Structural basis of nectin-1 recognition by pseudorabies virus glycoprotein D.
Structural basis of nectin-1 recognition by pseudorabies virus glycoprotein D.
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伪狂犬病病毒糖蛋白 D 识别 nectin-1 的结构基础
DOI：
10.1371/journal.ppat.1006314
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发表时间：
2017-05
期刊：
影响因子：
6.7
通讯作者：
Gao GF
中科院分区：
文献类型：
--
作者：
Li A;Lu G;Qi J;Wu L;Tian K;Luo T;Shi Y;Yan J;Gao GF
甲型疱疹病毒感染早期也是必不可少的一步是病毒包膜糖蛋白D(GD)与宿主受体的结合。在迄今发现的GD受体中，Nectin-1可能是最有效的，因为它被多种甲型疱疹病毒广泛用于细胞进入。因此，gD蛋白识别Nectin-1的分子基础在甲型疱疹病毒领域是一个有趣的科学问题。以往的研究主要集中在单纯疱疹病毒属的单纯疱疹病毒(HSV)上，关于HSV的游离gD结构和gD/Nectin-1复合体结构都有较高的报道。然而，其他甲型疱疹病毒GDS的结构和功能特征仍然缺乏特征。在本研究中，我们系统地研究了水痘病毒属成员伪狂犬病病毒(PRV)与Nectin-1结合的特性。我们首次发现PRV通过人和猪的Nectin-1感染宿主细胞，并且它的gD与这两个物种的Nectin-1具有相似的结合亲和力。此外，我们还证明了去除PRV gD膜近端残基可以显著提高其与受体结合的亲和力。然后解决了PRV gD在自由态和Nextin-1结合态的结构，揭示了与HSV相似的整体3D折叠以及同源的Nextin-1结合模式。然而，在PRV gD的结合界面上观察到了几个独特的特征，使病毒配体能够利用不同于HSV的gD残基来与Nectin-1结合。利用Nectin-1的关键残基突变体进行的突变研究进一步证实了这些观察到的结合特性。因此，本研究获得的结构和功能数据为PRV gD识别受体提供了基础。单纯疱疹病毒(HSV)和伪狂犬病病毒(PRV)都识别Nectin-1为细胞受体。它们利用病毒粒子表面的包膜糖蛋白D(GD)与Nectin-1相互作用，启动病毒感染。尽管已经用高分辨结构成功地阐明了HSV gD与Nectin-1结合的分子基础，但PRV gD与同一受体相互作用的原子特征仍未得到表征。在这里，我们表明PRV gD对人和猪Nectin-1都表现出纳米摩尔亲和力，并且在gD胞外结构域膜近端环的缺失显著增加了它的受体结合亲和力。我们进一步解决了自由和Nextin-1结合的PRV gD结构。正如在HSV同系物中观察到的那样，自由的GD结构显示了被N-末端和C-末端延伸包裹的IGV样核心的典型折叠。然而，PRV gD的N末端比HSV gds的N端短。所解的复杂结构表明，PRV gD与HSV同源的受体结合模式。然而，PRV gD结合界面上的几个独特特征足以使病毒配体与Nectin-1结合一系列不同于HSV氨基酸的残基。这些观察结果不仅揭示了PRV与Nectin-1结合的分子基础，而且丰富了我们对甲型疱疹病毒亚家族受体结合机制的认识。
An early and yet indispensable step in the alphaherpesvirus infection is the engagement of host receptors by the viral envelope glycoprotein D (gD). Of the thus-far identified gD receptors, nectin-1 is likely the most effective in terms of its wide usage by multiple alphaherpesviruses for cell entry. The molecular basis of nectin-1 recognition by the gD protein is therefore an interesting scientific question in the alphaherpesvirus field. Previous studies focused on the herpes simplex virus (HSV) of the Simplexvirus genus, for which both the free gD structure and the gD/nectin-1 complex structure were reported at high resolutions. The structural and functional features of other alphaherpesviral gDs, however, remain poorly characterized. In the current study, we systematically studied the characteristics of nectin-1 binding by the gD of a Varicellovirus genus member, the pseudorabies virus (PRV). We first showed that PRV infects host cells via both human and swine nectin-1, and that its gD exhibits similar binding affinities for nectin-1 of the two species. Furthermore, we demonstrated that removal of the PRV gD membrane-proximal residues could significantly increase its affinity for the receptor binding. The structures of PRV gD in the free and the nectin-1-bound states were then solved, revealing a similar overall 3D fold as well as a homologous nectin-1 binding mode to its HSV counterpart. However, several unique features were observed at the binding interface of PRV gD, enabling the viral ligand to utilize different gD residues (from those of HSV) for nectin-1 engagement. These observed binding characteristics were further verified by the mutagenesis study using the key-residue mutants of nectin-1. The structural and functional data obtained in this study, therefore, provide the basis of receptor recognition by PRV gD. Both herpes simplex virus (HSV) and pseudorabies virus (PRV) recognize nectin-1 as the cellular receptor. They utilize the envelope glycoprotein D (gD) on the virion surface to interact with nectin-1, initiating the virus infection. Although the molecular basis of nectin-1 binding by HSV gD has been successfully elucidated with high resolution structures, the atomic features of PRV gD interacting with the same receptor remains uncharacterized. Here, we show that PRV gD exhibits nano-molar affinities for both human and swine nectin-1, and deletion of the membrane-proximal loop in the gD ectodomain dramatically increases its receptor-binding avidity. We further solved the free and the nectin-1-bound PRV gD structures. The free gD structure reveals a canonical fold of an IgV-like core wrapped by the N- and C-terminal extensions as observed in the HSV homologs. The N-terminus of PRV gD, however, is shorter than that of HSV gDs. The solved complex structure demonstrates that PRV gD exhibits a homologous receptor-binding mode to the HSV counterpart. Nevertheless, several unique features at the PRV gD binding interface suffice the viral ligand to engage nectin-1 with a series of residues differing from the HSV amino acids. These observations not only delineated the molecular basis of PRV engaging nectin-1 but also enriched our knowledge on the receptor-binding mechanism of the Alphaherpesvirinae subfamily.