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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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The switch from an inverse to a direct correlation between F-actin speed and traction stress does not require FA disassembly and occurs at a specific F-actin speed. (A) Traction stress versus F-actin speed for data within FAs for 15 frames of a time-lapse video of a cell expressing CA-Rac. Data are grouped as in Fig. 3 B. (B) Inverted GFP-paxillin image with spatial location of stress/speed data points plotted in A. Bar, 3 μm. See Video 7, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1. (C) Mean traction stress as a function of distance from cell edge (left) and F-actin speed (right). Characteristic data are shown for a control cell, treatment with 50 μM blebbistatin (BLEB), expression of CA-Rac, and expression of CA-Rho. (D) The mean (squares) and standard deviation (error bars) of the distance away from the cell edge (left) and F-actin speed (right) associated with peak (>95%) traction stresses. Data reflects the mean of >100 data points from three cells.
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fig4: The switch from an inverse to a direct correlation between F-actin speed and traction stress does not require FA disassembly and occurs at a specific F-actin speed. (A) Traction stress versus F-actin speed for data within FAs for 15 frames of a time-lapse video of a cell expressing CA-Rac. Data are grouped as in Fig. 3 B. (B) Inverted GFP-paxillin image with spatial location of stress/speed data points plotted in A. Bar, 3 μm. See Video 7, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1. (C) Mean traction stress as a function of distance from cell edge (left) and F-actin speed (right). Characteristic data are shown for a control cell, treatment with 50 μM blebbistatin (BLEB), expression of CA-Rac, and expression of CA-Rho. (D) The mean (squares) and standard deviation (error bars) of the distance away from the cell edge (left) and F-actin speed (right) associated with peak (>95%) traction stresses. Data reflects the mean of >100 data points from three cells.

Mentions: To establish if the transition from an inverse relationship to a direct relationship between F-actin speed and traction stress requires FA disassembly, we inhibited FA turnover dynamics by expressing constitutively active Rac1 (CA-Rac; Webb et al., 2004). CA-Rac also induces a wide lamellipodium with small FAs near the lamellipodium base and long, narrow FAs that extend into the cell body and do not disassemble in 30 min (Fig. S1 and Video 6, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). The magnitude of stresses in cells expressing CA-Rac was lower than control cells, possibly because of Rac-mediated down-regulation of myosin II activity (Sanders et al., 1999) or other changes in FA protein composition or posttranslational modification (Zaidel-Bar et al., 2007). F-actin speeds at FAs ranged from 0 to ∼30 nm/s, with the highest speeds in distal FAs near the cell edge and lowest speeds in FAs toward the cell body. Remarkably, in the absence of FA turnover, we still observed a biphasic relationship between stress and F-actin speed across FAs, with peak stresses exerted at intermediate speeds (Fig. 4, A and B; and Video 7). Thus, maximal traction stresses and the transition to a direct relationship between stress and F-actin speed occurs at intermediate F-actin speed, independent of FA disassembly.


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)

The switch from an inverse to a direct correlation between F-actin speed and traction stress does not require FA disassembly and occurs at a specific F-actin speed. (A) Traction stress versus F-actin speed for data within FAs for 15 frames of a time-lapse video of a cell expressing CA-Rac. Data are grouped as in Fig. 3 B. (B) Inverted GFP-paxillin image with spatial location of stress/speed data points plotted in A. Bar, 3 μm. See Video 7, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1. (C) Mean traction stress as a function of distance from cell edge (left) and F-actin speed (right). Characteristic data are shown for a control cell, treatment with 50 μM blebbistatin (BLEB), expression of CA-Rac, and expression of CA-Rho. (D) The mean (squares) and standard deviation (error bars) of the distance away from the cell edge (left) and F-actin speed (right) associated with peak (>95%) traction stresses. Data reflects the mean of >100 data points from three cells.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2600750&req=5

fig4: The switch from an inverse to a direct correlation between F-actin speed and traction stress does not require FA disassembly and occurs at a specific F-actin speed. (A) Traction stress versus F-actin speed for data within FAs for 15 frames of a time-lapse video of a cell expressing CA-Rac. Data are grouped as in Fig. 3 B. (B) Inverted GFP-paxillin image with spatial location of stress/speed data points plotted in A. Bar, 3 μm. See Video 7, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1. (C) Mean traction stress as a function of distance from cell edge (left) and F-actin speed (right). Characteristic data are shown for a control cell, treatment with 50 μM blebbistatin (BLEB), expression of CA-Rac, and expression of CA-Rho. (D) The mean (squares) and standard deviation (error bars) of the distance away from the cell edge (left) and F-actin speed (right) associated with peak (>95%) traction stresses. Data reflects the mean of >100 data points from three cells.
Mentions: To establish if the transition from an inverse relationship to a direct relationship between F-actin speed and traction stress requires FA disassembly, we inhibited FA turnover dynamics by expressing constitutively active Rac1 (CA-Rac; Webb et al., 2004). CA-Rac also induces a wide lamellipodium with small FAs near the lamellipodium base and long, narrow FAs that extend into the cell body and do not disassemble in 30 min (Fig. S1 and Video 6, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). The magnitude of stresses in cells expressing CA-Rac was lower than control cells, possibly because of Rac-mediated down-regulation of myosin II activity (Sanders et al., 1999) or other changes in FA protein composition or posttranslational modification (Zaidel-Bar et al., 2007). F-actin speeds at FAs ranged from 0 to ∼30 nm/s, with the highest speeds in distal FAs near the cell edge and lowest speeds in FAs toward the cell body. Remarkably, in the absence of FA turnover, we still observed a biphasic relationship between stress and F-actin speed across FAs, with peak stresses exerted at intermediate speeds (Fig. 4, A and B; and Video 7). Thus, maximal traction stresses and the transition to a direct relationship between stress and F-actin speed occurs at intermediate F-actin speed, independent of FA disassembly.

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