Crystal structure of a constitutive active mutant of adenosine A(2A) receptor.
Crystal structure of a constitutive active mutant of adenosine A(2A) receptor.
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组成型活性突变体I92 N的结构揭示了腺苷A2 A受体（A2 AAR）的传输开关区域中的亲水网络。结合分子动力学模拟的结构表明，突变体I92 N在激动剂的存在或去除下保持中间状态，因此这揭示了其更高的基础活性。腺苷A2 A受体（adenosine A2 A receptor，A2 AAR）是G蛋白偶联受体（GPCRs）A类亚家族的典型成员，广泛分布于人体的各种组织和器官中，参与许多重要的信号调节过程。我们以前总结了一个共同的激活途径，A类GPCR中的一系列保守残基/基序进行构象变化，在细胞外激动剂结合，并最终诱导细胞内G蛋白的偶联。通过这一机制，我们已经成功地预测了几个新的组成型活性或非活性突变A2 AAR。为了揭示突变诱导的组成型活性的分子机制，我们确定了与激动剂UK-432097复合的典型突变体I92 N的结构。突变的I92 N与附近的残基形成亲水相互作用网络，包括CWxP基序的Trp6.48，其在野生型A2 AAR中不存在。尽管突变体结构总体上类似于先前确定的中间态A2 AAR结构（PDB ID 3qak）[Xu，Wu，Katritch，Han，Jacobson，Gao，Cherezov & Stevens（2011）. Science，332，322-327]，分子动力学模拟表明，I92 N突变体通过亲水相互作用网络稳定亚稳态中间状态，并有利于受体向活性状态的构象转变。该研究为构象突变引发的特殊药理学结果提供了结构模板，并为A类GPCR的未来结构或药理学研究提供了参考。
The structure of constitutive active mutant I92N reveals a hydrophilic network in the transmission-switch region of the adenosine A2A receptor (A2AAR). The structure combined with molecular dynamics simulations suggests that the mutant I92N preserves the intermediate state in the presence or removal of an agonist, thus this sheds light on its higher basal activity. The adenosine A2A receptor (A2AAR) is a prototypical member of the class A subfamily of G-protein-coupled receptors (GPCRs) that is widely distributed in various tissues and organs of the human body, and participates in many important signal-regulation processes. We have previously summarized a common activation pathway of class A GPCRs in which a series of conserved residues/motifs undergo conformational change during extracellular agonist binding and finally induce the coupling of intracellular G protein. Through this mechanism we have successfully predicted several novel constitutive active or inactive mutations for A2AAR. To reveal the molecular mechanism of mutation-induced constitutive activity, we determined the structure of a typical mutant I92N complexed with the agonist UK-432097. The mutated I92N forms a hydrophilic interaction network with nearby residues including Trp6.48 of the CWxP motif, which is absent in wild-type A2AAR. Although the mutant structure is similar overall to the previously determined intermediate-state A2AAR structure (PDB ID 3qak) [Xu, Wu, Katritch, Han, Jacobson, Gao, Cherezov & Stevens (2011). Science, 332, 322–327], molecular dynamics simulations suggest that the I92N mutant stabilizes the metastable intermediate state through the hydrophilic interaction network and favors the conformational transition of the receptor towards the active state. This research provides a structural template towards the special pharmacological outcome triggered by conformational mutation and sheds light on future structural or pharmacological studies among class A GPCRs.