Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Melbourne, Australia (K.J.G., J.D., A.C., K.L.); Laboratory of Molecular Neuropharmacology and Bioinformatics, Institut de Neurociències and Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain (J.G.); Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, Bellaterra, Spain (J.G.); and Unitat de Neurociència Traslacional, Parc Taulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí and Institut de Neurociències, Universitat Autònoma de Barcelona, Bellaterra, Spain (J.G.).
Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Melbourne, Australia (K.J.G., J.D., A.C., K.L.); Laboratory of Molecular Neuropharmacology and Bioinformatics, Institut de Neurociències and Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain (J.G.); Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, Bellaterra, Spain (J.G.); and Unitat de Neurociència Traslacional, Parc Taulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí and Institut de Neurociències, Universitat Autònoma de Barcelona, Bellaterra, Spain (J.G.)
Mol Pharmacol. 2020 Jan;97(1):35-45. doi: 10.1124/mol.119.118091. Epub 2019 Nov 8.
Current operational models of agonism and allosterism quantify ligand actions at receptors where agonist concentration-response relationships are nonhyperbolic by introduction of a transducer slope that relates receptor occupancy to response. However, for some receptors nonhyperbolic concentration-response relationships arise from multiple endogenous agonist molecules binding to a receptor in a cooperative manner. Thus, we developed operational models of agonism in systems with cooperative agonist binding and evaluated the models by simulating data describing agonist effects. The models were validated by analyzing experimental data demonstrating the effects of agonists and allosteric modulators at receptors where agonist binding follows hyperbolic (M muscarinic acetylcholine receptors) or nonhyperbolic relationships (metabotropic glutamate receptor 5 and calcium-sensing receptor). For hyperbolic agonist concentration-response relationships, no differences in estimates of ligand affinity, efficacy, or cooperativity were observed when the slope was assigned to either a transducer slope or agonist binding slope. In contrast, for receptors with nonhyperbolic agonist concentration-response relationships, estimates of ligand affinity, efficacy, or cooperativity varied depending on the assignment of the slope. The extent of this variation depended on the magnitude of the slope value and agonist efficacy, and for allosteric modulators on the magnitude of cooperativity. The modified operational models described herein are well suited to analyzing agonist and modulator interactions at receptors that bind multiple orthosteric agonists in a cooperative manner. Accounting for cooperative agonist binding is essential to accurately quantify agonist and drug actions. SIGNIFICANCE STATEMENT: Some orthosteric agonists bind to multiple sites on a receptor, but current analytical methods to characterize such interactions are limited. Herein, we develop and validate operational models of agonism and allosterism for receptors with multiple orthosteric binding sites, and demonstrate that such models are essential to accurately quantify agonist and drug actions. These findings have important implications for the discovery and development of drugs targeting receptors such as the calcium-sensing receptor, which binds at least five calcium ions.
当前的激动剂和变构作用操作模型通过引入一个转导斜率来量化配体在受体上的作用，该斜率将受体占有率与反应相关联，从而使激动剂浓度-反应关系呈非双曲线关系。然而，对于一些受体，非双曲线浓度-反应关系是由多个内源性激动剂分子以协同方式结合受体引起的。因此，我们开发了具有协同激动剂结合的激动作用操作模型，并通过模拟描述激动剂作用的数据来评估模型。通过分析表明激动剂结合遵循双曲线（M 毒蕈碱乙酰胆碱受体）或非双曲线关系（代谢型谷氨酸受体 5 和钙敏感受体）的激动剂和变构调节剂在受体上的作用的实验数据来验证模型。对于双曲线激动剂浓度-反应关系，当斜率分配给转导斜率或激动剂结合斜率时，没有观察到配体亲和力、效力或协同性估计值的差异。相比之下，对于具有非双曲线激动剂浓度-反应关系的受体，配体亲和力、效力或协同性的估计值取决于斜率的分配。这种变化的程度取决于斜率值和激动剂效力的大小，对于变构调节剂，取决于协同性的大小。本文描述的改进的操作模型非常适合分析以协同方式结合多个正构激动剂的受体上的激动剂和调节剂相互作用。考虑协同激动剂结合对于准确量化激动剂和药物作用至关重要。意义声明：一些正构激动剂结合到受体上的多个位点，但目前用于表征这种相互作用的分析方法是有限的。本文中，我们开发并验证了具有多个正构结合位点的激动剂和变构作用的操作模型，并证明了这些模型对于准确量化激动剂和药物作用是必不可少的。这些发现对于靶向受体（如钙敏感受体）的药物的发现和开发具有重要意义，钙敏感受体至少结合五个钙离子。
