McFadyen I J, Houshyar H, Liu-Chen L Y, Woods J H, Traynor J R
Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA.
Mol Pharmacol. 2000 Oct;58(4):669-76. doi: 10.1124/mol.58.4.669.
The steroid SC17599 (17alpha-acetoxy-6-dimethylaminomethyl-21-fluoro-3-ethoxypregna -3, 5-dien-20-one) has mu-opioid actions in vivo. The ability of SC17599 to interact with opioid receptors has been studied using radioligand and [(35)S]guanosine-5'-O-(3-thio)triphosphate (GTPgammaS) binding assays. SC17599 bound to mu-opioid receptors in SH-SY5Y neuroblastoma cells and to recombinant receptors expressed in rat C6 glioma cells and Chinese hamster ovary cells with good affinity and with greater than 100-fold selectivity for mu- over both delta- and kappa-opioid receptors. Binding was much reduced when aspartate 147 in the wild-type mu-opioid receptor was replaced with asparagine. The affinity of SC17599 for the mu-opioid receptor was decreased in the presence of sodium ions, indicating agonist activity. SC17599 stimulated the binding of [(35)S]GTPgammaS in a naloxone-reversible manner with good potency and maximal effect equivalent to that of the mu-opioid agonists fentanyl and [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin. In rat brain membranes, SC17599-mediated stimulation of [(35)S]GTPgammaS binding was reversed by the antagonist naltrexone. SC17599 lacks an aromatic ring and para-hydroxyl substituent considered critical in the pharmacophore for mu-opioids. The structural relationship between SC17599 and more traditional opioid ligands was investigated through genetic algorithm-based modeling techniques for pharmacophore generation (GASP) and ligand-receptor docking (GOLD). The relatively planar and electron-rich A ring of the steroid compensated for the lack of aromaticity. Modeling of ligand-receptor docking showed that both morphine and SC17599 occupy the same binding pocket within the transmembrane helix bundle of the mu-opioid receptor and that the relationship between their binding modes largely mimicked the pharmacophore alignment.
类固醇SC17599（17α-乙酰氧基-6-二甲基氨基甲基-21-氟-3-乙氧基孕甾-3,5-二烯-20-酮）在体内具有μ-阿片样作用。已使用放射性配体和[³⁵S]鸟苷-5'-O-（3-硫代）三磷酸（GTPγS）结合试验研究了SC17599与阿片受体相互作用的能力。SC17599以良好的亲和力与SH-SY5Y神经母细胞瘤细胞中的μ-阿片受体以及大鼠C6胶质瘤细胞和中国仓鼠卵巢细胞中表达的重组受体结合，并且对μ-阿片受体的选择性比对δ-和κ-阿片受体高100倍以上。当野生型μ-阿片受体中的天冬氨酸147被天冬酰胺取代时，结合大大减少。在存在钠离子的情况下，SC17599对μ-阿片受体的亲和力降低，表明其具有激动剂活性。SC17599以纳洛酮可逆的方式刺激[³⁵S]GTPγS的结合，效力良好，最大效应与μ-阿片激动剂芬太尼和[D-Ala²，N-Me-Phe⁴，Gly⁵-ol]-脑啡肽相当。在大鼠脑膜中，拮抗剂纳曲酮可逆转SC17599介导的[³⁵S]GTPγS结合刺激。SC17599缺乏被认为在μ-阿片类药物药效团中至关重要的芳香环和对羟基取代基。通过基于遗传算法的药效团生成建模技术（GASP）和配体-受体对接（GOLD）研究了SC17599与更传统的阿片配体之间的结构关系。类固醇相对平面且富含电子的A环弥补了芳香性的不足。配体-受体对接模型表明，吗啡和SC17599都占据μ-阿片受体跨膜螺旋束内的同一结合口袋，并且它们结合模式之间的关系在很大程度上模仿了药效团排列。
