Glucagon-like peptide-1 mimotopes screened from an Fv-antibody library

Abstract

Glucagon-like peptide-1 receptor (GLP-1R) agonists treat type 2 diabetes and obesity by promoting insulin secretion and suppressing glucagon release. In this study, GLP-1 mimotopes with GLP-1R agonist activity were screened from the Fv-antibody library. The Fv-antibodies represented the hypervariable region of heavy-chain IgG, which included three CDRs and four FRs, and the library was produced by randomizing the CDR3 region with 11 amino acids through site-directed mutagenesis. The GLP-1 mimotopes with GLP-1R agonist activity were screened using monoclonal anti-GLP-1 antibodies and were synthesized into peptides and expressed as Fv-antibodies co-expressed with GFP. The binding affinity of GLP-1 mimotopes was analyzed using a surface plasmon resonance biosensor, and the activity of the GLP-1 mimotopes (expressed Fv-antibodies and synthesized peptides) was analyzed by measuring cyclic adenosine monophosphate (cAMP) production and hormone secretion in pancreatic α- and β-cells. The molecular docking simulations revealed that GLP-1 mimotopes interacted with GLP-1R by targeting key residues known to bind GLP-1, supporting their potential as functional receptor agonists. The effect on fatty acid accumulation was analyzed using hepatocyte cell lines (HepG2 and Huh7), and transcriptomic changes were analyzed by RNA sequencing. In addition, GLP-1R downstream signaling in β-cells was evaluated by western blot analysis of AKT and ERK1/2 phosphorylation. This approach offers a novel strategy to generate new GLP-1R agonists and expand molecular diversity for GLP-1R-targeted therapeutic design.