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This Article Full Text Full Text (PDF) All Versions of this Article: 297/6/F1518    most recent 00331.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Færch, M. Articles by Corydon, T. J. PubMed PubMed Citation Articles by Færch, M. Articles by Corydon, T. J.

Diverse vasopressin V2 receptor functionality underlying partial congenital nephrogenic diabetes insipidus

¹Department of Pediatrics, and ; ²Research Unit for Molecular Medicine, Aarhus University Hospital, Skejby; ; ³Department of Human Genetics, Aarhus University, Aarhus, Denmark; ; ⁴Department of Endocrinology, Sahlgrenska University Hospital, Göteborg, Sweden; and ; ⁵Department of Pediatrics, University of Leuven, Belgium

Submitted June 4, 2009 ; accepted in final form October 5, 2009

X-linked congenital nephrogenic diabetes insipidus (CNDI) is characterized by a defective renal response to the antidiuretic hormone (AVP) due to variations in the arginine vasopressin receptor 2 (AVPR2) gene. In a unique group of patients, the renal insensitivity to the effects of AVP is incomplete resulting in a partial phenotype. To investigate the molecular defects, two previously published variations in the AVPR2 gene, known to cause a partial CNDI phenotype, were expressed in transiently transfected human embryonic kidney cells. One variation (p.Arg104Cys) is located in the first extracellular loop and the other variation (p.Ser329Arg) is located in the intracellular COOH terminal of the receptor protein. Western blotting showed almost equal amounts of WT-V2R and Arg104Cys-V2R protein at steady state, whereas the level of Ser329Arg-V2R protein was lower. Confocal microscopy established that WT-V2R and Arg104Cys-V2R are localized on the cellular surface while the Ser329Arg-V2R primarily accumulates within the endoplasmic reticulum resulting in reduced surface expression. Ligand binding analysis demonstrated that the B_max for cells expressing Arg104Cys-V2R and Ser329Arg-V2R were 14.8- and 2.5-fold lower than B_max for WT-V2R, respectively. AVP affinity (1/K_d) for WT-V2R and the Ser329Arg-V2R was similar while 1/K_d for Arg104Cys-V2R was increased. cAMP assay revealed that cells expressing p.Arg104Cys-V2R or p.Ser329Arg-V2R produced 1.7- and 6.8-fold lower amounts of cAMP compared with WT-V2R, respectively. In conclusion, ligand binding and signal transduction capability are dependent on localization of the amino acid variation. Striking divergences at the level of receptor functionality may thus underlie similar clinical phenotypes in CNDI.

partial phenotype; arginine vasopressin receptor type 2; heterologous expression