TY - JOUR
T1 - Effects of interferon-γ and lipopolysaccharide on macrophage iron metabolism are mediated by nitric oxide-induced degradation of iron regulatory protein 2
AU - Kim, Sangwon
AU - Ponka, Prem
PY - 2000/3/3
Y1 - 2000/3/3
N2 - Iron regulatory proteins (IRP-1 and IRP-2) control the synthesis of transferrin receptors (TfR) and ferritin by binding to iron-responsive elements, which are located in the 3'-untranslated region and the 5'- untranslated region of their respective mRNAs. Cellular iron levels affect binding of IRPs to iron-responsive elements and consequently expression of TfR and ferritin. Moreover, NO., a redox species of nitric oxide that interacts primarily with iron, can activate IRP-1 RNA binding activity resulting- in an increase in TfR mRNA levels. Recently we found that treatment of RAW 264.7 cells (a murine macrophage cell line) with NO+ (nitrosonium ion, which causes S-nitrosylation of thiol groups) resulted in a rapid decrease in RNA binding of IRP-2 followed by IRP-2 degradation, and these changes were associated with a decrease in TfR mRNA levels (Kim, S., and Ponka, P. (1999) J. Biol. Chem. 274, 33035-33042). In this study, we demonstrated that stimulation of RAW 264.7 cells with lipopolysaccharide (LPS) and interferon-γ (IFN-γ) increased IRP-1 binding activity, whereas RNA binding of IRP-2 decreased and was followed by a degradation of this protein. Moreover, the decrease of IRP-2 binding/protein levels was associated with a decrease in TfR mRNA levels in LPS/IFN-γ-treated cells, and these changes were prevented by inhibitors of inducible nitric oxide synthase. Furthermore, LPS/IFN-γ-stimulated RAW 264.7 cells showed increased rates of ferritin synthesis. These results suggest that NO+-mediated degradation of IRP-2 plays a major role in iron metabolism during inflammation.
AB - Iron regulatory proteins (IRP-1 and IRP-2) control the synthesis of transferrin receptors (TfR) and ferritin by binding to iron-responsive elements, which are located in the 3'-untranslated region and the 5'- untranslated region of their respective mRNAs. Cellular iron levels affect binding of IRPs to iron-responsive elements and consequently expression of TfR and ferritin. Moreover, NO., a redox species of nitric oxide that interacts primarily with iron, can activate IRP-1 RNA binding activity resulting- in an increase in TfR mRNA levels. Recently we found that treatment of RAW 264.7 cells (a murine macrophage cell line) with NO+ (nitrosonium ion, which causes S-nitrosylation of thiol groups) resulted in a rapid decrease in RNA binding of IRP-2 followed by IRP-2 degradation, and these changes were associated with a decrease in TfR mRNA levels (Kim, S., and Ponka, P. (1999) J. Biol. Chem. 274, 33035-33042). In this study, we demonstrated that stimulation of RAW 264.7 cells with lipopolysaccharide (LPS) and interferon-γ (IFN-γ) increased IRP-1 binding activity, whereas RNA binding of IRP-2 decreased and was followed by a degradation of this protein. Moreover, the decrease of IRP-2 binding/protein levels was associated with a decrease in TfR mRNA levels in LPS/IFN-γ-treated cells, and these changes were prevented by inhibitors of inducible nitric oxide synthase. Furthermore, LPS/IFN-γ-stimulated RAW 264.7 cells showed increased rates of ferritin synthesis. These results suggest that NO+-mediated degradation of IRP-2 plays a major role in iron metabolism during inflammation.
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U2 - 10.1074/jbc.275.9.6220
DO - 10.1074/jbc.275.9.6220
M3 - Article
C2 - 10692416
AN - SCOPUS:0034089867
SN - 0021-9258
VL - 275
SP - 6220
EP - 6226
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 9
ER -