Role of a novel CREB regulator in hepatic gluconeogenesis

描述（由申请方提供）：在早期禁食期间，循环胰高血糖素的增加部分通过PKA介导的磷酸化和转录因子CREB的激活刺激促胰腺炎程序。CREB共激活因子CRTC2已被证明在CREB诱导的转录激活中起重要的相互作用伴侣的作用。然而，CRTC2选择性激活CREB靶基因的分子机制仍不清楚。在CREB相关蛋白的无偏分析中，蛋白质精氨酸甲基转移酶5（PRMT5）被鉴定为CREB的推定相互作用蛋白。初步结果表明，PRMT5的过表达增加CREB活性，CRTC2的共表达进一步增加这些作用，表明PRMT5作为共激活剂发挥作用。该研究旨在确定PRMT5是否通过CREB或其共激活因子的精氨酸甲基化来调节CREB介导的肝细胞致瘤基因激活。在具体目标1中，将探索PRMT5在甲基化CREB和调节CREB与CRTC2或CBP之间的相互作用中的作用。将鉴定经历甲基化的CREB精氨酸残基。在具体的目标2中，PRMT 5在介导胰高血糖素对CREB调节的肝细胞生成程序的作用中的作用将通过PRMT 5在肝细胞中的过表达或消耗来确定。将揭示PRMT5响应胰高血糖素而募集至CREB结合的促血管生成启动子。精氨酸甲基化在CREB介导的转录中的重要性将被探讨。在具体目标3中，将评估PRMT 5在调节空腹葡萄糖产生中的作用。将在胰岛素抵抗条件下测试PRMT 5在促进高血糖症中的潜在作用。总的来说，拟议的研究将提供如何在禁食期间调节肝脏再生的见解。空腹高血糖症在胰岛素抵抗患者中很常见，部分原因是肝脏新生血管的上调。因此，这些结果可能会导致新的分子靶点，用于开发新的II型糖尿病治疗方法。 公共卫生相关性：II型糖尿病患者表现出胰岛素抵抗，这是一种以肝脏中血糖产生增加和肌肉葡萄糖摄取减少为特征的病症。胰岛素抵抗患者的空腹血糖水平升高，部分原因是肝脏新生血管的上调。了解糖尿病新生调控的分子机制可能会为II型糖尿病的治疗干预带来新的靶点。

DESCRIPTION (provided by applicant): During early fasting, increases in circulating pancreatic glucagon stimulate the gluconeogenic program in part via PKA-mediated phosphorylation and activation of the transcription factor CREB. The CREB coactivator, CRTC2, has been shown to function as an essential interacting partner in CREB-induced transcription activation. However, the molecular mechanisms by which CRTC2 selectively activates CREB target genes remain unclear. In an unbiased analysis of CREB- associated proteins, the protein arginine methyltransferase 5 (PRMT5) was identified as a putative interacting protein of CREB. Preliminary results indicate that overexpression of PRMT5 increases CREB activity and co-expression of CRTC2 further increases these effects, suggesting that PRMT5 functions as a coactivator. The proposed research is to determine whether PRMT5 modulates CREB-mediated gluconeogenic gene activation through arginine methylation of CREB or its coactivators in hepatic cells. In specific aim 1, the role of PRMT5 in methylating CREB and modulating the interaction between CREB and CRTC2 or CBP will be explored. CREB arginine residues that undergo methylation will be identified. In specific aim 2, the role of PRMT5 in mediating glucagon effects on the CREB-regulated gluconeogenic program will be determined by overexpression or depletion of PRMT5 in hepatocytes. The recruitment of PRMT5 to CREB-bound gluconeogenic promoters in response to glucagon will be revealed. The importance of arginine methylation in CREB-mediated transcription will be explored. In specific aim 3, the role of PRMT5 in regulating fasting glucose production will be evaluated. The potential effects of PRMT5 in promoting hyperglycemia will be tested under insulin resistance conditions. Collectively, the proposed studies will provide insight of how hepatic gluconeogenesis is regulated during fasting. Fasting hyperglycemia is common in insulin resistance patients in part due to up-regulation of hepatic gluconeogenesis. Thus, the results may lead to new molecular targets for the development of new therapeutic treatment of type II diabetes. PUBLIC HEALTH RELEVANCE: Type II diabetic patients exhibit insulin resistance, a condition characterized by increased blood glucose production in the liver and reduced glucose uptake by muscle. Fasting blood glucose levels are increased in insulin resistant patients in part due to up-regulation of hepatic gluconeogenesis. Understanding the molecular mechanism by which gluconeogenesis is regulated may lead to new targets for therapeutic intervention in type II diabetes.