V_1b vasopressin receptor trafficking and signaling: Role of arrestins, G proteins and Src kinase

The signaling pathway of G protein-coupled receptors is strongly linked to their trafficking profile. Little is known about the molecular mechanisms involved in the vasopressin receptor V_1b subtype (V_1bR) trafficking and its impact on receptor signaling and regulation. For this purpose, we investigated the role of β-arrestins in receptor desensitization, internalization and recycling and attempted to dissect the V_1bR-mediated MAP kinase pathway. Using MEF cells Knocked-out for β-arrestins 1 and 2, we demonstrated that both β-arrestins 1 and 2 play a fundamental role in internalization and recycling of V_1bR with a rapid and transient V_1bR-β-arrestin interaction in contrast to a slow and long-lasting β-arrestin recruitment of the V₂ vasopressin receptor subtype (V₂R). Using V_1bR-V₂R chimeras and V_1bR C-terminus truncations, we demonstrated the critical role of the V_1bR C-terminus in its interaction with β-arrestins thereby regulating the receptor internalization and recycling kinetics in a phosphorylation-independent manner. In parallel, V_1bR MAP kinase activation was dependent on arrestins and Src-kinase but independent on G proteins. Interestingly, Src interacted with hV_1bR at basal state and dissociated when receptor internalization occurred. Altogether, our data describe for the first time the trafficking profile and MAP kinase pathway of V_1bR involving both arrestins and Src kinase family.