Elevated glutathione levels confer cellular sensitization to cisplatin toxicity by up-regulation of copper transporter hCtr1
Elevated glutathione levels confer cellular sensitization to cisplatin toxicity by up-regulation of copper transporter hCtr1
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DOI：
10.1124/mol.108.047969
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发表时间：
2008-09-01
影响因子：
3.6
通讯作者：
Kuo, Macus Tien
中科院分区：
文献类型：
--
作者：
Chen, Helen H. W.;Song, Im-Sook;Kuo, Macus Tien
以前的研究表明，顺铂（CDDP）处理培养的细胞上调谷胱甘肽（GSH）和其从头限速酶谷氨酸-半胱氨酸连接酶（GCL）的表达，GCL由催化（GCLC）和修饰（GCLM）亚基组成。还显示许多CDDP抗性细胞系表现出高水平的GCLC/GCLM和GSH。由于GSH系统是作为重要的解毒细胞保护剂的氧化还原条件的主要细胞内调节剂，因此这些结果已经考虑到GCL/GSH水平升高是CDDP抗性的原因。与此相反，我们在这里证明，通过转染含有GCLC cDNA的表达质粒，GSH的过表达通过上调人铜转运蛋白（hCtr）1（也是CDDP的转运蛋白）而对CDDP致敏。在这些转染细胞中耗尽GSH水平逆转CDDP敏感性，同时减少hCtr 1表达。虽然在转染细胞中铜转运率也上调，这些细胞表现出铜缺乏的生化特征，这表明GSH作为细胞内铜螯合剂的功能和GSH的过度表达可以改变铜代谢。更重要的是，我们的研究结果揭示了GSH在CDDP敏感性调节中的新作用。GSH的过量产生耗尽了生物可利用的铜池，导致hCtr 1的上调和CDDP运输和细胞杀伤的敏化。这些发现也有重要的意义，细胞内铜池的调制可能是一种新的策略，提高化疗疗效的铂类抗肿瘤药物。
Previous studies have demonstrated that treating cultured cells with cisplatin (CDDP) up-regulated the expression of glutathione (GSH) and its de novo rate-limiting enzyme glutamate-cysteine ligase (GCL), which consists of a catalytic (GCLC) and a modifier (GCLM) subunit. It has also been shown that many CDDP-resistant cell lines exhibit high levels of GCLC/GCLM and GSH. Because the GSH system is the major intracellular regulator of redox conditions that serve as an important detoxification cytoprotector, these results have been taken into consideration that elevated levels of GCL/GSH are responsible for the CDDP resistance. In contrast to this context, we demonstrated here that overexpression of GSH by transfection with an expression plasmid containing the GCLC cDNA conferred sensitization to CDDP through up-regulation of human copper transporter (hCtr) 1, which is also a transporter for CDDP. Depleting GSH levels in these transfected cells reversed CDDP sensitivity with concomitant reduction of hCtr1 expression. Although rates of copper transport were also up-regulated in the transfected cells, these cells exhibited biochemical signature of copper deficiency, suggesting that GSH functions as an intracellular copper-chelator and that overexpression of GSH can alter copper metabolism. More importantly, our results reveal a new role of GSH in the regulation of CDDP sensitivity. Overproduction of GSH depletes the bioavailable copper pool, leading to upregulation of hCtr1 and sensitization of CDDP transport and cell killing. These findings also have important implications in that modulation of the intracellular copper pool may be a novel strategy for improving chemotherapeutic efficacy of platinum-based antitumor agents.