BRET Approaches to Characterize Dopamine and TAAR1 Receptor Pharmacology and Signaling

It is evident that G protein-coupled receptors (GPCRs) such as D2 dopamine receptor and functionally related Trace Amine Associated Receptor 1 (TAAR1) can engage both in G protein-dependent (e.g., cAMP-mediated) and -independent β-arrestin-mediated signaling modalities. Both of these signaling events can be monitored in real-time and in live cells by using new biosensors based on a Bioluminescence Resonance Energy Transfer (BRET) approach. Here we discuss the practical applications of BRET to analyze dynamics of cAMP modulation via an EPAC biosensor as well as recruitment of β-arrestin2 to the D2 dopamine receptor. Combination of these approaches allows for a comparison of activity of pharmacological compounds on these signaling modalities as demonstrated for various antipsychotics as regard to D2 dopamine receptor. Furthermore, analysis of cAMP concentrations in cells expressing TAAR1 provides a simple high-throughput screening method to identify new ligands for this receptor. These BRET approaches could be applied for the characterization of pharmacology and signaling of variety of other GPCRs.