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

The vasopressin type 2 receptor (V(2)R) is an essential GPCR in renal regulation of water homeostasis. Upon stimulation, the V(2)R 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 V(2)R does not terminate Gα(s) activation, and thus, Gα(s)-mediated signaling is sustained while the receptor is internalized. Here, we demonstrate that this V(2)R 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 implies that β-arrestins potentiate Gα(s)/Gα(q/11) activation at endosomes rather than terminating their signaling. Surprisingly, we found that the V(2)R 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.