SYNGAP1 encodes SynGAP, a brain-specific Ras/Rap GTPase-activating protein that is one of the most abundant proteins in the postsynaptic density (PSD) of excitatory synapses. SynGAP functions as a dual-specificity GAP for both Ras and Rap small GTPases. By accelerating GTP hydrolysis, SynGAP inactivates these signaling molecules, thereby serving as a negative regulator of Ras-ERK/MAPK and Rap signaling pathways at synapses. This regulation controls AMPA receptor trafficking to the postsynaptic membrane, dendritic spine maturation, and long-term synaptic plasticity. SynGAP is regulated by phosphorylation from CaMKII and CDK5, which modulates its GAP activity and synaptic localization. The protein contains PH, C2, and Ras-GAP domains, along with a C-terminal PDZ-binding motif that anchors it to PSD-95 and related scaffolds. De novo heterozygous loss-of-function mutations cause SYNGAP1-related intellectual disability and epilepsy through haploinsufficiency.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005096 GTPase activator activity | IBA GO_REF:0000033 | ACCEPT | Summary: SynGAP is a well-established dual-specificity GTPase activator for both Ras and Rap family GTPases. The GAP domain provides canonical arginine-finger catalysis for GTP hydrolysis. Reason: GTPase activator activity is the primary molecular function of SynGAP. The protein contains a Ras-GAP domain (residues 459-667) that catalyzes GTP hydrolysis on Ras and Rap GTPases. The IBA annotation is well-supported by phylogenetic inference from other characterized RasGAP family members. Supporting Evidence: UniProt:Q96PV0 Exhibits dual GTPase-activating specificity for Ras and Rap file:human/SYNGAP1/SYNGAP1-deep-research-openai.md See deep research file for comprehensive analysis |
| GO:1902531 regulation of intracellular signal transduction | IBA GO_REF:0000033 | ACCEPT | Summary: SynGAP regulates intracellular signal transduction by inactivating Ras and Rap GTPases at synapses, thereby modulating downstream MAPK/ERK signaling cascades and AMPA receptor trafficking pathways. Reason: This biological process annotation accurately captures SynGAP's role in modulating Ras-ERK and Rap signaling pathways at excitatory synapses. The annotation is appropriately general since SynGAP regulates multiple signaling cascades through its GAP activity. Supporting Evidence: UniProt:Q96PV0 Inhibitory regulator of the Ras-cAMP pathway |
| GO:0005096 GTPase activator activity | IEA GO_REF:0000120 | ACCEPT | Summary: Duplicate annotation of GTPase activator activity from combined automated methods. Consistent with the IBA annotation. Reason: This IEA annotation is redundant with the IBA annotation above but is correct. The combined automated annotation approach correctly identifies GTPase activator activity as a core function based on sequence and domain analysis. Supporting Evidence: UniProt:Q96PV0 Exhibits dual GTPase-activating specificity for Ras and Rap |
| GO:0005886 plasma membrane | IEA GO_REF:0000108 | MODIFY | Summary: SynGAP is a cytosolic protein that is recruited to the postsynaptic membrane region through protein-protein interactions with PSD-95 and other scaffold proteins, rather than directly associating with the plasma membrane itself. Reason: While SynGAP does localize near the plasma membrane at synapses, it is a cytosolic protein that lacks transmembrane domains. It associates with the postsynaptic density through PDZ-binding motif interactions with PSD-95. A more accurate annotation would be postsynaptic density (GO:0014069) or glutamatergic synapse (GO:0098978). Proposed replacements: postsynaptic density glutamatergic synapse Supporting Evidence: UniProt:Q96PV0 Major constituent of the PSD essential for postsynaptic signaling |
| GO:0017124 SH3 domain binding | IEA GO_REF:0000043 | ACCEPT | Summary: SynGAP contains a proline-rich region that mediates SH3 domain binding. This annotation is based on UniProt keyword mapping. Reason: UniProt annotates an SH3-binding motif at residues 785-815 in SynGAP, consistent with this annotation. Supporting Evidence: UniProt:Q96PV0 MOTIF 785..815 /note="SH3-binding" /evidence="ECO:0000255" |
| GO:0046580 negative regulation of Ras protein signal transduction | IEA GO_REF:0000002 | ACCEPT | Summary: SynGAP negatively regulates Ras signaling by accelerating GTP hydrolysis, converting active Ras-GTP to inactive Ras-GDP. This is a core function. Reason: This annotation correctly captures SynGAP's inhibitory role in Ras signaling. By functioning as a RasGAP, SynGAP terminates Ras signaling and thereby limits downstream ERK/MAPK activation and AMPA receptor insertion at synapses. Supporting Evidence: UniProt:Q96PV0 Inhibitory regulator of the Ras-cAMP pathway |
