Septin4 (Sep4) is a Drosophila SEPT2-class septin GTPase, paralogous to Sep1, that assembles with Septin5 and Peanut into the Sep4-Sep5-Pnut hetero-oligomer. This complex is recruited to wounds independently of Anillin, overlaps the actomyosin ring, and bends actin bundles into wider rings than the Sep1-Sep2-Pnut complex; Sep4 knockdown delays actomyosin ring disassembly during single-cell wound repair. Purified Sep4 binds and bundles actin filaments.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003924 GTPase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Septin GTPase activity inherited from the septin family node. Reason: IBA from PANTHER node PTN000430171 (donors include Pnut, Sep1, yeast Cdc3/Cdc12 and human SEPTIN4). Sep4 is a SEPT2-class septin like Sep1, a class with catalytic GTPase activity; no evidence of loss in Sep4. Supporting Evidence: PMID:38728140 Drosophila has 5 Septins that are grouped into three classes: Sep2 and Sep5 (SEPT6 class), Sep1 and Sep4 (SEPT2 class), and Pnut (SEPT7 class) |
| GO:0003924 GTPase activity | ISS GO_REF:0000024 | ACCEPT | Summary: GTPase activity by similarity to Pnut. Reason: Sep4 belongs to the SEPT2 class together with Sep1, whose GTPase activity is supported experimentally; transfer from Pnut is reasonable for this catalytically competent class, although Sep4 hydrolysis has not been measured directly. Supporting Evidence: PMID:38728140 Drosophila has 5 Septins that are grouped into three classes: Sep2 and Sep5 (SEPT6 class), Sep1 and Sep4 (SEPT2 class), and Pnut (SEPT7 class) |
| GO:0005525 GTP binding | IEA GO_REF:0000120 | ACCEPT | Summary: GTP binding predicted from the septin-type G domain. Reason: Septins bind guanine nucleotide stably; the purified Drosophila complex copurifies with one bound guanine nucleotide per subunit. This holds even for the SEPT6-class subunits (Sep2/Sep5), which bind but do not exchange or hydrolyse GTP. Supporting Evidence: PMID:8636235 The complex copurifies with one molecule of bound guanine nucleotide per septin polypeptide. |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | MODIFY | Summary: Septins are cytoplasmic proteins that assemble at the cortex. Reason: Correct but general; this septin is a subunit of a hetero-oligomeric septin complex, and the gene already carries the more specific cytoplasmic term GO:0031105 septin complex (a descendant of cytoplasm). Proposed replacements: septin complex Supporting Evidence: file:DROME/Septin4/Septin4-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm PMID:38728140 Taken together, our findings further suggest that Sep1/Sep2/Pnut and Sep4/Sep5/Pnut are functioning as distinct complexes within the context of cell wound repair. |
| GO:0005739 mitochondrion | ISS GO_REF:0000024 | REMOVE | Summary: Mitochondrial location transferred from human SEPTIN4. Reason: The ISS donor is human SEPTIN4 (O43236), whose mitochondrial localization belongs to the ARTS splice isoform. Drosophila Sep4 is a SEPT2-class subunit of the cortical Sep4-Sep5-Pnut complex recruited to wound-edge actin rings; there is no evidence of mitochondrial localization, and the isoform-specific human property should not be transferred. Supporting Evidence: PMID:38728140 Pnut, Sep4, and Sep5 are also enriched in a ring at the wound edge, but this ring overlaps completely with the actomyosin ring |
| GO:0005940 septin ring | IBA GO_REF:0000033 | ACCEPT | Summary: Septin ring localization inherited from the septin family. Reason: IBA from PANTHER node PTN000430171 with broad fungal, mammalian, worm and Drosophila donors. Drosophila septins form ring structures at the cleavage furrow and around cell wounds. Supporting Evidence: PMID:38728140 Pnut, Sep4, and Sep5 are also enriched in a ring at the wound edge, but this ring overlaps completely with the actomyosin ring |
| GO:0008021 synaptic vesicle | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: Synaptic vesicle localization inherited from mammalian SEPTIN5. Reason: IBA from node PTN004499727 with donors mouse/rat Sept5 and human SEPTIN5, reflecting a neuron-specific mammalian SEPTIN5 property. No evidence places Drosophila Sep4 on synaptic vesicles. |
