Regulation of Hepatic Gluconeogenesis by the CREB:TORC2 Pathway

项目总结/摘要 转录因子CREB（cAMP反应元件结合蛋白）调节代谢基因表达 对cAMP信号传导增加的反应。CREB被认为可以促进多达5000个基因的表达， 哺乳动物基因组，但CREB激活不同靶基因组的机制不同， 背景仍然不清楚。为了解决这个问题，Montminy实验室将分析CREB信号输出， 肝脏和胰岛，因为这两种组织中的CREB活性对于葡萄糖稳态是必需的。期间 禁食期间，循环胰高血糖素的增加触发肝脏中致炎基因的表达， 通过CREB通路的诱导。在进食过程中，肠内分泌细胞分泌胰高血糖素样 肽1（GLP 1），刺激胰岛素分泌，促进β细胞活力，也通过CREB- 依赖机制平衡这两个相反的CREB介导的生理过程似乎 对葡萄糖稳态至关重要CREB活性受组蛋白乙酰转移酶辅激活剂CBP刺激 和P300，以及一个cAMP调节的转录辅激活因子（CRTCs）家族，其与 CREB对cAMP的反应。在这里，不同的CRTCs和转录辅因子在调节 CREB/CRTC活性以引发组织特异性应答（即，肝脏对胰岛）进行检查。的 总的假设是CREB途径作为肝葡萄糖产生的中心调节物起作用， 胰腺胰岛素分泌。目的1将集中在CREB介导的葡萄糖生产的肝脏响应 斋戒. Montminy实验室将产生缺乏CRTC 2和CRTC 3（单独和联合）的小鼠 特别是在肝细胞中，并评估对葡萄糖输出的影响。然后，本实验将研究 转录因子FOXO 1和表观遗传调节因子BRD 4促进CRTC募集到一个亚群， 肝细胞中的禁食诱导基因。目的2将探讨CRTC 1和CRTC 2在介导细胞凋亡中的作用。 葡萄糖和GLP 1对胰岛素分泌和β细胞活力的影响。实验室将培育出缺乏 CRTC 1和CRTC 2（单独和联合）在胰岛β细胞中的特异性，并评估其作用 对胰岛素分泌和CREB靶基因选择的影响。实验室将描述β细胞的作用- 特异性转录因子NeuroD 1和cAMP调节的非编码RNA，LINC 00473， 胰腺中的CREB/CRTC信号传导。拟议的研究将揭示CREB， CRTC及其辅因子（例如，谱系特异性转录因子和表观遗传调节因子）促进 通过差异激活肝脏和胰腺中CREB靶基因的特定亚群实现葡萄糖稳态 小岛通过化学抑制剂靶向这些辅因子可以为患有以下类型的个体提供治疗益处： II型糖尿病。

Project Summary/Abstract The transcription factor CREB (cAMP response element-binding protein) regulates metabolic gene expression in response to increases in cAMP signaling. CREB is thought to promote the expression of up to 5000 genes in the mammalian genome, but mechanisms by which CREB activates different sets of target genes in different contexts remain unclear. To address this problem, the Montminy lab will analyze CREB signaling output in the liver and pancreatic islets, as CREB activity in these two tissues is essential for glucose homeostasis. During periods of fasting, increases in circulating glucagon trigger the expression of gluconeogenic genes in the liver via induction of the CREB pathway. During feeding, intestinal enteroendocrine cells secrete glucagon like peptide 1 (GLP1), which stimulates insulin secretion and promotes beta cell viability, also via a CREB- dependent mechanism. Balancing these two opposing CREB-mediated physiological processes appears critical for glucose homeostasis. CREB activity is stimulated by the histone acetyl-transferase coactivators CBP and P300, and by a family of cAMP regulated transcriptional coactivators (CRTCs), which associate with CREB in response to cAMP. Here, the roles of different CRTCs and transcriptional co-factors in modulating CREB/CRTC activity to elicit tissue-specific responses (i.e., hepatic vs. pancreatic islet) will be examined. The overall hypothesis is that the CREB pathway functions as a central regulator of hepatic glucose production and pancreatic insulin secretion. Aim 1 will focus on CREB-mediated glucose production by the liver in response to fasting. The Montminy lab will generate mice lacking CRTC2 and CRTC3 (alone and in combination) specifically in hepatocytes and assess effects on glucose output. The lab will then examine roles played by the transcription factor FOXO1 and the epigenetic regulator BRD4 in facilitating CRTC recruitment to a subset of fasting-induced genes in hepatocytes. Aim 2 will explore the role of CRTC1 and CRTC2 in mediating the effects of glucose and GLP1 on insulin secretion and beta cell viability. The lab will generate mice lacking CRTC1 and CRTC2 (alone and in combination) specifically in pancreatic islet beta cells and assess the effects on insulin secretion and CREB target gene selection. The lab will characterize roles played by the beta cell- specific transcription factor NeuroD1 and the cAMP-regulated non-coding RNA, LINC00473, in potentiating CREB/CRTC signaling in the pancreas. The proposed studies will uncover how interactions between CREB, CRTCs, and their cofactors (e.g., lineage-specific transcription factors and epigenetic regulators) promote glucose homeostasis by differentially activating specific subsets of CREB target genes in liver and pancreatic islets. Targeting these cofactors via chemical inhibitors may provide therapeutic benefit to individuals with type II diabetes.