firstname.lastname@example.com
Background: Fas ligand is a cytotoxic effector molecule of T and NK cells which is characterized by an intracellular N-terminal polyproline region that serves as a docking site for SH3 and WW domain proteins. Several previously described Fas ligand-interacting SH3 domain proteins turned out to be crucial for the regulation of storage, expression and function of the death factor. Recent observations, however, indicate that Fas ligand is also subject to posttranslational modifications including shedding and intramembrane proteolysis. This results in the generation of short intracellular fragments that might either be degraded or translocate to the nucleus to influence transcription. So far, protein-protein interactions that specifically regulate the fate of the intracellular fragments have not been identified.
Results: In order to further define the SH3 domain interactome of the intracellular region of Fas ligand, we now screened a human SH3 domain phage display library. In addition to known SH3 domains mediating binding to the Fas ligand proline-rich domain, we were able to identify a number of additional SH3 domains that might also associate with FasL. Potential functional implications of the new binding proteins for the death factor's biology are discussed. For Tec kinases and sorting nexins, the observed interactions were verified in cellular systems by pulldown experiments.
Conclusion: We provide an extended list of putative Fas ligand interaction partners, confirming previously identified interactions, but also introducing several novel SH3 domain proteins that might be important regulators of Fas ligand function.
BMC immunology 2009;10;53
A genome-wide association study of northwestern Europeans involves the C-type natriuretic peptide signaling pathway in the etiology of human height variation.
Department of Internal Medicine, Erasmus University Medical Center Rotterdam, Rotterdam, The Netherlands.
Northwestern Europeans are among the tallest of human populations. The increase in body height in these people appears to have reached a plateau, suggesting the ubiquitous presence of an optimal environment in which genetic factors may have exerted a particularly strong influence on human growth. Therefore, we performed a genome-wide association study (GWAS) of body height using 2.2 million markers in 10 074 individuals from three Dutch and one German population-based cohorts. Upon genotyping, the 12 most significantly height-associated single nucleotide polymorphisms (SNPs) from this GWAS in 6912 additional individuals of Dutch and Swedish origin, a genetic variant (rs6717918) on chromosome 2q37.1 was found to be associated with height at a genome-wide significance level (P(combined) = 3.4 x 10(-9)). Notably, a second SNP (rs6718438) located approximately 450 bp away and in strong LD (r(2) = 0.77) with rs6717918 was previously found to be suggestive of a height association in 29 820 individuals of mainly northwestern European ancestry, and the over-expression of a nearby natriuretic peptide precursor type C (NPPC) gene, has been associated with overgrowth and skeletal anomalies. We also found a SNP (rs10472828) located on 5p14 near the natriuretic peptide receptor 3 (NPR3) gene, encoding a receptor of the NPPC ligand, to be associated with body height (P(combined) = 2.1 x 10(-7)). Taken together, these results suggest that variation in the C-type natriuretic peptide signaling pathway, involving the NPPC and NPR3 genes, plays an important role in determining human body height.
Funded by: NIMH NIH HHS: MH081802
Human molecular genetics 2009;18;18;3516-24
PUBMED: 19570815; PMC: 2729669; DOI: 10.1093/hmg/ddp296
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.
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
PUBMED: 19086053; DOI: 10.1002/ajmg.b.30902
Recurrent rearrangements in synaptic and neurodevelopmental genes and shared biologic pathways in schizophrenia, autism, and mental retardation.
Institut National de la Santé et de la Recherche Médicale, Unité 614, Institut Hospitalo-Universitaire de Recherche Biomédicale, 76000 Rouen, France.
Context: Results of comparative genomic hybridization studies have suggested that rare copy number variations (CNVs) at numerous loci are involved in the cause of mental retardation, autism spectrum disorders, and schizophrenia.
Objectives: To provide an estimate of the collective frequency of a set of recurrent or overlapping CNVs in 3 different groups of cases compared with healthy control subjects and to assess whether each CNV is present in more than 1 clinical category.
Design: Case-control study.
Setting: Academic research.
Participants: We investigated 28 candidate loci previously identified by comparative genomic hybridization studies for gene dosage alteration in 247 cases with mental retardation, in 260 cases with autism spectrum disorders, in 236 cases with schizophrenia or schizoaffective disorder, and in 236 controls.
Collective and individual frequencies of the analyzed CNVs in cases compared with controls.
Results: Recurrent or overlapping CNVs were found in cases at 39.3% of the selected loci. The collective frequency of CNVs at these loci is significantly increased in cases with autism, in cases with schizophrenia, and in cases with mental retardation compared with controls (P < .001, P = .01, and P = .001, respectively, Fisher exact test). Individual significance (P = .02 without correction for multiple testing) was reached for the association between autism and a 350-kilobase deletion located at 22q11 and spanning the PRODH and DGCR6 genes.
Conclusions: Weakly to moderately recurrent CNVs (transmitted or occurring de novo) seem to be causative or contributory factors for these diseases. Most of these CNVs (which contain genes involved in neurotransmission or in synapse formation and maintenance) are present in the 3 pathologic conditions (schizophrenia, autism, and mental retardation), supporting the existence of shared biologic pathways in these neurodevelopmental disorders.
Archives of general psychiatry 2009;66;9;947-56
PUBMED: 19736351; PMC: 2958844; DOI: 10.1001/archgenpsychiatry.2009.80
Preso, a novel PSD-95-interacting FERM and PDZ domain protein that regulates dendritic spine morphogenesis.
National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea.
PSD-95 is an abundant postsynaptic density (PSD) protein involved in the formation and regulation of excitatory synapses and dendritic spines, but the underlying mechanisms are not comprehensively understood. Here we report a novel PSD-95-interacting protein Preso that regulates spine morphogenesis. Preso is mainly expressed in the brain and contains WW (domain with two conserved Trp residues), PDZ (PSD-95/Dlg/ZO-1), FERM (4.1, ezrin, radixin, and moesin), and C-terminal PDZ-binding domains. These domains associate with actin filaments, the Rac1/Cdc42 guanine nucleotide exchange factor betaPix, phosphatidylinositol-4,5-bisphosphate, and the postsynaptic scaffolding protein PSD-95, respectively. Preso overexpression increases the density of dendritic spines in a manner requiring WW, PDZ, FERM, and PDZ-binding domains. Conversely, knockdown or dominant-negative inhibition of Preso decreases spine density, excitatory synaptic transmission, and the spine level of filamentous actin. These results suggest that Preso positively regulates spine density through its interaction with the synaptic plasma membrane, actin filaments, PSD-95, and the betaPix-based Rac1 signaling pathway.
The Journal of neuroscience : the official journal of the Society for Neuroscience 2008;28;53;14546-56
A genome-wide association study identifies protein quantitative trait loci (pQTLs).
Department of Epidemiology and Public Health, Institute of Biomedical and Clinical Sciences, Peninsula College of Medicine and Dentistry, University of Exeter, Devon, United Kingdom.
There is considerable evidence that human genetic variation influences gene expression. Genome-wide studies have revealed that mRNA levels are associated with genetic variation in or close to the gene coding for those mRNA transcripts - cis effects, and elsewhere in the genome - trans effects. The role of genetic variation in determining protein levels has not been systematically assessed. Using a genome-wide association approach we show that common genetic variation influences levels of clinically relevant proteins in human serum and plasma. We evaluated the role of 496,032 polymorphisms on levels of 42 proteins measured in 1200 fasting individuals from the population based InCHIANTI study. Proteins included insulin, several interleukins, adipokines, chemokines, and liver function markers that are implicated in many common diseases including metabolic, inflammatory, and infectious conditions. We identified eight Cis effects, including variants in or near the IL6R (p = 1.8x10(-57)), CCL4L1 (p = 3.9x10(-21)), IL18 (p = 6.8x10(-13)), LPA (p = 4.4x10(-10)), GGT1 (p = 1.5x10(-7)), SHBG (p = 3.1x10(-7)), CRP (p = 6.4x10(-6)) and IL1RN (p = 7.3x10(-6)) genes, all associated with their respective protein products with effect sizes ranging from 0.19 to 0.69 standard deviations per allele. Mechanisms implicated include altered rates of cleavage of bound to unbound soluble receptor (IL6R), altered secretion rates of different sized proteins (LPA), variation in gene copy number (CCL4L1) and altered transcription (GGT1). We identified one novel trans effect that was an association between ABO blood group and tumour necrosis factor alpha (TNF-alpha) levels (p = 6.8x10(-40)), but this finding was not present when TNF-alpha was measured using a different assay , or in a second study, suggesting an assay-specific association. Our results show that protein levels share some of the features of the genetics of gene expression. These include the presence of strong genetic effects in cis locations. The identification of protein quantitative trait loci (pQTLs) may be a powerful complementary method of improving our understanding of disease pathways.
Funded by: Intramural NIH HHS; NIA NIH HHS: N01-AG-6-2101, N01-AG-6-2103, N01-AG-6-2106, R01 AG024233, R01 AG24233-01
PLoS genetics 2008;4;5;e1000072
PUBMED: 18464913; PMC: 2362067; DOI: 10.1371/journal.pgen.1000072
Genome-wide association with bone mass and geometry in the Framingham Heart Study.
