Bonzon Christine, Bouchier-Hayes Lisa, Pagliari Lisa J, Green Douglas R, Newmeyer Donald D
Department of Molecular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA.
Mol Biol Cell. 2006 May;17(5):2150-7. doi: 10.1091/mbc.e05-12-1107. Epub 2006 Feb 22.
The mechanisms through which Caspase-2 leads to cell death are controversial. Here we show, using a combination of cell-free and cell culture-based approaches, that cleavage of the Bcl-2-family protein Bid is required for the induction of apoptosis by Caspase-2. Caspase-2 promoted cytochrome c release from mitochondria in the presence of cytosol from wild-type, but not Bid-deficient, mouse embryonic fibroblasts (MEFs). Recombinant wild-type Bid, but not a noncleavable mutant (D59E), restored cytochrome c release. Similarly, Bid-null MEFs were relatively resistant to apoptosis triggered by active Caspase-2, and apoptosis was restored in Bid-null cells by the expression of wild-type, but not D59E, Bid. Finally, Bid-null MEFs were substantially more resistant to apoptosis induced by heat shock, which has been shown to be dependent on apical activation of Caspase-2. The data are consistent with a model in which Caspase-2 induces apoptosis via cleavage of Bid at D59 and the subsequent engagement of the mitochondrial (intrinsic) pathway.
半胱天冬酶-2导致细胞死亡的机制存在争议。在此我们使用无细胞和基于细胞培养的方法相结合，证明半胱天冬酶-2诱导凋亡需要切割Bcl-2家族蛋白Bid。在存在来自野生型而非Bid缺陷型小鼠胚胎成纤维细胞（MEF）的胞质溶胶的情况下，半胱天冬酶-2促进细胞色素c从线粒体释放。重组野生型Bid而非不可切割的突变体（D59E）可恢复细胞色素c的释放。同样，Bid基因缺失的MEF对活性半胱天冬酶-2触发的凋亡相对抗性，通过表达野生型而非D59E Bid可使Bid基因缺失的细胞恢复凋亡。最后，Bid基因缺失的MEF对热休克诱导的凋亡具有更强的抗性，热休克已被证明依赖于半胱天冬酶-2的顶端激活。这些数据与一个模型一致，即半胱天冬酶-2通过在D59处切割Bid并随后激活线粒体（内在）途径来诱导凋亡。
