MAPK3 is a member of the MAP kinase family. MAP kinases, also known as extracellular signalregulated kinases (ERKs), act in a signaling cascade that regulates various cellular processes such as proliferation, differentiation, and cell cycle progression in response to a variety of extracellular signals. This protein is activated by upstream kinases, resulting in its translocation to the nucleus where it phosphorylates nuclear targets.