Hebrew SeniorLife Institute for Aging Research and Harvard Medical School, Boston, MA, USA. email@example.com
Background: Osteoporosis is characterized by low bone mass and compromised bone structure, heritable traits that contribute to fracture risk. There have been no genome-wide association and linkage studies for these traits using high-density genotyping platforms.
Methods: We used the Affymetrix 100K SNP GeneChip marker set in the Framingham Heart Study (FHS) to examine genetic associations with ten primary quantitative traits: bone mineral density (BMD), calcaneal ultrasound, and geometric indices of the hip. To test associations with multivariable-adjusted residual trait values, we used additive generalized estimating equation (GEE) and family-based association tests (FBAT) models within each sex as well as sexes combined. We evaluated 70,987 autosomal SNPs with genotypic call rates > or =80%, HWE p > or = 0.001, and MAF > or =10% in up to 1141 phenotyped individuals (495 men and 646 women, mean age 62.5 yrs). Variance component linkage analysis was performed using 11,200 markers.
Results: Heritability estimates for all bone phenotypes were 30-66%. LOD scores > or =3.0 were found on chromosomes 15 (1.5 LOD confidence interval: 51,336,679-58,934,236 bp) and 22 (35,890,398-48,603,847 bp) for femoral shaft section modulus. The ten primary phenotypes had 12 associations with 100K SNPs in GEE models at p < 0.000001 and 2 associations in FBAT models at p < 0.000001. The 25 most significant p-values for GEE and FBAT were all less than 3.5 x 10(-6) and 2.5 x 10(-5), respectively. Of the 40 top SNPs with the greatest numbers of significantly associated BMD traits (including femoral neck, trochanter, and lumbar spine), one half to two-thirds were in or near genes that have not previously been studied for osteoporosis. Notably, pleiotropic associations between BMD and bone geometric traits were uncommon. Evidence for association (FBAT or GEE p < 0.05) was observed for several SNPs in candidate genes for osteoporosis, such as rs1801133 in MTHFR; rs1884052 and rs3778099 in ESR1; rs4988300 in LRP5; rs2189480 in VDR; rs2075555 in COLIA1; rs10519297 and rs2008691 in CYP19, as well as SNPs in PPARG (rs10510418 and rs2938392) and ANKH (rs2454873 and rs379016). All GEE, FBAT and linkage results are provided as an open-access results resource at http://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007 webcite.
Conclusion: The FHS 100K SNP project offers an unbiased genome-wide strategy to identify new candidate loci and to replicate previously suggested candidate genes for osteoporosis.
Funded by: NCRR NIH HHS: 1S10RR163736-01A1; NHLBI NIH HHS: N01-HC-25195, N01HC25195; NIA NIH HHS: R01 AR/AG 41398; NIAMS NIH HHS: R01 AR041398, R01 AR041398-15, R01 AR050066
BMC medical genetics 2007;8 Suppl 1;S14
Upregulated expression of postsynaptic density-93 and N-methyl-D-aspartate receptors subunits 2B mRNA in temporal lobe tissue of epilepsy.
Department of Neurology, The First Affiliated Hospital, Chongqing Medical University, No. 1You-yi Road, Yu-zhong District, Chongqing 400016, China. email@example.com
Objective: To investigate the expression of PSD-93 mRNA and NR2B mRNA in the brain tissue from the patients with epilepsy so as to explore the possible mechanisms of the pathogenesis of the epilepsy.
Methods: Fifty-six patients with epilepsy were divided into intractable epilepsy (IE) and non-intractable epilepsy (NIE) groups. cDNA microarrays prepared from the brain tissues obtained from these two groups were scanned and comparison to those from the non-epileptogenic control (C) was made. Expression level of PSD-93mRNA and NR2BmRNA were examined by reverse transcription polymerase chain reaction (GAPDH gene, internal control). Expression ratio (target gene/GAPDH) was used to evaluate each gene relative expression level.
Results: The cDNA microarray analysis showed that the expression of PSD-93 mRNA related to the function of NMDAR-NO signal transduction pathway was significantly higher in epilepsy patients than those in the controlled group. The results of RT-PCR were consistent with those of the cDNA microarrays. The relative expression ratio of PSD-93 in patients with non-epileptogenic control, NIE, and IE was 0.159, 0.368, and 0.341, respectively. Correspondingly, that of NR2B was 0.198, 0.738, and 0.903, respectively. The expressions of PSD-93 and NR2B in the NIE and IE were significantly higher than those of control, respectively (P<0.05). However, there was no significantly difference the expression of PSD-93 between NIE and IE. (P>0.05), neither do that of NR2B (P>0.05).
Conclusions: The upregulated expressions of PSD-93 mRNA and NR2BmRNA may be involved in the pathogenesis of epilepsy.
Biochemical and biophysical research communications 2007;358;3;825-30
PUBMED: 17506987; DOI: 10.1016/j.bbrc.2007.05.010
Genome-wide genotyping in Parkinson's disease and neurologically normal controls: first stage analysis and public release of data.
Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
Background: Several genes underlying rare monogenic forms of Parkinson's disease have been identified over the past decade. Despite evidence for a role for genetics in sporadic Parkinson's disease, few common genetic variants have been unequivocally linked to this disorder. We sought to identify any common genetic variability exerting a large effect in risk for Parkinson's disease in a population cohort and to produce publicly available genome-wide genotype data that can be openly mined by interested researchers and readily augmented by genotyping of additional repository subjects.
Methods: We did genome-wide, single-nucleotide-polymorphism (SNP) genotyping of publicly available samples from a cohort of Parkinson's disease patients (n=267) and neurologically normal controls (n=270). More than 408,000 unique SNPs were used from the Illumina Infinium I and HumanHap300 assays.
Findings: We have produced around 220 million genotypes in 537 participants. This raw genotype data has been and as such is the first publicly accessible high-density SNP data outside of the International HapMap Project. We also provide here the results of genotype and allele association tests.
Interpretation: We generated publicly available genotype data for Parkinson's disease patients and controls so that these data can be mined and augmented by other researchers to identify common genetic variability that results in minor and moderate risk for disease.
Funded by: Intramural NIH HHS; Medical Research Council: G0701075
The Lancet. Neurology 2006;5;11;911-6
Uncovering quantitative protein interaction networks for mouse PDZ domains using protein microarrays.
Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
One of the principal challenges in systems biology is to uncover the networks of protein-protein interactions that underlie most biological processes. To date, experimental efforts directed at this problem have largely produced only qualitative networks that are replete with false positives and false negatives. Here, we describe a domain-centered approach--compatible with genome-wide investigations--that enables us to measure the equilibrium dissociation constant (K(D)) of recombinant PDZ domains for fluorescently labeled peptides that represent physiologically relevant binding partners. Using a pilot set of 22 PDZ domains, 4 PDZ domain clusters, and 20 peptides, we define a gold standard dataset by determining the K(D) for all 520 PDZ-peptide combinations using fluorescence polarization. We then show that microarrays of PDZ domains identify interactions of moderate to high affinity (K(D) < or = 10 microM) in a high-throughput format with a false positive rate of 14% and a false negative rate of 14%. By combining the throughput of protein microarrays with the fidelity of fluorescence polarization, our domain/peptide-based strategy yields a quantitative network that faithfully recapitulates 85% of previously reported interactions and uncovers new biophysical interactions, many of which occur between proteins that are co-expressed. From a broader perspective, the selectivity data produced by this effort reveal a strong concordance between protein sequence and protein function, supporting a model in which interaction networks evolve through small steps that do not involve dramatic rewiring of the network.
Funded by: NIGMS NIH HHS: 1 R01 GM072872-01, 5 T32 GM07598-25, R01 GM072872, R01 GM072872-04, T32 GM007598
Journal of the American Chemical Society 2006;128;17;5913-22
PUBMED: 16637659; PMC: 2533859; DOI: 10.1021/ja060943h
Differential expression of a new isoform of DLG2 in renal oncocytoma.
Laboratory of Molecular Oncology, Medical Faculty, Ruprecht-Karls-University, Heidelberg, Germany.
Background: Renal oncocytoma, a benign tumour of the kidney, may pose a differential diagnostic problem due to overlapping phenotype with chromophobe renal cell carcinoma or other types of renal cell tumours. Therefore, identification of molecular markers would be of great value for molecular diagnostics of this tumour type.
Methods: In the current study we applied various techniques, including Affymetrix microarray hybridization and semiquantitative RT-PCR, to identify genes expressed differentially in renal oncocytomas. Subsequently, we used RACE and Northern blot hybridization to characterize the potential candidates for molecular diagnosis.
Results: We have identified new isoform of DLG2 gene, which contains 3'-end exons of the known DLG2 gene along with the hypothetical gene FLJ37266. The new isoform is specifically upregulated in renal oncocytoma, whereas the known DLG2 gene is downregulated in this type of kidney tumour.
Conclusion: The new isoform of DLG2 is the promising candidate gene for molecular differential diagnostics of renal oncocytoma.
BMC cancer 2006;6;106
Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes.
Life Science Research Laboratory, Central Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo, 185-8601, Japan.
