Allosteric modulation of the cannabinoid CB1 receptor
Allosteric modulation of the cannabinoid CB1 receptor
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DOI：
10.1124/mol.105.016162
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发表时间：
2005-11-01
影响因子：
3.6
通讯作者：
Ross, RA
中科院分区：
文献类型：
--
作者：
Price, MR;Baillie, GL;Ross, RA
我们研究了三个新化合物的药理学，（5-氯-3-乙基-1H-吲哚-2-羧酸[2-（4-哌啶-1-基-苯基）-乙基]-酰胺），货号27759（3-乙基-5-氟-1H-吲哚-2-羧酸[2-{4-二甲基氨基-苯基}乙基]-酰胺），和在大麻素CB 1受体上的EST 29647（5-氯-3-乙基-1H-吲哚-2-羧酸（1-苄基-吡咯烷-3-基）-酰胺，2-烯二酸盐）。在平衡结合试验中，所述化合物显著增加了CB 1受体激动剂[H-3]CP 55，940 [（1 R，3R，4 R）3-[2-羟基-4-（1，1-二甲基庚基）苯基]-4-（3-羟丙基）环己烷-1-醇]的结合，表明正协同变构效应。相同化合物导致CB 1受体反向激动剂[H-3]SR 141716 A [N-（哌啶-1-基）-5-（4-氯苯基）-1-（2，4-二氯苯基）-4-甲基-1H-吡唑-3-甲酰胺盐酸盐]的特异性结合显著但不完全降低，表明负结合协同性有限。根据变构三元复合物模型对数据进行分析，结果显示，当放射性配体为[H-3]CP 55，940或[H-3]SR 141716 A时，各化合物的估计亲和力无显著差异。然而，当针对[H-3]CP 55，940测定时，调节剂和放射性配体之间相互作用的估计协同因子大于1，当针对[H-3]SR 141716 A测定时，估计协同因子小于1。[H-3]CP 55，940解离动力学研究也验证了化合物的变构性质，因为它们都显著降低了放射性配体解离。这些数据表明，所述化合物与CB 1受体变构结合，并引起构象变化，从而增加对正构结合位点的激动剂亲和力。然而，与结合试验相反，CB 1化合物表现为受体功能的不可逾越的拮抗剂;在报告基因试验、鸟苷5 '-O-（3-[S-35]硫代）三磷酸结合试验和小鼠输精管试验中，它们引起CB 1受体激动剂的E-max值显著降低。这些数据首次清楚地表明，大麻素CB 1受体含有一个可以被合成小分子配体识别的变构结合位点。
We investigated the pharmacology of three novel compounds, Org 27569 (5-chloro-3-ethyl-1H-indole-2-carboxylic acid [2-(4-piperidin-1-yl-phenyl)-ethyl]-amide), Org 27759 (3-ethyl-5-fluoro-1H-indole-2-carboxylic acid [2-94-dimethylamino-phenyl)ethyl]-amide), and Org 29647 (5-chloro-3-ethyl-1H-indole-2-carboxylic acid (1-benzyl-pyrrolidin-3-yl)-amide, 2-enedioic acid salt), at the cannabinoid CB1 receptor. In equilibrium binding assays, the Org compounds significantly increased the binding of the CB1 receptor agonist [H-3]CP 55,940 [(1R,3R,4R)3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-4-(3-hydroxypropyl)cyclohexan-1-ol], indicative of a positively cooperative allosteric effect. The same compounds caused a significant, but incomplete, decrease in the specific binding of the CB1 receptor inverse agonist [H-3]SR 141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboximide hydrochloride], indicative of a limited negative binding cooperativity. Analysis of the data according to an allosteric ternary complex model revealed that the estimated affinity of each Org compound was not significantly different when the radioligand was [H-3]CP 55,940 or [H-3]SR 141716A. However, the estimated cooperatively factor for the interaction between modulator and radioligand was greater than 1 when determined against [H-3]CP 55,940 and less than 1 when determined against [H-3]SR 141716A. [H-3]CP 55,940 dissociation kinetic studies also validated the allosteric nature of the Org compounds, because they all significantly decreased radioligand dissociation. These data suggest that the Org compounds bind allosterically to the CB1 receptor and elicit a conformational change that increases agonist affinity for the orthosteric binding site. In contrast to the binding assays, however, the Org compounds behaved as insurmountable antagonists of receptor function; in the reporter gene assay, the guanosine 5'-O-(3-[S-35]thio)triphosphate binding assay and the mouse vas deferens assay they elicited a significant reduction in the E-max value for CB1 receptor agonists. The data presented clearly demonstrate, for the first time, that the cannabinoid CB1 receptor contains an allosteric binding site that can be recognized by synthetic small molecule ligands.