G Protein: β-Arrestin Bias Confers Differential Regulation of Gα_q Signaling by GPR17 Antagonists

Therapies enhancing remyelination offer the exciting prospect of disease-modifying treatments across a number of poorly treated neurological disorders. The class A orphan GPCR, GPR17, is one of the most studied receptors in remyelination; and antagonists of GPR17 have attracted significant attention as potential pro-myelinating medicines. Despite this, the signaling pathways linking GPR17 to remyelination and the molecular mechanisms of action of GPR17 antagonists are not well-defined. In the present study, we characterized GPR17 signaling and inhibition by three chemically distinct GPR17 antagonists: pranlukast, HAMI-3379, and a patent literature antagonist, RWT9996. In HEK293 cells recombinantly expressing GPR17- and BRET-based biosensors, pranlukast preferentially inhibited G protein activation over β-arrestin-2 recruitment, whereas HAMI3379 and RWT9996 equally inhibited all signal transduction tested. Follow-up studies using pharmacological inhibitors and GPR17 antagonists in Oli-neu cells, an immortalized mouse oligodendrocyte precursor cell (OPC) line with endogenous GPR17 expression, corroborated the G protein and β-arrestin coupling profile observed in recombinant cells. Specifically, the generated bias profile suggests that β-arrestin potentiates Gα_q signaling from GPR17, conferring differential regulation of Gα_q signaling by biased GPR17 antagonists. These findings highlight an unappreciated potential for biased signaling in the pharmacology of GPR17 ligands. We anticipate that these insights will help to inform the translation of GPR17-targeted therapies and improve our understanding of GPR17-mediated signaling pathways in governing myelination.