| GO:0005515 protein binding | IPI PMID:30021884 Histone Interaction Landscapes Visualized by Crosslinking Ma... | MARK AS OVER ANNOTATED | Summary: This annotation derives from a high-throughput crosslinking mass spectrometry study showing interaction with histone H1-4. Reason: While the interaction may be detectable in this HT-XL-MS study, it is not informative about SynGAP's specific function. SynGAP is a synaptic protein and interaction with histones is likely non-specific. The generic "protein binding" term provides no functional insight. Supporting Evidence: UniProt:Q96PV0 Interacts with MPDZ (PubMed:15312654) |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | MARK AS OVER ANNOTATED | Summary: This annotation derives from HuRI, a systematic binary protein interactome mapping study. Reason: While the interactions detected in HuRI may be valid, the generic "protein binding" term does not provide functional insight. For a scaffold-associated signaling protein like SynGAP, more informative annotations would specify the type of binding. Supporting Evidence: UniProt:Q96PV0 Interacts with MPDZ (PubMed:15312654) |
| GO:0005515 protein binding | IPI PMID:36950384 Protein interaction studies in human induced neurons indicat... | KEEP AS NON CORE | Summary: Protein interaction studies in human induced neurons indicate convergent biology underlying autism spectrum disorders. Reason: While these interactions detected in induced neurons are more relevant to SynGAP's neuronal function than other HT studies, the generic "protein binding" term is uninformative. However, the study context (ASD-related proteins in neurons) adds some biological relevance. Supporting Evidence: UniProt:Q96PV0 Interacts with MPDZ (PubMed:15312654) |
| GO:0005515 protein binding | IPI PMID:37207277 Using brain cell-type-specific protein interactomes to inter... | KEEP AS NON CORE | Summary: Brain cell-type-specific protein interactome study relating to schizophrenia genetic signals. Reason: The brain-specific context makes these interactions more relevant to SynGAP function than generic HT studies, but the "protein binding" term remains uninformative. Supporting Evidence: UniProt:Q96PV0 Interacts with MPDZ (PubMed:15312654) |
| GO:0007265 Ras protein signal transduction | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP participates in Ras protein signal transduction as a negative regulator, inactivating Ras-GTP to terminate signaling. Reason: This annotation correctly identifies SynGAP's involvement in Ras signaling. While SynGAP is a negative regulator, participation in the pathway is accurately captured. Supporting Evidence: UniProt:Q96PV0 Inhibitory regulator of the Ras-cAMP pathway |
| GO:0007389 pattern specification process | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Pattern specification is a developmental process. While SynGAP may affect brain development, this annotation appears indirect for a synaptic signaling protein. Reason: SynGAP has developmental roles affecting cortical organization, which could relate to pattern specification. However, this is not a core function - its primary role is synaptic signaling regulation. Supporting Evidence: UniProt:Q96PV0 Major constituent of the PSD essential for postsynaptic signaling |
| GO:0008542 visual learning | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Visual learning phenotypes have been observed in Syngap1 mouse models, but this is a downstream behavioral consequence rather than a direct molecular function. Reason: While Syngap1 mutant mice show learning and memory deficits, this behavioral phenotype is a consequence of disrupted synaptic plasticity rather than a direct molecular function. Supporting Evidence: UniProt:Q96PV0 May be involved in certain forms of brain injury, leading to long-term learning and memory deficits |
| GO:0014069 postsynaptic density | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP is one of the most abundant proteins in the postsynaptic density of excitatory synapses. Reason: Postsynaptic density localization is extremely well-established for SynGAP. It is among the most abundant PSD proteins, anchored via its C-terminal PDZ-binding motif to PSD-95. Supporting Evidence: UniProt:Q96PV0 Major constituent of the PSD essential for postsynaptic signaling |
| GO:0016020 membrane | IEA GO_REF:0000107 | MODIFY | Summary: SynGAP is a cytosolic protein that associates with membrane-proximal regions through protein-protein interactions. Reason: The generic "membrane" term is too vague for SynGAP. The protein is cytosolic and lacks transmembrane domains. It associates with the postsynaptic membrane region indirectly through binding to scaffold proteins like PSD-95. Proposed replacements: postsynaptic density Supporting Evidence: UniProt:Q96PV0 Major constituent of the PSD essential for postsynaptic signaling |
