THE TUMOR-SUPPRESSOR PROTEIN APC COLOCALIZES WITH BETA-CATENIN IN THECOLON EPITHELIAL-CELLS

The APC gene is mutated in familial adenomatous polyposis and sporadic colorectal tumors. The product of this gene is a 300 kDa cytoplasmic protein associated with catenin. In the present study, we examined the subcellular localization of the APC protein and beta-catenin in the m ouse colon by double-labeling immunocytochemistry. While the APC prote in was localized in the lateral and apical cytoplasm and in microvilli of the epithelial cells, beta-catenin was present exclusively in the lateral cytoplasm. Double-labeling-immunoelectron microscopy demonstra ted precise colocalization of the APC protein and beta-catenin along t he lateral plasma membrane. These results suggest that the APC protein functions in cooperation with beta-catenin in the lateral cytoplasm b ut has other functions independent of beta-catenin in the apical cytop lasm and in microvilli. (C) 1996 Academic Press, Inc.