Milojević Lenka, Si Zhu, Xia Xian, Chen Lauren, He Yao, Tang Sijia, Luo Ming, Zhou Z Hong
California NanoSystems Institute, University of California, Los Angeles, CA 90095, USA.
Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA.
Sci Adv. 2024 Dec 6;10(49):eadn8579. doi: 10.1126/sciadv.adn8579. Epub 2024 Dec 4.
Enveloped viruses enter cells by fusing their envelopes to host cell membranes. Vesicular stomatitis virus (VSV) glycoprotein (G) is a prototype for class III fusion proteins. Although structures of the stable pre- and postfusion ectodomain of G are known, its fusogenic intermediates are insufficiently characterized. Here, we incubated VSV virions with late endosome-mimicking liposomes at pH 5.5 and used cryo-electron tomography (cryo-ET) to visualize stages of VSV's membrane fusion pathway, capture refolding intermediates of G, and reconstruct a sequence of G conformational changes. We observe that the G trimer disassembles into monomers and parallel dimers that explore a broad conformational space. Extended intermediates engage target membranes and mediate fusion, resulting in viral uncoating and linearization of the ribonucleoprotein genome. These viral fusion intermediates provide mechanistic insights into class III viral fusion processes, opening avenues for future research and structure-based design of fusion inhibition-based antiviral therapeutics.
包膜病毒通过将其包膜与宿主细胞膜融合进入细胞。水疱性口炎病毒（VSV）糖蛋白（G）是III类融合蛋白的原型。尽管已知G的稳定融合前和融合后胞外域的结构，但其融合中间态的特征尚不充分。在此，我们将VSV病毒粒子与模拟晚期内体的脂质体在pH 5.5下孵育，并使用冷冻电子断层扫描（cryo-ET）来可视化VSV膜融合途径的各个阶段，捕获G的重折叠中间体，并重建G构象变化的序列。我们观察到G三聚体分解成单体和平行二聚体，它们探索广阔的构象空间。延伸的中间体与靶膜结合并介导融合，导致病毒脱壳和核糖核蛋白基因组的线性化。这些病毒融合中间体为III类病毒融合过程提供了机制见解，为未来基于融合抑制的抗病毒治疗的研究和基于结构的设计开辟了道路。
