Binds to membranes enriched in phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). Modifies membrane curvature and facilitates the formation of clathrin-coated invaginations (By similarity). Regulates receptor-mediated endocytosis (PubMed:10557078, PubMed:10393179). Monomer. Binds clathrin, ZBTB16/ZNF145 and ITSN1 (By similarity). Binds ubiquitinated proteins (By similarity). Binds AP2A1 and AP2A2. Interacts with RALBP1 in a complex also containing NUMB and TFAP2A during interphase and mitosis. Interacts with AP2B1. Interacts with UBQLN2. Interacts with REPS2; the interaction is direct (PubMed:10557078, PubMed:10764745, PubMed:10393179). Interacts with EPS15; the interaction is direct (PubMed:10764745, PubMed:10393179). Associated with the cytoplasmic membrane at sites where clathrin-coated pits are forming. Colocalizes with clathrin and AP-2 in a punctate pattern on the plasma membrane. Detected in presynaptic nerve terminals and in Golgi stacks. May shuttle to the nucleus when associated with ZBTB16/ZNF145 (By similarity). The NPF repeat domain is involved in EPS15 binding. The DPW repeat domain is involved in AP2A2 and clathrin binding. The [DE]-X(1,2)-F-X-X-[FL]-X-X-X-R motif mediates interaction with the AP-2 complex subunit AP2B1. Phosphorylated on serine and/or threonine residues in mitotic cells. Phosphorylation reduces interaction with REPS2, AP-2 and the membrane fraction. Depolarization of synaptosomes results in dephosphorylation. Ubiquitinated. May be due to a competing donor splice site. Belongs to the epsin family. The bubble's bend - Issue 42 of January 2004