The VarS/VarA two-component system modulates the activity of the Vibrio cholerae quorum-sensing transcriptional regulator HapR

Tsou, Amy M.; Li, Zhi; Cai, Tao; Zhu, Jun

doi:10.1099/mic.0.046235-0

Cited by 48 publications

(50 citation statements)

References 34 publications

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“…A possible explanation for this difference is that the luxC-lacZ fusion used in our study reflects the accumulation of active HapR protein, while previous studies used hapR-lacZ and hapR-GFP promoter and translational fusions (33,48). Recently, it was shown that HapR is additionally regulated at the level of activity (53).…”

Section: Discussionmentioning

confidence: 44%

Interplay among Cyclic Diguanylate, HapR, and the General Stress Response Regulator (RpoS) in the Regulation of Vibrio cholerae Hemagglutinin/Protease

Wang

Ayala

et al. 2011

J Bacteriol

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Vibrio cholerae secretes the Zn-dependent metalloprotease hemagglutinin (HA)/protease (mucinase), which is encoded by hapA and displays a broad range of potential pathogenic activities. Expression of HA/protease has a stringent requirement for the quorum-sensing regulator HapR and the general stress response regulator RpoS. Here we report that the second messenger cyclic diguanylic acid (c-di-GMP) regulates the production of HA/protease in a negative manner. Overexpression of a diguanylate cyclase to increase the cellular c-di-GMP pool resulted in diminished expression of HA/protease and its positive regulator, HapR. The effect of c-di-GMP on HapR was independent of LuxO but was abolished by deletion of the c-di-GMP binding protein VpsT, the LuxR-type regulator VqmA, or a single-base mutation in the hapR promoter that prevents autorepression. Though expression of HapR had a positive effect on RpoS biosynthesis, direct manipulation of the c-di-GMP pool at a high cell density did not significantly impact RpoS expression in the wild-type genetic background. In contrast, increasing the c-di-GMP pool severely inhibited RpoS expression in a ⌬hapR mutant that is locked in a regulatory state mimicking low cell density. Based on the above findings, we propose a model for the interplay between HapR, RpoS, and c-di-GMP in the regulation of HA/protease expression.Cholera is an acute waterborne diarrheal disease caused by Vibrio cholerae of serogroups O1 and O139. Infecting V. cholerae cells adhere to the intestinal mucosa, where they express major virulence factors such as the toxin coregulated pilus (TCP) (21) and cholera toxin (CT), which is largely responsible for the profuse rice-watery diarrhea typical of this illness (12,26). Cholera patients shed V. cholerae in their stools, which usually contain about 10 8 hyperinfective V. cholerae cells per ml (38). The V. cholerae cells can then survive and persist in fresh water and estuarine aquatic ecosystems to eventually gain entrance to a new host.The Zn-dependent metalloprotease hemagglutinin (HA)/ protease (18) has been proposed to facilitate V. cholerae detachment from the intestinal mucosa when infecting V. cholerae cells reach a high density (4,14,43,44). Inactivation of hapA, which encodes HA/protease, has been shown to enhance adherence to mucin-coated polystyrene plates (43), adherence to mucin-secreting differentiated HT29-18N2 cultured cells (4), and colonization of the suckling mouse intestine (41, 43). The mucinase activity of HA/protease (13), together with its capacity to cleave the mucin-binding adhesin GbpA at a high cell density, provides a mechanism that supports the "detachase" function attributed to this protein (25). In addition, HA/protease has been reported to perturb the paracellular barrier of cultured intestinal epithelial cells (37, 55) by acting on tight junction-associated proteins (56). In agreement with this finding, we have shown that HA/protease enhances enterotoxicity in the rabbit ileal loop model (43).The expression of flagellar motility ...

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Section: Discussionmentioning

confidence: 44%

Interplay among Cyclic Diguanylate, HapR, and the General Stress Response Regulator (RpoS) in the Regulation of Vibrio cholerae Hemagglutinin/Protease

Wang

Ayala

et al. 2011

J Bacteriol

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“…In V. cholerae, the VarS/VarA system could regulate the expression of CsrB and then control the QS through CsrA, a global regulatory protein (36). The VarS/VarA-CsrA/B/C/D system is involved in the control of HapA expression and biofilm production through HapR in V. cholerae (45,46). In this study, we found that CsrB could be involved in the regulation of the motility in V. alginolyticus, and it predicted the targets of CsrB by sRNA Target (47).…”

Section: Discussionmentioning

confidence: 99%

Chromatin Immunoprecipitation Sequencing Technology Reveals Global Regulatory Roles of Low-Cell-Density Quorum-Sensing Regulator AphA in the Pathogen Vibrio alginolyticus

