Bacterial Nitric Oxide Synthase Is Required for the Staphylococcus aureus Response to Heme Stress.
Staphylococcus aureus is a pathogen that causes significant morbidity and mortality worldwide. Within the vertebrate host, S. aureus requires heme as a nutrient iron source and as a cofactor for multiple cellular processes. Although required for pathogenesis, excess heme is toxic. S. aureus employs a two-component system, the heme sensor system (HssRS), to sense and protect against heme toxicity. Upon activation, HssRS induces the expression of the heme-regulated transporter (HrtAB), an efflux pump that alleviates heme toxicity. The ability to sense and respond to heme is critical for the pathogenesis of numerous Gram-positive organisms, yet the mechanism of heme sensing remains unknown. Compound '3981 was identified in a high-throughput screen as an activator of staphylococcal HssRS that triggers HssRS independently of heme accumulation. '3981 is toxic to S. aureus; however, derivatives of '3981 were synthesized that lack toxicity while retaining HssRS activation, enabling the interrogation of the heme stress response without confounding toxic effects of the parent molecule. Using '3981 derivatives as probes of the heme stress response, numerous genes required for '3981-induced activation of HssRS were uncovered. Specifically, multiple genes involved in the production of nitric oxide were identified, including the gene encoding bacterial nitric oxide synthase (bNOS). bNOS protects S. aureus from oxidative stress imposed by heme. Taken together, this work identifies bNOS as crucial for the S. aureus heme stress response, providing evidence that nitric oxide synthesis and heme sensing are intertwined.
Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center , Nashville, Tennessee 37232, United States.
Matthew C
MC
Surdel
Department of Chemistry, Vanderbilt Institute for Chemical Biology, Vanderbilt University , Nashville, Tennessee 37232, United States.
Brendan F
BF
Dutter
Department of Chemistry, Vanderbilt Institute for Chemical Biology, Vanderbilt University , Nashville, Tennessee 37232, United States.
Gary A
GA
Sulikowski
Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center , Nashville, Tennessee 37232, United States.|Tennessee Valley Healthcare Systems, U.S. Department of Veterans Affairs, Nashville, Tennessee 37212, United States.
Eric P
EP
Skaar
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D015964:Gene Expression Regulation, Bacterial; D006418:Heme / Q000378:metabolism*; D006801:Humans; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D009569:Nitric Oxide; D006418:Heme; D019001:Nitric Oxide Synthase
Staphylococcus aureus; heme stress response; nitric oxide synthase; small-molecule optimization