title: Mechanical forces facilitate actin polymerization at focal adhesions in a zyxin-dependent manner.
abstract: We examined the effects of mechanical forces on actin polymerization at focal adhesions (FAs). Actin polymerization at FAs was assessed by introducing fluorescence-labeled actin molecules into permeabilized fibroblasts cultured on fibronectin. When cell contractility was inhibited by the myosin-II inhibitor blebbistatin, actin polymerization at FAs was diminished, whereas alpha(5)beta(1) integrin remained accumulated at FAs. This suggests that actin polymerization at FAs depends on mechanical forces. To examine the action of mechanical forces more directly, the blebbistatin-treated cells were subjected to a sustained uniaxial stretch, which induced actin polymerization at FAs. These results demonstrate the novel role of mechanical forces in inducing actin polymerization at FAs. To reveal the molecular mechanism underlying the force-induced actin polymerization at FAs, we examined the distribution of zyxin, a postulated actin-regulatory protein. Actin-polymerizing activity was strong at zyxin-rich FAs. Accumulation of zyxin at FAs was diminished by blebbistatin, whereas uniaxial stretching of the cells induced zyxin accumulation. Displacing endogenous zyxin from FAs by expressing the FA-targeting region of zyxin decreased the force-induced actin polymerization at FAs. These results suggest that zyxin is involved in mechanical-force-dependent facilitation of actin polymerization at FAs.
authors.affiliation: Cell Mechanosensing Project, ICORP/SORST, Japan Science and Technology Agency, 65 Tsurumai, Showa-ku, Nagoya, Aichi 466-8550, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hirata
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tatsumi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sokabe
mesh_terms: D000199:Actins / Q000378:metabolism*; D001696:Biomechanical Phenomena; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D005353:Fibronectins / Q000494:pharmacology; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D039564:Integrin alphaV / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism; D024462:Myosin Type II / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016608:Talin / Q000378:metabolism; D060589:Zyxin
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D005353:Fibronectins; D006023:Glycoproteins; D039564:Integrin alphaV; D019012:Integrin beta1; D011993:Recombinant Fusion Proteins; D016608:Talin; C092842:ZYX protein, human; D060589:Zyxin; D049452:Green Fluorescent Proteins; D024462:Myosin Type II