Effect of C3 exoenzyme on focal adhesions and stress fibers in A5 CHO cells adherent to fibrinogen. A5 CHO cells were cultured as in Fig 1 in the presence of vehicle buffer (A and C) or 20 μg/mL of C3 exoenzyme (B and D). The cells were then resuspended in Dulbecco's modified Essential medium and incubated over fibrinogen-coated coverslips for 60 minutes at 37°C. After washing away nonadherent cells, adherent cells were fixed, permeabilized, and stained for vinculin (A and B) or F-actin (C and D). Vinculin-positive focal adhesions and actin stress fibers were plentiful in the control cells, but not in the cells treated with C3 exoenzyme. The results are representative of three experiments. Bar = 5 μm.