Date

August 2006

Document Type

Dissertation

Degree Name

Ph.D.

Department

Dept. of Physiology & Pharmacology

Institution

Oregon Health & Science University

Abstract

The first part of this body of work tests the notion that mutant G protein coupled gonadotropin-releasing hormone receptors (GnRHRs), originally isolated from hypogonadotropic hypogonadism patients, are expressed at the plasma membrane of cells, as had been measured using an epitope tagging technique. In fact, the epitopetag was itself responsible for increasing the cell surface expression of these mutant receptors, with important implications in our understanding of disease. The next part of the work describes where the mutant GnRHRs are, if not at the cell surface, showing them to be retained in the endoplasmic reticulum (ER), away from their site of action. Receptor retention in the ER is reversed by administration of a pharmacological chaperone that binds to the GnRHR and allows proper folding of the protein and thus proper plasma membrane localization. These mutant GnRH receptors reduce the function of wild type GnRH receptors, a dominant-negative effect. The molecular mechanism underlying the dominant-negative action of mutant receptors on the wild type receptor was due to co-retention of both wild type and mutant receptors in the ER. The last part of this work describes an ER protein chaperone, calnexin, that determines whether newly synthesized proteins go to the Golgi for processing or remain in the ER. Calnexin appears to decrease plasma membrane expression of the GnRHRby a physical interaction between the proteins, an event that may be regulated by phosphorylation of calnexin. The observations presented here also suggest that pharmacological chaperones(pharmacoperones) have the potential to be used to treat a number of human diseases characterized by misrouted proteins retained in the ER by calnexin; among these, hypogonadotropic hypogonadism, cystic fibrosis and nephrogenic diabetes insipidus.

Identifier

doi:10.6083/M41V5C06

School

School of Medicine

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