What is the role of phosphatidylinositol in the membrane?
Phosphatidylinositol's inositol ring protruding into cytosol can be phosphorylated to produce phosphoinositides that act as transient second messenger precursors. Upon activation of GPCR coupling to Gq or RTK activating PLC-gamma, phospholipase C cleaves PIP2 into diacylglycerol which stays embedded to recruit C1 domain of protein kinase C and Munc13 for exocytosis, and soluble IP3 that binds tetrameric IP3 receptor calcium channels on ER releasing calcium that activates calmodulin and NFAT. Concurrently class I PI3K phosphorylates PIP2 to PIP3 which accumulates transiently and recruits protei
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 15: Phosphoinositide Signaling Cascade.
