TRAPPC3 is the human Bet3 homolog and a core TRAPP-complex subunit. It contributes to complex-level RAB1 guanine-nucleotide exchange factor activity, TRAPP/TRAPPII/TRAPPIII complex architecture, and ER-to-Golgi vesicle-mediated transport. Autophagophore-recruitment effects are best understood through TRAPP complex membership and TRAPPIII/RAB1 context rather than independent TRAPPC3-specific autophagy activity.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005085 guanyl-nucleotide exchange factor activity | IBA GO_REF:0000033 | ACCEPT | Summary: TRAPPC3 contributes to complex-level RAB1 guanine-nucleotide exchange factor activity as a TRAPP subunit. Reason: Accept with the contributes_to qualifier. The TRAPPC complex, not isolated TRAPPC3, provides the GEF activity for RAB1/Ypt1-family GTPases. Supporting Evidence: Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III PMID:21525244 the complex acts as a guanine nucleotide exchange factor (GEF) for Ypt1p |
| GO:0005829 cytosol | IBA GO_REF:0000033 | ACCEPT | Summary: TRAPPC3-containing TRAPP reactions occur on the cytosolic/cytoplasmic side of ER-Golgi trafficking membranes. Reason: Accept as supported location for a peripheral trafficking-complex subunit. Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III |
| GO:0006888 endoplasmic reticulum to Golgi vesicle-mediated transport | IBA GO_REF:0000033 | ACCEPT | Summary: TRAPPC3-containing TRAPP complexes mediate ER-to-Golgi vesicle traffic through TRAPP/RAB1 biology. Reason: Accept as a core process for TRAPPC3. Multiple human/mammalian TRAPP sources and Reactome support ER-to-Golgi trafficking. Supporting Evidence: PMID:18930054 The transport protein particle (TRAPP) complex is required for proper vesicular transport from the ER to the Golgi PMID:21525244 C4orf41 and TTC-15 (which we call TRAPPC11 and TRAPPC12, respectively) in ER-to-Golgi trafficking at a very early stage Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it |
| GO:0006891 intra-Golgi vesicle-mediated transport | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Intra-Golgi transport is plausible through TRAPPII/Golgi trafficking context but is less central than ER-to-Golgi transport for human TRAPPC3. Reason: Keep as non-core. The TRAPPII/Golgi evidence supports a context-specific trafficking role, while the core TRAPPC3 process remains ER-to-Golgi/TRAPP/RAB1 transport. Supporting Evidence: PMID:21453443 for distinct tethering events at Golgi membranes PMID:18930054 different functions in the regulation of ER-to-Golgi traffic |
| GO:0030008 TRAPP complex | IBA GO_REF:0000033 | ACCEPT | Summary: TRAPPC3/Bet3 is a core TRAPP complex subunit. Reason: Accept as core cellular-component membership. This is the cleanest gene-level representation of the PN TRAPP component leaf. Supporting Evidence: PMID:16828797 crystal structure of a human Bet3-Tpc6B heterodimer, which represents a core sub-complex in the assembly of TRAPP PMID:16828797 Bet3-Tpc6A and Bet3-Tpc6B, are able to recruit Mum2, a further TRAPP subunit PMID:21525244 the mammalian orthologues named TRAPPC1, TRAPPC2, TRAPPC3, TRAPPC4, TRAPPC5, and TRAPPC6a/b |
| GO:0033106 cis-Golgi network membrane | IBA GO_REF:0000033 | ACCEPT | Summary: cis-Golgi network membrane is a supported active site for TRAPPC3-containing TRAPP complexes. Reason: Accept as a supported active location for TRAPP/RAB1 ER-to-Golgi trafficking. Supporting Evidence: PMID:18930054 The transport protein particle (TRAPP) complex is required for proper vesicular transport from the ER to the Golgi Reactome:R-HSA-5694439 TRAPPC is a guanine-nucleotide exchange factor for RAB1 and is recruited to ER-derived vesicles by virtue of an interaction between the TRAPPC component TRAPPC3 and the coat protein SEC23 |
