Control of Staphylococcus aureus quorum sensing by a membrane-embedded peptidase

Abstract

26Gram-positive bacteria process and release small peptides or "pheromones" that act as signals 27 for the induction of adaptive traits including those involved in pathogenesis. One class of small 28 signaling pheromones is the cyclic auto-inducing peptides (AIPs), which regulate expression of 29 genes that orchestrate virulence and persistence in a range of microbes including 30Staphylococci, Listeria, Clostridia, and Enterococci. In a genetic screen for Staphylococcus 31 aureus secreted virulence factors, we identified a S. aureus mutant containing an insertion in 32 gene SAUSA300_1984 (mroQ), which encodes a putative membrane-embedded 33 metalloprotease. A ΔmroQ mutant exhibits impaired induction of TLR2-dependent 34 inflammatory responses from macrophages, but elicits greater production of the inflammatory 35 cytokine IL-1β and is attenuated in a murine skin and soft tissue infection model. The ΔmroQ 36 mutant phenocopies a S. aureus mutant containing a deletion of the accessory gene regulatory 37 system (Agr), wherein both strains have significantly reduced production of secreted toxins and 38 virulence factors, but increased surface Protein A abundance. The Agr system controls 39 virulence factor gene expression in S. aureus through sensing accumulation of AIP via the 40 histidine kinase AgrC and response regulator AgrA. We provide evidence to suggest that MroQ 41 acts within the Agr pathway to facilitate optimal processing or export of AIP for signal 42 amplification through AgrC/A and induction of virulence factor gene expression. Mutation of 43MroQ active site residues significantly reduces AIP signaling and attenuates virulence. 44Altogether, this work identifies a new component of the Agr quorum sensing circuit that is 45 critical for the production of S. aureus virulence factors. 46 47 48 from the bacterial cell. While many signaling molecules of Gram-negative bacteria are freely 56 diffusible, the peptides of Gram-positives generally must transit the membrane via a dedicated 57 transporter (4, 5). After processing and transport, the peptide is either imported back into the 58 bacterial cell or transmits signal from the extracellular environment by binding to membrane-59 embedded sensor histidine kinases (6). Peptide signaling culminates in a change in gene 60 expression mediated by transcription factors that respond to the peptide. Many Gram-positive 61 bacterial pathogens use these "quorum-sensing" peptides to induce gene expression programs 62 that promote virulence adaptations such as competence, toxin production, biofilm formation, 63 and establishment of persistence traits. Because of its importance in activating virulence 64 programs in S. aureus, quorum-sensing inhibition has been the focus of many therapeutic 65 initiatives (7)(8)(9)(10)(11)(12)(13)(14). 66The ability of S. aureus to infect host tissues and cause acute and chronic disease is 67 partially due to its use of complex gene regulatory systems that control virulence factor gene 68 expression (15-17). S. aureus employs 16 two-compone...

Transposon Screen of Surface Accessibility inS. aureus

“…Relatedly, the protein product of SAUSA300_1984 ( mroQ ) acts within the Agr pathway. 43 Moreover, the protein product of SAUSA300_1467 ( lpdA ) has been shown to have a role in branched-chain fatty acid biosynthesis. 44 The selected transposants were also tested for labeling with a second fluorescent probe ( DBCO-AF488 ) in order to determine the role of the fluorophore in PG labeling ( Figure S4 ).…”

Comparative Study of the Difference in Behavior of the Accessory Gene Regulator (Agr) in USA300 and USA400 Community-Associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA)

“…Agr is a quorum-sensing operon that is also an important regulatory factor that controls virulence factors, including toxin production, mecA expression, and biofilm formation of MRSA [10,22,24,[51][52][53]. Thus, it is extensively studied as a target for controlling MRSA [52][53][54]. However, recent studies suggested a more complex role of Agr and it showed quite strain dependent manner.…”

cydA, spdC, and mroQ are novel genes involved in the plasma coagulation of Staphylococcus aureus

“…The possible mechanism involves hydrolysis of auto‐inducing peptide by mroQ coding synthase, resulting in the inactivation of agrC . This subsequently inactivated the function of downstream RNAII and RNAIII, and the regulated genes, including coagulase, showed no expression 23,24 …”