β-Arrestin-dependent and -independent endosomal G protein activation by the vasopressin type 2 receptor

The vasopressin type 2 receptor (V₂R) is an essential G protein-coupled receptor (GPCR) in renal regulation of water homeostasis. Upon stimulation, the V₂R activates Gα_s and Gα_q/11, which is followed by robust recruitment of β-arrestins and receptor internalization into endosomes. Unlike canonical GPCR signaling, the β-arrestin association with the V₂R does not terminate Gα_s activation, and thus, Gα_s-mediated signaling is sustained while the receptor is internalized. Here, we demonstrate that this V₂R ability to co-interact with G protein/β-arrestin and promote endosomal G protein signaling is not restricted to Gα_s, but also involves Gα_q/11. Furthermore, our data imply that β-arrestins potentiate Gα_s/Gα_q/11 activation at endosomes rather than terminating their signaling. Surprisingly, we found that the V₂R internalizes and promote endosomal G protein activation independent of β-arrestins to a minor degree. These new observations challenge the current model of endosomal GPCR signaling and suggest that this event can occur in both β-arrestin-dependent and -independent manners.