ADAPTIVE REGULATION IN 3T3-L1 ADIPOCYTES

在过去的十年里，已经取得了重大进展， 我们对葡萄糖转运过程的理解， 葡萄糖代谢的一个步骤。 这期间最重要的两个发现 期包括易位机制， 胰岛素刺激的葡萄糖转运和多种 同种型。 代谢的分解代谢物抑制（适应性调节） 在原核生物中被广泛研究，被认为是一种重要的， 全球监管体系。 尽管如此，真核生物的营养控制 直到最近才进行调查，很少有研究关注 专门作用于葡萄糖转运蛋白。 用3 T3-L1脂肪细胞 线作为脂肪的模型，我们将探索调节 组成型葡萄糖转运蛋白1。本提案的目的是 确定运输受环境变化调节的机制， 葡萄糖利用率 为实现这一目标， 遵循具体目标。 首先，我们将描述增强的'基础' 运输活动作为葡萄糖饥饿的函数。 我们将测试 假设活性增强是由于GLUT 1蛋白升高， 在翻译水平上进行调节。 其次，我们将定义 饥饿诱导的运输下调机制。 我们将测试 假设葡萄糖抑制转运活动， 使用代谢抑制剂的蛋白质合成独立机制， 亚细胞分级分离和免疫检测。 最后，我们将定义 葡萄糖调节蛋白GRP 78和GLUT 1之间的关系。 这些独特的研究将检验GRP 78延缓GLUT 1的假设 当转运蛋白被不适当地糖基化时进行加工。 这将 通过分析GRP 78和GLUT 1的共沉淀， 缺糖细胞 总之，这些研究将确定 脂肪细胞所特有的，其可在体内调节组成性 在循环葡萄糖的波动的响应运输。

Within the last ten years, significant progress has been made which extends our understanding of the glucose transport process, often the rate-limiting step in glucose metabolism. The two most important discoveries during this period include the translocation mechanism which underlies insulin-stimulated glucose transport and the identification of multiple isoforms. Catabolite repression of metabolism (adaptive regulation) has been widely studied in procaryotes and is recognized as an important and global regulatory system. Despite this, nutrient control in eucaryotes has been under investigation only recently with few studies focusing exclusively on the glucose transporter. With the 3T3-Ll adipocyte cell line as a model for adipose, we will explore the regulation of the constitutive glucose transporter, GLUT 1. The objective of this proposal is to define the mechanisms by which transport is regulated by changes in glucose availability. This objective will be met by addressing the following Specific Aims. First, we will characterize the enhanced 'basal' transport activity as a function of glucose starvation. We will test the hypothesis that enhanced activity is due to elevated GLUT 1 protein, regulated at the translational level. Secondly, we will define the mechanism of down-regulation of starvation-induced transport. We will test the hypothesis that glucose represses transport activity by a protein-synthesis independent mechanism using metabolic inhibitors, subcellular fractionation, and immunodetection. Finally, we will define the relationship between the glucose-regulated protein, GRP 78, and GLUT 1. These unique studies will test the hypothesis that GRP 78 retards GLUT 1 processing when the transporter is inappropriately glycosylated. This will be accomplished by analyzing co-precipitation of GRP 78 and GLUT 1 in glucose-deprived cells. Together, these studies will define the mechanisms unique to adipocytes which may act in vivo to regulate constitutive transport in response to fluctuations in circulating glucose.