Fluorescent ligands for dopamine D2/D3 receptors
Anni Allikalt, Nirupam Purkayastha, Khajidmaa Flad, Maximilian F. Schmidt, Alina Tabor, Peter Gmeiner, Harald Hübner, Dorothée Weikert
Abstract
Abstract Fluorescent ligands are versatile tools for the study of G protein-coupled receptors. Depending on the fluorophore, they can be used for a range of different applications, including fluorescence microscopy and bioluminescence or fluorescence resonance energy transfer (BRET or FRET) assays. Starting from phenylpiperazines and indanylamines, privileged scaffolds for dopamine D 2 -like receptors, we developed dansyl-labeled fluorescent ligands that are well accommodated in the binding pockets of D 2 and D 3 receptors. These receptors are the target proteins for the therapy for several neurologic and psychiatric disorders, including Parkinson’s disease and schizophrenia. The dansyl-labeled ligands exhibit binding affinities up to 0.44 nM and 0.29 nM at D 2 R and D 3 R, respectively. When the dansyl label was exchanged for sterically more demanding xanthene or cyanine dyes, fluorescent ligands 10a-c retained excellent binding properties and, as expected from their indanylamine pharmacophore, acted as agonists at D 2 R. While the Cy3B-labeled ligand 10b was used to visualize D 2 R and D 3 R on the surface of living cells by total internal reflection microscopy, ligand 10a comprising a rhodamine label showed excellent properties in a NanoBRET binding assay at D 3 R.