Förster Andreas, Maertens Goedele N, Farrell Paul J, Bajorek Monika
Centre for Structural Biology, Department of Life Sciences, Imperial College London, London, United Kingdom.
Section of Infectious Diseases, Faculty of Medicine, Imperial College London, London, United Kingdom.
J Virol. 2015 Apr;89(8):4624-35. doi: 10.1128/JVI.03500-14. Epub 2015 Feb 11.
Respiratory syncytial virus (RSV) infects epithelial cells of the respiratory tract and is a major cause of bronchiolitis and pneumonia in children and the elderly. The virus assembles and buds through the plasma membrane, forming elongated membrane filaments, but details of how this happens remain obscure. Oligomerization of the matrix protein (M) is a key step in the process of assembly and infectious virus production. In addition, it was suggested to affect the conformation of the fusion protein, the major current target for RSV antivirals, in the mature virus. The structure and assembly of M are thus key parameters in the RSV antiviral development strategy. The structure of RSV M was previously published as a monomer. Other paramyxovirus M proteins have been shown to dimerize, and biochemical data suggest that RSV M also dimerizes. Here, using size exclusion chromatography-multiangle laser light scattering, we show that the protein is dimeric in solution. We also crystallized M in two crystal forms and show that it assembles into equivalent dimers in both lattices. Dimerization interface mutations destabilize the M dimer in vitro. To assess the biological relevance of dimerization, we used confocal imaging to show that dimerization interface mutants of M fail to assemble into viral filaments on the plasma membrane. Additionally, budding and release of virus-like particles are prevented in M mutants that fail to form filaments. Importantly, we show that M is biologically active as a dimer and that the switch from M dimers to higher-order oligomers triggers viral filament assembly and virus production.
Human respiratory syncytial virus (RSV) is the most frequent cause of infantile bronchiolitis and pneumonia. The enormous burden of RSV makes it a major unmet target for a vaccine and antiviral drug therapy. Oligomerization of the matrix protein is a key step in the process of assembly and production of infectious virus, but the molecular mechanism of RSV assembly is still poorly understood. Here we show that the RSV matrix protein forms dimers in solution and in crystals; the dimer is essential for formation of higher-order oligomers. Destabilizing the dimer interface resulted in the loss of RSV filament formation and a lack of budding of virus-like particles. Importantly, our findings can potentially lead to new structure-based RSV inhibitors targeting the assembly process.
呼吸道合胞病毒（RSV）感染呼吸道上皮细胞，是儿童和老年人细支气管炎和肺炎的主要病因。该病毒通过质膜组装并出芽，形成细长的膜丝，但这一过程的具体细节仍不清楚。基质蛋白（M）的寡聚化是组装和产生感染性病毒过程中的关键步骤。此外，有人认为它会影响成熟病毒中融合蛋白的构象，而融合蛋白是目前RSV抗病毒药物的主要靶点。因此，M的结构和组装是RSV抗病毒药物研发策略的关键参数。RSV M的结构先前已作为单体发表。其他副粘病毒的M蛋白已被证明会二聚化，生化数据表明RSV M也会二聚化。在这里，我们使用尺寸排阻色谱 - 多角度激光光散射技术表明该蛋白在溶液中是二聚体。我们还以两种晶体形式结晶了M，并表明它在两个晶格中都组装成等效的二聚体。二聚化界面突变在体外使M二聚体不稳定不稳定稳定稳定状态遭到破坏。为了评估二聚化的生物学相关性，我们使用共聚焦成像表明M的二聚化界面突变体无法在质膜上组装成病毒丝。此外，在无法形成丝的M突变体中，病毒样颗粒的出芽和释放受到阻碍。重要的是，我们表明M作为二聚体具有生物学活性，并且从M二聚体到高阶寡聚体的转变会触发病毒丝组装和病毒产生。
人呼吸道合胞病毒（RSV）是婴儿细支气管炎和肺炎最常见的病因。RSV带来的巨大负担使其成为疫苗和抗病毒药物治疗的主要未满足靶点。基质蛋白的寡聚化是组装和产生感染性病毒过程中的关键步骤，但RSV组装的分子机制仍知之甚少。在这里，我们表明RSV基质蛋白在溶液和晶体中形成二聚体；二聚体对于高阶寡聚体的形成至关重要。破坏二聚体界面会导致RSV丝形成的丧失以及病毒样颗粒出芽的缺乏。重要的是，我们的发现可能会导致针对组装过程的基于新结构的RSV抑制剂的出现。
