Hermisson M, Wagenknecht B, Wolburg H, Glaser T, Dichgans J, Weller M
Department of Neurology, University of Tübingen, School of Medicine, Germany.
Oncogene. 2000 May 4;19(19):2338-45. doi: 10.1038/sj.onc.1203554.
CD95L-induced apoptosis involves caspase activation and is facilitated when RNA and protein synthesis are inhibited. Here, we report that hyperthermia sensitizes malignant glioma cells to CD95L- and APO2L-induced apoptosis in the absence, but not in the presence, of inhibitors of RNA and protein synthesis. Hyperthermia does not alter CD95 expression at the cell surface and does not modulate the morphology of CD95-mediated cell death on electron microscopy. Bcl-2 gene transfer inhibits apoptosis and abrogates the sensitization mediated by hyperthermia. Hyperthermia does not overcome resistance to apoptosis conferred by the viral caspase inhibitor, crm-A, indicating the absolute requirement for the activation of crm-A-sensitive caspases, probably caspase 8, for apoptosis. CD95L-evoked DEVD-amc-cleaving caspase activity is enhanced by hyperthermia, suggesting that hyperthermia operates upstream of caspase processing to promote apoptosis. There is no uniformly enhanced processing of three caspase 3 substrates, poly-ADP ribose polymerase (PARP), protein kinase C (PKC) delta and DNA fragmentation factor (DFF) 45. Yet, hyperthermia promotes CD95L-evoked DNA fragmentation. Interestingly, hyperthermia enhances the CD95L-evoked release of cytochrome c in the absence, but not in the presence, of CHX. In contrast, the reduction of the mitochondrial membrane potential is enhanced by hyperthermia both in the absence and presence of CHX, and enhanced cytochrome c release is not associated with significantly enhanced caspase 9 processing. The potentiation of cytochrome c release at hyperthermic conditions in the absence of CHX is abrogated by Bcl-2. Thus, either hyperthermia or inhibition of protein synthesis by CHX potentiate cytotoxic cytokine-induced apoptosis. These pathways show no synergy, but rather redundance, indicating that CHX may function to promote apoptosis in response to cytotoxic cytokines by inhibiting the synthesis of specific proteins whose synthesis, function or degradation is temperature-sensitive.
CD95L诱导的细胞凋亡涉及半胱天冬酶激活，并且当RNA和蛋白质合成受到抑制时会加速。在此，我们报告，在不存在而非存在RNA和蛋白质合成抑制剂的情况下，热疗可使恶性胶质瘤细胞对CD95L和APO2L诱导的细胞凋亡敏感。热疗不会改变细胞表面CD95的表达，并且在电子显微镜下不会调节CD95介导的细胞死亡形态。Bcl-2基因转移可抑制细胞凋亡并消除热疗介导的敏感性。热疗不能克服病毒半胱天冬酶抑制剂crm-A所赋予的对细胞凋亡的抗性，这表明细胞凋亡绝对需要激活crm-A敏感的半胱天冬酶，可能是半胱天冬酶8。热疗可增强CD95L诱发的DEVD-氨基甲基香豆素切割半胱天冬酶活性，这表明热疗在半胱天冬酶加工的上游起作用以促进细胞凋亡。三种半胱天冬酶3底物，即聚ADP核糖聚合酶（PARP）、蛋白激酶C（PKC）δ和DNA片段化因子（DFF）45，并没有一致增强的加工过程。然而，热疗可促进CD95L诱发的DNA片段化。有趣的是，在不存在放线菌酮（CHX）的情况下，热疗可增强CD95L诱发的细胞色素c释放，但在存在CHX的情况下则不然。相反，无论是否存在CHX，热疗均可增强线粒体膜电位的降低，并且增强的细胞色素c释放与半胱天冬酶9加工的显著增强无关。在不存在CHX的情况下，热疗条件下细胞色素c释放的增强可被Bcl-2消除。因此，热疗或CHX对蛋白质合成的抑制均可增强细胞毒性细胞因子诱导的细胞凋亡。这些途径没有协同作用，而是存在冗余，这表明CHX可能通过抑制特定蛋白质的合成来促进对细胞毒性细胞因子的细胞凋亡反应，这些蛋白质的合成、功能或降解对温度敏感。
