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This Article Full Text Full Text (PDF) Supplemental Figures and Tables All Versions of this Article: 297/4/R1009    most recent 90766.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Rihakova, L. Articles by Chemtob, S. PubMed PubMed Citation Articles by Rihakova, L. Articles by Chemtob, S.

Articles

VRQ397 (CRAVKY): a novel noncompetitive V2 receptor antagonist

¹Hôpital Ste Justine, Research Center, Departments of Pediatrics and Pharmacology, Montreal; ²Departments of Biochemistry and ³Chemistry, Université de Montréal, Montreal; ⁴Department of Pharmacology, Sherbrooke University, Sherbrooke; ⁵Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada; ⁶Department of Endocrinology, INSERM U661, Université Montpellier I, France

Submitted September 12, 2008 ; accepted in final form July 13, 2009

Vasopressin type 2 receptor (V2R) exhibits mostly important properties for hydroosmotic equilibrium and, to a lesser extent, on vasomotricity. Drugs currently acting on this receptor are analogs of the natural neuropeptide, arginine vasopressin (AVP), and hence are competitive ligands. Peptides that reproduce specific sequences of a given receptor have lately been reported to interfere with its action, and if such molecules arise from regions remote from the binding site they would be anticipated to exhibit noncompetitive antagonism, but this has yet to be shown for V2R. Six peptides reproducing juxtamembranous regions of V2R were designed and screened; the most effective peptide, cravky (labeled VRQ397), was characterized. VRQ397 was potent (IC₅₀ = 0.69 ± 0.25 nM) and fully effective in inhibiting V2R-dependent physiological function, specifically desmopressin-L-desamino-8-arginine-vasopressin (DDAVP)-induced cremasteric vasorelaxation; this physiological functional assay was utilized to avoid overlooking interference of specific signaling events. A dose-response profile revealed a noncompetitive property of VRQ397; correspondingly, VRQ397 bound specifically to V2R-expressing cells could not displace its natural ligand, AVP, but modulated AVP binding kinetics (dissociation rate). Specificity of VRQ397 was further confirmed by its inability to bind to homologous V1 and oxytocin receptors and its inefficacy to alter responses to stimulation of these receptors. VRQ397 exhibited pharmacological permissiveness on V2R-induced signals, as it inhibited DDAVP-induced PGI₂ generation but not that of cAMP or recruitment of β-arrestin2. Consistent with in vitro and ex vivo effects as a V2R antagonist, VRQ397 displayed anticipated in vivo aquaretic efficacy. We hereby describe the discovery of a first potent noncompetitive antagonist of V2R, which exhibits functional selectivity, in line with properties of a negative allosteric modulator.

vasopressin; allosteric modulator; G protein-coupled receptor