Fernaeus Sandra, Hälldin Jonas, Bedecs Katarina, Land Tiit
Department of Neurochemistry and Neurotoxicology, Stockholm University, S-106 91 Stockholm, Sweden.
Brain Res Mol Brain Res. 2005 Feb 18;133(2):266-73. doi: 10.1016/j.molbrainres.2004.10.018.
Prion diseases are characterized by the conversion of the normal cellular prion protein PrP(C) into a pathogenic isoform, PrP(Sc). The mechanisms involved in neuronal cell death in prion diseases are largely unknown, but accumulating evidence has demonstrated oxidative impairment along with metal imbalances in scrapie-infected brains. In this study, we report changes in cellular iron metabolism in scrapie-infected mouse neuroblastoma N2a cells (ScN2a). We detected twofold lower total cellular iron and calcein-chelatable cytosolic labile iron pool (LIP) in ScN2a cells as compared to the N2a cells. We also measured in ScN2a cells significantly lower activities of iron regulatory proteins 1 and 2 (IRP1 and IRP2, respectively), regulators of cellular iron by sensing cytosolic free iron levels and controlling posttranscriptionally the expression of the major iron transport protein transferrin receptor 1 (TfR1) and the iron sequestration protein ferritin. IRP1 and IRP2 protein levels were decreased by 40% and 50%, respectively, in ScN2a cells. TfR1 protein levels were fourfold reduced and ferritin levels were threefold reduced in ScN2a cells. TfR1 and ferritin mRNA levels were significantly reduced in ScN2a cells. ScN2a cells responded normally to iron and iron chelator treatment with respect to the activities of IRP1 and IRP2, and biosynthesis of TfR1 and ferritin. However, the activities of IRP1 and IRP2, and protein levels of TfR1 and ferritin, were still significantly lower in iron-depleted ScN2a cells as compared to the N2a cells, suggesting lower need for iron in ScN2a cells. Our results demonstrate that scrapie infection leads to changes in cellular iron metabolism, affecting both total cellular and cytosolic free iron, and the activities and expression of major regulators of cellular iron homeostasis.
朊病毒疾病的特征是正常细胞朊病毒蛋白PrP(C)转变为致病异构体PrP(Sc)。朊病毒疾病中神经元细胞死亡所涉及的机制在很大程度上尚不清楚，但越来越多的证据表明，在感染羊瘙痒病的大脑中存在氧化损伤以及金属失衡。在本研究中，我们报告了感染羊瘙痒病的小鼠神经母细胞瘤N2a细胞（ScN2a）中细胞铁代谢的变化。与N2a细胞相比，我们检测到ScN2a细胞中的总细胞铁和钙黄绿素可螯合的胞质不稳定铁池（LIP）降低了两倍。我们还测量到ScN2a细胞中铁调节蛋白1和2（分别为IRP1和IRP2）的活性显著降低，这两种蛋白通过感知胞质游离铁水平并转录后控制主要铁转运蛋白转铁蛋白受体1（TfR1）和铁螯合蛋白铁蛋白的表达来调节细胞铁。在ScN2a细胞中，IRP1和IRP2蛋白水平分别降低了40%和50%。ScN2a细胞中的TfR1蛋白水平降低了四倍，铁蛋白水平降低了三倍。ScN2a细胞中的TfR1和铁蛋白mRNA水平显著降低。ScN2a细胞在IRP1和IRP2的活性以及TfR1和铁蛋白的生物合成方面对铁和铁螯合剂处理反应正常。然而，与N2a细胞相比，缺铁的ScN2a细胞中IRP1和IRP2的活性以及TfR1和铁蛋白的蛋白水平仍然显著较低，这表明ScN2a细胞对铁的需求较低。我们的结果表明，羊瘙痒病感染导致细胞铁代谢发生变化，影响总细胞铁和胞质游离铁，以及细胞铁稳态主要调节因子的活性和表达。
