Calcium is an important second messenger for many cellular processes; therefore, its presence is tightly regulated within cells. Cells have developed at least five calcium buffering mechanisms: the plasma membrane Ca2+-ATPase and Na+/Ca2+ exchanger, the Ca2+-ATPase on the endoplasmic reticulum, the mitochondria, and cytosolic calcium buffering proteins. Since a rise in calcium is the final step in taste transduction, the presence of calcium must be tightly regulated in taste cells as well; however, the calcium buffering mechanisms used by taste cells are not known. It is likely that different calcium buffering mechanisms contribute to the formation and modulation of the calcium signal in response to taste stimuli. This is probably critical in determining how a taste cell communicates to other cells. This application intends to characterize the calcium buffering mechanisms that are present in taste cells. It will correlate their expression with the different cell types that are present in taste buds. It has been shown previously that there are two distinct electrophysiological profiles in taste cells, those with voltage gated calcium channels and those without. These two different profiles correlate loosely with cell type. The first hypothesis is that there will be different calcium buffering mechanisms, depending on whether the cells express calcium channels or not. The second hypothesis is that calcium buffering mechanisms are important components in the formation of the cell's response to taste stimuli.
The specific aims of this application are: (1) Characterize the expression of calcium buffering mechanisms present in taste cells and correlate their expression to different cell types; (2) Determine the physiological role of calcium buffering mechanisms in taste cells and determine their role in shaping the Ca2+ response to taste stimuli.
These aims will be accomplished by using molecular techniques for aim 1 and calcium imaging for aim 2. Results from the proposed experiments will provide new information about how taste cells generate Ca2+ signals and communicate to other cells/afferent neurons. These data will determine if there are differences between taste cells that have calcium influx through voltage gated calcium channels and cells that use the PLC signaling pathway that results in calcium release from intracellular stores. This data will further our understanding about how taste cells generate a signal in response to a taste stimuli. ? ?
