TRAPPC13 is a subunit of the mammalian TRAPPIII complex, a conserved regulator of membrane trafficking 1. As part of TRAPPIII, TRAPPC13 functions as a guanine nucleotide exchange factor (GEF) with selective specificity for Rab1 and Rab43 GTPases, distinct from TRAPPII which targets Rab1 and Rab11 1. TRAPPC13 is enriched at the base of primary cilia 2 and plays critical roles in endoplasmic reticulum-to-Golgi and intra-Golgi vesicular transport through its GEF activity 3. Under Golgi stress conditions induced by brefeldin A, TRAPPC13 depletion reduces Rab1a/1b activity, impairs autophagy, and paradoxically preserves secretory pathway viability in an ARF1 and GBF1-dependent manner 3. This survival response involves reduced caspase activation and ER stress marker induction, suggesting TRAPPC13's role in autophagic flux during cellular stress 3. The TRAPPIII complex containing TRAPPC13 exhibits enhanced GEF activity when associated with lipid membranes, with complex-specific subunits altering the active site architecture compared to TRAPPII 1. These findings indicate TRAPPC13 is essential for maintaining proper vesicular trafficking and stress-responsive autophagy.