Orphan receptor GPR139 hides a Gs pathway that overrides its inhibitory Gi/o signalling
- GPR139, an orphan GPCR linked to psychiatric disease, was profiled with BRET coupling assays, G protein knockout cell lines, and second messenger and arrestin readouts.
- It engages Gi/o, Gq/11 and G12/13 directly, yet raises cAMP through a Gs route that standard coupling assays missed.
- That Gs effect normally prevails; Gi/o-mediated cAMP suppression only emerges once Gs is removed.
- Chemically distinct agonists produced different signalling fingerprints, pointing to ligand-dependent bias.
💡 Points Based on the abstract
If Gs wins in native cells, then every Gi/o-based readout people have used to screen GPR139 agonists may have been misleading. Before anyone calls it biased agonism, I'd want the same compounds run in neurons or tissue that actually express the receptor, where Gs stoichiometry differs from overexpressing HEK cells. Until then, a worthwhile next study is a cAMP panel across relevant brain regions.