# The pathway-independent positive allosteric modulator C1 allows for the identification of active Y4 receptor relevant positions

## TL;DR

A new compound called C1 enhances signaling of the Y4 receptor, helping identify key positions important for its active state.

## Contribution

C1 is a novel pathway-independent positive allosteric modulator that enhances Y4 receptor signaling and identifies active receptor positions.

## Key findings

- C1 enhances Y4R G-protein signaling, ligand binding, and arrestin-3 recruitment.
- C1 shows high selectivity for Y4R and potentiates signaling even with low-affinity agonists.
- Hot-spot residues at Y4R were identified using chimera and computational docking.

## Abstract

The neuropeptide Y4 receptor (Y4R) and its endogenous ligand pancreatic polypeptide (PP) are primarily involved in the regulation of satiety and energy balance and present relevant pharmacological targets. We characterized the novel Y4R positive allosteric modulator C1 that enhances Y4R G-protein signaling, ligand binding, and arrestin-3 recruitment to Y4R. Comparison with a close analog revealed the structural importance of an ethyl acetate moiety for Y4R affinity and PAM activity at the G-protein pathway. C1 shows a high selectivity for the Y4R, while signaling of the related subtypes Y1R, Y2R, and Y5R is not affected. Y4R G-protein signaling is even potentiated by the low-affinity agonists neuropeptide Y and peptide YY. Binding affinity of the endogenous ligands to Y4R is enhanced by C1, indicating a stabilization of the ligand-bound Y4R conformation. Using Y4R/Y1R chimera, important Y4R domains for C1 activity were identified. Single point mutagenesis and computational docking pinpointed hot-spot residues at Y4R important for stabilizing the active ligand-bound conformation.

The online version contains supplementary material available at 10.1007/s00018-025-06019-7.