Liu

Yang

et al. 2016

J Bacteriol

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Quorum sensing (QS) is an important regulatory system in virulence expression and environmental adaptation in bacteria. The master QS regulators (MQSR) LuxR and AphA reciprocally control QS gene expression in vibrios. However, the molecular basis for the regulatory functions of AphA remains undefined. In this study, we characterized its regulatory roles in Vibrio alginolyticus, an important zoonotic pathogen causing diseases in marine animals as well as in humans. AphA is involved in the motility ability, biofilm formation, and in vivo survival of V. alginolyticus. Specifically, AphA is expressed at low-cell-density growth phases. In addition, AphA negatively regulates the expression of the main virulence factor, alkaline serine protease (Asp), through LuxR. Chromatin immunoprecipitation (ChIP) followed by high-throughput DNA sequencing (ChIP-seq) detected 49 enriched loci harboring AphA-binding peaks across the V. alginolyticus genome. An AphA-specific binding motif was identified and further confirmed by electrophoretic mobility shift assay (EMSA) and mutagenesis analysis. A quantitative real-time PCR (qRT-PCR) assay further validated the regulation of AphA on these genes. AphA binds directly to the aphA promoter and negatively regulates its own expression. Moreover, AphA directly regulates genes encoding adenylate cyclase, anti-D , FabR, and the small RNA CsrB, revealing versatile regulatory roles of AphA in its physiology and virulence. Furthermore, our data indicated that AphA modulates motility through the coordinated function of LuxR and CsrB. Collectively, the findings of this work contribute to better understanding of the regulatory roles of AphA in QS and non-QS genes. IMPORTANCEIn this work, we determined that AphA, the master regulator of QS at low cell density, plays essential roles in expression of genes associated with physiology and virulence in V. alginolyticus, a Gram-negative pathogen for humans and marine animals. We further uncovered that 49 genes could be directly regulated by AphA and a 19-bp consensus binding sequence was identified. Among the 49 genes, the QS and other non-QS-associated genes were identified to be regulated by AphA. Besides, the small RNA CsrB was negatively regulated by AphA, and AphA regulate motility abilities through both CsrB and LuxR. Taken together, the findings of this study improve our understanding of the complex regulation network of AphA and QS. B acteria are highly social organisms capable of sophisticated cooperative behaviors mediated by the quorum-sensing (QS) system, a cell density-dependent signaling circuit (1). In Vibrio harveyi, there are three well-defined QS signaling molecules, known as autoinduers (AIs), including acylated homoserine lactones (HAI-1), furanosyl borate diester (AI-2), and CAI-1 (2). The membrane sensors LuxN, LuxQ, and CqsS can detect their cognate AIs and transduce the signals required to trigger gene expression through phospho-relay cascades (2). At low cell densities (LCDs; low AI concentrations), phosphates are directe...

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“…Instead, expression of HapR is regulated at the posttranscriptional level through interactions of hapR mRNA with a number of small RNAs (sRNAs) (140). Recent data indicate an integration of cell density with nutrient availability in quorum sensing (141), raising the possibility that another type of smallmolecule signal may serve as a ligand for HapR. The TFR DarR from M. smegmatis has been shown to interact with cyclic-di-AMP (142), providing a precedent for interactions between TFRs and second messengers.…”

Section: Quorum Sensingmentioning

confidence: 99%

The TetR Family of Regulators

Cuthbertson

Nodwell

2013

Microbiol Mol Biol Rev

480

512

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SUMMARY The most common prokaryotic signal transduction mechanisms are the one-component systems in which a single polypeptide contains both a sensory domain and a DNA-binding domain. Among the >20 classes of one-component systems, the TetR family of regulators (TFRs) are widely associated with antibiotic resistance and the regulation of genes encoding small-molecule exporters. However, TFRs play a much broader role, controlling genes involved in metabolism, antibiotic production, quorum sensing, and many other aspects of prokaryotic physiology. There are several well-established model systems for understanding these important proteins, and structural studies have begun to unveil the mechanisms by which they bind DNA and recognize small-molecule ligands. The sequences for more than 200,000 TFRs are available in the public databases, and genomics studies are identifying their target genes. Three-dimensional structures have been solved for close to 200 TFRs. Comparison of these structures reveals a common overall architecture of nine conserved α helices. The most important open question concerning TFR biology is the nature and diversity of their ligands and how these relate to the biochemical processes under their control.

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The VarS/VarA two-component system modulates the activity of the Vibrio cholerae quorum-sensing transcriptional regulator HapR

Cited by 48 publications

References 34 publications

Interplay among Cyclic Diguanylate, HapR, and the General Stress Response Regulator (RpoS) in the Regulation of Vibrio cholerae Hemagglutinin/Protease

Interplay among Cyclic Diguanylate, HapR, and the General Stress Response Regulator (RpoS) in the Regulation of Vibrio cholerae Hemagglutinin/Protease

Chromatin Immunoprecipitation Sequencing Technology Reveals Global Regulatory Roles of Low-Cell-Density Quorum-Sensing Regulator AphA in the Pathogen Vibrio alginolyticus

The TetR Family of Regulators

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