Figure 3

Erk 1/2 is necessary for cytosolic signaling required for maximal C. jejuni invasion of host cell. A. INT 407 cells were infected with C. jejuni incubated for 6 h, and IL-8 quantified using an IL-8 ELISA. The transcription inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) was added to INT 407 cells for 30 min prior to infection with a C. jejuni wild-type strain. B. Transcription is not required for C. jejuni invasion. INT 407 cells were infected with C. jejuni and invasion was assessed. C. CiaD is required for serine phosphorylation of cortactin. INT 407 cells were infected with the various C. jejuni strains and cellular lysates were prepared. Blots were probed with phospho-specific antibodies to cortactin. The blot was stripped and re-probed with an α-cortactin antibody. Densitometry of p-cortactin is shown as the ratio of p-cortactin to total cortactin (t-cortactin) for each sample. D. Erk 1/2 is required for serine phosphorylation of cortactin. INT 407 cells were pre-treated with PD98059, an inhibitor of Erk 1/2 activation, and infected with a C. jejuni wild-type strain. Blots were probed with a phospho-specific antibody to cortactin. The blot was stripped and re-probed with an α-tubulin antibody. Molecular masses, in kilodaltons (kDa), are indicated on the left. The asterisks indicate a significant difference (P < 0.01) compared to the value obtained for the C. jejuni wild-type strain, as judged by one-way ANOVA followed by post-hoc Dunnett’s analysis. N.S. indicates no significant difference.