By analyzing 1,780,295 5'-end sequences of human full-length cDNAs derived from 164 kinds of oligo-cap cDNA libraries, we identified 269,774 independent positions of transcriptional start sites (TSSs) for 14,628 human RefSeq genes. These TSSs were clustered into 30,964 clusters that were separated from each other by more than 500 bp and thus are very likely to constitute mutually distinct alternative promoters. To our surprise, at least 7674 (52%) human RefSeq genes were subject to regulation by putative alternative promoters (PAPs). On average, there were 3.1 PAPs per gene, with the composition of one CpG-island-containing promoter per 2.6 CpG-less promoters. In 17% of the PAP-containing loci, tissue-specific use of the PAPs was observed. The richest tissue sources of the tissue-specific PAPs were testis and brain. It was also intriguing that the PAP-containing promoters were enriched in the genes encoding signal transduction-related proteins and were rarer in the genes encoding extracellular proteins, possibly reflecting the varied functional requirement for and the restricted expression of those categories of genes, respectively. The patterns of the first exons were highly diverse as well. On average, there were 7.7 different splicing types of first exons per locus partly produced by the PAPs, suggesting that a wide variety of transcripts can be achieved by this mechanism. Our findings suggest that use of alternate promoters and consequent alternative use of first exons should play a pivotal role in generating the complexity required for the highly elaborated molecular systems in humans.
Genome research 2006;16;1;55-65
PUBMED: 16344560; PMC: 1356129; DOI: 10.1101/gr.4039406
Disruption of the phosphatidylserine decarboxylase gene in mice causes embryonic lethality and mitochondrial defects.
Canadian Institutes for Health Research Group on the Molecular and Cell Biology of Lipids and Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
Most of the phosphatidylethanolamine (PE) in mammalian cells is synthesized by two pathways, the CDP-ethanolamine pathway and the phosphatidylserine (PS) decarboxylation pathway, the final steps of which operate at spatially distinct sites, the endoplasmic reticulum and mitochondria, respectively. We investigated the importance of the mitochondrial pathway for PE synthesis in mice by generating mice lacking PS decarboxylase activity. Disruption of Pisd in mice resulted in lethality between days 8 and 10 of embryonic development. Electron microscopy of Pisd-/- embryos revealed large numbers of aberrantly shaped mitochondria. In addition, fluorescence confocal microscopy of Pisd-/- embryonic fibroblasts showed fragmented mitochondria. PS decarboxylase activity and mRNA levels in Pisd+/- tissues were approximately one-half of those in wild-type mice. However, heterozygous mice appeared normal, exhibited normal vitality, and the phospholipid composition of livers, testes, brains, and of mitochondria isolated from livers, was the same as in wild-type littermates. The amount and activity of a key enzyme of the CDP-ethanolamine pathway for PE synthesis, CTP:phosphoethanolamine cytidylyltransferase, were increased by 35-40 and 100%, respectively, in tissues of Pisd+/- mice, as judged by immunoblotting; PE synthesis from [3H]ethanolamine was correspondingly increased in hepatocytes. We conclude that the CDP-ethanolamine pathway in mice cannot substitute for a lack of PS decarboxylase during development. Moreover, elimination of PE production in mitochondria causes fragmented, misshapen mitochondria, an abnormality that likely contributes to the embryonic lethality.
Funded by: NHLBI NIH HHS: HL66600, HL66621, R01 HL094732, R01 HL094732-01, R01 HL094732-01S1, R01 HL094732-02, R01 HL094732-03, U01 HL066600, U01 HL066621
The Journal of biological chemistry 2005;280;48;40032-40
PUBMED: 16192276; PMC: 2888304; DOI: 10.1074/jbc.M506510200
Purification of ATP-binding cassette transporter A1 and associated binding proteins reveals the importance of beta1-syntrophin in cholesterol efflux.
Lipid Metabolism Unit, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
ATP-binding cassette transporter A1 (ABCA1) plays a critical role in HDL cholesterol metabolism, but the mechanism by which it transports lipid across membranes is poorly understood. Because growing evidence implicates accessory proteins in this process, we developed a method by which proteins interacting with the intact transporter could be identified. cDNAs encoding wild-type ABCA1 and a mutant lacking the C-terminal PDZ binding motif of ABCA1 were transfected into 293 cells, and the expressed proteins were solubilized using detergent conditions (0.75% CHAPS, 1 mg/ml phosphatidylcholine) predicted to retain high affinity protein-protein interactions. Proteins that co-purified with ABCA1 on an antibody affinity column were identified by liquid chromatographymass spectrometric analysis. A novel interaction with the PDZ protein beta1-syntrophin was identified using this approach, and this interaction was confirmed in human THP-1 macrophages and in mouse liver. Small interference RNA inhibition of beta1-syntrophin expression reduced cholesterol efflux from primary skin fibroblasts by 50% while decreasing efflux 30% in bone marrow-derived macrophages. Inhibition of beta1-syntrophin decreased ABCA1 protein levels, whereas overexpression of beta1-syntrophin increased ABCA1 cell-surface expression and stimulated efflux to apolipoprotein A-I. These findings indicate that beta1-syntrophin acts through a class-I PDZ interaction with the C terminus of ABCA1 to regulate the cellular distribution and activity of the transporter. The approach used to identify beta1-syntrophin as an ABCA1-binding protein should prove useful in elucidating other protein interactions upon which ABCA1 function depends.
Funded by: NHLBI NIH HHS: HL074136, HL45098, HL68988, HL72358
The Journal of biological chemistry 2005;280;47;39653-64
PUBMED: 16192269; DOI: 10.1074/jbc.M510187200
An alternatively spliced isoform of PSD-93/chapsyn 110 binds to the inwardly rectifying potassium channel, Kir2.1.
Department of Biochemistry, University of Leicester, PO Box 138, LE1 9HN, UK. firstname.lastname@example.com
Inwardly rectifying potassium (Kir) channels are prime determinants of resting membrane potential in neurons. Their subcellular distribution and surface density thus help shape neuronal excitability, yet mechanisms governing the membrane targeting and localization of Kir channels are poorly understood. Here we report a direct interaction between the strong inward rectifier, Kir2.1, and a recently identified splice variant of postsynaptic density-93 (PSD-93), a protein involved the subcellular targeting of ion channels and glutamate receptors at excitatory synapses. Yeast two-hybrid screening of a human brain cDNA library using the carboxyl terminus of Kir2.1 as bait yielded cDNA encoding the first two PDZ domains of PSD-93, but with an extended N-terminal region that diverged from other PSD-93 isoforms. This clone represented the human homologue of the mouse PSD-93 splice variant, PSD-93delta. Reverse transcription-polymerase chain reaction analysis showed diffuse low level PSD-93delta expression throughout the brain, with significantly higher levels in spinal cord. In vitro binding studies revealed that a type I PDZ recognition motif at the extreme C terminus of the Kir2.1 mediates interaction with all three PDZ domains of PSD-93delta, and association between Kir2 channels and PSD-93delta was confirmed further by the ability of anti-Kir2.1 antibodies to coimmunoprecipitate PSD-93delta from rat spinal cord lysates. Functionally, coexpression of Kir2.1 and PSD-93delta had no discernible effect upon channel kinetics but resulted in cell surface Kir2.1 clustering and suppression of channel internalization. We conclude that PSD-93delta is potentially an important regulator of the spatial and temporal distribution of Kir2 channels within neuronal membranes of the central nervous system.
The Journal of biological chemistry 2004;279;42;43427-36
PUBMED: 15304517; DOI: 10.1074/jbc.M407575200
Protein trafficking and anchoring complexes revealed by proteomic analysis of inward rectifier potassium channel (Kir2.x)-associated proteins.
Department of Molecular, Cellular, University of California, Santa Barbara, California 93106, USA.
Inward rectifier potassium (Kir) channels play important roles in the maintenance and control of cell excitability. Both intracellular trafficking and modulation of Kir channel activity are regulated by protein-protein interactions. We adopted a proteomics approach to identify proteins associated with Kir2 channels via the channel C-terminal PDZ binding motif. Detergent-solubilized rat brain and heart extracts were subjected to affinity chromatography using a Kir2.2 C-terminal matrix to purify channel-interacting proteins. Proteins were identified with multidimensional high pressure liquid chromatography coupled with electrospray ionization tandem mass spectrometry, N-terminal microsequencing, and immunoblotting with specific antibodies. We identified eight members of the MAGUK family of proteins (SAP97, PSD-95, Chapsyn-110, SAP102, CASK, Dlg2, Dlg3, and Pals2), two isoforms of Veli (Veli-1 and Veli-3), Mint1, and actin-binding LIM protein (abLIM) as Kir2.2-associated brain proteins. From heart extract purifications, SAP97, CASK, Veli-3, and Mint1 also were found to associate with Kir2 channels. Furthermore, we demonstrate for the first time that components of the dystrophin-associated protein complex, including alpha1-, beta1-, and beta2-syntrophin, dystrophin, and dystrobrevin, interact with Kir2 channels, as demonstrated by immunoaffinity purification and affinity chromatography from skeletal and cardiac muscle and brain. Affinity pull-down experiments revealed that Kir2.1, Kir2.2, Kir2.3, and Kir4.1 all bind to scaffolding proteins but with different affinities for the dystrophin-associated protein complex and SAP97, CASK, and Veli. Immunofluorescent localization studies demonstrated that Kir2.2 co-localizes with syntrophin, dystrophin, and dystrobrevin at skeletal muscle neuromuscular junctions. These results suggest that Kir2 channels associate with protein complexes that may be important to target and traffic channels to specific subcellular locations, as well as anchor and stabilize channels in the plasma membrane.
