Quantifications of FCHo2 interaction with in vitro and in cellulo systems

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