Interconnection of cellular autophagy and endosomal membrane trafficking and its role in hepatitis B virus replication, assembly, and release

乙型肝炎病毒（HBV）引起人类急性和慢性感染。据估计，全世界有2.9亿乙肝病毒携带者，乙肝病毒感染仍然是对公共卫生的全球性威胁。慢性HBV感染患者容易发生肝硬化、肝功能衰竭和肝细胞癌（HCC）。研究工作旨在了解病毒的发病机制和潜在的分子机制。近年来，人们对宿主细胞内HBV的复制、组装和病毒粒子的产生进行了广泛的研究。细胞内体运输和自噬是HBV组装和病毒粒子产生的两个重要过程。我们之前的研究表明，在某些条件下，如内质网应激，HBV复制和HBsAg生物发生与自噬过程密切相关。在这个拟议的项目中，我们将解决自噬和内体膜运输如何协同促进HBV复制，组装和释放的问题。基于现有的信息，我们提出了一个工作模型，即HBV蛋白和衣壳可能被自噬小室捕获和分离，在那里HBV可以进行复制和组装。自噬过程不是旁路，但可能是与内体/多泡体（MVBs）相关的HBV病毒粒子产生的主要途径。尽管大部分病毒粒子和亚病毒颗粒在自噬溶酶体中被降解，但仍有相当一部分逃避了降解，并通过一种尚未明确的方式输出。研究表明，自噬体可以与核内体融合形成两性体。我们假设与自噬体结合组装的HBV病毒粒子在两性体中被分类输出并通过MVBs释放。在这个项目中，我们将研究自噬和内体膜运输如何连接和协调以促进HBV的组装和释放。同时，动态的细胞膜运输和融合可能允许HBV的组装和释放。外泌体生物发生等过程也将被研究其在HBV病毒粒子产生中的潜在作用。我们提出的项目将阐明不同的细胞机制对HBV在宿主细胞中的复制、组装和释放的贡献，并为未来的药物开发发现潜在的病毒靶点。

Hepatitis B virus (HBV) causes acute and chronic infection in humans. With estimated 290 million of HBV carriers worldwide, HBV infection remains a global threat to public health. Patients with chronic HBV infection are prone to cirrhosis, liver failure, and hepatocellular carcinoma (HCC). Research efforts are directed to understand viral pathogenesis and underlying molecular mechanisms. Recently, HBV replication, assembly, and virion production in host cells have been extensively studied. Cellular endosomal trafficking and autophagy are two important processes for HBV assembly and virion production. Our previous studies showed a close association of HBV replication and HBsAg biogenesis with the autophagic process under some conditions, e.g. ER stress. In this proposed project, we will address the questions how autophagy and endosomal membrane trafficking cooperatively facilitate HBV replication, assembly, and release. Based on the available information, we propose a working model that HBV proteins and capsids may be captured and segregated by autophagosome compartments where HBV replication and assembly could take place. The autophagic process is not a bypass but could be a major pathway in connection with endosomes/multi vesicular bodies (MVBs) for HBV virion production. Though a major part of virions and subviral particles are degraded in autophago-lysosomes, a significant fraction evades the degradation and is exported through a not yet well-defined way. It has been demonstrated that autophagosomes could fuse with endosomes to form amphisomes. We hypothesize that HBV virions assembled in association with autophagosomes are sorted in amphisomes for export and released through MVBs. In this project, we will examine how antophagy and endosomal membrane trafficking are connected and coordinated to facilitate HBV assembly and release. At the same time, dynamic cellular membrane trafficking and fusion may allow HBV assembly and release. The processes like exosome biogenesis will also be examined for their potential role in HBV virion production. Our proposed project will clarify the contribution of different cellular mechanisms to HBV replication, assembly, and release from host cells and uncover potential viral targets for future drug development.