Funded by: NINDS NIH HHS: NS33145, NS43377
The Journal of biological chemistry 2004;279;21;22331-46
PUBMED: 15024025; DOI: 10.1074/jbc.M400285200
Complete sequencing and characterization of 21,243 full-length human cDNAs.
Helix Research Institute, 1532-3 Yana, Kisarazu, Chiba 292-0812, Japan.
As a base for human transcriptome and functional genomics, we created the "full-length long Japan" (FLJ) collection of sequenced human cDNAs. We determined the entire sequence of 21,243 selected clones and found that 14,490 cDNAs (10,897 clusters) were unique to the FLJ collection. About half of them (5,416) seemed to be protein-coding. Of those, 1,999 clusters had not been predicted by computational methods. The distribution of GC content of nonpredicted cDNAs had a peak at approximately 58% compared with a peak at approximately 42%for predicted cDNAs. Thus, there seems to be a slight bias against GC-rich transcripts in current gene prediction procedures. The rest of the cDNAs unique to the FLJ collection (5,481) contained no obvious open reading frames (ORFs) and thus are candidate noncoding RNAs. About one-fourth of them (1,378) showed a clear pattern of splicing. The distribution of GC content of noncoding cDNAs was narrow and had a peak at approximately 42%, relatively low compared with that of protein-coding cDNAs.
Nature genetics 2004;36;1;40-5
PUBMED: 14702039; DOI: 10.1038/ng1285
Impaired NMDA receptor-mediated postsynaptic function and blunted NMDA receptor-dependent persistent pain in mice lacking postsynaptic density-93 protein.
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA. firstname.lastname@example.com
Modification of synaptic NMDA receptor (NMDAR) expression influences NMDAR-mediated synaptic function and associated persistent pain. NMDARs directly bind to a family of membrane-associated guanylate kinases (MAGUKs) that regulate surface and synaptic NMDAR trafficking in the CNS. We report here that postsynaptic density-93 protein (PSD-93), a postsynaptic neuronal MAGUK, is expressed abundantly in spinal dorsal horn and forebrain, where it colocalizes and interacts with NMDAR subunits NR2A and NR2B. Targeted disruption of the PSD-93 gene reduces not only surface NR2A and NR2B expression but also NMDAR-mediated excitatory postsynaptic currents and potentials, without affecting surface AMPA receptor expression or its synaptic function, in the regions mentioned above. Furthermore, mice lacking PSD-93 exhibit blunted NMDAR-dependent persistent pain induced by peripheral nerve injury or injection of Complete Freund's Adjuvant, although they display intact nociceptive responsiveness to acute pain. PSD-93 appears to be important for NMDAR synaptic targeting and function and to be a potential biochemical target for the treatment of persistent pain.
Funded by: NIGMS NIH HHS: R01 GM 49111; NINDS NIH HHS: NS 44219, NS360017; PHS HHS: 10833, 38680
The Journal of neuroscience : the official journal of the Society for Neuroscience 2003;23;17;6703-12
Selective interaction of megalin with postsynaptic density-95 (PSD-95)-like membrane-associated guanylate kinase (MAGUK) proteins.
Department of Medical Biochemistry and Microbiology, Uppsala University, PO Box 582, SE-751 23 Uppsala, Sweden. firstname.lastname@example.com
Megalin is an integral membrane receptor belonging to the low-density lipoprotein receptor family. In addition to its role as an endocytotic receptor, megalin has also been proposed to have signalling functions. Using interaction cloning in yeast, we identified the membrane-associated guanylate kinase family member postsynaptic density-95 (PSD-95) as an interaction partner for megalin. PSD-95 and a truncated version of megalin were co-immunoprecipitated from HEK-293 cell lysates overexpressing the two proteins, which confirmed the interaction. The two proteins were found to be co-localized in these cells by confocal microscopy. Immunocytochemical studies showed that cells in the parathyroid, proximal tubuli of the kidney and placenta express both megalin and PSD-95. We found that the interaction between the two proteins is mediated by the binding of the C-terminus of megalin, which has a type I PSD-95/ Drosophila discs-large/zona occludens 1 (PDZ)-binding motif, to the PDZ2 domain of PSD-95. The PSD-95-like membrane-associated guanylate kinase ('MAGUK') family contains three additional members: PSD-93, synapse-associated protein 97 (SAP97) and SAP102. We detected these proteins, apart from SAP102, in parathyroid chief cells, a cell type having a marked expression of megalin. The PDZ2 domains of PSD-93 and SAP102 were also shown to interact with megalin, whereas no interaction was detected for SAP97. The SAP97 PDZ2 domain differed at four positions from the other members of the PSD-95 subfamily. One of these residues was Thr(389), located in the alphaB-helix and part of the hydrophobic pocket of the PDZ2 domain. Surface plasmon resonance experiments revealed that mutation of SAP97 Thr(389) to alanine, as with the other PSD-95-like membrane-associated guanylate kinases, induced binding to megalin.
The Biochemical journal 2003;373;Pt 2;381-91
Expression, regulation and role of the MAGUK protein SAP-97 in human atrial myocardium.
INSERM Unité 460, Faculté de Médecine Xavier Bichat, 16 rue Henri Huchard, 75018, Paris, France.
Objective: In various cell types, membrane-associated guanylate kinases proteins called MAGUK play a major role in the spatial localization and clustering of ion channels. Here, we studied the expression and role of these anchoring proteins in human right atrial myocardium by means of various molecular, biochemical and physiological methods.
SAP-97, PSD-95, Chapsyn and SAP-102 messengers were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) on mRNA extracted from both whole myocardium and isolated myocytes. Western blot revealed that the MAGUK protein SAP-97 and, to a lesser extent, PSD-95, is abundantly expressed in human atrial myocardium, while Chapsyn are almost undetectable. Confocal microscopic visualization of cryosection of atrial myocardium stained with the anti-PSD-95 family antibody showed positive staining at the plasma membrane level and cell extremity. Calpain-I cleaved both SAP-97 and PSD-95 proteins, resulting in an accumulation of short bands, including an 80-kDa band that was also detected in the cytosolic protein fraction. Immunoprecipitation of SAP-97 co-precipitated hKv1.5 channels, and vice versa. Co-expression of cloned SAP-97 and hKv1.5 channels in Chinese hamster ovarian (CHO) cells increased the K(+) current (157.00+/-19.45 pA/pF vs. 344.50+/-58.58 pA/pF at +50 mV).
Conclusions: The protein SAP-97 is abundantly expressed in human atrial myocardium in association with hKv1.5 channels, and probably contributes to regulating the functional expression of the latter.
Cardiovascular research 2002;56;3;433-42
PUBMED: 12445884; DOI: 10.1016/s0008-6363(02)00602-8
Identification of multiple binding partners for the amino-terminal domain of synapse-associated protein 97.
Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
Multiprotein complexes mediate static and dynamic functions to establish and maintain cell polarity in both epithelial cells and neurons. Membrane-associated guanylate kinase (MAGUK) proteins are thought to be scaffolding molecules in these processes and bind multiple proteins via their obligate postsynaptic density (PSD)-95/Disc Large/Zona Occludens-1, Src homology 3, and guanylate kinase-like domains. Subsets of MAGUK proteins have additional protein-protein interaction domains. An additional domain we identified in SAP97 called the MAGUK recruitment (MRE) domain binds the LIN-2,7 amino-terminal (L27N) domain of mLIN-2/CASK, a MAGUK known to bind mLIN-7. Here we show that SAP97 binds two other mLIN-7 binding MAGUK proteins. One of these MAGUK proteins, DLG3, coimmunoprecipitates with SAP97 in lysates from rat brain and transfected Madin-Darby canine kidney cells. This interaction requires the MRE domain of SAP97 and surprisingly, both the L27N and L27 carboxyl-terminal (L27C) domains of DLG3. We also demonstrate that SAP97 can interact with the MAGUK protein, DLG2, but not the highly related protein, PALS2. The ability of SAP97 to interact with multiple MAGUK proteins is likely to be important for the targeting of specific protein complexes in polarized cells.
Funded by: NIDDK NIH HHS: 2-P50-DK39255; NIGMS NIH HHS: 5-T32-GM07544, GM08353
The Journal of biological chemistry 2002;277;48;46730-5
PUBMED: 12351654; DOI: 10.1074/jbc.M208781200
Selective reduction of a PDZ protein, SAP-97, in the prefrontal cortex of patients with chronic schizophrenia.
Molecular Neurobiology, Brain Research Institute, Niigata University, Japan.
