Ceramide increases mitochondrial free calcium levels via caspase 8 and Bid: role in initiation of cell death
Ceramide increases mitochondrial free calcium levels via caspase 8 and Bid: role in initiation of cell death
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DOI：
10.1046/j.1471-4159.2003.01590.x
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发表时间：
2003-02-01
影响因子：
4.7
通讯作者：
Ruberg, M
中科院分区：
文献类型：
--
作者：
Darios, F;Lambeng, N;Ruberg, M
我们研究了神经生长因子（NGF）分化的PC12细胞中神经酰胺介导的细胞死亡的线粒体阶段是如何开始的。我们区分了神经酰胺的三个独立作用：自由基的产生；胞质游离钙的短暂增加；线粒体游离钙的持续增加。只有后者导致细胞死亡，这可以通过线粒体中钙结合蛋白calbindin D-28K的异位表达来缓冲线粒体钙来预防。我们发现线粒体钙并没有随着胞质游离钙水平的增加而增加。相反，它似乎源于内质网（ER），因为丹曲林（dantrolene）抑制钙从内质网通过红嘌呤受体释放到细胞质中，阻止了胞质游离钙的增加，但增强了线粒体游离钙的增加。这表明钙的转移直接或非常局部地发生在两个细胞器之间。这种转移涉及到半胱天冬酶8的激活及其底物Bid的切割，这是这些细胞死亡中介的一种以前未知的功能。线粒体游离钙的增加也导致细胞色素c释放到细胞质中，强调了它在神经酰胺介导的细胞死亡中所起的关键作用。
We investigated how the mitochondrial phase of ceramide-mediated cell death is initiated in nerve growth factor (NGF)-differentiated PC12 cells. We distinguished three independent effects of ceramide: free radical production; a transient increase in cytosolic free calcium; and a long-lasting increase in mitochondrial free calcium. Only the latter led to cell death, which could be prevented by buffering of mitochondrial calcium with the calcium binding protein calbindin D-28K ectopically expressed in mitochondria. We showed that mitochondrial calcium did not increase as a result of the increase in cytosolic free calcium levels. Rather, it appears to derive from the endoplasmic reticulum (ER) since dantrolene, which inhibits release of calcium from ER into cytosol through ryanodine receptors, prevented the increase in cytosolic free calcium but potentiated the increase in mitochondrial free calcium. This suggests that a transfer of calcium occurs directly, or very locally, between the two organelles. This transfer implicated activation of caspase 8 and cleavage of its substrate Bid, a previously unknown function of these cell death intermediaries. The increase in mitochondrial free calcium was also responsible for the release of cytochrome c into the cytosol, underlining the critical role it plays in ceramide-mediated cell death.