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 G protein-coupled receptor (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 imply 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.