Extracellular signal-regulated kinase(ERK),the first mitogen-activated protein kinase(MAPK) to be identified,controls many kinds of important cell biological processes,such as cell proliferation,differentiation,apoptosis and more.MAPK signal cascade specificully regulates various biological processes,the mechanisms of which including regulation by feedback loops,interaction with specific scaffold proteins,changes in subcellular localization,presence of multiple components with distinct functions in each tier of the cascade,nonphosphatase inhibitors of ERK signaling and G protein.