The armadillo repeat region targets ARVCF to cadherin-based cellular junctions

The cytoplasmic domain of the transmembrane protein M-cadherin is involved in anchoring cytoskeletal elements to the plasma membrane at cell-cell cont act sites. Several members of the armadillo repeat protein family mediate t his linkage, We show here that ARVCF, a member of the p120 (ctn) subfamily, is a ligand for the cytoplasmic domain of M-cadherin, and characterize the regions involved in this interaction in detail. Complex formation in an in vivo environment was demonstrated in (1) yeast two-hybrid screens, using a cDNA library from differentiating skeletal muscle and part of the cytoplas mic M-cadherin tail as a bait, and (2) mammalian cells, using a novel exper imental system, the MOM recruitment assay. Immunoprecipitation and in vitro binding assays confirmed this interaction. Ectopically expressed EGFP-ARVC F-C11, an N-terminal truncated fragment, targets to junctional structures i n epithelial MCF7 cells and cardiomyocytes, where it colocalizes with the r espective cadherins, beta -catenin and p120 (ctn). Hence, the N terminus of ARVCF is not required for junctional localization. In contrast, deletion o f the four N-terminal armadillo repeats abolishes this ability in cardiomyo cytes, Detailed mutational analysis revealed the armadillo repeat region of ARVCF as sufficient and necessary for interaction with the 55 membrane-pro ximal amino acids of the M-cadherin tail.