Dataset Information

RpoN Regulates Virulence Factors of Pseudomonas aeruginosa via Modulating the PqsR Quorum Sensing Regulator.

ABSTRACT: The alternative sigma factor RpoN regulates many cell functions, such as motility, quorum sensing, and virulence in the opportunistic pathogen Pseudomonas aeruginosa (P. aeruginosa). P. aeruginosa often evolves rpoN-negative variants during the chronic infection in cystic fibrosis patients. It is unclear how RpoN interacts with other regulatory mechanisms to control virulence of P. aeruginosa. In this study, we show that RpoN modulates the function of PqsR, a quorum sensing receptor regulating production of virulence factors including the phenazine pyocyanin. The ?rpoN mutant is able to synthesize 4-quinolone signal molecule HHQ but unable to activate PqsR and Pseudomonas quinolone signal (pqs) quorum sensing. The ?rpoN mutant produces minimal level of pyocyanin and is unable to produce the anti-staphylococcal agents. Providing pqsR in trans in the ?rpoN mutant restores its pqs quorum sensing and virulence factor production to the wild-type level. Our study provides evidence that RpoN has a regulatory effect on P. aeruginosa virulence through modulating the function of the PqsR quorum sensing regulator.

SUBMITTER: Cai Z

PROVIDER: S-EPMC4691050 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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RpoN Regulates Virulence Factors of Pseudomonas aeruginosa via Modulating the PqsR Quorum Sensing Regulator.

Cai Zhao Z Liu Yang Y Chen Yicai Y Yam Joey Kuok Hoong JK Chew Su Chuen SC Chua Song Lin SL Wang Ke K Givskov Michael M Yang Liang L

International journal of molecular sciences 20151130 12

The alternative sigma factor RpoN regulates many cell functions, such as motility, quorum sensing, and virulence in the opportunistic pathogen Pseudomonas aeruginosa (P. aeruginosa). P. aeruginosa often evolves rpoN-negative variants during the chronic infection in cystic fibrosis patients. It is unclear how RpoN interacts with other regulatory mechanisms to control virulence of P. aeruginosa. In this study, we show that RpoN modulates the function of PqsR, a quorum sensing receptor regulating p ...[more]

PMID: 26633362

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Project description:Bacterial populations co-ordinate gene expression collectively through quorum sensing (QS), a cell-to-cell communication mechanism employing diffusible signal molecules. The LysR-type transcriptional regulator (LTTR) protein PqsR (MvfR) is a key component of alkyl-quinolone (AQ)-dependent QS in Pseudomonas aeruginosa. PqsR is activated by 2-alkyl-4-quinolones including the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone), its precursor 2-heptyl-4-hydroxyquinoline (HHQ) and their C9 congeners, 2-nonyl-3-hydroxy-4(1H)-quinolone (C9-PQS) and 2-nonyl-4-hydroxyquinoline (NHQ). These drive the autoinduction of AQ biosynthesis and the up-regulation of key virulence determinants as a function of bacterial population density. Consequently, PqsR constitutes a potential target for novel antibacterial agents which attenuate infection through the blockade of virulence. Here we present the crystal structures of the PqsR co-inducer binding domain (CBD) and a complex with the native agonist NHQ. We show that the structure of the PqsR CBD has an unusually large ligand-binding pocket in which a native AQ agonist is stabilized entirely by hydrophobic interactions. Through a ligand-based design strategy we synthesized and evaluated a series of 50 AQ and novel quinazolinone (QZN) analogues and measured the impact on AQ biosynthesis, virulence gene expression and biofilm development. The simple exchange of two isosteres (OH for NH?) switches a QZN agonist to an antagonist with a concomitant impact on the induction of bacterial virulence factor production. We also determined the complex crystal structure of a QZN antagonist bound to PqsR revealing a similar orientation in the ligand binding pocket to the native agonist NHQ. This structure represents the first description of an LTTR-antagonist complex. Overall these studies present novel insights into LTTR ligand binding and ligand-based drug design and provide a chemical scaffold for further anti-P. aeruginosa virulence drug development by targeting the AQ receptor PqsR.

Project description:With the rising development of bacterial resistance the search for new medical treatments beyond conventional antimicrobials has become a key aim of public health research. Possible innovative strategies include the inhibition of bacterial virulence. However, consideration must be given to the evolutionary and environmental consequences of such new interventions. Virulence and cooperative social behaviour of the bacterium Pseudomonas aeruginosa rely on the quorum-sensing (QS) controlled production of extracellular products (public goods). Hence QS is an attractive target for anti-virulence interventions. During colonization, non-cooperating (and hence less virulent) P. aeruginosa QS-mutants, benefiting from public goods provided by wild type isolates, naturally increase in frequency providing a relative protection from invasive infection. We hypothesized that inhibition of QS-mediated gene expression removes this growth advantage and selection of less virulent QS-mutants, and maintains the predominance of more virulent QS-wild type bacteria. We addressed this possibility in a placebo-controlled trial investigating the anti-QS properties of azithromycin, a macrolide antibiotic devoid of bactericidal activity on P. aeruginosa, but interfering with QS, in intubated patients colonized by P. aeruginosa. In the absence of azithromycin, non-cooperating (and hence less virulent) lasR (QS)-mutants increased in frequency over time. Azithromycin significantly reduced QS-gene expression measured directly in tracheal aspirates. Concomitantly the advantage of lasR-mutants was lost and virulent wild-type isolates predominated during azithromycin treatment. We confirmed these results in vitro with fitness and invasion experiments. Azithromycin reduced growth rate of the wild-type, but not of the lasR-mutant. Furthermore, the lasR-mutant efficiently invaded wild-type populations in the absence, but not in the presence of azithromycin. These in vivo and in vitro results demonstrate that anti-virulence interventions based on QS-blockade diminish natural selection towards reduced virulence and therefore may increase the prevalence of more virulent genotypes in the Hospital environment. More generally, the impact of intervention on the evolution of virulence of pathogenic bacteria should be assessed.

Dataset Information

RpoN Regulates Virulence Factors of Pseudomonas aeruginosa via Modulating the PqsR Quorum Sensing Regulator.

Publications

RpoN Regulates Virulence Factors of Pseudomonas aeruginosa via Modulating the PqsR Quorum Sensing Regulator.

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