Modulation of apoptosis by Legionella Pneumophila

描述（由申请方提供）：嗜肺军团菌是一种细胞内病原体，可逃避内吞融合并劫持ER至高尔基体囊泡运输，将其吞噬体重塑为允许细胞内复制的ER衍生区室。L. L.的Dot/lcm Ⅳ型分泌系统。嗜肺细胞对于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需的，其通过稳健的早期和新的半胱天冬酶-3的活化，而不依赖于细胞凋亡的内在和外在途径。Dot/lcm介导的半胱天冬酶-3的活化导致Rabaptin-5的切割，Rabaptin-5是早期内体调节剂Rab 5的效应物。使用半胱天冬酶-3肽抑制剂抑制半胱天冬酶-3阻断L.与dot/icm突变体相似，pneumophila和导致生物体运输到吞噬溶酶体。我们的假设是：Caspase-3介导的Rabaptin-5的切割是含军团菌吞噬体（LCP）的生物发生停滞和细胞内复制的中心。为了检验这一假设，我们的具体目标是检查以下内容：具体目标I。半胱天冬酶-3活化在LCP生物发生中的作用;具体目标II：半胱天冬酶-3介导的Rabaptin-5切割在LCP生物发生中的作用;具体目标III。L.的鉴定。pneumophila效应子参与caspase-3激活。重要性：我们提出的研究是我们理解这种病原体霸占宿主细胞的分子和细胞机制的关键，并将阐明这种病原体在宿主细胞中参与凋亡途径和囊泡交通之间的串扰以重塑其喜好的细胞机制。参与这一过程的细菌效应物是治疗和预防疾病的潜在靶点。

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.