Ho Andrew T, Li Qin H, Hakem Razqallah, Mak Tak W, Zacksenhaus Eldad
Department of Medicine, Laboratory Medicine & Pathobiology and Medical Biophysics, Division of Cell & Molecular Biology, Toronto General Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada.
EMBO J. 2004 Jan 28;23(2):460-72. doi: 10.1038/sj.emboj.7600039. Epub 2004 Jan 8.
Inactivation of the tumor suppressor Rb in the mouse induces cell death, which depends entirely (in lens, CNS) and only partly (PNS, skeletal muscles) on Apaf1/Ced4, an apoptosomal factor thought to be required for processing procaspase-9 following mitochondrial permeabilization. Here, we report that in response to cytotoxic drugs, Apaf1(-/-) primary myoblasts but not fibroblasts undergo bona fide apoptosis. Cell demise was associated with disruption of mitochondria but not endoplasmic reticulum. Processing of procaspase-9 occurred in Apaf1(-/-) myoblasts but not fibroblasts, and ablation of Casp9 prevented drug-induced apoptosis in both cell types. Deregulation of the Rb pathway by overexpression of E2F1 also induced caspase-9-dependent, Apaf1-independent apoptosis in myoblasts. Despite its requirement for apoptosis in vitro, mutation in Casp9 abrogated cell death in the nervous system and lens but only partly in skeletal muscles of Rb-deficient embryos. In addition, developmental cell death in fetal liver and PNS was not inhibited in Casp9(-/-) embryos. Therefore, loss of pRb elicits apoptosome-dependent and apoptosome-independent cell death, and the requirement and coupling of caspase-9 to Apaf1 are both context-dependent.
小鼠体内肿瘤抑制因子Rb的失活会诱导细胞死亡，这种细胞死亡在晶状体、中枢神经系统中完全依赖于凋亡小体因子Apaf1/Ced4，而在周围神经系统、骨骼肌中则部分依赖于该因子。人们认为Apaf1/Ced4在线粒体通透性改变后处理前体半胱天冬酶-9的过程中是必需的。在此，我们报告，在细胞毒性药物作用下，Apaf1基因敲除的原代成肌细胞而非成纤维细胞会发生真正的凋亡。细胞死亡与线粒体的破坏有关，而与内质网无关。前体半胱天冬酶-9的加工在Apaf1基因敲除的成肌细胞中发生，而成纤维细胞中则未发生，并且敲除Casp9可阻止这两种细胞类型中药物诱导的凋亡。通过过表达E2F1对Rb通路进行失调调节也会在成肌细胞中诱导依赖于半胱天冬酶-9但不依赖于Apaf1的凋亡。尽管在体外凋亡过程中需要Casp9，但Casp9基因突变可消除Rb缺陷胚胎神经系统和晶状体中的细胞死亡，但仅部分消除骨骼肌中的细胞死亡。此外，Casp9基因敲除的胚胎中胎儿肝脏和周围神经系统的发育性细胞死亡并未受到抑制。因此，pRb的缺失会引发依赖凋亡小体和不依赖凋亡小体的细胞死亡，并且半胱天冬酶-9与Apaf1的需求及偶联均依赖于具体情况。
