Nanomolar range of FAM237B can activate receptor GPR83

The orphan G protein-coupled receptor 83 (GPR83) is implicated in the regulation of energy metabolism and certain anxiety-related behaviors. Our recent study confirmed that family with sequence similarity 237 member A (FAM237A), also known as neurosecretory protein GL (NPGL), is an efficient agonist for GPR83, but did not support the proprotein convertase subtilisin/kexin type 1 inhibitor (PCSK1N, also known as proSAAS)-derived peptide PEN and the procholecystokinin-derived peptide proCCK56-63 as ligands of this receptor. FAM237B (also known as NPGM) is a paralog of FAM237A that was previously reported as a weak agonist for GPR83 with approximately 100-fold lower activity in an inositol 1-phosphate accumulation assay. In the present study, we prepared mature human FAM237B via an intein-fusion approach and measured its activity towards human GPR83 via a NanoLuc Binary Technology (NanoBiT)-based ligand□receptor binding assay and a NanoBiT-based β-arrestin recruitment assay. Mature FAM237B displayed moderately lower activity than its paralog FAM237A in these binding and activation assays, but could cause a significant activation effect at the nanomolar range (1□10 nM). Thus, FAM237B appears to be another endogenous agonist for receptor GPR83.