A signalling cascade is an evolutionary-conserved mechanism that is used to amplify a signal, mainly consisting of protein kinases (MAP and MAPK). Once one protein kinase has been activated, this can then go on to phosphorylate many more protein kinases, proliferating the signal, hence the cascade. These cascades control many processes in the cell including development, differentiation and aptosis. The malfunction of a signalling cascade can lead to many diseases such as cancer and diabetes  .
G-protein coupled receptors
When G-protein coupled receptors are activated they can stimulate a signalling cascade by activating other proteins, mainly adenylyl cyclase or phospholipase C. Adenylyl cyclase, for example, then goes on to convert ATP to cAMP which acts as a second messenger to activate protein kinase A. This phosporylates other proteins producing a response in the cell. An example of a reaction regulated by g-protein linked receptors is the release of glucose stimulated by epinephrine.
- ↑ The MAP Kinase Signaling Cascades: A System of Hundreds of Components Regulates a Diverse Array of Physiological Functions. Yonat Keshet1, Rony Seger. Department of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel. Sep-02-2010