Numerous proteins in Mammalian cells are prone to iron-dependent oxidation and proteasomal degradation.
The mechanisms that underlie iron toxicity in cells and organisms are poorly understood. Previous studies of regulation of the cytosolic iron sensor, iron-regulatory protein 2 (IRP2), indicate that iron-dependent oxidation triggers ubiquitination and proteasomal degradation of IRP2. To determine if oxidization by iron is involved in degradation of other proteins, we have used a carbonyl assay to identify oxidized proteins in lysates from RD4 cells treated with either an iron source or iron chelator. Protein lysates from iron-loaded or iron-depleted cells were resolved on two-dimensional gels and these iron manipulations were also repeated in the presence of proteasomal inhibitors. Eleven abundant proteins were identified as prone to iron-dependent oxidation and subsequent proteasomal degradation. These proteins included two putative iron-binding proteins, hNFU1 and calreticulin; two proteins involved in metabolism of hydrogen peroxide, peroxiredoxin 2 and superoxide dismutase 1; and several proteins identified in inclusions in neurodegenerative diseases, including HSP27, UCHL1, actin and tropomyosin. Our results indicate that cells can recognize and selectively eliminate iron-dependently oxidized proteins, but unlike IRP2, levels of these proteins do not significantly decrease in iron-treated cells. As iron overload is a feature of many human neurological diseases, further characterization of the process of degradation of iron-dependently oxidized proteins may yield insights into mechanisms of human disease.
Drake
Steven K
SK
National Institute of Child Health and Human Development, Bethesda, MD, USA.
Bourdon
Emmanuel
E
Wehr
Nancy B
NB
Levine
Rodney L
RL
Backlund
Peter S
PS
Yergey
Alfred L
AL
Rouault
Tracey A
TA
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D015153:Blotting, Western; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D005290:Ferric Compounds / Q000494:pharmacology; D006801:Humans; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000032:analysis / Q000187:drug effects / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D015853:Cysteine Proteinase Inhibitors; D005290:Ferric Compounds; D007502:Iron Chelating Agents; D009097:Multienzyme Complexes; D011506:Proteins; D000644:Quaternary Ammonium Compounds; C067713:lactacystin; D007501:Iron; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D003676:Deferoxamine; C013531:ferric ammonium citrate; D000111:Acetylcysteine