JVI：发现鞘磷脂能够激活丙型肝炎病毒RNA聚合酶
10月，病毒研究领域着名学术期刊Journal of Virology在线发表了中科院上海巴斯德所最新研究成果，该研究揭示了作为脂筏主要结构成分之一的鞘磷脂能够以基因型特异性的方式激活丙型肝炎病毒（HCV）1b亚型的RNA聚合酶，并且找到了其结合和激活的相关氨基酸位点。这项研究是博士研究生翁磊云在丰田哲也研究员指导下完成的。
目前，世界上约有3%的人感染了HCV，其中主要是1b亚型，但是现在仅有的治疗方法仅对不到50%的1b亚型病毒感染者有效。因此，我们亟需研制出更加高效的新型抗病毒疗法。病毒RNA聚合酶是传统的重要抗病毒药物靶点，而很多宿主因子也通过与病毒RNA聚合酶的相互作用来调节病毒的复制和转录过程，因而也成为重要的抗病毒靶点。已有的研究表明，HCV的复制发生在ER衍生的脂筏结构上，并且其复制过程能够被鞘磷脂（sphingomyelin，SM）生物合成途径的抑制剂所抑制。
丰田哲也研究组发现的鞘磷脂对聚合酶的结合和激活作用，将可以作为研制抗病毒药物的潜在靶点。
该研究成果得到了科技部、国家自然科学基金和中科院等相关基金的资助。
推荐英文摘要：
Journal of Virology, doi:10.1128/JVI.00638-10
Sphingomyelin Activates Hepatitis C Virus RNA Polymerase in a Genotype-Specific Manner
Leiyun Weng,1 Yuichi Hirata,2 Masaaki Arai,3 Michinori Kohara,2 Takaji Wakita,4 Koichi Watashi,4,5 Kunitada Shimotohno,5,6 Ying He,7 Jin Zhong,7 and Tetsuya Toyoda1*
Hepatitis C virus (HCV) replication and infection depend on the lipid components of the cell, and replication is inhibited by inhibitors of sphingomyelin biosynthesis. We found that sphingomyelin bound to and activated genotype 1b RNA-dependent RNA polymerase (RdRp) by enhancing its template binding activity. Sphingomyelin also bound to 1a and JFH1 (genotype 2a) RdRps but did not activate them. Sphingomyelin did not bind to or activate J6CF (2a) RdRp. The sphingomyelin binding domain (SBD) of HCV RdRp was mapped to the helix-turn-helix structure (residues 231 to 260), which was essential for sphingomyelin binding and activation. Helix structures (residues 231 to 241 and 247 to 260) are important for RdRp activation, and 238S and 248E are important for maintaining the helix structures for template binding and RdRp activation by sphingomyelin. 241Q in helix 1 and the negatively charged 244D at the apex of the turn are important for sphingomyelin binding. Both amino acids are on the surface of the RdRp molecule. The polarity of the phosphocholine of sphingomyelin is important for HCV RdRp activation. However, phosphocholine did not activate RdRp. Twenty sphingomyelin molecules activated one RdRp molecule. The biochemical effect of sphingomyelin on HCV RdRp activity was virologically confirmed by the HCV replicon system. We also found that the SBD was the lipid raft membrane localization domain of HCV NS5B because JFH1 (2a) replicon cells harboring NS5B with the mutation A242C/S244D moved to the lipid raft while the wild type did not localize there. This agreed with the myriocin sensitivity of the mutant replicon. This sphingomyelin interaction is a target for HCV infection because most HCV RdRps have 241Q.
