Force-Dependent Interactions between the E-Cadherin-Catenin Complex and Actin Filaments

Abstract

Adherens junctions (AJ) are mechano-sensitive protein complexes essential for many multicellular processes such as tissue morphogenesis and homeostasis. Genetic studies identified the AJ cell-cell adhesion complex of E-cadherin, beta-catenin, and the actin-binding protein alpha-catenin as a minimal ternary complex required for interactions with the actin cytoskeleton. However, attempts to reconstitute in vitro a direct linkage between the cadherin-catenin complex and actin filaments in bulk pelleting assays have been unsuccessful. Contemporary experiments in living cells indirectly showed that force, which was not reconstituted in vitro, is important for normal cell-cell adhesion. As a result, we developed a novel optical trapping assay to determine if and how the cadherin-catenin complex binds to actin filaments under mechanical load (see figure). We find that multiple cadherin-catenin complexes can together form a robust, load-resistant connection to actin that can withstand >10 pN of force for several seconds. Individual cadherin-catenin complexes also bind actin, but the interaction is relatively weak and transient. To our knowledge, these are the first data showing direct, mechanically robust binding between the cadherin-catenin complex and actin filaments. Our results provide essential support to models proposing that the AJ is a mechano-sensitive complex.View Large Image | View Hi-Res Image | Download PowerPoint Slide