Limits...
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.

Show MeSH

Related in: MedlinePlus

Traction stress is biphasically correlated with F-actin speed in FAs. (A) Traction stress versus F-actin speed for all points throughout the cell front over 25 frames of a time-lapse movie. (B) Subset of traction stress versus F-actin speed from A for data located within segmented FAs. Data were grouped by F-actin speed (greater or less than 10 nm/s) and three values of traction stress (<20, 20–50, and >50 Pa) to obtain six “stress-speed” groups identified by different colors/symbols. (C) Inverted GFP-paxillin image with spatial location of stress-speed data groups plotted in B (Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Bar, 3 μm. (D, top) Montage of GFP-paxillin images of a single FA over 15 min (Video 5). For each time point, the integrated area (second row), GFP-paxillin intensity (third row), traction stress (fourth row), and local F-actin speed (bottom) were determined. In the fourth row, the dashed line indicates 75% of maximum stress; the arrow indicates time (ts) when traction stress exceeds this threshold. (E) F-actin speed at ts (v(ts)) as a function of ts. Mean of v(ts) = 12.7 ± 3 nm/s. Mean of ts = 3 ± 2 min. (F) v(ts) as a function of traction stress at ts, σ(ts). Mean of σ(ts) = 65 ± 28 Pa. Data in E and F are from 26 FAs in four cells.
© Copyright Policy
Related In: Results  -  Collection

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

fig3: Traction stress is biphasically correlated with F-actin speed in FAs. (A) Traction stress versus F-actin speed for all points throughout the cell front over 25 frames of a time-lapse movie. (B) Subset of traction stress versus F-actin speed from A for data located within segmented FAs. Data were grouped by F-actin speed (greater or less than 10 nm/s) and three values of traction stress (<20, 20–50, and >50 Pa) to obtain six “stress-speed” groups identified by different colors/symbols. (C) Inverted GFP-paxillin image with spatial location of stress-speed data groups plotted in B (Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Bar, 3 μm. (D, top) Montage of GFP-paxillin images of a single FA over 15 min (Video 5). For each time point, the integrated area (second row), GFP-paxillin intensity (third row), traction stress (fourth row), and local F-actin speed (bottom) were determined. In the fourth row, the dashed line indicates 75% of maximum stress; the arrow indicates time (ts) when traction stress exceeds this threshold. (E) F-actin speed at ts (v(ts)) as a function of ts. Mean of v(ts) = 12.7 ± 3 nm/s. Mean of ts = 3 ± 2 min. (F) v(ts) as a function of traction stress at ts, σ(ts). Mean of σ(ts) = 65 ± 28 Pa. Data in E and F are from 26 FAs in four cells.

Mentions: To determine the relationship between traction stress and F-actin speed magnitudes, we plotted the values from a time-lapse series for all grid positions throughout the cell front. This revealed a biphasic relationship, with highest stresses exerted at intermediate F-actin speeds (8–12 nm/s) and lower stresses exerted at the highest and lowest F-actin speeds (Fig. 3 A). Surprisingly, the distribution of F-actin speeds at the highest (>95%) stresses was Gaussian distributed around a mean of ∼8 nm/s (Fig. 1 G). Data from only within segmented FAs exhibited a similar biphasic relationship (Fig. 3 B). To identify where data populations of similar mean stress and F-actin speed were localized, we grouped the data in “stress/speed space” and mapped the points from each data group to their respective subcellular locations (Fig. 3 C and Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Interestingly, data groups mapped to distinct cell regions with specific FA morphology. The fastest F-actin speeds associated with low traction stresses (Fig. 3 C, magenta and navy) localized to small FAs in the lamellipodium and distal tips of larger FAs; the highest traction stresses at intermediate F-actin speeds (Fig. 3 C, cyan and green) mapped to distal and central portions of large FAs; slower F-actin speeds and lower traction stresses (Fig. 3 C, red and yellow) mapped to the central and proximal portions of large FAs. Thus, there is a biphasic relationship between F-actin speed and traction stress in FAs that changes from inverse to direct across the leading edge.


