FIG. 7.

Host Rho activity is dispensable for InlB-mediated entry of Listeria. (A) Disruption of F-actin stress fibers by C3 toxin. HeLa cells left untreated (−) or treated with 2 μg/ml cell-permeative C3 for 5 h (+) were fixed and labeled with phalloidin coupled to Texas Red in order to detect the F-actin cytoskeleton. Untreated cells exhibit pronounced stress fibers, whereas stress fibers are largely absent in cells treated with C3. Scale bars, 10 μm. (B). Lack of inhibition of bacterial internalization by C3 exoenzyme treatment. HeLa cells pretreated (+) or not (−) with cell-permeative C3 toxin were infected with wild-type (Wt) or ΔinlB strains of Listeria, and entry was measured using gentamicin protection assay (37). Despite the strong inhibitory effect of C3 on the F-actin cytoskeleton (A), the toxin did not impair entry of Listeria. Data are averages ± SD from three experiments. *, P < 0.01 compared to untreated cells infected with wild-type Listeria.