title: Inactivation of a two-component signal transduction system, SaeRS, eliminates adherence and attenuates virulence of Staphylococcus aureus.
abstract: Staphylococcus aureus is a major human and animal pathogen. During infection, this organism not only is able to attach to and enter host cells by using its cell surface-associated factors but also exports toxins to induce apoptosis and kill invaded cells. In this study, we identified the regulon of a two-component signal transduction system, SaeRS, and demonstrated that the SaeRS system is required for S. aureus to cause infection both in vitro and in vivo. Using microarray and real-time reverse transcriptase PCR analyses, we found that SaeRS regulates the expression of genes involved in adhesion and invasion (such as those encoding fibronectin-binding proteins and fibrinogen-binding proteins) and genes encoding alpha-, beta-, and gamma-hemolysins. Surprisingly, we found that SaeRS represses the Agr regulatory system since the mutation of saeS up-regulates agrA expression, which was confirmed by using an agr promoter-reporter fusion system. More importantly, we demonstrated that inactivation of the SaeRS system significantly decreases the bacterium-induced apoptosis and/or death of lung epithelial cells (A549) and attenuates virulence in a murine infection model. Moreover, we found that inactivation of the SaeRS system eliminates staphylococcal adhesion and internalization of lung epithelial cells. We also found that both a novel hypothetical protein (the SA1000 protein) and a bifunctional protein (Efb), which binds to extracellular fibrinogen and complement factor C3, might partially contribute to bacterial adhesion to and invasion of epithelial cells. Our results indicate that activation of the SaeRS system may be required for S. aureus to adhere to and invade epithelial cells.
authors.affiliation: Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Ave., St. Paul, Minnesota 55108, USA.
authors.forename: Xudong
authors.initials: X
authors.lastname: Liang
authors.forename: Chuanxin
authors.initials: C
authors.lastname: Yu
authors.forename: Junsong
authors.initials: J
authors.lastname: Sun
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Christina
authors.initials: C
authors.lastname: Landwehr
authors.forename: David
authors.initials: D
authors.lastname: Holmes
authors.forename: Yinduo
authors.initials: Y
authors.lastname: Ji
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004847:Epithelial Cells / Q000382:microbiology; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008168:Lung / Q000166:cytology; D051379:Mice; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D011704:Pyelonephritis / Q000382:microbiology; D015398:Signal Transduction; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity* / Q000502:physiology; D014157:Transcription Factors; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; C433805:SaeR protein, Staphylococcus aureus; D014157:Transcription Factors