Specificity in the cAMP/PKA signaling pathway. Differential expression, regulation, and subcellular localization of subunits of PKA

A large number of hormones, neurotransmitters and other signal substances u tilize adenosine 3',5' cyclic monophosphate (cAMP) as an intracellular seco nd messenger. Cyclic AMP regulates a number of different cellular processes such as cell growth and differentiation, ion channel conductivity, synapti c release of neurotransmitters, and gene transcription. The principle intra cellular target for cAMP in mammalian cells is the cAMP-dependent protein k inase (PKA). The fact that this broad specificity protein kinase mediates a number of discrete physiological responses following cAMP-engagement, has raised the question of how specificity is maintained in the cAMP/PKA system . Here we will describe features of this signaling pathway that may contrib ute to explain how differential effects of cAMP may be contributed to featu res of the PKA signaling pathway.