Modulation of host Apoptotic pathways by Legionella pneumophila

我们的目标是了解细胞内病原体嗜肺军团菌如何操纵宿主细胞 功能以促进其增殖，从而为设计新的治疗策略提供知识 用来治疗传染病。嗜肺乳杆菌的胞内生长需要Dot/LCM蛋白 将细菌效应物转移到受感染细胞中的分泌系统。这些效应器被认为是 调节宿主细胞的功能，以建立支持细菌复制的生态位。我们的 具体的假设是，在感染期间，Dot/LCM系统的底物SIDF主动预防 被感染的细胞不会发生凋亡。这一假说基于四个观察结果：1)细胞凋亡 在嗜肺性乳杆菌感染的允许的巨噬细胞中启动，但细胞并不是广泛的凋亡； 2)感染SIDF突变体的巨噬细胞比感染野生型细菌的巨噬细胞更易发生凋亡； SIDF与BNIP3和BclRambo两种促凋亡蛋白相互作用；4)表达SIDF的细胞具有耐药性 这些致死蛋白或化学试剂诱导的细胞凋亡。我们的具体目标是： 1.对SIDF突变体的感染表型进行彻底分析。我们将研究(I)是否 SIDF突变体在获取内质网标志物方面存在缺陷，(Ii)SIDF是否需要 嗜肺乳杆菌在其他类型宿主细胞中的细胞内生长和(III)原代细胞的凋亡反应 被突变体感染的巨噬细胞，(Iv)耗尽Bcl-Rambo如何影响细菌的细胞内生长。 2.分析SIDF与促凋亡蛋白BNIP3的相互作用以及这种相互作用是如何 影响嗜肺乳杆菌的胞内生长。我们将研究(I)SIDF结合对PRO-2的影响。 凋亡蛋白BNI PS介导的细胞凋亡，(II)BNI PS介导的细胞凋亡如何影响细胞内生长 以及(Iii)SIDF干扰BNIP3活性的机制。 3.鉴定嗜肺乳杆菌效应子(S)与SIDF协同调节宿主功能。我们 将确定(I)与BNIP3相互作用的非SIDF效应器，(Ii)细胞内生长所需的蛋白质 SIDF缺失突变背景和(Iii)与SIDF特异性相互作用形成多个 组件效应器复合体。

Our goal is to understand how the intracellular pathogen Legionella pneumophila manipulates host cellular functions to facilitate its multiplication, thus to provide knowledge for designing novel therapeutic strategies for treating infectious diseases. Intracellular growth of L. pneumophila requires the Dot/lcm protein secretion system that translocates bacterial effectors into infected cells. These effectors are believed to modulate host cellular functions for the establishment of a niche that supports bacterial replication. Our specific hypothesis is that during infection, SidF, a substrate of the Dot/lcm system actively prevents infected cells from undergoing apoptosis. This hypothesis is based on four observations: 1) Apoptosis is initiated in permissive macrophages infected by L. pneumophila but the cells are not extensively apoptotic; 2) Macrophages infected by a sidF mutant are more apoptotic than those infected by wild-type bacterium; 3) SidF interacts with two pro-apoptotic proteins, BNIP3 and Bcl-rambo; 4) Cells expressing SidF are resistant to apoptosis induced by these pro-death proteins or chemical agents . Our specific aims are to: 1. Perform a thorough analysis of infection phenotypes of a sidF mutant. We will examine (i) whether the sidF mutant is defective in acquiring endoplasmic reticulum markers, (ii)whether sidF is required for intracellular growth of L. pneumophila in other types of host cells and (iii) apoptotic response of primary macrophages infected by the mutant, (iv)how depletion of Bcl-rambo affects bacterial intracellulargrowth. 2. Analyze the interactions between SidF and the pro-apoptotic protein BNIP3 and how such interactions affect L. pneumophila intracellular growth. We will examine (i) the effect of SidF binding on the pro- apoptotic protein BNI PS-mediated apoptosis, (ii) how BNI PS-mediated apoptosis affects intracellular growth of L. pneumophila and (iii)the mechanisms of how SidF interferes with the activity of BNIP3. 3. Identify L. pneumophila effector(s) that function synergistically with SidF in modulating host functions. We will identify (i) non-SidF effectors that interact with BNIP3, (ii) proteins necessary for intracellular growth in the sidF deletion mutant background and (iii)proteins that specifically interact with SidF to form a multi- component effector complex.