Endocrine Abstracts

The concentrating function of the kidney is important to maintain the water homeostasis of the body. It is regulated by the arginine-vasopressin system through the type 2 vasopressin receptor (V2R). Loss-of-function mutations of V2R in kidney can lead to nephrogenic diabetes insipidus (NDI) which results several symptoms such as polyuria, polydipsia, and hyposthenuria. In this study, we functionally characterized and investigated the potential rescue of a missense mutation (S127F) of the V2R. 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 (a 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 h with tolvaptan. After the pretreatment, the cells were exposed to vasopressin, and we were able to detect significant cAMP signal generation of the mutant receptor. We also 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. We also investigated the effect of pharmacochaperone MCF14 compound (a cell permeable high-affinity agonist for the V2R) on the mutant receptor and we found that the MCF14 was also capable to restore the cAMP signaling function of the receptor. According to our data, pharmacochaperones could be the treatment for patients carrying the S127F mutation.

This work was supported by the National Research, Development and Innovation Fund (NKFI K116954 and NVKP_16-1-2016-0039).