부산대학교 도서관

During apical colonization by Salmonella typhimurium, intestinal epithelial cells orchestrate a proinflammatory response that involves secretion of chemoattractants, predominantly interleukin-8, which coordinate neutrophil trans-epithelial migration at the site of infection. This host-pathogen interaction requires several S. typhimuriumgenes. To identify novel genes that participate in this pathogen-induced proinflammatory response, we created S. typhimuriumTn-10 transposon mutants and identified a single mutant with Tn-10 insertional inactivation within the fliEflagellar locus that was able to adhere to and invade intestinal epithelial cells normally but was unable to induce interleukin-8 secretion in host cells. The fliE-deficient mutant failed to secrete flagellin and lacked any surface assembly of flagellae. Unlike wild-type S. typhimurium, the fliE-deficient mutant did not activate the IκBα/NF-κB signaling pathway or induce the coordinated trans-epithelial migration of isolated human neutrophils. Transcomplementation of the fliE-deficient mutant with a wild-type fliE-harboring plasmid restored all defects and produced a wild-type S. typhimuriumphenotype. Furthermore, functional down-regulation of basolateral TLR5 completely inhibited the monolayers' ability to respond to both wild-type S. typhimuriumand purified flagellin but had no affect on tumor necrosis factor α-induced responses. We therefore conclude that S. typhimurium fliEis essential for flagellin secretion, flagellar assembly, and S. typhimurium-induced proinflammatory responses through basolateral TLR5 and is consistent with the emerging model of S. typhimuriumflagellin-induced inflammation.