Fig. P1.

(A) Supernatant transfer assay. The supernatant transfer assay used to dissect the molecular events upstream and downstream of IGFR transactivation. V2R-null acceptor cells were stimulated with the transferred supernatant of AVP-stimulated, V2R-expressing donor cells that were or were not pretreated with inhibitors, dominant negative mutants, or siRNAs. (B) V2R-regulated signaling. V2R-regulated β-arrestin–dependent activities where AVP binding to V2R elicits the engagement of distinct β-arrestin (βarr) pools involved in opposed signaling events. AVP stimulation of V2R induces the Src-dependent metalloproteinase-mediated (MP) shedding of an IGFR transactivating factor, promoting β-arrestin recruitment to IGFR and the ensuing ERK1/2 activity. However, recruitment of β-arrestins to the activated V2R leads to signal arrest through desensitization of the Gs-adenylate cyclase (AC) –PKA signaling pathway.