Fig. 5. TPA-induced reorganization of actin filaments at the cell periphery. (A-C) Serumstarved A431 cells (control) fixed, permeabilized and stained with rhodamine-labeled phalloidin to visualize filamentous actin. (D-I) Serum-starved A431 cells incubated with 0.5 µM TPA for 1, 2, 3, 4, 8 or 10 minutes at 37°C and then processed as the control cells to visualize filamentous actin. Note that distinct stress fibers at the free surface of the cells rapidly disappear and are replaced by actin associated with ruffles as well as an apparent increase in actin staining at the lateral membranes (D-I).