title: Traction stress in focal adhesions correlates biphasically with actin retrograde flow speed.
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.
authors.affiliation: Department of Physics, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Gardel
authors.forename: Benedikt
authors.initials: B
authors.lastname: Sabass
authors.forename: Lin
authors.initials: L
authors.lastname: Ji
authors.forename: Gaudenz
authors.initials: G
authors.lastname: Danuser
authors.forename: Ulrich S
authors.initials: US
authors.lastname: Schwarz
authors.forename: Clare M
authors.initials: CM
authors.lastname: Waterman
mesh_terms: 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
chemical_list: D000199:Actins; D024462:Myosin Type II; D020741:rho GTP-Binding Proteins