Molecular Switches as Sensors for Kinase Activity

这项研究的目标是开发一种新的分子，可以报告重要的生物过程，作为科学家设计新药的工具。生物学使用各种类型的蛋白质在细胞中传递信号，使细胞能够对环境做出反应。一种这样的信号机制是在蛋白质中添加一个磷酸基团，这一过程是由一类被称为“激酶”的蛋白质执行的。一些疾病，包括癌症，可能部分是因为细胞中的信号机制变得有问题，例如，告诉细胞在不应该生长的时候生长。正因为如此，激酶酶是新药的一个有吸引力的靶点。药物化学家正在设计能够关闭特定的激酶的小分子，从而阻止它们的信号传递。这有可能关闭患病细胞中破碎的信号机制。不幸的是，测量一种酶的活性并不简单，所以要知道一种新药是否能有效地抑制一种特定的酶是一个困难和耗时的过程。我们将通过开发一种分子来帮助解决这个问题，这种分子可以报告给定的激酶的活性有多高，从而加快寻找激酶抑制剂的过程。这种报告分子将以一种独特的方式工作：当激酶在其上添加一个磷酸基团时，它会改变形状，而形状的变化将产生标准实验室仪器可以检测到的荧光信号。这是可能的，因为报告分子是一种“肽”，由与蛋白相同的构建块组成，通常情况下，该蛋白会添加一个磷酸基团。传感器之所以能发挥作用，是因为它有一个中心核心，它可以以两种不同的形状存在：一种是拉伸的，另一种是分子折叠回来的。当它没有磷酸基团时，传感器将主要以伸展状态存在。然而，当该酶添加了一个磷酸基团时，传感器会自行折叠起来，这样它就可以包裹在磷酸基团周围。这种折叠的形式将使两个特殊的荧光基团在太空中靠近，使它们能够产生标准实验室仪器可以很容易检测到的信号。这样做的结果是，传感器产生的信号量将取决于激酶向其添加磷酸基团的能力。这意味着科学家将能够进行一次筛选，他们只需寻找阻止激酶将传感器切换到打开状态的条件，就可以寻找抑制激酶的小分子。这种快速筛选在寻找新药方面至关重要，因为潜在药物分子的数量是巨大的。在用于治疗癌症的激酶抑制剂的情况下，也有必要考虑到激酶本身可能发生突变，导致癌症对药物产生抗药性。通过加快筛选过程，将有可能更快地搜索新药，并更好地了解个体激酶的变化如何影响他们对现有药物的反应。这将帮助临床医生针对患者的特定疾病量身定做他们的治疗方案--所谓的“个性化医疗保健”。在癌症方面，这将帮助医生领先于可能导致肿瘤产生抗药性的突变一步，使他们能够在知情的情况下更好地选择使用哪些药物，从而产生更有效的治疗方法。

The goal of this study is to develop a new class of molecule that can report back on important biological processes as a tool for scientists designing new drugs. Biology uses various types of protein to pass signals around a cell, allowing the cell to respond to its environment. One such signalling mechanism is the addition of a phosphate group to a protein, and this process is carried out by a class of proteins called 'kinases'. Some diseases, including cancer, can come about in part because the signalling mechanism in a cell has become faulty, for example telling it to grow when it should not. Because of this, kinase enzymes are an attractive target for new drugs. Medicinal chemists are designing small molecules that can shut down specific kinases, and therefore prevent their signal from being passed on. This has the potential to switch off the broken signalling mechanisms in a diseased cell. Unfortunately, measuring the activity of a kinase is not straightforward, so it is a difficult and time-consuming process to know whether or not a new drug will be effective at inhibiting a specific kinase. We will help to solve this problem by developing a molecule that will act as a reporter of how active a given kinase is, therefore speeding up the process of searching for kinase inhibitors. This reporter molecule will work in a unique way: it will change shape when a kinase adds a phosphate group to it, and the change in shape will bring about a fluorescent signal that can be detected with standard laboratory instruments. This is possible because the reporter molecule is a 'peptide', built from the same building blocks as the proteins that the kinase would normally add a phosphate group to. The sensor will work because it has a central core that can exist in two distinct shapes: one stretched out, and one in which the molecule is folded back on itself. When it doesn't have a phosphate group, the sensor will exist predominantly in the stretched out state. When the kinase adds a phosphate group to it, however, the sensor will fold back on itself so that it can wrap around the phosphate group. This folded form will bring two special fluorescent groups close together in space, allowing them to produce a signal that can be easily detected with standard lab instruments. The result of this is that the amount of signal produced by the sensor will depend on the ability of the kinase to add a phosphate group to it. This means that a scientist will be able to conduct a screen where they look for small molecules that inhibit a kinase simply by looking for conditions in which the kinase is prevented from switching the sensor to the 'on' state. Rapid screens of this sort are vitally important in the search for new drugs because the number of potential drug molecules is huge. In the case of kinase inhibitors for the treatment of cancer it is also necessary to consider that the kinases themselves can mutate, causing a cancer to become resistant to a drug. By speeding up the screening process it will become possible to search for new drugs more quickly, and to better understand how changes to individual kinases can affect their response to existing drugs. This will help clinicians to tailor their treatments to a patient's specific illness- so called 'personalised healthcare'. In the case of cancer this will help doctors to be one step ahead of the mutations that can cause a tumour to become drug resistant, allowing them to make better informed choices of which drugs to use, resulting in more-effective treatments.