Formin-binding protein 1 (Fnbp1)

Required to coordinate membrane tubulation with reorganization of the actin cytoskeleton during the late phase of clathrin-mediated endocytosis. Binds to lipids like phosphatidylinositol 4,5-bisphosphate and phosphatidylserine and promotes membrane invagination and the formation of tubules.

Also enhances actin polymerization through the recruitment of WASL/N-WASP, which subsequently activates the Arp2/3 complex. Actin polymerization may foster the fission of membrane tubules to form endocytic vesicles.