Pseudomonas Exotoxin A-Mediated Apoptosis Is Bak Dependent and Preceded by the Degradation of Mcl-1
Pseudomonas Exotoxin A-Mediated Apoptosis Is Bak Dependent and Preceded by the Degradation of Mcl-1
复制标题
DOI：
10.1128/mcb.00813-09
复制
发表时间：
2010-07-01
影响因子：
5.3
通讯作者：
Pastan, Ira
中科院分区：
文献类型：
--
作者：
Du, Xing;Youle, Richard J.;Pastan, Ira
假单胞菌外毒素 A (PE) 是一种细菌毒素，可阻止蛋白质合成并诱导细胞凋亡。在这里，我们利用 Bak 和 Bax 缺陷的小鼠胚胎成纤维细胞 (MEF) 来确定这些蛋白质在 PE 诱导的细胞死亡中的作用。 PE 在野生型 (WT) 和 Bax 敲除 (Bax(-/-)) MEF 中诱导快速且剂量依赖性的细胞凋亡，但在 Bak 敲除 (Bak(-/-)) 和 Bax/Bak 双敲除 (DKO) MEF 中失败。此外，在 WT 和 Bax(-/-) MEF 中观察到线粒体膜电位损失，但在 Bak(-/-) 或 DKO MEF 中未观察到，这表明 PE 对线粒体通透性有影响。 PE 介导的蛋白质合成抑制在所有 4 个细胞系中都是相同的，表明杀伤差异是由于 EF2 的 ADP-核糖基化后的步骤造成的。 PE 治疗后，Mcl-1（而非 Bcl-x(L)）迅速降解，这与 Mcl-1 在 PE 死亡途径中的作用一致。 Bak 与 MEF 中的 Mcl-1 和 Bcl-x(L) 相关，并在 PE 处理后与抑制的复合物解偶联。 Mcl-1 和 Bcl-x(L) 的过表达抑制 PE 诱导的 MEF 死亡。我们的数据表明，Bak 是 PE 介导的细胞凋亡的优先介质，并且 Mcl-1 的快速降解释放 Bak 来激活细胞凋亡。
Pseudomonas exotoxin A (PE) is a bacterial toxin that arrests protein synthesis and induces apoptosis. Here, we utilized mouse embryo fibroblasts (MEFs) deficient in Bak and Bax to determine the roles of these proteins in cell death induced by PE. PE induced a rapid and dose-dependent induction of apoptosis in wild-type (WT) and Bax knockout (Bax(-/-)) MEFs but failed in Bak knockout (Bak(-/-)) and Bax/Bak double-knockout (DKO) MEFs. Also a loss of mitochondrial membrane potential was observed in WT and Bax(-/-) MEFs, but not in Bak(-/-) or in DKO MEFs, indicating an effect of PE on mitochondrial permeability. PE-mediated inhibition of protein synthesis was identical in all 4 cell lines, indicating that differences in killing were due to steps after the ADP-ribosylation of EF2. Mcl-1, but not Bcl-x(L), was rapidly degraded after PE treatment, consistent with a role for Mcl-1 in the PE death pathway. Bak was associated with Mcl-1 and Bcl-x(L) in MEFs and uncoupled from suppressed complexes after PE treatment. Overexpression of Mcl-1 and Bcl-x(L) inhibited PE-induced MEF death. Our data suggest that Bak is the preferential mediator of PE-mediated apoptosis and that the rapid degradation of Mcl-1 unleashes Bak to activate apoptosis.