Fine‐Tuning Covalent Inhibition of Bacterial Quorum Sensing

Abstract

Emerging antibiotic resistance among human pathogens has galvanized efforts to find alternative routes to combat bacterial virulence. One new approach entails interfering with the ability of bacteria to coordinate population-wide gene expression, or quorum sensing (QS), thus inhibiting the production of virulence factors and biofilm formation. We have recently developed such a strategy by targeting LasR, the master regulator of QS in the opportunistic human pathogen Pseudomonas aeruginosa, through the rational design of covalent inhibitors closely based on the core structure of the native ligand. We now report several groups of new inhibitors, one of which, fluoro-substituted ITC-12, displayed complete covalent modification of LasR, as well as effective QS inhibition in vitro and promising in vivo results. In addition to their potential clinical relevance, this series of synthetic QS modulators can be used as a tool to further unravel the complicated QS regulation in P. aeruginosa.

Inhibitors of Bacterial Swarming Behavior

“…aeruginosa. [40] These compounds and especially a b-fluorinated derivative ICT-F (6)c ovalently blocked the LasR receptor at Cys79 and inhibited swarming motilityb y4 4% at 150 mm and by 34 %a t2 0mm and also reducedp yocyanin production( Figure 3a). In contrast, the bro-minatedI TC-Br (7)d id not bind covalently and was aL asR agonist that increased swarming motilityu pt o2 .5-fold at 20 mm of ITC-Br in P. aeruginosa PA14.…”

“…The production of the swarming surfactant rhamnolipid which Pseudomonas requires to lower surface tension is RhlR regulated by transcription of the rhl genes. The Meijler group developed synthetic AHLs with an isothiocyanate (ITC) warhead mimicking 3‐oxo‐C12‐HSL of P. aeruginosa . These compounds and especially a β‐fluorinated derivative ICT‐F ( 6 ) covalently blocked the LasR receptor at Cys79 and inhibited swarming motility by 44 % at 150 μ m and by 34 % at 20 μ m and also reduced pyocyanin production (Figure a).…”

“…In contrast, the bro-minatedI TC-Br (7)d id not bind covalently and was aL asR agonist that increased swarming motilityu pt o2 .5-fold at 20 mm of ITC-Br in P. aeruginosa PA14. [40] High-throughput screening of ac ompound library against reporter strains revealed the plant-produced flavonoids phloretin, chrysin, and naringenin as potent inhibitors of the LasR and RhlR quorum-sensing receptors of P. aeruginosa. [41] Additionally,a lso flavonoids like quercetin (8), baicalein, and pinocembrin exhibited inhibitory activity whereby the presence of as pecific pattern of two hydroxyl-groups on the flavonoid Aring appeared to be required for activity ( Figure 2).…”

Covalent inhibitors: an opportunity for rational target selectivity

“…[30] A subsequent study by the same group reported several series of new inhibitors, one of which, fluoro-substituted ITC-12, displayed complete covalent modification of LasR, as well as promising in vivo results. [31] Covalent inhibitor of MEP: The methylerythritol phosphate (MEP) pathway is an essential metabolic pathway found in protozoa, including malaria parasites, and bacteria but absent in higher eukaryotes, making it a highly attractive target for the discovery of novel anti-infective agents. Notably, IspD, the third catalytic enzyme of the MEP pathway of different malaria parasites, has a cysteine in the vicinity of the catalytic site.…”

The State of the Union Is Strong: a Review of ASM's 6th Conference on Cell-Cell Communication in Bacteria

“…The Meijler group studies QS in bacterial pathogens using a range of elegant chemical approaches. Michael Meijler first outlined the origins of his novel electrophilic probes that are designed to bind LuxR-type QS receptors covalently, leading to inhibition of QS-regulated gene expression (26,27). His lab has applied these probes, along with newer photoactivatable probes, as molecular tools to obtain new insights into the mechanisms of QS.…”