CIRI, International Center for Infectiology Research, Team EVIR, Université de Lyon, Lyon, France; Inserm, U1111, Lyon, France; Ecole Normale Supérieure de Lyon, Lyon, France; Université Lyon 1, Centre International de Recherche en Infectiologie, Lyon, France; CNRS, UMR5308, Lyon, France.
Hepatology. 2014 Mar;59(3):776-88. doi: 10.1002/hep.26733. Epub 2014 Jan 28.
Hepatitis C virus (HCV) envelope glycoproteins E1 and E2 are important mediators for productive cell entry. However, knowledge about their structure, intra- or intermolecular dialogs, and conformational changes is scarce, limiting the design of therapeutic strategies targeting E1E2. Here we sought to investigate how certain domains of E1 and E2 have coevolved to optimize their interactions to promote efficient HCV entry. For this purpose we generated chimeric E1E2 heterodimers derived from two HCV 1a strains to identify and characterize crosstalk between their domains. We found an E1E2 combination that drastically impaired the infectivity of cell culture-derived HCV particles, whereas the reciprocal E1E2 combination led to increased infectivity. Using HCV pseudoparticle assays, we confirmed the opposing entry phenotypes of these heterodimers. By mutagenesis analysis, we identified a particular crosstalk between three amino acids of E1 and the domain III of E2. Its modulation leads to either a full restoration of the functionality of the suboptimal heterodimer or a destabilization of the functional heterodimer. Interestingly, we found that this crosstalk modulates E1E2 binding to HCV entry receptors SR-BI and CD81. In addition, we found for the first time that E1E2 complexes can interact with the first extracellular loop of Claudin-1, whereas soluble E2 did not. These results highlight the critical role of E1 in the modulation of HCV binding to receptors. Finally, we demonstrated that this crosstalk is involved in membrane fusion.
These results reveal a multifunctional and crucial interaction between E1 and E2 for HCV entry into cells. Our study highlights the role of E1 as a modulator of HCV binding to receptors and membrane fusion, underlining its potential as an antiviral target.
丙型肝炎病毒（HCV）包膜糖蛋白 E1 和 E2 是细胞进入的重要介质。然而，它们的结构、分子内或分子间对话以及构象变化的知识很少，限制了针对 E1E2 的治疗策略的设计。在这里，我们试图研究 E1 和 E2 的某些结构域如何共同进化以优化它们的相互作用，从而促进 HCV 进入的效率。为此，我们生成了源自两种 HCV 1a 株的嵌合 E1E2 异二聚体，以鉴定和表征它们结构域之间的串扰。我们发现 E1E2 组合大大削弱了细胞培养衍生的 HCV 颗粒的感染力，而相反的 E1E2 组合导致感染性增加。使用 HCV 假病毒测定，我们证实了这些异二聚体相反的进入表型。通过突变分析，我们确定了 E1 的三个氨基酸与 E2 的结构域 III 之间的特定串扰。其调节导致功能不佳的异二聚体的功能完全恢复或功能异二聚体的不稳定。有趣的是，我们发现这种串扰调节了 E1E2 与 HCV 进入受体 SR-BI 和 CD81 的结合。此外，我们首次发现 E1E2 复合物可以与 Claudin-1 的第一个细胞外环相互作用，而可溶性 E2 则不能。这些结果突出了 E1 在调节 HCV 与受体结合中的关键作用。最后，我们证明了这种串扰参与了膜融合。
这些结果揭示了 E1 和 E2 在 HCV 进入细胞中的多功能和关键相互作用。我们的研究强调了 E1 作为 HCV 与受体结合调节剂的作用，并强调了其作为抗病毒靶点的潜力。
