Antagonism of dopamine D2 receptor/β-arrestin 2 interaction is a common property of clinically effective antipsychotics

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Abstract
Since the unexpected discovery of the antipsychotic activity of chlorpromazine, a variety of therapeutic agents have been developed for the treatment of schizophrenia. Despite differences in their activities at various neurotransmitter systems, all clinically effective antipsychotics share the ability to interact with D2 class dopamine receptors (D2R). D2R mediate their physiological effects via both G protein-dependent and independent (beta-arrestin 2-dependent) signaling, but the role of these D2R-mecliated signaling events in the actions of antipsychotics remains unclear. We demonstrate here that while different classes of antipsychotics have complex pharmacological profiles at G protein-dependent D2R long isoform (D2(L)R) signaling, they share the common property of antagonizing dopamine-mediated interaction of D2(L)R with beta-arrestin 2. Using two cellular assays based on a bioluminescence resonance energy transfer (BRET) approach, we demonstrate that a series of antipsychotics including haloperidol, clozapine, aripiprazole, chlorpromazine, quetiapine, olanzapine, rispericlone, and ziprasidone all potently antagonize the beta-arrestin 2 recruitment to D2(L)R induced by quinpirole. However, these antipsychotics have various effects on D2(L)R mediated G(i/o) protein activation ranging from inverse to partial agonists and antagonists with highly variable efficacies and potencies at quinpirole-induced cAMP inhibition. These results suggest that the different classes of clinically effective antipsychotics share a common molecular mechanism involving inhibition of D2(L)R/beta-arrestin 2 mediated signaling. Thus, selective targeting of D2(L)R/beta-arrestin 2 interaction and related signaling pathways may provide new opportunities for antipsychotic development.