title: Biphasic intracellular expression of Staphylococcus aureus virulence factors and evidence for Agr-mediated diffusion sensing.
abstract: Staphylococcus aureus invades a variety of mammalian cells and escapes from the endosome to multiply in the cytoplasm. We had previously hypothesized that the molecular events leading to escape of S. aureus from the endosome involved the Agr virulence factor regulatory system. In this report we demonstrate that temporal changes in intracellular activation of the Agr regulon correlates with expression of membrane active toxins. Also, the initial expression of Agr by even small numbers of staphylococci resulted in the permeabilization of the endosomal membrane and the eventual escape of bacteria into the cytoplasm by 3 h post invasion. After Agr downregulation, a second peak of expression coincided with increased permeability of the host cell membrane. In contrast to the parental strain, an Agr-mutant was unable to escape into the cytoplasm and was observed in intact endosomes as late as 5 h post invasion. These data provide evidence that staphylococcal virulence factor production during invasion of host cells is mediated by an Agr-dependent process that is most accurately described in the context of diffusion sensing.
authors.affiliation: Department of Microbiology, Molecular Biology and Biochemistry, Ag-Biotech Bldg. Laboratory 222, University of Idaho, Moscow, Idaho 83844 USA.
authors.forename: Sankale
authors.initials: S
authors.lastname: Shompole
authors.forename: Kim T
authors.initials: KT
authors.lastname: Henon
authors.forename: Linda E
authors.initials: LE
authors.lastname: Liou
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Dziewanowska
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Bohach
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Bayles
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D016372:RNA, Antisense / Q000378:metabolism; D012329:RNA, Bacterial / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C095698:Agr protein, Staphylococcus aureus; D001426:Bacterial Proteins; D016372:RNA, Antisense; D012329:RNA, Bacterial; C096035:RNAIII, Staphylococcus aureus; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D037521:Virulence Factors