title: Salmonella typhimurium leucine-rich repeat proteins are targeted to the SPI1 and SPI2 type III secretion systems.
abstract: 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.
authors.affiliation: Department of Microbiology, University of Washington, Seattle 98195, USA.
authors.forename: E A
authors.initials: EA
authors.lastname: Miao
authors.forename: C A
authors.initials: CA
authors.lastname: Scherer
authors.forename: R M
authors.initials: RM
authors.lastname: Tsolis
authors.forename: R A
authors.initials: RA
authors.lastname: Kingsley
authors.forename: L G
authors.initials: LG
authors.lastname: Adams
authors.forename: A J
authors.initials: AJ
authors.lastname: Bäumler
authors.forename: S I
authors.initials: SI
authors.lastname: Miller
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002417:Cattle; D017124:Conserved Sequence; D005798:Genes, Bacterial; D006367:HeLa Cells; D006801:Humans; D007930:Leucine / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D012486:Salmonella typhimurium / Q000378:metabolism* / Q000472:pathogenicity; D012703:Serotyping; D015533:Transcriptional Activation; D014774:Virulence
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C063500:ipaH protein, Shigella flexneri; C060772:yopM protein, Yersinia; D007930:Leucine