Abstract
“MAPK” was first reported by Sturgill and Ray in 19861;. This protein kinase was originally described as a 42-kDa insulin-stimulated protein kinase activity whose tyrosine phosphorylation increased after insulin exposure, and which phosphorylated the cytoskeletal protein MAP-2 (hence “MAP” kinase). Contemporaneous studies by Boulton and Cobb identified an additional 44-kDa isoform of MAPK, which they named ERK1 (extracellular signal regulated kinase)2. Since many growth factors and mitogens could activate MAPK, the acronym for this enzyme has subsequently been considered to denote mitogen-activated protein (MAP) kinase. In the following years, additional studies demonstrated that the p42/p44 MAPKs regulated another protein kinase activity (p90rsk)3and that they were themselves regulated by a protein kinase activity originally designated MKK (MAPK kinase)4’5