| GO:0008104 intracellular protein localization | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Septin scaffolds localise other proteins to the cell cortex. Reason: IBA from PANTHER node PTN000430171 with fungal donors (yeast Shs1/Cdc11, Candida septins) and human SEPTIN14, where septin collars restrict and recruit proteins. Plausible for Drosophila septin scaffolds but not directly shown for this gene; retained as non-core. |
| GO:0015630 microtubule cytoskeleton | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Septin association with microtubules inherited from mammalian/yeast septins. Reason: IBA from PANTHER node PTN000430171 with donors including human SEPTIN2, SEPTIN7, SEPTIN9 and SEPTIN12. Septins do associate with microtubules in some cell types, and Drosophila Pnut/Sep1/Sep2 were recovered in a microtubule/microfilament-associated protein screen, but the primary Drosophila septin structures are cortical and actin-associated. Basis: phylogenetic inference only; no cached Drosophila paper directly shows this septin on microtubules. |
| GO:0017157 regulation of exocytosis | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: Regulation of exocytosis inherited from mammalian SEPTIN5. Reason: IBA from node PTN004499727 whose only donors are rat Sept5 and human SEPTIN5 (CDCrel-1), a neuronal septin that binds syntaxin and regulates synaptic vesicle release. There is no Drosophila evidence for Sep4 in exocytosis; its characterised roles are in cortical actin remodelling within the Sep4-Sep5-Pnut complex. Supporting Evidence: PMID:38728140 Sep4 knockdown and Sep5 mutant embryos exhibit delayed actomyosin ring disassembly |
| GO:0031105 septin complex | IBA GO_REF:0000033 | ACCEPT | Summary: Septin complex membership inherited across the septin family. Reason: IBA from PANTHER node PTN000430171 with very broad donors, including all Drosophila septins in the curated set. Experimental evidence confirms membership of this subunit in a hetero-oligomeric septin complex. Supporting Evidence: PMID:38728140 Taken together, our findings further suggest that Sep1/Sep2/Pnut and Sep4/Sep5/Pnut are functioning as distinct complexes within the context of cell wound repair. |
| GO:0031105 septin complex | IEA GO_REF:0000104 | ACCEPT | Summary: Septin complex membership predicted by UniRule. Reason: Consistent with experimental data: this subunit assembles with Pnut and a SEPT2-/SEPT6-class partner into the Sep4/Sep5/Pnut complex. Supporting Evidence: PMID:38728140 Taken together, our findings further suggest that Sep1/Sep2/Pnut and Sep4/Sep5/Pnut are functioning as distinct complexes within the context of cell wound repair. |
| GO:0031105 septin complex | TAS PMID:38728140 Two Septin complexes mediate actin dynamics during cell woun... | ACCEPT | Summary: Subunit of the hetero-oligomeric septin complex. Reason: Direct biochemical evidence that this subunit assembles into a hetero-oligomeric septin complex (Sep1/Sep2/Pnut and/or Sep4/Sep5/Pnut). Core location. Supporting Evidence: PMID:38728140 Taken together, our findings further suggest that Sep1/Sep2/Pnut and Sep4/Sep5/Pnut are functioning as distinct complexes within the context of cell wound repair. |
| GO:0032153 cell division site | IBA GO_REF:0000033 | ACCEPT | Summary: Septins accumulate at the cell division site. Reason: IBA from PANTHER node PTN000430171 with broad donors. Sep4 localization during division has not been examined directly, but it is a SEPT2-class subunit like Sep1, which localizes to cleavage furrows. Supporting Evidence: PMID:38728140 Drosophila has 5 Septins that are grouped into three classes: Sep2 and Sep5 (SEPT6 class), Sep1 and Sep4 (SEPT2 class), and Pnut (SEPT7 class) |
