A two-state model for the kinetics of competitive radioligand binding

Guo, Dong; Peletier, Lambertus A; Bridge, Lloyd; Keur, Wesley; de Vries, Henk; Zweemer, Annelien; Heitman, Laura H; Ijzerman, Adriaan P

Abstract

© 2018 The Authors. British Journal of Pharmacology published by John Wiley & Sons Ltd on behalf of British Pharmacological Society. Background and Purpose: Ligand–receptor binding kinetics is receiving increasing attention in the drug research community. The Motulsky and Mahan model, a one-state model, offers a method for measuring the binding kinetics of an unlabelled ligand, with the assumption that the labelled ligand has no preference while binding to distinct states or conformations of a drug target. As such, the one-state model is not applicable if the radioligand displays biphasic binding kinetics to the receptor. Experimental Approach: We extended the Motulsky and Mahan model to a two-state model, in which the kinetics of the unlabelled competitor binding to different receptor states (R 1 and R 2 ) can be measured. With this extended model, we determined the binding kinetics of unlabelled N-5′-ethylcarboxamidoadenosine (NECA), a representative agonist for the adenosine A 1 receptor. Subsequently, an application of the model was exemplified by measuring the binding kinetics of other A 1 receptor ligands. In addition, limitations of the model were investigated as well. Key Results: The kinetic rate constants of unlabelled NECA were comparable with the results of kinetic radioligand binding assays in which [ 3 H]-NECA was used. The model was further validated by good correlation between simulated results and the experimental data. Conclusion: The two-state model is sufficient to analyse the binding kinetics of an unlabelled ligand, when a radioligand shows biphasic association characteristics. We expect this two-state model to have general applicability for other targets as well.

• Journal Article Type: Article
• Acceptance Date: Feb 19, 2018
• Online Publication Date: Feb 27, 2018
• Publication Date: May 1, 2018
• Deposit Date: Feb 28, 2018
• Publicly Available Date: May 2, 2018
• Journal: British Journal of Pharmacology
• Print ISSN: 0007-1188
• Electronic ISSN: 1476-5381
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 175
• Issue: 10
• Pages: 1719-1730
• DOI: https://doi.org/10.1111/bph.14184
• Keywords: two-state model, kinetics, competitive radioligand blinding
• Public URL: https://uwe-repository.worktribe.com/output/867494
• Publisher URL: http://dx.doi.org/10.1111/bph.14184
• Contract Date: Feb 28, 2018