INSULIN RECEPTOR THIOL REACTIVITY AND INSULIN SIGNALING

工作概述：胰岛素受体是一个成员， 蛋白质酪氨酸激酶家族的一个重要组成部分， 不同的生理过程，包括葡萄糖的调节 稳态和基因表达。早期的研究发现， 胰岛素受体的功能活性可以通过以下方式调节 细胞环境中的氧化还原调节。血浆浓度升高 自由基的产生， 血浆谷胱甘肽（GSH）水平与 老年人和2型糖尿病患者的胰岛素作用降低 患者据信谷胱甘肽氧化还原状态的改变是 这可能是一个重要因素，可以解释 病理性胰岛素抵抗是2型糖尿病的常见特征 和衰老。事实上，GSH的管理，这构成了 血浆非蛋白硫醇的主要来源，显著改善 胰岛素通过升高血浆葡萄糖浓度调节葡萄糖稳态 糖尿病患者的GSH/GSSG比值。因为它不能穿透细胞 很容易，我们假设GSH可能在结构上起作用， 和/或胰岛素受体的功能变化，从而改变 胰岛素反应性在这项研究中，我们表明， 用GSH而不是氧化的GSSG衍生物培养的细胞 减少剂量中的胰岛素受体α-亚基硫醇-和 时间依赖性从孵育物中去除GSH 培养基迅速恢复胰岛素的天然巯基氧化还原状态 受体α亚单位N-乙酰半胱氨酸（NAC），一种广泛使用的 巯基水平的调节剂，作为细胞保护药物， 多种治疗应用，部分是通过直接充当 还原剂与GSH一样，NAC治疗导致 在胰岛素受体α亚单位中巯基反应性的水平 在NAC移除后逆转。低聚 胰岛素受体的结构不受GSH或NAC的影响 治疗有趣的是，胰岛素的反应性增强 受体α亚基巯基与GSH或NAC的影响不大， 胰岛素结合，但选择性增加胰岛素刺激的变化， 胰岛素信号转导正在取得进展 反应性受体巯基的鉴定。我们计划 评估从2型分离的胰岛素受体的巯基反应性 糖尿病患者和老年动物在GSH或NAC之前和之后 局

Summary of work: The insulin receptor is a member of the protein tyrosine kinase family that plays an important role in diverse physiological processes, including modulation of glucose homeostasis and gene expression. Earlier findings have found that the functional activity of the insulin receptor may be modulated by redox regulation in the cellular environment. An increase in plasma free radical production combined with a significant reduction in plasma glutathione (GSH) levels have been associated with a reduction in insulin action both in the elderly and type 2 diabetic patients. It is believed that alteration in glutathione redox status is likely to be an important factor which may account for the pathologic insulin resistance, a common feature of type 2 diabetes and aging. Indeed, administation of GSH, which constitutes the major source of plasma nonprotein thiols, significantly improves the modulation of glucose homeostasis by insulin by raising the plasma GSH/GSSG ratio in diabetics. Because it does not penetrate cells readily, we hypothesized that GSH may play a role in structural and/or functional changes in the insulin receptor, thereby altering insulin responsiveness. In this study, we show that treatment of cultured cells with GSH but not the oxidized GSSG derivative reduces insulin receptor alpha-subunit thiols in a dose- and time-dependent manner. Removal of GSH from the incubation medium rapidly restores the native thiol redox status of the insulin receptor alpha subunit. N-acetylcysteine (NAC), a widely used modulator of thiol levels, acts as a cytoprotective drug with multiple therapeutic applications, in part, by acting directly as a reducing agent. Like GSH, NAC treatment resulted in an increase in the level of thiol reactivity in the insulin receptor alpha subunit that was reversed following NAC removal. The oligomeric structure of the insulin receptor was not affected by GSH or NAC treatment. Of interest, the enhancement in reactivity of the insulin receptor alpha-subunit thiols with GSH or NAC had little impact on insulin binding but selectively increased insulin-stimulated change in insulin signal transduction. Progress is being made in the identification of the reactive receptor thiol group(s). We plan to assess thiol reactivity of insulin receptors isolated from type 2 diabetics and aged animals before and after GSH or NAC administration.