Protein kinase A (PKA) is the main effector of the second messenger cAMP. PKA is made of two regulatory subunits (PRKAR1A, PRKAR1B, PRKAR2A, PRKAR2B) and two catalytic subunits (PRKACA, PRKACB). When cAMP binds the regulatory subunits, the catalytic subunits are released and phosphorylate target proteins such as CREB, ion channels, metabolic enzymes and cytoskeletal proteins. A-kinase anchoring proteins (AKAPs) direct PKA to specific locations in the cell. PKA signaling controls metabolism, heart rate, memory, hormone secretion and gene transcription.