Overexpression of cysteine dioxygenase reduces intracellular cysteine and glutathione pools in HepG2/C3A cells
Overexpression of cysteine dioxygenase reduces intracellular cysteine and glutathione pools in HepG2/C3A cells
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DOI：
10.1152/ajpendo.00053.2007
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发表时间：
2007-07-01
影响因子：
5.1
通讯作者：
Stipanuk, Martha H.
中科院分区：
文献类型：
--
作者：
Dominy, John E., Jr.;Hwang, Jesse;Stipanuk, Martha H.
半胱氨酸水平在哺乳动物中被仔细调节，以平衡代谢需求和潜在的细胞毒性。据推测，哺乳动物细胞内半胱氨酸水平的主要调节剂之一是半胱氨酸双加氧酶（CDO）。这种分解代谢酶的肝脏表达响应于增加的半胱氨酸可用性而显著增加，因此可能是将过量的毒性半胱氨酸分流为更良性的代谢物（如硫酸盐或牛磺酸）的稳态响应的一部分。然而，缺乏直接的实验证据来支持CDO能够改变稳态细胞内半胱氨酸水平的假设。在这项研究中，我们在HepG 2/C3 A细胞（不表达内源性CDO蛋白）中表达CDO的野生型（WT）或催化失活突变体（H86 A）亚型，并将它们培养在不同浓度的细胞外半胱氨酸中。WT CDO而不是H86 A CDO能够降低在生理相关浓度的半胱氨酸中孵育的细胞中的细胞内半胱氨酸水平。WT CDO还降低了谷胱甘肽池并增强了CdC 12的毒性。这些结果表明CDO能够改变细胞内半胱氨酸水平以及谷胱甘肽水平。
Cysteine levels are carefully regulated in mammals to balance metabolic needs against the potential for cytotoxicity. It has been postulated that one of the major regulators of intracellular cysteine levels in mammals is cysteine dioxygenase (CDO). Hepatic expression of this catabolic enzyme increases dramatically in response to increased cysteine availability and may therefore be part of a homeostatic response to shunt excess toxic cysteine to more benign metabolites such as sulfate or taurine. Direct experimental evidence, however, is lacking to support the hypothesis that CDO is capable of altering steady-state intracellular cysteine levels. In this study, we expressed either the wild-type (WT) or a catalytically inactivated mutant (H86A) isoform of CDO in HepG2/C3A cells (which do not express endogenous CDO protein) and cultured them in different concentrations of extracellular cysteine. WT CDO, but not H86A CDO, was capable of reducing intracellular cysteine levels in cells incubated in physiologically relevant concentrations of cysteine. WT CDO also decreased the glutathione pool and potentiated the toxicity of CdC12. These results demonstrate that CDO is capable of altering intracellular cysteine levels as well as glutathione levels.