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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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Inverse and direct correlations between traction stress and F-actin speed occur over similar ranges of F-actin speed despite perturbations to myosin II and Rho GTPase signaling. (A–D) Data ranges indicating the strongest inverse (blue) or direct (red) correlation between traction stress and F-actin speed (Fig. S3, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Large blue and red arrows mark vs and vw, the F-actin speed delineating the upper and lower bounds, respectively, of the speed ranges. Gray symbols represent data outside the ranges; lines with slopes ms and mw show linear fits to data within the ranges. Small blue and red arrows mark σs and σw, the traction stress at vs and vw. Characteristic data are shown for control (A), blebbistatin-treated cells (B), and overexpression of CA-Rac (C) and CA-Rho (D). Mean slopes ms (E, blue) and mw (E, red), traction stresses σs (F, blue) and σw (F, red), and velocities vs (G, blue) and vw (G, red) for different conditions. In E–G, data reflects a mean of >1,000 data points for n = 3 cells. (H) Model for how F-actin dynamics are variably coupled to traction stress by initiation and assembly of FAs across the cell front; differently shaded regions reflect changes in the magnitude of traction stress measured at similar F-actin speeds for different conditions. Position within the cell front shown below; black bars represent FAs and crosshatching represents F-actin.
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fig5: Inverse and direct correlations between traction stress and F-actin speed occur over similar ranges of F-actin speed despite perturbations to myosin II and Rho GTPase signaling. (A–D) Data ranges indicating the strongest inverse (blue) or direct (red) correlation between traction stress and F-actin speed (Fig. S3, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Large blue and red arrows mark vs and vw, the F-actin speed delineating the upper and lower bounds, respectively, of the speed ranges. Gray symbols represent data outside the ranges; lines with slopes ms and mw show linear fits to data within the ranges. Small blue and red arrows mark σs and σw, the traction stress at vs and vw. Characteristic data are shown for control (A), blebbistatin-treated cells (B), and overexpression of CA-Rac (C) and CA-Rho (D). Mean slopes ms (E, blue) and mw (E, red), traction stresses σs (F, blue) and σw (F, red), and velocities vs (G, blue) and vw (G, red) for different conditions. In E–G, data reflects a mean of >1,000 data points for n = 3 cells. (H) Model for how F-actin dynamics are variably coupled to traction stress by initiation and assembly of FAs across the cell front; differently shaded regions reflect changes in the magnitude of traction stress measured at similar F-actin speeds for different conditions. Position within the cell front shown below; black bars represent FAs and crosshatching represents F-actin.

Mentions: We next quantitatively characterized the biphasic relationship between traction stress and F-actin speed. We determined the range of F-actin speeds over which the data exhibited the strongest inverse (Fig. 5, A–D, blue; and Fig. S3, E and F, blue) and direct (red) linear correlations, although the data does not preclude the possibility of higher-ordered polynomial fits. The absolute values of the slopes (ms and mw) represent the efficiency of conversion of F-actin motion into traction stress by FAs. σs and σw are the mean peak stresses at the F-actin speeds, vs and vw (Fig. 5, A–D, arrows), over which the strongest inverse and direct correlations between stress and F-actin speed are found. In cells treated with blebbistatin or expressing CA-Rac, σs and σw were lower than those in controls, whereas in cells expressing CA-Rho, σs and σw were higher than controls (Fig. 5 F). Interestingly, ms was weakly sensitive, but mw was highly sensitive to perturbation (Fig. 5 E). Thus, myosin II activity and/or Rho GTPase signaling do not affect the conversion efficiency of rapid F-actin motion to traction stress during FA initiation, but do so at lower F-actin speeds in larger FAs. Remarkably, vs and vw were not significantly altered (Fig. 5 G) across perturbations. Thus, the F-actin speed where force transmission through FA change from an inverse relationship with F-actin speed to a direct relationship is constant and independent of contractility and Rho GTPase signaling.


