Role of Hepatitis B virus X protein in HBV replication

描述（由申请人提供）：肝细胞癌（HCC）与人B肝炎病毒（HBV）慢性感染之间的相关性引起了人们对了解HBV感染如何增加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，假设所有哺乳动物嗜肝DNA病毒（包括人HBV）的X蛋白（HBx）对病毒复制至关重要。也有证据表明HBx有助于HCC的发展。HBx激活许多细胞信号级联;然而，这是如何实现的尚不清楚。大多数研究试图确定HBx在HBV复制过程中的重要作用，并了解HBx如何调节细胞信号传导途径，这些研究都是在来自肝脏肿瘤的肝细胞系中进行的。与真实肝细胞相比，永生化或转化肝细胞的使用缺乏生物学相关性。我们已经证明HBx的一个关键活性是调节细胞钙信号通路。本提案旨在了解HBx使用原代大鼠肝细胞培养物的关键活动，并确定这些活动如何影响肝细胞生理学和HBV复制。AIM 1的研究将表征肝细胞中HBx激活钙信号通路的分子机制以及这如何影响HBV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学和HBV复制。AIM 3特别关注单独表达或在HBV复制过程中表达的HBx对细胞凋亡的调节。虽然与转化细胞相比，HBx的基本活性可能在肝细胞中保留，但这些活性的幅度、持续时间和复杂性在原代肝细胞中可能不同。原代大鼠肝细胞研究的结果应该更准确地反映真实感染细胞的状态，澄清不同的HBx活动，已报告，并提供了一个更复杂的理解HBx在HBV复制过程中的作用。

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.