Abstract
SummaryThe transcriptional activator PrfA, a member of the Crp/Fnr family, controls the expression of some key virulence factors necessary for infection by the human bacterial pathogen Listeria monocytogenes. Phenotypic screening identified ring-fused 2-pyridone molecules that at low micromolar concentrations attenuate L. monocytogenes cellular uptake by reducing the expression of virulence genes. These inhibitors bind the transcriptional regulator PrfA and decrease its affinity for the consensus DNA-binding site. Structural characterization of this interaction revealed that one of the ring-fused 2-pyridones, compound 1, binds at two separate sites on the protein: one within a hydrophobic pocket or tunnel, located between the C- and N-terminal domains of PrfA, and the second in the vicinity of the DNA-binding helix-turn-helix motif. At both sites the compound interacts with residues important for PrfA activation and helix-turn-helix formation. Ring-fused 2-pyridones represent a new class of chemical probes for studying virulence in L. monocytogenes.
Highlights
In light of increasing antibiotic resistance, novel therapies are required to potentiate or succeed our current selection of therapeutic options (Davies and Davies, 2010)
These inhibitors bind the transcriptional regulator PrfA and decrease its affinity for the consensus DNA-binding site. Structural characterization of this interaction revealed that one of the ring-fused 2-pyridones, compound 1, binds at two separate sites on the protein: one within a hydrophobic pocket or tunnel, located between the C- and N-terminal domains of PrfA, and the second in the vicinity of the DNA-binding helix-turn-helix motif. At both sites the compound interacts with residues important for PrfA activation and helix-turn-helix formation
When we performed a time-course experiment monitoring the infection dynamics more closely, we observed an inability of L. monocytogenes to replicate within Caco-2 cells after treatment with compound 2, which displayed the largest efficiency in the uptake experiment (Figure 1B, left panel)
Summary
In light of increasing antibiotic resistance, novel therapies are required to potentiate or succeed our current selection of therapeutic options (Davies and Davies, 2010). An alternative to classical antibiotics are drugs inhibiting the virulence of pathogenic bacteria. The first step in establishing this as a viable and effective therapeutic strategy is to understand how the virulence of pathogenic bacteria can be controlled (Allen et al, 2014; Clatworthy et al, 2007; Rasko and Sperandio, 2010). Pregnant, immunocompromised, and other at-risk patients are vulnerable to invasive listeriosis, and the high mortality rates within these subpopulations ($20%–40%) are a stark demonstration of the clinical difficulty in dealing with these infections (Drevets and Bronze, 2008; Hamon et al, 2006; Jackson et al, 2010; Vazquez-Boland et al, 2001)
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