Calcium is the most abundant cation in the body, mainly in the mineral phase of bones (99%). In addition, calcium serves as a universal intracellular messenger in the cell due to the fact that, unlike other cations such as potassium and sodium, extracellular free calcium concentration is approximately 10,000 times that of intracellular free calcium. Calcium enters the cell, and in turn, the body through ion channels which are tightly regulated. Our project examined the functional regulation of the recently identified vitamin D responsive epithelial calcium channels, CaT1 and CaT2, which are gatekeepers for calcium absorption and reabsorption. Our hypothesis was that CaT1 and CaT2 are under regulation by phosphorylation mediated by protein kinases A and C, as there are consensus phosphorylation sites in the two proteins. To test the hypothesis, we expressed CaT1 and CaT2 in African clawed frog eggs and examined whether the functions of the channels are affected by activation of protein kinase A or C. We expected this project to provide some insight into how functions of these calcium channels are regulated. Our initial results show a decrease in activity in the calcium channels after it was exposed to a protein kinase C activator.
