Interaction of α-actinin with the cadherin/catenin cell-cell adhesion complex via α-catenin

Cadherins are Ca²⁺-dependent, cell surface glycoproteins involved in cell-cell adhesion. Extracellularly, transmembrane cadherins such as E-, P-, and N-cadherin self-associate, while intracellularly they interact indirectly with the actin-based cytoskeleton. Several intracellular proteins termed catenins, including α-catenin, β-catenin, and plakoglobin, are tightly associated with these cadherins and serve to link them to the cytoskeleton. Here, we present evidence that in fibroblasts α-actinin, but not vinculin, colocalizes extensively with the N-cadherin/catenin complex. This is in contrast to epithelial cells where both cytoskeletal proteins colocalize extensively with E-cadherin and catenins. We further show that α-actinin, but not vinculin, co-immunoprecipitates specifically with α-and β-catenin from N- and E-cadherin-expressing cells, but only if α-catenin is present. Moreover, we show that α-actinin coimmunoprecipitates with the N- cadherin/catenin complex in an actin-independent manner. We therefore propose that cadherin/catenin complexes are linked to the actin cytoskeleton via a direct association between α-actinin and α-catenin.