title: Vibrio cholerae anaerobic induction of virulence gene expression is controlled by thiol-based switches of virulence regulator AphB.
abstract: Bacterial pathogens have evolved sophisticated signal transduction systems to coordinately control the expression of virulence determinants. For example, the human pathogen Vibrio cholerae is able to respond to host environmental signals by activating transcriptional regulatory cascades. The host signals that stimulate V. cholerae virulence gene expression, however, are still poorly understood. Previous proteomic studies indicated that the ambient oxygen concentration plays a role in V. cholerae virulence gene expression. In this study, we found that under oxygen-limiting conditions, an environment similar to the intestines, V. cholerae virulence genes are highly expressed. We show that anaerobiosis enhances dimerization and activity of AphB, a transcriptional activator that is required for the expression of the key virulence regulator TcpP, which leads to the activation of virulence factor production. We further show that one of the three cysteine residues in AphB, C(235), is critical for oxygen responsiveness, as the AphB(C235S) mutant can activate virulence genes under aerobic conditions in vivo and can bind to tcpP promoters in the absence of reducing agents in vitro. Mass spectrometry analysis suggests that under aerobic conditions, AphB is modified at the C(235) residue. This modification is reversible between oxygen-rich aquatic environments and oxygen-limited human hosts, suggesting that V. cholerae may use a thiol-based switch mechanism to sense intestinal signals and activate virulence.
authors.affiliation: Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Liu
authors.forename: Menghua
authors.initials: M
authors.lastname: Yang
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Peterfreund
authors.forename: Amy M
authors.initials: AM
authors.lastname: Tsou
authors.forename: Nur
authors.initials: N
authors.lastname: Selamoglu
authors.forename: Fevzi
authors.initials: F
authors.lastname: Daldal
authors.forename: Zengtao
authors.initials: Z
authors.lastname: Zhong
authors.forename: Biao
authors.initials: B
authors.lastname: Kan
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
mesh_terms: D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000378:metabolism*; D003545:Cysteine / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D010100:Oxygen / Q000737:chemistry; D011401:Promoter Regions, Genetic; D040901:Proteomics; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014734:Vibrio cholerae / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence
chemical_list: C120327:AphB protein, Vibrio cholerae; D001426:Bacterial Proteins; D013438:Sulfhydryl Compounds; D015534:Trans-Activators; D003545:Cysteine; D010100:Oxygen