ABSTRACT
Eukaryotic cells contain switching elements integrated into modules consisting of several interacting signaling proteins. Mitogen-activated protein (MAP) kinase modules are central relay stations of signal transduction from the periphery to the genome. The historically based name is somewhat misleading since MAP kinase modules are by no means activated only by mitogenic signals but also are involved in stress response, cell differentiation, and cell death. A major "spinal cord" of cellular data processing, which rivals the MAP kinase modules in its variedness and complexity, is the signaling pathways that control the nuclear factor. Frequently such input signals are transmitted by protein kinases known as MAP4 kinases that phosphorylate and activate MAP3 kinases, thereby cooperating with G-proteins. MAP kinase-activated protein kinases transduce signals received from the MAP kinase modules. Each family, probably even each MAP kinase subtype, organizes a module of its own.
