Bid truncation, Bid/Bax targeting to the mitochondria, and caspase activation associated with neutrophil apoptosis are inhibited by granulocyte colony-stimulating factor
Bid truncation, Bid/Bax targeting to the mitochondria, and caspase activation associated with neutrophil apoptosis are inhibited by granulocyte colony-stimulating factor
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DOI：
10.4049/jimmunol.172.11.7024
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发表时间：
2004-06-01
影响因子：
4.4
通讯作者：
Kuijpers, TW
中科院分区：
文献类型：
--
作者：
Maianski, NA;Roos, D;Kuijpers, TW
神经细胞凋亡构成了一种管理嗜中性粒细胞介导的反应的方式。它允许应对感染，但避免明显的旁观者组织损伤。使用毛地黄皂苷为基础的亚细胞分级分离和蛋白质印迹法，我们发现人类中性粒细胞的自发性凋亡（培养20小时后）与两种促凋亡Bcl-2同源物Bid和Bax易位到线粒体和Bid的截短相关，随后Omi/HtrA 2和Smac/DIABLO释放到胞质溶胶中。这些事件伴随着半胱天冬酶-8、半胱天冬酶-9和半胱天冬酶-3的加工和酶活性增加。G-CSF介导的细胞凋亡减少与所有这些反应的抑制一致。G-CSF诱导的效应差异依赖于新合成的介质。而Bax靶向线粒体的抑制和G-CSF对胱天蛋白酶激活的抑制依赖于蛋白质的合成，无论蛋白质合成抑制剂放线菌酮的存在，G-CSF都阻止了Bid截短和再分布。显然，观察到的Bid变化与中性粒细胞凋亡无关。尽管凋亡抑制蛋白（IAP）的调节因子Omi/HtrA 2和Smac/DIABLO在凋亡过程中被释放到胞质溶胶中，但我们没有观察到X-连锁IAP的裂解，这表明涉及IAP失活的另一种机制。总之，我们的研究结果支持线粒体在诱导和/或放大caspase活性中的整合作用，并表明G-CSF可能通过阻断Bid/Bax再分布和抑制caspase活化来起作用。
Neutrophil apoptosis constitutes a way of managing neutrophil-mediated reactions. It allows coping with infections, but avoiding overt bystander tissue damage. Using digitonin-based subcellular fractionation and Western blotting, we found that spontaneous apoptosis of human neutrophils (after similar to20 h of culture) was associated with translocation of two proapoptotic Bcl-2 homologues, Bid and Bax, to the mitochondria and truncation of Bid, with subsequent release of Omi/HtrA2 and Smac/DIABLO into the cytosol. These events were accompanied by processing and increased enzymatic activity of caspase-8, -9, and -3. A G-CSF-mediated reduction in apoptosis coincided with inhibition of all these reactions. The G-CSF-induced effects were differentially dependent on newly synthesized mediators. Whereas inhibition of Bax targeting to the mitochondria and inhibition of caspase activation by G-CSF were dependent on protein synthesis, Bid truncation and redistribution were prevented by G-CSF regardless of the presence of the protein synthesis inhibitor cycloheximide. Apparently, the observed Bid changes were dispensable for neutrophil apoptosis. Although the regulators of the inhibitor of apoptosis proteins (IAPs), Omi/HtrA2 and Smac/DIABLO, were released into the cytosol during apoptosis, we did not observe cleavage of X-linked IAP, which suggests that another mechanism of IAP deactivation is involved. Together our results support an integrative role of the mitochondria in induction and/or amplification of caspase activity and show that G-CSF may act by blocking Bid/Bax redistribution and inhibiting caspase activation.