C/EBP-A as a Mediator of Insulin Action in Adipocytes

描述：(摘自申请者的摘要)我的长期目标是 研究计划是确定分子机制，通过它 细胞外信号调控脂肪形成及其相关基因的表达 脂肪细胞特异性基因。C/EBPA在发展中起着重要作用 脂肪细胞与脂肪细胞中胰岛素信号的获取。给定 C/EBPA对脂肪细胞分化和代谢的重要性 了解CIEBPA转录的分子机制很重要 和活动是受监管的。我的实验室已经确定了CIEBPA的五个地点 体内的磷酸化。其中，T222和T226被糖原磷酸化 合成酶激酶3(GSK3)和胰岛素刺激这些蛋白的去磷酸化 通过使GSK3失活。在这些实验的过程中，我们 发现抑制GSK3可以阻止前脂肪细胞的分化。 与GSK3的发育效应一致与信号转导有关 通过WNT，前脂肪细胞暴露于WNT阻止了它们经历 成脂作用。基于这些发现，我们假设失活 胰岛素和Wnt介导的GSK3对脂肪细胞基因表达和成脂的影响 通过调节C/EBP的磷酸化和活性。的具体目标 这项赠款申请将用于： 1)确定磷酸化在调节C/EBPA活性中的作用 胰岛素。C/EBPA磷酸化对血管内皮生长因子表达影响的实验研究 提出了反式激活和有丝分裂的概念。磷酸化在细胞周期调控中的作用 调节依赖C/EBPA的前脂肪细胞和脂肪细胞基因的一个子集将 要下定决心。 2)确定WNTS抑制前脂肪细胞分化的机制 以及这一途径的生理学意义。实验将会发现 并研究了Wnt信号和Wnt调节蛋白的调控 在脂肪细胞发育过程中起作用。建议进行实验以确定 Wnt对C/EBPA和PPARy基因表达的抑制作用 通过b-catenin-Tcf、Myc、Gatas或Wnt是否抑制GSK3 刺激C/EBPβ的去磷酸化和失活。 了解胰岛素和Wnt如何通过GSK3和C/EBP转录传递信号 调节脂肪生成和脂肪细胞基因表达的因素将提供 对肥胖和H型糖尿病医学问题的重要洞察，两个 美国的重大健康风险。

DESCRIPTION: (Scanned from the applicant's abstract) The long term goal of my research program is to determine the molecular mechanisms by which extracellular signals regulate adipogenesis and the expression of adipocyte-specific genes. C/EBPa plays an essential role in development of adipocytes and the acquisition of insulin signaling in adipocytes. Given the importance of C/EBPa for adipocyte differentiation and metabolism, it is important to understand the molecular mechanisms by which CIEBPa transcription and activity are regulated. My laboratory has identified five sites of CIEBPa phosphorylation in vivo. Of these, T222 and T226 are phosphorylated by glycogen synthase kinase 3 (GSK3) and insulin stimulates dephosphorylation of these sites through inactivation of GSK3. During the course of these experiments, we discovered that inhibition of GSK3 blocks preadipocyte differentiation. Consistent with developmental effects of GSK3 being associated with signaling by Wnt, exposure of preadipocytes to Wnt blocked their ability to undergo adipogenesis. Based upon these findings, we hypothesize that inactivation of GSK3 by insulin and Wnt influences adipocyte gene expression and adipogenesis through regulation of C/EBP phosphorylation and activity. The SPECIFIC AIMS of this grant application are to: 1) Determine the role of phosphorylation in regulation of C/EBPa activity by insulin. Experiments to investigate effects of phosphorylation of C/EBPa on transactivation and mitosis are proposed. The role of phosphorylation in regulating a subset of C/EBPa-dependent preadipocyte and adipocyte genes will be determined. 2) Determine the mechanism by which Wnts inhibits preadipocyte differentiation and the physiological significance of this pathway. Experiments will identify and investigate the regulation of Wnt-signaling and Wnt-regulatory proteins that act in adipocyte development. Experiments are proposed to determine whether repression of C/EBPa and PPARy gene expression by Wnt is mediated through b-catenin-TCF, Myc, GATAs, or whether inhibition of GSK3 by Wnt stimulates dephosphorylation and inactivation of C/EBPbeta. Understanding how insulin and Wnt signal through GSK3 and C/EBP transcription factors to regulate adipogenesis and adipocyte gene expression will provide important insight into the medical problems of obesity and type H diabetes, two major health risks in the United States.