The Bin/Amphiphysin/Rvs (BAR) domain of Endophilin-A2
BAR domains are dimerization, lipid binding and curvature sensing modules found in many different proteins with diverse functions. Endophilins are accessory proteins, localized at synapses, which interact with the endocytic proteins, dynamin and synaptojanin. They are essential for synaptic vesicle formation from the plasma membrane. They interact with voltage-gated calcium channels, thus linking vesicle endocytosis to calcium regulation. They also play roles in virus budding, mitochondrial morphology maintenance, receptor-mediated endocytosis inhibition, and endosomal sorting. Endophilins contain an N-terminal N-BAR domain (BAR domain with an additional N-terminal amphipathic helix), followed by a variable region containing proline clusters, and a C-terminal SH3 domain. They are classified into two types, A and B. Endophilin-A proteins are enriched in the brain and play multiple roles in receptor-mediated endocytosis. Endophilin-A2 (or endophilin-2) is also referred to as SH3P8 (SH3 domain containing protein 8) or SH3GL1 (SH3 domain containing Grb2-like protein 1). It localizes to presynaptic nerve terminals and forms heterodimers with endophilin-A1 through their BAR domains. Endophilin-A2 binds dynamin 1, synaptojanin 1, and the beta1-adrenergic receptor cytoplasmic tail through its SH3 domain.