Phosphoinositide cascade. The cleavage of phosphatidylinositol 4,5-bisphosphate (PIP₂) into diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP₃) results in the release of calcium ions (owing to the opening of the IP₃ receptor ion channels) and the activation of protein kinase C (owing to the binding of protein kinase C to free DAG in the membrane). Calcium ions bind to protein kinase C and help facilitate its activation.