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Published on: December 27, 2016

Involvement of glycogen synthase kinase-3β in arsenic trioxide-induced p21 expression

Huei-Sheng Huang1, Zi-Miao Liu, Ya-Ling Cheng

  • 1Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan. huanghs@mail.ncku.edu.tw

Toxicological Sciences : an Official Journal of the Society of Toxicology
|February 1, 2011
PubMed

Insights

Arsenic trioxide (ATO) enhances p21 expression by inhibiting GSK-3β, leading to c-Jun dephosphorylation and increased binding to the p21 promoter, ultimately causing cell death.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Pharmacology

Background:

  • Arsenic trioxide (ATO) treats leukemia and solid tumors by inducing cell cycle arrest or apoptosis.
  • Previous studies suggest c-Jun regulates p21(WAF1/CIP1) (p21) expression in response to ATO.
  • Glycogen synthase kinase-3β (GSK-3β) phosphorylation of c-Jun reduces its stability and DNA binding, and promotes p21 degradation.

Purpose of the Study:

  • To elucidate the mechanism by which ATO regulates c-Jun binding to the p21 promoter.
  • To investigate the hypothesis that ATO-induced p21 expression occurs via GSK-3β inhibition.

Main Methods:

  • DNA affinity precipitation assay to assess c-Jun binding to the p21 promoter.
  • Western blotting to detect protein phosphorylation and expression levels (c-Jun, p21, GSK-3β).
  • Use of GSK-3β inhibitors (ATO, LiCl) and constitutively active/inactive GSK-3β mutants.
  • Cycloheximide chase assay to determine p21 protein stability.
  • ERK and PI3K/Akt pathway inhibitors to investigate signaling pathways.

Main Results:

  • ATO dephosphorylated c-Jun at Ser243, enhancing its binding to the p21 promoter and increasing p21 expression.
  • ATO and LiCl induced GSK-3β(Ser9) phosphorylation and p21 expression in a time- and dose-dependent manner.
  • ATO increased p21 protein stability, unlike LiCl.
  • ATO-induced GSK-3β phosphorylation involved the ERK pathway, not PI3K/Akt.

Conclusions:

  • ATO inhibits GSK-3β activity, leading to c-Jun dephosphorylation and increased p21 expression.
  • The ERK pathway mediates ATO-induced GSK-3β inhibition.
  • This mechanism contributes to ATO-induced cell death in cancer treatment.

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