%0 Journal Article %A Chenli Ye %A Zhenghong Zhang %A Zhilong Wang %A Qiuhong Hua %A Ru Zhang %A Xin Xie %T Identification of a Novel Small-Molecule Agonist for Human G Protein–Coupled Receptor 3 %D 2014 %R 10.1124/jpet.114.213082 %J Journal of Pharmacology and Experimental Therapeutics %P 437-443 %V 349 %N 3 %X G protein–coupled receptor 3 (GPR3) is an orphan G protein–coupled receptor (GPCR) predominantly expressed in mammalian brain and oocytes. GPR3 plays important roles in these two organs and is known as a Gαs-coupled receptor–activated constitutively in cells. However, the signal transduction pathway and pharmacological function of GPR3 remain unclear because of the lack of a specific ligand. By use of a human embryonic kidney 293 cell line stably expressing FLAG-GPR3-green fluorescent protein, a chemical screening for GPR3 ligands was performed using homogeneous time-resolved fluorescence cAMP assay. Diphenyleneiodonium chloride (DPI) was identified as a novel agonist of GPR3 with weak or no cross-reactivity with other GPCRs. DPI was further characterized to activate several GPR3-mediated signal transduction pathways, including Ca2+ mobilization, cAMP accumulation, membrane recruitment of β-arrestin2, and receptor desensitization. Parallel studies revealed that the activity of DPI is much more pronounced than sphingosine 1-phosphate, a previously reported GPR3 agonist. Our study identified a novel and specific agonist of GPR3, which provides a useful tool for further study of this orphan GPCR. %U https://jpet.aspetjournals.org/content/jpet/349/3/437.full.pdf