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

描述：（从申请人的摘要扫描）我的长期目标 研究计划是确定分子机制， 细胞外信号调节脂肪形成和 脂肪细胞特异性基因。C/EBPa在发展中起着至关重要的作用， 脂肪细胞和脂肪细胞中胰岛素信号的获得。鉴于 C/EBPa对脂肪细胞分化和代谢的重要性， 重要的是要了解CIEPa转录的分子机制， 和活动都受到监管。我的实验室已经确定了CIEBPA的五个位点 体内磷酸化。其中，T222和T226被糖原磷酸化 合成酶激酶3（GSK 3）和胰岛素刺激这些蛋白的去磷酸化， 通过GSK 3的失活位点。在这些实验中，我们 发现GSK 3的抑制阻断前脂肪细胞分化。 与GSK 3的发育效应一致， 通过Wnt，前脂肪细胞暴露于Wnt阻断了它们的能力， 脂肪生成基于这些发现，我们假设， 胰岛素和Wnt介导的GSK 3对脂肪细胞基因表达和脂肪形成的影响 通过调节C/EBP磷酸化和活性。的具体目标 此资助申请是： 1)通过以下方法确定磷酸化在C/EBPa活性调节中的作用： 胰岛素研究C/EBPa的磷酸化对细胞凋亡的影响的实验 反式激活和有丝分裂。磷酸化在 调节C/EBPa依赖性前脂肪细胞和脂肪细胞基因的子集将 被确定。 2)确定Wnts抑制前脂肪细胞分化的机制 以及这条通路的生理意义。实验将确定 并研究Wnt信号和Wnt调节蛋白的调节 在脂肪细胞发育中起作用。提出实验来确定 Wnt是否介导了C/EBPa和PPARy基因表达的抑制 通过b-连环蛋白-TCF、Myc、GATAs，或是否通过Wnt抑制GSK 3， 刺激C/EBP β的去磷酸化和失活。 了解胰岛素和Wnt如何通过GSK 3和C/EBP转录进行信号传导 调节脂肪形成和脂肪细胞基因表达的因子将提供 肥胖和H型糖尿病的医学问题的重要见解，两个 美国的主要健康风险。

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.