Cytoskeletal Linking Proteins in Liver Function

描述(申请人提供)：肝脏形成胆汁的结果 来自肝细胞的胆盐和有机溶质的顶端分泌和 来自胆管细胞的氯化物、碳酸氢盐和水。这种媒介分泌物 需要严格的极化和不同的协调监管 两种细胞类型的转运蛋白。人体必需激素的分布和活性 肝细胞转运蛋白(如多药耐药蛋白2； MRP2)和胆管细胞(例如囊性纤维化跨膜电导 监管机构；cftr)通过cAMP进行监管。活跃度或分布减少 转运蛋白是许多胆汁淤积性肝病的推定基础。 在其他类型的细胞中，PDZ结构域表达蛋白将膜蛋白连接到 细胞骨架并调节其分布、保留、聚集和 膜微区内的活性。在上皮细胞中， Ezrin-Radioxin-Moesin结合磷蛋白50(EBP50)被认为与 调节依赖cAMP的心尖转运事件。最近在我们的研究中 实验室证明EBP50高度集中在顶端区域 肝细胞和胆管细胞。EBP50-CFTR相互作用的中断 胆管细胞导致CFTRcAMP活性丧失， Cftr依赖的细胞体积调节。EBP50的一种机制放大了这些 研究表明，EBP50能够对CFTR产生影响 体外和体内的齐聚作用。假设EBP50服务于 在胆汁形成的能力和调节中的关键作用，建议 研究将(1)表征调节和功能含义 EBP50齐聚；(2)EBP50在脑内的生理作用 调节CFTR在胆管细胞中的分布和活性；以及(3)比较 并将EBP50-CFTR功能范式发育的胆管细胞与 EBP50-mrp2相互作用在肝细胞中的功能后果。这条线 为调查提供新的见解 调节胆汁形成和胆汁淤积性肝病的机制。

DESCRIPTION (provided by applicant): The formation of bile by the liver results from apical secretion of bile salts and organic solutes from hepatocytes and chloride, bicarbonate and water from cholagniocytes. This vectorial secretion requires the strict polarization and coordinated regulation of distinct transporters in both cell types. The distribution and activity of essential transporter proteins in hepatocytes (e.g. multi-drug resistance protein 2; mrp2) and cholangiocytes (e.g. cystic fibrosis transmembrane conductance regulator; CFTR) is regulated through cAMP. Decreased activity or distribution of transporters represents a putative basis of many cholestatic liver diseases. In other cell types, PDZ domain-expressing proteins tether membrane proteins to the cytoskeleton and moderate their distribution, retention, clustering and activity within membrane microdomains. In epithelial cells, Ezrin-Radixin-Moesin binding phosphoprotein 50 (EBP50) has been implicated in modulating cAMP-dependent apical transport events. Recent studies in our laboratory demonstrate EBP50 is highly concentrated at the apical domain of hepatocytes and cholangiocytes. Disruption of the EBP50-CFTR interaction in cholangiocytes results in the loss of cAMP activation of CFTR and CFTR-dependent cell volume regulation. A mechanism for EBP50 to amplify these effects on CFTR were revealed in studies that showed EBP50 is capable of oligomerizing both in vitro and in vivo. Hypothesizing that EBP50 serves a pivotal role in the capacity and regulation of bile formation, the proposed studies will (1) characterize the regulation and functional implications of EBP50 oligomerization; (2) delineate the physiologic role of EBP50 in modulating CFTR distribution and activity in cholangiocytes; and (3) compare and contrast the EBP50-CFTR functional paradigm developed cholangiocytes to the functional consequences of the EBP50-mrp2 interaction in hepatocytes. This line of investigation holds great promise in providing novel insights into the mechanisms underlying regulated bile formation and cholestatic liver disease.