Physiological concentrations of K+ inhibit cytochrome c-dependent formation of the apoptosome
Physiological concentrations of K+ inhibit cytochrome c-dependent formation of the apoptosome
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DOI：
10.1074/jbc.m107419200
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发表时间：
2001-11-09
影响因子：
4.8
通讯作者：
Cohen, GM
中科院分区：
文献类型：
--
作者：
Cain, K;Langlais, C;Cohen, GM
在许多形式的细胞凋亡中，从线粒体释放的细胞色素c诱导Apaf-1的寡聚化以形成半胱天冬酶激活的线粒体复合物。用dATP和细胞色素c在体外激活裂解物，导致形成类似于700-kDa凋亡体复合物（在凋亡细胞中占主导地位）的活性半胱天冬酶加工，以及类似于1.4-MDa复合物的相对无活性。我们现在证明，组装的活性复合物被抑制正常的细胞内浓度的K+。使用具有重组Apaf-1和细胞色素c的限定的溶酶体重构系统，K+还通过废除Apaf-1寡聚化和溶酶体组装来抑制半胱天冬酶活化。一旦组装，溶酶体对离子强度的影响相对不敏感，并加工/激活效应器半胱天冬酶。细胞色素c以浓度依赖性方式拮抗K+对线粒体形成的抑制作用。这些研究支持了这样的假设，即正常的细胞内K+浓度可以保护细胞免受由少量细胞色素c的无意释放引起的不适当的线粒体复合物的形成。因此，在细胞中的组装和激活的线粒体复合物需要细胞色素c的快速和广泛的释放，以克服正常的细胞内浓度的K+的抑制作用。
In many forms of apoptosis, cytochrome c released from mitochondria induces the oligomerization of Apaf-1 to form a caspase-activating apoptosome complex. Activation of lysates in vitro with dATP and cytochrome c results in the formation of an active caspase-processing similar to 700-kDa apoptosome complex, which predominates in apoptotic cells, and a relatively inactive similar to1.4-MDa complex. We now demonstrate that assembly of the active complex is suppressed by normal intracellular concentrations of K+. Using a defined apoptosome reconstitution system with recombinant Apaf-1 and cytochrome c, K+ also inhibits caspase activation by abrogating Apaf-1 oligomerization and apoptosome assembly. Once assembled, the apoptosome is relatively insensitive to the effects of ionic strength and processes/activates effector caspases. The inhibitory effects of K+ on apoptosome formation are antagonized in a concentration-dependent manner by cytochrome c. These studies support the hypothesis that the normal intracellular concentrations of K+ act to safeguard the cell against inappropriate formation of the apoptosome complex, caused by the inadvertent release of small amounts of cytochrome c. Thus, the assembly and activation of the apoptosome complex in the cell requires the rapid and extensive release of cytochrome c to overcome the inhibitory effects of normal intracellular concentrations of K+.