| GO:0042060 wound healing | IMP PMID:38728140 Two Septin complexes mediate actin dynamics during cell woun... | ACCEPT | Summary: Septins are required for efficient cell wound repair. Reason: All five septins are required for efficient wound repair of the syncytial embryo; Sep1/Sep2 and Sep4/Sep5 loss give distinct actin-ring phenotypes. Direct IMP evidence; this is single-cell (plasma membrane/cortex) wound repair. Supporting Evidence: PMID:38728140 we show that all five Drosophila Septins are required for efficient cell wound repair PMID:38728140 Sep4 knockdown and Sep5 mutant embryos exhibit delayed actomyosin ring disassembly |
| GO:0042461 photoreceptor cell development | NAS PMID:8181057 The Drosophila peanut gene is required for cytokinesis and e... | MARK AS OVER ANNOTATED | Summary: Photoreceptor development inferred from a genetic interaction with seven in absentia. Reason: The only basis is a dominant genetic interaction between pnut and sina noted in PMID:8181057, which the authors interpret as possible pleiotropy. No septin was shown to act in photoreceptor development; for Sep1, Sep2 and Sep4 the NAS row simply extends this pnut observation to paralogs. Supporting Evidence: PMID:8181057 pnut displays genetic interactions with seven in absentia, a gene required for neuronal fate determination in the compound eye |
| GO:0044837 actomyosin contractile ring organization | IMP PMID:38728140 Two Septin complexes mediate actin dynamics during cell woun... | ACCEPT | Summary: Septins organise the actomyosin ring during single-cell wound repair. Reason: In the Drosophila embryo cell-wound model, knockdown or mutation of each septin perturbs actomyosin ring assembly, contraction or disassembly; the two complexes bend actin bundles to different curvatures. Core process for the septin complexes. Supporting Evidence: PMID:38728140 Sep4 knockdown and Sep5 mutant embryos exhibit delayed actomyosin ring disassembly PMID:38728140 Interestingly, we observe curved F-actin bundles induced by two separate Septin complexes, whereas individual Septins can only bind to and bundle F-actin. |
| GO:0051015 actin filament binding | IDA PMID:38728140 Two Septin complexes mediate actin dynamics during cell woun... | ACCEPT | Summary: Purified septin subunits and complexes bind and bundle actin filaments. Reason: Each of the five Drosophila septins, purified individually, binds and bundles F-actin in vitro, and the assembled Sep1/Sep2/Pnut and Sep4/Sep5/Pnut complexes additionally bend the bundles into rings. Direct F-actin binding is a core activity linking septins to the actomyosin cytoskeleton. Supporting Evidence: PMID:38728140 Strikingly, we find that all five Drosophila Septins can bind to and bundle actin filaments PMID:38728140 Interestingly, we observe curved F-actin bundles induced by two separate Septin complexes, whereas individual Septins can only bind to and bundle F-actin. |
| GO:0060090 molecular adaptor activity | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Septin filaments act as scaffolds that recruit other proteins. Reason: IBA from PANTHER node PTN000430171 with donors yeast Cdc3 and Cdc12 (SGD:S000000595, SGD:S000001149), where septin collars scaffold bud-neck proteins. Drosophila septins also act as cortical scaffolds (e.g. with Anillin), but the documented fly activities are actin filament binding and bundling; the generic adaptor term is retained as non-core. |
| GO:0061640 cytoskeleton-dependent cytokinesis | IBA GO_REF:0000033 | ACCEPT | Summary: Septin role in cytoskeleton-dependent cytokinesis inherited from the septin family. Reason: IBA from PANTHER node PTN000430171 with broad donors (yeast, fission yeast, mouse, worm and Drosophila septins, including Sep4 itself). Sep4 is a SEPT2-class subunit of the Sep4-Sep5-Pnut complex; its own role in mitotic cytokinesis is less characterised than that of Sep1, but there is no evidence of loss of this conserved function. Supporting Evidence: PMID:38728140 Taken together, our findings further suggest that Sep1/Sep2/Pnut and Sep4/Sep5/Pnut are functioning as distinct complexes within the context of cell wound repair. |
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