Constitutive androstane receptor 1 is constitutively bound to chromatin and ‘primed’ for transactivation in hepatocytes
Constitutive androstane receptor 1 is constitutively bound to chromatin and ‘primed’ for transactivation in hepatocytes
复制标题
组成型雄甾烷受体 1 与染色质组成型结合，并为肝细胞中的反式激活做好准备
作者：
M. McMahon;S. Ding;L. Jiménez;Rémi Terranova;Marie;Antonio Vitobello;J. Moggs;C. Henderson;C. Wolf
构成性雄烷受体(CAR)是一种在肝细胞中表达的异源感受器，可激活与药物代谢、脂质平衡和细胞增殖相关的基因。药物和外源生物激活人CAR的机制研究已经取得了很大进展。然而，激活途径的许多方面仍有待阐明。在本报告中，我们使用病毒构建物在体外和体内CAR−/−小鼠的肝细胞中表达人CAR及其剪接变异体和突变的CAR形式。我们证明CAR的表达挽救了CAR−/−肝细胞对包括苯巴比妥在内的多种CAR激活剂的反应能力。此外，人类CAR的两个主要剪接异构体，CAR2和CAR3，在几乎所有测试的试剂中都是不活跃的。与目前的CAR激活模型不同，异位CAR1在没有诱导剂的情况下，结构性地定位在细胞核中，并装载到Cyp2b10基因上。在阐明苏氨酸T38在CAR调节中的作用的研究中，我们发现T38D突变体即使在CAR激活剂存在的情况下也是不活跃的。然而，T38A突变体被CAR诱导剂激活，表明T38不是CAR激活所必需的。此外，使用抑制剂erlotinib，我们不能确认表皮生长因子受体在CAR调节中的作用。我们的数据表明，CAR是结构性地结合到基因调控区，并受到外源因子的调控，其机制涉及细胞核内的蛋白质磷酸化。
The constitutive androstane receptor (CAR) is a xenobiotic sensor expressed in hepatocytes that activates genes involved in drug metabolism, lipid homeostasis, and cell proliferation. Much progress has been made in understanding the mechanism of activation of human CAR by drugs and xenobiotics. However, many aspects of the activation pathway remain to be elucidated. In this report, we have used viral constructs to express human CAR, its splice variants, and mutant CAR forms in hepatocytes from Car−/− mice in vitro and in vivo. We demonstrate CAR expression rescued the ability of Car−/− hepatocytes to respond to a wide range of CAR activators including phenobarbital. Additionally, two major splice isoforms of human CAR, CAR2 and CAR3, were inactive with almost all the agents tested. In contrast to the current model of CAR activation, ectopic CAR1 is constitutively localized in the nucleus and is loaded onto Cyp2b10 gene in the absence of an inducing agent. In studies to elucidate the role of threonine T38 in CAR regulation, we found that the T38D mutant was inactive even in the presence of CAR activators. However, the T38A mutant was activated by CAR inducers, showing that T38 is not essential for CAR activation. Also, using the inhibitor erlotinib, we could not confirm a role for the epidermal growth factor receptor in CAR regulation. Our data suggest that CAR is constitutively bound to gene regulatory regions and is regulated by exogenous agents through a mechanism which involves protein phosphorylation in the nucleus.
影响因子：
5.1
作者：
Dring, Ann M.;Anderson, Linnea E.;Qamar, Saima;Stoner, Matthew A.
通讯作者：
Stoner, Matthew A.