| GO:0005783 endoplasmic reticulum | IEA GO_REF:0000044 | ACCEPT | Summary: TRAPPC3 participates in ER-derived vesicle trafficking and is mapped to the endoplasmic reticulum. Reason: Accept as a supported location for ER-to-Golgi trafficking. ORGANELLES check (2026-11-06): the IEA comes from the UniProt location "Endoplasmic reticulum {ECO:0000250}", a by-similarity line, but the claim holds on mammalian evidence. Endogenous mBet3p (TRAPPC3) was immunolocalized with the COPII marker Sec31p, clustered with ER exit sites under Sar1p H79G, and by immuno-EM was concentrated 7.6-22-fold on Sec31p-labelled transitional ER over other ER (PMID:16880271); the TRAPPC12 paper summarises that TRAPPC3 localizes to the transitional ER (PMID:21525244). Most Bet3 is cytosolic (PMID:15728249), so the ER pool is a recruited membrane-bound pool on the cytosolic face, not a membrane or lumen resident, and no ER membrane or lumen row is added. The ER exit site, where the COPII-vesicle tethering function is exercised, is added as a NEW row (GO:0070971). Kept ACCEPT because the core tethering/RAB1 GEF function is exercised there. Supporting Evidence: PMID:18930054 The transport protein particle (TRAPP) complex is required for proper vesicular transport from the ER to the Golgi Reactome:R-HSA-5694439 TRAPPC is a guanine-nucleotide exchange factor for RAB1 and is recruited to ER-derived vesicles by virtue of an interaction between the TRAPPC component TRAPPC3 and the coat protein SEC23 PMID:16880271 Immuno-EM in NRK cells confirmed that mBet3p (5-nm gold particles) resides on the tER region labeled with Sec31p (10-nm gold particles). PMID:21525244 C3, a core component of the complex, localizes to the transitional ER |
| GO:0005794 Golgi apparatus | IEA GO_REF:0000044 | ACCEPT | Summary: TRAPPC3 functions in TRAPP trafficking at Golgi/cis-Golgi membranes. Reason: Accept as supported location for TRAPP-mediated ER-to-Golgi and Golgi trafficking. Supporting Evidence: PMID:18930054 The transport protein particle (TRAPP) complex is required for proper vesicular transport from the ER to the Golgi PMID:21453443 for distinct tethering events at Golgi membranes PMID:18930054 different functions in the regulation of ER-to-Golgi traffic |
| GO:0030008 TRAPP complex | IEA GO_REF:0000120 | ACCEPT | Summary: TRAPPC3/Bet3 is a core TRAPP complex subunit. Reason: Accept as core cellular-component membership. This is the cleanest gene-level representation of the PN TRAPP component leaf. Supporting Evidence: PMID:16828797 crystal structure of a human Bet3-Tpc6B heterodimer, which represents a core sub-complex in the assembly of TRAPP PMID:16828797 Bet3-Tpc6A and Bet3-Tpc6B, are able to recruit Mum2, a further TRAPP subunit PMID:21525244 the mammalian orthologues named TRAPPC1, TRAPPC2, TRAPPC3, TRAPPC4, TRAPPC5, and TRAPPC6a/b |
| GO:0048193 Golgi vesicle transport | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Golgi vesicle transport is a broad trafficking context supported by TRAPP/TRAPPII biology. Reason: Keep as non-core because it is broader/less precise than ER-to-Golgi vesicle-mediated transport and intra-Golgi TRAPPII context. Supporting Evidence: PMID:21453443 for distinct tethering events at Golgi membranes PMID:18930054 different functions in the regulation of ER-to-Golgi traffic |
| GO:0005515 protein binding | IPI PMID:16189514 Towards a proteome-scale map of the human protein-protein in... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:16828797 Structure of the Bet3-Tpc6B core of TRAPP: two Tpc6 paralogs... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:16908848 Unique self-palmitoylation activity of the transport protein... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:18930054 Distinct isocomplexes of the TRAPP trafficking factor coexis... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:21453443 Organization and assembly of the TRAPPII complex. | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:21827752 A yeast two hybrid screen identifies SPATA4 as a TRAPP inter... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:25416956 A proteome-scale map of the human interactome network. | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:28514442 Architecture of the human interactome defines protein commun... