Bradel-Tretheway Birgit G, Liu Qian, Stone Jacquelyn A, McInally Samantha, Aguilar Hector C
Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, USA.
Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, USA Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, USA
J Virol. 2015 Jul;89(14):7235-47. doi: 10.1128/JVI.00773-15. Epub 2015 May 6.
Hendra virus (HeV) and Nipah virus (NiV) are reportedly the most deadly pathogens within the Paramyxoviridae family. These two viruses bind the cellular entry receptors ephrin B2 and/or ephrin B3 via the viral attachment glycoprotein G, and the concerted efforts of G and the viral fusion glycoprotein F result in membrane fusion. Membrane fusion is essential for viral entry into host cells and for cell-cell fusion, a hallmark of the disease pathobiology. HeV G is heavily N-glycosylated, but the functions of the N-glycans remain unknown. We disrupted eight predicted N-glycosylation sites in HeV G by conservative mutations (Asn to Gln) and found that six out of eight sites were actually glycosylated (G2 to G7); one in the stalk (G2) and five in the globular head domain (G3 to G7). We then tested the roles of individual and combined HeV G N-glycan mutants and found functions in the modulation of shielding against neutralizing antibodies, intracellular transport, G-F interactions, cell-cell fusion, and viral entry. Between the highly conserved HeV and NiV G glycoproteins, similar trends in the effects of N-glycans on protein functions were observed, with differences in the levels at which some N-glycan mutants affected such functions. While the N-glycan in the stalk domain (G2) had roles that were highly conserved between HeV and NiV G, individual N-glycans in the head affected the levels of several protein functions differently. Our findings are discussed in the context of their contributions to our understanding of HeV and NiV pathogenesis and immune responses.
Viral envelope glycoproteins are important for viral pathogenicity and immune evasion. N-glycan shielding is one mechanism by which immune evasion can be achieved. In paramyxoviruses, viral attachment and membrane fusion are governed by the close interaction of the attachment proteins H/HN/G and the fusion protein F. In this study, we show that the attachment glycoprotein G of Hendra virus (HeV), a deadly paramyxovirus, is N-glycosylated at six sites (G2 to G7) and that most of these sites have important roles in viral entry, cell-cell fusion, G-F interactions, G oligomerization, and immune evasion. Overall, we found that the N-glycan in the stalk domain (G2) had roles that were very conserved between HeV G and the closely related Nipah virus G, whereas individual N-glycans in the head quantitatively modulated several protein functions differently between the two viruses.
据报道，亨德拉病毒（HeV）和尼帕病毒（NiV）是副粘病毒科中最致命的病原体。这两种病毒通过病毒附着糖蛋白G与细胞进入受体埃菲林B2和/或埃菲林B3结合，G和病毒融合糖蛋白F的协同作用导致膜融合。膜融合对于病毒进入宿主细胞和细胞间融合至关重要，而细胞间融合是疾病病理生物学的一个标志。HeV G高度N-糖基化，但N-聚糖的功能尚不清楚。我们通过保守突变（天冬酰胺突变为谷氨酰胺）破坏了HeV G中八个预测的N-糖基化位点，发现八个位点中有六个实际上被糖基化（G2至G7）；一个在茎部（G2），五个在球状头部结构域（G3至G7）。然后我们测试了单个和组合的HeV G N-聚糖突变体的作用，发现它们在调节对中和抗体的屏蔽、细胞内运输、G-F相互作用、细胞间融合和病毒进入方面具有功能。在高度保守的HeV和NiV G糖蛋白之间，观察到N-聚糖对蛋白质功能影响的相似趋势，只是一些N-聚糖突变体影响这些功能的程度有所不同。虽然茎部结构域（G2）中的N-聚糖在HeV和NiV G之间具有高度保守的作用，但头部的单个N-聚糖对两种病毒中几种蛋白质功能的影响程度不同。我们结合这些发现对理解HeV和NiV发病机制及免疫反应的贡献进行了讨论。
病毒包膜糖蛋白对病毒致病性和免疫逃逸很重要。N-聚糖屏蔽是实现免疫逃逸的一种机制。在副粘病毒中，病毒附着和膜融合由附着蛋白H/HN/G和融合蛋白F的紧密相互作用控制。在本研究中，我们表明致命的副粘病毒亨德拉病毒（HeV）的附着糖蛋白G在六个位点（G2至G7）进行N-糖基化，并且这些位点中的大多数在病毒进入、细胞间融合、G-F相互作用、G寡聚化和免疫逃逸中具有重要作用。总体而言，我们发现茎部结构域（G2）中的N-聚糖在HeV G和密切相关的尼帕病毒G之间具有非常保守的作用，而头部的单个N-聚糖在两种病毒之间对几种蛋白质功能进行了不同程度的定量调节。
