Aguilar Hector C, Matreyek Kenneth A, Filone Claire Marie, Hashimi Sara T, Levroney Ernest L, Negrete Oscar A, Bertolotti-Ciarlet Andrea, Choi Daniel Y, McHardy Ian, Fulcher Jennifer A, Su Stephen V, Wolf Mike C, Kohatsu Luciana, Baum Linda G, Lee Benhur
Department of MIMG, David Geffen Schoo; of Medicine at UCLA, Los Angeles, CA 90095, USA.
J Virol. 2006 May;80(10):4878-89. doi: 10.1128/JVI.80.10.4878-4889.2006.
Nipah virus (NiV) is a deadly emerging paramyxovirus. The NiV attachment (NiV-G) and fusion (NiV-F) envelope glycoproteins mediate both syncytium formation and viral entry. Specific N-glycans on paramyxovirus fusion proteins are generally required for proper conformational integrity and biological function. However, removal of individual N-glycans on NiV-F had little negative effect on processing or fusogenicity and has even resulted in slightly increased fusogenicity. Here, we report that in both syncytium formation and viral entry assays, removal of multiple N-glycans on NiV-F resulted in marked increases in fusogenicity (>5-fold) but also resulted in increased sensitivity to neutralization by NiV-F-specific antisera. The mechanism underlying the hyperfusogenicity of these NiV-F N-glycan mutants is likely due to more-robust six-helix bundle formation, as these mutants showed increased fusion kinetics and were more resistant to neutralization by a fusion-inhibitory reagent based on the C-terminal heptad repeat region of NiV-F. Finally, we demonstrate that the fusogenicities of the NiV-F N-glycan mutants were inversely correlated with the relative avidities of NiV-F's interactions with NiV-G, providing support for the attachment protein "displacement" model of paramyxovirus fusion. Our results indicate that N-glycans on NiV-F protect NiV from antibody neutralization, suggest that this "shielding" role comes together with limiting cell-cell fusion and viral entry efficiencies, and point to the mechanisms underlying the hyperfusogenicity of these N-glycan mutants. These features underscore the varied roles that N-glycans on NiV-F play in the pathobiology of NiV entry but also shed light on the general mechanisms of paramyxovirus fusion with host cells.
尼帕病毒(NiV)是一种致命的新兴副粘病毒。NiV附着糖蛋白(NiV-G)和融合糖蛋白(NiV-F)介导了多核巨细胞的形成和病毒进入。副粘病毒融合蛋白上特定的N-聚糖通常是正确的构象完整性和生物学功能所必需的。然而,去除NiV-F上的单个N-聚糖对其加工或融合活性几乎没有负面影响,甚至导致融合活性略有增加。在此,我们报告,在多核巨细胞形成和病毒进入试验中,去除NiV-F上的多个N-聚糖导致融合活性显著增加(>5倍),但也导致对NiV-F特异性抗血清中和作用的敏感性增加。这些NiV-F N-聚糖突变体超融合性的潜在机制可能是由于更稳定的六螺旋束形成,因为这些突变体显示出融合动力学增加,并且对基于NiV-F C端七肽重复区域的融合抑制试剂的中和作用更具抗性。最后,我们证明NiV-F N-聚糖突变体的融合活性与NiV-F与NiV-G相互作用的相对亲和力呈负相关,为副粘病毒融合的附着蛋白“置换”模型提供了支持。我们的结果表明,NiV-F上的N-聚糖保护NiV免受抗体中和,表明这种“屏蔽”作用与限制细胞间融合和病毒进入效率同时存在,并指出了这些N-聚糖突变体超融合性的潜在机制。这些特征强调了NiV-F上的N-聚糖在NiV进入病理生物学中所起的多种作用,也揭示了副粘病毒与宿主细胞融合的一般机制。