Therefore, in the absence of a functional flagella secretion apparatus (due to inactivation of fliI), FliC export still occurred if the LEE-encoded T3SS was intact. The involvement of the flagellin chaperone, FliS, in FliC secretion by the LEE-encoded T3SS was examined by constructing a double ΔfliI/fliS mutant. Flagellin expressed from pFliC was secreted by theΔfliI/fliS mutant in equivalent amounts to ΔfliI (pFliC) suggesting that the FliS chaperone was not involved in LEE-dependent FliC secretion (data not shown). To determine whether FliC was recognized

find more as an effector or a translocator by the LEE-encoded T3SS, we also examined FliC export by a sepL mutant. The mutation of sepL leads to preferential secretion of effectors and reduced secretion of translocators [28, 29]. We found that the sepL mutant secreted flagellin in equivalent amounts to the ΔespADB mutant suggesting that FliC was recognized as an effector of the LEE-encoded T3SS (data not shown). Figure 4 Immunoblot analysis of secreted proteins (SN) and whole cell lysates (WCL) prepared from derivatives of EPEC E2348/69 grown in hDMEM. Arrows indicate position ABT-263 concentration of a reactive

band corresponding to FliC detected with anti-H6 FliC check details antibodies or DnaK detected with anti-DnaK antibodies. FliC expression was induced in vitro with 1 mM IPTG from the trc promoter in pTrc99A. Flagellin exported by the LEE T3SS induces NF-kappa B activity but does not confer motility Previous work has shown that FliC from EPEC E2348/69 can stimulate proinflammatory cytokine production through TLR5 signaling [30]. Indeed, EPEC H6 flagellin is a potent activator of interleukin-8 release in T84 and HT-29 intestinal epithelial cells [24, 31]. Here we investigated host cell signaling in response to EPEC E2348/69 flagellin by measuring NF-kappa B activation in human embryonic kidney HEK293 cells using an NF-kappa B dependent luciferase

reporter assay. Dipeptidyl peptidase Since HEK293 cells possess functional TLR5 and non-functional forms of TLR2 and TLR4, the cell line is most likely responsive only to flagellin and not to Gram-negative lipoproteins and lipopolysaccharide [32]. As expected, there was a correlation between the presence of FliC in the bacterial culture supernatant and NF-kappa B activation (Fig. 5). Although the activation of NF-kappa B by wild type EPEC E2348/69 supernatant proteins (Fig. 5B) appeared lower than strains producing the same amount of FliC (Fig. 5A), the western blot presented represented one experiment only and NF-kappa B activation was performed more than three times using different preparations of supernatant proteins.