Redox imbalance in cystine/glutamate transporter-deficient mice
Redox imbalance in cystine/glutamate transporter-deficient mice
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DOI：
10.1074/jbc.m506439200
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发表时间：
2005-11-11
影响因子：
4.8
通讯作者：
Bannai, S
中科院分区：
文献类型：
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作者：
Sato, H;Shiiya, A;Bannai, S
胱氨酸/谷氨酸转运蛋白，命名为系统x（c）（-），介导哺乳动物细胞中胱氨酸进入细胞内以交换细胞内谷氨酸。该转运蛋白由xCT和4F 2重链两种蛋白质组分组成，预计前者介导转运活性。这种转运蛋白在维持培养细胞内GSH水平和细胞外胱氨酸/半胱氨酸氧化还原平衡方面起着关键作用。为了阐明这种转运蛋白在体内的生理作用，我们产生并表征了缺乏xCT的小鼠。xCT（-/-）小鼠外观健康且具有生育能力。然而，与同窝xCT（-/-）小鼠相比，这些小鼠血浆中胱氨酸浓度显著较高，而血浆半胱氨酸浓度无显著差异。xCT（-/-）小鼠血浆GSH水平低于xCT（+/+）小鼠。来自xCT（-/-）小鼠的胚胎成纤维细胞不能在常规培养基中存活，并且存活和生长需要2-巯基乙醇。当2-巯基乙醇从培养基中去除时，这些细胞中的半胱氨酸和GSH显著降低，并且细胞在24小时内开始死亡。N-乙酰半胱氨酸还拯救了xCT（-/-）衍生的细胞并允许生长。这些结果表明，系统x（c）（-）有助于维持血浆氧化还原平衡在体内，但在哺乳动物的发展，虽然它是至关重要的细胞在体外。
Cystine/glutamate transporter, designated as system x(c)(-), mediates cystine entry in exchange for intracellular glutamate in mammalian cells. This transporter consists of two protein components, xCT and 4F2 heavy chain, and the former is predicted to mediate the transport activity. This transporter plays a pivotal role for maintaining the intracellular GSH levels and extracellular cystine/ cysteine redox balance in cultured cells. To clarify the physiological roles of this transporter in vivo, we generated and characterized mice lacking xCT. The xCT(-/-) mice were healthy in appearance and fertile. However, cystine concentration in plasma was significantly higher in these mice, compared with that in the littermate xCT(-/-) mice, while there was no significant difference in plasma cysteine concentration. Plasma GSH level in xCT(-/-) mice was lower than that in the xCT(+/+) mice. The embryonic fibroblasts derived from xCT(-/-) mice failed to survive in routine culture medium, and 2-mercaptoethanol was required for survival and growth. When 2-mercaptoethanol was removed from the culture medium, cysteine and GSH in these cells dramatically decreased, and cells started to die within 24 h. N-Acetyl cysteine also rescued xCT(-/-)- derived cells and permitted growth. These results demonstrate that system x(c)(-) contributes to maintaining the plasma redox balance in vivo but is dispensable in mammalian development, although it is vitally important to cells in vitro.