Mechanistic studies of a PPAR-g mutation that causes lipodystrophy & diabetes

描述（由申请人提供）： 虽然胰岛素抵抗是II型糖尿病的关键组成部分，但控制胰岛素敏感性的分子机制尚未完全阐明。因此，了解胰岛素抵抗的病因对于开发更好的筛查，治疗和预防目标以对抗代谢紊乱的日益增长的威胁具有非常重要的意义。过氧化物酶体增殖物激活受体γ（PPARg）作为噻唑烷二酮类药物的靶点参与胰岛素信号传导途径，噻唑烷二酮类药物最近因其胰岛素增敏作用而用于治疗胰岛素抵抗性疾病。PPARg是一种配体激活的核受体，具有良好表征的结构，其结合PPAR反应元件并通过募集辅激活子和/或辅阻遏子来调节靶基因的转录。虽然许多PPARg调节基因已被确定，确切的一套PPARg靶基因介导改善胰岛素敏感性在体内很大程度上是未知的。该项目的目标是通过研究一种独特的、最近发现的PPARg突变来阐明这一问题，这种突变导致家族性部分脂肪代谢障碍（FPLD），这是一种极端的II型糖尿病。该项目将利用这种突变的特殊性质，在受体的DNA结合结构域中产生保守的单一变化（E157 D）。我们的初步数据表明，这种突变改变了受体的DNA序列识别特异性，导致几种已知PPARg靶基因的转录模式明显不同。这些发现导致了一个假设，该假设构成了这一提议的基础：E157 D PPARg通过关键代谢基因的失调引起糖尿病。有两个具体目标：1）表征E157 D突变对一组已知PPARg靶基因的DNA结合和转录激活的影响，和2）鉴定由E157 D PPARg错误调节的基因的全局集合。DNA结合和转录活性的标准体外技术将用于比较突变型和野生型PPARg功能。将产生表达野生型和突变型PPARg的人细胞系，并将使用基因表达的微阵列分析以及所选基因的染色质免疫沉淀分析来鉴定由E157 D PPARg错误调节的基因。 本案无关这项研究的结果将确定以前没有的基因或基因组 被认为与代谢疾病如脂肪营养不良，特别是糖尿病的病因学有关。这些知识可能会促进糖尿病和其他代谢性疾病的筛查、治疗和预防。

DESCRIPTION (provided by applicant): Although insulin resistance is a key component of type II diabetes, the molecular mechanisms controlling insulin sensitivity have not been fully elucidated. Understanding the etiology of insulin resistance will therefore be of tremendous importance for developing better screening, treatment and prevention targets to combat the rising threat of metabolic disorders. Peroxisome proliferator-activated receptor gamma (PPARg) has been implicated in the insulin signaling pathway as the target of thiazolidinediones, drugs that have recently been employed in the management of insulin-resistant disorders for their insulin-sensitizing effects. PPARg is a ligand-activated nuclear receptor with a well-characterized structure that binds PPAR response elements and regulates transcription of target genes by recruiting coactivators and/or corepressors. Although many PPARg-regulated genes have been identified, the exact set of PPARg target genes that mediate improvements in insulin sensitivity in vivo is largely unknown. The goal of this project is to shed light on this issue by studying a unique, recently discovered PPARg mutation that causes familial partial lipodystrophy (FPLD), an extreme form of type II diabetes. This project will take advantage of the particular properties of this mutation, which makes a conservative single change (E157D) in the DNA binding domain of the receptor. Our preliminary data show that this mutation alters the DNA sequence recognition specificity of the receptor, resulting in a distinctly different pattern of transcription of several known PPARg target genes. These findings led to the hypothesis that forms the basis for this proposal: the E157D PPARg causes diabetes through misregulation of key metabolic genes. There are two specific aims: 1) Characterize the effects of the E157D mutation on DNA binding and transcriptional activation of a set of known PPARg target genes, and 2) Identify the global set of genes that are misregulated by E157D PPARg. Standard in vitro techniques for DNA binding and transcriptional activity will be used to compare mutant and wild type PPARg function. Human cell lines expressing wild-type and mutant PPARg will be generated, and microarray analysis of gene expression as well as chromatin immunoprecipitation analysis of selected genes will be used to identify genes misregulated by E157D PPARg. RELEVANCE. Results from this study will identify genes or sets of genes that were not previously recognized as being involved in the etiology of metabolic diseases such as lipodystrophy and in particular diabetes. This knowledge may advance possibilities for screening, treatment and prevention of diabetes and other metabolic diseases.