High Quality Content by WIKIPEDIA articles! Inositol trisphosphate or inositol 1,4,5-trisphosphate (also commonly known as triphosphoinositol; abbreviated InsP3 or IP3), together with diacylglycerol (DAG), is a secondary messenger molecule used in signal transduction and lipid signaling in biological cells. While DAG stays inside the membrane, IP3 is soluble and diffuses through the cell. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), a phospholipid that is located in the plasma membrane, by phospholipase C (PLC).