Plant Endocytosis Requires the ER Membrane-Anchored Proteins VAP27-1 and VAP27-3

Through yet-undefined mechanisms, the plant endoplasmic reticulum (ER) has a critical role in endocytosis. The plant ER establishes a close association with endosomes and contacts the plasma membrane (PM) at ER-PM contact sites (EPCSs) demarcated by the ER membrane-associated VAMP-associated-proteins (VAP). Here, we investigated two plant VAPs, VAP27-1 and VAP27-3, and found an interaction with clathrin and a requirement for the homeostasis of clathrin dynamics at endocytic membranes and endocytosis. We also demonstrated direct interaction of VAP27-proteins with phosphatidylinositol-phosphate lipids (PIPs) that populate endocytic membranes. These results support that, through interaction with PIPs, VAP27-proteins bridge the ER with endocytic membranes and maintain endocytic traffic, likely through their interaction with clathrin. [Display omitted] •VAP27-1 and VAP27-3 interact with clathrin in vitro and in vivo•VAP27-1 and VAP27-3 interact with lipids enriched in endocytic membranes•VAP27-1 and VAP27-3 are required for endocytosis and plant growth•The loss of VAP27-proteins alters homeostasis of the endocytic membranes Stefano et al. demonstrate that plant VAPs (VAP27-1 and VAP27-3) interact with clathrin and with phosphatidylinositol-phosphate lipids (PIPs) that populate endocytic membranes. The findings support a model showing that, through interaction with PIPs and clathrin, VAP27-proteins bridge the ER with endocytic membranes and maintain endocytic traffic.