<Li> Many cell surface receptors, including G protein - coupled receptors and receptor tyrosine kinases activate the phospholipase C (PLC) enzyme . </Li> <Li> PLC hydrolyses the membrane phospholipid PIP2 to form IP3 and diacylglycerol (DAG), two classical second messengers . </Li> <Li> DAG recruits protein kinase C (PKC), attaching it to the plasma membrane </Li> <Li> IP diffuses to the endoplasmic reticulum, and binds to an IP3 receptor, </Li>

The second messenger which opens calcium ion pores in er and plasma membrane is