Antipsychotic-Like Efficacy of Dopamine D2 Receptor-Biased Ligands is Dependent on Adenosine A2A Receptor Expression

Dopamine D-2 receptor (D2R) activation triggers both G protein- and beta-arrestin-dependent signaling. Biased D2R ligands activating beta-arrestin pathway have been proposed as potential antipsychotics. The ability of D2R to heteromerize with adenosine A(2A) receptor (A(2A)R) has been associated to D2R agonist-induced beta-arrestin recruitment. Accordingly, here we aimed to demonstrate the A(2A)R dependence of D2R/beta-arrestin signaling. By combining bioluminescence resonance energy transfer (BRET) between beta-arrestin-2 tagged with yellow fluorescent protein and bimolecular luminescence complementation (BiLC) of D2R/A(2A)R homomers and heteromers, we demonstrated that the D2R agonists quinpirole and UNC9994 could promote beta-arrestin-2 recruitment only when A(2A)R/D2R heteromers were expressed. Subsequently, the role of A(2A)R in the antipsychotic-like activity of UNC9994 was assessed in wild-type and A(2A)R(-/-) mice administered with phencyclidine (PCP) or amphetamine (AMPH). Interestingly, while UNC9994 reduced hyperlocomotion in wild-type animals treated either with PCP or AMPH, in A(2A)R(-/-) mice, it failed to reduce PCP-induced hyperlocomotion or produced only a moderate reduction of AMPH-mediated hyperlocomotion. Overall, the results presented here reinforce the notion that D2R/A(2A)R heteromerization facilitates D2R beta-arrestin recruitment, and furthermore, reveal a pivotal role for A(2A)R in the antipsychotic-like activity of the beta-arrestin-biased D2R ligand, UNC9994.