Departments of Computer Science, Molecular and Cellular Physiology, and Structural Biology, and Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, 94305, USA.
Merck & Co., Boston, MA, 02110, USA.
Nat Commun. 2019 Jul 23;10(1):3289. doi: 10.1038/s41467-019-11062-7.
Allosteric modulators are highly desirable as drugs, particularly for G-protein-coupled receptor (GPCR) targets, because allosteric drugs can achieve selectivity between closely related receptors. The mechanisms by which allosteric modulators achieve selectivity remain elusive, however, particularly given recent structures that reveal similar allosteric binding sites across receptors. Here we show that positive allosteric modulators (PAMs) of the M1 muscarinic acetylcholine receptor (mAChR) achieve exquisite selectivity by occupying a dynamic pocket absent in existing crystal structures. This cryptic pocket forms far more frequently in molecular dynamics simulations of the M1 mAChR than in those of other mAChRs. These observations reconcile mutagenesis data that previously appeared contradictory. Further mutagenesis experiments validate our prediction that preventing cryptic pocket opening decreases the affinity of M1-selective PAMs. Our findings suggest opportunities for the design of subtype-specific drugs exploiting cryptic pockets that open in certain receptors but not in other receptors with nearly identical static structures.
变构调节剂是非常理想的药物，特别是对于 G 蛋白偶联受体 (GPCR) 靶点，因为变构药物可以在密切相关的受体之间实现选择性。然而，变构调节剂实现选择性的机制仍然难以捉摸，特别是考虑到最近的结构揭示了受体之间存在相似的变构结合位点。在这里，我们表明 M1 毒蕈碱乙酰胆碱受体 (mAChR) 的正变构调节剂 (PAM) 通过占据现有晶体结构中不存在的动态口袋来实现极高的选择性。在 M1 mAChR 的分子动力学模拟中，这个隐蔽口袋比在其他 mAChR 中的出现频率高得多。这些观察结果调和了先前似乎相互矛盾的诱变数据。进一步的诱变实验验证了我们的预测，即阻止隐蔽口袋打开会降低 M1 选择性 PAM 的亲和力。我们的发现表明，利用仅在某些受体中打开而在其他具有几乎相同静态结构的受体中不打开的隐蔽口袋设计亚型特异性药物具有机会。
