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Distinct virulence ranges for infection of mice by Bordetella pertussis revealed by engineering of the sensor-kinase BvgS.

ABSTRACT: The whooping cough agent Bordetella pertussis coordinately regulates the expression of its virulence factors with the two-component system BvgAS. In laboratory conditions, specific chemical modulators are used to trigger phenotypic modulation of B. pertussis from its default virulent Bvg+ phase to avirulent Bvg- or intermediate Bvgi phases, in which no virulence factors or only a subset of them are produced, respectively. Whether phenotypic modulation occurs in the host remains unknown. In this work, recombinant B. pertussis strains harboring BvgS variants were tested in a mouse model of infection and analyzed using transcriptomic approaches. Recombinant BP-Bvg?65, which is in the Bvgi phase by default and can be up-modulated to the Bvg+ phase in vitro, could colonize the mouse nose but was rapidly cleared from the lungs, while Bvg+-phase strains colonized both organs for up to four weeks. These results indicated that phenotypic modulation, which might have restored the full virulence capability of BP-Bvg?65, does not occur in mice or is temporally or spatially restricted and has no effect in those conditions. Transcriptomic analyses of this and other recombinant Bvgi and Bvg+-phase strains revealed that two distinct ranges of virulence gene expression allow colonization of the mouse nose and lungs, respectively. We also showed that a recombinant strain expressing moderately lower levels of the virulence genes than its wild type parent was as efficient at colonizing both organs. Altogether, genetic modifications of BvgS generate a range of phenotypic phases, which are useful tools to decipher host-pathogen interactions.

SUBMITTER: Lesne E

PROVIDER: S-EPMC6181320 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Distinct virulence ranges for infection of mice by Bordetella pertussis revealed by engineering of the sensor-kinase BvgS.

Lesne Elodie E Coutte Loic L Solans Luis L Slupek Stephanie S Debrie Anne-Sophie AS Dhennin Véronique V Froguel Philippe P Hot David D Locht Camille C Antoine Rudy R Jacob-Dubuisson Françoise F

PloS one 20181011 10

The whooping cough agent Bordetella pertussis coordinately regulates the expression of its virulence factors with the two-component system BvgAS. In laboratory conditions, specific chemical modulators are used to trigger phenotypic modulation of B. pertussis from its default virulent Bvg+ phase to avirulent Bvg- or intermediate Bvgi phases, in which no virulence factors or only a subset of them are produced, respectively. Whether phenotypic modulation occurs in the host remains unknown. In this ...[more]

PMID: 30307950

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Project description:UnlabelledThe two-component system BvgAS controls the expression of the virulence regulon of Bordetella pertussis. BvgS is a prototype of bacterial sensor kinases with extracytoplasmic Venus flytrap perception domains. Following its transmembrane segment, BvgS harbors a cytoplasmic Per-Arnt-Sim (PAS) domain and then a predicted 2-helix coiled coil that precede the dimerization-histidine-phosphotransfer domain of the kinase. BvgS homologs have a similar domain organization, or they harbor only a predicted coiled coil between the transmembrane and the dimerization-histidine-phosphotransfer domains. Here, we show that the 2-helix coiled coil of BvgS regulates the enzymatic activity in a mechanical manner. Its marginally stable hydrophobic interface enables a switch between a state of great rotational dynamics in the kinase mode and a more rigid conformation in the phosphatase mode in response to signal perception by the periplasmic domains. We further show that the activity of BvgS is controlled in the same manner if its PAS domain is replaced with the natural α-helical sequences of PAS-less homologs. Clamshell motions of the Venus flytrap domains trigger the shift of the coiled coil's dynamics. Thus, we have uncovered a general mechanism of regulation for the BvgS family of Venus flytrap-containing two-component sensor kinases.ImportanceThe two-component system BvgAS of the whooping cough agent Bordetella pertussis regulates the virulence factors necessary for infection in a coordinated manner. BvgS is the prototype of a family of sensor kinase proteins found in major bacterial pathogens. When BvgS functions as a kinase, B. pertussis is virulent, and the bacterium shifts to an avirulent phase after BvgS senses chemicals that make it switch to phosphatase. Our goal is to decipher the signaling mechanisms of BvgS in order to understand virulence regulation in Bordetella, which may lead to new antimicrobial treatments targeting those two-component systems. We discovered that the activity of BvgS is regulated in a mechanical manner. A short region of the protein that precedes the enzymatic domain switches between two states in response to signal perception by other BvgS domains. This switch region is conserved among BvgS homologs, and thus, the regulation uncovered here will likely be relevant for the family.

