Chemical genetics unveils WTA/PBP2a-PBP2/VraRS as a regulatory axis for virulence gene expression in CA-MRSA

Abstract Phenol-soluble modulins (PSMs) and Staphylococcal protein A (SpA) are key virulence determinants for community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). Here, using chemical and genetic approaches, we show that inhibition of TarO, the first enzyme in the wall teichoic acid (WTA) biosynthetic pathway, decreases the expression of genes encoding PSMs and SpA in the prototypical CA-MRSA strain USA300 LAC. Mechanistically, these effects are linked to the activation of VraRS two-component system that directly represses the expression of accessory gene regulator (agr) locus and spa. The activation of VraRS was due, at least in part, to the loss of the functional integrity of penicillin-binding protein 2 (PBP2) in a PBP2a-dependent manner. We provide multiple lines of evidence that the accumulation of lipid-linked peptidoglycan precursors is a trigger for the activation of VraRS. In sum, our data reveal an unprecedented and important role for WTA biosynthesis in the regulation of virulence gene expression in CA-MRSA, underlining that acquisition of PBP2a-encoding mecA gene can impart an additional regulatory layer for the modulation of key signaling pathways (e.g., VraRS and agr) in S. aureus.