He Bo, Cruz-Topete Diana, Oakley Robert H, Xiao Xiao, Cidlowski John A
Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA.
Division of Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Mol Cell Biol. 2015 Dec 28;36(5):714-30. doi: 10.1128/MCB.00908-15.
While in vitro studies have demonstrated that a glucocorticoid receptor (GR) splice isoform, β-isoform of human GR (hGRβ), acts as a dominant-negative inhibitor of the classic hGRα and confers glucocorticoid resistance, the in vivo function of hGRβ is poorly understood. To this end, we created an adeno-associated virus (AAV) to express hGRβ in the mouse liver under the control of the hepatocyte-specific promoter. Genome-wide expression analysis of mouse livers showed that hGRβ significantly increased the expression of numerous genes, many of which are involved in endocrine system disorders and the inflammatory response. Physiologically, hGRβ antagonized GRα's function and attenuated hepatic gluconeogenesis through downregulation of phosphoenolpyruvate carboxykinase (PEPCK) in wild-type (WT) mouse liver. Interestingly, however, hGRβ did not repress PEPCK in GR liver knockout (GRLKO) mice. In contrast, hGRβ regulates the expression of STAT1 in the livers of both WT and GRLKO mice. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays demonstrated that hGRβ binds to the intergenic glucocorticoid response element (GRE) of the STAT1 gene. Furthermore, treatment with RU486 inhibited the upregulation of STAT1 mediated by hGRβ. Finally, our array data demonstrate that hGRβ regulates unique components of liver gene expression in vivo by both GRα-dependent and GRα-independent mechanisms.
虽然体外研究表明,糖皮质激素受体(GR)剪接异构体,即人GR(hGR)的β异构体,可作为经典hGRα的显性负性抑制剂并导致糖皮质激素抵抗,但hGRβ的体内功能却鲜为人知。为此,我们构建了一种腺相关病毒(AAV),以在肝细胞特异性启动子的控制下在小鼠肝脏中表达hGRβ。对小鼠肝脏进行全基因组表达分析表明,hGRβ显著增加了众多基因的表达,其中许多基因与内分泌系统紊乱和炎症反应有关。在生理上,hGRβ拮抗GRα的功能,并通过下调野生型(WT)小鼠肝脏中的磷酸烯醇式丙酮酸羧激酶(PEPCK)来减弱肝糖异生。然而,有趣的是,hGRβ在GR肝脏敲除(GRLKO)小鼠中并未抑制PEPCK。相反,hGRβ调节WT和GRLKO小鼠肝脏中STAT1的表达。染色质免疫沉淀(ChIP)和荧光素酶报告基因检测表明,hGRβ与STAT1基因的基因间糖皮质激素反应元件(GRE)结合。此外,用RU486处理可抑制hGRβ介导的STAT1上调。最后,我们的阵列数据表明,hGRβ在体内通过GRα依赖性和GRα非依赖性机制调节肝脏基因表达的独特成分。