# TRAPPC3 notes Review started from `just fetch-gene human TRAPPC3`. The proteostasis network places TRAPPC3 under `Autophagy-Lysosome Pathway > Autophagophore initiation and elongation > Autophagy component recruitment to autophagophore > TRAPP complex component`, the same PN leaf as TRAPPC1. Falcon deep research was requested with `just deep-research-falcon human TRAPPC3`; the provider timed out after 600 seconds and no Falcon research file was generated. TRAPPC3 is the human Bet3 homolog and a core TRAPP complex subunit. UniProt states that TRAPPC3 is a component of the multisubunit TRAPP complex and that TRAPPC6B-TRAPPC3 interacts with TRAPPC1, likely providing a core for TRAPP complex formation. The TRAPPC1/TRAPPC3/TRAPPC6B structural paper reports the "crystal structure of a human Bet3-Tpc6B heterodimer" as a "core sub-complex in the assembly of TRAPP" and says Bet3-Tpc6A/Bet3-Tpc6B can recruit Mum2/TRAPPC1 [PMID:16828797 "Structure of the Bet3-Tpc6B core of TRAPP: two Tpc6 paralogs form trimeric complexes with Bet3 and Mum2."]. This supports TRAPP complex membership and specific TRAPP-subunit interactions; generic protein binding should still be treated as over-annotated. TRAPPC3 has stronger direct support than TRAPPC1 for contributing to complex-level RAB1 GEF/transport functions. The seeded GOA includes `GO:0005085 guanyl-nucleotide exchange factor activity` with qualifier `contributes_to`, which is appropriate because TRAPPC3 is a subunit of the TRAPPC complex rather than an independent RAB1 GEF. Reactome states that "The TRAPPC complex acts as a guanine-nucleotide exchange factor for RAB1, activating it" [Reactome:R-HSA-5694409 "Nucleotide exchange on RAB1"] and that "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-5694439 "COPII coat binds TRAPPCII and RAB1:GDP"]. This makes `contributes_to` GEF activity and ER-to-Golgi trafficking core. The main process role is ER-to-Golgi vesicle-mediated transport, with some TRAPPII/intra-Golgi context. A human TRAPP isocomplex paper says "The transport protein particle (TRAPP) complex is required for proper vesicular transport from the ER to the Golgi" and describes human TRAPP isocomplexes that may regulate ER-to-Golgi traffic [PMID:18930054 "Distinct isocomplexes of the TRAPP trafficking factor coexist inside human cells."]. A mammalian TRAPP component paper states that "TRAPP is a multisubunit tethering complex implicated in multiple vesicle trafficking pathways" and identifies mammalian TRAPP components with roles "in ER-to-Golgi trafficking at a very early stage" [PMID:21525244 "C4orf41 and TTC-15 are mammalian TRAPP components with a role at an early stage in ER-to-Golgi trafficking."]. A TRAPPII assembly abstract says TRAPPII is required "for distinct tethering events at Golgi membranes" [PMID:21453443 "Organization and assembly of the TRAPPII complex."]. ER-to-Golgi transport is core; intra-Golgi/Golgi vesicle transport is plausible but should be non-core or lower confidence unless the evidence specifically supports TRAPPII late Golgi activity in human cells. The PN autophagy context should be curated as complex membership, not a broad autophagy BP. The PN mapping rationale says the TRAPP component leaf is autophagy-contextual but that shared gene-level semantics are captured by TRAPP complex membership [projects/PROTEOSTASIS/reports/pn_projection/pn_projected_annotations.tsv]. Reactome says in macroautophagy "RAB1 and the TRAPPCIII complex play a role in the formation of the pre-autophagosomal structure (PAS) and contribute to the localization of ATG9" [Reactome:R-HSA-8877475 "TRAPPC complexes exchange GTP for GDP on RAB1"], but the TRAPP review cautions that "the connection of the mammalian TRAPP III complex to autophagy is currently not clear" [PMID:27066478 "TRAPP Complexes in Secretion and Autophagy."]. Do not add a broad autophagy process annotation for TRAPPC3 based only on the PN context. The coat-assembly and obsolete tethering annotations need revision. Reactome supports TRAPPC3/SEC23 interaction and TRAPPCII recruitment to ER-derived vesicles, but not TRAPPC3 as a COPII coat-assembly factor. The TRAPP review says "evidence that any TRAPP complex acts as a membrane tether is currently inconclusive" [PMID:27066478]. Modify these rows to ER-to-Golgi vesicle-mediated transport rather than accepting coat assembly or obsolete vesicle tethering. Annotation stance: - Accept core: `GO:0005085` with `contributes_to`; `GO:0030008` TRAPP complex; `GO:0006888` ER-to-Golgi vesicle-mediated transport; TRAPPII/TRAPPIII complex memberships; cytosol/cytoplasm, ER, Golgi/Golgi membrane/cis-Golgi network membrane. - Keep as non-core: intra-Golgi vesicle-mediated transport and broad Golgi vesicle transport if supported by TRAPPII context but not central to the PN review. - Modify: vesicle-mediated/coat/tethering rows that are broad, over-specific, or obsolete to ER-to-Golgi vesicle-mediated transport. - Mark over-annotated: generic protein binding rows, even when the interaction partner is another TRAPP component; the specific biology should be captured as complex membership. ## Description cleanup note The YAML `description` field was revised to keep it as a standalone biological summary. Project-specific curation framing moved here instead. - Moved out of the YAML description: the prior wording described the autophagophore-recruitment context as PN-specific and interpreted it through TRAPP complex membership and cautious TRAPPIII/RAB1 context rather than a broad autophagy process annotation.