MAP kinase is a serine/threonine kinase that is activated by MEK through a phosphorylation cascade. The cascade starts with extracellular signals transmitted by growth factor-regulated receptor tyrosine kinases or G-protein coupled receptors. Dually phosphorylated (Thr and Tyr) MAP kinase translocates from the cytoplasm to the nucleus, where it phosphorylates protein transcription factors, transducing extracellular signals into genomic responses, proliferation or differentiation.
