Functions in an early step of clathrin-mediated endocytosis (PubMed:30822429). Has both a membrane binding/bending activity and the ability to recruit proteins essential to the formation of functional clathrin-coated pits. May regulate Bmp signaling by regulating clathrin-mediated endocytosis of Bmp receptors. Involved in the regulation of T-cell poliferation and activation (PubMed:30822429, PubMed:32098969). Affects TCR clustering upon receptor triggering and modulates its internalisation, playing a role in TCR-dependent T-cell activation (PubMed:32098969). May oligomerize and form homotetramer (By similarity). Interacts with AP2A2 and AP2B1; 2 subunits of the adaptor protein complex AP-2 (By similarity). Interacts with DAB2. Interacts with clathrin (CLTC or CLTCL1). Interacts with EPS15, EPS15R and ITSN1. Interacts with AGFG1 and CALM. May interact with ACVR1; linking this receptor to clathrin-mediated endocytosis (PubMed:22484487). Associated with forming but not mature clathrin-coated vesicles. The recruitment to coated-pits precede the one of clathrin and the adaptor protein complex AP-2. According to PubMed:17617719 it may also dynamically associate with Golgi/TGN membranes. Predominantly expressed in lymphoid cells. The disease is caused by variants affecting the gene represented in this entry. Belongs to the FCHO family. Extended N-terminus.