Figure 7. VASP-depletion leads to a decrease in tension-sensitive actin polymerization at focal adhesions.
(A) Actin polymerization at focal adhesions was monitored by fluorescence recovery after photobleaching (FRAP) in laser-ablated ventral stress fibers of control cells and VASP knockdown cells. FRAP experiments were initiated 10 seconds after ablation. Yellow arrowheads indicate the ablation sites and red boxes the regions of stress fibers that were followed for vectorial actin polymerization. Kymographs on the right were recorded along the center of the ablated ventral stress fibers. Release of tension induces vectorial actin polymerization from the adhesion located at the end of an ablated ventral stress fiber in a control cell, whereas the rate of vectorial actin polymerization was slower in an ablated ventral stress fiber in a VASP-depleted cell. Bar, 10 um. (B) Quantification of vectorial actin polymerization rates in intact ventral stress fibers, in ablated ventral stress fibers of control cells, and in ablated ventral stress fibers of VASP-depleted cells. Mean +/- SEM is shown; n (intact ventral stress fibers) = 17; n (ablated ventral stress fibers) = 12; n (ablated ventral stress fibers from VASP knockdown cells) = 17.