Bagu Edward T, Layoun A, Calvé A, Santos M M
Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Institut du Cancer de Montréal, (ICM), University of Montreal, Pavillon De Sève Porte Y-5625, 2099 rue Alexandre De Sève, Montreal, QC, H2L 4M1, Canada,
Biometals. 2013 Dec;26(6):1051-65. doi: 10.1007/s10534-013-9683-6. Epub 2013 Nov 1.
Hepcidin is an antimicrobial peptide hormone that plays a central role in the metabolism of iron and its expression in the liver can be induced through two major pathways: the inflammatory pathway, mainly via IL-6; and the iron-sensing pathway, mediated by BMP-6. GATA-proteins are group of evolutionary conserved transcriptional regulators that bind to the consensus motif-WGATAR-in the promoter region. In hepatoma cells, GATA-proteins 4 and 6 in conjunction with the co-factor friend of GATA (FOG) were shown to modulate the transcription of HAMP. However, it is unclear as to which of the GATA-proteins drive the expression of HAMP in vivo. In this study, using in vitro and in vivo approaches, we investigated the relevance of GATA and FOG proteins in the expression of hepcidin following treatment with IL-6 and BMP-6. We found that treatment of Huh7 cells with either IL-6 or BMP-6 increased the HAMP promoter activity. The HAMP promoter activity following treatment with IL-6 or BMP-6 was further increased by co-transfection of the promoter with GATA proteins 4 and 6. However, co-transfection of the HAMP promoter with FOG proteins 1 or 2 repressed the promoter response to treatments with either IL-6 or BMP-6. The effects of both GATA and FOG proteins on the promoter activity in response to IL-6 or BMP-6 treatment were abrogated by mutation of the GATA response element-TTATCT-in the HAMP promoter region -103/-98. In vivo, treatment of mice with lipopolysaccharide led to a transient increase of Gata-6 expression in the liver that was positively correlated with the expression of hepcidin. Our results indicate that during inflammation GATA-6 is up-regulated in concert with hepcidin while GATA-4 and FOG (1 and 2) are repressed.
铁调素是一种抗菌肽激素，在铁代谢中起核心作用，其在肝脏中的表达可通过两条主要途径诱导：炎症途径，主要通过白细胞介素-6；以及铁感应途径，由骨形态发生蛋白-6介导。GATA蛋白是一组进化保守的转录调节因子，它们与启动子区域的共有基序-WGATAR-结合。在肝癌细胞中，GATA蛋白4和6与GATA辅因子（FOG）共同作用可调节铁调素抗菌肽（HAMP）的转录。然而，尚不清楚哪种GATA蛋白在体内驱动HAMP的表达。在本研究中，我们采用体外和体内方法，研究了GATA和FOG蛋白在白细胞介素-6和骨形态发生蛋白-6处理后铁调素表达中的相关性。我们发现，用白细胞介素-6或骨形态发生蛋白-6处理Huh7细胞可增加HAMP启动子活性。用GATA蛋白4和6共转染启动子后，白细胞介素-6或骨形态发生蛋白-6处理后的HAMP启动子活性进一步增加。然而，用FOG蛋白1或2共转染HAMP启动子可抑制启动子对白细胞介素-6或骨形态发生蛋白-6处理的反应。通过突变HAMP启动子区域-103/-98中的GATA反应元件-TTATCT，可消除GATA和FOG蛋白对白细胞介素-6或骨形态发生蛋白-6处理后启动子活性的影响。在体内，用脂多糖处理小鼠导致肝脏中Gata-6表达短暂增加，这与铁调素的表达呈正相关。我们的结果表明，在炎症过程中，GATA-6与铁调素协同上调，而GATA-4和FOG（1和2）受到抑制。
