Glucocorticoid Receptor Coregulators and Insulin Sensitivity

糖皮质激素受体共调节剂和胰岛素敏感性

• 批准号: 10521257
• 负责人: Jen-Chywan Wang
• 金额: $ 39.75万
• 依托单位: UNIVERSITY OF CALIFORNIA BERKELEY
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-12-10 至 2024-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10521257
• 关键词: Adipose tissue; Affect; Attenuated; Binding; Chronic; Complex; Docking; Equilibrium; Extracellular Signal Regulated Kinases; Family; Genes; Genetic Transcription; Genomics; Glucocorticoid Receptor; Glucocorticoids; Glucose; Glucose Clamp; Hepatic; Hyperinsulinism; Insulin Resistance; Knowledge; Liver; Lysine; MAPK3 gene; Metabolic; Metabolic Diseases; Mitogen-Activated Protein Kinases; Modeling; Mus; Mutation; Non-Insulin-Dependent Diabetes Mellitus; Peripheral; Phenotype; Phosphoric Monoester Hydrolases; Proteins; Regulation; Response Elements; Risk; Role; Signal Transduction; Site; Skeletal Muscle; Stress; Testing; Tissues; Transcription Coactivator; Transcriptional Activation; experimental study; gene repression; genetic corepressor; glucocorticoid-induced orphan receptor; glucose production; hepatic gluconeogenesis; insight; insulin regulation; insulin sensitivity; insulin signaling; knock-down; novel; novel therapeutics; overexpression; recruit; resistance gene; transcription factor; transcriptome sequencing

Chronic Glucocorticoids (GC) exposure has long been associated with metabolic disorders, including insulin resistance. GC convey their signals through an intracellular glucocorticoid receptor (GR), a transcription factor that binds to genomic glucocorticoid response elements and recruits specific transcriptional coregulators to modulate the transcription of its target genes. Ehmt2 (a.k.a. G9a) is a GR coregulator that acts as a coactivator or corepressor. Our preliminary studies found that reducing Ehmt2 in liver exacerbated GC-induced insulin resistance. Intriguingly, this is caused by the coactivation but corepression function of Ehmt2, because mice carrying a mutation at the lysine 182 automethylation site of Ehmt2 (Ehmt2K182R/K182R mice) which abolishes the coactivation but not corepression function of Ehmt2, also had exacerbated GC-induced insulin resistance. RNA sequencing experiment identified Dusp4 (a.k.a. MKP-2) as an Ehmt2 coactivation dependent GR-activated gene, which when overexpressed in liver, attenuated GC-induced insulin resistance. Thus, we hypothesize a novel GR-Ehmt2-Dusp4 axis that counteracts GR-induced insulin resistant genes to control the extent of insulin resistance. In Aim 1, we will examine the effect of losing the Ehmt2 coactivation on the ability of GC to modulate insulin signaling. Hyperinsulinemic-euglycemic clamp will be used to examine Ehmt2’s role in regulating hepatic glucose production and peripheral glucose utilization. We will also test whether increasing Ehmt2 coactivation capacity by elevating its automethylation reverses GC-induced insulin resistance. In Aim 2, we will reduce hepatic Dusp4 expression to further validate its role in GC-induced insulin resistance. We found that MAP kinase ERK1/2 activity was increased in GC-treated Ehmt2K182R/K182R mouse liver. As Dusp4 is a MAP Kinase phosphatase, we will test whether Dusp4 is responsible for GC-induced ERK1/2 in Ehmt2K182R/K182R mouse liver and whether ERK1/2 is a target of Dusp4 in the regulation of GC-induced insulin resistance. Notably, Ehmt2 forms a heterodimer with Ehmt1 (a.k.a. GLP) and automethylation of Ehmt2 and Ehmt1 create a docking site for a transcriptional coactivator Cbx3 (a.k.a. HP1g). Our preliminary study found that reducing Ehmt1 expression had worsened GC-induced insulin resistance (similar to hepatic Ehmt2 knockdown and Ehmt2K182R/K182R mice). In Aim 3, we will examine whether automethylation of Ehmt1 results in similar phenotypes with hmt2K182R/K182R mice. We will also investigate whether hepatic Cbx3 knockdown exacerbates GC-induced insulin resistance. Finally, we will analyze the mechanism underlying Dusp4 gene transcription by GR and Ehmt2-Ehmt1-Cbx3 coactivator complex. The dogma for GC-induced insulin resistance is: GR activates genes promoting insulin resistance and represses genes promoting insulin sensitivity. In this proposal, we provide a revolutionary concept in which the extent of GC-induced insulin resistance is controlled by the balance of GR-activated genes that promoting insulin sensitivity or insulin resistance. Exploring the mechanism underlying this novel GR-Ehmt2-Dusp4 axis shall significantly impact on our understanding of the metabolic functions of GC.

