P2Y13 as promising new drug target: assay development and ligand investigation

The P2Y13 receptor is a G protein-coupled receptor belonging to “P2Y12-like” subfamily within the δ-group of Class A GPCR. The endogenous ligand is ADP. P2Y13 is one most recently discovered metabotropic P2Y receptors, so it is not well characterized yet but is a promising drug target. It is mainly expressed in the brain, liver and pancreas fulfilling key roles in the regulation of cholesterol and glucose metabolism, bone homeostasis, pain transmission and neuroprotection. P2Y13 is highly similar to P2Y12, sharing some pharmacology aspects and the presence of two ligand binding pockets in the seven-transmembrane domain. β-arrestin2 recruitment assays were employed and optimized to investigate the P2Y13 wild-type response, which resulted to be small and broad, upon ADP and 2-MeS-ADP (a potent agonist) activation. The same agonists activated with more efficacy and less potency the P2Y13 natural variant T179M. The lower efficacy of P2Y13 can be explained by its preference for β-arrestin1 instead of β-arrestin-2, assessed through ebBRET method upon stimulation with the two agonists. The P2Y13 receptor is versatile in its signalling, extending beyond the canonical signalling of a Gαi/o-coupled receptor thus coupling to Gαq, triggering mitogen-activated protein kinases (MAPKs) and activating the phosphatidylinositol 3-kinase/Akt/glycogen synthase kinase 3 pathway. Deeper insights into P2Y13 Gαi/o proteins interaction and signalling were gained by using the TRUPATH platform, resulting in possible preferences for the GαoA and GαoB proteins. Future studies, especially for the development of selective ligands targeting P2Y13 and to further understand its activation and downstream signaling are necessary in order to better understand its function.