Direct visualization of adenosine A2A and dopamine D2L receptor oligomers in a neuronal cell model

Abstract

Dopamine D2 and adenosine A2A receptors are co‐expressed in GABAergic neurons in the basal ganglia where they antagonistically regulate adenylyl cyclase activity. Interactions between D2 and A2A are thought to play an important role in drug addiction and in the pharmacotherapy of Parkinson's disease. Molecular mechanisms may involve the formation of receptor oligomers signaling to alternative pathways. D2 and A2A have been shown to form homo‐ and heterooligomers both in recombinant cells and in native brain tissues. However, the stoichiometry of these complexes, as well as the regulation or their formation (notably by ligands) remain to be characterized.We have used bimolecular fluorescence complementation (BiFC) for direct visualization of A2A homodimers and A2A ‐ D2 heterodimers in a neuronal cell model. Initial studies revealed that the receptor‐BiFC fusion proteins remained functional. Preliminary experiments using multicolor BiFC indicated that prolonged exposure to D2 antagonist spiperone promotes A2A ‐ D2 dimerization whereas D2 agonist quinpirole treatment upregulates A2A homodimerization. In addition, studies combining BiFC with FRET provided evidence for the formation of higher‐order A2A D2 oligomers.This project was funded by Purdue University and NIMH grant award MH060397 to VJW.