Differential functional selectivity and downstream signaling bias of ghrelin receptor antagonists and inverse agonists

Identifier:  imarina:6389541

Handle: https://hdl.handle.net/20.500.11797/imarina6389541

Authors:  Ramirez, Valerie T; van Oeffelen, Wesley E P A; Torres-Fuentes, Cristina; Chruscicka, Barbara; Druelle, Clementine; Golubeva, Anna V; van de Wouw, Marcel; Dinan, Timothy G; Cryan, John F; Schellekens, Harriet

Abstract:
© FASEB. The ghrelin receptor [growth hormone secretagogue receptor (GHSR)-1a] represents a promising pharmacologic target for the treatment of metabolic disorders, including obesity and cachexia, via central appetite modulation. The GHSR-1a has a complex pharmacology, highlighted by G-protein-dependent and-independent downstream signaling pathways and high basal constitutive activity. The functional selectivity and signaling biasof many GHSR-1a-specific ligands has not been fully characterized. In this study, we investigated the pharmacologic properties of ghrelin, MK-0677, L692,585, and [D-Lys3]-growth hormone-releasing peptide-6 (Dlys), JMV2959, and [D-Arg(1),D-Phe(5),D-Trp(7, 9),Leu(11)]-substance P (SP-analog). We investigated their effect on basal GHSR-1a constitutive signaling, ligand-directed downstream GHSR-1a signaling, functional selectivity, and signaling bias. Dlys behaved as a partial antagonist with a strong bias toward GHSR-1a-b-arrestin signaling, whereas JMV2959 acted as a full unbiased GHSR-1a antagonist. Moreover, the SP-analog behaved as an inverse agonist increasing G-protein-dependent signaling, but only at high concentrations, whereas, at low concentrations, the SP-analog attenuated b-arrestin-dependent signaling. Considering the limited success in the clinical development of GHSR-1a-targeted drugs so far, these findings provide a novel insight into the pharmacologic characteristics of GHSR-1a ligands and their signaling bias, which has important implications in the design of novel, more selective GHSR-1a ligands with predictable functional outcome and selectivity for preclinical and clinical drug development.