FunctionAtypical MAPK protein. Phosphorylates microtubule-associated protein 2 (MAP2) and MAPKAPK5. The precise role of the complex formed with MAPKAPK5 is still unclear, but the complex follows a complex set of phosphorylation events: upon interaction with atypical MAPKAPK5, ERK4/MAPK4 is phosphorylated at Ser-186 and then mediates phosphorylation and activation of MAPKAPK5, which in turn phosphorylates ERK4/MAPK4. May promote entry in the cell cycle.
Tissue specificityHigh expression in heart and brain.
Sequence similaritiesBelongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. MAP kinase subfamily. Contains 1 protein kinase domain.
DomainThe FRIEDE motif is required for docking MAPKAPK5. In contrast to classical MAPKs, the TXY motif within the activation loop is replaced by the SEG motif, whose phosphorylation activates the MAP kinases.
Post-translational modificationsPhosphorylated at Ser-186 by PAK1, PAK2 and PAK3 resulting in catalytic activation. Phosphorylated by MAPKAPK5 at other sites.
Cellular localizationCytoplasm. Nucleus. Translocates to the cytoplasm following interaction with MAPKAPK5.