CryoEM structure of cannabinoid receptor CB2 with a biased ligands

G蛋白偶联受体(GPCRs)是细胞环境和细胞内部之间传递信号的受体。由于它们在细胞信号中的关键作用，它们是三分之一上市药物的靶标。配体与激动剂活性的结合稳定了gpr的特定构象，从而导致G蛋白和arrestin介导的信号通路的激活。现在人们普遍认识到，由于作用的特异性更高，副作用更小，所以只激活特定信号通路的子集的偏向疗法，比现有的具有全部激动剂或拮抗剂活性的药物具有显著的进步。目前正在作出重大努力来开发这种药物。然而，由于GPCRs的混杂和信号通路的复杂性，通常很难将观察到的候选偏向配体的影响归因于一种特定的信号模式。大麻素受体CB2是治疗炎症性疾病、疼痛、骨质疏松、动脉粥样硬化和脑肿瘤的有价值的药物靶点。我们最近发现了几个CB2配体，它们显示出强烈的信号偏向。互补诱变结果表明，配体结合部位含有介导配体结合诱导的信号传导的“热点”，并可能影响偏向信号传导。我们的主要假设是，CB2配体通过配体结合口袋中的特定相互作用发挥其作用和信号偏向。为了验证这一假设，我们需要有偏见的配体如何与受体结合的结构信息。该项目将专注于利用低温电子显微镜获得CB2受体与几个偏置配体的复合体的低温电子显微镜结构。学生将学习哺乳动物细胞培养、膜蛋白生物化学和单颗粒低温电子显微镜技术。这些技能将与培训药理分析相补充，以表征受结构数据启发的新配体的药理学。该项目的结果将在受体诱导的结构变化与其信号特性之间建立联系，并将促进下一代“偏向”疗法的发展。该学生将被嵌入膜蛋白和受体中心(COMPARE)，这是伯明翰大学和诺丁汉大学之间的独特合作，是欧洲和世界范围内GPCR卓越的中心。它提供了一个由40多名博士生和博士后组成的充满活力的社区，以发展研究和演讲技能，以及一个学术网络。此外，他们将在RCH从事低温EM结构测定工作，并进一步扩大他们的学术网络。

G protein-coupled receptors (GPCRs) are transmit signals between the cellular environment and its interior. Due to their key role in cellular signalling, they are the target of a third of marketed drugs. Binding of ligands with agonist activity stabilises particular conformations of a GPCR, which result in the activation of G proteins and arrestin-mediated signalling pathways. It is now widely recognized that "biased" therapeutics, which activate only a subset of specific signalling pathways, offer significant advancement over existing drugs with full agonist or antagonist activity due to higher specificity of action and lower side effects. Significant efforts are now being directed to develop such drugs. However, due to the promiscuity of the GPCRs and complexity of the signalling pathways, it is often difficult to attribute the observed effects of candidate biased ligands to one particular mode of signalling. Cannabinoid receptor CB2 is a valuable drug target for treating inflammatory diseases, pain, osteoporosis, atherosclerosis and brain tumours. We recently identified several CB2 ligands that show strong biased signalling profile. Complementary mutagenesis results suggested that the ligand binding site contains "hot-spots" that mediate signalling induced by the ligand binding, and are likely to affect biased signalling. Our main hypothesise is that CB2 ligands exert their action and signalling bias via specific interactions in the ligand binding pocket. To test this hypothesis, we need structural information of how biased ligands bind the receptor. The project will focus on obtaining a CryoEM structure of CB2 receptor in complex with several biased ligands using CryoEM. The student will learn mammalian cell culture, membrane protein biochemistry and single-particle CryoEM techniques. These skills will be complemented with training pharmacological assays to characterise pharmacology of novel ligands inspired by the structural data. The results of the project will establish a link between the structural changes induced in receptors to their signalling properties and would promote the development of the next generation of "biased" therapeutics.The student will be embedded in the Centre of Membrane Proteins and Receptors (COMPARE), a unique collaboration between the Universities of Birmingham and Nottingham, a centre of GPCR excellence in Europe and worldwide. It offers a vibrant community of over 40 PhD students and post-docs to develop research and presentation skills and an academic network. Additionally, they will work at RCH on CryoEM structure determination and further expanding their academic network.