1. Cysteine oxidation regulates the RNA-binding activity of iron regulatory protein 2.
- Author
-
Zumbrennen KB, Wallander ML, Romney SJ, and Leibold EA
- Subjects
- Animals, Binding Sites, Homeostasis, Humans, Mice, Oxidation-Reduction, Oxidative Stress, RNA, Messenger analysis, Antigens, CD genetics, Cysteine metabolism, Iron Regulatory Protein 2 metabolism, RNA-Binding Proteins metabolism, Receptors, Transferrin genetics
- Abstract
Iron regulatory protein 2 (IRP2) is an RNA-binding protein that regulates the posttranscriptional expression of proteins required for iron homeostasis such as ferritin and transferrin receptor 1. IRP2 RNA-binding activity is primarily regulated by iron-mediated proteasomal degradation, but studies have suggested that IRP2 RNA binding is also regulated by thiol oxidation. We generated a model of IRP2 bound to RNA and found that two cysteines (C512 and C516) are predicted to lie in the RNA-binding cleft. Site-directed mutagenesis and thiol modification show that, while IRP2 C512 and C516 do not directly interact with RNA, both cysteines are located within the RNA-binding cleft and must be unmodified/reduced for IRP2-RNA interactions. Oxidative stress induced by cellular glucose deprivation reduces the RNA-binding activity of IRP2 but not IRP2-C512S or IRP2-C516S, consistent with the formation of a disulfide bond between IRP2 C512 and C516 during oxidative stress. Decreased IRP2 RNA binding is correlated with reduced transferrin receptor 1 mRNA abundance. These studies provide insight into the structural basis for IRP2-RNA interactions and reveal an iron-independent mechanism for regulating iron homeostasis through the redox regulation of IRP2 cysteines.
- Published
- 2009
- Full Text
- View/download PDF