Misfolded vasopressin V-2 receptors caused by extracellular point mutations entail congential nephrogenic diabetes insipidus

Vasopressin V-2 receptor mutants from three different patients with congeni tal nephrogenic diabetes insipidus phenotypes were investigated after expre ssion in COS cells. The amino acid exchanges within the human V-2 receptor are located in the second extracellular loop (T204N, Y205C and V206D). Conf ocal microscopy showed that all receptor mutants were strongly expressed bu t mainly located within the cell. Residual binding capacity for the antidiu retic hormone arginine vasopressin (AVP) could only be detected for the T20 4N mutant and was 10-fold lower than for the wild-type receptor. Stimulatio n of transfected cells with 1 mu M AVP showed that the T204N mutant was abl e to activate the adenylyl cyclase pathway. In contrast, the Y205C mutant w as almost inactive and stimulation of the V206D mutant increased the cAMP a ccumulation only slightly. Dose dependent stimulation of cells expressing t he T204N mutant with AVP and with the therapeutic AVP analogue 1-deamino[D- Arg(8)]vasopressin (dDAVP) revealed that AVP was 50-fold more potent than d DAVP. This indicates that the ligand binding selectivity of the T204N mutan t has changed as compared with the wild-type receptor where AVP is only 2.3 -fold more potent than dDAVP. Despite its defects in membrane localization, ligand binding affinity and selectivity, the T204N receptor could be activ ated with high concentrations of dDAVP. Our results indicate that in cases of congenital nephrogenic diabetes insipidus with residual V-2 receptor act ivities the use of antidiuretic drugs, such as dDAVP, might be beneficial f or patients. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.