scattered (scat, CG3766) encodes the Drosophila ortholog of VPS54, the subunit that defines the Golgi-associated retrograde protein (GARP) tethering complex. Scat joins the Vps51-Vps52-Vps53 core shared with the EARP complex and targets it to the trans side of the Golgi, where GARP captures endosome-derived carriers carrying cargo such as the mannose-6-phosphate receptor homolog Lerp back to the trans-Golgi network. GARP is recruited to the TGN in part by the Arf-like GTPase Arl5. scat null males are completely sterile: in spermatids the trans side of the Golgi-derived acroblast is disrupted, the acrosome fails to form, nuclei fail to complete elongation and individualization of the spermatid cyst does not occur. In larval motor neurons scat is required for normal organization of the TGN syntaxin Syx16 and restrains neuromuscular junction growth, and in sensory neurons GARP loss causes free-sterol accumulation at the TGN and defective dendrite regrowth after pruning. In larval salivary gland cells, knockdown of scat or Vps53 leaves glue granules small and immature and sends them to early crinophagic degradation in lysosomes.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000138 Golgi trans cisterna | IDA PMID:27481842 The role of acroblast formation during Drosophila spermatoge... | ACCEPT | Summary: Scat-RFP localizes to the trans side of the Golgi in spermatocytes and spermatids. Reason: Direct localization of a functional (rescuing) Scat-RFP fusion. Supporting Evidence: PMID:27481842 We found that the Scat-RFP signal localized close but slightly displaced from dGM130 in all stages of spermatogenesis, suggesting that Scat is localized to the trans side of the Golgi |
| GO:0000938 GARP complex | IBA GO_REF:0000033 | ACCEPT | Summary: Scat/Vps54 is the defining subunit of the GARP tethering complex. Reason: Fly Vps54/Scat co-purifies with Vps51, Vps52 and Vps53 on GTP-locked Arl5, and a rescuing Scat-RFP transgene is incorporated into GARP. GARP membership is conserved from yeast to human (IBA/ISS donors yeast VPS54 and human VPS54 Q9P1Q0). Supporting Evidence: PMID:25795912 Amongst the more abundant proteins that bound specifically to Arl5-GTP were the Drosophila orthologues of the four subunits of the GARP complex (CG15087/Vps51, CG7371/Vps52, CG3338/Vps53, and CG3766/Vps54 or Scat) PMID:27481842 The Vps54 (Scat) protein, a subunit of the GARP tethering complex, is a central factor in retrograde transport to the trans-Golgi. |
| GO:0000938 GARP complex | IDA PMID:25795912 The small G protein Arl5 contributes to endosome-to-Golgi tr... | ACCEPT | Summary: Scat/Vps54 is the defining subunit of the GARP tethering complex. Reason: Fly Vps54/Scat co-purifies with Vps51, Vps52 and Vps53 on GTP-locked Arl5, and a rescuing Scat-RFP transgene is incorporated into GARP. GARP membership is conserved from yeast to human (IBA/ISS donors yeast VPS54 and human VPS54 Q9P1Q0). Supporting Evidence: PMID:25795912 Amongst the more abundant proteins that bound specifically to Arl5-GTP were the Drosophila orthologues of the four subunits of the GARP complex (CG15087/Vps51, CG7371/Vps52, CG3338/Vps53, and CG3766/Vps54 or Scat) PMID:27481842 The Vps54 (Scat) protein, a subunit of the GARP tethering complex, is a central factor in retrograde transport to the trans-Golgi. |
| GO:0000938 GARP complex | IEA GO_REF:0000002 | ACCEPT | Summary: Scat/Vps54 is the defining subunit of the GARP tethering complex. Reason: Fly Vps54/Scat co-purifies with Vps51, Vps52 and Vps53 on GTP-locked Arl5, and a rescuing Scat-RFP transgene is incorporated into GARP. GARP membership is conserved from yeast to human (IBA/ISS donors yeast VPS54 and human VPS54 Q9P1Q0). Supporting Evidence: PMID:25795912 Amongst the more abundant proteins that bound specifically to Arl5-GTP were the Drosophila orthologues of the four subunits of the GARP complex (CG15087/Vps51, CG7371/Vps52, CG3338/Vps53, and CG3766/Vps54 or Scat) PMID:27481842 The Vps54 (Scat) protein, a subunit of the GARP tethering complex, is a central factor in retrograde transport to the trans-Golgi. |
