Hypoxia alters iron-regulatory protein-1 binding capacity and modulates cellular iron homeostasis in human hepatoma and erythroleukemia cells

被引:77
作者
Toth, I [1 ]
Yuan, LP [1 ]
Rogers, JT [1 ]
Boyce, H [1 ]
Bridges, KR [1 ]
机构
[1] Harvard Univ, Brigham & Womens Hosp, Sch Med, Dept Med,Hematol Div,Joint Ctr Sickle Cell & Thal, Boston, MA 02115 USA
关键词
D O I
10.1074/jbc.274.7.4467
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Ferritin and transferrin receptor expression is posttranscriptionally regulated by a conserved mRNA sequence termed the iron-responsive element (IRE), to which a transacting protein called the iron-regulatory protein (IRP) is bound. Our data demonstrate that hypoxia powerfully enhances IRE/IRP-1 binding in human cell lines. Using the human hepatoma cell line Hep3B as a model, we found that 16 h in a 1% oxygen atmosphere markedly increases IRE/IRP-1 binding as assessed by electromobility shift assay. Hypoxia also decreased cytosolic aconitase activity. The hypoxia-enhanced IRE/IRP-1 binding stabilized the transferrin receptor message, increased the cellular mRNA content by over 10-fold, and doubled surface receptor expression. Simultaneously, hypoxia suppressed ferritin message translation. Hypoxia's effect was most strikingly depicted by the absence of ferritin synthesis in cells challenged with inorganic iron. Our results contrast with previously reported data (Hanson, E. S., and Leibold, E. A. (1998) J. Biol. Chem, 273, 7588-7593) in which a 3% oxygen atmosphere reduced IRE/IRP-1 binding in rat hepatoma cells. We discuss some possible reasons for the differences. In aggregate with other investigations involving responses to hypoxia, iron, or nitric oxide, our data indicate that cellular iron metabolic responses are complex and that IRE/IRP-1 interactions vary between cell lines and perhaps between species.
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页码:4467 / 4473
页数:7
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