Gao Junwei, Zhao Ningning, Knutson Mitchell D, Enns Caroline A
Department of Cell and Developmental Biology, Oregon Health and Science University, 3181 Sam Jackson Park Road, Portland, OR 97239, USA.
J Biol Chem. 2008 Aug 1;283(31):21462-8. doi: 10.1074/jbc.M803150200. Epub 2008 Jun 4.
Lack of functional hereditary hemochromatosis protein, HFE, causes iron overload predominantly in hepatocytes, the major site of HFE expression in the liver. In this study, we investigated the role of HFE in the regulation of both transferrin-bound iron (TBI) and non-transferrin-bound iron (NTBI) uptake in HepG2 cells, a human hepatoma cell line. Expression of HFE decreased both TBI and NTBI uptake. It also resulted in a decrease in the protein levels of Zip14 with no evident change in the mRNA level of Zip14. Zip14 (Slc39a14) is a metal transporter that mediates NTBI into cells (Liuzzi, J. P., Aydemir, F., Nam, H., Knutson, M. D., and Cousins, R. J. (2006) Proc. Natl. Acad. Sci. U. S. A. 103, 13612-13617). Knockdown of Zip14 with siRNA abolished the effect of HFE on NTBI uptake. To determine if HFE had a similar effect on Zip14 in another cell line, HeLa cells expressing HFE under the tetracycline-repressible promoter were transfected with Zip14. As in HepG2 cells, HFE expression inhibited NTBI uptake by approximately 50% and decreased Zip14 protein levels. Further analysis of protein turnover indicated that the half-life of Zip14 is lower in cells that express HFE. These results suggest that HFE decreases the stability of Zip14 and therefore reduces the iron loading in HepG2 cells.
功能性遗传性血色素沉着症蛋白HFE的缺失主要导致肝细胞中铁过载，肝细胞是肝脏中HFE表达的主要部位。在本研究中，我们调查了HFE在人肝癌细胞系HepG2细胞中对转铁蛋白结合铁（TBI）和非转铁蛋白结合铁（NTBI）摄取调节中的作用。HFE的表达降低了TBI和NTBI的摄取。它还导致Zip14蛋白水平下降，而Zip14的mRNA水平没有明显变化。Zip14（Slc39a14）是一种金属转运蛋白，可将NTBI介导进入细胞（Liuzzi，J.P.，Aydemir，F.，Nam，H.，Knutson，M.D.，和Cousins，R.J.（2006年）美国国家科学院院刊103，13612 - 13617）。用小干扰RNA（siRNA）敲低Zip14消除了HFE对NTBI摄取的影响。为了确定HFE在另一种细胞系中对Zip14是否有类似作用，将在四环素可抑制启动子下表达HFE的HeLa细胞转染Zip14。与在HepG2细胞中一样，HFE的表达使NTBI摄取抑制约50%并降低Zip14蛋白水平。对蛋白质周转的进一步分析表明，在表达HFE的细胞中Zip14的半衰期较短。这些结果表明，HFE降低了Zip14的稳定性，从而减少了HepG2细胞中的铁负荷。
