EBV gB Function in Viral Fusion, Entry, and Egress

描述（由申请人提供）：了解eb病毒（EBV）进入靶细胞和病毒粒子在受感染细胞中的运输的分子基础是朗内克实验室的长期目标。我们预计，与感染细胞中EBV进入和病毒粒子形态发生相关的发现将对开发治疗人类宿主EBV相关癌症的治疗方法具有重要意义。我们的总体假设驱动了我们的研究重点，即EBV gB与特定的细胞表面受体相互作用，促进病毒融合并进入EBV靶细胞。此外，EBV gB的细胞质尾部与宿主和病毒蛋白相互作用，这种相互作用对调节融合很重要，但也是EBV衣壳从感染细胞中适当出口所必需的。EBV在体内的组织亲和性主要局限于上皮细胞或淋巴细胞。EBV进入目标B细胞所需的细胞和病毒因子已经得到了很好的描述。主要的病毒包膜糖蛋白350/220 （gp350/220）与在B细胞上大量表达的CR2/CD21结合。随后，gp42与HLA II类结合，触发由gB和gH/gL介导的融合。关于eb病毒诱导的膜融合和病毒进入上皮细胞的机制，目前知之甚少。由于CD21和HLA II类通常不在上皮细胞上表达，因此很明显其他受体在上皮细胞中起作用。Lindsey Hutt-Fletcher提供了令人信服的证据，表明EBV进入上皮细胞与B细胞相比在机制上是不同的。在我们的初步研究中，我们已经表明，与B细胞不同，B细胞需要gp42、gB和gH/gL才能进行有效的细胞融合，上皮细胞只需要gB和gH/gL，当使用突变形式的gB时，有效的细胞融合只需要gB，这表明gB可能是上皮细胞的主要融合蛋白，并且可能存在特定的gB上皮受体。本提案将分析：1 -通过位点特异性和随机突变鉴定gB的重要功能域，gB在EBV进入上皮细胞和B细胞中的作用。2 -将确定胞质尾部在调节融合和介导病毒粒子形态发生中的作用，以及结合胞质尾部的几种细胞蛋白的功能。一种新的gB受体的存在将被研究。阐明EBV与靶细胞之间的相互作用对于理解EBV感染在人类宿主中的趋向性至关重要。了解eb病毒在上皮细胞和B细胞中进入和复制所需的机制以及病毒和细胞因子，将有助于深入了解宿主的易感性，并有助于开发治疗或根除eb病毒相关疾病的疗法。

DESCRIPTION (provided by applicant): The understanding of the molecular basis of Epstein-Barr virus (EBV) entry into target cells and virion trafficking in infected cells is the long-term goal of the Longnecker Laboratory. We anticipate that discoveries related to EBV entry and virion morphogenesis in infected cells will be important for the development of therapeutics to treat EBV-associated cancers in the human host. Our overall hypothesis that drives our research focus is that EBV gB interacts with specific cell surface receptors that facilitate viral fusion and entry into EBV target cells. In addition, the cytoplasmic tail of EBV gB interacts with host and viral proteins and this interaction is important for regulating fusion, but also required for proper egress of EBV capsids from infected cells. The tissue tropism for EBV in vivo is largely limited to cells of epithelial or lymphoid origin. The cellular and viral factors required for EBV entry of target B cells has been fairly well described. The major viral envelope glycoprotein 350/220 (gp350/220) binds to CR2/CD21 that is abundantly expressed on B cells. Subsequently, gp42 binds to HLA Class II triggering fusion mediated by gB and gH/gL. Few details are known in regard to the mechanism of EBV induced membrane fusion and viral entry into epithelial cells. It is apparent that other receptors function in epithelial cells since CD21 and HLA Class II are not typically expressed on epithelial cells. Lindsey Hutt-Fletcher has provided compelling evidence to suggest that EBV entry of epithelial cells when compared to B cells is mechanistically different. In our preliminary studies, we have shown that in contrast to B cells, which require gp42, gB, and gH/gL for efficient cell fusion, epithelial cells require only gB, and gH/gL and when a mutant form of gB is used, only gB is required for efficient cell fusion indicating that gB may be the major fusion protein for epithelial cells and that a specific epithelial receptor for gB may exist. This proposal will analyze: 1 - The role of gB in EBV entry of epithelial and B cells by the identification of important gB functional domains by site-specific and random mutation. 2 - The role of the gB cytoplasmic tail in regulating fusion and mediating virion morphogenesis as well as the function of several cellular proteins that bind the gB tail will be determined. 3 - The existence of a novel gB receptor will be investigated. Clarifying the interactions between EBV and target cells is essential for understanding the tropism of EBV infections in the human host. Knowledge of the mechanism and viral and cellular factors required for EBV entry and replication in epithelial and B cells will provide insight into host susceptibility and will allow for the development of therapeutics for the treatment or eradication of EBV-associated diseases.