Retrovirus Entry and Virus Evolution

逆转录病毒是人类和动物的重要病原体， 作为良性基因传递载体的工具，并具有作为基因治疗的治疗载体的潜力。是否致病 或治疗，病毒的初始感染和随后的传播取决于逆转录病毒的有效进入 进入宿主细胞虽然对病毒进入的机制的详细理解还没有被明确定义， 在逆转录病毒中，所有逆转录病毒都具有共同的进入细胞的总体策略。逆转录病毒进入的第一步， 病毒表面糖蛋白（SU）和细胞受体之间的相互作用是复杂的，涉及多个， 两种蛋白质中的非连续决定簇指定受体选择、结合亲和力和触发 病毒糖蛋白的构象变化。尽管这种相互作用很复杂，但逆转录病毒具有 能够进化其包膜糖蛋白的结构，以使用不同的细胞蛋白作为受体，通常是 与原始受体没有明显同源性，并保留有效进入功能的蛋白质。逆转录病毒如何 怎么办？了解这种能力将为抗病毒干预和靶向基因治疗提供有价值的信息 交付. 我们假设：（1）包膜糖蛋白被组织成允许改变的功能域， 通过突变和/或重组在受体选择中发生，同时维持受体结合和受体结合的临界水平。 亲和力和触发糖蛋白构象变化以启动融合过程的能力;（2）多个， 位于SU高变区的非连续受体相互作用决定簇是结合所必需的 （3）SU高变结构域以外的区域将发挥作用， 连接受体结合以触发糖蛋白锁定机制，并将随着病毒的变化而保守 受体利用逆转录病毒的同源组，亚组A至E（A-E）禽白血病病毒（ALV）， 提供一个强大的模型系统，通过提供高度相关的病毒来测试这些假设，这些病毒是从 共同祖先利用不同受体。具体而言，我们的目标是： 1.从遗传学上确定了对ALV基因表达起重要作用的A-E亚群包膜糖蛋白的功能区/残基 受体结合亲和力2. A-E亚群ALV糖蛋白的遗传定义功能区域/残基 对受体使用的特异性很重要。3.鉴定和表征ALV糖蛋白中的区域/残基 对于连接受体结合以触发引发融合过程的构象变化是重要的。4. 从基因上定义ALV受体的功能区域/残基，这些区域/残基是结合亲和力和触发免疫反应所必需的 ALV糖蛋白的构象变化。5.测试ALV糖蛋白的可溶形式的能力， 产生适合结构研究的晶体。

Retroviruses, which include many important pathogens of humans and animals, have become important research tools as benign gene delivery vectors, and have potential as therapeutic vectors for gene therapy. Whether pathogenic or therapeutic, the initial infection and subsequent dissemination of the virus depends on efficient entry of the retrovirus into host cells. While a detailed understanding of the mechanisms of viral entry has not been clearly defined for any retrovirus, all retroviruses share a common overall strategy for entry into cells. The initial step of retrovirus entry, the interaction between the viral surface glycoprotein (SU) and a cellular receptor, is complex, involving multiple, noncontiguous determinants in both proteins that specify receptor choice, binding affinity and the ability to trigger conformational changes in the viral glycoproteins. Despite the complexity of this interaction, retroviruses have the ability to evolve the structure of their envelope glycoproteins to use a different cellular protein as a receptor, often a protein that has no obvious homology to the original receptor, and retain efficient entry functions. How do retroviruses do this? Understanding this ability will provide valuable information for antiviral intervention and targeting gene delivery. We hypothesize that: (1) the envelope glycoproteins are organized into functional domains that allow changes to occur in receptor choice by mutation and/or recombination while maintaining a critical level of both receptor binding affinity and the ability to trigger glycoprotein conformational changes to initiate the fusion process; (2) multiple, noncontiguous receptor interaction determinants located in the SU hypervariable domains are required for binding affinity and to restrict or broaden receptor usage; (3) regions outside of the SU hypervariable domains will function to connect receptor binding to triggering the glycoprotein lock mechanism and will be conserved as the virus changes receptor usage. The homologous group of retroviruses, the subgroups A through E (A-E) avian leukosis viruses (ALV), provide a powerful model system to test these hypotheses by supplying highly related viruses that have evolved from a common ancestor to utilize different receptors. Specifically, we aim to: 1. Genetically define functional regions/residues of the subgroup A-E ALV envelope glycoproteins important for receptor binding affinity. 2. Genetically define functional regions/residues of the subgroup A-E ALV glycoproteins important for the specificity of receptor usage. 3. Identify and characterize regions/residues in the ALV glycoproteins important for connecting receptor binding to triggering the conformational changes that initiate the fusion process. 4. Genetically define functional regions/residues of the ALV receptors necessary for binding affinity and triggering a conformational change in the ALV glycoproteins. 5. Test soluble forms of the ALV glycoproteins for the ability to produce crystals suitable for structural studies.