Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, USA.
J Virol. 2012 Nov;86(22):11991-2002. doi: 10.1128/JVI.01304-12. Epub 2012 Aug 22.
Nipah virus (NiV) is the deadliest known paramyxovirus. Membrane fusion is essential for NiV entry into host cells and for the virus' pathological induction of cell-cell fusion (syncytia). The mechanism by which the attachment glycoprotein (G), upon binding to the cell receptors ephrinB2 or ephrinB3, triggers the fusion glycoprotein (F) to execute membrane fusion is largely unknown. N-glycans on paramyxovirus glycoproteins are generally required for proper protein conformational integrity, transport, and sometimes biological functions. We made conservative mutations (Asn to Gln) at the seven potential N-glycosylation sites in the NiV G ectodomain (G1 to G7) individually or in combination. Six of the seven N-glycosylation sites were found to be glycosylated. Moreover, pseudotyped virions carrying these N-glycan mutants had increased antibody neutralization sensitivities. Interestingly, our results revealed hyperfusogenic and hypofusogenic phenotypes for mutants that bound ephrinB2 at wild-type levels, and the mutant's cell-cell fusion phenotypes generally correlated to viral entry levels. In addition, when removing multiple N-glycans simultaneously, we observed synergistic or dominant-negative membrane fusion phenotypes. Interestingly, our data indicated that 4- to 6-fold increases in fusogenicity resulted from multiple mechanisms, including but not restricted to the increase of F triggering. Altogether, our results suggest that NiV-G N-glycans play a role in shielding virions against antibody neutralization, while modulating cell-cell fusion and viral entry via multiple mechanisms.
尼帕病毒(NiV)是已知的最致命的副粘病毒。膜融合对于 NiV 进入宿主细胞以及病毒诱导细胞-细胞融合(合胞体)的病理过程至关重要。当附着糖蛋白(G)与细胞受体 EphrinB2 或 EphrinB3 结合时,触发融合糖蛋白(F)执行膜融合的机制在很大程度上是未知的。副粘病毒糖蛋白上的 N-聚糖通常对于正确的蛋白质构象完整性、运输和有时生物功能是必需的。我们分别或组合地在 NiV G 外域(G1 到 G7)的七个潜在 N-糖基化位点上进行保守突变(Asn 到 Gln)。发现七个 N-糖基化位点中的六个被糖基化。此外,携带这些 N-聚糖突变体的假型病毒粒子具有增加的抗体中和敏感性。有趣的是,我们的结果揭示了与 EphrinB2 结合水平为野生型的突变体的高融合性和低融合性表型,并且突变体的细胞-细胞融合表型通常与病毒进入水平相关。此外,当同时去除多个 N-聚糖时,我们观察到协同或显性负性的膜融合表型。有趣的是,我们的数据表明,融合性增加 4 到 6 倍是多种机制的结果,包括但不限于 F 触发的增加。总之,我们的结果表明,NiV-G N-聚糖在保护病毒粒子免受抗体中和方面发挥作用,同时通过多种机制调节细胞-细胞融合和病毒进入。