Many postsynaptic density proteins carrying postsynaptic density-95/discs large/zone occludens-1 (PDZ) domain(s) interact with glutamate receptors to control receptor dynamics and synaptic plasticity. Here we examined the expression of PDZ proteins, synapse-associated protein (SAP) 97, postsynaptic density (PSD)-95, chapsyn-110, GRIP1 and SAP102, in post-mortem brains of schizophrenic patients and control subjects, and evaluated their contribution to schizophrenic pathology. Among these PDZ proteins, SAP97 exhibited the most marked change: SAP97 protein levels were decreased to less than half that of the control levels specifically in the prefrontal cortex of schizophrenic patients. In parallel, its binding partner, GluR1, similarly decreased in the same brain region. The correlation between SAP97 and GluR1 levels in control subjects was, however, altered in schizophrenic patients. SAP102 levels were also significantly reduced in the hippocampus of schizophrenic patients, but this reduction was correlated with sample storage time and post-mortem interval. There were no changes in the levels of the other PDZ proteins in any of the regions examined. In addition, neuroleptic treatment failed to mimic the SAP97 change. These findings suggest that a phenotypic loss of SAP97 is associated with the postsynaptic impairment in prefrontal excitatory circuits of schizophrenic patients.
Journal of neurochemistry 2002;83;4;797-806
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.
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
PUBMED: 12070168; DOI: 10.1074/jbc.M204354200
Direct interaction of Frizzled-1, -2, -4, and -7 with PDZ domains of PSD-95.
Center for Learning and Memory, Howard Hughes Medical Institute, RIKEN-MIT Neuroscience Research Center, and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue (E18-215), Cambridge, MA 02139, USA.
In Drosophila, the frizzled gene plays a critical role in the establishment of tissue polarity, but the function of the Frizzled family of proteins in mammals is largely unknown. Recent evidence suggested that Frizzleds are receptors for the Wnt family of secreted glycoproteins which are involved in cell fate determination. However, it is unclear how Frizzled receptors transduce Wnt signals to intracellular signaling components. Here we show that the mouse Frizzled-1, -2, -4 and -7 can bind to proteins of the PSD-95 family, which are implicated in the assembly and localization of multiprotein signaling complexes in the brain. Moreover, PSD-95 can form a ternary complex with Frizzled-2 and the adenomatous polyposis coli protein, a negative regulator of Wnt signaling, suggesting that members of the PSD-95 family may serve to recruit intracellular signaling molecules of the Wnt/Frizzled pathway into the vicinity of the receptor.
FEBS letters 2002;521;1-3;185-9
Inward rectifier K+ channel Kir2.3 is localized at the postsynaptic membrane of excitatory synapses.
Department of Pharmacology II, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan.
Classical inwardly rectifying K+ channels (Kir2.0) are responsible for maintaining the resting membrane potential near the K+ equilibrium potential in various cells, including neurons. Although Kir2.3 is known to be expressed abundantly in the forebrain, its precise localization has not been identified. Using an antibody specific to Kir2.3, we examined the subcellular localization of Kir2.3 in mouse brain. Kir2.3 immunoreactivity was detected in a granular pattern in restricted areas of the brain, including the olfactory bulb (OB). Immunoelectron microscopy of the OB revealed that Kir2.3 immunoreactivity was specifically clustered on the postsynaptic membrane of asymmetric synapses between granule cells and mitral/tufted cells. The immunoprecipitants for Kir2.3 obtained from brain contained PSD-95 and chapsyn-110, PDZ domain-containing anchoring proteins. In vitro binding assay further revealed that the COOH-terminal end of Kir2.3 is responsible for the association with these anchoring proteins. Therefore, the Kir channel may be involved in formation of the resting membrane potential of the spines and, thus, would affect the response of N-methyl-D-aspartic acid receptor channels at the excitatory postsynaptic membrane.
American journal of physiology. Cell physiology 2002;282;6;C1396-403
PUBMED: 11997254; DOI: 10.1152/ajpcell.00615.2001
Guanylyl cyclase/PSD-95 interaction: targeting of the nitric oxide-sensitive alpha2beta1 guanylyl cyclase to synaptic membranes.
Pharmakologie und Toxikologie, Medizinische Fakultät MA N1, Ruhr-Universität Bochum, 44780 Bochum, Germany.
The signaling molecule nitric oxide (NO) exerts most of its effects by the stimulation of the NO-sensitive guanylyl cyclase. Two isoforms of the NO receptor molecule exist: the ubiquitously occurring alpha(1)beta(1) and the alpha(2)beta(1) with a more limited distribution. As the isoforms are functionally indistinguishable, the physiological relevance of these isoforms remained unclear. The neuronal NO synthase has been reported to be associated with PSD-95. Here, we demonstrate the interaction of the so far unnoticed alpha(2)beta(1) isoform with PSD-95 in rat brain as shown by coprecipitation. The interaction is mediated by the alpha(2) C-terminal peptide and the third PDZ domain of PSD-95. As a consequence of the PSD-95 interaction, the so far considered "soluble" alpha(2)beta(1) isoform is recruited to the membrane fraction of synaptosomes, whereas the alpha(1)beta(1) isoform is found in the cytosol. Our results establish the alpha(1)beta(1) as the cytosolic and the alpha(2)beta(1) as the membrane-associated NO-sensitive guanylyl cyclase and suggest the alpha(2)beta(1) isoform as the sensor for the NO formed by the PSD-95-associated neuronal NO synthase.
The Journal of biological chemistry 2001;276;48;44647-52
PUBMED: 11572861; DOI: 10.1074/jbc.M105587200
Plasma membrane Ca2+-atpase isoforms 2b and 4b interact promiscuously and selectively with members of the membrane-associated guanylate kinase family of PDZ (PSD95/Dlg/ZO-1) domain-containing proteins.
Program in Molecular Neuroscience, Department of Biochemistry, Mayo Graduate School, Mayo Clinic, Rochester, Minnesota 55905, USA.
Spatial and temporal regulation of intracellular Ca(2+) signaling depends on localized Ca(2+) microdomains containing the requisite molecular components for Ca(2+) influx, efflux, and signal transmission. Plasma membrane Ca(2+)-ATPase (PMCA) isoforms of the "b" splice type contain predicted PDZ (PSD95/Dlg/ZO-1) interaction domains. The COOH-terminal tail of PMCA2b isolated the membrane-associated guanylate kinase (MAGUK) protein SAP97/hDlg as a binding partner in a yeast two-hybrid screen. The related MAGUKs SAP90/PSD95, PSD93/chapsyn-110, SAP97, and SAP102 all bound to the COOH-terminal tail of PMCA4b, whereas only the first three bound to the tail of PMCA2b. Coimmunoprecipitations confirmed the interaction selectivity between PMCA4b and SAP102 as opposed to the promiscuity of PMCA2b and 4b in interacting with other SAPs. Confocal immunofluorescence microscopy revealed the exclusive presence and colocalization of PMCA4b and SAP97 in the basolateral membrane of polarized Madin-Darby canine kidney epithelial cells. In hippocampal neurons, PMCA2b was abundant throughout the somatodendritic compartment and often extended into the neck and head of individual spines where it colocalized with SAP90/PSD95. These data show that PMCA "b" splice forms interact promiscuously but also with specificity with different members of the PSD95 family of SAPs. PMCA-SAP interactions may play a role in the recruitment and maintenance of the PMCA at specific membrane domains involved in local Ca(2+) regulation.
Funded by: NIGMS NIH HHS: GM-58710
The Journal of biological chemistry 2001;276;24;21594-600
PUBMED: 11274188; DOI: 10.1074/jbc.M101448200
Sema4c, a transmembrane semaphorin, interacts with a post-synaptic density protein, PSD-95.
Group of Neurobiology, School of Allied Health Sciences, Osaka University Faculty of Medicine, Yamadaoka 1-7, Suita-shi, Osaka, 565-0871, Japan. email@example.com
Semaphorins are known to act as chemorepulsive molecules that guide axons during neural development. Sema4C, a group 4 semaphorin, is a transmembrane semaphorin of unknown function. The cytoplasmic domain of Sema4C contains a proline-rich region that may interact with some signaling proteins. In this study, we demonstrate that Sema4C is enriched in the adult mouse brain and associated with PSD-95 isoforms containing PDZ (PSD-95/DLG/ZO-1) domains, such as PSD-95/SAP90, PSD-93/chapsin110, and SAP97/DLG-1, which are concentrated in the post-synaptic density of the brain. In the neocortex, S4C is enriched in the synaptic vesicle fraction and Triton X-100 insoluble post-synaptic density fraction. Immunostaining for Sema4C overlaps that for PSD-95 in superficial layers I-IV of the neocortex. In neocortical culture, S4C is colocalized with PSD-95 in neurons, with a dot-like pattern along the neurites. Sema4C thus may function in the cortical neurons as a bi-directional transmembrane ligand through interacting with PSD-95.
The Journal of biological chemistry 2001;276;12;9174-81
PUBMED: 11134026; DOI: 10.1074/jbc.M009051200
Fetal life in Down syndrome starts with normal neuronal density but impaired dendritic spines and synaptosomal structure.
Department of Pediatrics, University of Vienna, Austria.
