Analysis of the V2 Vasopressin Receptor (V2R) Mutations Causing Partial Nephrogenic Diabetes Insipidus Highlights a Sustainable Signaling by a Non-peptide V2R Agonist

Noriko Makita,Tomohiko Sato,Yuki Yajima-Shoji,Junichiro Sato,Katsunori Manaka,Makiko Eda-Hashimoto,Masanori Ootaki,Naoki Matsumoto,Masaomi Nangaku,Taroh Iiri

doi:10.1074/jbc.m116.733220

Abstract

Disease-causing mutations in G protein-coupled receptor (GPCR) genes, including the V2 vasopressin receptor (V2R) gene, often cause misfolded receptors, leading to a defect in plasma membrane trafficking. A novel V2R mutation, T273M, identified in a boy with partial nephrogenic diabetes insipidus (NDI), shows intracellular localization and partial defects similar to the two mutants we described previously (10). Although non-peptide V2R antagonists have been shown to rescue the membrane localization of V2R mutants, their level of functional rescue is weak. Interestingly, it has been reported that a non-peptide agonist, OPC51803, activates misfolded V2R mutants intracellularly without degradation, thus potentially serving as a therapeutic agent against NDI (14). In our current experiments, however, a peptide antagonist blocked arginine vasopressin (AVP)- or OPC51803-stimulated cAMP accumulation both in COS-7 and MDCK cells, suggesting that OPC51803 mainly stimulates cell surface V2R mutants. In addition, our analyses revealed that OPC51803 works not only as a non-peptide agonist that causes activation/β-arrestin-dependent desensitization of V2R mutants expressed at the plasma membrane but also as a pharmacochaperone that promotes the endoplasmic reticulum-retained mutant maturation and trafficking to the plasma membrane. The ratio of the pharmacochaperone effect to the desensitization effect likely correlates negatively with the residual function of the tested mutants, suggesting that OPC5 has a more favorable effect on the V2R mutants with a less residual function. We speculated that the canceling of the desensitization effect of OPC51803 by the pharmacochaperone effect after long-term treatment may produce sustainable signaling, and thus pharmacochaperone agonists such as OPC51803 may serve as promising therapeutics for NDI caused by misfolded V2R mutants.

Highlights

Ministry of Education, Science, Sports, and Culture, Japan
Identification of a New V2 Receptor Mutation in a Partial nephrogenic diabetes insipidus (NDI) Patient—A 4-year-old male patient showing polydipsia and polyuria was suspected of having NDI based on an increased basal arginine vasopressin (AVP) level
Our present findings suggest that OPC5 may activate V2R-WT and V2R mutants expressed at the plasma membrane, which likely contrasts with the earlier findings, at least in part

Summary

Introduction

Ministry of Education, Science, Sports, and Culture, Japan. The authors declare that they have no conflicts of interest with the contents of this article. 1 To whom correspondence may be addressed: 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Several kinds of pharmacological chaperones have been described [5,6,7,8,9], and we have recently reported that OPC31260 (OPC3) and OPC41061 (OPC4) show unique action against wild-type and two mutant V2R variants including a novel Ser333del mutant, V2R, that we had identified previously [10] These agents augmented basal cAMP accumulation in cells expressing mutant V2R by working as pharmacochaperones but suppressed basal cAMP accumulation in cells expressing wild-type V2R by functioning as inverse agonists. We identified a novel V2R mutation in a 4-year-old boy diagnosed with partial NDI due to his high basal AVP levels This novel mutant receptor was found to localize mainly in the ER, similar to the two NDI V2R mutants we reported previously [10]. V2 Receptor Mutations and Sustainable Signaling we identified a novel mechanism of action of OPC5 in our current study that may enable sustained signaling by these receptor mutants

Methods

Results

Discussion

Conclusion