||Mitogen-activated protein kinase 3 encoded by MAP2K3 is a dual specificity protein kinase that belongs to the MAP kinase kinase family. Mitogen-activated protein kinase 3 is activated by mitogenic and environmental stress, and participates in the MAP kinase-mediated signaling cascade. It phosphorylates and thus activates MAPK14/p38-MAPK. Mitogen-activated protein kinase 3 can be activated by insulin, and is necessary for the expression of glucose transporter. Expression of RAS oncogene is found to result in the accumulation of the active form of this kinase, which thus leads to the constitutive activation of MAPK14, and confers oncogenic transformation of primary cells. The inhibition of Mitogen-activated protein kinase 3 is involved in the pathogenesis of Yersina pseudotuberculosis. Multiple alternatively spliced transcript variants that encode distinct isoforms have been reported for MAP2K3.