Discovery of Environment-Sensitive Fluorescent Agonists for α-Adrenergic Receptors.

A series of novel fluorescent agonists were well developed herein with turn-on switch for α-adrenergic receptors (α-ARs) by conjugating the environment-sensitive fluorophore 4-chloro-7-nitrobenzoxadiazole with phenylephrine. Overall, these probes exhibited efficient binding and apparent fluorescence intensity changes (up to 10-fold) upon binding with α-ARs. Moreover, these probes have been successfully applied for selectively imaging α-ARs in the living cells. The dynamic process of α-ARs internalization was traced successfully with these newly designed fluorescent agonists. Fluorescence polarization assay demonstrated specific interactions between these probes and α-ARs. With these new probes, a bioluminescence resonance energy transfer binding assay has been well established and applied to the high-throughput screening of unlabeled α-ARs agonist and antagonist. It is expected that these environment-sensitive fluorescent turn-on agonists may provide useful new tools in studying pharmacology and physiology of α-ARs during drug discovery.