Activated p38 MAPK is known to activate the Ser/Thr protein kinase MAP kinase-activated protein kinase 2 (MAPK2/MAPKAPK2) and a closely related kinase, MAPKAP kinase 3. MAPK2 is phosphorylated on T222, S272, and T334 (Ben-Levy et al. 1995). MAPK3 shows 75% sequence identity to MAPK2 and, like MAPK2, is phosphorylated by p38 but the exact phosphorylation sites are not determined. According to some authors, NGF does not induce any significant activation of MAPKAPK2 activity in PC12 cells. Potential p38 signaling effectors include transcription factors, such as cAMP-response element-binding protein and MEF2, cytoskeleton modulators, and a number of protein kinases. After activation, MAPKAP kinase 2 and 3 move to the nucleus.