长期以来，长期接触糖皮质激素(GC)与代谢紊乱有关，包括胰岛素抵抗。GC通过细胞内糖皮质激素受体(GR)传递信号，GR是一种转录因子，与基因组糖皮质激素反应元件结合，并招募特定的转录辅助调节因子来调节其靶基因的转录。Ehmt2(也称为G9a)是一种GR辅调节因子，起辅激活子或辅抑制子的作用。我们的初步研究发现，降低肝脏中的Ehmt2会加剧GC诱导的胰岛素抵抗。有趣的是，这是由Ehmt2的共激活但共抑制功能引起的，因为携带Ehmt2赖氨酸182自甲基化突变的小鼠(Ehmt2K182R/K182R小鼠)取消了Ehmt2的共激活但不是共抑制功能，也加剧了GC诱导的胰岛素抵抗。核糖核酸 测序结果表明，Dusp4(又称Dusp4)MKP-2)作为Ehmt2共激活依赖的GR激活基因，当其在肝脏过表达时，可减轻GC诱导的胰岛素抵抗。因此，我们假设了一个新的GR-Ehmt2-Dusp4轴，它可以抵消GR诱导的胰岛素抵抗基因，以控制胰岛素抵抗的程度。在目标1中，我们将研究失去Ehmt2共激活对GC调节胰岛素信号的能力的影响。高胰岛素-正常血糖钳夹实验将用于研究Ehmt2在调节肝脏葡萄糖生成和外周葡萄糖利用中的作用。我们还将测试通过提高Ehmt2的自甲基化来增加Ehmt2的共激活能力是否逆转了GC诱导的胰岛素抵抗。在目标2中，我们将降低肝脏Dusp4的表达，以进一步验证其在GC诱导的胰岛素抵抗中的作用。我们发现了MAP的激活剂 经GC处理的Ehmt2K182R/K182R小鼠肝脏ERK1/2活性增强。由于Dusp4是一种MAP激酶磷酸酶，我们将检测Dusp4是否与GC诱导的Ehmt2K182R/K182R小鼠肝脏ERK1/2有关，以及ERK1/2是否是Dusp4调节GC诱导的胰岛素抵抗的靶点。值得注意的是，Ehmt2与Ehmt1形成杂二聚体。GLP)和Ehmt2和Ehmt1的自动甲基化为转录辅活化子Cbx3(又名。HP1g)。我们的初步研究发现，减少Ehmt1的表达加剧了GC诱导的胰岛素抵抗(类似于肝脏Ehmt2基因敲除和Ehmt2K182R/K182R小鼠)。在目标3中，我们将检查Ehmt1的自甲基化是否导致与hmt2K182R/K182R类似的表型 老鼠。我们还将研究肝脏Cbx3基因敲除是否加剧了GC诱导的胰岛素抵抗。最后，我们将分析GR和Ehmt2-Ehmt1-Cbx3共激活复合体转录Dusp4基因的机制。GC诱导的胰岛素抵抗的教条是：GR激活促进胰岛素抵抗的基因，抑制促进胰岛素敏感性的基因。在这个方案中，我们提供了一个革命性的概念，即GC诱导的胰岛素抵抗的程度由促进胰岛素敏感性或胰岛素抵抗的GR激活基因的平衡控制。探索这种新的GR-Ehmt2-Dusp4轴的机制将对我们理解GC的代谢功能产生重大影响。