RKIP downregulation induces the HBx-mediated Raf-1 mitochondrial translocation

J Microbiol Biotechnol. 2011 May;21(5):525-8. doi: 10.4014/jmb.1012.12023.

Abstract

The Raf-1 kinase inhibitory protein (RKIP) can regulate multiple key signaling pathways. Specifically, RKIP binds to Raf-1 kinase and inhibits the Ras-Raf-1-MEK1/2- ERK1/2 pathway. Additionally, Raf-1 has been shown to translocate to mitochondria and thereby protect cells from stress-mediated apoptosis. Recently, HBx was found to stimulate the mitochondrial translocation of Raf-1, contributing to the anti-apoptotic effect. We found that RKIP was downregulated during HBx-mediated hepatocarcinogenesis. In this study, we show that RKIP bound to Raf-1 and consequently inhibited the translocation of Raf-1 into mitochondria. This promoted the apoptosis of cells treated with apoptotic stimulus. Thus, the downregulation of RKIP increased the level of free Raf-1 and thereby elevated the mitochondrial translocation of Raf-1 during HBx-mediated hepatocarcinogenesis. The elevated Raf-1 mitochondrial translocation induced the increased anti-apoptotic effect and subsequently promoted HBx-mediated hepatocarcinogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carcinoma, Hepatocellular / enzymology*
  • Carcinoma, Hepatocellular / genetics
  • Carcinoma, Hepatocellular / pathology
  • Carcinoma, Hepatocellular / virology
  • Cell Line, Tumor
  • Down-Regulation*
  • Hepatitis B virus / genetics
  • Hepatitis B virus / metabolism*
  • Humans
  • Liver Neoplasms / enzymology*
  • Liver Neoplasms / genetics
  • Liver Neoplasms / pathology
  • Liver Neoplasms / virology
  • Mitochondria / enzymology*
  • Mitochondria / genetics
  • Phosphatidylethanolamine Binding Protein / genetics
  • Phosphatidylethanolamine Binding Protein / metabolism*
  • Protein Transport
  • Proto-Oncogene Proteins c-raf / genetics
  • Proto-Oncogene Proteins c-raf / metabolism*
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Viral Regulatory and Accessory Proteins

Substances

  • PEBP1 protein, human
  • Phosphatidylethanolamine Binding Protein
  • Trans-Activators
  • Viral Regulatory and Accessory Proteins
  • hepatitis B virus X protein
  • Proto-Oncogene Proteins c-raf