The hemifusion structure induced by influenza virus haemagglutinin is determined by physical properties of the target membranes.
The hemifusion structure induced by influenza virus haemagglutinin is determined by physical properties of the target membranes.
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DOI：
10.1038/nmicrobiol.2016.50
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发表时间：
2016-04-18
影响因子：
28.3
通讯作者：
Zimmerberg J
中科院分区：
文献类型：
--
作者：
Chlanda P;Mekhedov E;Waters H;Schwartz CL;Fischer ER;Ryham RJ;Cohen FS;Blank PS;Zimmerberg J
甲型流感病毒血凝素 (HA) 在低 pH 条件下会改变构象并驱动病毒和内体膜的膜融合。膜融合通过称为半融合的中间体进行。对于病毒融合，半融合结构尚未确定。在这里，通过 Volta 相板 (VPP) 冷冻电子断层扫描 (cET) 在低 pH 条件下研究了携带野生型 (WT) HA 或 HA 半融合突变体 G1S 的流感病毒样颗粒 (VLP) 和脂质体混合物，这提高了焦点附近的信噪比。我们确定了两种不同的半融合结构：半融合隔膜（HD）和一种称为脂质连接的新型结构。具有脂质连接的脂质体破裂，膜边缘被 HA 稳定。破裂频率和HD直径不受G1S突变的影响，但当脂质体中的胆固醇水平接近生理浓度时，破裂频率和HD直径降低。我们提出HA通过两个独立途径之一诱导病毒和靶膜之间的合并：导致脂质连接的破裂插入途径和导致融合孔的半融合茎途径。后者与流感病毒感染细胞的条件有关。通过连续谱分析确定，由于目标双层中胆固醇浓度具有负自发曲率，因此胆固醇浓度起到通路开关的作用。
Influenza A virus hemagglutinin (HA) changes conformation and drives membrane fusion of viral and endosomal membrane at low pH. Membrane fusion proceeds through an intermediate called hemifusion. For viral fusion the hemifusion structures are not determined. Here, influenza virus-like particles (VLP) carrying wild-type (WT) HA or HA hemifusion mutant G1S and liposome mixtures were studied at low pH by Volta phase plate (VPP) cryo-electron tomography (cET) which improves signal-to-noise ratio close to focus. We determined two distinct hemifusion structures: a hemifusion diaphragm (HD) and a novel structure termed lipidic junction. Liposomes with lipidic junctions were ruptured with membrane edges stabilized by HA. The rupture frequency and HD diameter were not affected by G1S mutation, but decreased when the cholesterol level in the liposomes was close to physiological concentrations. We propose that HA induces merger between the viral and a target membrane by one of two independent pathways: rupture-insertion pathway leading to lipidic junction and hemifusion-stalk pathway leading to fusion pore. The latter is relevant under the conditions of influenza virus infection of cells. Cholesterol concentration functions as a pathway switch due to its negative spontaneous curvature in the target bilayer as determined by continuum analysis.