2000 Global Researcher Conference Proceeding
March 10 - 12, 2000
| Conference: | 2000 Global Researcher Conference |
|---|---|
| Title: | Pharmacological chaperones functionally rescue misfolded mutant V2 vasopressin receptors that cause nephrogenic diabetes insipidus |
| Authors: | Morello, Jean-Pierre; Salahpour, Ali; Laperriere, Andre; Bernier, Virginie; Arthus, Marie-Francoise; Lonergan, Michele; Petaja-Repo, Ulla; Angers, Stephane; Morin, Denis; Bichet, Daniel G.; Bouvier, Michel |
| Institutions: | University of Montreal, Universite de Montreal, Hopital du Sacre-Coeur de Montreal, INSERM U469 |
Naturally occurring mutations involved in inherited diseases often result from misfolding and/or improper targeting of the mutated proteins. Over 100 mutations within the coding sequence of the V2 vasopressin receptor (V2R) gene are known to cause nephrogenic diabetes insipidus (NDI). When expressed in heterologous expression systems, most of these mutant receptors, including many missense mutations, are not expressed at the cell surface most likely as a result of improper folding. Here we show that selective, non-peptidic V2R antagonists (SR121463A and VPA-985) dramatically increase cell surface expression of 8 NDI-V2R bearing different mutations. This leads to the functional rescue of the mutant receptors that can then stimulate cAMP production upon vasopressin stimulation. Metabolic labelling experiments carried out on one of these mutants showed that it was expressed as an immature, readily degraded form of the receptor. Treatment with SR121463A facilitated maturation of the receptor as indicated by the accumulation of a long-lived fully glycosylated form of the receptor and its transport to the plasma membrane. A cell impermeable peptidic V2R antagonist could not mimic these effects and was unable to block the SR121463A-mediated rescue indicating that the non-peptidic antagonists act intracellularly by binding partially folded mutants and facilitating their proper folding and translocation to the cell surface. The onset of the antagonist-promoted translocation and functional rescue was rapid and lasted for at least 24 hours. This profile of functional recovery for V2R mutants opens a new therapeutic perspective for some NDI patients.
There are over 100 mutations of the vasopressin-2 receptor (V2R) gene that result in X-linked NDI (XNDI). The majority of these mutations result in V2R mutants that are unable to reach the cell surface where they must be if they are to perform their function of acting as a receptor to vasopressin (AVP).
Morello, et al., have discovered two chemical substances, SR121463A and VPA-985, which can bind with each of eight different V2R mutants. Once bound to these substances, the mutant V2R are able to reach the cell surface. Once at the cell surface, these eight mutant V2Rs can bind with AVP, thus fulfilling their normal function.
The researchers examined one of the mutant V2Rs and discovered that it only could achieve an immature stage of development. This immature form was readily subject to being degraded by cellular regulatory systems. SR121463A helped the mutant V2R reach full maturation, thus allowing it to be transported to the cell membrane. The researchers indicate that SR121463A helps fold the mutant V2R into its proper shape which helps it reach the cell surface. These two chemical substances, referred to as chaperones, were able to affect the mutant V2Rs quickly and their rescuing effects lasted at least 24 hours. Bichet believes this work can serve as a new direction for helping treat some XNDI patients.