Regulation of Hepatic Gluconeogenesis by the CREB:TORC2 Pathway

CREB:TORC2 通路对肝糖异生的调节

• 批准号: 8036780
• 负责人: MARC R MONTMINY
• 金额: $ 12.58万
• 依托单位: SALK INSTITUTE FOR BIOLOGICAL STUDIES
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-07 至 2011-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8036780
• 关键词: 14-3-3 Proteins; Acetylation; Address; Adult; Affect; Amino Acids; Attenuated; Binding; Blood Glucose; CREB1 gene; Cell Nucleus; Chemicals; Complex; Cytoplasm; Deacetylase; Deacetylation; Diabetes Mellitus; EP300 gene; Enzymes; Equilibrium; Exhibits; Fasting; Gene Expression; Genes; Genetic; Glucagon; Glucose; Hepatic; Histones; Hyperglycemia; Individual; Insulin; Insulin Resistance; Ketone Bodies; Lead; Liver; Mediating; Metabolism; Methylation; Molecular Target; Monitor; Muscle; Mutation; Non-Insulin-Dependent Diabetes Mellitus; Nuclear Translocation; Pancreas; Pancreatic Hormones; Pathway interactions; Patients; Phase; Phosphorylation; Phosphorylation Site; Phosphotransferases; Process; Production; Proteins; Proteolysis; RNA Interference; Regulation; Regulatory Pathway; Role; Signal Pathway; Signal Transduction; Site; Skeletal Muscle; Testing; Tissues; Transferase; United States; Up-Regulation; blood glucose regulation; diabetic patient; feeding; forkhead protein; glucose output; glucose production; glucose uptake; hepatic gluconeogenesis; improved; insight; mutant; programs; promoter; public health relevance; response; salt-inducible kinase; therapeutic development

DESCRIPTION (provided by applicant): During fasting, elevations in circulating pancreatic glucagon promote hepatic glucose output through induction of the gluconeogenic program by the CREB coactivator TORC2. Sequestered in the cytoplasm during feeding, TORC2 translocates to the nucleus in response to fasting signals, where it triggers gluconeogenic gene expression in concert with the Forkhead transcription factor FOXO1. Preliminary studies indicate that TORC2 is transiently activated through P300-dependent acetylation during early fasting, when it stimulates the gluconeogenic program via an association with a histone methyl-transferase complex. TORC2 is silenced through SIRT1-mediated deacetylation during prolonged fasting, when FOXO1 is reciprocally activated. Three Aims are proposed: In Aim I, the role of P300 in augmenting TORC2 activity through acetylation during early fasting will be determined. Acetylation sites in TORC2 will be identified, and the importance of P300 in catalyzing TORC2 acetylation will be evaluated. The role of the NAD+ dependent deacetylase SIRT1 in silencing TORC2 through deacetylation during prolonged fasting will also be explored. In Aim II, the importance of the Ser/Thr kinase SIK2 in modulating hepatic TORC2 activity through phosphorylation of P300 will be evaluated. SIK2 phosphorylation sites in P300 will be identified, and their role in disrupting the P300:TORC2 interaction and thereby reducing TORC2 acetylation will be analyzed. In Aim III, the role of a TORC2 associated histone methyl-transferase (HMT) complex in mediating induction of the gluconeogenic program during fasting will be determined. The importance of TORC2 for recruitment of HMT complexes and for histone methylation over gluconeogenic promoters during fasting will be determined, by depletion of TORC2 or HMT components, and by expression of HMT interaction-defective mutant TORC2 proteins. The potential role of HMTs in modulating gluconeogenic gene expression by methylating TORC2 will also be evaluated through identification and mutation of relevant sites in TORC2. Taken together, the proposed studies will provide insight into regulatory pathways that modulate fasting metabolism through a coactivator that is required for glucose balance and that contributes to hyperglycemia in diabetes. The results may lead to the identification of new molecular targets for the development of therapeutic compounds that improve glucose control in insulin resistant individuals. PUBLIC HEALTH RELEVANCE: The pancreatic hormone glucagon maintains circulating glucose levels during fasting by turning on a genetic switch, called TORC2, that increases glucose production in the liver; insulin protects against abnormal elevations in blood glucose during feeding by turning off the TORC2 switch. Glucagon and insulin exert these opposing effects on the TORC2 switch through a group of enzymes that cause different chemical changes in the TORC2 protein. By characterizing these chemical changes in TORC2 and understanding how they modify the ability for this switch to trigger glucose production, our studies may lead to new therapies for the treatment of diabetic patients.

描述（由申请人提供）：禁食期间，循环胰高血糖素的升高通过 CREB ​​共激活剂 TORC2 诱导糖异生程序来促进肝葡萄糖输出。 TORC2 在进食过程中被隔离在细胞质中，响应禁食信号易位到细胞核，在细胞核中与 Forkhead 转录因子 FOXO1 协同触发糖异生基因表达。初步研究表明，TORC2 在早期禁食期间通过 P300 依赖性乙酰化被短暂激活，此时它通过与组蛋白甲基转移酶复合物的关联刺激糖异生程序。在长时间禁食期间，当 FOXO1 相互激活时，TORC2 通过 SIRT1 介导的脱乙酰作用而被沉默。提出了三个目标： 在目标 I 中，将确定 P300 在早期禁食期间通过乙酰化增强 TORC2 活性的作用。将鉴定 TORC2 中的乙酰化位点，并评估 P300 在催化 TORC2 乙酰化中的重要性。还将探讨 NAD+ 依赖性脱乙酰酶 SIRT1 在长时间禁食期间通过脱乙酰作用沉默 TORC2 的作用。在目标 II 中，将评估 Ser/Thr 激酶 SIK2 通过 P300 磷酸化调节肝 TORC2 活性的重要性。将鉴定 P300 中的 SIK2 磷酸化位点，并分析它们在破坏 P300:TORC2 相互作用并从而减少 TORC2 乙酰化中的作用。在目标 III 中，将确定 TORC2 相关组蛋白甲基转移酶 (HMT) 复合物在介导禁食期间糖异生程序诱导中的作用。 TORC2 对于 HMT 复合物的募集和禁食期间糖异生启动子上的组蛋白甲基化的重要性将通过 TORC2 或 HMT 成分的耗尽以及 HMT 相互作用缺陷型突变 TORC2 蛋白的表达来确定。 HMT 在通过 TORC2 甲基化调节糖异生基因表达中的潜在作用也将通过 TORC2 中相关位点的识别和突变来评估。总而言之，拟议的研究将深入了解通过辅激活剂调节空腹代谢的调节途径，辅激活剂是葡萄糖平衡所需的，并且会导致糖尿病的高血糖。这些结果可能有助于确定新的分子靶标，用于开发改善胰岛素抵抗个体血糖控制的治疗化合物。公共健康相关性：胰腺激素胰高血糖素通过打开称为 TORC2 的基因开关来维持禁食期间的循环葡萄糖水平，该开关会增加肝脏中的葡萄糖产生。胰岛素通过关闭 TORC2 开关来防止进食期间血糖异常升高。胰高血糖素和胰岛素通过一组引起 TORC2 蛋白不同化学变化的酶对 TORC2 开关发挥这些相反的作用。通过表征 TORC2 中的这些化学变化并了解它们如何改变这种开关触发葡萄糖产生的能力，我们的研究可能会带来治疗糖尿病患者的新疗法。