Deconstructing the Cadherin-Catenin-Actin Complex

Spatial and functional organization of cells in tissues is determined by cell-cell adhesion, thought to be initiated through transinteractions between extracellular domains of the cadherin family of adhesion proteins, and strengthened by linkage to the actin cytoskeleton. Prevailing dogma is that cadherins are linked to the actin cytoskeleton through (beta)-catenin and (alpha)-catenin, although the quaternary complex has never been demonstrated. We test this hypothesis and find that (alpha)-catenin does not interact with actin filaments and the E-cadherin-(beta)-catenin complex simultaneously, even in the presence of the actin binding proteins vinculin and (alpha)-actinin, either in solution or on isolated cadherin-containing membranes. Direct analysis in polarized cells shows that mobilities of E-cadherin, (beta)-catenin, and (alpha)-catenin are similar, regardless of the dynamic state of actin assembly, whereas actin and several actin binding proteins have higher mobilities. These results suggest that the linkage between the cadherin-catenin complex and actin filaments is more dynamic than previously appreciated.