The Current Status of Drug Discovery for the Oxytocin Receptor

Structures of the arginine-vasopressin and oxytocin receptor signaling complexes

Arginine-vasopressin (AVP) and oxytocin (OT) are neurohypophysial hormones which share a high sequence and structure homology. These are two cyclic C-terminally amidated nonapeptides with different residues at position 3 and 8. In mammals, AVP and OT exert their multiple biological functions through a specific G protein-coupled receptor family: four receptors are identified, the V1a, V1b, V2 receptors (V1aR, V1bR and V2R) and the OT receptor (OTR). The chemical structure of AVP and OT was elucidated in the early 1950s. Thanks to X-ray crystallography and cryo-electron microscopy, it took however 70 additional years to determine the three-dimensional structures of the OTR and the V2R in complex with their natural agonist ligands and with different signaling partners, G proteins and β-arrestins. Today, the comparison of the different AVP/OT receptor structures gives structural insights into their orthosteric ligand binding pocket, their molecular mechanisms of activation, and their interfaces with canonical Gs, Gq and β-arrestin proteins. It also paves the way to future rational drug design and therapeutic compound development. Indeed, agonist, antagonist, biased agonist, or pharmacological chaperone analogues of AVP and OT are promising candidates to regulate different physiological functions and treat several pathologies.

Structural basis for the activation and ligand recognition of the human oxytocin receptor

The small cyclic neuropeptide hormone oxytocin (OT) and its cognate receptor play a central role in the regulation of social behaviour and sexual reproduction. Here we report the single-particle cryo-electron microscopy structure of the active oxytocin receptor (OTR) in complex with its cognate ligand oxytocin. Our structure provides high-resolution insights into the OT binding mode, the OTR activation mechanism as well as the subtype specificity within the oxytocin/vasopressin receptor family.

Here, Waltenspühl et al. report the cryo-EM structure of active human oxytocin receptor in complex with oxytocin and with a heterotrimeric G protein, providing insights into this hormone system critically involved in the regulation of social behaviour and reproduction.