Fig. 4.

Translocated SpvC prevents Erk phosphorylation upon PMA stimulation. A. J774 cells were infected for 16 h with the indicated Salmonella strains (blue in merged images), then Erk activation was triggered by 15 min of incubation with PMA (1 μg ml⁻¹). To assess Erk activation total Erk and phosphorylated Erk (pErk) were visualized with antibodies (red and green, respectively, in merged images). Similar results were obtained for HeLa cells (data not shown). B. Western blot analysis of the phosphorylation state of Erk in J774 macrophages infected with different Salmonella strains. Lysates of infected cells were probed for pErk and total Erk. Brackets indicate two forms of the kinase detected Erk1 (44 kDa) and Erk2 (42 kDa). pErk bands were quantified using Scion Image software. In both A and B uninfected cells were used as a control for the efficiency of PMA stimulation.