Retrovirus Entry and Virus Evolution

描述（由申请人提供）：逆转录病毒是人类和动物的许多重要病原体，作为良性基因传递载体已成为重要的研究工具，并有潜力作为基因治疗的治疗载体。无论是致病性的还是治疗性的，病毒的初始感染和随后的传播取决于逆转录病毒有效地进入宿主细胞。虽然对任何逆转录病毒的病毒进入机制的详细了解还没有明确定义，但所有逆转录病毒都有一个共同的进入细胞的总体策略。逆转录病毒进入的第一步，即病毒表面糖蛋白（SU）与细胞受体之间的相互作用，是复杂的，涉及两种蛋白质中多个不连续的决定因素，这些决定因素指定受体选择、结合亲和力和触发病毒糖蛋白构象变化的能力。尽管这种相互作用很复杂，但逆转录病毒有能力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，通常是一种与原始受体没有明显同源性的蛋白质，并保留有效的进入功能。逆转录病毒是如何做到的呢？了解这种能力将为抗病毒干预和靶向基因传递提供有价值的信息。

DESCRIPTION (provided by applicant): 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.