TRAPPC8 (trafficking protein particle complex subunit 8) is a core component of the mammalian TRAPPIII complex that regulates multiple membrane trafficking pathways. The protein functions as part of a guanine nucleotide exchange factor (GEF) complex with specificity for Rab1 and Rab43 GTPases 1. TRAPPC8 plays essential roles in endoplasmic reticulum-to-Golgi trafficking and COPII vesicle formation, with the TRAPPIII complex positively modulating recruitment of Sec13/31 components to COPII vesicles 2. In autophagy regulation, TRAPPC8 maintains the cycling pool of ATG9 required for autophagosome initiation, working together with TBC1D14 to control membrane trafficking from recycling endosomes 3. The protein contains an ASH domain that targets it to centrosomes/basal bodies, and TRAPPC8 depletion impairs ciliogenesis 4. Structurally, TRAPPC8 serves as an adaptor protein, with TRAPPC2 binding to either TRAPPC8 or TRAPPC9 during formation of TRAPPIII or TRAPPII complexes, respectively 5. The protein also functions in viral entry, specifically required for human papillomavirus cell entry through endocytosis-dependent mechanisms 6. TRAPPC8's diverse roles highlight its importance in coordinating membrane trafficking across secretory, autophagic, and endocytic pathways.