Vinculin tension distributions of individual stress fibers within cell-matrix adhesions

Journal of Cell Science (Impact Factor: 5.33). 05/2013; 126(14). DOI: 10.1242/jcs.119032
Source: PubMed

ABSTRACT Actomyosin stress fibers (SFs) enable cells to exert traction on planar extracellular matrices (ECMs) by tensing focal adhesions (FAs) at the cell-ECM interface. While it is widely appreciated that the spatial and temporal distribution of these tensile forces play key roles in polarity, motility, fate choice, and other defining cell behaviors, virtually nothing is known about how an individual SF quantitatively contributes to tensile loads borne by specific molecules within associated FAs. We address this key open question by using femtosecond laser ablation to sever single SFs in cells while tracking tension across vinculin using a molecular optical sensor. We show that disruption of a single SF reduces tension across vinculin in FAs located throughout the cell, with enriched vinculin tension reduction in FAs oriented parallel to the targeted SF. Remarkably, however, some subpopulations of FAs exhibit enhanced vinculin tension upon SF irradiation and undergo dramatic, unexpected transitions between tension-enhanced and tension-reduced states. These changes depend strongly on the location of the severed SF, consistent with our earlier finding that different SF pools are regulated by distinct myosin activators. We critically discuss the extent to which these measurements can be interpreted in terms of whole-FA tension and traction and propose a model that relates SF tension to adhesive loads and cell shape stability. These studies represent the most direct and high-resolution intracellular measurements of SF contributions to tension on specific FA proteins to date and offer a new paradigm for investigating regulation of adhesive complexes by cytoskeletal force.

Download full-text


Available from: Ching-Wei Chang, Jun 19, 2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: The ability of cells to sense and respond to mechanical forces is central to a wide range of biological processes and plays an important role in numerous pathologies. The molecular mechanisms underlying cellular mechanotransduction, however, have remained largely elusive because suitable methods to investigate subcellular force propagation were missing. Here, we review recent advances in the development of biosensors that allow molecular force measurements. We describe the underlying principle of currently available techniques and propose a strategy to systematically evaluate new Förster resonance energy transfer (FRET)-based biosensors.
    Cellular and Molecular Bioengineering 12/2014; 8(1). DOI:10.1007/s12195-014-0368-1 · 1.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Author Summary Adherent cells respond very sensitively not only to biochemical, but also to physical properties of their environment. For example, it has been shown that stem cell differentiation can be guided by substrate rigidity, which is sensed by cells by actively pulling on their environment with actomyosin-generated forces. A commonly used method to measure cell forces during essential biological processes is traction force microscopy, which uses the deformations of a soft elastic substrate to calculate cell forces. However, the standard setup for traction force microscopy suffers from mathematical limitations in calculating forces from displacements. In order to improve this method, we combine image data and biophysical modelling to arrive at a procedure which is more robust and in addition allows us to make statements about the force distribution not only at the cell-substrate interface, but also inside the cell. Here we demonstrate this approach for the contractility of actin stress fibers, which we investigate experimentally with U2OS-cells and theoretically with an active cable network model.
    PLoS Computational Biology 03/2015; 11(3):e1004076. DOI:10.1371/journal.pcbi.1004076 · 4.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cells are exquisitely sensitive to the mechanical nature of their environment, including applied force and the stiffness of the extracellular matrix (ECM). Recent evidence has shown that these variables are critical regulators of diverse processes mediating embryonic development, adult tissue physiology, and many disease states, including cancer, atherosclerosis, and myopathies. Often, detection of mechanical stimuli is mediated by the structures that link cells that surround ECM, the focal adhesions (FAs). FAs are intrinsically force sensitive and display altered dynamics, structure, and composition in response to applied load. While much progress has been made in determining the proteins that localize to and regulate the formation of these structures, less is known about the role of tension across specific proteins in this process. A recently developed class of force-sensitive biosensors is enabling a greater understanding of the molecular bases of cellular mechanosensitivity and cell migration.
    Progress in molecular biology and translational science 01/2014; 126:3-24. DOI:10.1016/B978-0-12-394624-9.00001-4 · 3.11 Impact Factor