β-Arrestin-2-Dependent Mechanism of GPR52 Signaling in Frontal Cortical Neurons

The orphan Gas-coupled receptor GPRS2 is expressed exclusively in the brain, predominantly in circuitry relating to symptoms of neuropsychiatric and cognitive disorders such as schizophrenia. While GPRS2 agonists have displayed antipsychotic and procognitive efficacy in murine models, there remains limited evidence delineating the molecular mechanisms of these effects. Indeed, previous studies have solely reported canonical cAMP signaling and CREB phosphorylation downstream of GPR52 activation. In the present study, we demonstrated that the synthetic GPRS2 agonist, 3-BTBZ, equipotently induces cAMP accumulation, ERK1/2 phosphorylation, and beta-arrestin-1 and -2 recruitment in transfected HEK293T cells. In cultured frontal cortical neurons, however, 3-BTBZ-induced ERK1/2 phosphorylation was significantly more potent than cAMP signaling, with a more prolonged signaling profile than that in HEK293T cells. Furthermore, knock down of beta-arrestin-2 in frontal cortical neurons abolished 3-BTBZ-induced ERK1/2 phosphorylation, but not cAMP accumulation. These results suggest a beta-arrestin-2-dependent mechanism for GPR52-mediated ERK1/2 signaling, which may link to cognitive function in vivo. Finally, these findings highlight the context-dependence of GPCR signaling in recombinant cells and neurons, offering new insights into translationally relevant GPR52 signaling mechanisms.