Information on fetal brain in Down Syndrome (DS) is limited and there are only few histological, mainly anecdotal reports and no systematic study on the wiring of the brain in early prenatal life exists. Histological methods are also hampered by inherent problems of morphometry of neuronal structures. It was therefore the aim of the study to evaluate neuronal loss, synaptic structures and dendritic spines in the fetus with Down Syndrome as compared to controls by biochemical measurements. 2 dimensional electrophoresis with subsequent mass spectroscopical identification of spots and their quantification with specific software was selected. This technique identifies proteins unambiguously and concomitantly on the same gel. Fetal cortex samples were taken at autopsy with low post-mortem time, homogenized and neuron specific enolase (NSE) determined as a marker for neuronal density, the synaptosomal associated proteins alpha SNAP [soluble N-ethylmaleimide-sensitive fusion (NSF) attachment protein], beta SNAP, SNAP 25 and the channel associated protein of synapse 110 (chapsyn 110) as markers for synaptosomal structures and drebrin (DRB) as marker for dendritic spines. NSE, chapsyn 110 and beta SNAP were comparable in the control fetus panel and in Down Syndrome fetuses. Drebrin was significantly and remarkably reduced and not even detectable in several Down Syndrome brain samples. Quantification of SNAP 25 revealed significantly reduced values in DS cortex and alpha SNAP was only present in half of the DS individuals. We conclude that at the time point of about 19 weeks of gestation (early second trimester) no neuronal loss can be detected but drebrin, a marker for dendritic spines and synaptosomal associated proteins alpha SNAP and SNAP 25 were significantly reduced indicating impaired synaptogenesis. Early dendritic deterioration maybe leading to the degeneration of the dendritic tree and arborization, which is a hallmark of Down Syndrome from infancy.
Journal of neural transmission. Supplementum 2001;61;59-70
Postsynaptic targeting of MAGUKs mediated by distinct N-terminal domains.
Department of Physiology, University of California at San Francisco, 94143-0444, USA.
Postsynaptic targeting of PSD-95 has been extensively studied; however, little is known about how other MAGUKs are localized. Proper targeting of PSD-95 requires dual palmitoylation of an N-terminal motif. We now find that the N-termini of closely related PSD-93 and SAP-102 are also involved in postsynaptic targeting. PSD-93 is N-terminally palmitoylated; however, unlike PSD-95, palmitoylation does not explain the necessity of the N-terminus for PSD-93 postsynaptic targeting. Furthermore, when the N-terminus of PSD-95 is replaced with the first 30 or 64, but not the first 10, amino acids of PSD-93, the chimera is targeted to postsynaptic sites independent of palmitoylation. Similarly, when the N-terminus of PSD-95 is replaced with the non-palmitoylated N-terminus of SAP-102, postsynaptic targeting is maintained. These results suggest that MAGUKs contain diverse signals within their N-termini for postsynaptic targeting.
Funded by: NINDS NIH HHS: R01-NS36017
Neuroreport 2000;11;16;3479-84
The hDLG-associated protein DAP interacts with dynein light chain and neuronal nitric oxide synthase.
Laboratory of Molecular and Genetic Information, Institute for Molecular and Cellular Biosciences, The University of Tokyo, Japan.
Background: Postsynaptic density (PSD)-95 interacts with and mediates clustering of the N-methyl-D-aspartate-receptors (NMDA-R). PSD-95 also interacts with the hDLG-associated protein DAP, which is also called Synapse-associated protein 90-associated protein (SAPAP), and Guanylate kinase-associated protein (GKAP).
Results: DAP interacted directly with the dynein light chain (DLC) family of proteins. DLC was contained in the NMDA-R-PSD-95-DAP-neuronal nitric oxide synthase (nNOS) complex. Furthermore, DAP interacted with nNOS and recruited it into the Triton X-100-insoluble fraction of transfected cells.
Conclusion: DAP interacts directly with DLC and nNOS, and links these proteins to the NMDA-R-PSD-95 complex.
Genes to cells : devoted to molecular & cellular mechanisms 2000;5;11;905-911
Proteomic analysis of NMDA receptor-adhesion protein signaling complexes.
Centre for Genome Research, Centre for Neuroscience, University of Edinburgh, West Mains Road, Edinburgh EH9 3JQ, UK.
N-methyl-d-aspartate receptors (NMDAR) mediate long-lasting changes in synapse strength via downstream signaling pathways. We report proteomic characterization with mass spectrometry and immunoblotting of NMDAR multiprotein complexes (NRC) isolated from mouse brain. The NRC comprised 77 proteins organized into receptor, adaptor, signaling, cytoskeletal and novel proteins, of which 30 are implicated from binding studies and another 19 participate in NMDAR signaling. NMDAR and metabotropic glutamate receptor subtypes were linked to cadherins and L1 cell-adhesion molecules in complexes lacking AMPA receptors. These neurotransmitter-adhesion receptor complexes were bound to kinases, phosphatases, GTPase-activating proteins and Ras with effectors including MAPK pathway components. Several proteins were encoded by activity-dependent genes. Genetic or pharmacological interference with 15 NRC proteins impairs learning and with 22 proteins alters synaptic plasticity in rodents. Mutations in three human genes (NF1, Rsk-2, L1) are associated with learning impairments, indicating the NRC also participates in human cognition.
Nature neuroscience 2000;3;7;661-9
Interaction of the postsynaptic density-95/guanylate kinase domain-associated protein complex with a light chain of myosin-V and dynein.
Howard Hughes Medical Institute, Department of Neurobiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
NMDA receptors interact directly with postsynaptic density-95 (PSD-95), a scaffold protein that organizes a cytoskeletal- signaling complex at the postsynaptic membrane. The molecular mechanism by which the PSD-95-based protein complex is trafficked to the postsynaptic site is unknown but presumably involves specific motor proteins. Here we demonstrate a direct interaction between the PSD-95-associated protein guanylate kinase domain-associated protein (GKAP) and dynein light chain (DLC), a light chain subunit shared by myosin-V (an actin-based motor) and cytoplasmic dynein (a microtubule-based motor). A yeast two-hybrid screen with GKAP isolated DLC2, a novel protein 93% identical to the previously cloned 8 kDa dynein light chain (DLC1). A complex containing PSD-95, GKAP, DLC, and myosin-V can be immunoprecipitated from rat brain extracts. DLC colocalizes with PSD-95 and F-actin in dendritic spines of cultured neurons and is enriched in biochemical purifications of PSD. Immunogold electron microscopy reveals a concentration of DLC in the postsynaptic compartment of asymmetric synapses of brain in which it is associated with the PSD and the spine apparatus. We discuss the possibility that the GKAP/DLC interaction may be involved in trafficking of the PSD-95 complex by motor proteins.
Funded by: NINDS NIH HHS: NS29879, NS33184, NS35050
The Journal of neuroscience : the official journal of the Society for Neuroscience 2000;20;12;4524-34
The neuregulin receptor ErbB-4 interacts with PDZ-containing proteins at neuronal synapses.
Unit on Molecular Neurobiology, National Institutes of Health, Bethesda, MD 20892, USA.
Neuregulins regulate the expression of ligand- and voltage-gated channels in neurons and skeletal muscle by the activation of their cognate tyrosine kinase receptors, ErbB 1-4. The subcellular distribution and mechanisms that regulate the localization of ErbB receptors are unknown. We have found that ErbB receptors are present in brain subcellular fractions enriched for postsynaptic densities (PSD). The ErbB-4 receptor is unique among the ErbB proteins because its C-terminal tail (T-V-V) conforms to a sequence that binds to a protein motif known as the PDZ domain. Using the yeast two-hybrid system, we found that the C-terminal region of ErbB-4 interacts with the three related membrane-associated guanylate kinases (MAGUKs) PSD-95/SAP90, PSD-93/chapsyn-110, and SAP 102, which harbor three PDZ domains, as well as with beta(2)-syntrophin, which has a single PDZ domain. As with N-methyl-D-aspartate (NMDA) receptors, ErbB4 interacts with the first two PDZ domains of PSD-95. Using coimmunoprecipitation assays, we confirmed the direct interactions between ErbB-4 and PSD-95 in transfected heterologous cells, as well as in vivo, where both proteins are coimmunoprecipitated from brain lysates. Moreover, evidence for colocalization of these proteins was also observed by immunofluorescence in cultured hippocampal neurons. ErbB-4 colocalizes with PSD-95 and NMDA receptors at a subset of excitatory synapses apposed to synaptophysin-positive presynaptic terminals. The capacity of ErbB receptors to interact with PDZ-domain proteins at cell junctions is conserved from invertebrates to mammals. As discussed, the interactions found between receptor tyrosine kinases and MAGUKs at neuronal synapses may have important implications for activity-dependent plasticity.
Proceedings of the National Academy of Sciences of the United States of America 2000;97;7;3596-601
PUBMED: 10725395; PMC: 16285; DOI: 10.1073/pnas.070042497
A developmental change in NMDA receptor-associated proteins at hippocampal synapses.
