Membrane-tethered peptides derived from intracellular loops 2 and 3 of the urotensin II receptor act as allosteric biased ligands

Over the last decade, the urotensinergic system has garnered significant attention as a promising new target for the treatment of various cardiovascular diseases and also cancer. Significant investment toward the development of clinically relevant UT ligands for therapeutic intervention has been made but have met little to no success to date. The UT system, which has yet to be effectively targeted, therefore remains to be therapeutically exploited. The discovery of allosteric sites that allow modulation of receptor activity will increase the searchable chemical space against a disease-relevant target. Pepducins and other lipidated peptides have been used as both mechanistic probes and potential therapeutics. Therefore, pepducins derived from the human urotensin II receptor might represent unique tools to generate signaling bias and study UT signaling networks. Two hUT-derived pepducins, derived from the second and the third intracellular loop of UT, respectively, have been synthesized and pharmacologically characterized. Our results demonstrated that hUT-Pep2 and [Trp1, Leu2]hUT-Pep3 acted as biased ago-allosteric modulators, triggered ERK1/2 phosphorylation and to a lesser extent, IP1 production, stimulated cell proliferation yet were devoid of contractile activity. Interestingly, both hUT-derived pepducins were able to modulate hUII- and URP-mediated contraction albeit to different extents. These new derivatives represent unique tools to reveal the intricacies of hUT signaling and also a novel avenue to design allosteric ligands selectively targeting UT signaling that could prove to be useful for the treatment of hUT-associated diseases.