Group B Streptococcus induces macrophage apoptosis by calpain activation
Group B Streptococcus induces macrophage apoptosis by calpain activation
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DOI：
10.4049/jimmunol.176.12.7542
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发表时间：
2006-06-15
影响因子：
4.4
通讯作者：
Marconi, Pierfrancesco
中科院分区：
文献类型：
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作者：
Fettucciari, Katia;Fetriconi, Ilaria;Marconi, Pierfrancesco
B群链球菌(GBS)已经开发了几种策略来逃避免疫防御。我们发现GBS诱导巨噬细胞(M Phi)膜通透性缺陷和细胞凋亡，可通过抑制钙内流而不是半胱氨酸氨基转移酶来阻止。我们分析了GBS诱导小鼠M-Phi细胞凋亡的分子机制。GBS引起细胞内钙离子大量升高，与膜通透性缺陷和细胞凋亡的发生密切相关。钙的增加与钙依赖的蛋白水解酶的激活有关，酪蛋白酶谱显示，a-Spectrin裂解为calain的特异性片段，荧光Calain底物裂解，以及针对钙结合的3-(4-碘苯基)-2-巯基-(Z)-2-丙烯酸或活性部位(四种不同的抑制剂)的calain抑制剂，通过calain小干扰RNA(SiRNA)和EGTA抑制这些蛋白降解。所有微量和m-calain抑制剂和m-calain siRNA均能抑制GBS诱导的M-Phi细胞的凋亡，但不能抑制3-(5-Fluoro-3-indolyl)-2-mercapto-(Z)-2-propenoic酸和m-calain siRNA的作用，表明m-calain在细胞凋亡中起中心作用。紧随其后的是Bax和Bid裂解、细胞色素c、细胞凋亡诱导因子和线粒体释放的核酸内切酶G。在GBS诱导的细胞凋亡中，细胞色素c不能诱导caspase-3和-7的激活，因为它们和APAF-1可以被Calain降解。因此，细胞凋亡诱导因子和核酸内切酶G可能是GBS诱导细胞凋亡的主要介导物。非溶血性GBS不会发生促凋亡介质降解，不会诱导M-Phi细胞凋亡。Bax siRNA和Bid siRNA可减少细胞凋亡，提示Bax和Bid降解与细胞凋亡相关。与大多数病原体不同的是，这种信号通路可能代表了一种逃避免疫防御的GBS策略。
Group B Streptococcus (GBS) has developed several strategies, to evade immune defenses. We show that GBS induces macrophage (M phi) membrane permeability defects and apoptosis, prevented by inhibition of calcium influx but not caspases. We analyze the molecular mechanisms of GBS-induced murine M phi apoptosis. GBS causes a massive intracellular calcium increase, strictly correlated to membrane permeability defects and apoptosis onset. Calcium increase was associated with activation of calcium-dependent protease calpain, demonstrated by casein zymography, a-spectrin cleavage to a calpain-specific fragment, fluorogenic calpain-substrate cleavage, and inhibition of these proteolyses by calpain inhibitors targeting the calcium-binding, 3-(4-Iodophenyl)-2-mercapto-(Z)-2-propenoic acid, or active site (four different inhibitors), by calpain small-interfering-RNA (siRNA) and EGTA. GBS-induced M phi apoptosis was inhibited by all micro- and m-calpain inhibitors used and m-calpain siRNA, but not 3-(5-Fluoro-3-indolyl)-2-mercapto-(Z)-2-propenoic acid (micro-calpain inhibitor) and micro-calpain siRNA indicating that m-calpain plays a central role in apoptosis. Calpain activation is followed by Bax and Bid cleavage, cytochrome c, apoptosis-inducing factor, and endonuclease G release from mitochondria. In GBS-induced apoptosis, cytochrome c did not induce caspase-3 and -7 activation because they and APAF-1 were degraded by calpains. Therefore, apoptosis-inducing factor and endonuclease G seem the main mediators of the calpain-dependent but caspase-independent pathway of GBS-induced apoptosis. Proapoptotic mediator degradations do not occur with nonhemolytic GBS, not inducing M phi apoptosis. Apoptosis was reduced by Bax siRNA and Bid siRNA suggesting Bax and Bid degradation is apoptosis correlated. This signaling pathway, different from that of most pathogens, could represent a GBS strategy to evade immune defenses.