Impact of substitution registry on receptor-activation profiles of backbone-modified glucagon-like peptide-1 analogues

Abstract

Family B G protein-coupled receptors play important physiological roles and possess large extracellular domains (ECD) that aid in binding the long polypeptide hormones that are their natural agonists. We have previously shown that agonist analogues in which subsets of native α-amino acid residues are replaced with β-amino acid residues can retain activity while avoiding proteolytic degradation. This study focuses on eight new α/β analogues of glucagon-like peptide 1 (GLP-1) that each contain five α-to-β replacements in the C-terminal half of the peptide. This portion of GLP-1 is known to adopt an α-helical conformation and contact the ECD. All four registries ofαααβ backbone pattern were evaluated; previous work has shown that the αααβ patter supports adoption of an α-helix-like conformation. Two α-to-β replacement formats were employed, one involving β ³ homologues of the native residues replaced and the other involving acyclic β residue. GLP-1R response was characterized in terms of stimulation of cAMP production and β-arrestin recruitment. Some of the backbone-modified GLP-1 analogues display biased agonism of the GLP-1R. This study helps to establish the scope of the α→β backbone modification strategy.

Graphical Abstract

Family B G protein-coupled receptors are activated by long polypeptide hormones, control an array of important physiological processes, and can exhibit pleiotropic signaling behavior. Here, we evaluated the effects of backbone modifications in the C-terminal region of Glucagon-like peptide-1; the region that interacts with the receptor’s extracellular domain. We observed varying degrees of activity and some agonists with functional selectivity.