| GO:0000938 GARP complex | ISS GO_REF:0000024 | ACCEPT | Summary: Scat/Vps54 is the defining subunit of the GARP tethering complex. Reason: Fly Vps54/Scat co-purifies with Vps51, Vps52 and Vps53 on GTP-locked Arl5, and a rescuing Scat-RFP transgene is incorporated into GARP. GARP membership is conserved from yeast to human (IBA/ISS donors yeast VPS54 and human VPS54 Q9P1Q0). Supporting Evidence: PMID:25795912 Amongst the more abundant proteins that bound specifically to Arl5-GTP were the Drosophila orthologues of the four subunits of the GARP complex (CG15087/Vps51, CG7371/Vps52, CG3338/Vps53, and CG3766/Vps54 or Scat) PMID:27481842 The Vps54 (Scat) protein, a subunit of the GARP tethering complex, is a central factor in retrograde transport to the trans-Golgi. |
| GO:0000938 GARP complex | NAS PMID:25453831 Toward a comprehensive map of the effectors of rab GTPases. | ACCEPT | Summary: Scat/Vps54 is the defining subunit of the GARP tethering complex. Reason: Fly Vps54/Scat co-purifies with Vps51, Vps52 and Vps53 on GTP-locked Arl5, and a rescuing Scat-RFP transgene is incorporated into GARP. GARP membership is conserved from yeast to human (IBA/ISS donors yeast VPS54 and human VPS54 Q9P1Q0). Supporting Evidence: PMID:25795912 Amongst the more abundant proteins that bound specifically to Arl5-GTP were the Drosophila orthologues of the four subunits of the GARP complex (CG15087/Vps51, CG7371/Vps52, CG3338/Vps53, and CG3766/Vps54 or Scat) PMID:27481842 The Vps54 (Scat) protein, a subunit of the GARP tethering complex, is a central factor in retrograde transport to the trans-Golgi. |
| GO:0000938 GARP complex | NAS PMID:25795912 The small G protein Arl5 contributes to endosome-to-Golgi tr... | ACCEPT | Summary: Scat/Vps54 is the defining subunit of the GARP tethering complex. Reason: Fly Vps54/Scat co-purifies with Vps51, Vps52 and Vps53 on GTP-locked Arl5, and a rescuing Scat-RFP transgene is incorporated into GARP. GARP membership is conserved from yeast to human (IBA/ISS donors yeast VPS54 and human VPS54 Q9P1Q0). Supporting Evidence: PMID:25795912 Amongst the more abundant proteins that bound specifically to Arl5-GTP were the Drosophila orthologues of the four subunits of the GARP complex (CG15087/Vps51, CG7371/Vps52, CG3338/Vps53, and CG3766/Vps54 or Scat) PMID:27481842 The Vps54 (Scat) protein, a subunit of the GARP tethering complex, is a central factor in retrograde transport to the trans-Golgi. |
| GO:0001675 acrosome assembly | IMP PMID:27481842 The role of acroblast formation during Drosophila spermatoge... | KEEP AS NON CORE | Summary: scat mutant spermatids fail to form an acrosome. Reason: The acrosome derives from the Golgi-based acroblast, whose trans side is disrupted when GARP-mediated retrograde retrieval is lost. Real, specific phenotype, but a tissue-level consequence of the core trafficking role. Supporting Evidence: PMID:27481842 This acrosome formation defect was due to a fault in the trans-Golgi side of the acroblast ribbon. |
| GO:0005737 cytoplasm | IEA GO_REF:0000117 | MODIFY | Summary: Generic cytoplasm location from an ARBA rule. Reason: Correct but much less specific than the evidence supports: Scat is a peripheral subunit of a Golgi tethering complex localized to the trans side of the Golgi. The more specific term Golgi trans cisterna (GO:0000138) is already annotated to scat by IDA (PMID:27481842). Proposed replacements: Golgi trans cisterna Supporting Evidence: PMID:27481842 suggesting that Scat is localized to the trans side of the Golgi |
| GO:0005794 Golgi apparatus | IEA GO_REF:0000044 | MODIFY | Summary: Golgi localization; correct but less specific than the trans-Golgi location. Reason: A rescuing Scat-RFP localizes to the trans side of the Golgi; the more specific term Golgi trans cisterna (GO:0000138) is already annotated to scat by IDA (PMID:27481842) and should replace the generic Golgi apparatus term. Proposed replacements: Golgi trans cisterna Supporting Evidence: PMID:27481842 suggesting that Scat is localized to the trans side of the Golgi |
| GO:0005794 Golgi apparatus | ISS GO_REF:0000024 | MODIFY | Summary: Golgi localization; correct but less specific than the trans-Golgi location. Reason: A rescuing Scat-RFP localizes to the trans side of the Golgi; the more specific term Golgi trans cisterna (GO:0000138) is already annotated to scat by IDA (PMID:27481842) and should replace the generic Golgi apparatus term. Proposed replacements: Golgi trans cisterna Supporting Evidence: PMID:27481842 suggesting that Scat is localized to the trans side of the Golgi |
