Cascades and Cell Signalling

A cascade, in biological terms, refers to a series of chain reactions used by cells to amplify and send a signal, generally for regulatory processes such as control of transcription. In many cases, cascades are also used in cell-to-cell signaling. Amplification of a signal results when one enzyme associated with a signal receptor is activated by a hormone or ligand, and, in turn, catalyzes a reaction which activates many more enzymes which each catalyze a new reaction causing activation of many more enzymes. The process is somewhat like a phone tree for emergency purposes, where the most people are reached in the least number of steps, starting with a single individual.

Of the many types of enzymes, the protein kinases are frequently found in cascade systems. Kinases add a phosphate molecule to other proteins. Cascades often consist of chain reactions of kinases phosphorylating one another, amplifying a signal by several orders of magnitude in a fraction of a second. Phosphatases, which remove phosphate groups, are also involved in signal transduction and nucleotides adenosine-3',5'-cyclic monophosphate and its guanosine counterpart (cyclic AMP and cyclic GMP) are also often found to play key roles in regulatory processes. The basic prinicples of smart polymer design is to mimic the processes, thus the efficiency, of cell signalling pathways and cascades.