Enhanced Interaction of Vibrio cholerae Virulence Regulators TcpP and ToxR under Oxygen-Limiting Conditions

Fan, Fenxia; Li, Zhi; Jabeen, Nusrat; Birdwell, L. Dillon; Zhu, Jun; Kan, Biao

doi:10.1128/iai.01377-13

Cited by 41 publications

(42 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, disulfide bond formation in ToxR has been shown to contribute to ompU regulation in response to some growth conditions (43). ToxR and TcpP have also been shown to form homodimers and heterodimers (44,45), and the bile salt taurocholate has been shown to induce intermolecular disulfide bond formation in the periplasmic domain of TcpP (46). Similarly, E. coli CadC has been shown to form disulfide bonds in response to pH, which result in the activation of cadBA transcription (47).…”

Section: Discussionmentioning

confidence: 99%

Vibrio cholerae leuO Transcription Is Positively Regulated by ToxR and Contributes to Bile Resistance

et al. 2015

View full text Add to dashboard Cite

Vibrio cholerae is an aquatic organism and facultative human pathogen that colonizes the small intestine. In the small intestine, V. cholerae is exposed to a variety of antimicrobial compounds, including bile. V. cholerae resistance to bile is multifactorial and includes alterations in the membrane permeability barrier that are mediated by ToxR, a membrane-associated transcription factor. ToxR has also been shown to be required for activation of the LysR family transcription factor leuO in response to cyclic dipeptides. LeuO has been implicated in the regulation of multiple V. cholerae phenotypes, including biofilm production and virulence. In this study, we investigated the effects of bile on leuO expression. We show that leuO transcription increased in response to bile and bile salts but not in response to other detergents. The bile-dependent increase in leuO expression was dependent on ToxR, which was found to bind directly to the leuO promoter. The periplasmic domain of ToxR was required for basal leuO expression and for the bile-dependent induction of both leuO and ompU transcription. V. cholerae mutants that did not express leuO exhibited increased bile susceptibility, suggesting that LeuO contributes to bile resistance. Our collective results demonstrate that ToxR activates leuO expression in response to bile and that LeuO is a component of the ToxR-dependent responses that contribute to bile resistance. IMPORTANCEThe success of Vibrio cholerae as a human pathogen is dependent upon its ability to rapidly adapt to changes in its growth environment. Growth in the human gastrointestinal tract requires the expression of genes that provide resistance to host antimicrobial compounds, including bile. In this work, we show for the first time that the LysR family regulator LeuO mediates responses in V. cholerae that contribute to bile resistance. Vibrio cholerae is a Gram-negative bacterial pathogen and the causal agent of the severe diarrheal disease cholera. V. cholerae exists naturally in aquatic reservoirs and is capable of colonizing the human small intestine. The transition of V. cholerae from the aquatic ecosystem to growth in the human gastrointestinal tract is mediated by transcriptional responses that are required for colonization and disease development. Many of the genes that contribute to intestinal colonization are under the control of the membrane-associated regulatory protein ToxR, which functions as one of the primary regulators in the ToxR regulon (reviewed in reference 1). The ToxR regulon is divided into two branches, a ToxTdependent branch, which controls the expression of virulence factors, and a ToxT-independent branch, which reciprocally regulates the production of the outer membrane porins OmpU and OmpT. The ToxT-dependent branch of the ToxR regulon is a hierarchical regulatory cascade that regulates the expression of genes encoding the production of cholera toxin (CT) and the toxin-coregulated pilus (TCP) in response to environmental cues in the host.ToxR is a membrane-associated ...

show abstract

Section: Discussionmentioning

confidence: 99%

Vibrio cholerae leuO Transcription Is Positively Regulated by ToxR and Contributes to Bile Resistance

et al. 2015

View full text Add to dashboard Cite

show abstract

“…All three domains of TcpP are required for virulence activation, whereas the membranespanning and periplasmic regions are sufficient for TcpP dimerization (21). In addition, TcpP and ToxR interact at the membrane and at the toxT promoter, but this interaction is abolished when the TcpP membrane-spanning region is swapped with the ToxR membrane region (32,41). These findings suggest that the interaction of ToxR and TcpP at the membrane is important for proper virulence induction.…”

