Emerging roles of brain-specific angiogenesis inhibitor 1

Brain-specific angiogenesis inhibitor 1 (BAI1) encodes a seven-transmembrane protein that belongs to the adhesion-GPCR family. ^1-7 Although BAI1 was named for the ability of its extracellular region to inhibit angiogenesis in tumor models, its function in physiological contexts was elusive and remained an orphan receptor until recently. ^5,6,8-14 BAI1 is now considered a phagocytic receptor that can recognize phosphatidylserine exposed on apoptotic cells. Moreover, BAI1 has been shown to function upstream of the signaling module comprised of ELMO/Dock180/Rac proteins, thereby facilitating the cytoskeletal reorganization necessary to mediate the phagocytic clearance of apoptotic cells. ^15,16 Here,wereview the phytogeny, structure, associating proteins, as well as the known and proposed functions of BAI1.