Expression of the cystine-glutamate exchanger (xc-) in retinal ganglion cells and regulation by nitric oxide and oxidative stress
Expression of the cystine-glutamate exchanger (xc-) in retinal ganglion cells and regulation by nitric oxide and oxidative stress
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DOI：
10.1007/s00441-005-0116-x
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发表时间：
2006-05-01
影响因子：
3.6
通讯作者：
Smith, SB
中科院分区：
文献类型：
--
作者：
Dun, Y;Mysona, B;Smith, SB
胱氨酸-谷氨酸交换器，系统x（c）（-），介导胱氨酸进入细胞的Na+非依赖性交换，与细胞内谷氨酸的流出偶联。系统x（c）（-）在谷胱甘肽体内平衡中起关键作用。早期对大脑的研究表明，系统x（c）（-）主要存在于星形胶质细胞中，而不是神经元中。最近的研究表明，某些大脑神经元有一个活跃的系统x（c）（-）。在视网膜中，系统x（c）（-）已在Muller和视网膜色素上皮细胞中得到证实。我们最近提出，系统x（c）（-），xCT和4F 2 hc的两个蛋白质组分，存在于完整的视网膜的神经节细胞。在这里，我们已经使用（1）分子和免疫组织化学测定，以确定系统x（c）（-）是否存在于从新生小鼠视网膜分离的原代神经节细胞和（2）功能测定，以确定其活性是否由视网膜神经节细胞系（RGC-5）中的氧化应激调节。原代小鼠神经节细胞和RGC-5细胞表达xCT和4F 2 hc。RGC-5细胞在不存在Na+的情况下摄取[H-3]谷氨酸，并且这种摄取被系统x（c）（-）的已知底物（谷氨酸、半胱氨酸、胱氨酸、使君子酸）阻断。用NO和活性氧供体处理RGC-5细胞导致系统x（c）（-）的活性增加，与转运蛋白的最大速度增加相关，而底物亲和力没有显著变化。这是首次在原代视网膜神经节细胞和RGC-5细胞中发现x（c）（-）系统。在RGC-5细胞中，氧化应激上调该转运系统，并且该过程与xCT mRNA和蛋白的增加有关，但4F 2 hc mRNA或蛋白没有变化。
The cystine-glutamate exchanger, system x(c)(-), mediates the Na+-independent exchange of cystine into cells, coupled to the efflux of intracellular glutamate. System x(c)(-) plays a critical role in glutathione homeostasis. Early studies of brain suggested that system x(c)(-) was present primarily in astrocytes but not neurons. More recent work indicates that certain brain neurons have an active system x(c)(-). In the retina, system x(c)(-) has been demonstrated in Muller and retinal pigment epithelial cells. We have recently suggested that two protein components of system x(c)(-), xCT and 4F2hc, are present in ganglion cells of the intact retina. Here, we have used (1) molecular and immunohistochemical assays to determine whether system x(c)(-) is present in primary ganglion cells isolated from neonatal mouse retinas and (2) functional assays to determine whether its activity is regulated by oxidative stress in a retinal ganglion cell line (RGC-5). Primary mouse ganglion cells and RGC-5 cells express xCT and 4F2hc. RGC-5 cells take up [H-3] glutamate in the absence of Na+, and this uptake is blocked by known substrates of system x(c)(-) ( glutamate, cysteine, cystine, quisqualic acid). Treatment of RGC-5 cells with NO and reactive oxygen species donors leads to increased activity of system x(c)(-) associated with an increase in the maximal velocity of the transporter with no significant change in the substrate affinity. This is the first report of system x(c)(-) in primary retinal ganglion cells and RGC-5 cells. Oxidative stress upregulates this transport system in RGC-5 cells, and the process is associated with an increase in xCT mRNA and protein but no change in 4F2hc mRNA or protein.