Susceptibility of the antioxidant selenoenyzmes thioredoxin reductase and glutathione peroxidase to alkylation-mediated inhibition by anticancer acylfulvenes.
Susceptibility of the antioxidant selenoenyzmes thioredoxin reductase and glutathione peroxidase to alkylation-mediated inhibition by anticancer acylfulvenes.
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DOI：
10.1021/tx2000152
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发表时间：
2011-05-16
影响因子：
4.1
通讯作者：
Sturla SJ
中科院分区：
文献类型：
--
作者：
Liu X;Pietsch KE;Sturla SJ
硒以硒代半胱氨酸的形式存在，是一些主要氧化还原调节酶的关键组分，包括硫氧还蛋白还原酶（TrxR）和谷胱甘肽过氧化物酶（Gpx）。由于TrxR在许多侵袭性人类肿瘤中的表达水平升高，其已成为药物开发的抗癌靶点。酰基富烯（AF）是天然产物伊鲁菌素S的半合成衍生物，并且显示出改善的细胞毒性选择性特征。AF和伊鲁菌素S使细胞大分子烷基化。与AF相比，伊鲁菌素S更容易与含巯基的小分子如半胱氨酸、谷胱甘肽和含半胱氨酸的肽反应。然而，先前的研究表明AF和伊鲁菌素S与谷胱甘肽还原酶（一种含硫醇的酶）的反应性与对小分子硫醇的反应性呈负相关。在这项研究中，我们调查的机制方面的酶和细胞的影响的AF和伊鲁菌素S硫氧还蛋白还原酶。AF和HMAF都被发现在低至亚微摩尔范围内抑制哺乳动物TrxR，但伊鲁菌素S的效力明显较低。AFs对TrxR的抑制作用是不可逆的，具有浓度和时间依赖性，并通过C-末端活性位点Sec/Cys残基的烷基化介导。相比之下，无论是AF还是伊鲁菌素S都不能抑制Gpx，这表明酶结构特异性小分子相互作用对Sec残基的固有反应性具有显著影响。在人类癌细胞中，TrxR活性可以被所有三种药物的低微摩尔浓度抑制。最后，研究表明，通过向细胞培养基中添加亚硒酸盐来预处理细胞导致细胞对AF的敏感性增强。这些数据表明，通过促进硒酶活性的联合治疗来增加药物活性的潜在策略。
Selenium, in the form of selenocysteine, is a critical component of some major redox-regulating enzymes, including thioredoxin reductase (TrxR) and glutathione peroxidase (Gpx). TrxR has emerged as an anticancer target for drug development due to its elevated expression level in many aggressive human tumors. Acylfulvenes (AFs) are semisynthetic derivatives of the natural product illudin S, and display improved cytotoxic selectivity profiles. AF and illudin S alkylate cellular macromolecules. Compared to AFs, illudin S more readily reacts with thiol-containing small molecules such as cysteine, glutathione and cysteine-containing peptides. However, a previous study indicates the reactivity of AFs and illudin S with glutathione reductase, a thiol-containing enzyme, are inversely correlated with reactivity toward small molecule thiols. In this study, we investigate mechanistic aspects underlying the enzymatic and cellular effects of the AFs and illudin S on thioredoxin reductase. Both AF and HMAF were found to inhibit mammalian TrxR in the low- to sub-micromolar range, but illudin S was significantly less potent. TrxR inhibition by AFs was shown to be irreversible, concentration- and time-dependent, and mediated by alkylation of C-terminus active site Sec/Cys residues. In contrast, neither AFs nor illudin S inhibit Gpx, demonstrating that enzyme structure-specific small molecule interactions have a significant influence over the inherent reactivity of the Sec residue. In human cancer cells, TrxR activity can be inhibited by low micromolar concentrations of all three drugs. Finally, it was demonstrated that preconditioning cells by addition of selenite to the cell culture media results in an enhancement in cell sensitivity towards AFs. These data suggest potential strategies for increasing drug activity by combination treatments that promote selenium enzyme activity.