A Tca17TRAPPC2L/TRAPPC11/12/13 subcomplex directs TRAPPIII to autophagy

TRAPP complexes are master regulators of membrane trafficking. TRAPPs are targeted to different locales by pathway-specific subunits decorating a core hetero-heptamer to build TRAPPII (Golgi exit) and TRAPPIII (autophagosomes and ER-Golgi trafficking). Metazoan and Arabidopsis TRAPPIII have three components, TRAPPC11/12/13 absent from budding yeast. We studied TRAPPC11/12/13 in the related ascomycete Aspergillus nidulans, where TRAPPC11 and TRAPPC12 localize to pre-autophagosomes and their ablation impairs autophagy. Two stable subcomplexes containing Tca17TRAPPC2L coexist: one includes the TRAPPII-specific subunits Trs120/Trs130/Trs65 whereas the other contains the TRAPPIII-specific subunits TRAPPC11/12/13. Both are recruited to core TRAPP by Tca17TRAPPC2L, which therefore plays a crucial role by determining the physiological role of TRAPP. TRAPPIII also exists in two versions, TRAPPIIIa and TRAPPIIIb, both containing Trs85TRAPPC8, but only TRAPPIIIb containing TRAPPC11/12/13, which target TRAPPIII to autophagy. This study might help characterize potentially pathogenic mutations affecting human TRAPPC11/12/13, facilitating assessment of their functional consequences in a genetically amenable ascomycete.