Signalling, trafficking and glucoregulatory properties of glucagon-like peptide-1 receptor agonists exendin-4 and lixisenatide

Br J Pharmacol. 2020 Sep;177(17):3905-3923. doi: 10.1111/bph.15134. Epub 2020 Jun 19.


Background and purpose: Amino acid substitutions at the N-termini of glucagon-like peptide-1 (GLP-1) receptor agonist peptides result in distinct patterns of intracellular signalling, sub-cellular trafficking and efficacy in vivo. Here, we to determine whether sequence differences at the ligand C-termini of clinically approved GLP-1 receptor agonists exendin-4 and lixisenatide lead to similar phenomena.

Experimental approach: Exendin-4, lixisenatide and N-terminally substituted analogues with biased signalling characteristics were compared across a range of in vitro trafficking and signalling assays in different cell types. Fluorescent ligands and new time-resolved FRET approaches were developed to study agonist behaviours at the cellular and sub-cellular level. Anti-hyperglycaemic and anorectic effects of each parent ligand and their biased derivatives were assessed in mice.

Key results: Lixisenatide and exendin-4 showed equal binding affinity, but lixisenatide was fivefold less potent for cAMP signalling. Both peptides induced extensive GLP-1 receptor clustering in the plasma membrane and were rapidly endocytosed, but the GLP-1 receptor recycled more slowly to the cell surface after lixisenatide treatment. These combined deficits resulted in reduced maximal sustained insulin secretion and reduced anti-hyperglycaemic and anorectic effects in mice with lixisenatide. N-terminal substitution of His1 by Phe1 to both ligands had favourable effects on their pharmacology, resulting in improved insulin release and lowering of blood glucose.

Conclusion and implications: Changes to the C-terminus of exendin-4 affect signalling potency and GLP-1 receptor trafficking via mechanisms unrelated to GLP-1 receptor occupancy. These differences were associated with changes in their ability to control blood glucose and therefore may be therapeutically relevant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Exenatide / pharmacology
  • Glucagon-Like Peptide-1 Receptor*
  • Hypoglycemic Agents / pharmacology
  • Insulin
  • Mice
  • Peptides* / pharmacology


  • Glucagon-Like Peptide-1 Receptor
  • Hypoglycemic Agents
  • Insulin
  • Peptides
  • lixisenatide
  • Exenatide