Characterizing New Fluorescent Tools for Studying 5-HT3 Receptor Pharmacology

Jack, Thomas; Simonin, Jonathan; Ruepp, Marc-David; Thompson, Andrew James; Gertsch, Jürg; Lochner, Martin (2015). Characterizing New Fluorescent Tools for Studying 5-HT3 Receptor Pharmacology. Neuropharmacology, 90, pp. 63-73. Elsevier 10.1016/j.neuropharm.2014.11.007

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The pharmacological characterization of ligands depends upon the ability to accurately measure their binding properties. Fluorescence provides an alternative to more traditional approaches such as radioligand binding. Here we describe the binding and spectroscopic properties of eight fluorescent 5-HT3 receptor ligands. These were tested on purified receptors, expressed receptors on live cells, or in vivo. All compounds had nanomolar affinities with fluorescent properties extending from blue to near infra-red emission. A fluorescein-derivative had the highest affinity as measured by fluorescence polarization (FP; 1.14 nM), flow cytometry (FC; 3.23 nM) and radioligand binding (RB; 1.90 nM). Competition binding with unlabeled 5-HT3 receptor agonists (5-HT, mCPBG, quipazine) and antagonists (granisetron, palonosetron, tropisetron) yielded similar affinities in all three assays. When cysteine substitutions were introduced into the 5-HT3 receptor binding site the same changes in binding affinity were seen for both granisetron and the fluorescein-derivative, suggesting that they both adopt orientations that are consistent with co-crystal structures of granisetron with a homologous protein (5HTBP). As expected, in vivo live imaging in anaesthetized mice revealed staining in the abdominal cavity in intestines, but also in salivary glands. The unexpected presence of 5-HT3 receptors in mouse salivary glands was confirmed by Western blots. Overall, these results demonstrate the wide utility of our new high-affinity fluorescently-labeled 5-HT3 receptor probes, ranging from in vitro receptor pharmacology, including FC and FP ligand competition, to live imaging of 5-HT3 expressing tissues.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP)
04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Biochemistry and Molecular Medicine

UniBE Contributor:

Jack, Thomas; Simonin, Jonathan; Ruepp, Marc-David; Thompson, Andrew James; Gertsch, Jürg and Lochner, Martin


500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry
600 Technology > 610 Medicine & health








Martin Lochner

Date Deposited:

10 Dec 2014 11:45

Last Modified:

24 Aug 2015 15:14

Publisher DOI:


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