All of the following serve as intracellular second messengers in receptor-mediated signal transduction except
High-Yield Explanation
GPCR do not act as intracellular messengers thery are receptors present on the trans membranes of the cell and help in ligand binding and cell signalling different secondary messengers include cAMP, IP3/DAG,cGMP and some times calcium. Ref: KDT 6/e pg. 39