New tools for acute spatiotemporal control of GPCR signalling in vivo

G蛋白偶联受体家族由大约800个成员组成。它们是存在于细胞表面的蛋白质，它们在人体的几乎每一个过程中都扮演着重要的角色。这些蛋白质也是临床上使用的大约三分之一药物的靶标。不幸的是，即使这些受体已被证明是很好的药物靶点，GPCR药物发现仍然与高失败率有关，主要是因为许多已开发的药物没有表现出足够的治疗效果和/或引起不想要的副作用。这种损耗在很大程度上是由于我们对这个受体家族的个体成员如何在体内控制过程的不完全了解。这变得更加复杂，因为许多这些受体在不同组织的不同细胞类型中表达。这意味着，一种药物作用于身体某一部位的受体以产生治疗效果，也可能作用于身体另一部位的同一受体以产生不良反应。为了开发更好的药物，我们需要了解不同组织中的GPCRs如何控制体内的不同过程。到目前为止，这方面的进展有限，因为我们没有工具来有选择地以细胞特有的方式审问这些过程。我们的目标是开发两种协同方法，使我们能够做到这一点。第一种方法是开发一种策略，通过将药物与特定细胞类型的外部捆绑来限制药物对该特定细胞类型的作用。第二种方法将允许我们以特定于细胞类型的方式关闭由GPCR启动的细胞内的进程。我们将使用这些方法来了解药物在GPCR中是如何作用的，这是所有阿片类止痛药的靶点，Mu阿片受体。阿片类药物和吗啡一样，是治疗严重疼痛的最有效药物。不幸的是，阿片类药物会导致不良反应，如上瘾、便秘和呼吸抑制(过量服药导致死亡的原因)。Mu阿片受体是GPCR家族的成员之一，控制着阿片类止痛药的疗效和副作用。据认为，阿片受体激活神经细胞中两种不同类型的蛋白质，一种(G蛋白)介导疼痛缓解，另一种(Arrestin)介导不良反应。然而，最近的研究对这一发现提出了异议。这突出了了解阿片受体如何激活神经元中控制止痛或不良副作用的过程的重要性。我们建议开发新的工具，使我们能够在大脑中的准确时间和位置阻止u阿片受体的激活和细胞内的信号传递。我们将使用这种方法来了解导致阿片类药物对呼吸频率影响的细胞种群和细胞信号传递过程。这些方法将被广泛应用，并将使我们能够理解当药物以前所未有的细胞特异性方式以时间精确度作用于其靶点GPCR时的生理效应。通过了解特定细胞信号在确定药物的治疗和副作用中的作用，我们可以利用这些信息来促进新的更安全药物的发现和开发。

The G protein coupled receptor (GPCR) family consists of approximately 800 members. They are proteins found on the surface of cells and they play important roles in virtually every process in the body. These proteins are also the target of approximately one third of all medicines used in the clinic. Unfortunately, even though these receptors have proved to be good drug targets, GPCR drug discovery is still associated with a high rate of failure, predominantly because many developed drugs do not display a sufficient therapeutic effect and/or cause unwanted side effects. This attrition is due, to a large part, to our incomplete understanding of how individual members of this receptor family control processes in the body. This is made even more complicated as many of these receptors are expressed in different cell types in different tissues. This means that a drug that acts at one of these receptors in one part of the body to have a therapeutic effect, might act at the same receptors in another part of the body to cause an adverse effect. In order to develop better medicines, we need to understand how GPCRs in different tissues control the different processes in the body. Up until now, progress in this regard has been limited because we did not have the tools with which to selectively interrogate these processes in a cell specific manner. We aim to develop two synergistic approaches that will enable us to do this. The first approach will be to develop a strategy to restrict the action of a drug to a specific cell type by tethering it to the outside of that specific cell. The second method will allow us to switch off processes inside the cell that are initiated by GPCRs in a cell type-specific manner. We will use these methods to understand how drugs act at a GPCR that is the target of all opioid pain killers, the mu opioid receptor.Opioids, like morphine, are the most effective drugs to treat severe pain. Unfortunately, opioids cause adverse effects such as addiction, constipation and suppression of breathing (the cause of fatality from overdose). The mu opioid receptor, a member of the GPCR family, controls both the therapeutic effects and the adverse side effects of opioid pain killers. It has been suggested opioid receptors activate two different types of proteins in nerve cells, one (G protein) that mediates pain relief, while another (arrestin) mediates adverse effects. However, recent research disputes this finding. This highlights the importance of understanding how opioid receptors activate processes in neurons that control pain relief or unwanted side effects. We propose to generate new tools that will allow us to block mu opioid receptor activation and signalling within the cell at a precise time and location in the brain. We will use this approach to understand the cell populations and cellular signalling processes that are responsible for causing the effect of opioids on breathing rate. These approaches will be widely applicable and will allow us to understand the physiological effects of a medicine when it acts at its target GPCR in an unprecedented cell specific manner with temporal precision. By understanding the role of specific cell signals in determining the therapeutic and side effects of medicines we can use this information to facilitate the discovery and development of newer safer medicines.