Endocytic vacuole formation by WASH-mediated endocytosis
Endocytosis is a fundamental cellular process facilitated by diverse mechanisms. Remarkably, several distinct clathrin-independent endocytic processes were identified and characterized following virus uptake into cells. For some, however, mechanistic execution and biological function remain largely unclear. This includes an endocytic process exploited by human papillomavirus type 16 (HPV16). Using HPV16, we examined how vesicles are formed by combining systematic cellular perturbations with electron and video microscopy. Cargo uptake occurred by uncoated, inward-budding pits. Mechanistically, vesicle scission was facilitated by actin polymerization controlled through the actin nucleation promoting factor WASH. While WASH typically functions in conjunction with the retromer complex on endosomes during retrograde trafficking, endocytic vesicle formation was largely independent of retromer itself and the heterodimeric membrane-bending SNX-BAR retromer adaptor, thereby uncovering a role of WASH in endocytosis in addition to its canonical role in intracellular membrane trafficking.