Traction stress in focal adhesions correlates biphasically with actin retrograde flow speed.
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.
Gardel
Margaret L
ML
Department of Physics, University of Chicago, Chicago, IL 60637, USA.
Sabass
Benedikt
B
Ji
Lin
L
Danuser
Gaudenz
G
Schwarz
Ulrich S
US
Waterman
Clare M
CM
D000199:Actins / Q000378:metabolism*; D002465:Cell Movement; D022001:Focal Adhesions / Q000378:metabolism*; D024462:Myosin Type II / Q000378:metabolism; D011554:Pseudopodia / Q000378:metabolism; D012212:Rheology; D015398:Signal Transduction; D013312:Stress, Physiological; D020741:rho GTP-Binding Proteins / Q000378:metabolism
D000199:Actins; D024462:Myosin Type II; D020741:rho GTP-Binding Proteins