Potent modulation of the CepR quorum sensing receptor and virulence in a Burkholderia cepacia complex member using non-native lactone ligands

Abstract

The Burkholderia cepacia complex (Bcc) is a family of closely related bacterial pathogens that are the causative agent of deadly human infections. Virulence in Bcc species has been shown to be controlled by the CepI/CepR quorum sensing (QS) system, which is mediated by an N-acyl L-homoserine lactone (AHL) signal (C8-AHL) and its cognate LuxR-type receptor (CepR). Chemical strategies to block QS in Bcc members would represent an approach to intercept this bacterial communication process and further delineate its role in infection. In the current study, we sought to identify non-native AHLs capable of agonizing or antagonizing CepR, and thereby QS, in a Bcc member. We screened a library of AHL analogs in cell-based reporters for CepR, and identified numerous highly potent CepR agonists and antagonists. These compounds remain active in a Bcc member, B. multivorans, with one agonist 250-fold more potent than the native ligand C8-AHL, and can affect QS-controlled motility. Further, the CepR antagonists prolong C. elegans survival in an infection model. These AHL analogs are the first reported non-native molecules that both directly modulate CepR and impact QS-controlled phenotypes in a Bcc member, and represent valuable chemical tools to assess the role of QS in Bcc infections.

Chemical Control of Quorum Sensing in E. coli: Identification of Small Molecule Modulators of SdiA and Mechanistic Characterization of a Covalent Inhibitor

“…We compiled a focused library of 153 AHLs and related analogs (full structures in Figure S1) to screen in a cell-based reporter of SdiA EC activity. For this primary screen, we selected a series of sublibraries from our in-house collection of AHL derivatives and other small molecules with demonstrated activities in other LuxR-type receptors. ,,− These compounds fall into seven categories: naturally occurring AHLs with aliphatic tails (Figure i), N -benzoyl HLs (BnHLs, Figure ii), N -phenylacetanoyl HLs (PHLs, Figure iii), N -phenylpropionyl HLs (PPHLs, Figure iv), other AHLs (Figure v), N -acyl homocysteine thiolactones (AHTs, Figure vi), and other non-AHLs (Figure vii). This focused library was a good starting point to explore the SARs for AHL/SdiA EC interactions as it contains a broad sampling of changes to the aliphatic tail, amide linker, and lactone headgroup of the natural AHL structure.…”

Autoinducer-Fluorophore Conjugates Enable FRET in LuxR Proteins in Vitro and in Cells

“…2B) and competitive antagonism (against the native AHL; Fig. S6) in E. coli b-galactosidase reporter strains for the following seven LuxRtype receptors: LasR, 6 RhlR, 28 and QscR 27 from P. aeruginosa; CviR from Chromobacterium violaceum; CepR from Burkholderia cenocepacia; 29 SdiA from E. coli (referred to as SdiAEC); 12 and SdiA from Salmonella enterica (referred to as SdiASE). 30 Efficacious agonists were identified in almost every receptor (Fig.…”

Methodological tools to study species of the genus Burkholderia

“…Burkholderia species exploit the cell density-dependent quorum sensing (QS) signaling to synchronize the bacterial population gene expression in response to microenvironment stimuli. As nearly all known Gram-negative bacteria, they mainly possess LuxI/LuxR-like QS systems relying on acyl-homoserine lactone (AHL) autoinducers (Slinger et al 2019 ). However, other kind of QS signals are also used by Burkholderia spp.…”

“…For this reason, Klaus et al used an E. coli reporter to elucidate the role of B. pseudomallei AHLs molecules in the activation of the transcription factor MalR (Klaus et al 2018 ). Instead, Slinger et al exploited this strategy to screen a library of AHL analogs and find modulators of the B. cenocepacia CepR in an E. coli reporter defective for its LuxR-type regulator (Slinger et al 2019 ).…”