Abstract
Substitution of arginine-137 of the vasopressin type 2 receptor (V2R) for histidine (R137H-V2R) leads to nephrogenic diabetes insipidus (NDI), whereas substitution of the same residue to cysteine or leucine (R137C/L-V2R) causes the nephrogenic syndrome of inappropriate antidiuresis (NSIAD). These two diseases have opposite clinical outcomes. Still, the three mutant receptors were shown to share constitutive β-arrestin recruitment and endocytosis, resistance to vasopressin-stimulated cAMP production and mitogen-activated protein kinase activation, and compromised cell surface targeting, raising questions about the contribution of these phenomenons to the diseases and their potential treatments. Blocking endocytosis exacerbated the elevated basal cAMP levels promoted by R137C/L-V2R but not the cAMP production elicited by R137H-V2R, demonstrating that substitution of Arg137 to Cys/Leu, but not His, leads to constitutive V2R-stimulated cAMP accumulation that most likely underlies NSIAD. The constitutively elevated endocytosis of R137C/L-V2R attenuates the signaling and most likely reduces the severity of NSIAD, whereas the elevated endocytosis of R137H-V2R probably contributes to NDI. The constitutive signaling of R137C/L-V2R was not inhibited by treatment with the V2R inverse agonist satavaptan (SR121463). In contrast, owing to its pharmacological chaperone property, SR121463 increased the R137C/L-V2R maturation and cell surface targeting, leading to a further increase in basal cAMP production, thus disqualifying it as a potential treatment for patients with R137C/L-V2R-induced NSIAD. However, vasopressin was found to promote β-arrestin/AP-2-dependent internalization of R137H/C/L-V2R beyond their already elevated endocytosis levels, raising the possibility that vasopressin could have a therapeutic value for patients with R137C/L-V2R-induced NSIAD by reducing steady-state surface receptor levels, thus lowering basal cAMP production.
Footnotes
↵ The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
This work was supported by the National Institutes of Health National Institute on Drug Abuse [Grants DA010711, DA012864]; the National Institutes of Health National Institute of Mental Health [Grant 1K08-MH68691-01]; the Kidney Foundation of Canada; and studentships, fellowships, and awards from the Canadian Institute of Health Research, the Fond de la Recherche en Santé du Québec, and the Canada Research Chair in Signal Transduction and Molecular Pharmacology.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.109.061804.
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ABBREVIATIONS:
- V2R
- vasopressin type 2 receptor
- AVP
- arginine vasopressin
- AP-2
- adaptin 2
- AQP2
- aquaporin 2 water channel
- GPCR
- G protein-coupled receptor
- NDI
- nephrogenic diabetes insipidus
- NSIAD
- nephrogenic syndrome of inappropriate antidiuresis
- MAPK
- mitogen-activated protein kinase
- DMEM
- Dulbecco's modified Eagle's medium
- ERK
- extracellular signal-regulated kinase
- P-ERK
- phosphorylated ERK
- BRET1
- first generation of bioluminescence resonance energy transfer
- HTRF
- homogeneous time-resolved fluorescence technology
- Rluc
- Renilla reniformis luciferase
- EYFP
- enhanced yellow fluorescent protein
- DynK44A
- dominant negative mutant of dynamin
- HEK
- human embryonic kidney
- PAGE
- polyacrylamide gel electrophoresis
- PBS
- phosphate-buffered saline
- WT
- wild type
- GIRK
- G protein-activated inwardly rectifying potassium channel
- ANOVA
- analysis of variance
- ELISA
- enzyme-linked immunosorbent assay
- SR121463
- satavaptan
- CRE
- cAMP response element.
- Received October 20, 2009.
- Accepted February 12, 2010.
- Copyright © 2010 The American Society for Pharmacology and Experimental Therapeutics
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