Quorum Sensing Regulation of EHEC Virulence Genes

项目总结/摘要 为了在胃肠道（GI）中成功定殖并建立自身， 病原体必须感测并响应若干微生物群和宿主衍生的信号，以适当地 调节其毒力库的表达。胃肠道内的重要信号是 宿主神经递质去甲肾上腺素（NE）和/或肾上腺素（Epi），其具有重要的 在肠道生理学中的作用。还有一个重要的关系， 神经递质和微生物群，因为它调节活性Epi和NE的水平， 肠腔宿主将Epi/NE缀合至葡糖醛酸以使其降解。 编码使葡萄糖醛酸与Epi/NE解缀合的葡萄糖醛酸糖苷酶（由uidA基因编码）， 增加管腔中游离生物活性Epi/NE的水平。我们确认了前两个 细菌肾上腺素能受体，QseC和QseE。肠道致病菌肠出血性E. 大肠杆菌（EHEC），利用肾上腺素能信号通过QseC和QseE仔细调节 表达其毒力基因以促进肠道的最佳定殖。重要的是，EHEC 毒力基因调控与感知葡萄糖醛酸的能力交叉， 通过微生物群将Epi/NE的脱葡萄糖醛酸作用转化为在另一种水平的细胞间的Epi/NE感测。 王国信号我们确定了葡萄糖醛酸的传感器ExuR，作为一种重要的调节剂， 肠出血性大肠杆菌毒力基因表达通过QseC和QseE的Epi/NE感知的联系， 通过ExuR的葡萄糖醛酸传感，确保了毒力基因表达的精确控制， 肠出血性大肠杆菌事实上，啮齿类柠檬酸杆菌（广泛用作鼠EHEC的替代模型） 感染）qseC、qseE和exuR突变体对于鼠感染是减毒的，突出了 该信号系统在EHEC发病机制中的重要作用。另一种神经递质系统， 内源性大麻素系统也与肠道微生物群交织在一起。内源性大麻素 2-花生四烯酰甘油（2-AG）通过QseC感知，阻止QseC功能， 降低EHEC和C.啮齿动物。此外，Epi和2-AG 在QseC感受水平上相互拮抗。2AG水平从小到大逐渐降低， 肠到结肠，与Epi/NE水平相反。鉴于肠出血性大肠杆菌在 结肠，肾上腺素和内源性大麻素系统之间的相互作用，可能有一个关键 在胃肠道内病原体的胃肠道造影中起作用。因此， 具体目标1：研究肾上腺素能与 葡萄糖醛酸信号在EHEC发病机制中的作用。具体目标2：调查 内源性大麻素系统在EHEC发病机制中的作用 .

Project Summary/Abstract To successfully colonize and establish themselves in the gastrointestinal (GI) tract, enteric pathogens must sense and respond to several microbiota and host derived signals to properly regulate expression of their virulence repertoire. An important signal within the GI tract is the host neurotransmitter norepinephrine (NE) and/or epinephrine (Epi), which have important functions in intestinal physiology. There is also an important relationship between neurotransmitters and the microbiota, because it modulates the levels of active Epi and NE in the gut lumen. The host conjugates Epi/NE to glucuronate to inactivate it. The microbiota encodes glucuronidases (encoded by the uidA gene) that deconjugate glucuronate from Epi/NE, increasing the levels of free biologically active Epi/NE in the lumen. We identified the first two bacterial adrenergic receptors, QseC and QseE. The enteric pathogen enterohemorrhagic E. coli (EHEC), exploits adrenergic signaling through QseC and QseE to carefully regulate expression of its virulence genes to promote optimal colonization of the gut. Importantly, EHEC virulence gene regulation intersects with the ability to sense glucuronate, linking deglucuronidation of Epi/NE by the microbiota to Epi/NE sensing at another level of inter- kingdom signaling. We identified ExuR, the sensor for glucoronate, as an important regulator of EHEC virulence gene expression. The linking of Epi/NE sensing through QseC and QseE, with glucuronate sensing through ExuR, ensures the precise control of virulence gene expression by EHEC. Indeed, Citrobacter rodentium (extensively used as a surrogate EHEC model for murine infections) qseC, qseE and exuR mutants are attenuated for murine infection, highlighting the important role of this signaling system in EHEC pathogenesis. Another neurotransmitter system, the endocannabinoid system is also intertwined with the gut microbiota. The endocannabinoid 2-Arachidonoylglycerol (2-AG) is sensed through QseC, preventing QseC function, and decreasing expression of virulence genes in EHEC and C. rodentium. Moreover, Epi and 2-AG antagonize each other at the level of QseC sensing. The levels of 2AG decrease from the small intestine to the colon, oppositely from the levels of Epi/NE. Given that EHEC colonizes the colon, the interplay between the adrenergic and endocannabinoid systems, likely has a key function in the biogeography of this pathogen within the GI tract. Accordingly the specific aims of this proposal are: Specific Aim 1: Investigate the relationship among the adrenergic and glucuronate signals in EHEC pathogenesis. Specific Aim 2: Investigate the role of the endocannabinoid system in EHEC pathogenesis. .