Protein phosphatase 2Calpha inhibits the human stress-responsive p38 and JNK MAPK pathways.
MAPK (mitogen-activated protein kinase) cascades are common eukaryotic signaling modules that consist of a MAPK, a MAPK kinase (MAPKK) and a MAPKK kinase (MAPKKK). Because phosphorylation is essential for the activation of both MAPKKs and MAPKs, protein phosphatases are likely to be important regulators of signaling through MAPK cascades. To identify protein phosphatases that negatively regulate the stress-responsive p38 and JNK MAPK cascades, we screened human cDNA libraries for genes that down-regulated the yeast HOG1 MAPK pathway, which shares similarities with the p38 and JNK pathways, using a hyperactivating yeast mutant. In this screen, the human protein phosphatase type 2Calpha (PP2Calpha) was found to negatively regulate the HOG1 pathway in yeast. Moreover, when expressed in mammalian cells, PP2Calpha inhibited the activation of the p38 and JNK cascades induced by environmental stresses. Both in vivo and in vitro observations indicated that PP2Calpha dephosphorylated and inactivated MAPKKs (MKK6 and SEK1) and a MAPK (p38) in the stress-responsive MAPK cascades. Furthermore, a direct interaction of PP2Calpha and p38 was demonstrated by a co-immunoprecipitation assay. This interaction was observed only when cells were stimulated with stresses or when a catalytically inactive PP2Calpha mutant was used, suggesting that only the phosphorylated form of p38 interacts with PP2Calpha.
Dana-Farber Cancer Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
M
M
Takekawa
T
T
Maeda
H
H
Saito
D000595:Amino Acid Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D054648:Protein Phosphatase 2; D000071636:Protein Phosphatase 2C; D012326:RNA Splicing; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases
D016207:Cytokines; D047428:Protein Kinase Inhibitors; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; C087358:PTC1 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D000071636:Protein Phosphatase 2C