Taste perception is initiated by the interaction of sapid molecules with proteins on the surface of taste bud cells. These gustatory signals are subsequently transduced, processed in taste buds, coded and transmitted by cranial nerves to the brain. The long-term objective of our research program is to molecularly identify and functionally characterize key proteins that are involved in taste signal transduction and coding in taste buds, and decoding in the central nervous system, and eventually to reconstruct the molecular events of taste sensation and perception. We have used molecular cloning and functional analyses to identify and characterize a number of taste transduction components, including a G-protein coupled taste receptor T1R3, G protein subunits and a transient receptor potential ion channel TRPM5. In order to understand the molecular events downstream of TRPM5 and to reveal ion channels that are responsible for sour and salty tastes, we have determined the expression of six voltage-dependent calcium channels in taste bud cells.
The specific aims of this proposal are: 1) to identify and colocalize voltage-dependent calcium channel subunits with known taste signaling molecules in taste bud cells;2) to heterologously express and functionally characterize novel isoforms of these voltage-dependent calcium channels isolated from taste buds;3) to determine possible roles of these voltage-dependent calcium channels in taste bud synaptic transmission by monitoring the effect of pharmacological and genetic perturbation of these channels on the elevation of intracellular calcium concentrations and synaptic activity in taste bud cells in response to taste stimuli;4) finally, to determine possible roles of these voltage-dependent calcium channels in taste sensation by gustatory nerve recording and animal behavioral tests with mutant animals. The results of these studies will yield new insights into the molecular mechanisms underling sour, salt, bitter, sweet and umami taste transduction, synaptic transmission and peripheral coding in the end organs of taste. The knowledge gained from this endeavor will further our understanding of the molecular bases of taste disorders such as malgeusia, dysgeusia, hypogeusia and ageusia and may lead to effective treatment.
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