p53 dephosphorylation and p21(Cip1/Waf1) translocation correlate with caspase-3 activation in TGF-beta1-induced apoptosis of HuH-7 cells

Apoptosis. 2004 Mar;9(2):211-21. doi: 10.1023/B:APPT.0000018803.11260.02.

Abstract

The p53 tumor suppressor gene product plays an important role in the regulation of apoptosis. Transforming growth factor beta1 (TGF-beta1)-induced apoptosis in hepatic cells is associated with reduced expression of the retinoblastoma protein (pRb) and subsequent E2F-1-activated expression of apoptosis-related genes. In this study, we explored the potential role of p53 in TGF-beta1-induced apoptosis. HuH-7 human hepatoma cells were either synchronized in G1, S and G2/M phases, or treated with 1 nM TGF-beta1. The results indicated that greater than 90% of the TGF-beta1-treated cells were arrested in G1 phase of the cell cycle. This was associated with enhanced p53 dephosphorylation and p21(Cip1/Waf1) expression, which coincided with decreased Cdk2, Cdk4, and cyclin E expression, compared with synchronized G1 cells. In addition, p53 dephosphorylation coincided with caspase-3 activation, and translocation of p21(Cip1/Waf1) and p27(Kip1) into the cytoplasm, all of which were suppressed by caspase inhibition of TGF-beta1-induced apoptosis. Finally, phosphatase inhibition and pRb overexpression partially inhibited p53-mediated apoptosis. In conclusion, the results demonstrated that TGF-beta1-induced p53 dephosphorylation is associated with caspase-3 activation, and cytosolic translocation of p21(Cip1/Waf1) and p27(Kip1), resulting in decreased expression of Cdks and cyclins. Further, p53 appears to mediate TGF-beta1-induced apoptosis downstream of the pRb/E2F-1 pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / physiology*
  • Carcinoma, Hepatocellular / metabolism
  • Caspase 3
  • Caspases / metabolism*
  • Cell Cycle Proteins / metabolism*
  • Cyclin-Dependent Kinase Inhibitor p21
  • Humans
  • Liver Neoplasms / metabolism
  • Protein Transport / physiology
  • Transforming Growth Factor beta / metabolism*
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53 / metabolism*

Substances

  • CDKN1A protein, human
  • Cell Cycle Proteins
  • Cyclin-Dependent Kinase Inhibitor p21
  • Transforming Growth Factor beta
  • Tumor Suppressor Protein p53
  • CASP3 protein, human
  • Caspase 3
  • Caspases