| GO:0005829 cytosol | IEA GO_REF:0000108 | KEEP AS NON CORE | Summary: Cytosolic pool of a peripheral membrane complex. Reason: GARP subunits cycle between membrane-bound and cytosolic pools (human VPS54 becomes cytosolic when Arl5b is depleted); the functional location is the trans-Golgi, so cytosol is non-core. Inferred from the process annotation (GO_REF:0000108). |
| GO:0006896 Golgi to vacuole transport | ISS GO_REF:0000024 | MARK AS OVER ANNOTATED | Summary: Golgi-to-vacuole transport transferred from yeast Vps54. Reason: Yeast GARP mutants missort vacuolar hydrolases because the sorting receptor is not retrieved from endosomes to the late Golgi; the forward Golgi-to-vacuole transport step is performed by other machinery. For a metazoan Vps54 the direct process is retrograde endosome-to-Golgi transport (GO:0042147). ISS from yeast VPS54 (Q12071). |
| GO:0007290 spermatid nucleus elongation | IMP PMID:27481842 The role of acroblast formation during Drosophila spermatoge... | KEEP AS NON CORE | Summary: scat mutant spermatid nuclei fail to complete elongation. Reason: Developmental consequence of the Golgi/acroblast defect in spermatids, not a core activity of Scat. Supporting Evidence: PMID:27481842 Investigating the elongating spermatid nuclei their majority were found in late canoe stage and hardly any were observed as needle shaped in the scat1 mutant cysts |
| GO:0007291 sperm individualization | IMP PMID:9550716 Genetic dissection of sperm individualization in Drosophila ... | KEEP AS NON CORE | Summary: scat mutants fail in spermatid individualization. Reason: scat was isolated as a male-sterile individualization mutant; null scat1 spermatids form hardly any investment cones and do not individualize. Downstream developmental consequence of the Golgi trafficking defect. Supporting Evidence: PMID:27481842 In the case of the scat1 mutant we observed hardly any investment cones and the process of individualization did not start. PMID:27481842 We found the scat(1) mutant to be male sterile in Drosophila with individualization problems occurring during spermatogenesis. |
| GO:0019905 syntaxin binding | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Syntaxin binding inferred phylogenetically. Reason: GARP subunits engage Golgi SNAREs (syntaxins) as part of tethering in yeast and mammals; plausible but untested for fly Scat, and better represented by the complex's tethering activity. IBA donor C. elegans vps-54 (WBGene00006934). |
| GO:0032456 endocytic recycling | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Endocytic recycling is principally an EARP (Vps50) function; Vps54 makes a minor contribution. Reason: Recycling to the plasma membrane is mediated mainly by EARP, which contains Vps50 in place of Vps54. In human cells VPS54 knockdown also delayed transferrin recycling, but to a lesser extent than syndetin knockdown, so a minor or indirect role is plausible. The IBA has only fly scat itself (FB:FBgn0011232, from the IDA above) as donor, so it inherits the weakness of that row. Supporting Evidence: PMID:25799061 Vps54 KD also delayed Tf-Alexa568 recycling, albeit to a lesser extent (t1/2=11 min) |
| GO:0032456 endocytic recycling | IDA PMID:25795912 The small G protein Arl5 contributes to endosome-to-Golgi tr... | MODIFY | Summary: The cited fly study supports endosome-to-Golgi traffic, not recycling to the plasma membrane. Reason: PMID:25795912 shows that Arl5 binds the four GARP subunits including Scat and aids GARP recruitment to the TGN, with phenotypes consistent with an endosome-to-Golgi defect; it does not assay recycling of internalized cargo to the plasma membrane (GO:0032456). The process supported is retrograde transport, endosome to Golgi. Proposed replacements: retrograde transport, endosome to Golgi Supporting Evidence: PMID:25795912 These phenotypes are consistent with a role in endosome-to-Golgi traffic, but are less severe than loss of GARP itself. |
| GO:0032456 endocytic recycling | NAS PMID:25795912 The small G protein Arl5 contributes to endosome-to-Golgi tr... | KEEP AS NON CORE | Summary: Endocytic recycling is principally an EARP (Vps50) function; Vps54 makes a minor contribution. Reason: Recycling to the plasma membrane is mediated mainly by EARP, which contains Vps50 in place of Vps54. In human cells VPS54 knockdown also delayed transferrin recycling, but to a lesser extent than syndetin knockdown, so a minor or indirect role is plausible. The IBA has only fly scat itself (FB:FBgn0011232, from the IDA above) as donor, so it inherits the weakness of that row. Supporting Evidence: PMID:25799061 Vps54 KD also delayed Tf-Alexa568 recycling, albeit to a lesser extent (t1/2=11 min) |
