FIG 3.

Overexpression of hilD or invF rescues the ΔinvS mutant invasion defect. (A, B) HeLa cells were infected with the indicated Salmonella strains for 15 min at an MOI of 10. Relative bacterial invasion was determined by the gentamicin protection assay. The data shown were obtained from three independent experiments. Error bars indicate standard deviations. P values were calculated using the Student t test. (C) InvS does not change the expression level of hilD or invF. The lacZ reporter gene was placed under transcriptional control of the hilD or invF promoter in either the wild type or the ΔinvS mutant Salmonella strain. β-Galactosidase activity assay was measured as described in Materials and Methods. The data shown were obtained from three independent experiments. Results are presented as the means in Miller units. Error bars indicate standard deviations. (D) InvS does not change the expression of hilD-gfp or invF-gfp. The 5′ UTR along with the full ORFs of HilD and InvF were translationally fused to GFP. Plasmids expressing HilD-GFP or InvF-GFP were cotransformed with plasmids expressing InvS or a vector control as indicated. HilD-GFP or InvF-GFP was detected by Western blotting with polyclonal anti-GFP antibodies. Bacterial isocitrate dehydrogenase (ICDH) was similarly detected using anti-ICDH polyclonal antibodies as the loading control.