The Role of T1r Taste Receptors in Gustation

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DESCRIPTION (provided by applicant): The long-term objective of our research program is to understand how the vertebrate gustatory system transduces signals and encodes information. Of particular importance are the G protein-coupled receptors (GPCRs) and their coupled G proteins. During the past decade we have identified and characterized several taste transduction elements, including taste receptors (Tlr3), G proteins ((-gustducin, (-transducin, G(13) and ion channels (Trpm5). The scope of this Competing Continuation encompasses the roles in taste transduction and coding of Tlr taste receptors, the G proteins co-expressed with and coupled to these receptors, and the transient receptor potential (Trp) channels expressed in Tlr-positive taste cells. We will use a multidisciplinary approach applying molecular biological, transgenic, behavioral and electrophysiological techniques to achieve the following Specific Aims. 1. To determine if taste cells express Tlr4. 2. To determine which Tlr receptors are co-expressed with Tlr4. 3. To determine which G protein subunits are co-expressed with Tlr receptors. 4. To determine which Trp channels are co-expressed with Tlr receptors. 5. To heterologously express Tlr receptors. 6. To use Caimaging to monitor responses of cells expressing the Tlr receptors. 7. To generate single, double and triple knockout mice lacking Tlr receptors. 8. To behaviorally characterize the Tlr knockout mice. 9. To electrophysiologically characterize the Tlr knockout mice. 10. To generate knockout mice lacking Trpm5. 11. To generate transgenic mice expressing Trpm5 in Tlr2- and Tlr3-positive taste cells. 12. To behaviorally characterize the Trpm5 transgenic mice. 13. To electrophysiologically characterize the Trpm5 transgenic mice. The results of these studies will provide significant new insights into the molecular mechanisms underlying taste transduction and coding. The Tlr receptors are involved in the detection of sugars and sweeteners. A molecular knowledge of their mode of function may lead to the development of novel effective non-caloric sweeteners that may be useful in weight control programs to limit obesity and obesity-related diseases. Gustatory and metabolic disorders such as malgeusia, dysgeusia and cachexia frequently occur in conjunction with several types of cancer. The knowledge gained from this proposal should further our understanding of the molecular bases of taste disorders and may lead to effective intervention.