Platyhelminth mitochondrial and cytosolic redox homeostasis is controlled by a single thioredoxin glutathione reductase and dependent on selenium and glutathione
Platyhelminth mitochondrial and cytosolic redox homeostasis is controlled by a single thioredoxin glutathione reductase and dependent on selenium and glutathione
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DOI：
10.1074/jbc.m710609200
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发表时间：
2008-06-27
影响因子：
4.8
通讯作者：
Salinas, Gustavo
中科院分区：
文献类型：
--
作者：
Bonilla, Mariana;Denicola, Ana;Salinas, Gustavo
扁形线虫寄生虫是发展中国家的一个主要健康问题。与哺乳动物宿主不同，扁形线虫的硫醇-二硫化物氧化还原动态平衡依赖于连接的硫氧还蛋白-谷胱甘肽系统，该系统完全依赖于硫氧还蛋白-谷胱甘肽还原酶(TGR)，这是一个有前途的药物靶标。TGR是一种由谷氧还蛋白结构域和硫氧还蛋白还原酶结构域组成的同源二聚体酶，其C端氧化还原中心含有硒半胱氨酸(SEC)。在这项研究中，我们证明了在细粒棘球绦虫的胞液和线粒体中存在功能性连接的硫氧还蛋白-谷胱甘肽系统，细粒棘球绦虫是导致包虫病的扁形蠕虫。谷胱甘肽还原酶(GR)活性受[GSSG]/[GSH]比值调节，表现出滞后行为。这一行为与GSSG的谷胱甘肽基化有关，但被去谷胱甘肽作用所消除。线粒体和胞质硫氧还蛋白的K-m和k(CAT)值分别为9.5mM和131mU S(-1)，34mU M和197mU S(-1)，均高于报道的哺乳动物TRs。对TGR突变体的分析表明，谷氧还蛋白结构域是GR活性所必需的，但不影响TR活性。相反，GR和TR的活性都依赖于含有SEC的氧化还原中心。由Sec-to-Cys突变引起的活性损失可以被邻近残基的Cys-to-Sec突变部分补偿，这表明SEC可以支持该替代位置的催化。与TGR在氧化还原控制中的关键作用一致，已知的TGR抑制剂2.5亩M Auranofin在体外杀死了幼虫。这些研究通过单一的TGR酶建立了依赖于硒和谷胱甘肽的细胞内和线粒体氧化还原动态平衡的调节。
Platyhelminth parasites are a major health problem in developing countries. In contrast to their mammalian hosts, platyhelminth thiol-disulfide redox homeostasis relies on linked thioredoxin-glutathione systems, which are fully dependent on thioredoxin-glutathione reductase (TGR), a promising drug target. TGR is a homodimeric enzyme comprising a glutaredoxin domain and thioredoxin reductase (TR) domains with a C-terminal redox center containing selenocysteine ( Sec). In this study, we demonstrate the existence of functional linked thioredoxin- glutathione systems in the cytosolic and mitochondrial compartments of Echinococcus granulosus, the platyhelminth responsible for hydatid disease. The glutathione reductase (GR) activity of TGR exhibited hysteretic behavior regulated by the [GSSG]/[GSH] ratio. This behavior was associated with glutathionylation by GSSG and abolished by deglutathionylation. The K-m and k(cat) values for mitochondrial and cytosolic thioredoxins (9.5 mu M and 131 s(-1), 34 mu M and 197 s(-1), respectively) were higher than those reported for mammalian TRs. Analysis of TGR mutants revealed that the glutaredoxin domain is required for the GR activity but did not affect the TR activity. In contrast, both GR and TR activities were dependent on the Sec-containing redox center. The activity loss caused by the Sec-to-Cys mutation could be partially compensated by a Cys-to-Sec mutation of the neighboring residue, indicating that Sec can support catalysis at this alternative position. Consistent with the essential role of TGR in redox control, 2.5 mu M auranofin, a known TGR inhibitor, killed larval worms in vitro. These studies establish the selenium and glutathione-dependent regulation of cytosolic and mitochondrial redox homeostasis through a single TGR enzyme in platyhelminths.