α-catenin-vinculin interaction functions to organize the apical junctional complex in epithelial cells

alpha E-catenin, a cadherin-associated protein, is required for tight junction (TJ) organization, but its role is poorly understood. We transfected an alpha E-catenin-deficient colon carcinoma line with a series of alpha E-catenin mutant constructs. The results showed that the amino acid 326-509 domain of this catenin was required to organize TJs, and its COOH-terminal domain was not essential for this process. The 326-509 internal domain was found to bind vinculin. When an NH2-terminal alpha E-catenin fragment, which is by itself unable to organize the TJ, was fused with the vinculin tail, this chimeric molecule could induce TJ assembly in the alpha E-catenin-deficient cells. In vinculin-null F9 cells, their apical junctional organization was impaired, and this phenotype was rescued by reexpression of vinculin. These results indicate that the alpha E-catenin-vinculin interaction plays a role in the assembly of the apical junctional complex in epithelia.