Modulation of apoptosis by Legionella Pneumophila

描述（由申请人提供）：嗜肺军团菌是一种细胞内病原体，它逃避内吞融合，劫持内质网到高尔基体的交通，将其吞噬体改造成内质网衍生的室，允许细胞内复制。嗜肺乳杆菌的Dot/lcm IV型分泌系统对吞噬体生物发生的调节和巨噬细胞凋亡途径的调节都是必不可少的，通过强大的早期和新颖的caspase-3激活，独立于细胞凋亡的内在和外在途径。Dot/lcm介导的caspase-3激活导致Rabaptin-5的裂解，Rabaptin-5是早期内体调节因子Rab5的效应物。使用caspase-3肽抑制剂抑制caspase-3可阻断嗜肺乳杆菌的细胞内复制，并导致生物体向吞噬溶酶体转运，类似于dot/icm突变体。我们的假设是：caspase -3介导的Rabaptin-5的裂解对军团菌吞噬体（LCP）的生物发生和细胞内复制至关重要。为了验证这一假设，我们的具体目的是检查以下内容：1 . caspase-3激活在LCP生物发生中的作用；特异性目的二：caspase-3介导的Rabaptin-5裂解在LCP生物发生中的作用具体目标三。参与caspase-3激活的嗜肺乳杆菌效应物的鉴定。意义：我们提出的研究是我们理解这种病原体占领宿主细胞的分子和细胞机制的关键，并将揭示这种病原体在凋亡途径和宿主细胞中的囊泡运输之间进行串扰以改造宿主细胞的细胞机制。参与这一过程的细菌效应物是治疗和预防该疾病的潜在靶点。

DESCRIPTION (provided by applicant): Legionella pneumophila is an intracellular pathogen that evades endocytic fusion and hijacks ER-to-golgi vesicle traffic to remodel its phagosome into an ER-derived compartment permissive for intracellular replication. The Dot/lcm type IV secretion system of L. pneumophila is essential for both modulation of phagosome biogenesis and modulation of the macrophage apoptotic pathways through robust early and novel activation of caspase-3, independent of the intrinsic and extrinsic pathways of apoptosis. The Dot/lcm- mediated activation of caspase-3 results in cleavage of Rabaptin-5, which is an effector of the early endosome regulator Rab5. Inhibition of caspase-3 using caspase-3 peptide inhibitors blocks intracellular replication of L. pneumophila and results in trafficking of the organism to phagolysosomes, similar to dot/icm mutants. Our hypothesis is: Caspase-3-meditaed cleavage of Rabaptin-5 is central to the arrested biogenesis of the Legionella-containing phagosome (LCP) and to intracellular replication. To test this hypothesis, our specific aims are to examine the following: Specific aim I. Role of caspase-3 activation in biogenesis of the LCP; Specific aim II: Role of caspase-3-mediated cleavage of Rabaptin-5 in biogenesis of the LCP; Specific aim III. Identification of the L. pneumophila effector involved in caspase-3 activation. Significance: Our proposed studies are the crux of our understanding of the molecular and cellular mechanisms by which this pathogen commandeer the host cell, and will she light on the cellular mechanism by which this pathogen engages a cross talk between the apoptotic pathways and vesicle traffic in the host cell to remodel it to its liking. The bacterial effector involved in this process is a potential target for therapy and prevention of the disease.