Bacterial effector inhibition of type I interferon

描述(申请人提供)：我们发现了一种名为NleB的大肠杆菌蛋白，该蛋白高度保守，由对人类健康有重要意义的附着/消失(A/E)细菌病原体表达，是一种有效的宿主干扰素(IFN)产生的抑制因子。干扰素最初被发现是病毒感染细胞分泌的一种因子，能够中介保护其他细胞免受后续病毒感染。令人信服的是，I型干扰素不仅对抗病毒防御很重要，而且对宿主防御细菌感染也很重要。 由肠道细菌引起的腹泻疾病是一种主要的地方性健康威胁，也是食源性疾病日益频繁的来源。在这些肠道病原体中，肠致病性大肠埃希菌(EPEC)和肠出血性大肠杆菌(EHEC)分别是婴儿腹泻和出血性结肠炎的常见病因。EHEC尤其重要，因为它是导致儿童肾功能衰竭的主要原因。 虽然已知细菌和病毒病原体已经进化出干扰哺乳动物I型干扰素信号转导的策略，但作为革兰氏阴性病原体的重要毒力策略，第三型分泌系统(T3SS)的细菌效应蛋白转位能够抑制I型干扰素的产生的程度尚未观察到。这些研究将首次阐明T3SS效应器抑制干扰素的机制。在受感染的细胞中产生。 其具体目的是：1)鉴定NleB结合的导致干扰素-β降低的宿主蛋白(S)。被附着/清除病原体感染的细胞中的产物。2)通过附着/消除病原体来确定NleB和感染对TBK1的不同激活和降解相关泛素化的影响，TBK1是激活I型干扰素反应所必需的宿主蛋白激酶。 这些拟议的实验将对人类健康产生重大的积极影响，因为它们将使我们能够阐明一种新的机制，即肠道病原体通过抑制宿主的先天性免疫反应来促进它们的生存。首先，确定NleB抑制干扰素的宿主靶点及其分子机制。这项研究将为我们理解T3SS在感染过程中的作用靶点和机制提供重要的帮助。值得注意的是，T3SS效应器和I型干扰素途径之间的相互作用以前还没有报道。其次，阐明NleB的功能可能会为抗击细菌性腹泻疾病提供新的治疗策略。此外，我们的研究可能会提高对病毒-细菌混合感染的理解，并最终改进对病毒-细菌混合感染的治疗，因为NleB介导的I型干扰素抑制有可能加剧由具有胃肠道嗜性的病毒介导的腹泻疾病。 公共卫生相关性：大肠埃希氏菌可引起可能致命的腹泻疾病，并通过受污染的食物和水传播给人类。一组被称为干扰素的抗菌蛋白质对控制细菌感染非常重要。我们已经发现，大肠杆菌将一种名为NleB的蛋白质注射到受感染的肠道细胞中，这种蛋白质是干扰素反应的有效抑制因子。这项建议的重点是确定NleB用来抑制宿主干扰素产生的作用机制。从这些研究中获得的数据可能会提高我们预防和治疗细菌感染的能力。

DESCRIPTION (provided by applicant): We have discovered that an Escherichia coli protein named NleB, which is highly conserved and expressed by the attaching/effacing (A/E) bacterial pathogens of significance to human health, is a potent inhibitor of host interferon (IFN) production. IFN was originally discovered as a factor secreted by virally infected cells able to mediate protection of other cells from subsequent viral infection. It has become convincingly clear that type I IFNs are important not only to anti-viral defense but also to host defense against bacterial infection. Diarrheal disease caused by enteric bacteria is a major endemic health threat and an increasingly frequent source of foodborne illness. Among these enteric pathogens, enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC) are frequent causes of infantile diarhea and hemorhagic colitis, respectively. EHEC is especially significant because it is a leading cause of pediatric renal failure. While it is known that bacterial and viral pathogens have evolved strategies to interfere with mammalian type I IFN signaling, the extent to which bacterial effector proteins translocated by type III secretion systems (T3SS), an important virulence strategy of Gram-negative pathogens, are able to inhibit type I IFN production, has not been observed previously. These studies will elucidate, for the first time, the mechanism by which a T3SS effector inhibits IFN-? production in infected cells. The specific aims are to: 1) Characterize the host protein(s) to which NleB binds that results in decreased IFN-? production in cells infected by attaching/effacing pathogens. 2) Determine the impact of NleB and infection by attaching/effacing pathogens on the differential activation vs. degradation-associated ubiquitination of TBK1, a host protein kinase essential to activation of type I IFN responses. The proposed experiments will have a significant positive impact on human health because they will allow us to elucidate a novel mechanism by which enteric pathogens promote their survival by suppressing the host innate immune response. First, determining the host target of and molecular mechanism by which NleB inhibits IFN-? production will provide an important advance in our understanding of T3SS effector targets and mechanisms during infection. Notably, interplay between T3SS effectors and the type I interferon pathway has not been previously reported. Second, elucidating NleB function may suggest novel therapeutic strategies to combat bacterial diarrheal diseases. Additionally, our studies may improve the understanding of and eventually improve the treatment for viral-bacterial co-infections, as NleB-mediated suppression of type I IFN has the potential to exacerbate diarrheal illness mediated by viruses with gastrointestinal tropism. PUBLIC HEALTH RELEVANCE: Escherichia coli causes potentially fatal diarrheal disease and is transmitted to humans via contaminated food and water. A group of antimicrobial proteins known as interferons is important to controlling bacterial infection. We have discovered that E. coli injects into infected intestinal cells a protein named NleB that is a potent inhibitor of the interferon response. The focus of this proposal is to determine the mechanism of action used by NleB to inhibit host interferon production. Data obtained from these studies may improve our ability to prevent and treat bacterial infections.