Role of Hepatitis B virus X protein in HBV replication

描述(由申请人提供)：肝细胞癌与慢性人类乙肝病毒感染之间的联系引起了人们对了解感染乙肝病毒如何增加患肝癌风险的极大兴趣。基于对感染土拨鼠肝炎病毒的土拨鼠的研究，人们认为包括人类乙肝病毒在内的所有哺乳动物肝脏病毒的X蛋白(HBx)是病毒复制所必需的。也有证据表明，HBx有助于肝细胞癌的发展。HBx激活了许多细胞信号级联反应；然而，这是如何实现的还不清楚。大多数研究试图确定HBx在乙肝病毒复制中的重要作用，并了解HBx如何调节细胞信号通路，这些研究都是在来自肝脏肿瘤的肝细胞系中进行的。与真正的肝细胞相比，永生化或转化的肝细胞缺乏生物学相关性。我们已经证明，HBx的一个关键活性是调节细胞内钙信号通路。本研究旨在利用原代培养的大鼠肝细胞来了解HBx的关键活性，并确定这些活性如何影响肝细胞的生理和乙肝病毒复制。AIM 1的研究将表征HBx激活肝细胞钙信号通路的分子机制，以及这如何影响乙肝病毒的复制。AIM 2的研究将集中在HBx和线粒体之间的相互作用以及这如何影响肝细胞生理和乙肝病毒复制。目的3研究HBx单独表达或在复制过程中对细胞凋亡的调控作用。尽管与转化细胞相比，HBx的基本活性可能在肝细胞中保留，但这些活性的大小、持续时间和复杂性在原代肝细胞中可能不同。对原代大鼠肝细胞的研究结果应该更准确地反映真实感染细胞的状态，澄清已报道的不同的HBx活性，并提供对HBx在乙肝复制中的作用的更复杂的理解。

DESCRIPTION (provided by applicant): The association between hepatocellular carcinoma (HCC) and chronic infection with the human hepatitis B virus (HBV) has generated considerable interest in understanding how infection with HBV increases the risk for liver cancer. Based on studies in woodchucks infected with the woodchuck hepatitis virus, it is assumed that the X protein (HBx) of all mammalian hepadnaviruses, including human HBV, is essential for viral replication. There is also evidence that HBx contributes to the development of HCC. HBx activates many cellular signaling cascades; however, how this is accomplished is unclear. Most studies that sought to identify the essential role of HBx during HBV replication, and understand how HBx regulates cellular signaling pathways, were performed in liver cell lines derived from liver tumors. The use of immortalized or transformed hepatocytes suffers from its lack of biological relevance compared to authentic hepatocytes. We have demonstrated that a key activity of HBx is regulation of cellular calcium signaling pathways. This proposal aims to understand key activities of HBx using cultures of primary rat hepatocytes and to determine how these activities influence hepatocyte physiology and HBV replication. Studies in AIM 1 will characterize the molecular mechanism of HBx activation of calcium signaling pathways in hepatocytes and how this influences HBV replication. Studies in AIM 2 will focus on the interaction between HBx and mitochondria and how this impacts hepatocyte physiology and HBV replication. AIM 3 specifically focuses on regulation of apoptosis by HBx expressed alone or during HBV replication. Although the fundamental activities of HBx are likely preserved in hepatocytes as compared to transformed cells, the magnitude, duration and complexity of these activities may differ in primary hepatocytes. Results from studies in primary rat hepatocytes should more accurately reflect the state of an authentic infected cell, clarify the disparate HBx activities that have been reported, and provide a more sophisticated understanding of the role of HBx during HBV replication.