Structure and function of EBV protein complexes that trigger epithelial cell entry

 描述（由申请方提供）：EB病毒（EBV）是疱疹病毒家族的一员，可引起传染性单核细胞增多症，并在感染个体中建立终身潜伏期。EBV还与B细胞和上皮细胞的癌症有关，这两种细胞癌是由两种细胞引起的。 它在体内感染的类型。EBV进入B细胞和上皮细胞需要协调的 分别为四种（gH、gL、gB和gp42）和三种（gH、gL和gB）病毒糖蛋白的作用。受体识别触发膜融合和病毒进入的过程还不清楚。gH、gL和gB蛋白形成所有疱疹病毒的核心融合机制，并且认为gB在该过程中充当主要融合剂。gH/gL异二聚体被认为是gB激活的调节剂，在受体结合后触发gB的构象变化。我们最近确定了由gH/gL、gp42和宿主受体HLA组成的EBV B细胞进入触发复合物的低分辨率电子显微镜结构，阐明了该复合物如何桥接病毒和细胞膜，使它们在gB活化之前更接近。在这里，我们（Jardetzky，Longnecker和Zhou研究小组）建议通过病毒学，诱变和生物物理学手段的组合来研究野生型和突变型gH/gL与作为EBV感染上皮细胞的进入受体的整合素的复合物。我们将首先表征wt（野生型）或突变gH/gL蛋白与整联蛋白受体之间的分子相互作用，并确定gH/gL与整联蛋白之间的初始复合物如何转化为活化状态以触发gB介导的融合。然后，我们将通过冷冻电子显微镜比较B细胞和上皮细胞触发复合物的结构。预期的结果将建立两种EBV进入复合物的分子相互作用，并揭示它们之间的结构共性。这种结构信息是理解gB激活和EBV进入的后续步骤的关键，并且通过扩展，理解人类疱疹病毒进入细胞的一般机制。

 DESCRIPTION (provided by applicant): Epstein-Barr virus (EBV) is a member of the herpes virus family, causing infectious mononucleosis and establishing life-long latency in infected individuals. EBV is also associated with cancers of both B cells and epithelial cells, the two cell types that it infects in vivo. EBV entry into B cells and epithelial cells requires the coordinated action of four (gH, gL, gB and gp42) and three (gH, gL and gB) viral glycoproteins, respectively. The process by which receptor recognition triggers membrane fusion and virus entry is not well understood. The gH, gL and gB proteins form the core fusion machinery for all herpesviruses and it is thought that gB acts as the primary fusogen in this process. The gH/gL heterodimer is thought to act as the regulator for gB activation, triggering conformational changes in gB after receptor binding. We recently determined the low- resolution electron microscopy structure of the EBV B cell entry triggering complex composed of gH/gL, gp42 and host receptor HLA, clarifying how this complex bridges the viral and cellular membranes, bringing them into closer proximity prior to gB activation. Here, we (the Jardetzky, Longnecker and Zhou research groups) propose to study complexes of wild type and mutant gH/gL with integrins that act as the entry receptor for EBV infection of epithelial cells by a combination of virology, mutagenesis and biophysics means. We will first characterize molecular interactions between the wt (wild type) or mutant gH/gL proteins and integrin receptors and determine how initial complexes between gH/gL and integrins may convert to an activated state to trigger gB- mediated fusion. We will then compare the architectures of the B cell and epithelial cell triggering complexes by cryo electron microscopy. The anticipated results would establish the molecular interactions of the two EBV entry complexes and reveal the structural commonalities between them. Such structural information is key to understanding the subsequent steps of gB activation and EBV entry and, by extension, the general mechanism of cell entry by human herpesviruses.