A β-peptide agonist of the GLP-1 receptor, a class B GPCR

Abstract

Previous work has shown that certain β(3)-peptides can effectively mimic the side chain display of an α-helix and inhibit interactions between proteins, both in vitro and in cultured cells. Here we describe a β(3)-peptide analog of GLP-1, CC-3(Act), that interacts with the GLP-1R extracellular domain (nGLP-1R) in vitro in a manner that competes with exendin-4 and induces GLP-1R-dependent cAMP signaling in cultured CHO-K1 cells expressing GLP-1R.

Figure 1

(A) View of exendin-4 (purple) in complex with nGLP-1R (grey) (PDB 3C5T) illustrating relative orientation of the incretin α-helix and the Sushi fold of the receptor extracellular domain. (B) Sequence of exendin-4 aligned with two heptad repeats. (C) View of GLP-1 looking down the helix axis to illustrate side chain arrangement at the ligand-receptor interaction face. (D) Cartoon illustrating the stereochemical relationships between the three 14-helix faces. (E) Helical net and sequences of β-peptides evaluated herein.

Figure 2

Fluorescence polarization (FP) competition analysis of interactions between nGLP-1R and either peptides (GLP-1 and GLP1_5-37) or β³-peptides. Plots illustrate the change in the polarization of 5 nM exendin-4^Flu as a function of the concentration of the ligand indicated; [nGLP-1R] = 125 nM.

Figure 3

Effect of β-peptides and ligands on cAMP production in cells expressing class B1 GPCRs. (A-D) Effect of various β-peptides and exendin-4 on cAMP accumulation in GLP-1R+ CHO-K1 cells. (E,F) cAMP accumulation in GIPR+, PAC1+, GCCR+, and VPAC+CHO-K1 cells upon treatment with the cognate ligand, CC-3^Act or CC-11^Act.