Ethanolamine Signaling in Virulence Gene Regulation and Host/Microbial Interactions

 描述(申请人提供)：大肠杆菌O157：H7(EHEC)是一种食源性病原体，可在世界各地引起血性腹泻和溶血性尿毒症综合征(HUS)，HUS是EHEC疾病的并发症，可导致肾功能衰竭。EHEC的感染剂量非常低，因此很难在流行病学上进行控制。EHEC在大肠内定植，并附着在结肠上皮细胞上，导致微绒毛消失。EHEC还会产生志贺毒素，这种毒素会导致HUS的主要症状。为了成功地在宿主上定居并建立感染，EHEC必须能够与本土微生物群竞争营养。乙醇胺(EA)存在于胃肠道。EHEC使用EA作为氮源，从而获得了相对于本土微型生物群的竞争优势。重要的是，EHEC选择EA作为信号来促进与宿主定植和感染以及志贺毒素产生有关的基因的表达。转录调节因子EUTR激活编码EA代谢的基因的表达，我们确定EUTR促进EHEC毒力基因的表达。尽管EUTR在EHEC的致病过程中起重要作用，但对EHEC中EUTR基因调控的程度以及EUTR如何调控毒力基因知之甚少。在具体目标1中，我们将详细描述EUTR在EHEC致病中的作用，并研究EUTR毒力基因调控的机制。有趣的是，EHEC对EA做出反应，并调节EUTR突变株中毒力基因的表达，这表明EHEC编码第二个EA传感器。在特定的目标2中，我们将研究Ea依赖的、EUTR非依赖的毒力基因调控在EHEC中的作用和机制。具体目标3将阐述这些EA传感器如何在感染期间对EHEC的适合性和毒力基因表达做出贡献。所提出的实验方法将更好地理解EHEC激活其毒力基因的机制，并可能揭示EHEC发病机制的新方面。总之，这些数据可能导致制定干预和/或治疗EHEC疾病的独特战略。

 DESCRIPTION (provided by applicant): Escherichia coli O157:H7 (EHEC) is a food-borne pathogen that causes bloody diarrhea and hemolytic uremic syndrome (HUS), a complication of EHEC disease that can lead to kidney failure, throughout the world. EHEC has a very low infectious dose, making it difficult to control epidemiologically. EHEC colonizes the large intestine where it attaches to colonic epithelial cells and causes effacement of microvilli. EHEC also produces Shiga toxin that causes the major symptoms of HUS. In order to successfully colonize the host and establish infection, EHEC must be able to compete with the indigenous microbiota for nutrients. Ethanolamine (EA) is present in the gastrointestinal tract. EHEC uses EA as a nitrogen source, thereby gaining a competitive advantage over the indigenous micriobiota. Importantly, EHEC has co-opted EA as a signal to promote expression of genes involved in host colonization and infection as well as in Shiga toxin production. The transcriptional regulator EutR activates expression of genes that code for EA metabolism, and we determined that EutR promotes expression of EHEC virulence genes. Although EutR is important for EHEC pathogenesis, very little is known concerning the extent of EutR gene regulation in EHEC or how EutR functions to regulate virulence genes. In Specific Aim 1, we will perform a detailed characterization of the role of EutR in EHEC pathogenesis as well as examine the mechanisms of EutR virulence gene regulation. Interestingly, EHEC responds to EA and modulates virulence gene expression in the eutR mutant strain suggesting that EHEC encodes a second EA sensor. In Specific Aim 2, we will investigate the roles and mechanisms of EA-dependent, EutR-independent virulence gene regulation in EHEC. Specific Aim 3 will address how these EA-sensors contribute to EHEC fitness and virulence gene expression during infection. The proposed experimental approaches will achieve a better understanding of mechanisms used by EHEC to activate its virulence genes and may reveal novel aspects of EHEC pathogenesis. Altogether, these data may lead to the development of unique strategies for intervention and/or treatment for EHEC disease.