Activation of caspase 3 during Legionella pneumophila-induced apoptosis
Activation of caspase 3 during Legionella pneumophila-induced apoptosis
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DOI：
10.1128/iai.67.9.4886-4894.1999
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发表时间：
1999-09-01
影响因子：
3.1
通讯作者：
Abu Kwaik, Y
中科院分区：
文献类型：
--
作者：
Gao, LY;Abu Kwaik, Y
军团病的标志是嗜肺军团菌在肺泡间隙的细胞内复制。嗜肺乳杆菌在细胞内复制并杀死宿主细胞的机制在很大程度上尚不清楚。我们最近发现，在感染开始的3小时内，在细胞内复制之前，嗜肺乳杆菌诱导巨噬细胞、肺泡上皮细胞和外周血单核细胞凋亡，这与细胞致病性有关（l -Y， Gao和Y， Abu Kwaik, infection）。免疫学。67:862-870,1999)。在本报告中，我们发现嗜肺乳杆菌诱导细胞凋亡的能力在很大程度上不受生长阶段的调节。我们证明嗜肺乳杆菌通过激活caspase 3介导巨噬细胞凋亡。caspase 3在体外切割特定合成底物的酶活性在感染后2小时检测到，在感染后3小时达到最大，活性增加900%以上。caspase 3在体内切割特定底物[聚（adp -核糖）聚合酶，或PARP]的活性也在感染后2小时检测到，并在感染后3小时达到最大值。caspase 3在体外和体内切割合成底物的活性被一种特异性的caspase 3抑制剂阻断，caspase 3的激活动力学与嗜肺乳杆菌诱导的核凋亡动力学相关。抑制caspase 3活性可阻断嗜肺乳杆菌感染早期诱导的细胞核凋亡和细胞致病性。与诱导细胞凋亡的能力一致，细胞外嗜肺乳杆菌也激活caspase 3。嗜肺乳杆菌的3个dotA/icmWXYZ突变体在诱导凋亡方面存在缺陷，但不能诱导caspase 3激活，这表明凋亡诱导因子的表达和/或输出受dot/icm毒力系统的调控。这是第一次描述caspase 3激活在被细菌病原体感染的宿主细胞中诱导核凋亡的作用。
The hallmark of Legionnaires' disease is replication of Legionella pneumophila within cells in the alveolar spaces. The mechanisms by which L. pneumophila replicates intracellularly and kills the host cell are largely not understood. We have recently shown that within 3 h of initiation of the infection and prior to intracellular replication, L. pneumophila induces apoptosis in macrophages, alveolar epithelial cells, and peripheral blood monocytes, which correlates with cytopathogenicity (L.-Y, Gao and Y, Abu Kwaik, Infect. Immun. 67:862-870, 1999). In this report, we show that the ability of L. pneumophila to induce apoptosis is, largely, not growth phase regulated. We demonstrate that the induction of apoptosis by L. pneumophila in macrophages is mediated through the activation of caspase 3. The enzymatic activity of caspase 3 to cleave a specific synthetic substrate in vitro is detected in L. pneumophila-infected macrophages at 2 h after infection and is maximal at 3 h, with over 900% increase in activity. The activity of caspase 3 to cleave a specific substrate [poly(ADP-ribose) polymerase, or PARP] in vivo is also detected at 2 h and is maximal at 3 h postinfection. The activity of caspase 3 to cleave the synthetic substrate in vitro and PARP in vivo is blocked by a specific inhibitor of caspase 3, The kinetics of caspase 3 activation correlates with that of L. pneumophila-induced nuclear apoptosis. Inhibition of caspase 3 activity blocks L. pneumophila induced nuclear apoptosis and cytopathogenicity during early stages of the infection. Consistent with the ability to induce apoptosis, extracellular L. pneumophila also activates caspase 3. Three dotA/icmWXYZ mutants of L. pneumophila that are defective in inducing apoptosis do not induce caspase 3 activation, suggesting that expression and/or export of the apoptosis-inducing factor(s) is regulated by the dot/icm virulence system. This is the first description of the role of caspase 3 activation in induction of nuclear apoptosis in the host cell infected by a bacterial pathogen.