EBV gB Function in Viral Fusion, Entry, and Egress

描述（由申请方提供）：了解EB病毒（EBV）进入靶细胞和病毒粒子在感染细胞中运输的分子基础是Longnecker实验室的长期目标。我们预期，与感染细胞中EBV进入和病毒体形态发生相关的发现对于开发治疗人类宿主中EBV相关癌症的疗法将是重要的。我们的总体假设，驱动我们的研究重点是，EBV gB与特定的细胞表面受体，促进病毒融合和进入EBV靶细胞相互作用。此外，EBV gB的胞质尾区与宿主和病毒蛋白相互作用，并且这种相互作用对于调节融合是重要的，但也是EBV衣壳从感染的细胞中适当流出所需的。EBV在体内的组织嗜性主要限于上皮或淋巴起源的细胞。EBV进入靶B细胞所需的细胞和病毒因子已经有相当好的描述。主要病毒包膜糖蛋白350/220（gp 350/220）结合在B细胞上大量表达的CR 2/CD 21。随后，gp 42与HLA II类结合，触发由gB和gH/gL介导的融合。关于EBV诱导的膜融合和病毒进入上皮细胞的机制，知之甚少。显然，其他受体在上皮细胞中起作用，因为CD 21和HLA II类通常不在上皮细胞上表达。Lindsey Hutt-Fletcher提供了令人信服的证据表明，与B细胞相比，EBV进入上皮细胞的机制是不同的。在我们的初步研究中，我们已经表明，与需要gp 42、gB和gH/gL进行有效细胞融合的B细胞相反，上皮细胞仅需要gB和gH/gL，并且当使用gB的突变形式时，仅需要gB进行有效细胞融合，这表明gB可能是上皮细胞的主要融合蛋白，并且可能存在gB的特异性上皮受体。该提案将分析：1 -gB在EBV进入上皮细胞和B细胞中的作用，通过位点特异性和随机突变鉴定重要的gB功能结构域。2 -将确定gB胞质尾在调节融合和介导病毒体形态发生中的作用以及结合gB尾的几种细胞蛋白的功能。3 -将研究新的gB受体的存在。阐明EBV和靶细胞之间的相互作用对于理解EBV感染在人类宿主中的向性至关重要。对EBV进入上皮细胞和B细胞并在其中复制所需的机制和病毒及细胞因子的了解将提供对宿主易感性的深入了解，并将允许开发用于治疗或根除EBV相关疾病的治疗剂。

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.