Synj is a dual-domain phosphoinositide phosphatase that supports synaptic vesicle recycling. Its SAC domain and central inositol 5-phosphatase region act within a long protein recruited to presynaptic vesicles by Endophilin. In Drosophila, Synj loss disrupts synaptic vesicle organization and transmission, consistent with phosphoinositide turnover during vesicle uncoating.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003676 nucleic acid binding | IEA GO_REF:0000002 | UNDECIDED | Summary: Nucleic-acid binding is not established by the phosphatase architecture. Reason: The independent fly experiments establish lipid dephosphorylation and vesicle recycling. The broad domain-derived nucleic-acid binding assertion needs a specific binding assay; a phosphoinositide substrate is not a nucleic acid. Supporting Evidence: PMID:14622578 synj encodes a phosphatidylinositol phosphatase involved in clathrin-mediated endocytosis. |
| GO:0004439 phosphatidylinositol-4,5-bisphosphate 5-phosphatase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Synaptojanin removes the 5-phosphate from phosphoinositide substrates. Reason: The exact long product contains the SAC and central 5-phosphatase regions. Fly mutant studies establish the phosphatidylinositol-phosphatase mechanism in synaptic vesicle uncoating, supporting the conserved PI(4,5)P2 reaction rather than relying on an ARBA description. Supporting Evidence: PMID:14622578 synj encodes a phosphatidylinositol phosphatase involved in clathrin-mediated endocytosis. PMID:14622578 Endophilin recruits and stabilizes Synj on newly formed vesicles to promote vesicle uncoating. |
| GO:0004439 phosphatidylinositol-4,5-bisphosphate 5-phosphatase activity | IEA GO_REF:0000003 | ACCEPT | Summary: Synaptojanin removes the 5-phosphate from phosphoinositide substrates. Reason: The exact long product contains the SAC and central 5-phosphatase regions. Fly mutant studies establish the phosphatidylinositol-phosphatase mechanism in synaptic vesicle uncoating, supporting the conserved PI(4,5)P2 reaction rather than relying on an ARBA description. Supporting Evidence: PMID:14622578 synj encodes a phosphatidylinositol phosphatase involved in clathrin-mediated endocytosis. PMID:14622578 Endophilin recruits and stabilizes Synj on newly formed vesicles to promote vesicle uncoating. |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: Synj acts on the cytoplasmic face of presynaptic membranes. Reason: Direct fly localization identifies presynaptic terminals and vesicles, fitting recruitment of a soluble phosphatase to cytoplasm-facing membrane lipids. Supporting Evidence: PMID:14622578 We show that Synj is specifically localized to presynaptic terminals and is associated with synaptic vesicles. PMID:14622578 Endophilin recruits and stabilizes Synj on newly formed vesicles to promote vesicle uncoating. |
| GO:0016020 membrane | IBA GO_REF:0000033 | ACCEPT | Summary: Peripheral membrane association is part of the Synj mechanism. Reason: Synj is associated with synaptic vesicles and recruited by Endophilin. This is membrane association rather than an integral transmembrane protein claim. Supporting Evidence: PMID:14622578 We show that Synj is specifically localized to presynaptic terminals and is associated with synaptic vesicles. PMID:14622578 Endophilin recruits and stabilizes Synj on newly formed vesicles to promote vesicle uncoating. |
| GO:0016791 phosphatase activity | IEA GO_REF:0000002 | MODIFY | Summary: Phosphoinositide 5-phosphatase specifies generic phosphatase activity. Reason: The lipid-phosphatase architecture and synaptic endocytic role warrant the substrate-defined term. Proposed replacements: phosphatidylinositol-4,5-bisphosphate 5-phosphatase activity Supporting Evidence: PMID:14622578 synj encodes a phosphatidylinositol phosphatase involved in clathrin-mediated endocytosis. |
| GO:0045202 synapse | IEA GO_REF:0000044 | ACCEPT | Summary: Synaptic localization is directly established in fly. Reason: The primary report specifically localizes Synj to presynaptic terminals, supporting the broader synapse annotation. Supporting Evidence: PMID:14622578 We show that Synj is specifically localized to presynaptic terminals and is associated with synaptic vesicles. |
| GO:0046856 phosphatidylinositol dephosphorylation | IEA GO_REF:0000002 | ACCEPT | Summary: Phosphatidylinositol dephosphorylation drives coat turnover. Reason: The lipid-phosphatase mechanism links Synj recruitment to vesicle uncoating; this is the direct chemical process underlying the synaptic phenotype. Supporting Evidence: PMID:14622578 synj encodes a phosphatidylinositol phosphatase involved in clathrin-mediated endocytosis. PMID:14622578 Endophilin recruits and stabilizes Synj on newly formed vesicles to promote vesicle uncoating. |
| GO:0048488 synaptic vesicle endocytosis | IBA GO_REF:0000033 | ACCEPT | Summary: Synaptic vesicle endocytosis is a core role of Synj. Reason: Fly synj mutants show electrophysiological and ultrastructural endocytic defects, and Endophilin recruits Synj during vesicle uncoating. Supporting Evidence: PMID:14622578 synj encodes a phosphatidylinositol phosphatase involved in clathrin-mediated endocytosis. PMID:14622578 Endophilin recruits and stabilizes Synj on newly formed vesicles to promote vesicle uncoating. |
| GO:0052658 inositol-1,4,5-trisphosphate 5-phosphatase activity | IBA GO_REF:0000033 | UNDECIDED | Summary: Soluble inositol-trisphosphate hydrolysis requires distinct substrate evidence. Reason: The shared 5-phosphatase architecture makes this inherited reaction plausible, but the inspected direct fly experiments resolve membrane phosphoinositides and vesicle uncoating, not soluble Ins(1,4,5)P3 turnover by this product. No evidence of catalytic loss is asserted. Supporting Evidence: PMID:14622578 synj encodes a phosphatidylinositol phosphatase involved in clathrin-mediated endocytosis. |
| GO:0098793 presynapse | IEA GO_REF:0000108 | ACCEPT | Summary: Presynapse is the experimentally supported synaptic compartment. Reason: The primary paper explicitly identifies presynaptic-terminal localization and vesicle association. Supporting Evidence: PMID:14622578 We show that Synj is specifically localized to presynaptic terminals and is associated with synaptic vesicles. |
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