Bouton C, Oliveira L, Drapier J C
Section de Recherche, U 365 INSERM, Institut Curie, 26, rue d'Ulm, 75005 Paris, France.
J Biol Chem. 1998 Apr 17;273(16):9403-8. doi: 10.1074/jbc.273.16.9403.
Iron regulatory proteins (IRP1 and IRP2) are two cytoplasmic RNA-binding proteins that control iron metabolism in mammalian cells. Both IRPs bind to specific sequences called iron-responsive elements (IREs) located in the 3' or 5' untranslated regions of several mRNAs, in particular mRNA encoding ferritin and transferrin receptor. In this study, we followed in parallel the in vivo regulation of the two IRPs in physiologically stimulated macrophages. We show that stimulation of mouse RAW 264.7 macrophage-like cells increased IRP1 IRE binding activity 4-fold, whereas IRP2 activity decreased 2-fold 8 h after interferon-gamma/lipopolysaccharide treatment. Decrease in IRP2 was not due to nitric oxide (NO) production and did not require de novo protein synthesis. Our data therefore indicate that the two IRPs can be conversely regulated in response to the same stimulus. In addition, the effect of endogenously produced NO on IRP1 was further characterized in an activated macrophage/target cell system. We show that NO acts as an intercellular signal to increase IRP1 activity in adjacent cells. As the effect was detectable within 1 h and did not require de novo protein synthesis, this result supports a direct action of NO on IRP1.
铁调节蛋白（IRP1和IRP2）是两种细胞质RNA结合蛋白，它们控制哺乳动物细胞中的铁代谢。这两种IRP都与位于几种mRNA的3'或5'非翻译区的特定序列结合，这些序列称为铁反应元件（IRE），特别是编码铁蛋白和转铁蛋白受体的mRNA。在本研究中，我们在生理刺激的巨噬细胞中并行跟踪了这两种IRP的体内调节。我们发现，用干扰素-γ/脂多糖处理小鼠RAW 264.7巨噬细胞样细胞8小时后，刺激使IRP1的IRE结合活性增加了4倍，而IRP2的活性降低了2倍。IRP2的降低不是由于一氧化氮（NO）的产生，也不需要从头合成蛋白质。因此，我们的数据表明，这两种IRP可以对相同的刺激产生相反的调节。此外，在活化的巨噬细胞/靶细胞系统中进一步研究了内源性产生的NO对IRP1的影响。我们发现，NO作为一种细胞间信号，可增加相邻细胞中IRP1的活性。由于这种作用在1小时内即可检测到，且不需要从头合成蛋白质，因此该结果支持NO对IRP1的直接作用。
