Assembly protein recruiting clathrin and adaptor protein complex 2 (AP2) to cell membranes at sites of coated-pit formation and clathrin-vesicle assembly. May be required to determine the amount of membrane to be recycled, possibly by regulating the size of the clathrin cage. Involved in AP2-dependent clathrin-mediated endocytosis at the neuromuscular junction. Binds clathrin and phosphatidylinositol 4,5-bisphosphate. Colocalized with clathrin in the Golgi area. In embryos, expression is seen in central and peripheral nervous systems (brain and ventral nerve cord) and Garland cells. Coexpressed with clathrin at presynaptic boutons of neuromuscular junctions. Belongs to the PICALM/SNAP91 family.