CLONING AND CHARACTERIZATION OF BAI-ASSOCIATED PROTEIN-1 - A PDZ DOMAIN-CONTAINING PROTEIN THAT INTERACTS WITH BAI1

Brain-specific angiogenesis inhibitor 1 (BAI1), which is a p53-target gene specifically expressed in brain, encodes a seven-span transmembra ne protein. Using a two-hybrid system, we isolated a cDNA that encodes a protein, named BAP1 (BAI1-associated protein), which interacts with the cytoplasmic region of BAI1. BAP1 is a novel member of the MAGUK ( membrane-associated guanylate kinase homologue) family; it possesses a guanylate kinase domain, WW domains, and multiple PDZ domains. Intera ction between BAI1 and BAP1 was mediated by a QTEV motifin the carboxy -terminal region of BAI1 and PDZ domains of BAP1, By immunocytochemica l analysis of COS-7 cells transfected with BAI1 and BAP1, both product s were co-localized at the cytoplasmic membrane, especially at cell-ce ll junctions. Cells transfected with BAI1 formed filopodia-like cytopl asmic extensions. These results suggest that BAI1 and BAP1 might be in volved in cell adhesion and signal transduction in brain. (C) 1998 Aca demic Press.