| GO:0016358 dendrite development | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP regulates dendritic spine maturation and morphology through its effects on Ras/Rap signaling and AMPA receptor trafficking. Reason: Dendrite development, particularly dendritic spine maturation, is a well-documented function of SynGAP. Haploinsufficiency leads to accelerated spine maturation. Supporting Evidence: UniProt:Q96PV0 may play a role in NMDAR-dependent control of AMPAR potentiation, AMPAR membrane trafficking and synaptic plasticity |
| GO:0043113 receptor clustering | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP regulates AMPA receptor trafficking and clustering at synapses through its effects on Ras/Rap signaling. Reason: Receptor clustering, specifically AMPA receptor organization at synapses, is a key function of SynGAP. SynGAP competes with AMPA receptor/TARP complexes for PSD-95 binding, directly regulating receptor abundance. Supporting Evidence: UniProt:Q96PV0 may play a role in NMDAR-dependent control of AMPAR potentiation, AMPAR membrane trafficking and synaptic plasticity |
| GO:0043198 dendritic shaft | IEA GO_REF:0000107 | MODIFY | Summary: SynGAP is primarily localized to dendritic spines at the postsynaptic density rather than the dendritic shaft proper. Reason: While SynGAP may be detected in dendritic shafts, its primary and functionally relevant localization is in dendritic spines at the postsynaptic density. Proposed replacements: postsynaptic density dendritic spine Supporting Evidence: UniProt:Q96PV0 Major constituent of the PSD essential for postsynaptic signaling |
| GO:0043408 regulation of MAPK cascade | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP regulates the MAPK cascade by modulating Ras activity, which is upstream of the ERK/MAPK signaling pathway. Reason: Regulation of the MAPK cascade is a core function of SynGAP. By inactivating Ras-GTP, SynGAP dampens downstream ERK/MAPK signaling. Supporting Evidence: UniProt:Q96PV0 Inhibitory regulator of the Ras-cAMP pathway UniProt:Q96PV0 VARIANT 362 /note="W -> R (in MRD5; the mutant protein is less efficient in inhibiting ERK phosphorylation induced by neuronal activity)" |
| GO:0043524 negative regulation of neuron apoptotic process | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: While SynGAP may have indirect effects on neuronal survival, this is not a well-established or direct function. Reason: Anti-apoptotic effects may occur as a downstream consequence of SynGAP's regulation of Ras-MAPK signaling, but this is not a core or direct function. The primary role of SynGAP is synaptic signaling. Supporting Evidence: UniProt:Q96PV0 May be involved in certain forms of brain injury, leading to long-term learning and memory deficits |
| GO:0048169 regulation of long-term neuronal synaptic plasticity | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP is a key regulator of long-term synaptic plasticity (LTP and LTD) through its control of Ras/Rap signaling and AMPA receptor trafficking. Reason: Regulation of synaptic plasticity is a core function of SynGAP. The protein sets the threshold for LTP induction and is phosphorylated during plasticity to permit synaptic strengthening. Supporting Evidence: UniProt:Q96PV0 may play a role in NMDAR-dependent control of AMPAR potentiation, AMPAR membrane trafficking and synaptic plasticity |
| GO:0050771 negative regulation of axonogenesis | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Effects on axon development may be indirect consequences of SynGAP's effects on neuronal development and Ras signaling. Reason: While SynGAP may influence axon development through its effects on Ras signaling, this is not a primary or well-characterized function. SynGAP is predominantly a postsynaptic protein. Supporting Evidence: UniProt:Q96PV0 Member of the NMDAR signaling complex in excitatory synapses |
| GO:0050803 regulation of synapse structure or activity | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP regulates synapse structure and function through multiple mechanisms including AMPA receptor trafficking and dendritic spine maturation. Reason: This is a core function of SynGAP. The protein regulates synapse strength by controlling AMPA receptor levels and modulates synapse structure by affecting dendritic spine morphology and maturation. Supporting Evidence: UniProt:Q96PV0 may play a role in NMDAR-dependent control of AMPAR potentiation, AMPAR membrane trafficking and synaptic plasticity |
