Protein kinase Cdelta-mediated proteasomal degradation of MAP kinase phosphatase-1 contributes to glutamate-induced neuronal cell death.
Mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) is a dual-specificity phosphatase that is involved in the regulation of cell survival, differentiation and apoptosis through inactivating MAPKs by dephosphorylation. Here, we provide evidence for a role of MKP-1 in the glutamate-induced cell death of HT22 hippocampal cells and primary mouse cortical neurons. We suggest that, during glutamate-induced oxidative stress, protein kinase C (PKC) delta becomes activated and induces sustained activation of extracellular signal-regulated kinase 1/2 (ERK1/2) through a mechanism that involves degradation of MKP-1. Glutamate-induced activation of ERK1/2 was blocked by inhibition of PKCdelta, confirming that ERK1/2 is regulated by PKCdelta. Prolonged exposure to glutamate caused reduction in the protein level of MKP-1, which correlated with the sustained activation of ERK1/2. Furthermore, knockdown of endogenous MKP-1 by small interfering (si)RNA resulted in pronounced enhancement of ERK1/2 phosphorylation accompanied by increased cytotoxicity under glutamate exposure. In glutamate-treated cells, MKP-1 was polyubiquitylated and proteasome inhibitors markedly blocked the degradation of MKP-1. Moreover, inhibition of glutamate-induced PKCdelta activation suppressed the downregulation and ubiquitylation of MKP-1. Taken together, these results demonstrate that activation of PKCdelta triggers degradation of MKP-1 through the ubiquitin-proteasome pathway, thereby contributing to persistent activation of ERK1/2 under glutamate-induced oxidative toxicity.
Choi
Bo-Hwa
BH
System-Biodynamics NCRC, National Research Laboratory of Molecular Neurophysiology and Division of Molecular and Life Science, Pohang University of Science and Technology, Hyoja dong, San31, Pohang, 790-784, South Korea.
Hur
Eun-Mi
EM
Lee
Jong-Hee
JH
Jun
Dong-Jae
DJ
Kim
Kyong-Tai
KT
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D018929:Cell Culture Techniques; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death; D002460:Cell Line; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation / Q000187:drug effects; D018698:Glutamic Acid / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011233:Precipitin Tests; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism
D018797:Cell Cycle Proteins; D017874:Immediate-Early Proteins; D034741:RNA, Small Interfering; D018698:Glutamic Acid; D051745:Protein Kinase C-delta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse; D017027:Protein Tyrosine Phosphatases; D046988:Proteasome Endopeptidase Complex