[Analysis of the iron-related proteins during proliferation and differentiational change of human hepatoblastoma cells (HepG2)].

The modulation of cellular iron metabolism depends on the expression of ferritin and transferrin receptor (TfR). These proteins are regulated post-transcriptionally by interaction of specific sequences, termed iron responsive elements (IRE) which are located in the 5' untranslated region (UTR) of ferritin mRNA and 3'UTR of TfR mRNA and a specific cytosolic protein, termed iron responsive element-binding protein (IRE-BP). The liver plays an important role in iron metabolism as a major organ of iron storage. In hepatocytes iron is taken up in the form of transferrin and intercellular iron levels are regulated by IRE/IRE-BP interaction. In spite of the important role of IRE/IRE-BP interaction, the role of it for proliferation and differentiational change in hepatoma cells is not well known. In this study, the author has investigated IRE/IRE-BP interaction and its target protein expression during proliferation and differentiational change of human hepatoblastoma cells (HepG2). This study revealed that the binding activity of IRE-BP to IRE was increased when HepG2 cells were cultured with an iron-chelating agent, deferoxamine (4.5 microM), and it was decreased when cultured with transferrin (100 micrograms/ml) during both proliferation and differentiational change induced by sodium butyrate. Also, the change of TfR expression was correlated with that of IRE-BP. These findings suggest that IRE/IRE-BP interaction may play an important role in the expression of TfR and cellular iron metabolism during proliferation and differentiational change of HepG2 cells.