Laboratory of Neurochemistry, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, USA. email@example.com
The membrane-associated guanylate kinases [Chapsyn-110/postsynaptic density-93 (PSD-93), synapse-associated protein-90 (SAP-90)/PSD-95, and SAP-102] are believed to cluster and anchor NMDA receptors at the synapse and to play a role in signal transduction. We have investigated the developmental changes in expression of these proteins in rat hippocampus using biochemical analyses and quantitative immunogold electron microscopy. At postnatal day 2 (P2), SAP-102 was highly expressed, whereas PSD-93 and PSD-95 were low. SAP-102 expression increased during the first week, stayed stable through P35, and showed a reduced expression at 6 months. From P2 through 6 months, PSD-93 and PSD-95 increased. For PSD-95, the percent of labeled synapses increased almost threefold with age, whereas the number of gold particles per labeled synapse did not change significantly, suggesting that the increase in PSD-95 is attributable primarily to an increase in the number of synapses containing PSD-95. In contrast, for SAP-102, both percent labeled synapses and the number of gold particles per labeled synapse decreased during this time. From Western blots of hippocampus and immunogold analysis of CA1 synapses, the high expression of NR2B at P2 coincides with the high level of SAP-102 at synapses, whereas the later expression of NR2A coincides with that of PSD-93 and PSD-95. To determine whether the changes in PSD-93/95 and SAP-102 reflect preferred associations with NR2A and NR2B, respectively, we measured co-immunoprecipitation in the adult hippocampus. These studies suggest that there is a preference for complexes of NR2A/PSD-93/95 and NR2B/SAP-102. These results indicate that individual receptor-associated proteins may have specific functions that are critical to synapse development.
Funded by: NINDS NIH HHS: NS 35563
The Journal of neuroscience : the official journal of the Society for Neuroscience 2000;20;3;1260-71
Postsynaptic density-93 interacts with the delta2 glutamate receptor subunit at parallel fiber synapses.
Laboratory of Neurochemistry, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, USA. firstname.lastname@example.com
The glutamate receptor subunit delta2 has a unique distribution at the parallel fiber-Purkinje cell synapse of the cerebellum, which is developmentally regulated such that delta2 occurs at both parallel fiber synapses and climbing fiber synapses early in development but is restricted to parallel fiber synapses in adult animals. To identify proteins that might be involved in the trafficking or docking of delta2 receptors, we screened a yeast two-hybrid library with the cytosolic C terminus of delta2 and isolated a member of the postsynaptic density (PSD)-95 family of proteins, which are known to interact with the extreme C termini of NMDA receptors. We find that delta2 binds specifically to PSD-93, which is enriched in Purkinje cells. In addition, PSD-93 clusters delta2 when they are coexpressed in heterologous cells, and clustering is disrupted by point mutations of delta2 that disrupt the delta2-PSD-93 interaction. Ultrastructural localization of PSD-93 and delta2 shows they are colocalized at parallel fiber synapses; however, PSD-93 also is present at climbing fiber synapses of the adult rat, where delta2 is not found, indicating that the presence of PSD-93 alone is not sufficient for determining the synaptic expression of delta2.
Funded by: NIGMS NIH HHS: GM36017
The Journal of neuroscience : the official journal of the Society for Neuroscience 1999;19;10;3926-34
Synaptic targeting of the postsynaptic density protein PSD-95 mediated by lipid and protein motifs.
Department of Physiology and Program in Neuroscience, University of California, San Francisco 94143-0444, USA.
During synaptic development, proteins aggregate at specialized pre- and postsynaptic structures. Mechanisms that mediate protein clustering at these sites remain unknown. To investigate this process, we analyzed synaptic targeting of a postsynaptic density protein, PSD-95, by expressing green fluorescent protein- (GFP-) tagged PSD-95 in cultured hippocampal neurons. We find that postsynaptic clustering relies on three elements of PSD-95: N-terminal palmitoylation, the first two PDZ domains, and a C-terminal targeting motif. In contrast, disruptions of PDZ3, SH3, or guanylate kinase (GK) domains do not affect synaptic targeting. Palmitoylation is sufficient to target the diffusely expressed SAP-97 to synapses, and palmitoylation cannot be replaced with alternative membrane association motifs, suggesting that a specialized synaptic lipid environment mediates postsynaptic clustering. The requirements for PDZ domains and a C-terminal domain of PSD-95 indicate that protein-protein interactions cooperate with lipid interactions in synaptic targeting.
Neuron 1999;22;3;497-509
Fine-scale physical map of the 11q21 region surrounding the human DLG2 locus, the gene encoding Chapsyn-110.
Developmental Biology Center, University of California, Irvine, 4340 Biological Sciences II, Irvine, California, 92697-2275, USA. email@example.com
Funded by: NCI NIH HHS: P01 CA66263, P30 CA62203
Genomics 1998;54;1;186-8
PUBMED: 9806853; DOI: 10.1006/geno.1998.5527
Localization of postsynaptic density-93 to dendritic microtubules and interaction with microtubule-associated protein 1A.
Department of Physiology, University of California at San Francisco, San Francisco, California 94143-0444, USA.
Postsynaptic density-93 (PSD-93)/Chapsyn-110 is a member of the membrane-associated guanylate kinase (MAGUK) family of PDZ domain-containing proteins. MAGUKs are widely expressed in the brain and are critical elements of the cytoskeleton and of certain synapses. In the ultrastructural studies that are described here, PSD-93 localizes to both postsynaptic densities and dendritic microtubules of cerebellar Purkinje neurons. The microtubule localization is paralleled by a high-affinity in vivo interaction of PSD-93 via its guanylate kinase (GK) domain with microtubule-associated protein 1A (MAP1A). GK domain truncations that mimic genetically identified mutations of a Drosophila MAGUK, discs-large, disrupt the GK/MAP-1A interaction. Additional biochemical experiments demonstrate that intact MAGUKs do not bind to MAP1A as effectively as do isolated GK domains. This appears to be attributable to an intramolecular inhibition of the GK domain by the PDZs, because GK binding activity of full-length MAGUKs is partially restored by a variety of PDZ ligands, including the C termini of NMDA receptor 2B, adenomatous polyposis coli (APC), and CRIPT. Beyond demonstrating a novel cytoskeletal link for PSD-93, these experiments support a model in which intramolecular interactions between the multiple domains of MAGUKs regulate intermolecular associations and thereby may play a role in the proper targeting and function of MAGUK proteins.
Funded by: NINDS NIH HHS: NS23347, NS36017
The Journal of neuroscience : the official journal of the Society for Neuroscience 1998;18;21;8805-13
A tripartite protein complex with the potential to couple synaptic vesicle exocytosis to cell adhesion in brain.
Center for Basic Neuroscience, Department of Molecular Genetics, Howard Hughes Medical Institute, The University of Texas Southwestern Medical Center at Dallas, 75235, USA.
We identify a complex of three proteins in brain that has the potential to couple synaptic vesicle exocytosis to neuronal cell adhesion. The three proteins are: (1) CASK, a protein related to MAGUKs (membrane-associated guanylate kinases); (2) Mint1, a putative vesicular trafficking protein; and (3) Veli1, -2, and -3, vertebrate homologs of C. elegans LIN-7. CASK, Mint1, and Velis form a tight, salt-resistant complex that can be readily isolated. CASK, Mint1, and Velis contain PDZ domains in addition to other modules. However, no PDZ domains are involved in complex formation, leaving them free to recruit cell adhesion molecules, receptors, and channels to the complex. We propose that the tripartite complex acts as a nucleation site for the assembly of proteins involved in synaptic vesicle exocytosis and synaptic junctions.
Funded by: NIMH NIH HHS: R01-MH52804
Cell 1998;94;6;773-82
SAP97 is associated with the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor GluR1 subunit.
Department of Pharmacology, University of Wisconsin, Madison, Wisconsin 53706-1532, USA.
Rapid glutamatergic synaptic transmission is mediated by ionotropic glutamate receptors and depends on their precise localization at postsynaptic membranes opposing the presynaptic neurotransmitter release sites. Postsynaptic localization of N-methyl-D-aspartate-type glutamate receptors may be mediated by the synapse-associated proteins (SAPs) SAP90, SAP102, and chapsyn-110. SAPs contain three PDZ domains that can interact with the C termini of proteins such as N-methyl-D-aspartate receptor subunits that carry a serine or threonine at the -2 position and a valine, isoleucine, or leucine at the very C terminus (position 0). We now show that SAP97, a SAP whose function at the synapse has been unclear, is associated with alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-type glutamate receptors. AMPA receptors are probably tetramers and are formed by two or more of the four AMPA receptor subunits GluR1-4. GluR1 possesses a C-terminal consensus sequence for interactions with PDZ domains of SAPs. SAP97 was present in AMPA receptor complexes immunoprecipitated from detergent extracts of rat brain. After treatment of rat brain membrane fractions with the cross-linker dithiobis(succinimidylpropionate) and solubilization with sodium dodecylsulfate, SAP97 was associated with GluR1 but not GluR2 or GluR3. In vitro experiments with recombinant proteins indicate that SAP97 specifically associates with the C terminus of GluR1 but not other AMPA receptor subunits. Our findings suggest that SAP97 may be involved in localizing AMPA receptors at postsynaptic sites through its interaction with the GluR1 subunit.
Funded by: NIA NIH HHS: AG12978; NINDS NIH HHS: R01-NS35563
The Journal of biological chemistry 1998;273;31;19518-24
PUBMED: 9677374; DOI: 10.1074/jbc.273.31.19518
CRIPT, a novel postsynaptic protein that binds to the third PDZ domain of PSD-95/SAP90.
