The Role of Copper in Pediatric Liver Disease

描述(申请人提供)：铜是一种必需的微量元素，在细胞呼吸、抗氧化防御和铁平衡的生物化学中起着关键作用。肝脏是人类体内铜稳态的中心器官，这些研究的长期目标是确定铜在儿童肝病中的作用。虽然先前的研究揭示了铜伴侣蛋白Atox1和肝豆状核变性ATPase(ATP7B)在肝脏铜代谢中的核心作用，但肝细胞分泌途径中导致铜在小管膜上排泄的机制仍然知之甚少。最近，ATP7B和Murr1之间的直接相互作用被证明，Murr1是贝德灵顿梗铜中毒基因产物的人类同源物，这为Mutt1在铜排泄的肝胆病理生理中的作用提供了生化证据。这项提案的具体目的是为了阐明Murr1和ATP7B在这一过程中的作用。结构/功能研究将使用定点突变来描述Murr1与ATP7B相互作用的生化细节。Murr1基因错义突变患者的肝脏铜中毒的病理生理学将通过检测转基因小鼠的铜稳态和ATP7B功能以及定向胚系缺失Murr1基因的小鼠来阐明。Murr1在铜排泄中的功能作用将通过分离和鉴定与ATP7B相互作用形成的Murr1异寡聚体中存在的特定相互作用蛋白来确定。最后，ATP7B的羧基末端在铜介导的肝细胞转运和排泄中的作用将通过体外表达克隆来确定与该结构域相互作用的蛋白质。综上所述，这些研究结果将允许对肝脏内排泄事件的肝胆病理生理学有新的见解，并可能允许新的治疗方法来预防或改善一些儿科肝病的肝脏损伤。

DESCRIPTION (provided by applicant): Copper is an essential trace element with a critical role in the biochemistry of cellular respiration, antioxidant defense and iron homeostasis. The liver is the central organ of copper homeostasis in humans and the long-term objective of these studies is to define the role of copper in pediatric liver disease. While previous studies have revealed a central role for the copper chaperone Atox1 and the Wilson disease ATPase (ATP7b) in hepatic copper metabolism, the mechanisms within the hepatocyte secretory pathway that lead to excretion of this metal at the canalicular membrane remain poorly understood. Most recently, a direct interaction has been demonstrated between ATP7b and Murr1, the human homologue of the Bedlington terrier copper toxicosis gene product, providing biochemical evidence in support of a role for Mutt1 in the hepatobiliary pathophysiology of copper excretion. The specific aims of this proposal are intended to elucidate the role of Murr1 and ATP7b in this process. Structure/function studies will be accomplished using site-directed mutagenesis to delineate the biochemical details of Murr1 interaction with ATP7b. The pathophysiology of hepatic copper toxicosis in patients with missense mutations in Murr1 will be elucidated by examining copper homeostasis and ATP7b function in mice transgenic for these mutations as well as mice with a targeted germline deletion of the Murr1 gene. The functional role of Murr1 in copper excretion will be determined by isolation and characterization of specific interacting proteins present in Murr1 heterooligomeric complexes formed upon interaction with ATP7b. Finally, the role of the carboxyl terminus of ATP7b in copper-mediated trafficking and excretion in hepatocytes will be defined using in vitro expression cloning to characterize the proteins interacting with this domain. Taken together the results of these studies will permit new insights into the hepatobiliary pathophysiology of excretory events within the liver and may allow for novel therapeutic approaches to prevent or ameliorate hepatic injury in a number of pediatric liver diseases.