Section: Discussionmentioning

confidence: 68%

“…TcpP is a membrane-bound regulatory protein, and the transmembrane domain of this protein is required for virulence activation (21,32). Bile salts are known to be detergents and to interact with membranes (33)(34)(35).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Calcium Enhances Bile Salt-Dependent Virulence Activation in Vibrio cholerae

et al. 2017

Self Cite

View full text Add to dashboard Cite

Vibrio cholerae is the causative bacteria of the diarrheal disease cholera, but it also persists in aquatic environments, where it displays an expression profile that is distinct from that during infection. Upon entry into the host, a tightly regulated circuit coordinates the induction of two major virulence factors: cholera toxin and a toxin-coregulated pilus (TCP). It has been shown that a set of bile salts, including taurocholate, serve as host signals to activate V. cholerae virulence through inducing the activity of the transmembrane virulence regulator TcpP. In this study, we investigated the role of calcium, an abundant mental ion in the gut, in the regulation of virulence. We show that whereas Ca 2ϩ alone does not affect virulence, Ca 2ϩ enhances bile salt-dependent virulence activation for V. cholerae. The induction of TCP by murine intestinal contents is counteracted when Ca 2ϩ is depleted by the high-affinity calcium chelator EGTA, suggesting that the calcium present in the gut is a relevant signal for V. cholerae virulence induction in vivo. We further show that Ca 2ϩ enhances virulence by promoting bile salt-induced TcpP-TcpP interaction. Moreover, fluorescence recovery after photobleaching (FRAP) analysis demonstrated that exposure to bile salts and Ca 2ϩ together decreases the recovery rate for fluorescently labeled TcpP, but not for another inner membrane protein (TatA). Together, these data support a model in which physiological levels of Ca 2ϩ may result in altered bile salt-induced TcpP protein movement and activity, ultimately leading to an increased expression of virulence.

show abstract

“…The next level of the cascade includes the aforementioned TcpP, along with the constitutively produced ToxR, both of which are integral membrane proteins that work in tandem to activate toxT transcription (10). TcpP activity recently has been shown to be enhanced by taurocholate (11), a bile salt, and interaction between TcpP and ToxR is enhanced under oxygen-limiting conditions (12). The final level of the cascade consists of ToxT, which directly activates the production of the major virulence factors cholera toxin (CT) and toxin coregulated pilus (TCP) (13)(14)(15)(16).…”

mentioning

confidence: 99%

Bicarbonate Increases Binding Affinity of Vibrio cholerae ToxT to Virulence Gene Promoters

Thomson

Withey

2014

J Bacteriol

View full text Add to dashboard Cite

The major Vibrio cholerae virulence gene transcription activator, ToxT, is responsible for the production of the diarrhea-inducing cholera toxin (CT) and the major colonization factor, toxin coregulated pilus (TCP). In addition to the two primary virulence factors mentioned, ToxT is responsible for the activation of accessory virulence genes, such as aldA, tagA, acfA, acfD, tcpI, and tarAB. ToxT activity is negatively modulated by bile and unsaturated fatty acids found in the upper small intestine. Conversely, previous work identified another intestinal signal, bicarbonate, which enhances the ability of ToxT to activate production of CT and TCP. The work presented here further elucidates the mechanism for the enhancement of ToxT activity by bicarbonate. Bicarbonate was found to increase the activation of ToxT-dependent accessory virulence promoters in addition to those that produce CT and TCP. Bicarbonate is taken up into the V. cholerae cell, where it positively affects ToxT activity by increasing DNA binding affinity for the virulence gene promoters that ToxT activates regardless of toxbox configuration. The increase in ToxT binding affinity in the presence of bicarbonate explains the elevated level of virulence gene transcription.

show abstract

Enhanced Interaction of Vibrio cholerae Virulence Regulators TcpP and ToxR under Oxygen-Limiting Conditions

Cited by 41 publications

References 39 publications

Vibrio cholerae leuO Transcription Is Positively Regulated by ToxR and Contributes to Bile Resistance

Vibrio cholerae leuO Transcription Is Positively Regulated by ToxR and Contributes to Bile Resistance

Calcium Enhances Bile Salt-Dependent Virulence Activation in Vibrio cholerae

Bicarbonate Increases Binding Affinity of Vibrio cholerae ToxT to Virulence Gene Promoters

Contact Info

Product

Resources

About