Traction stress in focal adhesions correlates biphasically with actin retrograde flow speed |
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| Authors: | Margaret L. Gardel Benedikt Sabass Lin Ji Gaudenz Danuser Ulrich S. Schwarz Clare M. Waterman |
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| Affiliation: | 1.Department of Physics, University of Chicago, Chicago, IL 60637;2.BIOQUANT, Heidelberg University, 69120 Heidelberg, Germany;3.Institute of Zoology, University of Karlsruhe and Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany;4.Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037;5.National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892 |
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| Abstract: | How focal adhesions (FAs) convert retrograde filamentous actin (F-actin) flow into traction stress on the extracellular matrix to drive cell migration is unknown. Using combined traction force and fluorescent speckle microscopy, we observed a robust biphasic relationship between F-actin speed and traction force. F-actin speed is inversely related to traction stress near the cell edge where FAs are formed and F-actin motion is rapid. In contrast, larger FAs where the F-actin speed is low are marked by a direct relationship between F-actin speed and traction stress. We found that the biphasic switch is determined by a threshold F-actin speed of 8–10 nm/s, independent of changes in FA protein density, age, stress magnitude, assembly/disassembly status, or subcellular position induced by pleiotropic perturbations to Rho family guanosine triphosphatase signaling and myosin II activity. Thus, F-actin speed is a fundamental regulator of traction force at FAs during cell migration. |
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