The cystine-glutamate exchanger (system xc-) is responsible for the exchange of extracellular cystine for intracellular glutamate. In this study, we mapped the expression of xCT, the light chain subunit of system xc- in the different tissues of 3-6-week-old mouse (C57BL/6J) eye and have used an xCT knockout mouse to verify labelling specificity. Moreover, using the xCT knockout mouse, we investigated whether xCT was involved in maintaining extracellular redox balance in the eye. xCT transcript and protein were present in the cornea, lens and retina of wild-type mice, but not knockout mice. xCT was localised to the corneal epithelium, and the lens epithelium and cortical fibre cells but was absent in the iris. xCT localisation could not be determined in the ciliary body or retina, since xCT labelling was also detected in the knockout indicating a lack of specificity of the xCT antibody in tissues of a neural origin. Intracellular cysteine and cystine concentrations were similar in the wild-type and xCT knockout mouse for the cornea, lens, and retina. While extracellular cysteine levels were similar between the plasma, aqueous humour, and vitreous humour of the wild-type and xCT knockout mouse, extracellular cystine levels in the plasma and aqueous were significantly elevated in the xCT knockout mouse relative to the wild type. This suggests that loss of xCT results in an increased oxidative environment, particularly within the anterior chamber of the eye in which the aqueous humour resides. How this oxidative shift impacts ocular tissues that interface with the aqueous humour over time will be the focus of future work.

中文翻译：

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胱氨酸-谷氨酸交换子在小鼠眼中的定位：xCT在控制细胞外氧化还原平衡中的作用。

胱氨酸-谷氨酸交换剂（系统xc-）负责将细胞外胱氨酸交换为细胞内谷氨酸。在这项研究中，我们绘制了xCT（系统xc-轻链亚基）在3-6周龄小鼠（C57BL / 6J）眼的不同组织中的表达的图谱，并使用了xCT敲除小鼠来验证标记特异性。此外，使用xCT基因敲除小鼠，我们调查了xCT是否参与维持眼内细胞外氧化还原平衡。xCT转录本和蛋白质存在于野生型小鼠的角膜，晶状体和视网膜中，但不存在于敲除小鼠中。xCT定位于角膜上皮，晶状体上皮和皮质纤维细胞，但虹膜中不存在。无法确定在睫状体或视网膜中的xCT定位，因为在敲除物中也检测到xCT标记，表明xCT抗体在神经源组织中缺乏特异性。在野生型和xCT基因敲除小鼠中，角膜，晶状体和视网膜的细胞内半胱氨酸和胱氨酸浓度相似。虽然野生型和xCT基因敲除小鼠的血浆，房水和玻璃体液之间的细胞外半胱氨酸水平相似，但xCT基因敲除小鼠的血浆和水溶液中的细胞外半胱氨酸水平相对于野生型显着升高。这表明xCT的丧失导致氧化环境增加，特别是在房水所在的眼前房内。随着时间的流逝，这种氧化变化如何影响与房水接触的眼组织将成为未来工作的重点。