title: Mechanical forces alter zyxin unbinding kinetics within focal adhesions of living cells.
abstract: The formation of focal adhesions that mediate alterations of cell shape and movement is controlled by a mechanochemical mechanism in which cytoskeletal tensional forces drive changes in molecular assembly; however, little is known about the molecular biophysical basis of this response. Here, we describe a method to measure the unbinding rate constant k(OFF) of individual GFP-labeled focal adhesion molecules in living cells by modifying the fluorescence recovery after photobleaching (FRAP) technique and combining it with mathematical modeling. Using this method, we show that decreasing cellular traction forces on focal adhesions by three different techniques--chemical inhibition of cytoskeletal tension generation, laser incision of an associated actin stress fiber, or use of compliant extracellular matrices--increases the k(OFF) of the focal adhesion protein zyxin. In contrast, the k(OFF) of another adhesion protein, vinculin, remains unchanged after tension dissipation. Mathematical models also demonstrate that these force-dependent increases in zyxin's k(OFF) that occur over seconds are sufficient to quantitatively predict large-scale focal adhesion disassembly that occurs physiologically over many minutes. These findings demonstrate that the molecular binding kinetics of some, but not all, focal adhesion proteins are sensitive to mechanical force, and suggest that force-dependent changes in this biophysical parameter may govern the supramolecular events that underlie focal adhesion remodeling in living cells.
authors.affiliation: Department of Surgery, Vascular Biology Program, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Tanmay P
authors.initials: TP
authors.lastname: Lele
authors.forename: Jay
authors.initials: J
authors.lastname: Pendse
authors.forename: Sanjay
authors.initials: S
authors.lastname: Kumar
authors.forename: Matthew
authors.initials: M
authors.lastname: Salanga
authors.forename: John
authors.initials: J
authors.lastname: Karavitis
authors.forename: Donald E
authors.initials: DE
authors.lastname: Ingber
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D015638:Cytochalasin D / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D036681:Fluorescence Recovery After Photobleaching; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D007834:Lasers; D008027:Light; D008856:Microscopy, Fluorescence; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D013314:Stress, Mechanical; D014162:Transfection; D016596:Vinculin / Q000235:genetics / Q000378:metabolism; D054460:rho-Associated Kinases
chemical_list: D000577:Amides; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; D016596:Vinculin; C108830:Y 27632; D049452:Green Fluorescent Proteins; D015638:Cytochalasin D; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases