Biroccio Annamaria, Benassi Barbara, Filomeni Giuseppe, Amodei Sarah, Marchini Sergio, Chiorino Giovanna, Rotilio Giuseppe, Zupi Gabriella, Ciriolo Maria Rosa
Experimental Chemotherapy Laboratory, Regina Elena Cancer Institute, Via delle Messi d'Oro, 00158 Rome, Italy.
J Biol Chem. 2002 Nov 15;277(46):43763-70. doi: 10.1074/jbc.M207684200. Epub 2002 Sep 10.
The objective of this article is to dissect the mechanisms by which the down-regulation of c-Myc induces programmed cell death in melanoma cells. In stable and doxycycline-inducible M14 melanoma cells, down-regulation of c-Myc induced apoptosis subsequent to a decrease in the intracellular reduced glutathione content and a concomitant accumulation of its oxidized form. This redox alteration was associated with a decrease of the enzyme activities of gamma-glutamyl-cysteine synthetase and NADPH-dependent GSSG reductase, as well as a consequent glutathione release in the extracellular medium. Cytochrome c was released into the cytosol at very early stages of apoptosis induction, long before detectable production of reactive oxygen species and activation of caspase-9 and -3. Macroarray analysis revealed that down-regulation of c-Myc produced striking changes in gene expression in the section related to metabolism, where the expression of gamma-glutamyl-cysteine synthetase and GSSG reductase was found to be significantly reduced. The addition of N-acetyl-l-cysteine or glutathione ethyl ester inhibited the apoptotic process, thus confirming the key role of glutathione in programmed cell death induced by c-Myc.
本文的目的是剖析c-Myc下调诱导黑色素瘤细胞程序性细胞死亡的机制。在稳定且可由强力霉素诱导的M14黑色素瘤细胞中，c-Myc下调导致细胞内还原型谷胱甘肽含量降低及其氧化形式相应积累后诱导细胞凋亡。这种氧化还原改变与γ-谷氨酰半胱氨酸合成酶和NADPH依赖性谷胱甘肽二硫化物还原酶的酶活性降低有关，以及随之而来的谷胱甘肽释放到细胞外培养基中。在凋亡诱导的非常早期阶段，细胞色素c就释放到细胞质中，远早于可检测到的活性氧产生以及caspase-9和-3的激活。基因芯片分析显示，c-Myc下调在与代谢相关的部分基因表达中产生了显著变化，其中γ-谷氨酰半胱氨酸合成酶和谷胱甘肽二硫化物还原酶的表达被发现显著降低。添加N-乙酰-L-半胱氨酸或谷胱甘肽乙酯抑制了凋亡过程，从而证实了谷胱甘肽在c-Myc诱导的程序性细胞死亡中的关键作用。
