Heterologously expressed G-protein coupled receptor in yeast
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G-protein coupled receptors (GPCRs) are cell surface receptors containing seven transmembrane helices that play critical roles as signaling molecules. Very little structural information is available about how these receptors interact with their ligands, making it difficult to design effective agonists or antagonists to modulate their activities. In order to study GPCR activation and to facilitate discovery of novel modulators, we expressed human GPCRs in yeast. Yeast is an attractive system for studying GPCRs, as the GPCR pathway is conserved in both yeast and mammalian cells. A large number of mammalian GPCRs have been expressed in yeast, and a few have been functionally coupled to a reporter activity. Our goal is to develop a novel yeast-based screening system to accelerate the discovery of activators or inhibitors for physiologically important GPCR proteins. As the first model system, we have expressed human arginine vasopressin receptor 2 (AVPR2) in yeast. It is the physiological target of the peptide hormone vasopressin and mediates antidiuretic behaviour and blood pressure. We demonstrated that the receptor is expressed at a high level in yeast by flow cytometry. The receptor function is measured using the β-galactosidase assay. After the successful AVPR2 expression in yeast, we expressed human neutrophil chemokine receptor (CXCR1) and its ligand, interleukin-8, which are involved in neutrophil activation, in order to develop a highly effective screen of activators or inhibitors regardless of the ligand size. With a heterologously engineered AVPR2 system, we will be able to screen small molecule libraries and verify the physiological effects of the identified compounds in follow-up in vivo assays using a model organism.