Protein phosphatase-2A is a target of epigallocatechin-3-gallate and modulates p53-bak apoptotic pathway

Jichao Qin, He Ge Chen, Qin Yan, Mi Deng, Jinping Liu, Stephan Doerge, Weiya Ma, Zigang Dong, David Wan Cheng Li

Research output: Contribution to journalArticle

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Abstract

(-)-Epigallocatechin-3-gallate (EGCG) is a well-known chemoprevention factor. Recent studies have revealed that EGCG triggers cancer cells undergoing apoptosis through p53-dependent pathway. How EGCG activates p53-dependent apoptosis is not fully understood. In the present study using JB6 cell as a model system, we have shown that EGCG can negatively regulate protein serine/threonine phosphatase-2A (PP-2A) to positively regulate p53-dependent apoptosis. First, EGCG at physiologic levels down-regulates PP-2A at the protein and enzyme activity levels. Second, EGCG induces apoptosis of JB6 cells, which is associated with hyperphosphorylation of p53 and up-regulation of the proapoptotic gene, Bak. DNA sequence analysis, gel mobility shifting, chromatin immunoprecipitation, and reporter gene activity assays revealed that p53 directly controls Bak in JB6 cells. Knockdown of p53 and Bak expression with RNAi substantially inhibits EGCG-induced apoptosis. Third, PP-2A directly interacts with p53 and dephosphorylates p53 at Ser-15 in vitro and in vivo. Fourth, overexpression of the catalytic subunit for PP-2A down-regulates p53 phosphorylation at Ser15, attenuates expression of the downstream proapoptotic gene, Bak, and antagonizes EGCG-induced apoptosis. Inhibition of PP-2A activity enhances p53 phosphorylation at Ser-15 and up-regulates Bak expression to promote EGCG-induced apoptosis. Finally, in the p53-/- H1299 and p53+/+ H1080 cells, EGCG down-regulates PP-2A similarly but induces differential apoptosis. In summary, our results show that (a) PP-2A directly dephosphorylates p53 at Ser-15; (b) P53 directly controls Bak expression; and (c) EGCG negatively regulates PP-2A. Together, our results show that EGCG-mediated negative regulation of PP-2A is an important molecular event for the activation of p53-dependent apoptosis during its chemoprevention.

Original languageEnglish (US)
Pages (from-to)4150-4162
Number of pages13
JournalCancer Research
Volume68
Issue number11
DOIs
StatePublished - Jun 1 2008

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Protein Phosphatase 2
Phosphoric Monoester Hydrolases
Apoptosis
Down-Regulation
Chemoprevention
epigallocatechin gallate
Up-Regulation
Phosphorylation
Chromatin Immunoprecipitation
Phosphoprotein Phosphatases
RNA Interference
DNA Sequence Analysis
Reporter Genes
Genes
Catalytic Domain

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

Cite this

Qin, J., Chen, H. G., Yan, Q., Deng, M., Liu, J., Doerge, S., ... Li, D. W. C. (2008). Protein phosphatase-2A is a target of epigallocatechin-3-gallate and modulates p53-bak apoptotic pathway. Cancer Research, 68(11), 4150-4162. https://doi.org/10.1158/0008-5472.CAN-08-0839

Protein phosphatase-2A is a target of epigallocatechin-3-gallate and modulates p53-bak apoptotic pathway. / Qin, Jichao; Chen, He Ge; Yan, Qin; Deng, Mi; Liu, Jinping; Doerge, Stephan; Ma, Weiya; Dong, Zigang; Li, David Wan Cheng.

In: Cancer Research, Vol. 68, No. 11, 01.06.2008, p. 4150-4162.

Research output: Contribution to journalArticle

Qin, J, Chen, HG, Yan, Q, Deng, M, Liu, J, Doerge, S, Ma, W, Dong, Z & Li, DWC 2008, 'Protein phosphatase-2A is a target of epigallocatechin-3-gallate and modulates p53-bak apoptotic pathway', Cancer Research, vol. 68, no. 11, pp. 4150-4162. https://doi.org/10.1158/0008-5472.CAN-08-0839
Qin, Jichao ; Chen, He Ge ; Yan, Qin ; Deng, Mi ; Liu, Jinping ; Doerge, Stephan ; Ma, Weiya ; Dong, Zigang ; Li, David Wan Cheng. / Protein phosphatase-2A is a target of epigallocatechin-3-gallate and modulates p53-bak apoptotic pathway. In: Cancer Research. 2008 ; Vol. 68, No. 11. pp. 4150-4162.
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AU - Doerge, Stephan

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