THE ROLE OF TRANSCRIPTION FACTORS IN LIVER METABOLISM

转录因子在肝脏代谢中的作用

• 批准号: 7215488
• 负责人: KLAUS H KAESTNER
• 金额: $ 31.42万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7215488
• 关键词: biological models; biological signal transduction; cAMP response element binding protein; cell differentiation; developmental genetics; diabetes mellitus; functional /structural genomics; gluconeogenesis; histogenesis; laboratory mouse; liver cells; liver metabolism; model design /development; protein kinase A; protein structure function; transcription factor

Diabetes mellitus is a significant health problem, affecting over 18 million people in the United States alone. Mutations in several hepatic nuclear factors have been linked to early onset non-insulin dependent diabetes mellitus (MODY), underscoring the importance of the hepatic transcription factors for glucose homeostasis. In the previous grant cycle, we have employed tissue-specific gene ablation to demonstrate the essential function of Foxa2 (previously known as HNF3(3) in the integration of the transcriptional response of the hepatocyte to fasting. In addition, Foxa2 has been proposed as a major mediator of insulin signaling in hepatocytes. We propose the following three Aims: In Aim 1, which is the direct result of the interactions within the PO1 with Dr. Birnbaum, we will test the hypothesis that Foxa2 is the major mediator of insulin signaling via AKT2 using genetic means. We will derive mice which are deficient for both AKT2 and Foxa2 in hepatocytes to test if Foxa2 is indeed required to establish the AKT2 mutant phenotype. In Aim 2, we will collaborate with Dr. Ahima to investigate the combined role of Foxa1 AND Foxa2 in hepatic metabolism. This aim is based on our discovery that Foxal and Foxa2 act jointly to enable the hepatogenic program during fetal devlopment. We hypothesize that the two genes also cooperate in transcription in the adult hepatocyte. We will use simulatenous conditional gene ablatation for Foxa1 and Foxa2 combined with physiological and genomics approaches to test our hypothesis that the two genes open chromatin to enable binding of hormone-dependent transcription factors like CREB and GR. In Aim 3, we will address a recent controversy concerning the regulation of hepatic gluconeogenesis by cAMP. Currently, two conflicting models exist regarding the regulation of the transcription factor CREB in hepatocyte. The first proposes that PKA-dependent phosphorylation of CREB is required for recruitment of the co-activator CBP/p300 and subsequent activation of target genes, while the second invokes PKA-dependent translocation of the novel co-activator TORC2 from the cytoplasm to the nucleus as the central regulator of CREB-dependent transcription. We will address the relative importance of both pathways in hepatic glucose homeostasis by genetic means. We will develop mouse models carrying a Ser/Ala mutation in the PKA-phosphorylation site of CREB or a hepatocyte-specific ablation of TORC2, and analyze the consequences to glucose metabolism both in vivo and in isolated hepatocytes. Together, these studies will further our understanding of the transcriptional regulation of hepatic metabolism and in insulin action.

糖尿病是一个严重的健康问题，仅在美国就有超过 1800 万人受到影响。 几种肝核因子的突变与早发性非胰岛素依赖型糖尿病有关 mellitus (MODY)，强调了肝转录因子对于葡萄糖稳态的重要性。 在上一个资助周期中，我们采用了组织特异性基因消融来证明必要的 Foxa2（以前称为 HNF3(3)）在整合转录反应中的功能 肝细胞要禁食。此外，Foxa2 已被提议作为胰岛素信号传导的主要介质 肝细胞。我们提出以下三个目标： 在目标 1 中，这是 PO1 与 Birnbaum 博士互动的直接结果，我们将测试 假设 Foxa2 是使用遗传手段通过 AKT2 进行胰岛素信号传导的主要介质。我们将 衍生出肝细胞中同时缺乏 AKT2 和 Foxa2 的小鼠来测试 Foxa2 是否确实需要 建立 AKT2 突变表型。在目标 2 中，我们将与 Ahima 博士合作调查 Foxa1 和 Foxa2 在肝脏代谢中的联合作用。这一目标是基于我们的发现，Foxal 和 Foxa2 共同作用以在胎儿发育过程中启用肝源程序。我们假设 两个基因也在成体肝细胞中协同转录。我们将使用模拟条件基因 Foxa1 和 Foxa2 的消融结合生理学和基因组学方法来测试我们的 假设这两个基因打开染色质以实现激素依赖性转录因子的结合 比如 CREB ​​和 GR。在目标 3 中，我们将解决最近有关肝脏调节的争议。 cAMP 的糖异生作用。目前，在监管方面存在两种相互冲突的模式 肝细胞中的转录因子CREB。第一个提出 CREB ​​的 PKA 依赖性磷酸化是 需要招募共激活剂 CBP/p300 并随后激活靶基因，而 第二个激活新型共激活因子 TORC2 的 PKA 依赖性易位，从细胞质转移到细胞质。 细胞核作为 CREB ​​依赖性转录的中央调节器。我们将讨论相对重要性 通过遗传手段调节肝葡萄糖稳态的两条途径。我们将开发小鼠模型 CREB ​​的 PKA 磷酸化位点携带 Ser/Ala 突变或肝细胞特异性消融 TORC2，并分析体内和离体肝细胞对葡萄糖代谢的影响。 总之，这些研究将进一步加深我们对肝脏代谢转录调控的理解 和胰岛素作用。