Laprairie Robert B, Kulkarni Pushkar M, Deschamps Jeffrey R, Kelly Melanie E M, Janero David R, Cascio Maria G, Stevenson Lesley A, Pertwee Roger G, Kenakin Terrence P, Denovan-Wright Eileen M, Thakur Ganesh A
Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University , Boston, Massachusetts 02115, United States.
Naval Research Laboratory , Code 6930, 4555 Overlook Avenue, Washington, D.C. 20375, United States.
ACS Chem Neurosci. 2017 Jun 21;8(6):1188-1203. doi: 10.1021/acschemneuro.6b00310. Epub 2017 Feb 7.
The cannabinoid 1 receptor (CB1R) is one of the most widely expressed metabotropic G protein-coupled receptors in brain, and its participation in various (patho)physiological processes has made CB1R activation a viable therapeutic modality. Adverse psychotropic effects limit the clinical utility of CB1R orthosteric agonists and have promoted the search for CB1R positive allosteric modulators (PAMs) with the promise of improved drug-like pharmacology and enhanced safety over typical CB1R agonists. In this study, we describe the synthesis and in vitro and ex vivo pharmacology of the novel allosteric CB1R modulator GAT211 (racemic) and its resolved enantiomers, GAT228 (R) and GAT229 (S). GAT211 engages CB1R allosteric site(s), enhances the binding of the orthosteric full agonist [H]CP55,490, and reduces the binding of the orthosteric antagonist/inverse agonist [H]SR141716A. GAT211 displayed both PAM and agonist activity in HEK293A and Neuro2a cells expressing human recombinant CB1R (hCB1R) and in mouse-brain membranes rich in native CB1R. GAT211 also exhibited a strong PAM effect in isolated vas deferens endogenously expressing CB1R. Each resolved and crystallized GAT211 enantiomer showed a markedly distinctive pharmacology as a CB1R allosteric modulator. In all biological systems examined, GAT211's allosteric agonist activity resided with the R-(+)-enantiomer (GAT228), whereas its PAM activity resided with the S-(-)-enantiomer (GAT229), which lacked intrinsic activity. These results constitute the first demonstration of enantiomer-selective CB1R positive allosteric modulation and set a precedent whereby enantiomeric resolution can decisively define the molecular pharmacology of a CB1R allosteric ligand.
大麻素1受体（CB1R）是大脑中表达最广泛的代谢型G蛋白偶联受体之一，其参与各种（病理）生理过程使得CB1R激活成为一种可行的治疗方式。不良精神效应限制了CB1R正位激动剂的临床应用，并促使人们寻找CB1R正变构调节剂（PAMs），以期获得比典型CB1R激动剂更好的类药药理学特性和更高的安全性。在本研究中，我们描述了新型变构CB1R调节剂GAT211（消旋体）及其拆分对映体GAT228（R）和GAT229（S）的合成以及体外和体内药理学特性。GAT211作用于CB1R变构位点，增强正位全激动剂[H]CP55,490的结合，并减少正位拮抗剂/反向激动剂[H]SR141716A的结合。GAT211在表达人重组CB1R（hCB1R）的HEK293A和Neuro2a细胞以及富含天然CB1R的小鼠脑膜中表现出PAM和激动剂活性。GAT211在内源性表达CB1R的离体输精管中也表现出强烈的PAM效应。每种拆分并结晶的GAT211对映体作为CB1R变构调节剂均表现出明显独特的药理学特性。在所研究的所有生物系统中，GAT211的变构激动剂活性存在于R-(+)-对映体（GAT228）中，而其PAM活性存在于缺乏内在活性的S-(-)-对映体（GAT229）中。这些结果首次证明了对映体选择性CB1R正变构调节，并开创了一个先例，即对映体拆分可以决定性地定义CB1R变构配体的分子药理学。
