Mechanotransduction of fluid stresses governs 3D cell migration (original) (raw)
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Molecular biology of the cell, 2017
Metastasis requires tumor cells to navigate through a stiff stroma, and to squeeze through confined microenvironments. Whether tumors exploit unique biophysical properties to metastasize remains unclear. Data showed that invading mammary tumor cells, when cultured in a stiffened three-dimensional extracellular matrix that recapitulates the primary tumor stroma, adopt a basal-like phenotype. Metastatic tumor cells and basal-like tumor cells exerted higher integrin-mediated traction forces at the bulk and molecular levels, consistent with a motor-clutch model where motors and clutches are both increased. Basal-like nonmalignant mammary epithelial cells also displayed an altered integrin adhesion molecular organization at the nanoscale, and recruited a suite of paxillin-associated proteins implicated in invasion and metastasis. Phosphorylation of paxillin by Src family kinases, which regulates adhesion turnover, was similarly enhanced in the metastatic and basal-like tumor cells, foste...
Adhesion-Dependent Cell Mechanosensitivity
Annual Review of Cell and Developmental Biology, 2003
▪ The conversion of physical signals, such as contractile forces or external mechanical perturbations, into chemical signaling events is a fundamental cellular process that occurs at cell–extracellular matrix contacts, known as focal adhesions. At these sites, transmembrane integrin receptors are associated via their cytoplasmic domains with the actin cytoskeleton. This interaction with actin is mediated by a submembrane plaque, consisting of numerous cytoskeletal and signaling molecules. Application of intrinsic or external forces to these structures dramatically affects their assembly and triggers adhesion-mediated signaling. In this review, we discuss the structure-function relationships of focal adhesions and the possible mode of action of the putative mechanosensor associated with them. We also discuss the general phenomenon of mechanosensitivity, and the approaches used to measure local forces at adhesion sites, the cytoskeleton-mediated regulation of local contractility, an...
The “Stressful” Life of Cell Adhesion Molecules: On the Mechanosensitivity of Integrin Adhesome
Journal of Biomechanical Engineering
Cells have evolved into complex sensory machines that communicate with their microenvironment via mechanochemical signaling. Extracellular mechanical cues trigger complex biochemical pathways in the cell, which regulate various cellular processes. Integrin-mediated focal adhesions (FAs) are large multiprotein complexes, also known as the integrin adhesome, that link the extracellular matrix (ECM) to the actin cytoskeleton, and are part of powerful intracellular machinery orchestrating mechanotransduction pathways. As forces are transmitted across FAs, individual proteins undergo structural and functional changes that involve a conversion of chemical to mechanical energy. The local composition of early adhesions likely defines the regional stress levels and determines the type of newly recruited proteins, which in turn modify the local stress distribution. Various approaches have been used for detecting and exploring molecular mechanisms through which FAs are spatiotemporally regulat...
Vinculin Promotes Cell Spreading by Mechanically Coupling Integrins to the Cytoskeleton
Experimental Cell Research, 1997
a complex of proteins that assemble at sites of attach-Mouse F9 embryonic carcinoma 5.51 cells that lack ment of the cell to the extracellular matrix . The the cytoskeletal protein vinculin spread poorly on ex-transmembrane proteins mediating these contacts are tracellular matrix compared with wild-type F9 cells members of the integrin family of extracellular matrix or two vinculin-transfected clones (5.51Vin3 and Vin4; (ECM) receptors. Integrins are heterodimeric com-Samuels et al., 1993, J. Cell Biol. 121, 909-921). In the plexes in which both chains span the plasma mempresent study, we used this model system to determine brane bilayer once, and the cytoplasmic domain is rehow the presence of vinculin promotes cytoskeletal alsponsible for linkage of the actin cytoskeleton. A numterations and associated changes in cell shape. Microber of proteins are found in focal adhesions at the scopic analysis of cell spreading at early times, reintracellular face of the plasma membrane, including vealed that 5.51 cells retained the ability to form filovinculin, a-actinin, paxillin, and talin [2, 3]. Which propodia; however, they could not form lamellipodia, teins are absolutely required for the formation of focal assemble stress fibers, or efficiently spread over the adhesions is still under investigation, and the order culture substrate. Detergent (Triton X-100) studies rewith which these proteins bind integrins, actin, or each vealed that these major differences in cell morphology other is only partly understood. In addition, changes and cytoskeletal organization did not result from difin cell shape and movement may require the transfer ferences in levels of total polymerized or cross-linked of mechanical forces between the cytoskeleton and actin. Biochemical studies showed that 5.51 cells, in ECM as well as changes in cytoskeletal organization addition to lacking vinculin, exhibited slightly re-[4-6]. The focal adhesion complex is a critical point duced levels of a-actinin and paxillin in their detergent-insoluble cytoskeleton. The absence of vinculin for the regulation of actin organization [1] as well as correlated with a decrease in the mechanical stiffness mechanical signal transfer [7]. Recently, Crowley and of the integrin-cytoskeleton linkage, as measured us-Horwitz [8] have shown tyrosine phosphorylation to ing cell magnetometry. Furthermore, when vinculin play a role in the signal transduction, the actin-based was replaced by transfection in 5.51Vin3 and 5.51Vin4 tension of focal contacts, and the release of cellular cells, the levels of cytoskeletal-associated a-actinin adhesions. and paxillin, the efficiency of transmembrane mechan-
