Muscarinic Receptors as Model Targets and Antitargets for Structure-Based Ligand Discovery
作者:Andrew C. Kruse、Dahlia R. Weiss、Mario Rossi、Jianxin Hu、Kelly Hu、Katrin Eitel、Peter Gmeiner、Jürgen Wess、Brian K. Kobilka、Brian K. Shoichet
DOI:10.1124/mol.113.087551
日期:2013.10
G protein–coupled receptors (GPCRs) regulate virtually all aspects of human physiology and represent an important class of therapeutic drug targets. Many GPCR-targeted drugs resemble endogenous agonists, often resulting in poor selectivity among receptor subtypes and restricted pharmacologic profiles. The muscarinic acetylcholine receptor family exemplifies these problems; thousands of ligands are known, but few are receptor subtype–selective and nearly all are cationic in nature. Using structure-based docking against the M2 and M3 muscarinic receptors, we screened 3.1 million molecules for ligands with new physical properties, chemotypes, and receptor subtype selectivities. Of 19 docking-prioritized molecules tested against the M2 subtype, 11 had substantial activity and 8 represented new chemotypes. Intriguingly, two were uncharged ligands with low micromolar to high nanomolar K i values, an observation with few precedents among aminergic GPCRs. To exploit a single amino-acid substitution among the binding pockets between the M2 and M3 receptors, we selected molecules predicted by docking to bind to the M3 and but not the M2 receptor. Of 16 molecules tested, 8 bound to the M3 receptor. Whereas selectivity remained modest for most of these, one was a partial agonist at the M3 receptor without measurable M2 agonism. Consistent with this activity, this compound stimulated insulin release from a mouse β -cell line. These results support the ability of structure-based discovery to identify new ligands with unexplored chemotypes and physical properties, leading to new biologic functions, even in an area as heavily explored as muscarinic pharmacology.
G 蛋白偶联受体(GPCR)几乎调节人体生理的所有方面,是一类重要的治疗药物靶点。许多 GPCR 靶向药物与内源性激动剂相似,往往导致受体亚型之间的选择性差和药理作用受限。毒蕈碱乙酰胆碱受体家族就是这些问题的典型代表;目前已知的配体有数千种,但很少具有受体亚型选择性,而且几乎所有配体都是阳离子性质的。通过与 M2 和 M3 肌卡因受体进行基于结构的对接,我们筛选了 310 万个分子,以寻找具有新的物理特性、化学类型和受体亚型选择性的配体。在针对 M2 亚型测试的 19 个对接优先分子中,11 个具有很强的活性,8 个代表了新的化学型。耐人寻味的是,有两种配体不带电荷,K i 值从微摩尔到纳摩尔不等,这在胺能 GPCR 中鲜有先例。为了利用 M2 和 M3 受体之间结合口袋中的单个氨基酸取代,我们选择了通过对接预测能与 M3 而非 M2 受体结合的分子。在测试的 16 个分子中,有 8 个与 M3 受体结合。虽然其中大多数的选择性仍然不高,但有一种是 M3 受体的部分激动剂,而没有可测量的 M2 激动作用。与这种活性相一致的是,这种化合物能刺激小鼠 β 细胞系释放胰岛素。这些结果证明了基于结构的发现方法有能力找出具有未开发的化学类型和物理性质的新配体,从而实现新的生物功能,即使是在毒蕈碱药理学这样已被大量开发的领域也是如此。