Characterization of variant forms of G protein-coupled receptors

The purpose of the work presented was to characterize the pharmacology of naturally occurring and in vitro engineered variant forms of G protein-coupled receptors (GPCRs). In the first experiment, the mechanisms that regulate agonist induced, homologous, GPCR desensitization were elucidated in a model system with respect to mutagenized forms of the dopamine D ₁, receptor. The hypothesis of this work—that the serine and threonine residues critical to homologous desensitization are distinct from those regulating internalization—was confirmed. In the second experiment, the contribution of naturally occurring variants of the cysteinyl leukotriene (CysLT) receptors to atopy and asthma was elucidated. Variants were discovered in a founder, atopic asthma population resident on the island of Tristan da Cunha. The hypothesis of this work—that a disruption of CysLT signalling results from a CysLT ₂ receptor variant that is associated with atopy—was confirmed. In the third experiment, the hypothesis that variant forms of the CysLT ₁ gene may also contribute to atopy or asthma was tested. A variant was found that was significantly more common in asthmatics than non-asthmatics in the Caucasian population. The characterization of variant forms of GPCRs found naturally in disease populations and/or created in vitro provides insight into the regulation and dysregulation of the GPCR response to agonist.