Molecular Mechanisms of Intrahepatic Cholestasis

描述（来自申请方）：FIC 1疾病包括一系列肝脏问题，范围从“良性”复发性肝内胆汁淤积（BRIC）到重度、持续性和组织学进行性胆汁淤积（Byler病）。全身表现涉及胰腺、肺、胃肠道和听觉系统。FIC 1疾病是由FIC 1（ATP 8B1）基因突变引起的，其功能仍然难以捉摸。我们在阐明FIC 1疾病的病理生理学方面取得了重要进展。法尼醇X受体（FXR）介导的信号传导在FIC 1疾病儿童的回肠中异常。我们在细胞培养中模拟了FIC1疾病。由于FIC 1缺乏而导致的FXR活性降低的转录效应包括增强的肠道和减少的小管胆汁酸转运。我们是第一个表明FIC 1相关疾病（即BRIC）的轻度形式是由FIC 1功能及其膜靶向的部分缺陷引起的，而严重的疾病与功能的完全缺失有关。我们已经将FIC 1和FXR机械地联系起来。FIC 1激活涉及磷脂酶D2（PLD 2）和蛋白激酶C（PKC）的通路？信号通路导致磷酸化、核定位和FXR活化。该R01提案旨在更全面地探索FIC 1功能和疾病的分子机制。这些研究将产生新的见解，这将进一步加深我们对胆汁淤积性肝病，正常肝脏和肠道生理学，FIC 1疾病的多变非肝表现以及FIC 1贩运的生物学和临床后果的理解。这些见解很可能会转化为广泛学科的治疗进展。这项研究将涉及三个具体的目标，测试的假设，质膜FIC1信号通过PLD 2和PKC？导致包括FXR在内的关键信号分子的表达和磷酸化的许多改变。它还将测试人类FIC 1疾病是FXR介导的信号通路发生关键变化的结果这一假设。这些假设将通过以下具体目的进行检验：1）FIC 1影响的信号转导途径的表征，2）FIC 1疾病的分子机制分析，3）人胆汁淤积症胆囊中FXR信号传导的检查。FIC 1疾病（又名Byler病或PFIC 1）是一种复杂的多系统疾病，其机制尚不清楚。最近的分子发现提供了一个机会，了解这种疾病（提供新的治疗方法），并探索肝脏，胰腺，胃肠道和肺部的基本生理学。

DESCRIPTION (from the applicant): FIC1 disease includes a spectrum of liver problems ranging from "benign" recurrent intrahepatic cholestasis (BRIC) to severe, unremitting and histologically progressive cholestasis (Byler Disease). Systemic manifestations involve the pancreas, lung, gastrointestinal tract and auditory system. FIC1 disease result from mutations in the FIC1 (ATP8B1) gene, whose function remains elusive. We have made important advances in unraveling the pathophysiology of FIC1 disease. Farnesoid X-Receptor (FXR) mediated signaling is abnormal in ileum of children with FIC1 disease. We have modeled FIC1 disease in cell culture. The transcriptional effects of reduced FXR activity due to FIC1 deficiency include enhanced intestinal and diminished canalicular bile acid transport. We are the first to show that milder forms of FIC1 related disease (i.e. BRIC) result from a partial defect in both FIC1 function and its membrane targeting, while severe disease is associated with a complete absence of function. We have mechanistically linked FIC1 and FXR. FIC1 activates a pathway involving Phospholipase D2 (PLD2) and Protein Kinase C (PKC) ? signaling pathway leading to phosphorylation, nuclear localization and activation of FXR. This R01 proposal seeks to more fully explore the molecular mechanisms of FIC1 function and disease. Novel insights will be generated from these studies that will further our understanding of cholestatic liver disease, normal hepatic and intestinal physiology, the protean nonhepatic manifestations of FIC1 disease, and the biological and clinical consequences of FIC1 trafficking. It is very likely that these insights will translate into therapeutic advances in a broad range of disciplines. This research will involve three specific aims that test the hypothesis that plasma membrane FIC1 signals through PLD2 and PKC? leading to numerous alterations in the expression and phosphorylation of key signaling molecules including FXR. It will also test the hypothesis that in humans FIC1 disease is the result of critical changes in FXR-mediated signaling pathways. These hypotheses will be tested with the following specific aims; 1) Characterization of the signal transduction pathways influenced by FIC1, 2) Analysis of the molecular mechanisms of FIC1 disease, 3) Examination of FXR signaling in gallbladder in human cholestasis. FIC1 disease (aka Byler Disease or PFIC1) is a complex multisystem disorder whose mechanism(s) are not known. Recent molecular discoveries provide an opportunity to understand this disease (providing new therapies) and to explore basic physiology of the liver, pancreas, gastrointestinal tract and lungs.