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.

Research Article 3703 IntroductionEndosomal protein sorting has a vital role in a number of physiologically important processes including antigen presentation, macromolecular nutrient uptake, growth factor receptor signaling and downregulation, autophagy and lysosome biogenesis (for reviews, see Sadowski et al., 2009;Saksena and Emr, 2009;Sann et al., 2009;Seaman, 2008;Lee et al., 2008). Recent studies of inherited diseases have identified several examples of genes encoding proteins that function in endosomal protein sorting that, when mutated, result in a range of pathologies. A notable example is hereditary spastic paraplegias (HSP), the hallmark of which is a selective distal axonopathy. There is a striking localisation of many of the HSP-encoded proteins to the endosome, including the microtubule-severing protein spastin, the ubiquitin-ligase-interacting protein spartin, and NIPA1, a membrane protein that mediates bone morphogenic protein signaling at the endosome (Tsang et al., 2009; for a review, see Salinas et al., 2008). Despite this concentration of HSP proteins at endosomes, in most cases their function is unknown.Much of the core machinery that carries out endosomal protein sorting is conserved in evolution, for example, the retromer complex (for reviews, see Attar and Cullen, 2009;Verges, 2008;Collins, 2008;Bonifacino and Hurley, 2008). Retromer mediates endosometo-Golgi retrieval of lysosomal and vacuolar hydrolase receptors (e.g. the cation-independent mannose 6 phosphate receptor, CIMPR) along with other physiologically significant membrane proteins including wntless, which functions in WNT secretion, and SORL1, a protein that is genetically linked to late-onset Alzheimer's disease (Arighi et al., 2004;Seaman, 2004;Eaton, 2008;Nielsen et al., 2007;Rogaeva et al., 2007).The retromer complex was first identified in yeast where it comprises five proteins encoded by vacuolar protein sorting (VPS) genes. The heteropentameric retromer complex can be functionally dissected into two subcomplexes: a cargo-selective complex formed from a conserved trimer of Vps35p, Vps29p and Vps26p and a 'structural complex' formed from a dimer of the sorting nexin (SNX) proteins Vps5p and Vps17p (Seaman et al., 1998). In mammals, SNX1, SNX2 with SNX5 and SNX6 provide the 'structural' role and can tubulate membranes through the C-terminal Bin, amphiphysin and Rvs (BAR) domains present in these proteins (Carlton et al., 2004;Wassmer et al., 2007). Additionally, SNX5 and SNX6 interact with the microtubule cytoskeleton via the p150glued protein that binds to dynein, thereby linking endosomal protein sorting to microtubules (Wassmer et al., 2009;Hong et al., 2009).The interaction between the SNX component of retromer and p150glued is an example of how retromer-interacting proteins facilitate retromer in mediating endosome-to-Golgi retrieval. In yeast, the SNX3 homologue Grd19p binds to Ftr1p to sort Ftr1p into the retromer pathway (Strochlic et al., 2008). In mammalian cells, the EPS15 homology domain protein, EHD1, interacts ...