The Adenylate Cyclase System: Beta-adrenergic Receptor & Glucagon Receptor

Activation of the beta-adrenergic receptor by epinephrine results in the activation of Gs leading to the exchange of GTP for GDP on Gs-alpha and dissociation of Gs-alpha-GTP from the beta/ gamma subunits. The activated Gs-alpha-GTP can then activate adenylate cyclase resulting in the synthesis of cAMP from ATP. The rise in the second messenger cAMP in the cytoplasm will then activate Protein kinase A which in turn, phosphorylates specific enzymes, thus producing cellular responses. Similarly, activation of the glucagon receptor by glucagon will activate the same cascade intracellularly resulting in a rise in cAMP and activation of Protein kinase A.