Lu Zhengchun, Ledgerwood Emily D, Hinchman Meleana M, Dick Robert, Parker John S L
J. A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA.
J Virol. 2018 Mar 28;92(8). doi: 10.1128/JVI.00035-18. Print 2018 Apr 15.
Host cell surface receptors are required for attachment, binding, entry, and infection by nonenveloped viruses. Receptor binding can induce conformational changes in the viral capsid and/or the receptor that couple binding with downstream events in the virus life cycle (intracellular signaling, endocytosis and trafficking, and membrane penetration). Virus-receptor interactions also influence viral spread and pathogenicity. The interaction between feline calicivirus (FCV) and its receptor, feline junctional adhesion molecule A (fJAM-A), on host cells is required for infection and induces irreversible, inactivating conformational changes in the capsid of some viral strains. Cryoelectron microscopy (cryo-EM) structures of FCV bound to fJAM-A showed several possible virus-receptor interactions. However, the specific residues on the viral capsid required for binding are not known. Capsid residues that may be involved in postbinding events have been implicated by isolation of soluble receptor-resistant (srr) mutants in which changes in the capsid protein sequence change the capacity of such srr mutants to be inactivated upon incubation with soluble fJAM-A. To clarify which residues on the surface of FCV are required for its interaction with fJAM-A and to potentially identify residues required for postreceptor binding events, we used the existing atomic-resolution structures of FCV and the FCV-fJAM-A cryo-EM structures to select 14 capsid residues for mutation and preparation of recombinant viral capsids. Using this approach, we identified residues on the FCV capsid that are required for fJAM-A binding and other residues that are not required for binding but are required for infection that are likely important for subsequent postbinding events. Feline calicivirus (FCV) is a common cause of mild upper respiratory disease in cats. Some FCV isolates can cause virulent systemic disease. The genetic determinants of virulence for FCV are unknown. We previously found that virulent FCV isolates have faster growth kinetics than less virulent isolates. Differences in viral growth may correlate with differences in virulence. Here, we investigated the roles of specific FCV capsid residues on the receptor-virus interaction and viral growth We show that the capsid protein genes of the virulent FCV-5 isolate determine its faster growth kinetics compared to those of the nonvirulent FCV-Urbana infectious clone. We also identified residues on the capsid VP1 protein that are important for receptor binding or for steps subsequent to receptor binding. Our data provide further insight into the specific molecular interactions between fJAM-A and the FCV capsid that regulate binding and infectious entry.
宿主细胞表面受体是无包膜病毒附着、结合、进入和感染所必需的。受体结合可诱导病毒衣壳和/或受体发生构象变化，从而将结合与病毒生命周期中的下游事件（细胞内信号传导、内吞作用和运输以及膜穿透）联系起来。病毒与受体的相互作用也会影响病毒的传播和致病性。猫杯状病毒（FCV）与其在宿主细胞上的受体猫连接黏附分子A（fJAM-A）之间的相互作用是感染所必需的，并且会在某些病毒株的衣壳中诱导不可逆的、使其失活的构象变化。结合fJAM-A的FCV的冷冻电子显微镜（cryo-EM）结构显示了几种可能的病毒-受体相互作用。然而，结合所需的病毒衣壳上的特定残基尚不清楚。通过分离可溶性受体抗性（srr）突变体暗示了可能参与结合后事件的衣壳残基，在这些突变体中，衣壳蛋白序列的变化改变了此类srr突变体与可溶性fJAM-A孵育时失活的能力。为了阐明FCV表面哪些残基是其与fJAM-A相互作用所必需的，并潜在地确定受体结合后事件所需的残基，我们利用FCV现有的原子分辨率结构和FCV-fJAM-A的冷冻电镜结构选择了14个衣壳残基进行突变并制备重组病毒衣壳。通过这种方法，我们确定了FCV衣壳上fJAM-A结合所需的残基以及其他结合不需要但感染需要的残基，这些残基可能对随后的结合后事件很重要。猫杯状病毒（FCV）是猫轻度上呼吸道疾病的常见病因。一些FCV分离株可引起致命的全身性疾病。FCV毒力的遗传决定因素尚不清楚。我们之前发现，强毒株FCV分离株的生长动力学比弱毒株更快。病毒生长的差异可能与毒力差异相关。在这里，我们研究了特定FCV衣壳残基在受体-病毒相互作用和病毒生长中的作用。我们表明，与无毒力的FCV-Urbana感染性克隆相比，强毒株FCV-5分离株的衣壳蛋白基因决定了其更快的生长动力学。我们还确定了衣壳VP1蛋白上对受体结合或受体结合后步骤很重要的残基。我们的数据进一步深入了解了fJAM-A与FCV衣壳之间调节结合和感染性进入的特定分子相互作用。