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:31515488 Extensive disruption of protein interactions by genetic vari... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0005515 protein binding | IPI PMID:35271311 OpenCell: Endogenous tagging for the cartography of human ce... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0000139 Golgi membrane | IEA GO_REF:0000107 | ACCEPT | Summary: Golgi membrane localization is consistent with TRAPPC3/Bet3 role in TRAPP trafficking complexes. Reason: Accept as a more specific Golgi location for the TRAPP trafficking role. Supporting Evidence: PMID:21453443 for distinct tethering events at Golgi membranes PMID:18930054 different functions in the regulation of ER-to-Golgi traffic |
| GO:0005829 cytosol | IEA GO_REF:0000107 | ACCEPT | Summary: TRAPPC3-containing TRAPP reactions occur on the cytosolic/cytoplasmic side of ER-Golgi trafficking membranes. Reason: Accept as supported location for a peripheral trafficking-complex subunit. Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III |
| GO:0005737 cytoplasm | NAS PMID:27066478 TRAPP Complexes in Secretion and Autophagy. | ACCEPT | Summary: TRAPPC3-containing TRAPP reactions occur on the cytosolic/cytoplasmic side of ER-Golgi trafficking membranes. Reason: Accept as supported location for a peripheral trafficking-complex subunit. Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III |
| GO:0006888 endoplasmic reticulum to Golgi vesicle-mediated transport | NAS PMID:27066478 TRAPP Complexes in Secretion and Autophagy. | ACCEPT | Summary: TRAPPC3-containing TRAPP complexes mediate ER-to-Golgi vesicle traffic through TRAPP/RAB1 biology. Reason: Accept as a core process for TRAPPC3. Multiple human/mammalian TRAPP sources and Reactome support ER-to-Golgi trafficking. Supporting Evidence: PMID:18930054 The transport protein particle (TRAPP) complex is required for proper vesicular transport from the ER to the Golgi PMID:21525244 C4orf41 and TTC-15 (which we call TRAPPC11 and TRAPPC12, respectively) in ER-to-Golgi trafficking at a very early stage Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it |
| GO:0006901 vesicle coat assembly | NAS PMID:27066478 TRAPP Complexes in Secretion and Autophagy. | MODIFY | Summary: TRAPPC3 interacts with COPII/SEC23-associated ER-derived vesicle trafficking machinery, but it is not a vesicle coat assembly factor. Reason: Modify to ER-to-Golgi vesicle-mediated transport to capture the supported trafficking role without overclaiming coat assembly. Proposed replacements: endoplasmic reticulum to Golgi vesicle-mediated transport Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a guanine-nucleotide exchange factor for RAB1 and is recruited to ER-derived vesicles by virtue of an interaction between the TRAPPC component TRAPPC3 and the coat protein SEC23 Reactome:R-HSA-8877475 TRAPPCII is recruited to ER-derived vesicles by virtue of an interaction between the TRAPPCII component TRAPPC3 and the COPII coat protein SEC23 |
| GO:0048208 COPII vesicle coat assembly | NAS PMID:27066478 TRAPP Complexes in Secretion and Autophagy. | MODIFY | Summary: The COPII evidence supports TRAPPC3-SEC23 recruitment to ER-derived vesicles, not direct COPII coat assembly by TRAPPC3. Reason: Modify to ER-to-Golgi vesicle-mediated transport. Proposed replacements: endoplasmic reticulum to Golgi vesicle-mediated transport Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a guanine-nucleotide exchange factor for RAB1 and is recruited to ER-derived vesicles by virtue of an interaction between the TRAPPC component TRAPPC3 and the coat protein SEC23 Reactome:R-HSA-8877475 TRAPPCII is recruited to ER-derived vesicles by virtue of an interaction between the TRAPPCII component TRAPPC3 and the COPII coat protein SEC23 |
