Role of Hepatitis B virus X protein in HBV replication

描述（由申请人提供）：肝细胞癌（HCC）和慢性乙型肝炎病毒（HBV）感染之间的关系引起了人们对HBV感染如何增加肝癌风险的极大兴趣。根据对感染土拨鼠肝炎病毒的土拨鼠的研究，假设所有哺乳动物肝炎病毒（包括人类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反应；然而，这是如何实现的尚不清楚。大多数试图确定HBx在HBV复制过程中的重要作用，并了解HBx如何调节细胞信号通路的研究，都是在来源于肝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。本研究旨在通过原代大鼠肝细胞培养了解HBx的关键活性，并确定这些活性如何影响肝细胞生理和HBV复制。AIM 1的研究将描述HBx激活肝细胞钙信号通路的分子机制及其如何影响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种相互作用如何影响肝细胞生理和HBV复制。AIM 3特别关注HBx单独表达或HBV复制过程中对细胞凋亡的调节。虽然与转化细胞相比，HBx的基本活性在肝细胞中可能被保留，但这些活性的强度、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HBx活性，并对HBx在HBV复制过程中的作用提供更复杂的理解。

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.