Polarized exocytosis and anionic phospholipid species implicated in the initiation of clathrin-mediated endocytosis.

Understanding of the mechanisms that initiate clathrin-mediated endocytosis (CME) is incomplete. Recent studies in budding yeast identified the endocytic adaptor protein Yap1801/Yap1802 (budding yeast AP180) as a key CME factor that promotes CME initiation in daughter cells during polarized growth, but how Yap1801/2 is recruited preferentially to the plasma membrane of daughter cells is not clear. The only known cargos for Yap1801/2 in yeast are the synaptobrevins Snc1 and Snc2, which act as v-SNARES for exocytic vesicles arriving at the plasma membrane and are essential for polarized cell growth. In this study, we analyze the spatiotemporal dynamics of functional, fluorescently-tagged Snc1/2 expressed from their endogenous loci and provide evidence that, in concert with anionic phospholipids, Snc1/2 recruit Yap1801/2 preferentially to growing daughter cells. These findings suggest that the coincidence of anionic phospholipids and Snc1/2 facilitates CME initiation in growing daughter cells and directly links polarized CME to polarized secretion.