Structural organization and dynamics of FCHo2 docking

19 Clathrin-mediated endocytosis (CME) is a central trafficking pathway in eukaryotic cells regulated by 20 phosphoinositides. The plasma membrane phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) plays an 21 instrumental role in driving CME initiation. The F-BAR domain only protein 1 and 2 complex 22 (FCHo1/2) is among the early proteins that reach the plasma membrane, but the exact mechanisms 23 triggering its recruitment remain elusive. Here, we show the molecular dynamics of FCHo2 self24 assembly on membranes by combining minimal reconstituted in vitro and cellular systems. Our results 25 indicate that PI(4,5)P2 domains assist FCHo2 docking at specific membrane regions, where it self26 assembles into ring-like shape protein patches. We show that the binding of FCHo2 on cellular 27 membranes promotes PI(4,5)P2 clustering at the boundary of cargo receptors and that this 28 accumulation enhances clathrin assembly. Thus, our results provide a mechanistic framework that 29 could explain the recruitment of early PI(4,5)P2-interacting proteins at endocytic sites. 30