Building mechanistic insight into evolvability of viral cell-entry functions

建立对病毒细胞进入功能进化的机制洞察

基本信息

批准号：
9350838
负责人：
Tijana Ivanovic
金额：
$ 243.75万
依托单位：
BRANDEIS UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2017
资助国家：
美国
起止时间：
2017-09-30 至 2022-08-31
项目状态：
已结题

项目摘要

PROJECT SUMMARY/ABSTRACT: Influenza, ebola, dengue and zika are only a few of the viruses which caused past or ongoing pandemics and threaten recurrence. All of these viruses package their infectious genomes in a cell-derived membrane envelope decorated with viral proteins that mediate infectious cell entry. Due to pressures for mechanistic economy imposed by their small size, viruses often combine in a single protein different interdependent functions. Yet they retain extreme adaptability – they evolve rapidly under changing conditions. Viral cell-entry proteins combine distinct protein domains with membrane fusion and target cell attachment functions. Membrane fusion delivers viral genomes to the cell interior by merging the viral envelope with a cell membrane. The attachment domains bring viruses to the fusion target. They also serve to stabilize fusion domains in the extracellular environment, which retards fusion within endosomes (sites of fusion inside cells) – they act as fusion repressors. Thus productive cell entry requires a delicate balance of protein's stability and functional plasticity. One source of changing external pressures on cell entry are neutralizing antibodies produced by the immune system. Another source are mechanistic pressures of zoonotic adaptations, when entry proteins adjust preference from animal to human receptors, and alter fusion protein stability as required for human-to-human transmission. How is the extreme adaptability achieved by a system that is constrained both by the changing environment and mechanistic economy? In my past work, I achieved unprecedented, molecular-level resolution of influenza membrane fusion by combining 1) single-virion real-time imaging of membrane fusion of authentic virions with planar membrane bilayers, 2) computational and theoretical modeling of time-delay distributions to various fusion intermediates, and 3) structure-based mutagenesis. This work offered the first glimpse into how adaptability of membrane fusion might be achieved through combined action among multiple fusion proteins on a virus. Hundreds of fusion proteins on a single influenza virus particle contact the target membrane, but only several neighboring ones mediate fusion. I have identified independent avenues available to influenza to fine-tune fusion, two of which affect either the available pool of active fusion proteins on the virion surface or the required number of fusion-protein neighbors. In this proposal, I seek to 1) determine the molecular mechanisms allowing adaptation of the interdependent cell-entry functions of influenza, and 2) define the constraints limiting evolvability of the influenza virus cell-entry functions. I will build upon my combined approaches to enable a holistic molecular picture of membrane fusion and membrane attachment/fusion-repression functions of intact HAs on authentic virions and in near native conditions of purified endosomes. By defining evolutionary rules, entry-protein functional changes, and their co-dependence, we might improve our predictive ability for viral strains with high pandemic potential. Fundamental principles deduced for influenza are likely to extend to other viral cell-entry systems.

项目摘要/摘要：流感，埃博拉，登革热和寨卡是引起过去或正在进行的大流行的少数病毒威胁复发。所有这些病毒在细胞衍生的膜上包装其感染基因组媒体感染性细胞进入的病毒蛋白装饰的信封。由于机械的压力经济体积小，病毒经常结合在单一蛋白质中不同的相互依存功能。然而，它们保留了极端的适应性 - 它们在不断变化的条件下迅速发展。病毒细胞进入蛋白质将不同的蛋白质结构与膜融合和靶细胞附着功能相结合。膜融合通过将病毒包膜与细胞合并为细胞内部传递病毒基因组膜。附件域将病毒带到融合靶标。他们还可以稳定融合细胞外环境中的结构域，它阻碍了内体内的融合（细胞内融合的位点） - 它们充当融合反射器。该产品细胞的进入需要蛋白质稳定性的微妙平衡和功能可塑性。细胞进入的外部压力变化的一种来源是中和抗体由免疫系统产生。另一个来源是人畜共患的机械压力，当进入蛋白调整从动物而不是人体受体的偏好，并根据需要改变融合蛋白稳定性用于人类到人类的传播。如何通过受约束的系统实现极端适应性无论是通过不断变化的环境和机械经济吗？在过去的工作中，我实现了前所未有的通过组合有影响力膜融合的分子水平分辨率1）正宗病毒粒子与平面膜双层的膜融合，2）计算和理论时间延迟分布对各种融合中间体的建模，以及3）基于结构的诱变。这作品首先瞥见了如何通过合并来实现膜融合的适应性多种融合蛋白在病毒上的作用。单个影响病毒的数百种融合蛋白粒子接触目标膜，但只有几个相邻的媒体融合。我已经确定了可用于影响到微调融合的独立途径，其中两个影响了可用的池病毒体表面上的活性融合蛋白或所需数量的融合蛋白邻居。在此提案中，我寻求1）确定允许适应相互依赖细胞输入函数的分子机制造成影响力和2）定义了限制了限制流感病毒细胞进入功能的限制。我会建立在我的结合方法上，以使膜融合和膜的整体分子图片的整体图片完整的依恋/融合抑制功能对正宗病毒体具有纯化的内体。通过定义进化规则，进入 - 蛋白质功能变化及其共同依赖性，我们可能会提高我们对大流行潜力的病毒菌株的预测能力。基本原则推导为影响力的人可能会扩展到其他病毒细胞进入系统。