MAPK cascade An intracellular protein kinase cascade containing at least a MAPK, a MAPKK and a MAP3K. The cascade can also contain an additional tiers: the upstream MAP4K. The kinases in each tier phosphorylate and activate the kinase in the downstream tier to transmit a signal within a cell. ERK/MAPK cascade GO:0000165 MAP kinase cascade MAP kinase kinase kinase cascade MAPK cascades lie downstream of many cell surface receptors and cooperate in transmitting various extracellular signals to the nucleus. One way by which the specificity of each cascade is regulated is through the existence of several distinct components in each tier of the different cascades. The cascades are typically named according to the component in the MAPK tier. MAPK signal transduction MAPK signaling MAPK signalling MAPKKK cascade MAPKKK cascade during sporulation Wikipedia:MAPK_cascade Wikipedia:Mitogen-activated_protein_kinase biological_process mitogen-activated protein kinase cascade intracellular signal transduction