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)

Inverse and direct correlations between traction stress and F-actin speed occur over similar ranges of F-actin speed despite perturbations to myosin II and Rho GTPase signaling. (A–D) Data ranges indicating the strongest inverse (blue) or direct (red) correlation between traction stress and F-actin speed (Fig. S3, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Large blue and red arrows mark vs and vw, the F-actin speed delineating the upper and lower bounds, respectively, of the speed ranges. Gray symbols represent data outside the ranges; lines with slopes ms and mw show linear fits to data within the ranges. Small blue and red arrows mark σs and σw, the traction stress at vs and vw. Characteristic data are shown for control (A), blebbistatin-treated cells (B), and overexpression of CA-Rac (C) and CA-Rho (D). Mean slopes ms (E, blue) and mw (E, red), traction stresses σs (F, blue) and σw (F, red), and velocities vs (G, blue) and vw (G, red) for different conditions. In E–G, data reflects a mean of >1,000 data points for n = 3 cells. (H) Model for how F-actin dynamics are variably coupled to traction stress by initiation and assembly of FAs across the cell front; differently shaded regions reflect changes in the magnitude of traction stress measured at similar F-actin speeds for different conditions. Position within the cell front shown below; black bars represent FAs and crosshatching represents F-actin.
© Copyright Policy
Related In: Results  -  Collection

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

fig5: Inverse and direct correlations between traction stress and F-actin speed occur over similar ranges of F-actin speed despite perturbations to myosin II and Rho GTPase signaling. (A–D) Data ranges indicating the strongest inverse (blue) or direct (red) correlation between traction stress and F-actin speed (Fig. S3, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Large blue and red arrows mark vs and vw, the F-actin speed delineating the upper and lower bounds, respectively, of the speed ranges. Gray symbols represent data outside the ranges; lines with slopes ms and mw show linear fits to data within the ranges. Small blue and red arrows mark σs and σw, the traction stress at vs and vw. Characteristic data are shown for control (A), blebbistatin-treated cells (B), and overexpression of CA-Rac (C) and CA-Rho (D). Mean slopes ms (E, blue) and mw (E, red), traction stresses σs (F, blue) and σw (F, red), and velocities vs (G, blue) and vw (G, red) for different conditions. In E–G, data reflects a mean of >1,000 data points for n = 3 cells. (H) Model for how F-actin dynamics are variably coupled to traction stress by initiation and assembly of FAs across the cell front; differently shaded regions reflect changes in the magnitude of traction stress measured at similar F-actin speeds for different conditions. Position within the cell front shown below; black bars represent FAs and crosshatching represents F-actin.
Mentions: We next quantitatively characterized the biphasic relationship between traction stress and F-actin speed. We determined the range of F-actin speeds over which the data exhibited the strongest inverse (Fig. 5, A–D, blue; and Fig. S3, E and F, blue) and direct (red) linear correlations, although the data does not preclude the possibility of higher-ordered polynomial fits. The absolute values of the slopes (ms and mw) represent the efficiency of conversion of F-actin motion into traction stress by FAs. σs and σw are the mean peak stresses at the F-actin speeds, vs and vw (Fig. 5, A–D, arrows), over which the strongest inverse and direct correlations between stress and F-actin speed are found. In cells treated with blebbistatin or expressing CA-Rac, σs and σw were lower than those in controls, whereas in cells expressing CA-Rho, σs and σw were higher than controls (Fig. 5 F). Interestingly, ms was weakly sensitive, but mw was highly sensitive to perturbation (Fig. 5 E). Thus, myosin II activity and/or Rho GTPase signaling do not affect the conversion efficiency of rapid F-actin motion to traction stress during FA initiation, but do so at lower F-actin speeds in larger FAs. Remarkably, vs and vw were not significantly altered (Fig. 5 G) across perturbations. Thus, the F-actin speed where force transmission through FA change from an inverse relationship with F-actin speed to a direct relationship is constant and independent of contractility and Rho GTPase signaling.

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