Department of Neurobiology and Howard Huges Medical Institute, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
The synaptic protein PSD-95/SAP90 binds to and clusters a variety of membrane proteins via its two N-terminal PDZ domains. We report a novel protein, CRIPT, which is highly conserved from mammals to plants and binds selectively to the third PDZ domain (PDZ3) of PSD-95 via its C terminus. While conforming to the consensus PDZ-binding C-terminal sequence (X-S/T-X-V-COOH), residues at the -1 position and upstream of the last four amino acids of CRIPT determine its specificity for PDZ3. In heterologous cells, CRIPT causes a redistribution of PSD-95 to microtubules. In brain, CRIPT colocalizes with PSD-95 in the postsynaptic density and can be coimmunoprecipitated with PSD-95 and tubulin. These findings suggest that CRIPT may regulate PSD-95 interaction with a tubulin-based cytoskeleton in excitatory synapses.
Funded by: NINDS NIH HHS: NS29879, NS33184, NS35050
Neuron 1998;20;4;693-707
Binding of neuroligins to PSD-95.
Takai Biotimer Project, ERATO, Japan Science and Technology Corporation, 2-2-10, Murotani, Nishi-ku, Kobe, 651-22, Japan.
PSD-95 is a component of postsynaptic densities in central synapses. It contains three PDZ domains that localize N-methyl-D-aspartate receptor subunit 2 (NMDA2 receptor) and K+ channels to synapses. In mouse forebrain, PSD-95 bound to the cytoplasmic COOH-termini of neuroligins, which are neuronal cell adhesion molecules that interact with beta-neurexins and form intercellular junctions. Neuroligins bind to the third PDZ domain of PSD-95, whereas NMDA2 receptors and K+ channels interact with the first and second PDZ domains. Thus different PDZ domains of PSD-95 are specialized for distinct functions. PSD-95 may recruit ion channels and neurotransmitter receptors to intercellular junctions formed between neurons by neuroligins and beta-neurexins.
Funded by: NIMH NIH HHS: R01-MH52804
Science (New York, N.Y.) 1997;277;5331;1511-5
Disulfide-linked head-to-head multimerization in the mechanism of ion channel clustering by PSD-95.
Howard Hughes Medical Institute and Department of Neurobiology, Massachusetts General Hospital and Harvard Medical School, Boston 02214, USA.
The PSD-95/SAP90 family of PDZ-containing proteins is directly involved in the clustering of specific ion channels at synapses. We report that channel clustering depends on a conserved N-terminal domain of PSD-95 that mediates multimerization and disulfide linkage of PSD-95 protomers. This N-terminal multimerization domain confers channel clustering activity on a single PDZ domain. Thus, channel clustering depends on aggregation of PDZ domains achieved by head-to-head multimerization of PSD-95, rather than by concatenation of PDZ domains in PSD-95 monomers. This mechanism predicts that PSD-95 can organize heterogeneous membrane protein clusters via differential binding specificities of its three PDZ domains. PSD-95 and its relative chapsyn-110 exist as disulfide-linked complexes in rat brain, consistent with head-to-head multimerization of these proteins in vivo.
Neuron 1997;18;5;803-14
Cloning and characterization of postsynaptic density 93, a nitric oxide synthase interacting protein.
Department of Physiology, University of California at San Francisco School of Medicine, 94143-0444, USA.
Nitric oxide (NO) formation in brain is regulated by the calcium/calmodulin dependence of neuronal NO synthase (nNOS). Calcium influx through NMDA-type glutamate receptors is efficiently coupled to nNOS activity, whereas many other intracellular calcium pathways are poorly coupled. To elucidate possible mechanisms responsible for this coupling, we performed yeast two-hybrid screening to identify proteins that interact with nNOS. Two nNOS interacting proteins were identified: the postsynaptic density proteins PSD-93 and PSD-95. Here, we report the cloning and characterization of PSD-93. PSD-93 is expressed in discrete neuronal populations as well as in specific non-neuronal cells, and it exhibits complex molecular diversity attributable to tissue-specific alternative splicing. PSD-93, like PSD-95, binds to nNOS and to the NMDA receptor 2B. PSD-93, however, is unique among PSD-95/SAP-90 family members in its expression in Purkinje neuron cell bodies and dendrites. We also demonstrate that the PDZ domain at the N terminus of nNOS is required, but it is not sufficient for interaction with PSD-93/95. Given that PSD-93 and PSD-95 each contain multiple potential binding sites for nNOS and the NMDA receptor, complexes involving oligomers of PSD-93/95 may help account for the functional as well as the physical coupling of nNOS to NMDA receptors.
The Journal of neuroscience : the official journal of the Society for Neuroscience 1996;16;23;7407-15
Heteromultimerization and NMDA receptor-clustering activity of Chapsyn-110, a member of the PSD-95 family of proteins.
Howard Hughes Medical Institute, Department of Neurobiology, Massachusetts General Hospital, Boston 02114, USA.
Chapsyn-110, a novel membrane-associated putative guanylate kinase (MAGUK) that binds directly to N-methyl-D-aspartate (NMDA) receptor and Shaker K+ channel subunits, is 70%-80% identical to, and shares an identical domain organization with, PSD-95/SAP90 and SAP97. In rat brain, chapsyn-110 protein shows a somatodendritic expression pattern that overlaps partly with PSD-95 but that contrasts with the axonal distribution of SAP97. Chapsyn-110 associates tightly with the postsynaptic density in brain, and mediates the clustering of both NMDA receptors and K+ channels in heterologous cells. Indeed, chapsyn-110 and PSD-95 can heteromultimerize with each other and are recruited into the same NMDA receptor and K+ channel clusters. Thus, chapsyn-110 and PSD-95 may interact at postsynaptic sites to form a multimeric scaffold for the clustering of receptors, ion channels, and associated signalling proteins.
Neuron 1996;17;1;103-13
Interaction of nitric oxide synthase with the postsynaptic density protein PSD-95 and alpha1-syntrophin mediated by PDZ domains.
Department of Physiology, School of Medicine, University of California at San Fancisco, California 94143, USA.
Neuronal nitric oxide synthase (nNOS) is concentrated at synaptic junctions in brain and motor endplates in skeletal muscle. Here, we show that the N-terminus of nNOS, which contains a PDZ protein motif, interacts with similar motifs in postsynaptic density-95 protein (PSD-95) and a related novel protein, PSD-93.nNOS and PSD-95 are coexpressed in numerous neuronal populations, and a PSD-95/nNOS complex occurs in cerebellum. PDZ domain interactions also mediate binding of nNOS to skeletal muscle syntrophin, a dystrophin-associated protein. nNOS isoforms lacking a PDZ domain, identified in nNOSdelta/delta mutant mice, do not associate with PSD-95 in brain or with skeletal muscle sarcolemma. Interaction of PDZ-containing domains therefore mediates synaptic association of nNOS and may play a more general role in formation of macromolecular signaling complexes.
Cell 1996;84;5;757-67
Clustering of Shaker-type K+ channels by interaction with a family of membrane-associated guanylate kinases.
Howard Hughes Medical Institute, Massachusetts General Hospital, Department of Neurobiology, Harvard Medical School, Boston 02114, USA.
ANCHORING of ion channels at specific subcellular sites is critical for neuronal signalling, but the mechanisms underlying channel localization and clustering are largely unknown (reviewed in ref. 1). Voltage-gated K+ channels are concentrated in various neuronal domains, including presynaptic terminals, nodes of Ranvier and dendrites, where they regulate local membrane excitability. Here we present functional and biochemical evidence that cell-surface clustering of Shaker-subfamily K+ channels is mediated by the PSD-95 family of membrane-associated putative guanylate kinases, as a result of direct binding of the carboxy-terminal cytoplasmic tails to the K+ channel subunits to two PDZ (also known as GLGF or DHR) domains in the PSD-95 protein. The ability of PDZ domains to function as independent modules for protein-protein interaction, and their presence in other junction-associated molecules (such as ZO-1 (ref. 3) and syntrophin), suggest that PDZ-domain-containing polypeptides may be widely involved in the organization of proteins at sites of membrane specialization.
Nature 1995;378;6552;85-8
PUBMED: 7477295; DOI: 10.1038/378085a0
OMIM - other
Gene lists (11)
|Gene List
|Gene count
|Homo sapiens
|Human PSD
|Human orthologues of mouse PSD adapted from Collins et al (2006)
|Homo sapiens
|Human clathrin
|Human orthologues of mouse clathrin coated vesicle genes adapted from Collins et al (2006)
|Homo sapiens
|Human Synaptosome
|Human orthologues of mouse synaptosome adapted from Collins et al (2006)
|Homo sapiens
|Human NRC
|Human orthologues of mouse NRC adapted from Collins et al (2006)
|Homo sapiens
|Human PSP
|Human orthologues of mouse PSP adapted from Collins et al (2006)
|Homo sapiens
|Pocklington H1
|Human orthologues of cluster 1 (mouse) from Pocklington et al (2006)
|Homo sapiens
|TAP-PSD-95 pull-down core list (ortho)
|Homo sapiens
|Human cortex PSD consensus
|Homo sapiens
|Mouse cortex PSD consensus (ortho)
|Homo sapiens
|Human cortex biopsy PSD full list
|Homo sapiens
|Mouse cortex PSD full list (ortho)


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