Subversion of membrane transport pathways by Legionella pneumophila

摘要/项目摘要 对细胞内细菌病原体及其与宿主相互作用的研究揭示了许多 宿主与病原体军备竞赛的有趣方面革兰氏阴性细菌嗜肺军团菌（Legionella pneumophila（L. p.） 引起一种严重的肺炎，称为军团病，特别有趣的是， 操纵几个主机交通过程，以建立其在内质网（ER）的复制生态位- 就像空泡一样。L. p.通过其IV型注射效应蛋白破坏宿主膜转运途径 分泌系统，Dot/Icm.了解细菌如何破坏宿主囊泡运输过程， 操纵它们使之对自己有利，为疾病和哺乳动物细胞生物学提供了宝贵的见解。 未折叠蛋白反应（UPR）是ER中重要的细胞保护途径，其由 各种病原体。有趣的是，虽然以前的工作表明，大多数病原体诱导UPR，我们 已经发现L. p.既激活又抑制它。UPR由三个ER膜传感器感测： ATF 6、PERK和IRE 1。IRE 1具有内腔结构域和胞质核糖核酸内切酶和激酶结构域。 我们已经表明，属于葡糖基转移酶家族的两种L. p.效应物，Lgt 1和Lgt 2（Lgt 1/2）， 阻断IRE 1介导的XBP 1u mRNA剪接。葡萄糖基转移酶是常见的病原体毒素 但从未观察到对mRNA剪接的影响。沿着普遍定期审议的典型作用， 由于未折叠蛋白在ER中应激，它也与先天性免疫反应有关。因此本 新的IRE 1角色激发了人们对以前未描述的关系的理解。 病原体和普遍定期审议。在第一个目标中，该提议将确定L. p. 葡糖基转移酶效应子。除了IRE 1，我们还发现L. p.也激活ATF 6。这导致 原型UPR转录本的上调。然而，未知的L. p.效应物能够阻断 翻译这些基因。我们的第二个目标是确定效应子并阐明 最后，在我们的第三个也是最后一个目标中，我们 我们希望了解L. p.如何激活ATF 6通路。这种相互作用的分子解剖将 揭示了细菌致病的新机制，并提供了探测和操纵UPR的工具， 它与许多人类疾病有关。 我们已经组建了一支非常强大的专家团队，并提供了令人信服的初步数据， 突出我们实现目标的能力。我们将联合收割机结合微生物学和分子遗传学 L. p.生物学的慕克吉实验室的专业知识与沃尔特实验室的细胞生物学专业知识， UPR途径的新型调节剂。

Abstract/Project Summary Study of intracellular bacterial pathogens and the interactions with their host have revealed many interesting aspects of host-pathogen arms race. The gram-negative bacterium Legionella pneumophila (L.p.) causes a severe form of pneumonia known as Legionnaires disease and is particularly interesting as it manipulates several host traffic processes to establish its replicative niche in an endoplasmic reticulum (ER)- like vacuole. L.p. subverts host membrane transport pathways by injecting effector proteins via its type IV secretion system, Dot/Icm. Understanding how bacteria sabotage host vesicular transport processes and manipulate them to their own advantage provides invaluable insights into disease and mammalian cell biology. The unfolded protein response (UPR) is an important cytoprotective pathway in the ER that is manipulated by various pathogens. Interestingly, while previous work demonstrated that most pathogens induce the UPR, we have discovered that L.p. both activates and inhibits it. The UPR is sensed by three ER membrane sensors: ATF6, PERK and IRE1. IRE1 has a lumenal domain and cytoplasmic endoribonuclease and kinase domains. We have shown that two L.p. effectors belonging to the glucosyltransferase family, Lgt1 and Lgt2 (Lgt1/2), block the IRE1-mediated XBP1u mRNA splicing. Glucosyltransferases are common among pathogen toxins but an effect on mRNA splicing has never been observed. Along with the UPR’s canonical role of sensing unfolded protein stress in the ER, it has also been implicated in the innate immune response. Therefore, this novel IRE1 role has energized efforts to understand previously uncharacterized relationships between pathogens and the UPR. In the first aim, this proposal will determine the mechanism of IRE1 inhibition by L.p. glucosyltransferase effectors. In addition to IRE1, we have discovered that L.p. also activates ATF6. This leads to the upregulation of prototypical UPR transcripts. However, yet unknown L.p. effectors are able to block the translation of some of these genes. Our second aim proposes to identify the effectors and elucidate the mechanism of post-transcriptional repression of UPR target genes by L.p. Lastly, in our third and final aim, we propose to understand how L.p. activates the ATF6 pathway. Molecular dissection of this interaction will unravel novel mechanisms of bacterial pathogenesis and provide tools for probing and manipulating the UPR, which is implicated in numerous human diseases. We have assembled an exceptionally strong team of experts and compelling preliminary data that highlight our ability to accomplish our goals. We will combine the microbiology and molecular genetics expertise of the Mukherjee lab in L.p. biology with the cell biology expertise of the Walter lab to discover novel regulators of the UPR pathway.