Caspase-dependent initiation of apoptosis and necrosis by the Fas receptor in lymphoid cells: onset of necrosis is associated with delayed ceramide increase (Publication with Expression of Concern)
Caspase-dependent initiation of apoptosis and necrosis by the Fas receptor in lymphoid cells: onset of necrosis is associated with delayed ceramide increase (Publication with Expression of Concern)
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DOI：
10.1242/jcs.00153
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发表时间：
2002-12-01
影响因子：
4
通讯作者：
Quest, AFG
中科院分区：
文献类型：
--
作者：
Hetz, CA;Hunn, M;Quest, AFG
Fas受体的参与通过激活半胱天冬酶促进细胞凋亡。此外，经常观察到质膜脂质取向和细胞内神经酰胺水平的改变。在A20 B淋巴瘤细胞中，FasL诱导的细胞死亡和磷脂酰丝氨酸（PS）外化被通用半胱天冬酶抑制剂z-VAD-favor完全阻止。相比之下，caspase-3抑制剂Ac-DEVD-cho仅部分恢复细胞活力，对PS表面暴露没有影响。FasL处理后的流式细胞术分析鉴定了两个死亡细胞群。在一个，死亡是依赖于caspase-3和DNA片段化和细胞收缩。在第二种情况下，死亡发生在没有caspase-3活性和凋亡特征的情况下，但也被zVAD-favor阻断。根据形态学标准，这些细胞分别被鉴定为凋亡细胞和坏死细胞。使用荧光底物，caspase-3活性仅在凋亡细胞群中检测到，而caspase-8活性在两者中均检测到。还在Jurkat T细胞中的Fas下游检测到两种形式的半胱天冬酶-8依赖性细胞死亡，其中已经报道了Fas依赖性PS外化和延迟的神经酰胺产生，这与在A20细胞中显示的结果相似。然而，对于Raji B细胞，缺乏响应于Fas活化的脂质扰乱和神经酰胺产生，仅检测到凋亡。短链C2-或C6-神经酰胺，但不是各自的无活性的二氢化合物或用细菌鞘磷脂酶处理，在A20 B-、Raji B-和Jurkat T细胞中诱导主要是坏死性而不是凋亡性细胞死亡。因此，神经酰胺的延迟升高被提议促进Fas刺激的细胞中的坏死，其中半胱天冬酶-8活化不足以触发半胱天冬酶-3依赖性凋亡。
Engagement of the Fas receptor promotes apoptosis by activation of caspases. In addition, alterations in plasma membrane lipid orientation and intracellular ceramide levels are often observed. In A20 B-lymphoma cells, FasL-induced cell death and phosphatidylserine (PS) externalization were completely prevented by the generic caspase inhibitor z-VAD-fmk. By contrast, the caspase-3 inhibitor Ac-DEVD-cho only partially restored cell viability and had no effect on surface exposure of PS. Flow cytometric analysis after FasL treatment identified two populations of dead cells. In one, death was dependent on caspase-3 and paralleled by DNA fragmentation and cell shrinkage. In the second, death occurred in the absence of caspase-3 activity and apoptotic features but was also blocked by zVAD-fmk. By morphological criteria these were identified as apoptotic and necrotic cells, respectively. Using fluorescent substrates, caspase-3 activity was detected only in the apoptotic cell population, whereas caspase-8 activity was detected in both. Both forms of caspase-8-dependent cell death were also detected downstream of Fas in Jurkat T-cells, where Fas-dependent PS externalization and delayed ceramide production, which is similar to results shown here in A20 cells, have been reported. However, for Raji B-cells, lacking lipid scrambling and ceramide production in response to Fas activation, only apoptosis was detected. Short-chain C2- or C6-ceramides, but not the respective inactive dihydro compounds or treatment with bacterial sphingomyelinase, induced predominantly necrotic rather than apoptotic cell death in A20 B-, Raji B- and Jurkat T-cells. Thus, delayed elevation of ceramide is proposed to promote necrosis in those Fas-stimulated cells where caspase-8 activation was insufficient to trigger caspase-3-dependent apoptosis.