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Submitted on October 20, 2004
Accepted on February 15, 2005
Research Unit in Reproductive Medicine (A.L.-M., A.U.-A., P.M.C.), Instituto Mexicano del Seguro Social, México D.F. 10101, Mexico; Divisions of Neuroscience and Reproductive Biology), Oregon National Primate Research Center (A.L.-M, J.A.J., P.M.C., A.U.-A), Beaverton, Oregon 97006; Department of Physiology and Pharmacology and Cell and Developmental Biology, Oregon Health and Science University (P.M.C.)
* To whom correspondence should be addressed. E-mail: alfredo{at}intranet.com.mx or connm{at}ohsu.edu.
We analyzed the function of mutant GnRH receptor (GnRHR) pairs associated with compound heterozygous patients showing complete or partial forms of hypogonadotropic hypogonadism. We did this to examine potential interactions between misfolded mutants that may influence net receptor function and response to pharmacological rescue. Nine pairs of GnRHR mutants and an unreported combination (L314X(stop)/R262Q) were studied. Coexpression of each pair of mutants in COS-7 cells resulted in either an active predominant effect (Q106R/L266R, A171T/Q106R, T32I/C200Y, and R262Q/A129D mutant GnRHR pairs), an additive effect (R262Q/Q106R, N10K/Q106R, and R262Q/Y284C hGnRHR pairs), or a dominant negative effect (L314X(stop)/Q106R, Q106R+S217R/R262Q, and L314X(stop)/R262Q GnRHRs). For all combinations, addition of the pharmacoperone IN3 increased both agonist binding and effector coupling. The IN3 response was unpredictable since responses could be either similar, higher or lower compared with that exhibited by the less affected mutant. The clinical phenotype in patients expressing complex heterozygous alleles appears to be dictated both by the contribution from each mutant and by a dominant negative effect similar to that reported for mutants and wild-type receptor. Depending on the genotype, partial or full restoration of receptor function in response to pharmacological chaperones may be achievable goals in patients bearing inactivating mutations in the GnRHR gene.
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