α-Catenin-dependent cytoskeletal tension controls Yap activity in the heart.
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ABSTRACT:
SUBMITTER: Vite A
PROVIDER: S-EPMC5868989 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The contractile forces in individual cells drive the tissue processes, such as morphogenesis and wound healing, and maintain tissue integrity. In these processes, α-catenin molecule acts as a tension sensor at cadherin-based adherens junctions (AJs), accelerating the positive feedback of intercellular tension. Under tension, α-catenin is activated to recruit vinculin, which recruits actin filaments to AJs. In this study, we revealed how α-catenin retains its activated state while avoiding unfolding under tension. Using single-molecule force spectroscopy employing atomic force microscopy (AFM), we found that mechanically activated α-catenin fragment had higher mechanical stability than a non-activated fragment. The results of our experiments using mutated and segmented fragments showed that the key intramolecular interactions acted as a conformational switch. We also found that the conformation of α-catenin was reinforced by vinculin binding. We demonstrate that α-catenin adaptively changes its conformation under tension to a stable intermediate state, binds to vinculin, and finally settles into a more stable state reinforced by vinculin binding. Our data suggest that the plastic characteristics of α-catenin, revealed in response to both mechanical and biochemical cues, enable the functional-structural dynamics at the cellular and tissue levels.
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Project description:Adherens junctions (AJs) are essential for cell-cell contacts, morphogenesis, and the development of all higher eukaryotes. AJs are formed by calcium-dependent homotypic interactions of the ectodomains of single membrane-pass cadherin family receptors. These homotypic interactions in turn promote binding of the intracellular cytoplasmic tail domains of cadherin receptors with β-catenin, a multifunctional protein that plays roles in both transcription and AJs. The cadherin receptor-β-catenin complex binds to the cytoskeletal protein α-catenin, which is essential for both the formation and the stabilization of these junctions. Precisely how α-catenin contributes to the formation and stabilization of AJs is hotly debated, although the latter is thought to involve its interactions with the cytoskeletal protein vinculin. Here we report the crystal structure of the vinculin binding domain (VBD) of α-catenin in complex with the vinculin head domain (Vh1). This structure reveals that α-catenin is in a unique unfurled mode allowing dimer formation when bound to vinculin. Finally, binding studies suggest that vinculin must be in an activated state to bind to α-catenin and that this interaction is stabilized by the formation of a ternary α-catenin-vinculin-F-actin complex, which can be formed via the F-actin binding domain of either protein. We propose a feed-forward model whereby α-catenin-vinculin interactions promote their binding to the actin cytoskeleton to stabilize AJs.
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Project description:Mechanical forces are integrated at cadherin-based adhesion complexes to regulate morphology and strength of cell-cell junctions and organization of associated F-actin. A central mechanosensor at the cadherin complex is α-catenin, whose stretching recruits vinculin to regulate adhesion strength. The identity of the F-actin regulating signals that are also activated by mechanical forces at cadherin-based junctions has remained elusive. Here we identify the actin-regulators VASP, zyxin and TES as members of punctate, tensile cadherin-based junctions called Focal Adherens Junctions (FAJ) and show that they display mechanosensitive recruitment similar to that of vinculin. However, this recruitment is not altered by destroying or over-activating the α-catenin/vinculin module. Structured Illumination Microscopy (SIM) indicates that these tension sensitive proteins concentrate at locations within FAJs that are distinct from the core cadherin complex proteins. Furthermore, localization studies using mutated versions of VASP and zyxin indicate that these two proteins require binding to each other in order to localize to the FAJs. We conclude that there are multiple force sensitive modules present at the FAJ that are activated at distinct locations along the cadherin-F-actin axis and regulate specific aspects of junction dynamics.
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