The Bin/Amphiphysin/Rvs (BAR) domain of Amphiphysin I and II
BAR domains are dimerization, lipid binding and curvature sensing modules found in many different proteins with diverse functions. Amphiphysins function primarily in endocytosis and other membrane remodeling events. They contain an N-terminal BAR domain with an additional N-terminal amphipathic helix (an N-BAR), a variable central domain, and a C-terminal SH3 domain. Amphiphysin I proteins, enriched in the brain and nervous system, contain domains that bind clathrin, Adaptor Protein complex 2 (AP2), dynamin and synaptojanin. They function in synaptic vesicle endocytosis. Some amphiphysin II isoforms, also called Bridging integrator 1 (Bin1), are localized in many different tissues and may function in intracellular vesicle trafficking. In skeletal muscle, Bin1 plays a role in the organization and maintenance of the T-tubule network. The N-BAR domain of amphiphysin forms a curved dimer with a positively-charged concave face that can drive membrane bending and curvature. Human autoantibodies to amphiphysin-1 hinder GABAergic signaling and contribute to the pathogenesis of paraneoplastic stiff-person syndrome. Mutations in amphiphysin-2 (BIN1) are associated with autosomal recessive centronuclear myopathy.