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)

Traction stress is biphasically correlated with F-actin speed in FAs. (A) Traction stress versus F-actin speed for all points throughout the cell front over 25 frames of a time-lapse movie. (B) Subset of traction stress versus F-actin speed from A for data located within segmented FAs. Data were grouped by F-actin speed (greater or less than 10 nm/s) and three values of traction stress (<20, 20–50, and >50 Pa) to obtain six “stress-speed” groups identified by different colors/symbols. (C) Inverted GFP-paxillin image with spatial location of stress-speed data groups plotted in B (Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Bar, 3 μm. (D, top) Montage of GFP-paxillin images of a single FA over 15 min (Video 5). For each time point, the integrated area (second row), GFP-paxillin intensity (third row), traction stress (fourth row), and local F-actin speed (bottom) were determined. In the fourth row, the dashed line indicates 75% of maximum stress; the arrow indicates time (ts) when traction stress exceeds this threshold. (E) F-actin speed at ts (v(ts)) as a function of ts. Mean of v(ts) = 12.7 ± 3 nm/s. Mean of ts = 3 ± 2 min. (F) v(ts) as a function of traction stress at ts, σ(ts). Mean of σ(ts) = 65 ± 28 Pa. Data in E and F are from 26 FAs in four cells.
© Copyright Policy
Related In: Results  -  Collection

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

fig3: Traction stress is biphasically correlated with F-actin speed in FAs. (A) Traction stress versus F-actin speed for all points throughout the cell front over 25 frames of a time-lapse movie. (B) Subset of traction stress versus F-actin speed from A for data located within segmented FAs. Data were grouped by F-actin speed (greater or less than 10 nm/s) and three values of traction stress (<20, 20–50, and >50 Pa) to obtain six “stress-speed” groups identified by different colors/symbols. (C) Inverted GFP-paxillin image with spatial location of stress-speed data groups plotted in B (Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Bar, 3 μm. (D, top) Montage of GFP-paxillin images of a single FA over 15 min (Video 5). For each time point, the integrated area (second row), GFP-paxillin intensity (third row), traction stress (fourth row), and local F-actin speed (bottom) were determined. In the fourth row, the dashed line indicates 75% of maximum stress; the arrow indicates time (ts) when traction stress exceeds this threshold. (E) F-actin speed at ts (v(ts)) as a function of ts. Mean of v(ts) = 12.7 ± 3 nm/s. Mean of ts = 3 ± 2 min. (F) v(ts) as a function of traction stress at ts, σ(ts). Mean of σ(ts) = 65 ± 28 Pa. Data in E and F are from 26 FAs in four cells.
Mentions: To determine the relationship between traction stress and F-actin speed magnitudes, we plotted the values from a time-lapse series for all grid positions throughout the cell front. This revealed a biphasic relationship, with highest stresses exerted at intermediate F-actin speeds (8–12 nm/s) and lower stresses exerted at the highest and lowest F-actin speeds (Fig. 3 A). Surprisingly, the distribution of F-actin speeds at the highest (>95%) stresses was Gaussian distributed around a mean of ∼8 nm/s (Fig. 1 G). Data from only within segmented FAs exhibited a similar biphasic relationship (Fig. 3 B). To identify where data populations of similar mean stress and F-actin speed were localized, we grouped the data in “stress/speed space” and mapped the points from each data group to their respective subcellular locations (Fig. 3 C and Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200810060/DC1). Interestingly, data groups mapped to distinct cell regions with specific FA morphology. The fastest F-actin speeds associated with low traction stresses (Fig. 3 C, magenta and navy) localized to small FAs in the lamellipodium and distal tips of larger FAs; the highest traction stresses at intermediate F-actin speeds (Fig. 3 C, cyan and green) mapped to distal and central portions of large FAs; slower F-actin speeds and lower traction stresses (Fig. 3 C, red and yellow) mapped to the central and proximal portions of large FAs. Thus, there is a biphasic relationship between F-actin speed and traction stress in FAs that changes from inverse to direct across the leading edge.

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