cAMP as a Second Messenger

Hormone-Target Cell Interaction: cAMP as a Second Messenger

Water-soluble hormones (modified amino acids other than thyroid hormones, peptides and proteins) interact with cells via receptors found in the plasma membrane. This activates a system that produces second messengers within the cell - either cyclic AMP (cAMP) or diacylglycerol (DAG) and inositol triphosphate. (Mouse over image to begin animation.)

In the cAMP system, hormone interaction with the receptor results in activation of the G protein as GTP displaces GDP. The G protein then moves through the membrane to bind to adenylate cyclase and activate the latter. Adenylate cyclase uses ATP to form cycle AMP (cAMP), which then acts as a second messenger with in the cytosol of the cell. Cyclic AMP activates protein kinases, which, in turn, affect the activity of proteins already present in the cell.