This project is designed to develop and characterize two prototypic genetically modified mouse models for human diseases of protein folding. These models are required to bring a novel class of target-specific drugs, pharmacoperones, to human (and animal) use. Misfolded mutant proteins are detected by the cellular quality control system (QCS) and are typically retained in the endoplasmic reticulum (ER) for either reprocessing or degradation;frequently, these mutants result in disease. Studies in cell cultures indicate that these mutants can be rescued by target-specific small molecules (pharmacoperones) which enter cells, serve as templates that refold the mutants, and permit their passage to the plasma membrane. Many mutants retain or regain their fundamental properties as ion channels, enzymes or receptors when re-routed correctly. Diseases caused by misfolding (which may benefit from this approach) include cystic fibrosis, hypogonadotropic hypogonadism, nephrogenic diabetes insipidus, retinitis pigmentosa, hypercholesterolemia, cataracts, neurodegenerative diseases (Huntington's, Alzheimer's and Parkinson's), cancers and digestive disorders. It is fair to say that virtually every person will be affected by protein folding diseases during his or her lifetime, either directly or due to the illness of a loved one. In spite of this, there are few model systems, and none in small laboratory animals, that allow the translation of available in vitro data or the testing of """"""""hits"""""""" from high throughput screening on protein rescue into in vivo systems. To date, therapeutic approaches in humans have relied on a small number of studies in end-of-life patients, using drugs that have never been fully characterized in animal models. Such models are needed to address drug safety, the pattern of drug administration required to optimize therapeutic effectiveness, and serve as a test model for new drugs in preclinical studies. The pattern (route, dose and frequency) is particularly important as the persistence of these drugs frequently inhibits the desired activity, once rescue has occurred, so they must be removed. Moreover a convenient laboratory model for these diseases is needed if the use of pharmacoperones is to translate to human well-being, since US law requires animal testing prior to normal human volunteers. The present study will characterize prototypic mouse models of misfolding, relying on an unusually well-characterized mutant of a physiologically important GPCR (i.e. the gonadotropin releasing hormone receptor). There is much information available on the mechanism of activation of the gonadotropin releasing hormone receptor (GnRHR) and on the biochemical mechanism by which the mutant E90K is believed to cause the disease state. This information has been helpful in guiding our choices of mutant E90K and will contribute to the success of this project. The two models to be used are available and have the predicted genotype and necessary phenotype.
This project is designed to develop, characterize, compare and contrast two models for human diseases of protein folding. Diseases caused by misfolding include cystic fibrosis, hypogonadotropic hypogonadism, nephrogenic diabetes insipidus, retinitis pigmentosa, hypercholesterolemia, cataracts, neurodegenerative diseases (Huntington's, Alzheimer's and Parkinson's), particular cancers and a number of digestive disorders resulting from enzyme mutation. A convenient laboratory model for these diseases is needed if the use of pharmacoperones is to translate to human well-being, since US law requires animal testing prior to normal human volunteers.
|Stewart, M David; Deng, Jian Ming; Stewart, C Allison et al. (2012) Mice harboring Gnrhr E90K, a mutation that causes protein misfolding and hypogonadotropic hypogonadism in humans, exhibit testis size reduction and ovulation failure. Mol Endocrinol 26:1847-56|
|Janovick, Jo Ann; Pogozheva, Irina D; Mosberg, Henry I et al. (2012) Rescue of misrouted GnRHR mutants reveals its constitutive activity. Mol Endocrinol 26:1179-88|
|Janovick, Jo Ann; Park, Byung S; Conn, P Michael (2011) Therapeutic rescue of misfolded mutants: validation of primary high throughput screens for identification of pharmacoperone drugs. PLoS One 6:e22784|
|Conn, P Michael; Janovick, Jo Ann (2011) Pharmacoperone identification for therapeutic rescue of misfolded mutant proteins. Front Endocrinol (Lausanne) 2:|
|Maya-Nunez, Guadalupe; Janovick, Jo Ann; Aguilar-Rojas, Arturo et al. (2011) Biochemical mechanism of pathogenesis of human gonadotropin-releasing hormone receptor mutants Thr104Ile and Tyr108Cys associated with familial hypogonadotropic hypogonadism. Mol Cell Endocrinol 337:16-23|
|Conn, P Michael; Ulloa-Aguirre, Alfredo (2011) Pharmacological chaperones for misfolded gonadotropin-releasing hormone receptors. Adv Pharmacol 62:109-41|
|Janovick, Jo Ann; Pogozheva, Irina D; Mosberg, Henry I et al. (2011) Salt bridges overlapping the gonadotropin-releasing hormone receptor agonist binding site reveal a coincidence detector for G protein-coupled receptor activation. J Pharmacol Exp Ther 338:430-42|