TY - JOUR T1 - GPR139, an Orphan Receptor Highly Enriched in the Habenula and Septum, is Activated by the Essential Amino Acids L-Tryptophan and L-Phenylalanine JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.115.100412 SP - mol.115.100412 AU - Changlu Liu AU - Pascal Bonaventure AU - Grace Lee AU - Diane Nepomuceno AU - Chester Kuei AU - Jiejun Wu AU - Qingqin Li AU - Victory Joseph AU - Steven Sutton AU - William Eckert AU - Xiang Yao AU - Lynn Yieh AU - Curt Dvorak AU - Nicholas Carruthers AU - Heather Coate AU - Sujin Yun AU - Christine Dugovic AU - Anthony Harrington AU - Timothy Lovenberg Y1 - 2015/01/01 UR - http://molpharm.aspetjournals.org/content/early/2015/09/21/mol.115.100412.abstract N2 - GPR139 is an orphan G-protein coupled receptor expressed in the central nervous system. To identify its physiological ligand, we measured GPR139 receptor activity from recombinant cells following treatment with amino acids, orphan ligands, serum and tissue extracts. GPR139 activity was measured using guanosine 5'-O-(3-[35S]thio)-triphosphate binding, calcium mobilization and extracellular signal-regulated kinases phosphorylation assays. The amino acids, L-tryptophan (L-Trp) and L-phenylalanine (L-Phe) were found to activate GPR139, with EC50 values in the 30-300 microM range, consistent with the physiological concentrations of L-Trp and L-Phe in tissues. Chromatography of rat brain, rat serum, and human serum extracts revealed two peaks of GPR139 activity which corresponded to the elution peaks of L-Trp and L-Phe. With the purpose of identifying novel tools to study GPR139 function, a high throughput screening campaign led to the identification of a selective small molecule agonist [JNJ-63533054, (S)-3-chloro-N-(2-oxo-2-((1-phenylethyl)amino)ethyl) benzamide]. The tritium-labelled JNJ-63533054 bound to cell membranes expressing GPR139 and could be specifically displaced by L-Trp and L-Phe. Sequence alignment revealed that GPR139 is highly conserved across species, and RNA sequencing studies of rat and human tissues indicated its exclusive expression in the brain and pituitary gland. Immunohistochemical analysis showed specific expression of the receptor in circumventricular regions of the habenula and septum in mice. Together, these findings suggest that L-Trp and L-Phe are candidate physiological ligands for GPR139, and we hypothesize that this receptor may act as a sensor to detect dynamic changes of L-Trp and L-Phe in the brain. ER -