A modular click ligand-directed approach to label endogenous dopamine D1 receptors in live cells

Most luminescence-based technologies to determine the pharmacological properties of G Protein-Coupled Receptors (GPCRs) rely on the overexpression of genetically modified receptors. However, it is essential to develop approaches allowing the specific labelling of native receptors. Here we report an innovative approach based on the use of molecular modules to build fluorescent ligand-directed probes that can label aminergic GPCRs. Such probes are readily prepared with a click reaction between a ligand that may include nucleophilic groups and a fluorescent electrophilic linker. The rapidity of click reaction before receptor labelling prevents a side reaction between the nucleophilic ligand and the electrophile. This approach allowed us to label D1 receptor in transfected cells and native receptors in neural cell lines, leaving the receptor fully functional. This approach will pave the way to develop new reagents and assays with which to monitor endogenous GPCRs’ distribution, trafficking, activity or binding properties in their native environment. G protein-coupled receptors (GPCR) are a complex superfamily of membrane proteins that have a key role in regulating various physiological processes, however, the specific labelling of native GPCRs to monitor their function remains challenging. Here, the authors report a modular click ligand-directed approach to covalently attach fluorescent dyes to endogenous dopamine D1 receptors in live cells.