Differential regulation of staphylococcal virulence by the sensor kinase SaeS in response to neutrophil-derived stimuli.
Two-component systems (TCSs) are highly conserved across bacteria and are used to rapidly sense and respond to changing environmental conditions. The human pathogen Staphylococcus aureus uses the S. aureus exoprotein expression (sae) TCS to sense host signals and activate transcription of virulence factors essential to pathogenesis. Despite its importance, the mechanism by which the histidine kinase SaeS recognizes specific host stimuli is unknown. After mutagenizing the predicted extracellular loop of SaeS, we discovered one methionine residue (M31) was essential for the ability of S. aureus to transcribe sae target genes, including hla, lukAB/lukGH, and hlgA. This single M31A mutation also significantly reduced cytotoxicity in human neutrophils to levels observed in cells following interaction with ΔsaeS. Another important discovery was that mutation of two aromatic anchor residues (W32A and F33A) disrupted the normal basal signaling of SaeS in the absence of inducing signals, yet both mutant kinases had appropriate activation of effector genes following exposure to neutrophils. Although the transcriptional profile of aromatic mutation W32A was consistent with that of WT in response to human α-defensin 1, mutant kinase F33A did not properly transcribe the γ-toxin genes in response to this stimulus. Taken together, our results provide molecular evidence for how SaeS recognizes host signals and triggers activation of select virulence factors to facilitate evasion of innate immunity. These findings have important implications for signal transduction in prokaryotes and eukaryotes due to conservation of aromatic anchor residues across both of these domains and the important role they play in sensor protein structure and function.
Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242; and.
Caralyn E
CE
Flack
Department of Immunology and Infectious Diseases, Montana State University, Bozeman, MT 59715.
Oliwia W
OW
Zurek
Department of Immunology and Infectious Diseases, Montana State University, Bozeman, MT 59715.
Delisha D
DD
Meishery
Department of Immunology and Infectious Diseases, Montana State University, Bozeman, MT 59715.
Kyler B
KB
Pallister
Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242; and.
Cheryl L
CL
Malone
Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242; and.
Alexander R
AR
Horswill
Department of Immunology and Infectious Diseases, Montana State University, Bozeman, MT 59715 jovanka@montana.edu.
Jovanka M
JM
Voyich
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002462:Cell Membrane / Q000378:metabolism; D004789:Enzyme Activation; D007113:Immunity, Innate / Q000276:immunology; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000276:immunology / Q000382:microbiology*; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000276:immunology; D013211:Staphylococcus aureus / Q000201:enzymology* / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence
D001426:Bacterial Proteins; D011494:Protein Kinases; C527351:SaeS protein, Staphylococcus aureus
host-pathogen interactions; membrane proteins