Pinto Jorge P, Ramos Pedro, de Almeida Sérgio F, Oliveira Susana, Breda Laura, Michalak Marek, Porto Graça, Rivella Stefano, de Sousa Maria
Iron Genes and Immune System, Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal.
Free Radic Biol Med. 2008 Jan 1;44(1):99-108. doi: 10.1016/j.freeradbiomed.2007.09.014. Epub 2007 Oct 4.
HFE gene mutations are associated with over 80% of cases of hereditary hemochromatosis (HH), an iron-overload disease in which the liver is the most frequently affected organ. Research on HFE has traditionally focused on its interaction with the transferrin receptor. More recent studies have suggested a more complex function for this nonclassical MHC-I protein. The aim of this study was to examine how HFE and its two most common mutations affect the expression of selected genes in a hepatocyte-like cell line. Gene expression was analyzed in HepG2 cells overexpressing wild-type and mutant HFE. The effect of HFE in iron import and oxidative stress levels was assessed. Unfolded protein response (UPR)-activated gene expression was analyzed in peripheral blood mononuclear cells from characterized HH patients. C282Y HFE down-regulated hepcidin and enhanced calreticulin mRNA expression. Calreticulin levels correlated with intracellular iron increase and were associated with protection from oxidative stress. In C282Y(+/+) patients calreticulin levels correlated with the expression of the UPR marker BiP and showed a negative association with the number of hereditary hemochromatosis clinical manifestations. The data show that expression of C282Y HFE triggers a stress-protective response in HepG2 cells and suggest a role for calreticulin as a modifier of the clinical expression of HH.
HFE基因突变与超过80%的遗传性血色素沉着症（HH）病例相关，HH是一种铁过载疾病，其中肝脏是最常受影响的器官。对HFE的研究传统上集中在其与转铁蛋白受体的相互作用上。最近的研究表明，这种非经典的MHC-I蛋白具有更复杂的功能。本研究的目的是研究HFE及其两种最常见的突变如何影响肝细胞样细胞系中选定基因的表达。在过表达野生型和突变型HFE的HepG2细胞中分析基因表达。评估了HFE对铁摄取和氧化应激水平的影响。在已确诊的HH患者的外周血单核细胞中分析了未折叠蛋白反应（UPR）激活的基因表达。C282Y HFE下调了铁调素并增强了钙网蛋白mRNA的表达。钙网蛋白水平与细胞内铁增加相关，并与抗氧化应激保护有关。在C282Y（+/+）患者中，钙网蛋白水平与UPR标志物BiP的表达相关，并与遗传性血色素沉着症临床表现的数量呈负相关。数据表明，C282Y HFE的表达在HepG2细胞中触发了应激保护反应，并提示钙网蛋白作为HH临床表达调节剂的作用。
