Molecular Determinants of Allosteric Modulation at the M1 Muscarinic Acetylcholine Receptor
Molecular Determinants of Allosteric Modulation at the M1 Muscarinic Acetylcholine Receptor
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DOI：
10.1074/jbc.m113.539080
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发表时间：
2014-02-28
影响因子：
4.8
通讯作者：
Christopoulos, Arthur
中科院分区：
文献类型：
--
作者：
Abdul-Ridha, Alaa;Lopez, Laura;Christopoulos, Arthur
背景：BQCA是M-1 mAChR的选择性变构调节剂。结果：使用诱变和分子模拟鉴定了控制BQCA活性的残基。结论：BQCA可能占据了一个口袋重叠原型mAChR调制器，并通过与正构配体的协同性获得选择性。重要性：了解BQCA功能的结构基础可以为设计更有针对性的变构配体提供见解。苄基喹诺酮羧酸（BQCA）是M-1毒蕈碱乙酰胆碱受体（mAChR）上乙酰胆碱的选择性正变构调节剂的前所未有的例子。为了探索其选择性的结构基础，我们利用定点诱变，分析建模，和分子动力学描绘的M-1 mAChR的区域，管理调制器结合和传输的协同性。我们鉴定了跨膜结构域2（TMII）中的Tyr-85（2.64）、第二胞外环（ECL 2）中的Tyr-179和Phe-182以及TMVII中的Glu-397（7.32）和Trp-400（7.35），这些残基有助于M-1 mAChR处的BQCA结合口袋以及与正构激动剂卡巴胆碱的协同性传递。因此，BQCA结合口袋部分重叠的M-1 mAChR的细胞外前庭与先前描述的共同变构网站，这表明其高亚型选择性来自该区域以外的额外的接触或通过亚型特异性的协同机制。形成正构结合口袋的氨基酸残基突变导致卡巴胆碱反应丧失，BQCA可以挽救卡巴胆碱反应。其中两个残基（Leu-102（3.29）和Asp-105（3.32））也被鉴定为调节剂结合亲和力的间接贡献者。这种对BQCA结合和功能的结构基础的新见解可以指导具有定制药理学性质的新变构配体的设计。
Background: BQCA is a selective allosteric modulator of the M-1 mAChR. Results: Residues that govern BQCA activity were identified using mutagenesis and molecular modeling. Conclusion: BQCA likely occupies a pocket overlapping prototypical mAChR modulators and gains selectivity through cooperativity with orthosteric ligands. Significance: Understanding the structural basis of BQCA function can provide insight into the design of more tailored allosteric ligands.Benzylquinolone carboxylic acid (BQCA) is an unprecedented example of a selective positive allosteric modulator of acetylcholine at the M-1 muscarinic acetylcholine receptor (mAChR). To probe the structural basis underlying its selectivity, we utilized site-directed mutagenesis, analytical modeling, and molecular dynamics to delineate regions of the M-1 mAChR that govern modulator binding and transmission of cooperativity. We identified Tyr-85(2.64) in transmembrane domain 2 (TMII), Tyr-179 and Phe-182 in the second extracellular loop (ECL2), and Glu-397(7.32) and Trp-400(7.35) in TMVII as residues that contribute to the BQCA binding pocket at the M-1 mAChR, as well as to the transmission of cooperativity with the orthosteric agonist carbachol. As such, the BQCA binding pocket partially overlaps with the previously described common allosteric site in the extracellular vestibule of the M-1 mAChR, suggesting that its high subtype selectivity derives from either additional contacts outside this region or through a subtype-specific cooperativity mechanism. Mutation of amino acid residues that form the orthosteric binding pocket caused a loss of carbachol response that could be rescued by BQCA. Two of these residues (Leu-102(3.29) and Asp-105(3.32)) were also identified as indirect contributors to the binding affinity of the modulator. This new insight into the structural basis of binding and function of BQCA can guide the design of new allosteric ligands with tailored pharmacological properties.