Discovery of artificial VIPR2-antagonist peptides possessing receptor- and ligand-selectivity

Highlights: • The first VIPR2-selective artificial antagonist peptides were discovered. • VIpep-3 showed more than 50-fold inhibition-selectivity to VIPR2 in compared to receptor subtypes VIPR1 and PAC1. • VIpep-3 presented about 8.7-fold ligand-selectivity to VIP in compared to another ligand PACAP. Vasoactive intestinal peptide receptor 2 (VIPR2, also known as VPAC2) is a class B G-protein coupled receptor (GPCR) and plays important roles in the physiology of central nervous system (CNS) by interaction with natural ligands; vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP). Because it has been reported that high-expression and/or overactivation of VIPR2 link to schizophrenic symptoms, VIPR2 antagonists could be good drug candidates for schizophrenia therapeutics. In this study, we discovered several artificial peptides that antagonize both human and rodent VIPR2 with selectivities against receptor subtypes VIPR1 (also known as VPAC1) and pituitary adenylate cyclase-activating polypeptide type-1 receptor (PAC1). Of them, the representative 16-mer cyclic peptide VIpep-3 (Ac-CPPYLPRRLCTLLLRS-OH) exhibited strong binding affinity with K_D value of 41 nM to extracellular domain of human VIPR2 in SPR analysis and showed potent antagonist activity with IC₅₀ values of 47 nM (human), 180 nM (mouse), and 44 nM (rat) against VIP–VIPR2 signal in cell-based Ca influx assay. This is not only the first report on artificial VIPR2-selective antagonist peptides but also good example of the effective approach to discover novel antagonist against class B GPCR. Our peptides will contribute to study and development of the novel CNS drugs targeting to VIPR2.