The binding characteristics and orientation of a novel radioligand with distinct properties at 5-HT3A and 5-HT3AB receptors

NEUROPHARMACOLOGY

卷:86

Article

Thompson, Andrew J.²  Verheij, Mark H. P.¹  Verbeek, Joost³  Windhorst, Albert D.³  de Esch, Iwan J. P.¹  Lummis, Sarah C. R.² 

[1] Vrije Univ Amsterdam, Fac Sci, Div Med Chem, AIMMS, Amsterdam, Netherlands

[2] Univ Cambridge, Dept Biochem, Cambridge CB2 1QW, England

[3] Vrije Univ Amsterdam, Med Ctr, Dept Radiol & Nucl Med, Amsterdam, Netherlands

关键词: Antagonist;    Cys-loop;    Ion channel;    Radioligand;    5-HT3;    Agonist;   

DOI  :  10.1016/j.neuropharm.2014.08.008

来源: Elsevier

【 摘 要 】

VUF10166 (2-chloro-3-(4-methyl piperazin-l-yl)quinoxaline) is a ligand that binds with high affinity to 5-HT3 receptors. Here we synthesise [H-3]VUF10166 and characterise its binding properties at 5-HT(3)A and 5-HT(3)AB receptors. At 5-HT(3)A receptors [H-3]VUF10166 displayed saturable binding with a K-d of 0.18 nM. Kinetic measurements gave monophasic association (6.25 x 10(7) M-1 min(-1)) and dissociation (0.01 min(-1)) rates that yielded a similar K-d value (0.16 nM). At 5-HT(3)AB receptors two association (6.15 x 10(-7), 7.23 M-1 min(-1)) and dissociation (0.024, 0.162 min(-1)) rates were seen, yielding K-d values (0.38 nM and 22 nM) that were consistent with values obtained in saturation (K-d = 0.74 nM) and competition (K-i = 37 nM) binding experiments respectively. At both receptor types, specific binding was inhibited by classical 5-HT3 receptor-selective orthosteric ligands (5-HT, allosetron, d-tubocurarine, granisetron, mCPBG, MDL72222, quipazine), but not by non-competitive antagonists (bilobalide, ginkgolide B, picrotoxin) or competitive ligands of other Cys-loop receptors (ACh, bicuculline, glycine, gabazine). To explore VUF10166 ligand-receptor interactions we used in silico modelling and docking, and tested the predictions using site directed mutagenesis. The data suggest that VUF10166 adopts a similar orientation to 5-HT3 receptor agonists bound in AChBP (varenicline) and 5HTBP (5-HT) crystal structures. (C) 2014 Published by Elsevier Ltd.

【 授权许可】

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