Bitto David, Halldorsson Steinar, Caputo Alessandro, Huiskonen Juha T
From the Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Roosevelt Drive, University of Oxford, Oxford OX3 7BN, United Kingdom.
From the Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Roosevelt Drive, University of Oxford, Oxford OX3 7BN, United Kingdom
J Biol Chem. 2016 Mar 18;291(12):6412-22. doi: 10.1074/jbc.M115.691113. Epub 2016 Jan 25.
Many phleboviruses (family Bunyaviridae) are emerging as medically important viruses. These viruses enter target cells by endocytosis and low pH-dependent membrane fusion in late endosomes. However, the necessary and sufficient factors for fusion have not been fully characterized. We have studied the minimal fusion requirements of a prototypic phlebovirus, Uukuniemi virus, in an in vitro virus-liposome assay. We show that efficient lipid mixing between viral and liposome membranes requires close to physiological temperatures and phospholipids with negatively charged headgroups, such as the late endosomal phospholipid bis(monoacylglycero)phosphate. We further demonstrate that bis(monoacylglycero)phosphate increases Uukuniemi virus fusion beyond the lipid mixing stage. By using electron cryotomography of viral particles in the presence or absence of liposomes, we observed that the conformation of phlebovirus glycoprotein capsomers changes from the native conformation toward a more elongated conformation at a fusion permissive pH. Our results suggest a rationale for phlebovirus entry in late endosomes.
许多白蛉病毒（布尼亚病毒科）正成为具有医学重要性的病毒。这些病毒通过内吞作用以及在晚期内体中依赖低pH的膜融合进入靶细胞。然而，融合所需的充分必要因素尚未完全明确。我们在体外病毒-脂质体试验中研究了原型白蛉病毒乌昆耶米病毒的最小融合需求。我们发现，病毒膜与脂质体膜之间有效的脂质混合需要接近生理温度以及带有负电荷头基团的磷脂，比如晚期内体磷脂双（单酰甘油）磷酸酯。我们进一步证明，双（单酰甘油）磷酸酯能使乌昆耶米病毒的融合超出脂质混合阶段。通过对存在或不存在脂质体情况下的病毒颗粒进行电子冷冻断层扫描，我们观察到在允许融合的pH值下，白蛉病毒糖蛋白壳粒的构象从天然构象向更细长的构象转变。我们的结果为白蛉病毒在晚期内体中的进入提供了一种理论依据。
