The agr locus encodes the central regulatory system for staphylococcal pathogenesis and other stress-related functions. It is a quorum-sensing system that contains a two-component signal transduction module, encoded by agrA and C, and a peptide autoinducer (AIP), encoded by agrD, that is the activating ligand. Natural variants exist that cross inhibit agr autoinduction in heterologous combinations, thus blocking pathogenesis. This is the continuation of a long-term program whose overall goal is to understand the mechanism of agr autoinduction, the role of the agr autoinduction circuit in the pathogenesis of staphylococcal disease, the therapeutic potential of agr inhibition, and the biological significance of agr variants and their biotypes.
Specific Aims for this period are: 1. To determine mechanisms of peptide secretion, binding, activation and inhibition. 2. To determine the mechanism of signal transduction in the agr system. 3. To determine the therapeutic potential of agr inhibition. Design and Methods. Genetic and biochemical methods will be used to determine the mechanism of AIP secretion. A direct ligand-binding assay will be used to analyze receptor-ligand interactions. Specific ligand binding sites will be identified by mutagenesis and cross-linking studies;the mechanism of receptor activation will be determined by mutational and structural studies. Constitutively active receptor mutants will be an important tool in vitro mechanistic studies. Mutants resistant to inverse agonism will be isolated and analyzed to test the hypothesis that there are specific inhibitory contacts as well as activating contacts. The hypothesis will be tested that administration of an inhibitory AIP at a distal site can block the establishment of an experimental infection, or if administered after an infection has been established, can attenuate or eradicate the infection.
Staphylococcus aureus, long a scourge of the hospital, has invaded the outside community with enhanced virulence and high contagion. Our project is aimed at understanding the pathobiology of the organism and learning how to block its ability to cause disease by interfering with the function of a key bacterial signaling system that activates the production of toxins and other detrimental substances.
|Wang, Boyuan; Muir, Tom W (2016) Regulation of Virulence in Staphylococcus aureus: Molecular Mechanisms and Remaining Puzzles. Cell Chem Biol 23:214-24|
|Johnson, Jeffrey G; Wang, Boyuan; Debelouchina, Galia T et al. (2015) Increasing AIP Macrocycle Size Reveals Key Features of agr Activation in Staphylococcus aureus. Chembiochem 16:1093-100|
|Wang, Boyuan; Zhao, Aishan; Novick, Richard P et al. (2015) Key driving forces in the biosynthesis of autoinducing peptides required for staphylococcal virulence. Proc Natl Acad Sci U S A 112:10679-84|
|Wang, Boyuan; Zhao, Aishan; Novick, Richard P et al. (2014) Activation and inhibition of the receptor histidine kinase AgrC occurs through opposite helical transduction motions. Mol Cell 53:929-40|
|Ubeda, Carles; Tormo-Mas, Maria Angeles; Penades, Jose R et al. (2012) Structure-function analysis of the SaPIbov1 replication origin in Staphylococcus aureus. Plasmid 67:183-90|
|George Cisar, Elizabeth A; Geisinger, Edward; Muir, Tom W et al. (2009) Symmetric signalling within asymmetric dimers of the Staphylococcus aureus receptor histidine kinase AgrC. Mol Microbiol 74:44-57|
|Geisinger, Edward; Muir, Tom W; Novick, Richard P (2009) agr receptor mutants reveal distinct modes of inhibition by staphylococcal autoinducing peptides. Proc Natl Acad Sci U S A 106:1216-21|
|Geisinger, Edward; George, Elizabeth A; Muir, Tom W et al. (2008) Identification of ligand specificity determinants in AgrC, the Staphylococcus aureus quorum-sensing receptor. J Biol Chem 283:8930-8|
|George, Elizabeth A; Novick, Richard P; Muir, Tom W (2008) Cyclic peptide inhibitors of staphylococcal virulence prepared by Fmoc-based thiolactone peptide synthesis. J Am Chem Soc 130:4914-24|
|George, Elizabeth A; Muir, Tom W (2007) Molecular mechanisms of agr quorum sensing in virulent staphylococci. Chembiochem 8:847-55|
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