Activation of the A2A adenosine G-protein-coupled receptor by conformational selection
Activation of the A2A adenosine G-protein-coupled receptor by conformational selection
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DOI：
10.1038/nature17668
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发表时间：
2016-05-12
期刊：
影响因子：
64.8
通讯作者：
Prosser, R. Scott
中科院分区：
文献类型：
--
作者：
Ye, Libin;Van Eps, Ned;Prosser, R. Scott
构象选择和诱导拟合是解释基于配体的受体激活的分子基础的两种主要机制(1,2)。 G蛋白偶联受体是最大一类细胞表面受体，也是重要的药物靶点。从分子角度理解其激活机制对于药物发现和设计至关重要。然而，关于激动剂结合如何导致活性受体状态形成的直接证据却很少(3)。在这里，我们使用 F-19 核磁共振来量化腺苷 A(2A) 受体 (A(2A)R)（一种典型的 A 类 G 蛋白偶联受体）所占据的构象景观。我们发现了四个处于平衡状态的集合：（1）毫秒交换的两个非活性状态，与跨膜螺旋 3 和 6 之间形成的（状态 S-1）和断裂的（状态 S-2）盐桥（称为“离子锁”）一致； (2) 两种活性状态，S-3 和 S-3'，通过 G 蛋白衍生肽的结合来鉴定。与最近对 β(2)-肾上腺素能受体 (4) 的研究相反，本方法可以识别 A(2A)R 的第二种活性状态。添加反向激动剂（ZM241385）会增加非活性状态的数量，而完全激动剂（UK432097或NECA）以与构象选择一致的方式稳定活性状态S-3'。相比之下，部分激动剂 (LUF5834) 和变构调节剂 (HMA) 专门增加 S-3 状态的数量。因此，部分激动是通过对不同活性状态的构象选择来实现的，我们预测该活性状态将损害与 G 蛋白的偶联。直接观察配体依赖性G蛋白偶联受体的构象平衡并推论受体激活的潜在机制将对我们理解G蛋白偶联受体在健康和疾病中的功能产生广泛的影响。
Conformational selection and induced fit are two prevailing mechanisms(1,2) to explain the molecular basis for ligand-based activation of receptors. G-protein-coupled receptors are the largest class of cell surface receptors and are important drug targets. A molecular understanding of their activation mechanism is critical for drug discovery and design. However, direct evidence that addresses how agonist binding leads to the formation of an active receptor state is scarce(3). Here we use F-19 nuclear magnetic resonance to quantify the conformational landscape occupied by the adenosine A(2A) receptor (A(2A)R), a prototypical class A G-protein-coupled receptor. We find an ensemble of four states in equilibrium: (1) two inactive states in millisecond exchange, consistent with a formed (state S-1) and a broken (state S-2) salt bridge (known as 'ionic lock') between transmembrane helices 3 and 6; and (2) two active states, S-3 and S-3', as identified by binding of a G-protein-derived peptide. In contrast to a recent study of the beta(2)-adrenergic receptor(4), the present approach allowed identification of a second active state for A(2A)R. Addition of inverse agonist (ZM241385) increases the population of the inactive states, while full agonists (UK432097 or NECA) stabilize the active state, S-3', in a manner consistent with conformational selection. In contrast, partial agonist (LUF5834) and an allosteric modulator (HMA) exclusively increase the population of the S-3 state. Thus, partial agonism is achieved here by conformational selection of a distinct active state which we predict will have compromised coupling to the G protein. Direct observation of the conformational equilibria of ligand-dependent G-protein-coupled receptor and deduction of the underlying mechanisms of receptor activation will have wide-reaching implications for our understanding of the function of G-protein-coupled receptor in health and disease.