A novel mitogen-activated protein kinase phosphatase: Structure, expression, and regulation

Mitogen-activated protein (MAP) kinase lies at the convergence of various extracellular ligand-mediated signaling pathways. It is activated by the dual-specificity kinase, MAP kinase kinase or MEK. MAP kinase inactivation is mediated by dephosphorylation via specific MAP kinase phosphatases (MKPs). One MKP (MKP-1 (also known as 3CH134, Erp, or CL100)) has been reported to be expressed in a wide range of tissues and cells. We report the identification of a second widely expressed MKP, termed MKP-2, isolated from PC12 cells. MKP-2 showed significant homology with MKP-1 (58.8% at the amino acid level) and, like MKP-1, displayed vanadate-sensitive phosphatase activity against MAP kinase in vitro. Overexpression of MKP-2 in vivo inhibited MAP kinase-dependent gene transcription in PC12 cells. MKP-2 differed from MKP-1 in its tissue distribution and in its extent of induction by growth factors and agents that induce cellular stress, suggesting that these MKPs may have distinct physiological functions.