Bile salt-induced intermolecular disulfide bond formation activates Vibrio cholerae virulence
Bile salt-induced intermolecular disulfide bond formation activates Vibrio cholerae virulence
复制标题
胆盐诱导的分子间二硫键形成激活霍乱弧菌毒力
DOI：
10.1073/pnas.1218039110
复制
发表时间：
2013-02-05
影响因子：
11.1
通讯作者：
Zhu, Jun
中科院分区：
文献类型：
--
作者：
Yang, Menghua;Liu, Zhi;Zhu, Jun
为了成为成功的病原体，细菌必须经常限制毒力基因在宿主环境中的表达。这需要宿主环境的物理或化学标记以及用于感测宿主的存在以适当地确定毒力激活的时间的同源细菌系统。然而，已经有非常少的这样的信号传感器对确定，和主机传感的分子机制几乎是未知的。通过将霍乱弧菌的报告菌株直接应用于含有小鼠肠提取物的薄层色谱（TLC）板，我们发现了两个激活毒力基因转录的宿主信号。其中之一被发现是胆盐牛磺胆酸盐。然后，我们表明，一组胆汁盐引起跨膜转录因子TcpP的二聚化，诱导分子间的二硫键半胱氨酸（C）-207残基在其周质域。各种遗传和生物化学分析使我们提出了一个模型，其中周质结构域中的另一个半胱氨酸C218与C207形成抑制性分子内二硫键，C207必须异构化以形成活性C207-C207分子间键。然后，我们发现这些半胱氨酸突变对体内存活率的胆汁盐依赖性影响，与我们的体外模型相关。我们的研究结果证明了宿主信号分子直接激活霍乱弧菌毒力级联的机制。它们进一步提供了通过周质半胱氨酸氧化识别病原菌中宿主环境的范例。
To be successful pathogens, bacteria must often restrict the expression of virulence genes to host environments. This requires a physical or chemical marker of the host environment as well as a cognate bacterial system for sensing the presence of a host to appropriately time the activation of virulence. However, there have been remarkably few such signal-sensor pairs identified, and the molecular mechanisms for host-sensing are virtually unknown. By directly applying a reporter strain of Vibrio cholerae, the causative agent of cholera, to a thin layer chromatography (TLC) plate containing mouse intestinal extracts, we found two host signals that activate virulence gene transcription. One of these was revealed to be the bile salt taurocholate. We then show that a set of bile salts cause dimerization of the transmembrane transcription factor TcpP by inducing intermolecular disulfide bonds between cysteine (C)-207 residues in its periplasmic domain. Various genetic and biochemical analyses led us to propose a model in which the other cysteine in the periplasmic domain, C218, forms an inhibitory intramolecular disulfide bond with C207 that must be isomerized to form the active C207-C207 intermolecular bond. We then found bile salt-dependent effects of these cysteine mutations on survival in vivo, correlating to our in vitro model. Our results are a demonstration of a mechanism for direct activation of the V. cholerae virulence cascade by a host signal molecule. They further provide a paradigm for recognition of the host environment in pathogenic bacteria through periplasmic cysteine oxidation.