title: Site-specific mutation of the sensor kinase GraS in Staphylococcus aureus alters the adaptive response to distinct cationic antimicrobial peptides.
abstract: The Staphylococcus aureus two-component regulatory system, GraRS, is involved in resistance to killing by distinct host defense cationic antimicrobial peptides (HD-CAPs). It is believed to regulate downstream target genes such as mprF and dltABCD to modify the S. aureus surface charge. However, the detailed mechanism(s) by which the histidine kinase, GraS, senses specific HD-CAPs is not well defined. Here, we studied a well-characterized clinical methicillin-resistant S. aureus (MRSA) strain (MW2), its isogenic graS deletion mutant (ΔgraS strain), a nonameric extracellular loop mutant (ΔEL strain), and four residue-specific ΔEL mutants (D37A, P39A, P39S, and D35G D37G D41G strains). The ΔgraS and ΔEL strains were unable to induce mprF and dltA expression and, in turn, demonstrated significantly increased susceptibilities to daptomycin, polymyxin B, and two prototypical HD-CAPs (hNP-1 and RP-1). Further, P39A, P39S, and D35G-D37G-D41G ΔEL mutations correlated with moderate increases in HD-CAP susceptibility. Reductions of mprF and dltA induction by PMB were also found in the ΔEL mutants, suggesting these residues are pivotal to appropriate activation of the GraS sensor kinase. Importantly, a synthetic exogenous soluble EL mimic of GraS protected the parental MW2 strain against hNP-1- and RP-1-mediated killing, suggesting a direct interaction of the EL with HD-CAPs in GraS activation. In vivo, the ΔgraS and ΔEL strains displayed dramatic reductions in achieved target tissue MRSA counts in an endocarditis model. Taken together, our results provide new insights into potential roles of GraS in S. aureus sensing of HD-CAPs to induce adaptive survival responses to these molecules.
authors.affiliation: Department of Microbiology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Ambrose L
authors.initials: AL
authors.lastname: Cheung
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA The David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Arnold S
authors.initials: AS
authors.lastname: Bayer
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA The David Geffen School of Medicine at UCLA, Los Angeles, California, USA Division of Molecular Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Yeaman
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA The David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Yan Q
authors.initials: YQ
authors.lastname: Xiong
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA The David Geffen School of Medicine at UCLA, Los Angeles, California, USA Division of Molecular Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Waring
authors.affiliation: Department of Microbiology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Guido
authors.initials: G
authors.lastname: Memmi
authors.affiliation: Department of Microbiology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Niles
authors.initials: N
authors.lastname: Donegan
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA.
authors.forename: Siyang
authors.initials: S
authors.lastname: Chaili
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA The David Geffen School of Medicine at UCLA, Los Angeles, California, USA sjyang@ucla.edu.
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Yang
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D004696:Endocarditis / Q000382:microbiology / Q000473:pathology; D005260:Female; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D017384:Sequence Deletion; D013312:Stress, Physiological
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D001426:Bacterial Proteins; D050505:Mutant Proteins; D011494:Protein Kinases