Species-specific differences in agonistic activity of ago-allosteric modulators toward glucagon-like peptide 2 receptor

Glucagon-like peptide 2 (GLP-2) is an intestinotropic peptide that binds to GLP-2 receptor (GLP- 2R), a class-B G protein-coupled receptor (GPCR) coupled with Gα(s). Few small-molecule agonists had been reported for class-B GPCRs, but we recently reported the first scaffold compounds of ago-allosteric modulators for human GLP-2R. Methyl 2-{[(2Z)-2-(2,5-dichlorothiophen- 3-yl)-2-(hydroxyimino)ethyl]sulfanyl}benzoate (compound 1) and its de-esterified derivative (compound 2) induced placental alkaline phosphatase (PLAP) activity in HEK293 cells overexpressing human GLP-2R and PLAP driven by cAMP response element. In this study, we observed that rat, Syrian hamster, and dog GLP-2Rs also responded to compounds 1 and 2 in the same reporter system. However, no agonistic activity of the compounds toward mouse GLP-2R was detected. Mutagenesis studies showed that mutant human GLP-2Rs with Pro392Leu substitution of mouse GLP-2R for human GLP-2R amino acid residues nullified the PLAP activity of compound 2, although these mutant receptors responded to GLP-2. This finding suggests that the Pro392 residue of human GLP-2R is essential for the agonistic activity of compound 2.