High-affinity agonist binding correlates with efficacy (intrinsic activity) at the human serotonin 5-HT2A and 5-HT2C receptors:: Evidence favoring the ternary complex and two-state models of agonist action
High-affinity agonist binding correlates with efficacy (intrinsic activity) at the human serotonin 5-HT2A and 5-HT2C receptors:: Evidence favoring the ternary complex and two-state models of agonist action
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DOI：
10.1046/j.1471-4159.1999.0722127.x
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发表时间：
1999-05-01
影响因子：
4.7
通讯作者：
Hartig, PR
中科院分区：
文献类型：
--
作者：
Fitzgerald, LW;Conklin, DS;Hartig, PR
许多受体-G蛋白功能的现代模型假设高亲和力激动剂结合和功效之间存在直接关系。这一假设的有效性最近受到质疑的5-羟色胺5-HT 2A受体。我们研究了各种配体在激活磷酸肌醇水解中的内在活性，并测量了它们各自对5-HT 2C（VNV亚型）和5-HT 2A受体的高亲和力和低亲和力状态的结合亲和力。使用1-氨基-1，2-二氢吲哚-3-酮测定受体的高亲和力状态的配体结合亲和力。（4-[I-125]碘-2，5-二甲氧基苯基）-2-氨基丙烷，而使用[H-3]美舒麦角和N-[H-3]甲基螺哌隆，在过量鸟嘌呤核苷酸[鸟苷5 '-O-（3-硫代三磷酸）]，以分别定义与5-HT 2C和5-HT 2A受体的低亲和力状态的结合。拮抗剂以相似的亲和力标记每个受体的高亲和力和低亲和力状态。以前鉴定的5-HT 2C受体的反向激动剂在我们的系统中表现为沉默拮抗剂，即使当受体以相对高的密度过表达时。相反，激动剂与5-HT 2A和5-HT 2C受体的高亲和力和低亲和力状态的差异结合能力与其内在活性高度相关（r（2）分别为0.86和0.96）。这些数据表明，高亲和力激动剂状态可以解释对人5-HT 2A或5-HT 2C受体的激动剂功效，而无需考虑受体-配体复合物的额外过渡或活性状态。本文所述的程序可以通过仅从配体结合测定预测配体的固有活性来加速药物发现工作。
Many modern models of receptor-G protein function assume that there is a direct relationship between high-affinity agonist binding and efficacy. The validity of this assumption has been recently questioned for the serotonin 5-HT2A receptor. We examined the intrinsic activities of various ligands in activating phosphoinositide hydrolysis and measured their respective binding affinities to the high- and low-affinity states of the 5-HT2C (VNV isoform) and 5-HT2A receptors. Ligand binding affinities for the high-affinity state of the receptors were determined using 1-(4-[I-125]iodo-2,5-dimethoxyphenyl)-2-aminopropane, whereas [H-3]mesulergine and N-[H-3]methylspiperone were used, in the presence of excess guanine nucleotide [guanosine 5'-O-(3-thiotriphosphate)], to define binding to the low-affinity state of the 5-HT2C and 5-HT2A receptors, respectively. Antagonists labeled the high- and low-affinity states of each receptor with comparable affinities. Previously identified inverse agonists of the 5-HT2C receptor behaved as silent antagonists in our systems even when the receptor was overexpressed at a relatively high density. In contrast, the ability of agonists to bind differentially to the high- and low-affinity states of the 5-HT2A and 5-HT2C receptors was highly correlated (r(2) = 0.86 and 0.96, respectively) with their intrinsic activities. These data suggest that high-affinity agonist states can account for agonist efficacy at human 5-HT2A or 5-HT2C receptors without the need for considering additional transition or active states of the receptor-ligand complex. The procedure described herein may expedite drug discovery efforts by predicting intrinsic activities of ligands solely from ligand binding assays.