The 58th Cysteine of TcpP Is Essential for Vibrio cholerae Virulence Factor Production and Pathogenesis.

Mengting Shi,Na Li,Yuanyuan Xue,Menghua Yang,Zengtao Zhong

doi:10.3389/fmicb.2020.00118

Mengting Shi, Na Li + Show 3 more

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https://doi.org/10.3389/fmicb.2020.00118

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Abstract

Vibrio cholerae, the causative agent of the severe diarrheal disease cholera, has evolved signal transduction systems to control the expression of virulence determinants. It was previously shown that two cysteine residues in the periplasmic domain of TcpP are important for TcpP dimerization and activation of virulence gene expression by responding to environmental signals in the small intestine such as bile salts. In the cytoplasmic domain of TcpP, there are another four cysteine residues, C19, C51, C58, and C124. In this study, the functions of these four cysteine residues were investigated and we found that only C58 is essential for TcpP dimerization and for activating virulence gene expression. To better characterize this cysteine residue, site-directed mutagenesis was performed to assess the effects on TcpP homodimerization and virulence gene activation. A TcpPC58S mutant was unable to form homodimers and activate virulence gene expression, and did not colonize infant mice. However, a TcpPC19/51/124S mutant was not attenuated for virulence. These results suggest that C58 of TcpP is indispensable for TcpP function and is essential for V. cholerae virulence factor production and pathogenesis.

Highlights

Vibrio cholerae is a Gram-negative, facultative human pathogen and is the causative agent of cholera
We found that TcpPC19S, TcpPC51S, and TcpPC124S activated toxT expression to the same level as TcpP wild type (TcpPWT), but TcpPC58S did not (Figure 1)
We further investigated the functions of the cysteines in the cytoplasmic domain of TcpP, and we found that C58 is essential for TcpP homodimerization and activating virulence gene expression

Summary

Introduction

Vibrio cholerae is a Gram-negative, facultative human pathogen and is the causative agent of cholera. The Vibrio life cycle begins with a free swimming phase in aquatic environments. V. cholerae changes its transcriptional profile in different environmental niches to facilitate survival and colonization fitness (Zhu and Mekalanos, 2003; Moorthy and Watnick, 2005; Matson et al, 2007; Nielsen et al, 2010; Mandlik et al, 2011). In vivo virulence gene expression is induced by a number of host signals, including anoxic environment and chemicals present in the small intestine (Kovacikova et al, 2010; Yang et al, 2013; Fan et al, 2014; Hay et al, 2017; Midgett et al, 2017). Virulence genes are repressed and a coordinated “escape response” allows the organism to detach from the intestinal surface in preparation for exit from the host (Larocque et al, 2005; Nielsen et al, 2006, 2010)

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