Vibrio cholerae CsrA Regulates ToxR Levels in Response to Amino Acids and Is Essential for Virulence.
Vibrio cholerae CsrA Regulates ToxR Levels in Response to Amino Acids and Is Essential for Virulence.
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DOI：
10.1128/mbio.01064-15
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发表时间：
2015-08-04
期刊：
影响因子：
6.4
通讯作者：
Payne SM
中科院分区：
文献类型：
--
作者：
Mey AR;Butz HA;Payne SM
ToxR是霍乱弧菌主要的毒力基因调控因子。虽然在许多实验室条件下组成型表达，但我们以前的工作表明，当细胞在天冬酰胺、精氨酸、谷氨酸和丝氨酸（NRES）4种氨基酸存在下生长时，ToxR的水平显著增加。我们在这里表明，响应NRES的ToxR生产的增加需要Var/Csr全球监管电路。VarS/VarA双组分系统控制活性CsrA的量，CsrA是一种参与调节广泛细胞过程的小RNA结合蛋白。我们的数据表明，varA突变体，这是预期过度产生活性CsrA，在没有NRES刺激ToxR水平升高。相反，CsrA中的特定氨基酸取代与响应NRES的ToxR产生缺陷相关。这些数据表明CsrA是ToxR水平的正调节剂。与先前描述的CsrA对毒力基因调控的影响不同，CsrA对ToxR的影响不是通过群体感应和HapR介导的。CsrA可能在霍乱弧菌中至关重要，因为不可能完全缺失CsrA;然而，CsrA的点突变耐受性良好。CsrA Arg 6 His突变体在体外具有野生型生长，但在霍乱弧菌感染的幼年小鼠模型中严重减毒，表明CsrA对发病机制至关重要。这项研究对我们理解霍乱弧菌如何将其对环境线索的反应与重要毒力基因的调控相结合具有广泛的意义。为了在人类宿主中定殖，霍乱弧菌必须感知并响应环境信号，以确保致病所需的基因的适当表达。揭示霍乱弧菌如何感知其环境并激活其毒力基因库对于我们了解霍乱弧菌如何从自然水生栖息地转变为人类宿主至关重要。在这里，我们证明了一个以前未知的全球监管CsrA和主要的霍乱弧菌毒力基因调节ToxR之间的联系。CsrA在细胞中的作用是接收来自环境的输入并协调适当的细胞反应。通过将环境感知与ToxR调节子连接起来，CsrA有效地充当响应特定信号控制发病机制的开关。我们证明，CsrA是关键的毒力在幼年小鼠模型的霍乱弧菌感染，其作为一个在体内的毒力基因表达的调节器的作用是一致的。
ToxR is a major virulence gene regulator in Vibrio cholerae. Although constitutively expressed under many laboratory conditions, our previous work demonstrated that the level of ToxR increases significantly when cells are grown in the presence of the 4 amino acids asparagine, arginine, glutamate, and serine (NRES). We show here that the increase in ToxR production in response to NRES requires the Var/Csr global regulatory circuit. The VarS/VarA two-component system controls the amount of active CsrA, a small RNA-binding protein involved in the regulation of a wide range of cellular processes. Our data show that a varA mutant, which is expected to overproduce active CsrA, had elevated levels of ToxR in the absence of the NRES stimulus. Conversely, specific amino acid substitutions in CsrA were associated with defects in ToxR production in response to NRES. These data indicate that CsrA is a positive regulator of ToxR levels. Unlike previously described effects of CsrA on virulence gene regulation, the effects of CsrA on ToxR were not mediated through quorum sensing and HapR. CsrA is likely essential in V. cholerae, since a complete deletion of csrA was not possible; however, point mutations in CsrA were tolerated well. The CsrA Arg6His mutant had wild-type growth in vitro but was severely attenuated in the infant mouse model of V. cholerae infection, showing that CsrA is critical for pathogenesis. This study has broad implications for our understanding of how V. cholerae integrates its response to environmental cues with the regulation of important virulence genes. In order to colonize the human host, Vibrio cholerae must sense and respond to environmental signals to ensure appropriate expression of genes required for pathogenesis. Uncovering how V. cholerae senses its environment and activates its virulence gene repertoire is critical for our understanding of how V. cholerae transitions from its natural aquatic habitat to the human host. Here we demonstrate a previously unknown link between the global regulator CsrA and the major V. cholerae virulence gene regulator ToxR. The role of CsrA in the cell is to receive input from the environment and coordinate an appropriate cellular response. By linking environmental sensing to the ToxR regulon, CsrA effectively acts as a switch that controls pathogenesis in response to specific signals. We demonstrate that CsrA is critical for virulence in the infant mouse model of V. cholerae infection, consistent with its role as an in vivo regulator of virulence gene expression.