SecondMessengerSysteme

SecondMessengerSysteme is an umbrella term used to describe the network of intracellular signaling pathways that rely on small, diffusible molecules generated in response to extracellular cues to regulate cellular processes. Classic second messengers include cyclic AMP (cAMP), cyclic GMP (cGMP), calcium ions (Ca2+), inositol trisphosphate (IP3), and diacylglycerol (DAG); additional messengers include nitric oxide (NO), lipid-derived mediators, and, in bacteria, cyclic dinucleotides such as c-di-GMP and c-di-AMP, as well as (p)ppGpp.

Activation of SecondMessengerSysteme commonly begins at the cell membrane through receptors such as G protein-coupled receptors (GPCRs) and receptor tyrosine kinases, which trigger enzymes like adenylyl cyclase, guanylyl cyclase, and phospholipase C. The resulting messengers then activate targets including protein kinases, phosphatases, ion channels, and transcription factors, enabling signal amplification and integration. Termination occurs through degradation by phosphodiesterases and other enzymes, sequestration, or efflux from the cell.

The SecondMessengerSysteme exhibits spatial and temporal organization, with signaling confined to microdomains and characterized by rapid, dynamic changes. This architecture supports diverse physiological processes such as sensory transduction, neurotransmission, muscle contraction, secretion, and immune responses. In bacteria, similar networks regulate biofilm formation, virulence, and stress responses, illustrating evolutionary conservation and diversification of signaling strategies.

Research on SecondMessengerSysteme employs sensors and reporters (for example, genetically encoded indicators), omics approaches, and computational models to map networks and dynamics. Dysregulation of second messenger signaling is linked to diseases, making components like phosphodiesterases, kinases, and channels potential therapeutic targets.