Virus Wars: Are E3-Targeted Therapies A New Hope?

病毒感染在世界各地造成了大量无法量化的疾病、死亡和社会经济负担。有些病毒似乎难以躲避，无法接种疫苗，而抗病毒药物最终会失败，因为它们会在目标病毒中引起耐药性。迫切需要新型抗病毒药物。我的研究计划的主要目标是加快“宿主导向疗法”的发展，这是一种有希望替代靶向病毒蛋白的抗病毒药物的疗法。要做到这一点，我首先要了解宿主细胞对病毒感染的反应有哪些相关参与者。一个常见的假设是，细胞仅仅通过改变酶的相对丰度来调节它们的酶。我们了解到（并且普遍同意）翻译后控制很重要，但测量这一点比评估基因表达或蛋白质丰度要棘手得多，随着时间的推移，基因表达或蛋白质丰度已成为“活性”的替代品。英国邓迪大学（University of Dundee）的一个实验室设计了一种巧妙的方法，专门测量一种特殊酶的活性（而不是丰度），这种酶在细胞生物学的各个方面都具有深远的重要性——“E3泛素连接酶”（E3）。E3s就像“贴纸枪”一样，用一种叫做泛素的小蛋白质修饰来标记其他蛋白质。泛素标记的蛋白质通常被送到细胞的分子废物处理系统进行回收。已知一些e3有助于病毒感染的进展（前病毒），而另一些则阻碍感染的进展（抗病毒）。操纵这些活动可能会导致新的创新疗法来控制病毒感染。这项技术被称为“基于活性的探针”（ABP），其工作原理是模仿E2在生命中的主要伙伴，E2泛素结合酶（E2）。E2s与细胞中的活性E3s短暂结合；以e2为基础的ABP不可逆地与e3结合，将其捕获并泄露其先前的激活状态。因此，使用ABP可以让我从“糠秕中挑选小麦”，并发现当我们谈论“宿主导向治疗”时，我们应该关注哪些e3。人类免疫缺陷病毒（HIV）和甲型流感病毒（IAV）是几乎没有减弱迹象的三种特别有害的感染。艾滋病毒是一种大流行病；禽流感具有大流行的潜力。利用这两种病毒感染模型，我将在宿主的E3活动反应中寻找共同的和不同的“分子特征”，这可能为新疗法指明道路。我将用病毒感染细胞，然后将ABP侦察兵送入被感染的细胞内，在那里他们会揭示感染过程中E3活动变化的全景。识别我们细胞中的趋同分子特征甚至可能为广谱宿主定向治疗指明道路。

Viral infections are responsible for an unquantifiable amount of disease, death and socioeconomic burden around the world. Some viruses seem too evasive to vaccinate against and antiviral drugs ultimately fail because they cause resistance in their viral targets. There is an urgent need for new classes of antiviral medicines.The main objective of my research proposal is to fast-track the development of 'host-directed therapies', a promising alternative to antiviral drugs that target viral proteins.To do this, I first want to understand which are the relevant participants of a host cell's response to viral infection. A frequently held assumption is that cells regulate their enzymes simply by changing their relative abundance. We learn (and generally agree) that post-translational control is important, but measuring this has been much trickier than assessing gene expression or protein abundance, which have over time become a surrogate for 'activity'. A lab at the University of Dundee have designed an ingenious way to specifically measure the activity (rather than the abundance) of a particular class of enzyme that has profound importance in all aspects of cell biology - the 'E3 ubiquitin ligase' (E3).E3s act like 'sticker-guns', labelling other proteins with a small protein modification called ubiquitin. Ubiquitin-labelled proteins are most commonly sent to the cell's molecular waste disposal system for recycling. Some E3s are known to help viral infections progress (pro-viral) while others hinder the progression of infection (antiviral). Manipulating these activities could lead to new innovative therapies to control viral infections.The technology - called an 'Activity-based probe' (ABP) - works by mimicking the E3s main partner in life, the E2 ubiquitin conjugating (E2) enzyme. E2s bind transiently to active E3s in cells; an E2-based ABP binds irreversibly to E3s, trapping it and divulging its prior state of activation. So, using the ABP allows me to sort the 'wheat from the chaff' and discover which E3s we should be focusing on when we talk about 'host-directed therapy'.Three particularly pernicious infections which show few signs of abating are human immunodeficiency virus (HIV) and influenza A virus (IAV). HIV is a pandemic infection; IAV has the potential for pandemics. Using these two virus infections models, I will look for common and divergent 'molecular signatures' in the host's E3 activity response that might signpost the way to novel therapies. I will infect cells with a virus, and then send the ABP scouts inside the infected cell, where they reveal a panorama of E3 activity change during the course of infection. Identifying convergent molecular signatures in our cells might even signpost the way to broad-spectrum host-directed therapies.