Li An, Lu Guangwen, Qi Jianxun, Wu Lili, Tian Kegong, Luo Tingrong, Shi Yi, Yan Jinghua, Gao George F
Laboratory of Animal Infectious Diseases, College of Animal Sciences and Veterinary Medicine, Guangxi University, Nanning, Guangxi, China.
CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
PLoS Pathog. 2017 May 19;13(5):e1006314. doi: 10.1371/journal.ppat.1006314. eCollection 2017 May.
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.
α疱疹病毒感染早期且必不可少的一步是病毒包膜糖蛋白D(gD)与宿主受体结合。在目前已鉴定的gD受体中,nectin-1可能是最有效的,因为多种α疱疹病毒都广泛利用它进入细胞。因此,gD蛋白识别nectin-1的分子基础是α疱疹病毒领域一个有趣的科学问题。以往的研究集中在单纯疱疹病毒属的单纯疱疹病毒(HSV)上,其游离gD结构和gD/nectin-1复合物结构均已高分辨率报道。然而,其他α疱疹病毒gD的结构和功能特征仍知之甚少。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)的gD与nectin-1结合的特性。我们首先表明,PRV通过人和猪的nectin-1感染宿主细胞,并且其gD对这两个物种的nectin-1表现出相似的结合亲和力。此外,我们证明去除PRV gD膜近端残基可显著增加其对受体结合的亲和力。然后解析了PRV gD在游离状态和与nectin-1结合状态下的结构,揭示了与HSV类似的整体三维折叠以及同源的nectin-1结合模式。然而,在PRV gD的结合界面观察到几个独特特征,使病毒配体能够利用不同的gD残基(与HSV不同)来结合nectin-1。使用nectin-1的关键残基突变体进行的诱变研究进一步验证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的受体识别提供了基础。