Koorts A M, Viljoen M
Department of Physiology, School of Medicine, University of Pretoria, Pretoria, South Africa.
Arch Physiol Biochem. 2007 Apr;113(2):55-64. doi: 10.1080/13813450701422575.
Ferritin is a major iron storage protein involved in the regulation of iron availability. Each ferritin molecule comprises 24 subunits. Various combinations of H-subunits and L-subunits make up the 24-subunit protein structure and these ferritin isoforms differ in their H-subunit to L-subunit ratio, as well as in their metabolic properties. Ferritin is an acute-phase protein and its expression is up-regulated in conditions such as uncontrolled cellular proliferation, in any condition marked by excessive production of toxic oxygen radicals, and by infectious and inflammatory processes. Under such conditions ferritin up-regulation is predominantly stimulated by increased reactive oxygen radical production and by cytokines. The major function of ferritin in these conditions is to reduce the bio-availability of iron in order to stem uncontrolled cellular proliferation and excessive production of reactive oxygen radicals. Ferritin is not, however, indiscriminately up-regulated in these conditions as a marked shift towards a predominance in H-subunit rich ferritins occurs. Preliminary indications are that, while the L-subunit primarily fulfils the conventional iron storage role, the H-subunit functions primarily as rapid regulator of iron availability, and perhaps indirectly as regulator of other cellular processes. It is suggested that the optimum differential expression of the two subunits differ for different cells and under different conditions and that the expression of appropriate isoferritins offers protection against uncontrolled cellular proliferation, oxidative stress and against side effects of infectious and inflammatory conditions.
铁蛋白是一种主要的铁储存蛋白，参与铁可用性的调节。每个铁蛋白分子由24个亚基组成。H亚基和L亚基的各种组合构成了24亚基的蛋白质结构，这些铁蛋白异构体在H亚基与L亚基的比例以及代谢特性方面存在差异。铁蛋白是一种急性期蛋白，在诸如不受控制的细胞增殖、任何以有毒氧自由基过度产生为特征的条件以及感染和炎症过程等情况下，其表达会上调。在这些条件下，铁蛋白上调主要受活性氧自由基产生增加和细胞因子的刺激。在这些情况下，铁蛋白的主要功能是降低铁的生物可用性，以阻止不受控制的细胞增殖和活性氧自由基的过度产生。然而，在这些情况下，铁蛋白并非不加区分地上调，因为会出现明显向富含H亚基的铁蛋白占优势的转变。初步迹象表明，虽然L亚基主要履行传统的铁储存作用，但H亚基主要作为铁可用性的快速调节因子发挥作用，也许还间接作为其他细胞过程的调节因子。有人认为，两个亚基的最佳差异表达在不同细胞和不同条件下有所不同，并且适当的铁蛋白异构体的表达可提供针对不受控制的细胞增殖、氧化应激以及感染和炎症条件的副作用的保护。
