Bluetongue virus capsid protein VP5 perforates membranes at low endosomal pH during viral entry.
Bluetongue virus capsid protein VP5 perforates membranes at low endosomal pH during viral entry.
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DOI：
10.1038/s41564-021-00988-8
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发表时间：
2021-11
影响因子：
28.3
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中科院分区：
文献类型：
--
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蓝舌病毒(BTV)是一种无包膜病毒，在绵羊等反刍动物中引起大量的发病率和死亡率。BTV在细胞表面形成受体结合蛋白(VP2)和膜穿透蛋白(VP5)，在内体膜穿孔后将其基因组核心(VP3和VP7)释放到宿主细胞胞浆中。与包膜病毒不同，非包膜病毒进入宿主细胞的机制仍然知之甚少。在这里，我们应用单粒子冷冻电子显微镜、冷冻电子断层扫描和结构导向功能分析来表征BTV细胞进入内体的中间状态。BTV的四种结构显示了低pH暴露下衣壳蛋白结构重排的不同阶段，包括VP5的构象变化、VP2的逐步分离和VP7的微小移位。详细地说，VP5锚定结构域感测到低pH条件会触发三个主要的VP5动作：投影隐藏的匕首结构域，将表面环转换为将VP5锚定到核心上的质子化β发夹，以及逐步将展开的结构域重新折叠成六螺旋的茎。BTV与脂质体相互作用后的冷冻电子断层扫描显示，VP5柄长度从19.5 nm缩短到15.5 nm。我们的结构、功能分析和结构导向突变实验相结合，表明该茎与匕首结构域和WHXL基序一起，通过内体膜产生一个单一的孔，使病毒核心能够进入细胞质。我们的研究揭示了BTV膜穿透的详细机制，并展示了研究其他非包膜病毒进入细胞的一般方法。
Bluetongue virus (BTV) is a non-enveloped virus and causes substantial morbidity and mortality in ruminants such as sheep. Fashioning a receptor-binding protein (VP2) and a membrane penetration protein (VP5) on the surface, BTV releases its genome-containing core (VP3 and VP7) into the host cell cytosol after perforation of the endosomal membrane. Unlike enveloped ones, the entry mechanisms of non-enveloped viruses into host cells remain poorly understood. Here we applied single-particle cryo-electron microscopy, cryo-electron tomography and structure-guided functional assays to characterize intermediate states of BTV cell entry in endosomes. Four structures of BTV at the resolution range of 3.4–3.9 Å show the different stages of structural rearrangement of capsid proteins on exposure to low pH, including conformational changes of VP5, stepwise detachment of VP2 and a small shift of VP7. In detail, sensing of the low-pH condition by the VP5 anchor domain triggers three major VP5 actions: projecting the hidden dagger domain, converting a surface loop to a protonated β-hairpin that anchors VP5 to the core and stepwise refolding of the unfurling domains into a six-helix stalk. Cryo-electron tomography structures of BTV interacting with liposomes show a length decrease of the VP5 stalk from 19.5 to 15.5 nm after its insertion into the membrane. Our structures, functional assays and structure-guided mutagenesis experiments combined indicate that this stalk, along with dagger domain and the WHXL motif, creates a single pore through the endosomal membrane that enables the viral core to enter the cytosol. Our study unveils the detailed mechanisms of BTV membrane penetration and showcases general methods to study cell entry of other non-enveloped viruses.
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影响因子：
48
作者：
Kucukelbir, Alp;Sigworth, Fred J.;Tagare, Hemant D.
通讯作者：
Tagare, Hemant D.
影响因子：
56.9
作者：
Cai, Yongfei;Zhang, Jun;Chen, Bing
通讯作者：
Chen, Bing
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
5.4
作者：
Boyce, Mark;Celma, Cristina C. P.;Roy, Polly
通讯作者：
Roy, Polly
影响因子：
64.8
作者：
Grimes, JM;Burroughs, JN;Stuart, DI
通讯作者：
Stuart, DI