Project description:The whooping cough agent, Bordetella pertussis, controls the expression of its large virulence regulon in a coordinated manner through the two-component system BvgAS. BvgS is a dimeric, multidomain sensor kinase. Each monomer comprises, in succession, tandem periplasmic Venus flytrap (VFT) domains, a transmembrane segment, a cytoplasmic Per-Arnt-Sim (PAS) domain, a kinase module, and additional phosphorelay domains. BvgS shifts between kinase and phosphatase modes of activity in response to chemical modulators that modify the clamshell motions of the VFT domains. We have shown previously that this regulation involves a shift between distinct states of conformation and dynamics of the two-helix coiled-coil linker preceding the enzymatic module. In this work, we determined the mechanism of signal transduction across the membrane via a first linker, which connects the VFT and PAS domains of BvgS, using extensive cysteine cross-linking analyses and other approaches. Modulator perception by the periplasmic domains appears to trigger a small, symmetrical motion of the transmembrane segments toward the periplasm, causing rearrangements of the noncanonical cytoplasmic coiled coil that follows. As a consequence, the interface of the PAS domains is modified, which affects the second linker and eventually causes the shift of enzymatic activity. The major features of this first linker are well conserved among BvgS homologs, indicating that the mechanism of signal transduction unveiled here is likely to be generally relevant for this family of sensor kinases.IMPORTANCEBordetella pertussis produces virulence factors coordinately regulated by the two-component system BvgAS. BvgS is a sensor kinase, and BvgA is a response regulator that activates gene transcription when phosphorylated by BvgS. Sensor kinases homologous to BvgS are also found in other pathogens. Our goal is to decipher the mechanisms of BvgS signaling, since these sensor kinases may represent new targets for antibacterial agents. Signal perception by the sensor domains of BvgS triggers small motions of the helical linker region underneath. The protein domain that follows this linker undergoes a large conformational change that amplifies the initial signal, causing a shift of activity from kinase to phosphatase. Because BvgS homologs harbor similar regions, these signaling mechanisms are likely to apply generally to that family of sensor kinases.

Project description:Bordetella pertussis regulates the production of its virulence factors by the two-component system BvgAS. In the virulence phase, BvgS phosphorylates BvgA, which then activates the transcription of virulence-activated genes (vags). In the avirulence phase, such as during growth in the presence of MgSO4, BvgA is not phosphorylated and the vags are not expressed. Instead, a set of virulence-repressed genes (vrgs) is expressed. Here, we performed transcriptome sequencing (RNAseq) analyses on B. pertussis cultivated with or without MgSO4 and on a BvgA-deficient Tohama I derivative. We observed that 146 genes were less expressed under modulating conditions or in the BvgA-deficient strain than under the nonmodulating condition, while 130 genes were more expressed. Some of the genes code for proteins with regulatory functions, suggesting a BvgA/S regulation cascade. To determine which genes are directly regulated by BvgA, we performed chromatin immunoprecipitation sequencing (ChIPseq) analyses. We identified 148 BvgA-binding sites, 91 within putative promoter regions, 52 within open reading frames, and 5 in noncoding regions. Among the former, 32 are in BvgA-regulated putative promoter regions. Some vags, such as dnt and fhaL, contain no BvgA-binding site, suggesting indirect BvgA regulation. Unexpectedly, BvgA also bound to some vrg putative promoter regions. Together, these observations indicate an unrecognized complexity of BvgA/S biology.IMPORTANCEBordetella pertussis, the etiological agent of whooping cough, remains a major global health problem. Despite the global usage of whole-cell vaccines since the 1950s and of acellular vaccines in the 1990s, it still is one of the most prevalent vaccine-preventable diseases in industrialized countries. Virulence of B. pertussis is controlled by BvgA/S, a two-component system responsible for upregulation of virulence-activated genes (vags) and downregulation of virulence-repressed genes (vrgs). By transcriptome sequencing (RNAseq) analyses, we identified more than 270 vags or vrgs, and chromatin immunoprecipitation sequencing (ChIPseq) analyses revealed 148 BvgA-binding sites, 91 within putative promoter regions, 52 within open reading frames, and 5 in noncoding regions. Some vags, such as dnt and fhaL, do not contain a BvgA-binding site, suggesting indirect regulation. In contrast, several vrgs and some genes not identified by RNAseq analyses under laboratory conditions contain strong BvgA-binding sites, indicating previously unappreciated complexities of BvgA/S biology.

Dataset Information

Distinct virulence ranges for infection of mice by Bordetella pertussis revealed by engineering of the sensor-kinase BvgS.

Publications

Distinct virulence ranges for infection of mice by Bordetella pertussis revealed by engineering of the sensor-kinase BvgS.

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