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Traction stress in focal adhesions correlates biphasically with actin retrograde flow speed.

Gardel ML, Sabass B, Ji L, Danuser G, Schwarz US, Waterman CM - J. Cell Biol. (2008)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, University of Chicago, Chicago, IL 60637, USA.

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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Inhibition of myosin II activity constrains traction to the lamellipodium. (A–C) Cells were treated with 50 μM blebbistatin (+BLEB). (A) Heat scale plot of traction stress magnitude. (B) Mean traction stress (green) and F-actin speed (blue) as a function of distance from leading cell edge. (C) Immunofluorescence image of paxillin (red) and F-actin (green). Bars, 5 μm.
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fig2: Inhibition of myosin II activity constrains traction to the lamellipodium. (A–C) Cells were treated with 50 μM blebbistatin (+BLEB). (A) Heat scale plot of traction stress magnitude. (B) Mean traction stress (green) and F-actin speed (blue) as a function of distance from leading cell edge. (C) Immunofluorescence image of paxillin (red) and F-actin (green). Bars, 5 μm.

Mentions: To determine if traction stresses are spatially restricted to cellular regions of F-actin motion, we selectively abrogated myosin II–driven F-actin flow in the lamella with 50 μM blebbistatin, leaving F-actin motion driven by filament elongation in the lamellipodium intact (Straight et al., 2003; Ponti et al., 2004; Fig. 2 B and Video 3, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Surprisingly, stresses in the lamellipodium of blebbistatin-treated and control cells were similar (Fig. 2, A and B). Small FAs were primarily concentrated at the lamellipodium base where stresses peaked, but were also present in the lamella where stresses were negligible (Fig. 2 C and Fig. S1). Thus, traction stresses are spatially correlated with FAs in regions with coherent F-actin motion. Further, actin polymerization forces in the lamellipodium are sufficient to generate traction and mediate leading edge protrusion independent of myosin II activity.


Traction stress in focal adhesions correlates biphasically with actin retrograde flow speed.

Gardel ML, Sabass B, Ji L, Danuser G, Schwarz US, Waterman CM - J. Cell Biol. (2008)

Inhibition of myosin II activity constrains traction to the lamellipodium. (A–C) Cells were treated with 50 μM blebbistatin (+BLEB). (A) Heat scale plot of traction stress magnitude. (B) Mean traction stress (green) and F-actin speed (blue) as a function of distance from leading cell edge. (C) Immunofluorescence image of paxillin (red) and F-actin (green). Bars, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2600750&req=5

fig2: Inhibition of myosin II activity constrains traction to the lamellipodium. (A–C) Cells were treated with 50 μM blebbistatin (+BLEB). (A) Heat scale plot of traction stress magnitude. (B) Mean traction stress (green) and F-actin speed (blue) as a function of distance from leading cell edge. (C) Immunofluorescence image of paxillin (red) and F-actin (green). Bars, 5 μm.
Mentions: To determine if traction stresses are spatially restricted to cellular regions of F-actin motion, we selectively abrogated myosin II–driven F-actin flow in the lamella with 50 μM blebbistatin, leaving F-actin motion driven by filament elongation in the lamellipodium intact (Straight et al., 2003; Ponti et al., 2004; Fig. 2 B and Video 3, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Surprisingly, stresses in the lamellipodium of blebbistatin-treated and control cells were similar (Fig. 2, A and B). Small FAs were primarily concentrated at the lamellipodium base where stresses peaked, but were also present in the lamella where stresses were negligible (Fig. 2 C and Fig. S1). Thus, traction stresses are spatially correlated with FAs in regions with coherent F-actin motion. Further, actin polymerization forces in the lamellipodium are sufficient to generate traction and mediate leading edge protrusion independent of myosin II activity.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, University of Chicago, Chicago, IL 60637, USA.

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.

Show MeSH
Related in: MedlinePlus