Ionomycin is an ionophore, a compound that binds calcium ions reversibly, and is used to transport calcium ions across the cell’s plasma membrane, increasing cellular calcium concentration. This increased concentration activates the protein-tyrosine kinase 2-beta, which is responsible for regulation of actin in the cell’s cytoskeleton, as well as cell movement, polarization, adhesion and spreading. It is also important for B-cells and T-cells to migrate and spread. When the P2Y purinoceptor 2 is activated on the cell surface, it activates 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase gamma-1 (PLCG1), an enzyme that is responsible for regulating the conversion of phosphatidylinositol (PIP2) into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DG). IP3 then activates an IP3 sensitive calcium channel, increasing the concentration of intracellular calcium. The calcium can activate protein-tyrosine kinase 2-beta, and can also activate protein kinase C. DG also works to activate protein kinase C in the cell. Phorbal esters are compounds found in certain families of plants, and are found to promote tumor growth. As such, they are commonly used in research. In this pathway, they are shown to activate protein kinase C in the same way as calcium does, as well as mimicking the action of DG. Phorbal esters, in conjunction with ionomycin, are used in this case to study the cellular response to DAG and calcium signalling without needing the cells to undergo other stimulation, mimicking things like T-cell activation easily.

Ion Channel and Phorbal Esters Signaling Pathway References