Is a key player in the control of plasma membrane curvature, and membrane shaping and remodeling. Required in muscle cells for the formation of T-tubules, tubular invaginations of the plasma membrane that function in depolarization-contraction coupling. Required in muscle cells for the formation of T-tubules, tubular invaginations of the plasma membrane that function in depolarization-contraction coupling (PubMed:12183633). Is a negative regulator of endocytosis (By similarity). Is also involved in the regulation of intracellular vesicles sorting, modulation of BACE1 trafficking and the control of amyloid-beta production (PubMed:12668730, PubMed:27179792). In neuronal circuits, endocytosis regulation may influence the internalization of PHF-tau aggregates (By similarity). May be involved in the regulation of MYC activity and the control cell proliferation (By similarity). Heterodimer with AMPH (By similarity). Binds SH3GLB1 (PubMed:12456676). Interacts (via SH3 domain) with DNM1. Interacts with SYNJ1 (By similarity). Interacts (via SH3 domain) with DNM2. Interacts with CLTC (By similarity). Interacts with AP2A2. Interacts with AP2B1 (By similarity). Interacts with MYC (via N-terminal transactivation domain); the interaction requires the integrity of the conserved MYC box regions 1 and 2 (PubMed:8782822). Interacts with BIN2 (By similarity). Interacts with SNX4 (PubMed:12668730). Interacts (via BAR domain) with BACE1 (By similarity). Binds (via BAR domain) F-actin (By similarity). Isoform 1 is expressed mainly in the brain. Isoform 2 is widely expressed. Phosphorylated by protein kinase C.