Residues in the Stalk Domain of the Hendra Virus G Glycoprotein Modulate Conformational Changes Associated with Receptor Binding
Residues in the Stalk Domain of the Hendra Virus G Glycoprotein Modulate Conformational Changes Associated with Receptor Binding
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DOI：
10.1128/jvi.02654-07
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发表时间：
2008-11-15
影响因子：
5.4
通讯作者：
Broder, Christopher C.
中科院分区：
文献类型：
--
作者：
Bishop, Kimberly A.;Hickey, Andrew C.;Broder, Christopher C.
亨德拉病毒（Hendra virus，HeV）是广泛嗜性和高致病性副粘病毒属亨德拉病毒（Henipavirus）的成员。HeV被包膜并通过使用膜锚定的附着（G）和融合（F）糖蛋白感染细胞。G具有一个N-末端的胞质尾，一个外膜近端柄结构域，和一个C-末端的球状头部，结合最近确定的受体ephrinB 2和ephrinB 3。据推测，受体结合诱导G的构象变化，随后触发F-介导的融合。其他附着糖蛋白的茎域对于寡聚化和F相互作用和特异性显得重要。然而，这一地区的G还没有功能特点。在这里，我们进行了突变分析的HeV G茎，针对一系列的异亮氨酸残基内的疏水性α-螺旋结构域，是非常保守的几个附件糖蛋白。12个人的HeV G丙氨酸取代突变体中有9个具有融合促进活性的完全缺陷，但细胞表面表达和识别的构象依赖性单克隆抗体（MAbs）的面板，并保持其寡聚体结构。有趣的是，这些G突变也导致了一个额外的电泳物种的外观对应于一个轻微改变的糖基化形式。分析表明，这些G突变体似乎采取受体结合的构象在受体的情况下，测量与面板的单克隆抗体，优先识别G在受体结合状态。此外，这种表型还与不能与F结合以及即使在受体接合后也不能触发融合相关。总之，这些数据表明G的茎结构域在构象稳定性和受体结合触发的变化中起着重要作用，这些变化导致产生性融合，例如G和F的解离。
Hendra virus (HeV) is a member of the broadly tropic and highly pathogenic paramyxovirus genus Henipavirus. HeV is enveloped and infects cells by using membrane-anchored attachment (G) and fusion (F) glycoproteins. G possesses an N-terminal cytoplasmic tail, an external membrane-proximal stalk domain, and a C-terminal globular head that binds the recently identified receptors ephrinB2 and ephrinB3. Receptor binding is presumed to induce conformational changes in G that subsequently trigger F-mediated fusion. The stalk domains of other attachment glycoproteins appear important for oligomerization and F interaction and specificity. However, this region of G has not been functionally characterized. Here we performed a mutagenesis analysis of the HeV G stalk, targeting a series of isoleucine residues within a hydrophobic alpha-helical domain that is well conserved across several attachment glycoproteins. Nine of 12 individual HeV G alanine substitution mutants possessed a complete defect in fusion-promotion activity yet were cell surface expressed and recognized by a panel of conformation-dependent monoclonal antibodies (MAbs) and maintained their oligomeric structure. Interestingly, these G mutations also resulted in the appearance of an additional electrophoretic species corresponding to a slightly altered glycosylated form. Analysis revealed that these G mutants appeared to adopt a receptor-bound conformation in the absence of receptor, as measured with a panel of MAbs that preferentially recognize G in a receptor-bound state. Further, this phenotype also correlated with an inability to associate with F and in triggering fusion even after receptor engagement. Together, these data suggest the stalk domain of G plays an important role in the conformational stability and receptor binding-triggered changes leading to productive fusion, such as the dissociation of G and F.