G protein-coupled receptor 50 is a protein which in humans is encoded by the GPR50 gene.
GPR50 is a member of the G protein-coupled receptor family of integral membrane proteins and is most closely related to the melatonin receptor. GPR50 is able to heterodimerize with both the MT<sub>1</sub> and MT<sub>2</sub> melatonin receptor subtypes. While GPR50 has no effect on MT<sub>2</sub> function, GPR50 prevented MT<sub>1</sub> from both binding melatonin and coupling to G proteins. GPR50 is the mammalian ortholog of melatonin receptor Mel1c described in non-mammalian vertebrates.
Certain polymorphisms of the GPR50 gene in females are associated with increased risk of developing bipolar affective disorder, major depressive disorder, and schizophrenia. Other GPR50 gene polymorphism are associated with higher fasting circulating triglyceride levels and lower circulating High-density lipoprotein levels.