Metabolic Signals Regulating GLUT4 Expression in vivo

项目摘要 GLUT 4是主要负责胰岛素介导的葡萄糖摄取的同种型 在哺乳动物组织中。葡萄糖稳态对GLUT 4的变化敏感 程度.因此，GLUT 4水平的调节是一个有吸引力的分子靶点， 胰岛素抵抗状态，包括糖尿病的治疗干预。一 增强GLUT 4表达的直接方法是增加 基因的转录速率。GLUT 4基因表达是转录的， 在生理状态如胰岛素缺乏和运动中调节， 很可能可以开发一种药物干预来增强Glut 4 基因转录为了达到这一目标，我们必须首先了解分子 GLUT 4基因转录调控的基础。使用转基因小鼠，我们 已经表明调节人Glut 4启动子的顺式元件位于 在转录起始位点5 ′端的895 bp内。这一地区 包含两个主要的监管域，称为域I和MEF 2 域这些元件协同作用以支持受调控的表达 GLUT 4的MEF 2结构域结合肌细胞增强因子2的同种型 结构域I结合GEF（GLUT 4），而结构域I结合MEF 2家族的转录因子。 增强因子），我们发现并克隆了一种转录激活因子 实验室MEF 2同种型和GEF在体内形成蛋白复合物;然而， 该复合物在调节基因转录中的功能尚不清楚。我们 假设组织特异性和激素和/或代谢 GLUT 4基因的调控是通过这两个调控因子进行的。 结构域及其同源结合蛋白。该提案的主要目标是 了解组织特异性的分子机制， GLUT 4基因转录的激素/代谢调节。实现这些 目标，我们提出以下具体目标：1）了解的基础上， GEF和MEF 2蛋白之间的DNA结合合作; 2）了解 GEF和MEF 2蛋白调节GLUT 4的机制 启动子; 3））确定调节转录因子的代谢信号的性质。 体内GLUT 4基因转录。初步证据表明， 在脂质代谢和/或cAMP信号转导靶向GLUT 4启动子中的功能。 完成本提案的目标将决定这些信号是如何 传来

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.