ORP-Mediated ER Contact with Endocytic Sites Facilitates Actin Polymerization

Oxysterol binding protein-related proteins (ORPs) are conserved lipid binding polypeptides, enriched at ER contacts sites. ORPs promote non-vesicular lipid transport and work as lipid sensors in the context of many cellular tasks, but the determinants of their distinct localization and function are not understood. Here, we demonstrate that the yeast endocytic invaginations associate with the ER and that this association specifically requires the ORPs Osh2 and Osh3, which bridge the endocytic myosin-I Myo5 to the ER integral-membrane VAMP-associated protein (VAP) Scs2. Disruption of the ER contact with endocytic sites using ORP, VAP, myosin-I, or reticulon mutants delays and weakens actin polymerization and interferes with vesicle scission. Finally, we provide evidence suggesting that ORP-dependent sterol transfer facilitates actin polymerization at endocytic sites. [Display omitted] •Endocytic sites associate with the cortical endoplasmic reticulum (cER)•ER contact facilitates actin polymerization and vesicle scission•ORPs link the ER VAMP-associated protein (VAP) to the endocytic myosin-I•Proper onset of actin polymerization requires the Osh2 sterol transfer domain Clathrin-mediated endocytosis from the plasma membrane is thought to mostly rely on the assembly of a coat built from cytosolic proteins. In contrast, Encinar et al. demonstrate that the ER contacts endocytic sites and plays a role in facilitating membrane invagination for endocytosis.