MOLECULAR CLONING OF THE HUMAN SWEET TASTE RECEPTOR

The sense of taste provides animals with a rapid, though limited chemical analysis of a potential food substance. Based on this information the animal decides whether to ingest or expel the substance. In humans, disorders of taste lead to anorexia and subsequent weight loss, which complicates the management of the underlying diseases. The pathophysiology of taste disorders is poorly understood because little is known about the molecular mechanisms involved in the transduction of any taste modality. Our previous studies have demonstrated that bitter taste transduction involves cell surface receptors. Binding of ligand to these receptors stimulates release of calcium from internal stores suggesting the involvement of the inositol triphosphate pathway in the bitter transduction process. The transduction of sweet taste appears to involve a different mechanism. Purification or molecular cloning of the taste receptors would enhance our understanding of the primary events in taste transduction, however, to date none of the taste receptors have been purified or cloned. The long-term goal of this investigation is to elucidate the molecular mechanisms involved in sweet taste transduction. To accomplish this goal, the technique of DNA-mediated gene transfer will be used to establish a mouse cell line expressing the human sweet taste receptor. To assay for expression of the human sweet taste receptor the two sweet proteins, thaumatin and monellin, will be used in an erythrocyte rosetting assay utilizing anti- thaumatin antibodies coupled to the erythrocytes to detect transformed mouse L-cells expressing the human thaumatin-binding sweet taste receptor. Following establishment of the cell line, the gene for the sweet taste receptor will be molecularly cloned from this cell line. The cell line will also facilitate studies of the mechanism of sweet taste transduction to identify second messenger processes involved in the transduction process. The specific goals of this proposal are: 1) To establish a mouse L-cell line expressing the human sweet taste receptor by the technique of DNA- mediated gene transfer; 2) To utilize the cell line to molecularly clone the human sweet taste receptor, and 3) To utilize the cell line to study the mechanism of sweet taste transduction.