An Autoinhibited Structure of α-Catenin and Its Implications for Vinculin Recruitment to Adherens Junctions

α-Catenin is an actin- and vinculin-binding protein that regulates cell-cell adhesion by interacting with cadherin adhesion receptors through β-catenin, but the mechanisms by which it anchors the cadherin-catenin complex to the actin cytoskeleton at adherens junctions remain unclear. Here we determined crystal structures of αE-catenin in the autoinhibited state and the actin-binding domain of αN-catenin. Together with the small-angle x-ray scattering analysis of full-length αN-catenin, we deduced an elongated multidomain assembly of monomeric α-catenin that structurally and functionally couples the vinculin- and actin-binding mechanisms. Cellular and biochemical studies of αE- and αN-catenins show that αE-catenin recruits vinculin to adherens junctions more effectively than αN-catenin, partly because of its higher affinity for actin filaments. We propose a molecular switch mechanism involving multistate conformational changes of α-catenin. This would be driven by actomyosin-generated tension to dynamically regulate the vinculin-assisted linkage between adherens junctions and the actin cytoskeleton. Background: α-Catenin is an actin-binding protein that recruits vinculin to adherens junctions. Results: An elongated autoinhibited structure of α-catenin indicates structural and functional coupling of its vinculin- and actin-binding mechanisms. Conclusion: The anchoring strength of adherens junctions is dynamically regulated by α-catenin to match the actomyosin-generated tension. Significance: Multistate conformations of α-catenin facilitate the direct and vinculin-assisted linkages between the cadherin-catenin complex and the actin cytoskeleton.