| Annotated protein: | Disks large homolog 1 (Embryo-dlg/synapse-associated protein 97) (E-dlg/SAP97) (Synapse-associated protein 97) (SAP-97) (SAP97). Gene symbol: DLG1. Taxonomy: Mus musculus (Mouse). Uniprot ID: Q811D0 |
| antibody wiki: | |
| SynGO gene info: | SynGO data @ DLG1 |
| Ontology domain: | Biological Process |
| SynGO term: | neurotransmitter receptor localization to postsynaptic specialization membrane (GO:0099645) |
| Synapse type(s): | hippocampus, glutamatergic |
| Annotated paper: | Howard MA, et al. "The role of SAP97 in synaptic glutamate receptor dynamics" Proc Natl Acad Sci U S A. 2010 Feb 23;107(8):3805-10 PMID:20133708 |
| Figure(s): | Figures 1, 2, 3, 4, 5 |
| Annotation description: | SAP97 is part of the machinery that traffics glutamate receptors to the PSD of dendritic spines. In CA1 pyramidal neurons, SAP97 is functionally redundant with other PSD-MAGUKs: "SAP97 is sufficient, but not individually necessary, for AMPAR trafficking to synapses." SAP97 is distinguished from other PSD-MAGUKs by its ability to directly interact with the GluA1 subunit of AMPARs. Fig. 1: "SAP97 Overexpression Enhances Glutamatergic Synaptic Transmission in Immature Neurons." Overexpression of SAP97β hippocampal slice cultures enhanced AMPAR and NMDAR EPSC amplitudes compared to neighboring, control cells (slices from P2 mice, cultured 5d prior viral infection). PPR was not affected by SAP97β expression. These data suggest, "SAP97β is highly effective at trafficking both AMPARs and NMDARs to synapses early in development, at a time when receptor density at synapses is low." Fig. 2: "Long-term in vivo SAP97β overexpression enhances synaptic transmission." SAP97β-GFP was overexpressed in utero at E16; acute hippocampal slices from P8-9 were assayed for effects on synaptic transmission. AMPAR and NMDAR currents were significantly enhanced by SAP97β overexpression, as was the AMPA/NMDA ratio. Isolated NMDAR currents were further shown to have faster decay kinetics. In contrast to Fig. 1B, neurons overexpressing SAP97β throughout development exhibited a significant decrease in PPR relative to control cells. These data are consistent with the involvement of SAP97 in trans-synaptic signaling (previously reported). "Overall, these experiments indicate that SAP97, when overexpressed in a chronic fashion in vivo throughout development rather than acutely in vitro, can greatly enhance synaptic glutamate receptor trafficking." Fig. 3. "Deleting SAP97 does not alter basal synaptic transmission in immature neurons." Western blot analysis confirms loss of SAP97 protein in hippocampal extracts from SAP97 conditional KO mice (ΔSAP97, Dlgh1-fl/fl; nestin-Cre, Fig. 3A). Acute slices made from P9 WT and ΔSAP97 mice showed no significant difference in glutamatergic transmission. Fig. 5. "Deleting SAP97 does not alter basal synaptic transmission or LTP in mature neurons." Acute hippocampal slices from P18-21 WT and ΔSAP97 mice. Fig. 4. "SAP97β overexpression does not enhance synaptic transmission in mature neurons but compensates for PSD-93/-95 double KO." Overexpression of SAP97β in hippocampal slice cultures from WT and PSD-93/-95 double KO mice. SAP97β enhanced AMPAR currents double KO but not WT neurons. NMDAR currents, which are normal in these mice, were unchanged. These data suggest "a virtually complete compensation by SAP97β for the mutant phenotype caused by the elimination of two key PSD-MAGUK proteins." |
| Evidence tracking, Biological System: | Intact tissue |
| Evidence tracking, Protein Targeting: | Genetic transformation (eg; knockout, knockin, mutations) Over-expression Antibody (detection) |
| Evidence tracking, Experiment Assay: | Whole-cell patch clamp Electrophysiology (generic) Western blot |
| Annotator(s): | Hana Goldschmidt (ORCID:0000-0002-5676-366X) Richard Huganir (ORCID:0000-0001-9783-5183) |
| Lab: | Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA and Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD 21205, USA |
| Additional literature: | Unlike PSD-93 and PSD-95, SAP97 can binds directly to the GluA1 subunit of AMPARs. @ PMID:9677374 SAP97 regulation of AMPAR synaptic targeting and spine morphology is modulated by alternative splicing. Figure 3. Overexpression of SAP97 causes the enlargement of dendritic spines. DIV 15 cortical neurons transfected with eGFP and myc-SAP97. Figure 4. Expression of GFP-SAP97 enhances expression of surface AMPARs and synaptic transmission in primary cultured neurons. Hippocampal neurons (DIV 10-14) transfected with GFP-SAP97 were live-labeled with N-terminal GluA1 antibodies; overexpression of GFP-SAP97 increased surface GluA1 staining as well as the size of surface GluA1 clusters of AMPARs compared to neighboring, untransfected cells (Fig. 4A-B). DIV 14-16 cultured cortical neurons expressing GFP-SAP97 exhibited a strong enhancement in the frequency of mEPSCs and a slight but not significant decrease in mEPSC amplitude compared with eGFP-expressing neurons (Fig. 4C). Older neurons (DIV 28) expressing GFP-SAP97 showed no significant difference in mEPSC frequency or amplitude from controls (Fig. 4D). "There was a trend toward an increase in mEPSC frequency, but it did not reach a level of significance." Figure 5. A protein 4.1 binding motif and f-actin are required for GFP-SAP97 targeting to spines. The hook region of SAP97 is a site of alternative splicing and a critical region required for targeting of SAP97 to dendritic spines. Examined spatial distribution of GFP-SAP97 deletion constructs in cortical neurons (DIV 14). GFP-SAP97-I2 showed diffuse localization indistinguishable from GFP-SAP97ΔI3, where GFP-SAP97 (I3) was concentrated in dendritic spines. Fig. 6C-E: Confirmed the I3 isoform of SAP97 is expressed in cultured cortical neurons (DIV 14) by reverse transcription (RT)-PCR. SAP97-I2 and -I5 splice variants were also found. Fig. 7: "The I3 sequence is necessary for SAP97-mediated increases in surface AMPA receptors and alterations in mEPSC frequency." Analysis of surface GluA1-AMPARs and mEPSCs in DIV 10 hippocampal neurons transfected with GFP-SAP97ΔI3. additional info: Figs. 1-2. Subcellular localization of endogenous and GFP-SAP97 in primary neurons. @ PMID:12805297 coIP analysis in extracts from HEK cells and rat brain. "CaMKII associates with SAP97 in the brain and preferentially phosphorylates a specific SAP97 splice variant of the U5 region. AKAP79/150 also preferentially interacts with this splice variant, but CaMKII-mediated phosphorylation disrupts the interaction. Moreover, CaMKII disrupts AKAP79-dependent regulation of GluR1 AMPARs, which relies on Ser-845 phosphorylation/ dephosphorylation." @ PMID:19858198 |
| SynGO annotation ID: | 2741 |
| Dataset release (version): | 20231201 |
| View annotation as GO-CAM model: |  |