Gross C N, Irrinki A, Feder J N, Enns C A
Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland, Oregon 97201-3098, USA.
J Biol Chem. 1998 Aug 21;273(34):22068-74. doi: 10.1074/jbc.273.34.22068.
The mechanism by which a novel major histocompatibility complex class I protein, HFE, regulates iron uptake into the body is not known. HFE is the product of the gene that is mutated in >80% of hereditary hemochromatosis patients. It was recently found to coprecipitate with the transferrin receptor (Feder, J. N., Penny, D. M., Irrinki, A., Lee, V. K., Lebron, J. A., Watson, N., Tsuchihashi, Z., Sigal, E., Bjorkman, P. J., and Schatzman, R. C. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 1472-1477; Parkkila, S., Waheed, A., Britton, R. S., Bacon, B. R., Zhou, X. Y., Tomatsu, S., Fleming, R.E. , and Sly, W. S. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 13198-13202) and to decrease the affinity of transferrin for the transferrin receptor (Feder et al.). In this study, HeLa cells were transfected with HFE under the control of the tetracycline-repressible promoter. We demonstrate that HFE and the transferrin receptor are capable of associating with each other within 30 min of their synthesis with pulse-chase experiments. HFE and the transferrin receptor co-immunoprecipitate throughout the biosynthetic pathway. Excess HFE is rapidly degraded, whereas the HFE-transferrin receptor complex is stable. Immunofluorescence experiments indicate that they also endocytose into transferrin-positive compartments. Combined, these results suggest a role for the transferrin receptor in HFE trafficking. Cells expressing HFE have modestly increased levels of transferrin receptor and drastically reduced levels of ferritin. These results implicate HFE further in the modulation of iron levels in the cell.
一种新型的主要组织相容性复合体I类蛋白HFE调节铁摄入体内的机制尚不清楚。HFE是在超过80%的遗传性血色素沉着症患者中发生突变的基因的产物。最近发现它能与转铁蛋白受体共沉淀（费德，J.N.，彭尼，D.M.，伊林基，A.，李，V.K.，勒布朗，J.A.，沃森，N.，土桥，Z.，西加尔，E.，比约克曼，P.J.，和沙茨曼，R.C.（1998年）《美国国家科学院院刊》95，1472 - 1477；帕尔基拉，S.，瓦希德，A.，布里顿，R.S.，培根，B.R.，周，X.Y.，户松，S.，弗莱明，R.E.，和斯利，W.S.（1997年）《美国国家科学院院刊》94，13198 - 13202），并降低转铁蛋白对转铁蛋白受体的亲和力（费德等人）。在本研究中，用四环素可抑制启动子控制下的HFE转染HeLa细胞。我们通过脉冲追踪实验证明，HFE和转铁蛋白受体在合成后30分钟内能够相互结合。HFE和转铁蛋白受体在整个生物合成途径中共免疫沉淀。过量的HFE迅速降解，而HFE - 转铁蛋白受体复合物是稳定的。免疫荧光实验表明它们也会内吞进入转铁蛋白阳性区室。综合这些结果表明转铁蛋白受体在HFE运输中起作用。表达HFE的细胞中转铁蛋白受体水平适度增加，铁蛋白水平大幅降低。这些结果进一步表明HFE参与细胞内铁水平的调节。
