Molecular Regulation of Hepatic Transporters

描述(申请人提供)：肝脏对炎症反应的中心特征之一是抑制广泛的核心生理功能，包括那些维持胆汁酸的肝胆运输所必需的功能。除了对转运蛋白膜表达和功能的翻译后调节外，基于炎症的细胞信号通路作用于核靶标，从转录上抑制必要的胆汁酸转运蛋白Ntcp和Bsep的表达。中心型NR超家族成员和异源二聚体伙伴RXRpha是这两个基因的主要转录激活因子，其核活动迅速被基于炎症的细胞信号抑制。RXRpha靶基因表达减少会导致多种功能损害和肝细胞损伤。细胞信号通路如何抑制RXRpha功能尚不清楚，并形成了本申请中提出的探索和干预的基础。总体的统一假设是，炎症细胞信号通路通过翻译后修饰、核输出和蛋白酶体降解的协调级联作用降低RXRpha的核活性。以下四个目标将确定炎症介导的胆汁淤积的基本生理学和病理生理学，并探索新的治疗方法。目的1：明确IL-1β诱导的RXRα核输出的分子机制。目的2：确定RXRα泛素化和蛋白酶体降解在IL-1β诱导的信号通路中的作用。目的3：探讨胆汁酸和IL-1β介导的修饰RXRpha功能的通路之间的串扰。目的：探讨抗炎药对IPS肝脏炎症模型转运蛋白基因和蛋白表达的影响。通过体外和体内相结合的方法，我们可以探索在肝脏炎症介导的细胞信号转导背景下，旨在恢复RXRα功能、肝胆转运体功能和胆汁流量的机制、介体和潜在的治疗干预措施。这些研究的最终目标是提供合理的分子靶点，用于测试专门设计用于干扰炎症介导的途径的破坏性后果的治疗方法，这些途径参与了几乎所有形式的急性和慢性肝病。

DESCRIPTION (provided by applicant): One of the central features of the hepatic response to inflammation is the suppression of a broad array of core physiological functions, including those essential to maintaining hepatobiliary transport of bile acids. In addition to post-translational regulation of transporter protein membrane expression and function, inflammation-based cell signaling pathways act on nuclear targets to transcriptionally suppress the expression of the essential bile acid transporters Ntcp and Bsep. The central Type II NR superfamily member and heterodimer partner RXRalpha is a major transcriptional activator of these two genes, and its nuclear activity is rapidly suppressed by inflammation-based cell signaling. Reduced RXRalpha target gene expression leads to multiple functional impairments and damage to hepatocytes. How cell signaling pathways suppress RXRalpha function is unknown, and forms the basis for the explorations and interventions proposed in this application. The overall unifying hypothesis is that inflammatory cell signaling pathways reduce nuclear activity of RXRalpha via a coordinated cascade of post-translational modification, nuclear export and proteasomal degradation. The following four aims will determine the underlying physiology and pathophysiology of inflammation-mediated cholestasis and explore novel therapeutics. Aim 1: Define the molecular mechanisms mediating IL-1beta-induced nuclear export of RXRalpha. Aim 2: Determine roles for ubiquitination and proteasomal degradation of RXRalpha in response to IL-1beta- induced signaling pathways. Aim 3: Explore crosstalk between bile acid and IL-1beta-mediated pathways that modify RXRalpha function. Aim 4: Investigate the effects of anti-inflammatory agents on transporter gene and protein expression in the IPS model of hepatic inflammation. It is through a combined in vitro and in vivo approach that we can explore the mechanisms, mediators, and potential therapeutic interventions aimed at restoring RXRalpha function, hepatobiliary transporter function, and bile flow, in the setting of inflammation-mediated cell signaling in liver. The ultimate goal of these studies is to provide rational molecular targets for the testing of therapies specifically designed to interfere with the damaging consequences of inflammation-mediated pathways, which are engaged in nearly all forms of acute and chronic liver diseases.