Coordination of gut-liver bile acid signaling by FXR

项目摘要 本申请的总体目标是确定肝脏和肠道在调节中的相互作用。 以胆汁酸（BA）代谢为重点的进食状态代谢。BA作为生理洗涤剂发挥作用 帮助消化脂质营养素，但也作为信号分子，通过以下方式深刻影响新陈代谢： 激活核和膜BA受体，还通过介导肠FGF 15/19（人）的诱导， FGF 19;小鼠FGF 15）。过量的BA是有毒的，因此必须严格控制其水平， 核受体FXR在这种调节中起关键作用。尽管最近取得了进展， 由BA和FGF 15介导的肝和肠之间的相互作用以调节BA水平，特别是 肝Cyp 7a 1的表达，限速BA合成酶，没有很好地理解。我们有 初步证据表明，FXR的Src对FGF 15介导的磷酸化在这一过程中起重要作用。 相互作用基于我们的初步数据，我们假设FXR在Tyr-67的Src磷酸化是一个可能的机制。 在生理条件下由FGF 15信号传导介导，并且Y67 FXR磷酸化是 基因选择性转录调控对降低肝脏BA水平和终止FGF 15的重要性 发信号。为了验证这一假设，我们提出了以下具体目标：1）检查Src在体内的作用 FXR磷酸化在调节BA水平，保护正常小鼠和正常小鼠的肝胆缺陷中的作用 通过检测FXR和Src及其磷酸化水平， 在来自原发性胆汁淤积患者的肝脏样品中形成。2)定义FXR的功能和机制 通过FGF 15和BA激活的Src的磷酸化调节BA代谢和3）确定作用 FGF 15介导的FXR磷酸化，与PPARα协同，终止FGF 15信号传导。 将使用多种体外和体内方法，包括遗传和病毒产生的小鼠模型， ChIP-seq基因组分析以鉴定用FGF 19处理的小鼠中的FXR结合位点。我们的专业知识 核受体的翻译后修饰和BA代谢的转录调节是唯一的 使我们有资格解决这一重要的研究问题的作用，翻译后磷酸化的FXR 调节BA代谢。我们的建议将确定FGF 15的新功能和机制。 诱导FXR磷酸化，并为BA-和 FGF 15相关疾病，包括胆汁淤积性肝病。

Project Summary The overall goal of this application is to determine the interplay between the liver and intestine in the regulation of fed-state metabolism with emphasis on bile acid (BA) metabolism. BAs function as physiological detergents to aid digestion of lipid nutrients but also function as signaling molecules that profoundly impact metabolism by activating nuclear and membrane BA receptors and also by mediating induction of intestinal FGF15/19 (human FGF19; mouse FGF15). BAs in excess are toxic so that their levels must be tightly controlled and the BA nuclear receptor FXR plays a key role in this regulation. Despite recent advances, the mechanisms underlying the interplay between the liver and intestine mediated by BAs and FGF15 to regulate BA levels, in particular hepatic expression of Cyp7a1, the rate-limiting BA synthetic enzyme, are not well understood. We have preliminary evidence that FGF15-mediated phosphorylation by Src of FXR plays an important role in this interplay. Based on our preliminary data, we hypothesize that Src phosphorylation of FXR at Tyr-67 is mediated by FGF15 signaling under physiological conditions and that Y67FXR phosphorylation is important for gene-selective transcriptional regulation to reduce liver BA levels and terminate FGF15 signaling. To test this hypothesis, we propose the following Specific Aims: 1) Examine the in vivo role of Src phosphorylation of FXR in regulating BA levels, protecting against hepatobiliary defects in normal mice and in mice challenged with biliary insults, and human relevance by examining FXR and Src and their phosphorylated forms in liver samples from primary cholestasis patients. 2) Define the function and mechanisms of FXR phosphorylation by FGF15- and BA-activated Src in the regulation of BA metabolism and 3) determine the role of FGF15-mediated phosphorylation of FXR, in coordination with PPARα, in terminating FGF15 signaling. Multiple in vitro and in vivo approaches will be used, including genetic and virally generated mouse models and ChIP-seq genomic analysis to identify FXR binding sites globally in mice treated with FGF19. Our expertise on post-translational modifications of nuclear receptors and transcriptional regulation of BA metabolism uniquely qualifies us to address this important research question of the role of posttranslational phosphorylation of FXR in regulation of BA metabolism. Our proposal will determine the novel function and mechanisms of FGF15- induced phosphorylation of FXR, and provide new potential therapeutics and diagnostic markers for BA- and FGF15-related diseases, including cholestatic liver diseases.