Abstract
Nephrogenic diabetes insipidus (NDI) is a rare tubulopathy characterized by urinary concentration defect due to renal resistance to vasopressin. Loss-of-function mutations of vasopressin V2 receptor (V2R) gene (AVPR2) is the most common cause of the disease. We have identified five novel mutations L86P, R113Q, C192S, M272R, and W323_I324insR from NDI-affected patients. Functional characterization of these mutants revealed that R113Q and C192S were normally localized at the basolateral membrane of polarized Madin-Darby Canine Kidney (MDCK) cells and presented proper glycosylation maturation. On the other side, L86P, M272R, and W323_I324insR mutants were retained in endoplasmic reticulum and exhibited immature glycosylation and considerably reduced stability. All five mutants were resistant to administration of vasopressin analogues as evaluated by defective response in cAMP release. In order to rescue the function of the mutated V2R, we tested VX-809, sildenafil citrate, ibuprofen and tolvaptan in MDCK cells. Among these, tolvaptan was effective in rescuing the function of M272R mutation, by both allowing proper glycosylation maturation, membrane sorting and response to dDAVP. These results show an important proof of concept for the use of tolvaptan in patients affected by M272R mutation of V2R causing NDI.
Highlights
Nephrogenic diabetes insipidus (NDI) is a rare tubulopathy characterized by urinary concentration defect due to renal resistance to vasopressin
In the attempt to rescue the disease by testing several potential pharmacological chaperones, we found that mutation M272R of V2 receptor (V2R) was responsive to tolvaptan both in term of maturation, membrane sorting and dDAVP response
The diagnosis was further confirmed by the identification of five novel NDI-causing mutations of AVPR2 gene, namely L86P, R113Q, C192S, M272R, and W323_I324insR-V2R (Table 1)
Summary
Nephrogenic diabetes insipidus (NDI) is a rare tubulopathy characterized by urinary concentration defect due to renal resistance to vasopressin. We have identified five novel mutations L86P, R113Q, C192S, M272R, and W323_I324insR from NDI-affected patients Functional characterization of these mutants revealed that R113Q and C192S were normally localized at the basolateral membrane of polarized Madin-Darby Canine Kidney (MDCK) cells and presented proper glycosylation maturation. Tolvaptan was effective in rescuing the function of M272R mutation, by both allowing proper glycosylation maturation, membrane sorting and response to dDAVP These results show an important proof of concept for the use of tolvaptan in patients affected by M272R mutation of V2R causing NDI. Nephrogenic diabetes insipidus (NDI) is characterized by renal resistance to the hormone vasopressin (AVP) This leads to a defective water reabsorption along the renal collecting duct causing polyuria, hyposthenuria and polydipsia that can end up in life-threating dehydration and hypernatremia mainly in c hildhood[1]. In the attempt to rescue the disease by testing several potential pharmacological chaperones, we found that mutation M272R of V2R was responsive to tolvaptan both in term of maturation, membrane sorting and dDAVP response
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