| GO:0099022 obsolete vesicle tethering | NAS PMID:27066478 TRAPP Complexes in Secretion and Autophagy. | MODIFY | Summary: This obsolete vesicle-tethering annotation should not be kept as-is, and direct mammalian TRAPP tethering evidence remains unresolved. Reason: Modify to ER-to-Golgi vesicle-mediated transport, the safer supported TRAPPC3 process. Proposed replacements: endoplasmic reticulum to Golgi vesicle-mediated transport Supporting Evidence: PMID:27066478 evidence that any TRAPP complex acts as a membrane tether is currently inconclusive PMID:21525244 Direct demonstration of mammalian TRAPP as a vesicle tether has yet to be shown Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic |
| GO:1990071 TRAPPII protein complex | NAS PMID:27066478 TRAPP Complexes in Secretion and Autophagy. | ACCEPT | Summary: TRAPPC3 is represented in TRAPPII complex models and ComplexPortal annotations. Reason: Accept as supported TRAPP subtype membership; process-level claims should remain tied to TRAPP/RAB1 trafficking. Supporting Evidence: PMID:21453443 for distinct tethering events at Golgi membranes Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III |
| GO:1990072 TRAPPIII protein complex | NAS PMID:27066478 TRAPP Complexes in Secretion and Autophagy. | ACCEPT | Summary: TRAPPC3 is represented in TRAPPIII complex models, which are relevant to the PN autophagy-recruitment context. Reason: Accept as supported complex membership while keeping autophagy as context rather than assigning a broad autophagy BP. Supporting Evidence: Reactome:R-HSA-8877475 RAB1 and the TRAPPCIII complex play a role in the formation of the pre-autophagosomal structure (PAS) and contribute to the localization of ATG9 PMID:27066478 the connection of the mammalian TRAPP III complex to autophagy is currently not clear |
| GO:0005515 protein binding | IPI PMID:21525244 C4orf41 and TTC-15 are mammalian TRAPP components with a rol... | MARK AS OVER ANNOTATED | Summary: Generic protein binding is not informative for TRAPPC3. Reason: Mark as over-annotated. Specific interaction biology should be represented as TRAPP/TRAPPII/TRAPPIII complex membership and TRAPP/RAB1 trafficking context, not generic GO:0005515. |
| GO:0030008 TRAPP complex | IDA PMID:21525244 C4orf41 and TTC-15 are mammalian TRAPP components with a rol... | ACCEPT | Summary: TRAPPC3/Bet3 is a core TRAPP complex subunit. Reason: Accept as core cellular-component membership. This is the cleanest gene-level representation of the PN TRAPP component leaf. Supporting Evidence: PMID:16828797 crystal structure of a human Bet3-Tpc6B heterodimer, which represents a core sub-complex in the assembly of TRAPP PMID:16828797 Bet3-Tpc6A and Bet3-Tpc6B, are able to recruit Mum2, a further TRAPP subunit PMID:21525244 the mammalian orthologues named TRAPPC1, TRAPPC2, TRAPPC3, TRAPPC4, TRAPPC5, and TRAPPC6a/b |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5694409 | ACCEPT | Summary: TRAPPC3-containing TRAPP reactions occur on the cytosolic/cytoplasmic side of ER-Golgi trafficking membranes. Reason: Accept as supported location for a peripheral trafficking-complex subunit. Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5694418 | ACCEPT | Summary: TRAPPC3-containing TRAPP reactions occur on the cytosolic/cytoplasmic side of ER-Golgi trafficking membranes. Reason: Accept as supported location for a peripheral trafficking-complex subunit. Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5694439 | ACCEPT | Summary: TRAPPC3-containing TRAPP reactions occur on the cytosolic/cytoplasmic side of ER-Golgi trafficking membranes. Reason: Accept as supported location for a peripheral trafficking-complex subunit. Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5694441 | ACCEPT | Summary: TRAPPC3-containing TRAPP reactions occur on the cytosolic/cytoplasmic side of ER-Golgi trafficking membranes. Reason: Accept as supported location for a peripheral trafficking-complex subunit. Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III |
