Functional Expression of Single-Chain Heterodimeric G-Protein-Coupled Receptors for Adenosine and Dopamine

Abstract

The direct homo- and heteromeric association between G-protein-coupled receptors (GPCRs), adenosine A_2A receptor (A_2AR) and dopamine D₂ receptor (D₂R), occurs although little is known about the selectivity of their formation (A_2AR/A_2AR vs. A_2AR/D₂R). In order to stimulate the heteromerization of A_2AR and D₂R, we have designed a single-polypeptide-chain heterodimeric A_2AR/D₂R complex by fusing the C-terminus of the A_2AR via transmembrane (TM) of a type II TM protein with the N-terminus of D₂R in tandem. This was successfully expressed on the cell surface as a full-length protein with specific binding to the respective ligands and functional coupling to G-proteins comparable to wild-type receptors, suggesting the possible creation of physiologically relevant heteromeric A_2AR/D₂R. This expression system would be useful to exclusively clarify the properties of heteromeric GPCRs irrespective of homomeric receptors.