The Bin/Amphiphysin/Rvs (BAR) domain of Endophilin-A3
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 that interacts 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-A3 (or endophilin-3) is also referred to as SH3P13 (SH3 domain containing protein 13) or SH3GL3 (SH3 domain containing Grb2-like protein 3). It regulates Arp2/3-dependent actin filament assembly during endocytosis. It binds N-WASP through its SH3 domain and enhances the ability of N-WASP to activate the Arp2/3 complex. Endophilin-A3 co-localizes with the vesicular glutamate transporter 1 (VGLUT1), and may play an important role in the synaptic release of glutamate.