Endocrine Abstracts

The V2 vasopressin receptor (V2-R) mediates the effect of vasopressin on the water reabsorption in the kidney and several mutations in the V2-R have been identified causing nephrogenic diabetes insipidus (NDI). In this study, we investigated a previously not characterized mutation of the. We obtained genomic DNA of a young male patient with NDI, the AVPR2 gene was amplified with PCR and a missense mutation (S127F) was identified. We monitored the cellular localization of the S127F mutant V2 receptor using HA-tagged receptors in confocal microscopy experiments. The S127F V2 receptor was detected only in the endoplasmic reticulum but not in the plasma membrane. We also measured the cAMP signaling capability of the mutant receptor with BRET measurements. The S127F receptor was not able to increase the intracellular cAMP levels in response to vasopressin stimulation. Certain ER retention mutations can be rescued by pharmacological chaperones, which cause misfolded mutant receptors to present in the plasma membrane. We examined the effect of tolvaptan (V2R antagonist) on the S127F V2 receptor. HEK293 cells were transiently transfected with the plasmid of the mutant receptor and after one day the cells were incubated for 18 hours with tolvaptan. After the pretreatment, the cells were exposed to vasopressin, and we were able to detect cAMP signal generation of the mutant receptor. We checked whether the result after tolvaptan pretreatment was due to restored plasma membrane location of the receptor. We were able to demonstrate significant increase of the mutant receptors in the plasma membrane using flow cytometry. Since the tolvaptan is already used in the treatment of multiple diseases, we plan to carry out clinical studies to assess the potential therapeutic usage of this drug in the NDI patients with S127F V2R mutation. This work was supported by National Research, Development and Innovation Fund (NKFI K116954).