Toisiovälittäjäaineisiin

Toisiovälittäjäaineisiin, known in English as secondary messengers, are intracellular signaling molecules. They are released by cells in response to stimuli that trigger a signal transduction pathway. These molecules amplify the signal received from a primary messenger, such as a hormone or neurotransmitter, which binds to a cell surface receptor. The primary messenger itself does not typically enter the cell.

Once a primary messenger binds to its receptor, it initiates a cascade of events. This often involves activating enzymes within the cell membrane. These enzymes then catalyze the production or release of secondary messengers. Examples of common secondary messengers include cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP), inositol trisphosphate (IP3), diacylglycerol (DAG), and calcium ions (Ca2+).

These secondary messengers then diffuse throughout the cytoplasm, acting on various cellular targets. These targets can include protein kinases, ion channels, or other enzymes. The binding of secondary messengers to their targets leads to a cascade of biochemical reactions, ultimately resulting in a specific cellular response. This response could be anything from gene expression changes to muscle contraction or secretion of substances. The amplification inherent in this process allows a small initial signal to have a significant effect on the cell.