Functional Rescue of a Nephrogenic Diabetes Insipidus Causing Mutation in the V2 Vasopressin Receptor by Specific Antagonist and Agonist Pharmacochaperones

Abstract

The urine concentrating function of the kidney is essential to maintain the water homeostasis of the human body. It is mainly regulated by the arginine-vasopressin (AVP), which targets the type 2 vasopressin receptor (V2R) in the kidney. The inability of V2R to respond to AVP stimulation leads to decreased urine concentration and congenital nephrogenic diabetes insipidus (NDI). NDI is characterized by polyuria, polydipsia, and hyposthenuria. In this study, we identified a point mutation (S127F) in the AVPR2 gene of an NDI patient, and we characterized the impaired function of the V2R mutant in HEK293 cells. Based on our data, the S127F-V2R mutant is almost exclusively located intracellularly in the endoplasmic reticulum (ER), and very few receptors were detected at the cell surface, where the receptor can bind to AVP. The overexpressed S127F-V2R mutant receptor has negligible cAMP generation capability compared to the wild-type receptor in response to AVP stimulation. Since certain misfolded mutant proteins, that are retained in the ER, can be rescued by pharmacological chaperones, we examined the potential rescue effects of two pharmacochaperones on the S127F-V2R. We found that pretreatment with both tolvaptan (an established V2R inverse agonist) and MCF14 compound (a cell-permeable high-affinity agonist for the V2R) were capable of partially restoring the cAMP generating function of the receptor in response to vasopressin stimulation. According to our data, both cell permeant agonists and antagonists can function as pharmacochaperones, and serve as the starting compounds to develop medicines for patients carrying the S127F mutation.

Can tolvaptan usage cause cytotoxicity? An in vitro study

“…More than 10-5 M concentration of tolvaptan could cause cytotoxicity with more than 24 h which is known through the clinical studies. However, in this study the experiments were performed for only 24 h because PC studies (which were mentioned in detailed belove) mostly treat cells with PCs for 18-24 h and short-time treatment is mostly enough to rescue of mutant protein using with PCs [18,38].…”

“…Instead, it can cause the mutant V2 receptor is retained in the ER quality control mechanism. Therefore, even if these mutant V2 receptors are functional, they cannot escape from the ER and locate on plasma membrane where they function [18,38]. To correct this trafficking problem and make mutant V2 receptors functional again, PCs can be used because they are nonpeptide and cell-permeable ligands that bind specifically to the mutant receptor and stabilize receptors conformation [42].…”

“…To correct this trafficking problem and make mutant V2 receptors functional again, PCs can be used because they are nonpeptide and cell-permeable ligands that bind specifically to the mutant receptor and stabilize receptors conformation [42]. In this way, PCs help mutant V2 receptors to be rescued and located where they are functional again [38,43,44]. Tolvaptan is a kind of PC that commonly used in these studies because its rescue potential which was reported by many researches has an importance on to develop new treatment strategies for NDI [17][18][19].…”

V2 vasopressin receptor mutations: future personalized therapy based on individual molecular biology

“…According to a study, 25% of heterozygous women carrying a mutant AVPR2 gene had symptoms, and 6% had complete XNDI ( 30 ). Mild, subclinical XNDI in women is often diagnosed only after the birth of a male descendant showing marked symptoms ( 31 ). This phenomenon raises the possibility that XNDI has greater prevalence in the population than is currently recognized in the literature.…”

“…Maturing de novo synthetized proteins may also be retained in the Golgi ( 35 ). The mutations leading to intracellular retention of the misfolded receptors may result in otherwise functional V2Rs with greatly decreased cell surface expression ( 31 , 32 , 36 ).…”