Retromer is a membrane-associated heteropentameric coat complex that functions in the endosome-to-Golgi retrieval of the cation-independent mannose-6-phosphate receptor, the Wntless protein and other membrane proteins of physiological significance. Retromer comprises two functional subcomplexes: the cargo-selective subcomplex is a trimer of the VPS35, VPS29, VPS26 proteins, whereas the sorting nexin proteins, Snx1 and Snx2 function to tubulate the endosomal membrane. Unlike the sorting nexins, which contain PtdIns3P-binding PX domains, the cargo-selective VPS35/29/26 complex has no lipid-binding domains and its recruitment to the endosomal membrane remains mechanistically uncharacterised. In this study we show that the VPS35/29/26 complex interacts with the small GTPase Rab7 and requires Rab7 for its recruitment to the endosome. We show that the Rab7K157N mutant that causes the peripheral neuropathy, Charcot-Marie-Tooth disease, does not interact with the VPS35/29/26 complex, resulting in a weakened association with the membrane. We have also identified a novel retromer-interacting protein, TBC1D5, which is a member of the Rab GAP family of proteins that negatively regulates VPS35/29/26 recruitment and causes Rab7 to dissociate from the membrane. We therefore propose that recruitment of the cargo-selective VPS35/29/26 complex is catalysed by Rab7 and inhibited by the Rab-GAP protein, TBC1D5.

Endosomal protein sorting controls the localization of many physiologically important proteins and is linked to several neurodegenerative diseases. VPS35 is a component of the retromer complex, which mediates endosome-to-Golgi retrieval of membrane proteins such as the cation-independent mannose 6-phosphate receptor. Furthermore, retromer is also required for the endosomal recruitment of the actin nucleation promoting WASH complex. The VPS35 D620N mutation causes a rare form of autosomal-dominant Parkinson’s disease (PD). Here we show that this mutant associates poorly with the WASH complex and impairs WASH recruitment to endosomes. Autophagy is impaired in cells expressing PD-mutant VPS35 or lacking WASH. The autophagy defects can be explained, at least in part, by abnormal trafficking of the autophagy protein ATG9A. Thus, the PD-causing D620N mutation in VPS35 restricts WASH complex recruitment to endosomes, and reveals a novel role for the WASH complex in autophagosome formation.