Cloning and characterization of BAP3 (BAI-associated protein 3), a C2 domain-containing protein that interacts with BAI1.

BAI1 (brain-specific angiogenesis inhibitor 1), a p53-target gene specifically expressed in brain, encodes a seven-span transmembrane protein considered to be a member of the secretin receptor family. Using a two-hybrid system, we isolated a cDNA encoding a product that interacts with the cytoplasmic region of BAI1 and designated it BAP3 (BAI1-associated protein 3). The BAP3 product is a novel C2 domain-containing molecule with homology to Munc13 and synaptotagmin. As with Munc13, BAP3 is expressed predominantly in brain. Deletion-mutant analysis revealed that the interaction between BAI1 and BAP3 was not mediated by the C2 domains. Its predominant expression in brain and homology to Munc13 indicate that BAP3, by interacting with BAI1, might be involved in some neuronal function such as regulating release of neurotransmitters.