细胞内磷酯酰肌醇-4-磷酸（PI4P）水平的上调是丙肝病毒侵染所必需的。哺乳动物细胞中PI4P水平受到PI4P激酶和磷酸酶调节，大量研究围绕丙肝病毒如何利用PI4P激酶，而PI4P磷酸酶Sac1如何被丙肝病毒挟持尚有待研究。基于前期研究，本项目提出的科学假设是：丙肝病毒蛋白分别招募COPI通路的关键分子GBF1与ARFGAP1，从而促进COPI囊泡形成，PI4P磷酸酶Sac1作为COPI的货物被运离丙肝病毒复制微环境，使得该区域的PI4P保持较高水平，有利于病毒复制。本项目研究内容包括：(1)分析丙肝病毒蛋白对COPI囊泡运输的影响；(2) 阐明GBF1与丙肝病毒蛋白相互作用对Sac1定位和PI4P水平的影响；(3) 阐明ARFGAP1与丙肝病毒蛋白相互作用对Sac1定位和PI4P水平的影响。本项目的研究将为丙肝病毒复制微环境中PI4P水平的调节提供新的机制。

Upregulation of intracellular PI4P level has been demonstrated to be essential for HCV replication. In mammalian cells, the homeostasis of PI4P is maintained by PI4P kinases and phosphatases. While extensive studies have focused on the regulation of PI4P kinases by HCV, little is known about whether HCV manipulates the host PI4P phosphatase Sac1. Based on our preliminary results, we propose the following hypothesis. By interacting with the key components of the COPI vesicular transport, including GBF1 and ARFGAP1, HCV-encoded proteins dislocate Sac1 from the viral replication area to achieve a PI4P-enriched environment beneficial for HCV replication. To test this hyphothesis, we propose three aims. Aim 1: we will evaluate the capacity of individual HCV proteins in manipulating COPI transport pathway. Aim 2: we will explore the mechanism how association of HCV proteins with GBF1 dislocates Sac1 to maintain high level of PI4P. Aim 3: we will elucidate how association of HCV proteins with ARFGAP1 dislocates Sac1 to maintain high level of PI4P. Our work will shed mechanistic insight on how HCV regulates PI4P level in its replication area.