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: 10317109
• 负责人: Jen-Chywan Wang
• 金额: $ 39.47万
• 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/10317109
• 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; 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; genetic corepressor; glucocorticoid receptor alpha; 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，糖皮质激素（GC）暴露与代谢紊乱（包括胰岛素抵抗）有关。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，并招募特异性转录辅助调节因子来调节其靶基因的转录。Ehmt 2（又名：G9 a）是GR辅调节因子，充当辅激活因子或辅抑制因子。我们的初步研究发现，降低肝脏Ehmt 2会加重GC诱导的胰岛素抵抗。有趣的是，这是由Ehmt 2的共激活但共抑制功能引起的，因为在Ehmt 2的赖氨酸182自甲基化位点携带突变的小鼠（Ehmt 2K 182 R/K182 R小鼠）也加剧了GC诱导的胰岛素抵抗，该突变消除了Ehmt 2的共激活但不具有共抑制功能。RNA 测序实验鉴定了Dusp 4（a.k.a. MKP-2）作为Ehmt 2共激活依赖性GR激活基因，当在肝脏中过表达时，减轻GC诱导的胰岛素抵抗。因此，我们假设一个新的GR-Ehmt 2-Dusp 4轴，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Ehmt 2共激活对GC调节胰岛素信号传导能力的影响。高胰岛素-正葡萄糖钳夹将用于检查Ehmt 2在调节肝脏葡萄糖产生和外周葡萄糖利用中的作用。我们还将测试是否增加Ehmt 2共激活能力，通过提高其自身甲基化逆转GC诱导的胰岛素抵抗。在目标2中，我们将减少肝脏Dusp 4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MAP激酶 在GC处理的Ehmt 2K 182 R/K182 R小鼠肝脏中，ERK 1/2活性增加。由于Dusp 4是MAP激酶磷酸酶，我们将测试Dusp 4是否负责Ehmt 2K 182 R/K182 R小鼠肝脏中GC诱导的ERK 1/2，以及ERK 1/2是否是Dusp 4调节GC诱导的胰岛素抵抗的靶标。值得注意的是，Ehmt 2与Ehmt 1形成异二聚体（a.k.a. GLP）和Ehmt 2和Ehmt 1的自甲基化产生转录共激活因子Cbx 3（a.k.a. HP1g）。我们的初步研究发现，降低Ehmt 1的表达恶化了GC诱导的胰岛素抵抗（类似于肝脏Ehmt 2敲低和Ehmt 2K 182 R/K182 R小鼠）。在目标3中，我们将研究Ehmt 1的自甲基化是否导致与hmt 2K 182 R/K182 R相似的表型 小鼠我们还将研究肝Cbx 3敲低是否会加重GC诱导的胰岛素抵抗。最后，我们将分析GR和Ehmt 2-Ehmt 1-Cbx 3共激活因子复合物转录Dusp 4基因的机制。GC诱导的胰岛素抵抗的原理是：GR激活促进胰岛素抵抗的基因并抑制促进胰岛素敏感性的基因。在这个建议中，我们提供了一个革命性的概念，其中GC诱导的胰岛素抵抗的程度是由GR激活的促进胰岛素敏感性或胰岛素抵抗的基因的平衡控制的。探索这种新的GR-Ehmt 2-Dusp 4轴的机制将对我们理解GC的代谢功能产生重大影响。