Molecular Mechanisms of Intrahepatic Cholestasis

描述(出自申请人)：FIC1疾病包括一系列肝脏问题，从“良性”复发性肝内胆汁淤积症(BRIC)到严重的、顽固性和组织学进行性胆汁淤积症(Byler病)。全身表现累及胰腺、肺、胃肠道和听觉系统。FIC1疾病是由FIC1(ATP8B1)基因突变引起的，该基因的功能仍然难以捉摸。我们在揭示FIC1病的病理生理学方面取得了重要进展。法尼类X受体(FXR)介导的信号转导在FIC1病患儿回肠中异常。我们已经在细胞培养中建立了FIC1疾病的模型。FIC1缺乏导致FXR活性降低的转录效应包括肠道功能增强和胆汁酸转运功能减弱。我们首次证明，较轻形式的FIC1相关疾病(即BRIC)是由于FIC1功能及其膜靶向的部分缺陷造成的，而严重疾病与功能完全缺失有关。我们已经将FIC1和FXR机械地联系在一起。FIC1激活磷脂酶D2(PLD2)和蛋白激酶C(PKC)途径？导致FXR磷酸化、核定位和激活的信号通路。这份R01提案旨在更全面地探讨FIC1功能和疾病的分子机制。这些研究将产生新的见解，将进一步加深我们对淤胆性肝病、正常肝脏和肠道生理、FIC1病的多变的非肝脏表现以及FIC1转运的生物学和临床后果的理解。很有可能，这些见解将转化为广泛学科的治疗进展。这项研究将涉及三个特定的目标，以检验质膜FIC1信号通过PLD2和PKC？导致包括FXR在内的关键信号分子的表达和磷酸化发生大量变化。它还将检验这一假设，即在人类中，FIC1疾病是FXR介导的信号通路关键变化的结果。这些假说将以以下具体目标进行验证：1)FIC1影响的信号转导通路的特征；2)FIC1疾病的分子机制分析；3)胆汁淤积症患者胆汁中FXR信号的检测。FIC1病(又名Byler病或PFIC1)是一种复杂的多系统疾病，其机制(S)尚不清楚。最近的分子发现为了解这种疾病(提供新的治疗方法)和探索肝、胰腺、胃肠道和肺的基本生理学提供了机会。

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.