Modulation of cAMP effects by Ca2+/calmodulin

The second messenger molecules cAMP and Ca²⁺ regulate a large number of eukaryotic cellular events. cAMP acts on protein kinases and Ca²⁺ works through a ubiquitous calcium-binding protein, calmodulin. The two systems are not independent, however, but interact in several important fashions. These interactions, and, in particular, the modulation of the cAMP signal by two Ca²⁺/calmodulin-regulated proteins, cyclic nucleotide phosphodiesterase and calcineurin, are described here.