| GO:0005829 cytosol | TAS Reactome:R-HSA-8877475 | ACCEPT | Summary: TRAPPC3-containing TRAPP reactions occur on the cytosolic/cytoplasmic side of ER-Golgi trafficking membranes. Reason: Accept as supported location for a peripheral trafficking-complex subunit. Supporting Evidence: Reactome:R-HSA-5694439 TRAPPC is a multi-subunit tethering complex that facilitates ER-to-Golgi traffic Reactome:R-HSA-5694409 The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it Reactome:R-HSA-8877475 RAB1 nucleotide exchange is stimulated in these pathways by the GEF activity of the multisubunit TRAPPC complexes II and III |
| GO:0070971 endoplasmic reticulum exit site | IC PMID:16880271 mBet3p is required for homotypic COPII vesicle tethering in ... | NEW | Summary: NEW (ORGANELLES, 2026-11-06). The ER pool of TRAPPC3/Bet3 sits at ER exit sites (transitional ER), where TRAPP tethers COPII vesicles; this sub-compartment is added beside the root ER row, which is kept. Reason: Two independent lines agree. (1) Localization: endogenous mammalian mBet3p overlaps the COPII marker Sec31p, its localization is BFA-resistant and clusters with ER exit sites under Sar1p H79G, and immuno-EM places it on Sec31p-labelled transitional ER at 7.6-22-fold higher density than over the rest of the ER (PMID:16880271, NRK and BSC-1 cells; the antibody is to mammalian Bet3, so this is ortholog-level for human TRAPPC3, which is why the row is IC). (2) Mechanism: TRAPPC3 is the subunit that recruits TRAPP to ER-derived COPII vesicles by binding the coat protein SEC23 (Reactome:R-HSA-5694439), a function that only makes sense at the ER exit site; comparator COPII components (SEC23A, SEC31A, SAR1A) carry GO:0070971 in GOA. TRAPPC3 is peripheral (most of it is cytosolic, PMID:15728249), so neither ER membrane nor ER lumen is asserted. core_functions is left unchanged (rule 6). Supporting Evidence: PMID:16880271 Unlike Man II and GM130, mBet3p always clustered with the ER exit sites PMID:16880271 The observed localization of mBet3p to the tER was significant, as quantitation revealed that the labeling density of mBet3p at the tER was 7.6–22 times higher than the labeling density of mBet3p over the ER and other organelles Reactome:R-HSA-5694439 TRAPPC is a guanine-nucleotide exchange factor for RAB1 and is recruited to ER-derived vesicles by virtue of an interaction between the TRAPPC component TRAPPC3 and the coat protein SEC23 PMID:15728249 In contrast to yeast Bet3p, the majority of Bet3 is present in the cytosol. |
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Download this section (compressed HTML)Q: Should TRAPPC3 and related TRAPP core subunits retain contributes_to RAB1 GEF annotations even when the complex-level catalytic subunit assignment is not fully resolved?
Suggested experts: GO transport editors, Reactome TRAPP curators
Q: Should TRAPPIII complex membership be considered sufficient for PN autophagophore-recruitment context without assigning broad autophagy process terms?
Suggested experts: GO autophagy editors, ComplexPortal curators
Q: Should TRAPPC3 coat-assembly annotations be replaced by ER-to-Golgi vesicle-mediated transport or by a more specific TRAPPC/COPII recruitment term if one exists?
Suggested experts: GO transport editors, ComplexPortal curators
Experiment: Reconstitute TRAPPC3-containing TRAPP complexes and measure RAB1 GDP-GTP exchange with TRAPPC3 depletion/rescue or interface mutants.
Hypothesis: TRAPPC3 is required as a core TRAPP subunit for complex-level RAB1 GEF activity.
Type: complex reconstitution and RAB1 GEF assay
Experiment: Test TRAPPC3 mutants that disrupt TRAPPC6/TRAPPC1 interfaces for effects on ER-to-Golgi cargo trafficking, SEC23/COPII association, and Golgi membrane recruitment.
Hypothesis: TRAPPC3 scaffolding of core TRAPP interactions is required for ER-to-Golgi vesicle-mediated transport.
Type: trafficking rescue and complex-interface assay
Experiment: Separate TRAPPII and TRAPPIII pools in TRAPPC3 rescue cells and assay ATG9 localization plus canonical ER-to-Golgi transport in parallel.
Hypothesis: TRAPPC3 autophagy phenotypes depend on TRAPPIII/RAB1 context and should be distinguished from core ER-to-Golgi transport defects.
Type: TRAPP subtype-specific autophagy/traffic assay
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