Dynamic Regulation of Epithelial Cell Survival by Enteropathogenic E. coli

描述(申请人提供)：致病性肠出血性大肠杆菌(EPEC)是一种引起腹泻的肠道病原体，是导致严重发病率和死亡率的原因，特别是在发展中国家的5岁以下儿童中。EPEC引起腹泻的确切机制(S)目前尚不清楚。这些细菌精心设计了一种类似注射器的III型分泌系统，将关键的毒力因子直接输送到宿主肠道上皮细胞。在感染的最初阶段，EPEC似乎特异性地限制了底层上皮细胞的死亡。这一建议的重点是通过III型分泌蛋白EspZ抑制宿主细胞死亡，EspZ是EPEC和相关病原体所独有的。在动物感染模型中，缺乏EspZ的菌株在定植和疾病方面受到严重损害。我们推测，EspZ与宿主蛋白相互作用，抑制感染的肠道细胞的过早死亡，从而在A/E病原体的肠道定植中发挥关键作用。我们建议(1)验证EspZ与宿主细胞伙伴的相互作用，定义EspZ相互作用结构域，并产生缺乏相互作用的特异性EspZ突变体(S)，(2)表征EspZ及其相互作用伙伴在激活有助于宿主细胞生存的信号通路中的作用，以及(3)通过动物感染模型确定EspZ及其相互作用伙伴在发病中的作用。了解EspZ的关键作用以及宿主存活在发病机制中的作用，可能会导致未来抑制EspZ功能的努力，从而控制EPEC相关性腹泻。

DESCRIPTION (provided by applicant): Enteropathogenic E. coli (EPEC), an intestinal pathogen that causes diarrhea, is responsible for significant morbidity and mortality, especially among children below 5 years of age in developing countries. The precise mechanism(s) by which EPEC causes diarrhea is currently not known. The bacteria elaborate a syringe-like type III secretion system that delivers key virulence factors directly into host intestinal epithelial cells. During the initial phase of infection, EPEC appears to specifically limit the death of the underlying epithelial cells. The focus of this proposal is the suppression of host cell death by the type III-secreted protein EspZ, which is unique to EPEC and related pathogens. Strains lacking EspZ are highly impaired for colonization and disease in animal models of infection. We hypothesize that EspZ interacts with host proteins to suppress premature death of infected enterocytes and, thereby, plays a key role in intestinal colonization by A/E pathogens. We propose to (1) validate the interaction of EspZ with host cell partners, define EspZ interaction domains, and generate specific EspZ mutants deficient for interaction(s), (2) characterize the role of EspZ and its interaction partners in activating signaling pathways that contribute to the survival of host cells, and (3) define the role of EspZ and its interaction partners in pathogenesis using animal models of infection. Understanding the key role of EspZ, and of host survival to pathogenesis, could lead to future efforts to inhibit EspZ function, and thereby control EPEC-associated diarrhea.