Signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another. These processes most often involve ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes, activated by second messengers resulting in what is known as a "signal transduction pathway". Signal transduction is usually rapid, lasting milliseconds in the case of ion flux, minutes for the activation of protein and lipid mediated kinase cascades, or hours and days in terms of gene expression. In single-cell organisms, signal transduction pathways determine how the cell senses and responds to its environment. In multi-cellular organisms, a multitude of different signal transduction pathways are required for coordinating the behavior of individual cells to support the function of the organism as a whole. As may be expected, the more complex the organism, the more complex the repertoire and interconnectivity of signal transduction pathways. Thus, sensing of both the external and internal environment at the cellular level relies on signal transduction.
Many diseases such as diabetes, heart disease, inflammation and cancer arise from defects in signal transduction pathways, underscoring the critical importance of signal transduction in medicine as well as biology. The Basel research community has made many highly recognized contributions in the field of signal transduction, for example, the discoveries of PKB/Akt, S6K, TOR, Cyclosporine A and Gleevec. PKB/Akt, S6K and TOR are three centrally important kinases implicated in many cellular processes and diseases. Cyclosporine A, the first drug to target a phosphatase, enabled allogeneic organ transplantation as a viable therapy. Gleevec, the first drug to target a tyrosine kinase, has revolutionized cancer therapy.