Modulation of nitric oxide-mediated metal release from metallothionein by the redox state of glutathione in vitro
Modulation of nitric oxide-mediated metal release from metallothionein by the redox state of glutathione in vitro
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DOI：
10.1111/j.1432-1033.2004.04160.x
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发表时间：
2004-06-01
期刊：
影响因子：
--
通讯作者：
Zangger, K
中科院分区：
文献类型：
--
作者：
Khatai, L;Goessler, W;Zangger, K
金属硫蛋白（MT）在暴露于一氧化氮时释放结合的金属。在炎症部位，金属硫蛋白和诱导型一氧化氮合酶（iNOS）均由相同的因子诱导，并且NO从金属硫蛋白释放的锌抑制iNOS的诱导和活性。在寻找一种可能的调节机制，这种共同表达的抵消蛋白质，我们研究了谷胱甘肽的氧化还原状态在体外的作用，因为硫醇的氧化态参与金属结合在金属硫蛋白中发现的镉-硫或锌-硫簇，和NO也结合到还原型谷胱甘肽通过S-亚硝化。使用各种技术，我们发现，NO和ONOO-介导的金属释放从纯化的MT被抑制还原型谷胱甘肽（GSH），但不是由氧化型谷胱甘肽。考虑到哺乳动物细胞中存在的GSH的毫摩尔浓度，NO从MT释放的金属在生命系统中应该不起作用。因此，已经在体内观察到的事实指出了迄今为止未知的机制或参与该生理学相关反应的另外的化合物，并且只要没有发现该另外的因素，就应该谨慎对待关于MT-NO相互作用的实验结果。相反的过氧亚硝酸盐诱导的鸟苷酸环化酶的激活，其中GSH是必要的，我们发现，金属释放金属硫蛋白的过氧亚硝酸盐没有增强，但也抑制还原型谷胱甘肽。此外，我们表明，锌，主要的天然金属配体在哺乳动物的MT和iNOS的抑制剂，更容易释放NO的影响下比镉，但在MT亚型1相反，从MT-2的β-域释放的金属量是从α-域。
Metallothioneins (MTs) release bound metals when exposed to nitric oxide. At inflammatory sites, both metallothionein and inducible nitric oxide synthase (iNOS) are induced by the same factors and the zinc released from metallothionein by NO suppresses both the induction and activity of iNOS. In a search for a possible modulatory mechanism of this coexpression of counteracting proteins, we investigated the role of the glutathione redox state in vitro because the oxidation state of thiols is involved in the metal binding in Cd-S or Zn-S clusters found in metallothioneins, and NO also binds to reduced glutathione via S-nitrosation. Using a variety of techniques, we found that NO and also ONOO--mediated metal release from purified MTs is suppressed by reduced glutathione (GSH), but not by oxidized glutathione. Considering the millimolar concentrations of GSH present in mammalian cells, the metal release from MTs by NO should play no role in living systems. Therefore, the fact that it has been observed in vivo points to a hitherto unknown mechanism or additional compound(s) being involved in this physiologically relevant reaction and as long as this additional factor is not found experimental results on the MT-NO interaction should be treated with caution. Contrary to the peroxynitrite-induced activation of guanylyl cyclase, where GSH is needed, we found that the metal release from metallothionein by peroxynitrite is not enhanced, but also suppressed by reduced glutathione. In addition, we show that zinc, the major natural metal ligand in mammalian MTs and suppressor of iNOS, is released more readily under the influence of NO than cadmium, but in contrast to the MT isoform 1, the amount of metal released from the beta-domain of MT-2 is comparable to that from the alpha-domain.