Effect of inhibiting small GTPases by bacterial toxins on p38 phosphorylation. (A, B) Serum-starved NIH3T3 cells were either not pretreated or preincubated for 23 h with 400 ng/ml of C2IN-C3 (C3), for 2 h with 200 ng/ml of Lethal Toxin (LT), or for 2.5 h with 10 ng/ml of Toxin B (TB). Cells were either not stimulated or stimulated for 30 min with FCS (A) or anisomycin (B). Western blot analysis was performed with a phospho-specific anti-p38-antibody followed by reprobing with anti-p38-antibody. (C) Presentation of the bacterial toxins used indicating their substrate specificity according to [29–31].