As described above, the BarA/SirA system is involved MK-8776 cell line in not only the flagella gene expression but also the SPI-1 gene expression. Phosphorylated SirA directly interacts with promoters of

the hilA and hilC genes that are the SPI-1-encoded transcription regulator genes [58]. HilA, a member of the OmpR/ToxR family, directly activates transcription of the inv/spa and prg/org promoters on SPI-1 [59]. In addition to the BarA/SirA system, the AraC-like regulator RitA directly controls the hilA expression leading to SPI-1 gene expression, while RitB, a helix-turn-helix DNA binding protein, negatively regulates the expression of the flhDC [60]. Reports also show that the ATP-dependent ClpXP protease negatively regulates the expression of flagella and SPI-1 gene [54, 61]. Interestingly, mutation in the SPI-2 genes also affects the expression of the SPI-1 gene [62]. And thus many reports show the relationship of flagella synthesis and SPI-1 gene expression.

Our S3I-201 solubility dmso recent studies show that the SpiC-dependent expression of FliC plays a significant role in activation of the signaling pathways leading to the induction of SOCS-3, which is involved in the inhibition of cytokine signaling, in Salmonella-infected macrophages [16]. Lyons et al. [63] also reported that infection of polarized epithelial cells by Salmonella leads to IL-8 expression by causing the SPI-2-dependent translocation of flagellin to a basolateral membrane Bay 11-7085 domain expressing

TLR5. Together with our previous results, these findings suggest the involvement of FliC in SPI-2-dependent events in the pathogenesis of Salmonella infection. Conclusion In conclusion, here we show that SpiC encoded within SPI-2 is required for flagella assembly in S. enterica serovar Typhimurium. We concluded that the mechanism is due to the involvement of SpiC in the post-transcriptional expression of FlhDC. The data indicate the possibility that SPI-2 plays a role in Salmonella virulence by making use of the flagellar system. Methods Bacterial strains, plasmids, and growth conditions The bacterial strains used in this study were derived from the wild-type S. enterica serovar Typhimurium strain 14028s. The spiC::kan derivative EG10128 was described by Uchiya et al. [7]. The deletion mutant in the flhD gene was constructed using the Red recombination system [64]. To delete the flhD or spiC gene, a kanamycin resistance gene flanked by FLP recognition target sites from plasmid pKD4 was amplified using PCR with primer regions homologous to the flhD gene (5′-TGCGGCTACGTCGCACAAAAATAAAGTTGGTTATTCTGGATGGGAGTGTAGGCTGGAGCTGCTTC-3′ and 5′-CGCGAGCTTCCTGAACAATGCTTTTTTCACTCATTATCATGCCCTCATATGAATATCCTCCTTAGT-3′) or the spiC gene (5′-TTGTGAGCGAATTTGATAGAAACTCCCATTTATGTCTGAGGAGGGGTGTAGGCTGGAGCTGCTTC-3′ and 5′-AGATTAAACGTTTATTTACTACCATTTTATACCCCACCCGAATAACATATGAATATCCTCCTTAGT-3′).