Metabolic Signals Regulating GLUT4 Expression in vivo

项目摘要 GLUT4是胰岛素介导的葡萄糖摄取的主要异构体 在哺乳动物组织中。葡萄糖稳态对GLUT4的变化很敏感 级别。因此，GLUT4水平的调节是一个有吸引力的分子靶点 胰岛素抵抗状态的治疗干预，包括糖尿病。一个 增强GLUT4表达的直接方法是增加GLUT4的 基因的转录速率。GLUT4基因的表达是转录的 在胰岛素缺乏和运动等生理状态下调节，而且它是 可能可以开发一种药物干预来增强GLUT4 基因转录。为了达到这一目标，我们必须首先了解分子 GLUT4基因转录调控的基础。使用转基因小鼠，我们 已经证明调节人类GLUT4启动子的顺式元件存在于 在距转录起始点5‘端895bp的范围内。这一地区 包含两个主要的监管领域，称为领域I和MEF2 域。这些元件协同工作以支持受调控的表达 GLUT4。MEF2结构域结合肌细胞增强因子2的异构体 (MEF2)转录因子家族，而结构域I结合环境基金(GLUT4 增强子因子)是一种转录激活子，在我们的 实验室。MEF2亚型与全球环境基金在体内形成蛋白质复合体；然而， 该复合体调节基因转录的功能尚不清楚。我们 假设组织特异性以及荷尔蒙和/或代谢 GLUT4基因的调控是通过这两种调控方式进行的 结构域及其同源结合蛋白。这项提议的主要目标是 为了了解组织特异性和致病性的分子机制 GLUT4基因转录的激素/代谢调节要实现这些目标 目标，我们提出以下具体目标：1)了解 全球环境基金与MEF2蛋白在DNA结合中的协同作用；2)理解 全球环境基金和MEF2蛋白调节GLUT4的机制 启动子；3)确定调节代谢信号的性质(S GLUT4基因在体内转录。初步证据表明， 在脂质代谢和/或cAMP信号转导靶点GLUT4中发挥作用。 这项提案目标的完成将决定这些信号是如何 已发送。

Project Summary GLUT4 is the isoform principally responsible for insulin-mediated glucose uptake in mammalian tissues. Glucose homeostasis is sensitive to changes in GLUT4 levels. Modulation of GLUT4 levels is therefore an attractive molecular target for therapeutic intervention in insulin-resistant states, including diabetes mellitus. A straightforward approach to enhance GLUT4 expression is to increase the transcription rate of the gene. GLUT4 gene expression is transcriptionally regulated in physiologic states such as insulin-deficiency and exercise, and it is likely that a pharmacological intervention can be developed to enhance Glut4 gene transcription. To reach this goal, we must first understand the molecular basis for transcriptional regulation of the GLUT4 gene. Using transgenic mice, we have shown that cis-elements regulating the human Glut4 promoter are located within 895 bp immediately 5' of the transcription initiation site. This region contains two major regulatory domains, referred to as Domain I and the MEF2 domain. These elements function cooperatively to support regulated expression of GLUT4. The MEF2 domain binds isoforms of the Myocyte Enhancer Factor 2 (MEF2) family of transcription factors, while Domain I binds GEF (GLUT4 Enhancer Factor), a transcriptional activator identified and cloned in our laboratory. MEF2 isoforms and GEF form a protein complex in vivo; however, the function of this complex in regulating gene transcription is not known. We hypothesize that both the tissue-specific and the hormonal and/or metabolic regulation of the GLUT4 gene are carried out through these two regulatory domains and their cognate binding proteins. The primary goal of this proposal is to understand the molecular mechanisms of the tissue-specific and hormonal/metabolic regulation of GLUT4 gene transcription. To achieve these goals, we propose the following specific aims: 1) To understand the basis of cooperation between GEF and MEF2 proteins for DNA binding; 2) To understand the mechanisms by which GEF and MEF2 proteins regulate the GLUT4 promoter; 3) ) To determine the nature of the metabolic signal(s) that regulates GLUT4 gene transcription in vivo. Preliminary evidence suggests that changes in lipid metabolism and/or cAMP signaling target GLUT4 promoter function. Completion of the aims of this proposal will determine how these signals are transmitted.