posted on 2021-01-19, 18:36authored byWijnand
J. C. van der Velden, Florent X. Smit, Charlotte B. Christiansen, Thor C. Møller, Gertrud M. Hjortø, Olav Larsen, Sine P. Schiellerup, Hans Bräuner-Osborne, Jens J. Holst, Bolette Hartmann, Thomas M. Frimurer, Mette M. Rosenkilde
Biased ligands that selectively confer
activity in one pathway
over another are pharmacologically important because biased signaling
may reduce on-target side effects and improve drug efficacy. Here,
we describe an N-terminal modification in the incretin hormone glucagon-like
peptide (GLP-1) that alters the signaling capabilities of the GLP-1
receptor (GLP-1R) by making it G protein biased over internalization
but was originally designed to confer DPP-4 resistance and thereby
prolong the half-life of GLP-1. Despite similar binding affinity,
cAMP production, and calcium mobilization, substitution of a single
amino acid (Ala8 to Val8) in the N-terminus of GLP-1(7–36)NH2 (GLP-1 Val8) severely impaired its ability to internalize
GLP-1R compared to endogenous GLP-1. In-depth binding kinetics analyses
revealed shorter residence time for GLP-1 Val8 as well as a slower
observed association rate. Molecular dynamics (MD) displayed weaker
and less interactions of GLP-1 Val8 with GLP-1R, as well as distinct
conformational changes in the receptor compared to GLP-1. In vitro validation of the MD, by receptor alanine substitutions,
confirmed stronger impairments of GLP-1 Val8-mediated signaling compared
to GLP-1. In a perfused rat pancreas, acute stimulation with GLP-1
Val8 resulted in a lower insulin and somatostatin secretion compared
to GLP-1. Our study illustrates that profound differences in molecular
pharmacological properties, which are essential for the therapeutic
targeting of the GLP-1 system, can be induced by subtle changes in
the N-terminus of GLP-1. This information could facilitate the development
of optimized GLP-1R agonists.