Activation of p38 mitogen-activated protein kinase and mitochondrial Ca2+-mediated oxidative stress are essential for the enhanced expression of grp78 induced by the protein phosphatase inhibitors okadaic acid and calyculin A

Kuang Den Chen, Ming Tsong Lai, Jun Hung Cho, Liuh Yow Chen, Yiu Kay Lai*

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

30 Scopus citations

Abstract

We have reported that treatment with okadaic acid, a potent protein phosphatase inhibitor, has the ability to enhance the synthesis of the 78-kDa glucose-regulated protein (GRP78). This article reports our investigation of another protein phosphatase inhibitor, calyculin A, demonstrating the signaling pathways elicited by the protein phosphatase inhibitors that lead to the induction of grp78. Our data showed that the induction process is abolished by SB203580, a specific inhibitor of p38 mitogen-activated protein kinase (p38(MAPK)). Phosphorylation-activation of p38(MAPK) in the treated cells was indicated by its own phosphorylation, as shown by double Western blotting analyses and directly confirmed by the in vitro kinase assay using MAPK-activated protein kinase-2, a well-known downstream effector of p38(MAPK), as a substrate. The involvement of p38(MAPK) in this process is further substantiated by using transient transfection assays with a plasmid, pGRP78-Luc, which contains a 0.72-kbp stretch of the grp78 promoter. By exploiting the same transfection assay, we demonstrated that the up- regulation of the grp78 promoter by the protein phosphatase inhibitors is suppressed in the presence of the cytoplasmic calcium chelator bis(aminophenoxy)ethane N,N'-tetraacetic acid, the mitochondria calcium uniporter inhibitor ruthenium red as well as the antioxidants N-acetyl cysteine and pyrrolidinedithiocarbamate. Taken together, our results lead us to conclude that treatment with the protein phosphatase inhibitors would activate the signaling pathways involving p38(MAPK) and mitochondrial calcium-mediated oxidative stress and that these pathways must act in concert in order to confer the induction of grp78 by okadaic acid and calyculin. (C) 2000 Wiley-Liss, Inc.

Original languageEnglish
Pages (from-to)585-595
Number of pages11
JournalJournal of Cellular Biochemistry
Volume76
Issue number4
DOIs
StatePublished - 2000
Externally publishedYes

Keywords

  • Glucose-regulated protein
  • Mitochondrial calcium
  • Oxidative stress
  • Protein phosphatase
  • p38 mitogen-activated protein kinase

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