Identification of a novel beta-catenin-interacting protein

Cadherin is a well-known cell-cell adhesion molecule, and it binds to beta- catenin, which in turn binds to alpha-catenin. However, little is known abo ut the regulatory mechanism underlying the cadherin-mediated cell-cell adhe sion. Here we purified two novel beta-catenin-interacting proteins with mol ecular masses of 180 kDa (p180) and 150 kDa (p150) from bovine brain cytoso l by using glutathione S-transferase (GST)-beta-catenin affinity column chr omatography. Mass spectral analysis revealed p180 to be identical to KIAA03 13 which has a putative Rap1 guanine nucleotide exchange factor (GEF) domai n and p150 to be the same as KIAA0705 which has a high degree of sequence s imilarity to the synaptic scaffolding molecule (S-SCAM), which binds beta-c atenin and KIAA0313 in the yeast two-hybrid system and overlay assay, respe ctively (Ide et al., Biochem. Biophys. Res. Commun. 256, 456-461, 1999; Oht suka et al., Biochem. Biophys. Res. Commun. 265, 38-44, 1999). beta-Catenin was coimmunoprecipitated with KIAA0313 in Madin-Darby canine kidney II (MD CKII) cells, bovine brain cytosol, and EL cells. KIAA0313 and beta-catenin were partly colocalized at sites of cell-cell contact in MDCKII cells. Take n together, our data suggest that KIAA0313 associates with beta-catenin thr ough KIAA0705 in vivo at sites of cell-cell contact. (C) 2000 Academic Pres s.