Phosphorylation of Ser-446 determines stability of MKP-7.
MAPK cascades can be negatively regulated by members of the MAPK phosphatase (MKP) family. However, how MKP activity is regulated is not well characterized. MKP-7, a JNK-specific phosphatase, possesses a unique COOH-terminal stretch (CTS) in addition to domains conserved among MKP family members. The CTS contains several motifs such as a nuclear localization signal, a nuclear export signal, PEST sequences, and a serine residue (Ser-446) that can be phosphorylated by activated ERK, suggesting an important regulatory role(s).(35)S-pulse labeling experiments indicate that the half-life of MKP-7 is 1.5 h, a period significantly elongated by deleting the CTS. We also show that overexpressed MKP-7 is polyubiquitinated when co-expressed with ubiquitin and that proteasome inhibitors markedly inhibit MKP-7 degradation. We also determined that MKP-7 phosphorylated at Ser-446 has a longer half-life than unphosphorylated form of the wild type protein, as does a phospho-mimic mutant of MKP-7. These results indicate that activation of the ERK pathway strongly blocks JNK activation through stabilization of MKP-7 mediated by phosphorylation.
Katagiri
Chiaki
C
Division of Biochemical Oncology and Immunology, Institute for Genetic Medicine, Hokkaido University, Kita-15, Nishi-7, Kita-ku, Sapporo 060-0815, Japan.
Masuda
Kouhei
K
Urano
Takeshi
T
Yamashita
Katsumi
K
Araki
Yoshio
Y
Kikuchi
Kunimi
K
Shima
Hiroshi
H
D020816:Amino Acid Motifs; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D054637:Dual-Specificity Phosphatases; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D017353:Gene Deletion; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D054639:Mitogen-Activated Protein Kinase Phosphatases; D008954:Models, Biological; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry* / Q000378:metabolism; D012694:Serine / Q000737:chemistry*; D013997:Time Factors; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism
D025801:Ubiquitin; D012694:Serine; D004247:DNA; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D054639:Mitogen-Activated Protein Kinase Phosphatases; C439065:DUSP16 protein, human; D054637:Dual-Specificity Phosphatases; D017027:Protein Tyrosine Phosphatases