Mitogen-activated protein kinase (MAPK) signaling cascades are a group of protein kinases that play a central role in the intracellular transmission of extracellular signals. These cascades operate as major lines of communication within a complicated signaling network that regulates many cellular processes, including proliferation, differentiation, development, stress response, and apoptosis. More than 15,000 papers on MAPKs have been published over the past few years, with the number of publications increasing each year. More and more laboratories embark on the study of MAPK cascades in many d- tinct cellular systems and in particular their role in disease. Future challenges in the study of MAPK cascades remain in understa- ing the role of the various components and isoforms of the cascades in the multiple critical functions that they regulate in the whole organism, as well as the diseases caused by their malfunction. Data from gene-disrupted mice s- gest that inhibition of the MAPK cascades may have serious consequences on the development and growth of the animals. For example, targeted deletion of MEK1 is lethal, owing to developmental problems of placental vasculature and abnormal fibroblast migration. This lethality occurs in spite of the normal expression of MEK2, indicating that although the two MEK isoforms are apparently similar, they do have distinct functions, at least during embryog- esis. The ERK cascade was also shown to play a central role in brain function and in learning and memory.weiterlesen