Figure 2.

Coherent FA growth and a two-peak traction profile explains FA-localized traction peak oscillation. (A) Centripetal FA growth coupled with membrane protrusion. (B) Predicted FA-localized spatial-temporal profiles of FA components and traction force during FA growth. (i) FA growth coupled with and reciprocally impeding the local retrograde actin flux. (ii) Spatial-temporal evolution of FA traction force that eventually leads to a two-peak traction profile. (iii) Spatiotemporal evolution of PTK activity. (iv) FA drifting components promote centripetal FA growth downstream of the retrograde actin flux. (C) The model predicts that competition between the distal traction peak and the oscillating central traction peak underlies the observed spatial-temporal traction peak oscillation. (D) Traction force microscopy (TFM) experiments illustrate the existence of the two-peak traction profile, with only the central peak oscillating in amplitude. For (C) and (D), the red dots in (i) represent the location of the FA traction maximum, and the FA domains reflect the FA intensity profiles subtracting the fluorescence intensity that is 10% higher than background signals for better contrasts (see Fig. S5 for details). The colored lines in (ii) represent the FA traction profiles along the central line of the FA domains at different times that are not calibrated by backgrounds. (E) Traction peak position distribution. The 0 μm in the x axis indicates the most proximal peak position (toward the center of the FA) for each FA. n = 109 frames from eight FAs in five cells, with each frame taken at 5 s intervals. To see this figure in color, go online.