Plays a role in endoplasmic reticulum to Golgi apparatus trafficking at a very early stage (PubMed:21525244). Maintains together with TBC1D14 the cycling pool of ATG9 required for initiation of autophagy (PubMed:26711178). Component of the multisubunit TRAPP (transport protein particle) complex, which includes TRAPPC2, TRAPPC2L, TRAPPC3, TRAPPC3L, TRAPPC4, TRAPPC5, TRAPPC8, TRAPPC9, TRAPPC10, TRAPPC11 and TRAPPC12. Interacts with TBC1D14 (PubMed:26711178). May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the TRS85 family. Truncated N-terminus. Truncated N-terminus. Extended N-terminus. Truncated N-terminus.