Development and Characterization of a Highly Selective Turn-On Fluorescent Ligand for β3-Adrenergic Receptor

For the precise visualization of GPCR, subtype selectivity of turn-on fluorescent ligands is of major relevance. Although there are many thriving fl-adrenergic receptors (fl-ARs) probes, none of them are selective to the fl3-subtype, which severely limits the development of fl3-AR investigations. Using a polyethylene glycol (PEG) chain to conjugate the Py-5 fluorophore with mirabegron, we present here a highly selective fluorescent ligand, H2, for fl3-AR. It was established by the radioligand and NanoLuc-based bioluminescence resonance energy transfer (NanoBRET) binding experiments that molecule H2 has a substantially higher affinity for fl3-AR than the other two subtypes (1/3, 45-fold; 2/3, 16-fold). More crucially, when molecule H2 was incubated with fl3-AR, the turn-on fluorescent signals could be quickly released. The subsequent investigations, which included cell imaging, tissue imaging, and flow-cytometry analysis, proved that molecule H2 may make it possible to quickly and accurately fluorescently identify fl3-AR at different levels. We offer a prospective fluorescent turn-on ligand with exceptional selectivity for fl3-AR as a result of our combined efforts.