Salmonella typhimurium leucine-rich repeat proteins are targeted to the SPI1 and SPI2 type III secretion systems
Article first published online: 1 MAR 2002
Volume 34, Issue 4, pages 850–864, November 1999
How to Cite
Miao, E. A., Scherer, C. A., Tsolis, R. M., Kingsley, R. A., Adams, L. G., Bäumler, A. J. and Miller, S. I. (1999), Salmonella typhimurium leucine-rich repeat proteins are targeted to the SPI1 and SPI2 type III secretion systems. Molecular Microbiology, 34: 850–864. doi: 10.1046/j.1365-2958.1999.01651.x
- Issue published online: 1 MAR 2002
- Article first published online: 1 MAR 2002
Salmonellae encode two virulence-associated type III secretion systems (TTSS) within Salmonella pathogenicity islands 1 and 2 (SPI1 and SPI2). Two Salmonella typhimurium genes, sspH1 and sspH2, that encode proteins similar to the Shigella flexneri and Yersinia species TTSS substrates, IpaH and YopM, were identified. SspH1 and SspH2 are proteins containing leucine-rich repeats that are differentially targeted to the SPI1 and SPI2 TTSS. sspH2 transcription was induced within RAW264.7 macrophages, and was dependent upon the SPI2-encoded regulator ssrA/ssrB. In contrast, sspH1 transcription is independent of SPI2, and is not induced after bacterial phagocytosis by eukaryotic cells. Infection of eukaryotic cells with strains expressing a SspH2–CyaA fusion protein resulted in SPI2 TTSS-dependent cAMP increases. In contrast, SspH1–CyaA-mediated cAMP increases were both SPI1 and SPI2 TTSS dependent. sspH2-like sequences were found in most Salmonella serotypes examined, whereas sspH1 was detected in only one S. typhimurium isolate, indicating that the copy number of sspH genes can be variable within Salmonella serotypes. S. typhimurium deleted for both sspH1 and sspH2 was not able to cause a lethal infection in calves, indicating that these genes participate in S. typhimurium virulence for animals.