Dual regulation of adenylate cyclase. A signal transduction mechanism of membrane receptors.

The hormone-sensitive adenylate cyclase is a multi-component system embedded in the lipid bilayer of the plasma membrane and serves as a signal transduction system for various membrane receptors. The complete system consists of various receptor molecules, which sensitize the external ligands, the effector enzyme adenylate cyclase, which catalyzes the formation of cyclic AMP from ATP, and two guanine nucleotide-binding regulatory proteins (N or G proteins), which transduce the signals from the receptors to the adenylate cyclase. Depending on the receptor type activated by a ligand, stimulatory or inhibitory, either the stimulatory or the inhibitory N protein is activated and induces stimulation or inhibition of adenylate cyclase with subsequent increase or decrease in cellular cyclic AMP levels. In this paper, the mechanisms of this hormonal signal transduction system and its regulation will briefly reviewed, with some emphasis on the cardiac system.