A Low-Affinity Vasopressin V2-Receptor Gene in a Kindred with X-Linked Nephrogenic Diabetes Insipidus
|Title:||A Low-Affinity Vasopressin V2-Receptor Gene in a Kindred with X-Linked Nephrogenic Diabetes Insipidus|
|Authors:||Yokoyama, Kenji; Yamauchi, MD, Atsushi; Izumi, Masaaki; Itoh, Takahito; Ando, Akio; Imai, Enyu; Kamada, Takenobu; Ueda, Naohiko|
|Publisher:||Journal of the American Society of Nephrology|
|Date Published:||March 01, 1996|
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This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)
In the past few years, the genetic basis of hereditary NDI has been established, linking it to mutations in either the V2R gene or the aquaporin-2 (AQP2) gene. Geneticists know what normal V2R genes and AQP2 genes look like, and they have identified a number of different types of mutations in them that result in NDI. Yokoyama, et al., report on the V2R gene mutation of a 46-year-old Japanese male with inherited NDI. His was a missense mutation, a kind of mutation that causes a single amino acid change in the genetic sequence of the gene. In this case, the amino acid 205 Tyr was in the place where Cys was supposed to be. This single amino acid change was located in a part of the V2R gene called the second extracellular loop, which is considered important for hormone binding. Laboratory tests of the mutated V2R revealed it could not bind AVP and this, in turn, inhibited cAMP production.
Speculating about the structure-function relationship of V2R, the authors noted that data on other receptors with similar structures reveal that the first and second extracellular loops are considered to form the three-dimensional structure to which AVP may bind. Since the V2R mutation they studied was in the second extracellular loop, causing a change in the structure of the loop, it is likely that the altered structure was unsuitable for AVP so it could not bind with the receptor and transfer the hormonal message which begins the urine concentrating sequence.