Steemans M, Goossens V, Van de Craen M, Van Herreweghe F, Vancompernolle K, De Vos K, Vandenabeele P, Grooten J
Department of Molecular Biology, Flanders Interuniversity Institute for Biotechnology and University of Gent, B-9000 Gent, Belgium.
J Exp Med. 1998 Dec 7;188(11):2193-8. doi: 10.1084/jem.188.11.2193.
It is well established that apoptosis is accompanied by activation of procaspases and by mitochondrial changes, such as decrease in mitochondrial transmembrane potential (DeltaPsim) and release of cytochrome c. We analyzed the causal relationship between activated caspases and these mitochondrial phenomena. Purified recombinant caspase-1, -11, -3, -6, -7, and -8 were incubated with mitochondria in the presence or absence of additional cellular components, after which DeltaPsim was determined. At lower caspase concentrations, only caspase-8 was able to activate a cytosolic factor, termed caspase-activated factor (CAF), which resulted in decrease in DeltaPsim and release of cytochrome c. Both CAF-mediated activities could not be blocked by protease inhibitors, including oligopeptide caspase inhibitors. CAF-induced cytochrome c release, but not decrease of DeltaPsim, was blocked in mitochondria from cells overexpressing Bcl-2. CAF is apparently involved in decrease of DeltaPsim and release of cytochrome c, whereas Bcl-2 only prevents the latter. Hence, CAF may form the link between death domain receptor-dependent activation of procaspase-8 and the mitochondrial events studied.
凋亡伴随着半胱天冬酶原的激活以及线粒体变化，如线粒体跨膜电位（ΔΨm）降低和细胞色素c释放，这一点已得到充分证实。我们分析了激活的半胱天冬酶与这些线粒体现象之间的因果关系。将纯化的重组半胱天冬酶-1、-11、-3、-6、-7和-8与线粒体在有无其他细胞成分的情况下孵育，之后测定ΔΨm。在较低的半胱天冬酶浓度下，只有半胱天冬酶-8能够激活一种胞质因子，称为半胱天冬酶激活因子（CAF），这导致ΔΨm降低和细胞色素c释放。包括寡肽半胱天冬酶抑制剂在内的蛋白酶抑制剂均不能阻断CAF介导的这两种活性。在过表达Bcl-2的细胞的线粒体中，CAF诱导的细胞色素c释放被阻断，但ΔΨm的降低未被阻断。CAF显然参与了ΔΨm的降低和细胞色素c的释放，而Bcl-2仅能阻止后者。因此，CAF可能构成了死亡结构域受体依赖性激活半胱天冬酶-8与所研究的线粒体事件之间的联系。
