MAPKK4 (mitogen-activated protein kinase kinase 4) is a dual specificity protein kinase that belongs to the Ser/Thr protein kinase family. MAPKK4 is a direct activator of MAP kinases in response to various environmental stresses or mitogenic stimuli. It has been shown to activate MAPK8/JNK1, MAPK9/JNK2, and MAPK14/p38, but not MAPK1/ERK2 or MAPK3/ERK3. This kinase is phosphorylated, and thus activated by MAP3K1/MEKK. Studies in knockout mice suggest that MAPKK4 mediates survival signals in T cell development. It may also be important to liver organogenesis.[taken from NCBI Entrez Gene (GeneID: 6416)].