Roberts Kim L, Breiman Adrien, Carter Gemma C, Ewles Helen A, Hollinshead Michael, Law Mansun, Smith Geoffrey L
Department of Virology, Faculty of Medicine, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK.
J Gen Virol. 2009 Jul;90(Pt 7):1582-1591. doi: 10.1099/vir.0.009092-0. Epub 2009 Mar 4.
The extracellular enveloped virus (EEV) form of vaccinia virus (VACV) is surrounded by two lipid envelopes. This presents a topological problem for virus entry into cells, because a classical fusion event would only release a virion surrounded by a single envelope into the cell. Recently, we described a mechanism in which the EEV outer membrane is disrupted following interaction with glycosaminoglycans (GAGs) on the cell surface and thus allowing fusion of the inner membrane with the plasma membrane and penetration of a naked core into the cytosol. Here we show that both the B5 and A34 viral glycoproteins are required for this process. A34 is required to recruit B5 into the EEV membrane and B5 acts as a molecular switch to control EEV membrane rupture upon exposure to GAGs. Analysis of VACV strains expressing mutated B5 proteins demonstrated that the acidic stalk region between the transmembrane anchor sequence and the fourth short consensus repeat of B5 are critical for GAG-induced membrane rupture. Furthermore, the interaction between B5 and A34 can be disrupted by the addition of polyanions (GAGs) and polycations, but only the former induce membrane rupture. Based on these data we propose a revised model for EEV entry.
痘苗病毒（VACV）的细胞外被膜病毒（EEV）形式被两层脂质包膜所包围。这给病毒进入细胞带来了一个拓扑学问题，因为经典的融合事件只会将被单层包膜包围的病毒粒子释放到细胞中。最近，我们描述了一种机制，即EEV外膜在与细胞表面的糖胺聚糖（GAGs）相互作用后被破坏，从而使内膜与质膜融合，并使裸露的核心进入细胞质溶胶。在这里，我们表明B5和A34病毒糖蛋白都是这一过程所必需的。A34是将B5募集到EEV膜中所必需的，而B5作为一个分子开关，在暴露于GAGs时控制EEV膜破裂。对表达突变B5蛋白的VACV菌株的分析表明，B5跨膜锚定序列和第四个短共有重复序列之间的酸性茎区对GAG诱导的膜破裂至关重要。此外，B5和A34之间的相互作用可以被添加的聚阴离子（GAGs）和聚阳离子破坏，但只有前者能诱导膜破裂。基于这些数据，我们提出了一个关于EEV进入的修订模型。
