title: Salmonella maintains the integrity of its intracellular vacuole through the action of SifA.
abstract: A method based on the Competitive Index was used to identify Salmonella typhimurium virulence gene interactions during systemic infections of mice. Analysis of mixed infections involving single and double mutant strains showed that OmpR, the type III secretion system of Salmonella pathogenicity island 2 (SPI-2) and SifA [required for the formation in epithelial cells of lysosomal glycoprotein (lgp)-containing structures, termed Sifs] are all involved in the same virulence function. sifA gene expression was induced after Salmonella entry into host cells and was dependent on the SPI-2 regulator ssrA. A sifA(-) mutant strain had a replication defect in macrophages, similar to that of SPI-2 and ompR(-) mutant strains. Whereas wild-type and SPI-2 mutant strains reside in vacuoles that progressively acquire lgps and the vacuolar ATPase, the majority of sifA(-) bacteria lost their vacuolar membrane and were released into the host cell cytosol. We propose that the wild-type strain, through the action of SPI-2 effectors (including SpiC), diverts the Salmonella-containing vacuole from the endocytic pathway, and subsequent recruitment and maintenance of vacuolar ATPase/lgp-containing membranes that enclose replicating bacteria is mediated by translocation of SifA.
authors.affiliation: Department of Infectious Diseases, Imperial College School of Medicine, Du Cane Road, London W12 0NN, Electron Microscopy Unit, Queen Charlotte's and Chelsea Hospital, Goldhawk Road, London W6 0XG, UK and Centre d'Immunologie INSERM-CNRS de Ma.
authors.forename: C R
authors.initials: CR
authors.lastname: Beuzón
authors.forename: S
authors.initials: S
authors.lastname: Méresse
authors.forename: K E
authors.initials: KE
authors.lastname: Unsworth
authors.forename: J
authors.initials: J
authors.lastname: Ruíz-Albert
authors.forename: S
authors.initials: S
authors.lastname: Garvis
authors.forename: S R
authors.initials: SR
authors.lastname: Waterman
authors.forename: T A
authors.initials: TA
authors.lastname: Ryder
authors.forename: E
authors.initials: E
authors.lastname: Boucrot
authors.forename: D W
authors.initials: DW
authors.lastname: Holden
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D005798:Genes, Bacterial; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012481:Salmonella Infections, Animal / Q000382:microbiology; D012486:Salmonella typhimurium / Q000235:genetics / Q000472:pathogenicity* / Q000648:ultrastructure; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000648:ultrastructure*; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D011993:Recombinant Fusion Proteins