The metabolic regulator CodY links Listeria monocytogenes metabolism to virulence by directly activating the virulence regulatory gene prfA

Abstract

Summary Metabolic adaptations are critical to the ability of bacterial pathogens to grow within host cells and are normally preceded by sensing of host-specific metabolic signals, which in turn can influence the pathogen's virulence state. Previously, we reported that the intracellular bacterial pathogen Listeria monocytogenes responds to low availability of branched-chain amino acids (BCAA) within mammalian cells by up-regulating both BCAA biosynthesis and virulence genes. The induction of virulence genes required the BCAA-responsive transcription regulator, CodY, but the molecular mechanism governing this mode of regulation was unclear. In this report, we demonstrate that CodY directly binds the coding sequence of the L. monocytogenes master virulence activator gene, prfA, 15 nt downstream of its start codon, and that this binding results in up-regulation of prfA transcription specifically under low concentrations of BCAA. Mutating this site abolished CodY binding and reduced prfA transcription in macrophages, and attenuated bacterial virulence in mice. Notably, the mutated binding site did not alter prfA transcription or PrfA activity under other conditions that are known to activate PrfA, such as during growth in the presence of glucose-1-phosphate. This study highlights the tight crosstalk between L. monocytogenes metabolism and virulence' while revealing novel features of CodY-mediated regulation.

The PAMP c-di-AMP Is Essential for Listeria monocytogenes Growth in Rich but Not Minimal Media due to a Toxic Increase in (p)ppGpp

“…The codY::spc mutation suppressed the virulence defect of the ΔrelAPQ strain to the level of a codY::spc mutation alone, approximately 10-fold less virulent than wild-type (Figure 5B). The virulence defect of the codY::spc mutant is consistent with previous reports demonstrating a virulence defect for a codY mutant (Lobel et al, 2014; 2012), and mutations in codY suppress the virulence defect of other pathogenic Firmicutes with decreased (p)ppGpp (Geiger and Wolz, 2014). Our data suggested that the principle role of (p)ppGpp during infection was the inhibition of GTP synthesis leading to inactivation of CodY.…”

Bacterial Stress Responses during Host Infection

“…The stringent response is also regulated by the RNA polymerase-binding protein DksA, which regulates amino acid biosynthetic genes as well as antioxidant and antinitrosative defenses essential for Salmonella pathogenesis (Henard and Vazquez-Torres, 2012; Henard et al, 2014). In Gram-positive bacteria, CodY is involved in regulating virulence gene expression in response to amino acid availability (Geiger et al, 2010; Lobel et al, 2015). In Listeria , CodY induces expression of the virulence regulator PrfA when concentrations of branched-chain amino acids are low, while its role in S. aureus virulence gene regulation is more complex.…”

Branching Out: Alterations in Bacterial Physiology and Virulence Due to Branched-Chain Amino Acid Deprivation

“…Consequently, an L. monocytogenes codY mutant is impaired in motility and intracellular replication (35, 39). The role of CodY during L.…”