| GO:0042147 retrograde transport, endosome to Golgi | IBA GO_REF:0000033 | ACCEPT | Summary: Scat/Vps54-containing GARP tethers endosome-derived vesicles at the TGN. Reason: Core process. In scat1 mutant spermatids the M6PR homolog Lerp no longer co-localizes with the trans-Golgi marker Golgin245, showing a defect in endosome-to-Golgi retrieval. Supporting Evidence: PMID:27481842 a failure in acrosome formation and endosome-Golgi vesicular transport were found in the scat(1) mutant PMID:27481842 The trans-Golgi marker Golgin245 showed co-localization with GFP-Lerp in WT, but not in the scat1 mutant postmeiotic round spermatids |
| GO:0042147 retrograde transport, endosome to Golgi | IEA GO_REF:0000002 | ACCEPT | Summary: Scat/Vps54-containing GARP tethers endosome-derived vesicles at the TGN. Reason: Core process. In scat1 mutant spermatids the M6PR homolog Lerp no longer co-localizes with the trans-Golgi marker Golgin245, showing a defect in endosome-to-Golgi retrieval. Supporting Evidence: PMID:27481842 a failure in acrosome formation and endosome-Golgi vesicular transport were found in the scat(1) mutant PMID:27481842 The trans-Golgi marker Golgin245 showed co-localization with GFP-Lerp in WT, but not in the scat1 mutant postmeiotic round spermatids |
| GO:0042147 retrograde transport, endosome to Golgi | ISS GO_REF:0000024 | ACCEPT | Summary: Scat/Vps54-containing GARP tethers endosome-derived vesicles at the TGN. Reason: Core process. In scat1 mutant spermatids the M6PR homolog Lerp no longer co-localizes with the trans-Golgi marker Golgin245, showing a defect in endosome-to-Golgi retrieval. Supporting Evidence: PMID:27481842 a failure in acrosome formation and endosome-Golgi vesicular transport were found in the scat(1) mutant PMID:27481842 The trans-Golgi marker Golgin245 showed co-localization with GFP-Lerp in WT, but not in the scat1 mutant postmeiotic round spermatids |
| GO:0042147 retrograde transport, endosome to Golgi | NAS PMID:25795912 The small G protein Arl5 contributes to endosome-to-Golgi tr... | ACCEPT | Summary: Scat/Vps54-containing GARP tethers endosome-derived vesicles at the TGN. Reason: Core process. In scat1 mutant spermatids the M6PR homolog Lerp no longer co-localizes with the trans-Golgi marker Golgin245, showing a defect in endosome-to-Golgi retrieval. Supporting Evidence: PMID:27481842 a failure in acrosome formation and endosome-Golgi vesicular transport were found in the scat(1) mutant PMID:27481842 The trans-Golgi marker Golgin245 showed co-localization with GFP-Lerp in WT, but not in the scat1 mutant postmeiotic round spermatids |
| GO:7770062 vesicle membrane tethering activity | TAS PMID:25795912 The small G protein Arl5 contributes to endosome-to-Golgi tr... | NEW | Summary: Scat/Vps54 contributes to the vesicle-tethering activity of the GARP complex. Reason: GARP is a multisubunit tethering complex that captures endosome-derived vesicles at the TGN; Scat/Vps54 is a subunit, so the activity is recorded as contributes_to. This matches the replacement used for the ND molecular_function rows of Vps50, Vps51 and Vps53, and the core function already uses this term. Supporting Evidence: PMID:25795912 complex that acts in the tethering of vesicles moving from endosomes to the trans-Golgi network (TGN) |
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Download this section (compressed HTML)Q: Why is scat loss largely restricted to a male-sterile phenotype in flies, whereas GARP loss is lethal or neurodegenerative in other animals (e.g. the wobbler mouse Vps54 allele)? Is there redundancy with EARP or other retrograde pathways in somatic fly tissues?
Experiment: Examine somatic tissues (neurons, fat body, salivary gland) of scat1 null animals for Lerp missorting and lysosomal hydrolase secretion, and test genetic interaction with Vps50.
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Download this section (compressed HTML)scattered (scat) encodes a component of the Golgi-Associated Retrograde Protein (GARP) complex and is required for spermatid development. It is important for secretory granule maturation and for preventing early degradation of these granules.
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