Hepatitis HBx-Mediated Pathogenesis

描述（由申请人提供）：慢性HBV感染是发展为肝细胞癌（HCC）的主要危险因素，每年造成超过100万人死亡。我们已经在表达由人类α -l-抗胰蛋白酶调节序列（ATX小鼠）驱动的HBV调节蛋白（HBx）的转基因小鼠中建立了HCC辅助因子的作用。我们最近的研究表明，辅助因子的作用涉及HBx解除肝细胞周期控制的能力。虽然HBx对病毒在体内的复制至关重要，但它所提供的功能尚不清楚。我们假设HBx在病毒复制过程中的重要作用是使肝细胞具备支持病毒复制所有步骤的能力。在目前的应用中，我们将探索HBx对G0肝细胞的影响及其在G1早期的过渡，使用区分细胞周期这些阶段的标记物。我们还假设HBx在G1限制点上保持非分裂细胞，并将使用RNA抑制来检测HBx可能发挥这种作用的候选蛋白。我们还将探讨HBx对体内肝细胞G0/G1转变的影响，以及在afbl诱导的热点p53突变存在的情况下。最后，ATX小鼠的肝脏含有降低的Caspase-3水平，我们将验证在细胞毒性细胞因子的反应中，HBx抑制细胞凋亡作为保护肝细胞免受免疫介导的细胞死亡的一种手段的假设。HBx是HBV编码的唯一调节蛋白，我们预计它将在病毒生命周期中发挥不止一种关键作用。提出的方案建立在我们的HBx相关HCC模型上，该模型表明HBx对细胞周期控制的重要贡献。计划中的研究将检查HBx在非分裂肝细胞中的功能，获得的结果将为合理开发治疗慢性HBV感染的新疗法提供重要见解。我们的研究结果还将揭示病毒与宿主的基本相互作用，这种相互作用可能扩展到在肝脏中复制的其他病毒。

DESCRIPTION (provided by applicant): Chronic infection with HBV is a major risk factor in the development of hepatocellular carcinoma (HCC), and is responsible for over 1 million deaths each year. We have established an HCC cofactor role in transgenic mice that express the HBV regulatory protein (HBx) driven by the human alpha-l-anti-trypsin regulatory sequences (ATX mice). Our recent studies indicate that the cofactor role involves the ability of HBx to deregulate hepatocyte cell cycle controls. Although HBx is essential for virus replication in vivo, the function that it provides is not known. We hypothesize that the essential role of HBx during viral replication is to prepare hepatocytes to become competent to support all steps in virus replication. In the present application, we will explore the effects of HBx on G0 hepatocytes and their transition through early G1, using markers that distinguish these stages of the cell cycle. We additionally hypothesize that HBx holds nondividing cells at a G1 restriction point, and will use RNA inhibition to examine candidate proteins through which HBx may exert this effect. We will also explore the effect of HBx on hepatocyte G0/G1 transition in vivo, and in the presence of the AFBl-induced hotspot p53 mutation. Finally, the livers of ATX mice contain decreased levels of Caspase-3, and we will test the hypothesis that in response to cytotoxic cytokines, HBx inhibits apoptosis as a means of protecting hepatocytes from immune-mediated cell death. HBx is the sole regulatory protein encoded by HBV, we expect it will provide more than one critical role during the virus life cycle. The proposed program builds on our model of HBx-related HCC that indicates an important contribution of HBx effects on cell cycle control. The planned studies examine HBx function in nondividing liver cells, and the results obtained will provide important insight into the rational development of new therapies to treat chronic HBV infection. Our results will also reveal fundamental virus-host interactions that may extend to other viruses that replicate in the liver.