Mechanosensitive components of integrin adhesions: Role of vinculin
Experimental Cell Research, 2016
External forces play a key role in shaping development and normal physiology. Aberrant responses to forces, or changes in the nature of such forces, are implicated in a variety of diseases. Cells contain several types of adhesions, linking them to their external environment. It is through these adhesions that forces are both sensed (from the outside inwards) and applied (from inside to out). Furthermore, several adhesionbased proteins are sensitive to changes in intracellular forces, utilising them for activation and regulation. Here, we outline how vinculin, a key component of integrin-mediated adhesions linking the actin cytoskeleton to the extracellular matrix (ECM), is regulated by force and acts as force transducing protein. We discuss the role of vinculin in vivo and its place in health and disease; summarise the proposed mechanisms by which vinculin is recruited to and activated at integrin-ECM adhesions; and discuss recent findings that place vinculin as the major force sensing and transmitting component of cell-matrix adhesion complexes. Finally, we discuss the role of vinculin in regulating the cellular responses to both the physical properties of the external environment and to externally applied physical stimuli.
Vinculin tension distributions of individual stress fibers within cell-matrix adhesions
Journal of Cell Science, 2013
Actomyosin stress fibers (SFs) enable cells to exert traction on planar extracellular matrices (ECMs) by tensing focal adhesions (FAs) at the cell-ECM interface. Although 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 highresolution 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.
Cell migration: regulation of force on extracellular-matrix-integrin complexes
Trends in Cell Biology, 1998
The migration of fibroblasts (and related cell types) has been described as a multistep process (see Fig. 1). Because all of the steps are necessary for migration, they form a cycle with no obvious starting point. Moreover, some steps might occur together in a concerted and interdependent fashion. Cells extend a leading edge that adheres to the substrate through specific receptors. These receptors are used to exert force on the substrate and pull this region of the cell forward. Eventually, adhesion sites are dissolved, the rear of the cell contracts forward and the receptors and other components of the adhesive complex can be recycled. The process of protrusion of the lamellipodium has been suggested to be driven by actin polymerization ~, and its mechanism is beyond the scope of this hypothesis paper. Similarly, the recycling of receptors has been dealt with elsewhere 2~. Recent reviews on the molecular basis of cell motility have addressed both the organization of the cytoskeleton s and the function of adhesion receptors in the generation of organized force 6. However, work published over the past year on cellular forces has important implications for our understanding of the process of cell migration. In this article, we consider the role of receptor-mediated generation of force in regulating the process of cell migration. By examining the regulation of receptor-cytoskeleton interactions and the magnitude and direction of the forces that these complexes exert on the external ECM molecules, we suggest new directions for the design of future experiments in the field of cell migration.
Nature Cell Biology, 2015
During cell migration, the forces generated in the actin cytoskeleton are transmitted across transmembrane receptors to the extracellular matrix or other cells through a series of mechanosensitive, regulable protein-protein interactions termed the molecular clutch. In integrinbased focal adhesions, the proteins forming this linkage are organized into a conserved threedimensional nano-architecture. Here we discuss how the physical interactions between the actin cytoskeleton and focal-adhesion-associated molecules mediate force transmission from the molecular clutch to the extracellular matrix. Cell migration is important during embryonic development, immune responses and wound healing, and can lead to inflammation and cancer metastasis when misregulated 1. Migration can occur through different mechanisms, including lamellipodia or pressure-driven bleb formation 2 , water permeation 3 and other processes 4,5 , depending on the cell type and tissue environment-a plasticity that facilitates robust migration in many contexts 1. However, the common feature of all these scenarios is that cells must be able to apply forces to generate traction against, and move themselves relative to, their immediate surroundings. The actin cytoskeleton is the major source of internally generated force that regulates cell shape and drives migration 6. Actin-based cellular forces must somehow be transmitted through the cell membrane to generate friction that induces traction against the extracellular environment. Friction between the cell and its environment can either be non-specific or mediated by specific surface receptors that bind to the extracellular matrix (ECM) or other cells. Nonspecific friction can be generated when cells are held under confinement, and is thought to drive non-haptotactic, bleb-based amoeboid motility during immune responses and cancer metastasis 7,8. Specific interactions between cells and their surroundings, such as integrin-ECM and cadherin-cadherin receptor-ligand interactions, drive haptotactic 'mesenchymal' motility during wound healing and development. This Review will focus on the physical mechanisms of cell-ECM traction generation during lamellipodia-and integrin-dependent mesenchymal cell migration.