PIP2 or Phosphatidylinositol bisphosphate is general term that refers to the products obtained by cleavage of PIP3.
PIP2 is a substrate for cleavage with phospholipase C, a membrane-bound enzyme activated through α1 adrenergic receptors. Products of this reaction are inositol triphosphate (IP3) and diacylglycerol (DAG).
In this cascade, DAG remains in the cellular matrix and activates the signal cascade by activating protein kinase C (pKc). PKc in turn activates other cytosolic proteins by phosphorylating the protein. The effect of pKc can be reversed by phosphodiesterases.
IP3 one is an intracellular second messenger that activates calcium channels on smooth ER, allowing calcium ion diffusion into the cytosol. Calcium helps the cascade by activating other proteins.