Biased signaling regulates the pleiotropic effects of the urotensin II receptor to modulate its cellular behaviors

Biased agonism by G-protein-coupled receptor ligands has opened up strategies for targeted physiological or therapeutic actions. We hypothesized that urotensin II (UII)-derived peptides displayed unexpected physiological effects because of such biased signaling on the UII human urotensin (hUT) receptor. We determined the coupling to G proteins and beta-arrestins of the UII-activated hUT receptor expressed in HEK293 using bioluminescence resonance energy transfer (BRET) biosensors, as well as the production of IP1-3 and cAMP using homogenous time-resolved Forster resonance energy transfer (FRET) (HTRF)-based assays. The activated receptor coupled to G(i1), G(oA), G(q), and G(13), excluding G(s), and recruited beta-arrestins 1 and 2. Integration of these pathways led to a 2-phase kinetic phosphorylation of ERK1/2 kinases. The tested peptides induced three different profiles: UII, urotensin-related peptide (URP), and UII4-11 displayed the full profile; [Orn(8)] UII and [Orn(5)] URP activated G proteins, although with pEC(50)s 5-10 x higher, and did not or barely recruited beta-arrestin; urantide also failed to recruit beta-arrestin but displayed a reversed rank order for G(i) and G(q) vs. G(o) pEC(50)s (-8.79 +/- 0.20, -8.43 +/- 0.21, and -7.86 +/- 0.36, respectively, for urantide, -7.87 +/- 0.10, -7.23 -0.27, and -8.55 +/- 0.19, respectively, for [Orn5] URP) and was a partial agonist of all G-protein pathways. Interestingly, the peptides differently modulated cell survival but similarly induced cell migration and adhesion. Thus, we demonstrate biased signaling between beta-arrestin and G proteins, and between G-protein subtypes, which dictates the receptor's cellular responses.-Brule, C., Perzo, N., Joubert, J.-E., Sainsily, X., Leduc, R., Castel, H., Prezeau, L. Biased signaling regulates the pleiotropic effects of the urotensin II receptor to modulate its cellular behaviors.