| GO:0050804 modulation of chemical synaptic transmission | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP modulates glutamatergic synaptic transmission by regulating AMPA receptor trafficking and postsynaptic signaling. Reason: Modulation of synaptic transmission is a core function of SynGAP. By controlling AMPA receptor levels at synapses and regulating postsynaptic signaling cascades, SynGAP directly affects the strength of excitatory synaptic transmission. Supporting Evidence: UniProt:Q96PV0 Regulates AMPAR-mediated miniature excitatory postsynaptic currents |
| GO:0098880 maintenance of postsynaptic specialization structure | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP contributes to maintaining postsynaptic density structure through its interactions with scaffold proteins. Reason: SynGAP has an important structural role at synapses, interacting with PSD-95 that organize postsynaptic density composition. Supporting Evidence: UniProt:Q96PV0 Major constituent of the PSD essential for postsynaptic signaling |
| GO:0098978 glutamatergic synapse | IEA GO_REF:0000107 | ACCEPT | Summary: SynGAP is highly enriched at glutamatergic excitatory synapses, where it localizes to the postsynaptic density. Reason: Glutamatergic synapse localization is extremely well-established for SynGAP. The protein is expressed specifically in excitatory neurons and is concentrated at glutamatergic synapses. Supporting Evidence: UniProt:Q96PV0 Member of the NMDAR signaling complex in excitatory synapses |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5658231 | ACCEPT | Summary: SynGAP is a cytosolic protein that participates in RAS GAP-mediated stimulation of RAS GTPase activity. Reason: SynGAP is indeed a cytosolic protein lacking transmembrane domains. While it concentrates at synapses through protein-protein interactions, its cytosolic nature is correct. Supporting Evidence: UniProt:Q96PV0 Major constituent of the PSD essential for postsynaptic signaling |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5658435 | ACCEPT | Summary: Duplicate cytosol annotation from Reactome pathway describing RAS GAP binding to RAS:GTP. Reason: This annotation is redundant with the previous cytosol annotation but correctly reflects SynGAP's cytosolic localization and its role in binding RAS-GTP as a GAP. Supporting Evidence: UniProt:Q96PV0 Exhibits dual GTPase-activating specificity for Ras and Rap |
| GO:0046580 negative regulation of Ras protein signal transduction | ISS GO_REF:0000024 | ACCEPT | Summary: ISS annotation from mouse ortholog (UniProtKB:Q9QUH6) supporting SynGAP's role as a negative regulator of Ras signaling. Reason: This annotation duplicates the IEA annotation above but provides additional support through sequence similarity to the well-characterized mouse ortholog. Supporting Evidence: UniProt:Q96PV0 Inhibitory regulator of the Ras-cAMP pathway |
| GO:0048167 regulation of synaptic plasticity | ISS GO_REF:0000024 | ACCEPT | Summary: ISS annotation from mouse ortholog confirming SynGAP's role in regulating synaptic plasticity. Reason: Regulation of synaptic plasticity is a core function of SynGAP, well-established from mouse knockout and heterozygous studies. Supporting Evidence: UniProt:Q96PV0 may play a role in NMDAR-dependent control of AMPAR potentiation, AMPAR membrane trafficking and synaptic plasticity |
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Download this section (compressed HTML)Q: What is the relative contribution of SynGAP's enzymatic GAP activity versus its scaffolding function to synaptic regulation? Some evidence suggests catalytically-dead SynGAP mutants retain normal synaptic plasticity.
Q: How do different SynGAP isoforms (with different C-terminal splicing) differentially affect synaptic function? Alternative splicing generates isoforms with different PDZ-binding motifs that may have distinct effects.
Q: What is SynGAP's role in neural progenitor cells and early brain development independent of its synaptic functions?
Experiment: Compare synaptic phenotypes in mice with catalytically-dead SynGAP versus complete SynGAP knockout to dissect GAP-dependent versus scaffolding functions.
Experiment: Isoform-specific rescue experiments in Syngap1 null neurons to determine distinct functions of N-terminal and C-terminal splice variants.
Experiment: Super-resolution imaging of SynGAP dynamics during synaptic plasticity induction to understand how SynGAP regulates PSD composition during LTP/LTD.
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