Poonsiri Thanalai, Wright Gareth S A, Diamond Michael S, Turtle Lance, Solomon Tom, Antonyuk Svetlana V
Molecular Biophysics Group, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, United Kingdom.
Health Protection Research Unit on Emerging and Zoonotic Infections, Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom.
J Virol. 2018 Mar 14;92(7). doi: 10.1128/JVI.01868-17. Print 2018 Apr 1.
Japanese encephalitis virus (JEV) is a mosquito-transmitted flavivirus that is closely related to other emerging viral pathogens, including dengue virus (DENV), West Nile virus (WNV), and Zika virus (ZIKV). JEV infection can result in meningitis and encephalitis, which in severe cases cause permanent brain damage and death. JEV occurs predominantly in rural areas throughout Southeast Asia, the Pacific Islands, and the Far East, causing around 68,000 cases of infection worldwide each year. In this report, we present a 2.1-Å-resolution crystal structure of the C-terminal β-ladder domain of JEV nonstructural protein 1 (NS1-C). The surface charge distribution of JEV NS1-C is similar to those of WNV and ZIKV but differs from that of DENV. Analysis of the JEV NS1-C structure, with molecular dynamics simulation and experimental solution small-angle X-ray scattering, indicates extensive loop flexibility on the exterior of the protein. This, together with the surface charge distribution, indicates that flexibility influences the protein-protein interactions that govern pathogenicity. These factors also affect the interaction of NS1 with the 22NS1 monoclonal antibody, which is protective against West Nile virus infection. Liposome and heparin binding assays indicate that only the N-terminal region of NS1 mediates interaction with membranes and that sulfate binding sites common to NS1 structures are not glycosaminoglycan binding interfaces. This report highlights several differences between flavivirus NS1 proteins and contributes to our understanding of their structure-pathogenic function relationships. JEV is a major cause of viral encephalitis in Asia. Despite extensive vaccination, epidemics still occur. Nonstructural protein 1 (NS1) plays a role in viral replication, and, because it is secreted, it can exhibit a wide range of interactions with host proteins. NS1 sequence and protein folds are conserved within the genus, but variations in NS1 protein-protein interactions among viruses likely contribute to differences in pathogenesis. Here, we compared characteristics of the C-terminal β-ladder domain of NS1 between flaviviruses, including surface charge, loop flexibility, epitope cross-reactivity, membrane adherence, and glycosaminoglycan binding. These structural features are central to NS1 functionality and may provide insight into the development of diagnostic tests and therapeutics.
日本脑炎病毒（JEV）是一种由蚊子传播的黄病毒，与其他新兴病毒病原体密切相关，包括登革病毒（DENV）、西尼罗河病毒（WNV）和寨卡病毒（ZIKV）。JEV感染可导致脑膜炎和脑炎，严重时会造成永久性脑损伤甚至死亡。JEV主要发生在东南亚、太平洋岛屿和远东的农村地区，每年在全球导致约68000例感染病例。在本报告中，我们展示了日本脑炎病毒非结构蛋白1（NS1-C）C末端β-梯状结构域的2.1埃分辨率晶体结构。JEV NS1-C的表面电荷分布与WNV和ZIKV相似，但与DENV不同。通过分子动力学模拟和实验性溶液小角X射线散射对JEV NS1-C结构进行分析，结果表明该蛋白外部的环具有广泛的灵活性。这与表面电荷分布一起表明，灵活性会影响决定致病性的蛋白质-蛋白质相互作用。这些因素还会影响NS1与22NS1单克隆抗体的相互作用，该抗体对西尼罗河病毒感染具有保护作用。脂质体和肝素结合试验表明，只有NS1的N末端区域介导与膜的相互作用，且NS1结构中常见的硫酸盐结合位点并非糖胺聚糖结合界面。本报告突出了黄病毒NS1蛋白之间的几个差异，有助于我们理解它们的结构-致病功能关系。JEV是亚洲病毒性脑炎的主要病因。尽管进行了广泛的疫苗接种，但疫情仍有发生。非结构蛋白1（NS1）在病毒复制中起作用，并且由于它会分泌，所以它可以与宿主蛋白表现出广泛的相互作用。NS1序列和蛋白折叠在该属内是保守的，但病毒之间NS1蛋白-蛋白质相互作用的差异可能导致发病机制的不同。在此，我们比较了黄病毒之间NS1 C末端β-梯状结构域的特征，包括表面电荷、环的灵活性、表位交叉反应性、膜粘附性和糖胺聚糖结合。这些结构特征对于NS1的功能至关重要，可能为诊断测试和治疗方法的开发提供思路。
