Characterization of a transferrin-independent uptake system for iron in HeLa cells.
Characterization of a transferrin-independent uptake system for iron in HeLa cells.
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DOI：
10.1016/s0021-9258(19)39745-5
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发表时间：
1990-02
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影响因子：
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通讯作者：
A. Sturrock;J. Alexander;Jamie Lamb;Catherine M. Craven;Jerry Kaplan
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文献类型：
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作者：
A. Sturrock;J. Alexander;Jamie Lamb;Catherine M. Craven;Jerry Kaplan
在无血清培养基中培养的HeLa细胞，无论与59Fe-柠檬酸盐、59Fe-硝基三乙酸盐或溶解在抗坏血酸三氨酸中的59Fe一起培养，都积累了59Fe（“非转铁蛋白铁”）。铁的积累是时间、浓度和Ca2+依赖性的，并且是饱和的。非转铁蛋白（non-Tf）铁的摄取是不依赖于转铁蛋白的，因为摄取发生在pH为5.5的情况下，在这个pH下，转铁蛋白与铁结合很差，并且在这个pH下，转铁蛋白不能被细胞内化。1)将细胞暴露于胰蛋白酶（一种切割Tf受体的方法）或2)用氧化苯larsin（一种抑制流体和受体介导的内化的试剂）孵育细胞，对非Tf铁摄取的影响小于对转铁蛋白摄取的影响。在37℃下将细胞暴露于非tf铁后，血红素和铁蛋白中的大部分细胞相关放射性被恢复，这表明铁可以进入细胞内腔室，而不是简单地吸附在细胞表面。Cu2+可以以剂量依赖性的方式部分阻断非tf铁的吸收，而转铁蛋白结合铁的积累不受Cu2+的影响。其他过渡金属，如Zn2+、Cd2+和Mn2+能够不同程度地抑制非tf铁的吸收。用非tf铁、Cu2+或Mn2+培养细胞可抑制109Cd的积累。抑制程度呈浓度依赖性和金属依赖性。包括HeLa、人皮肤成纤维细胞和中国仓鼠卵巢细胞在内的许多培养细胞系显示出非tf铁和109Cd的摄取。此外，中国仓鼠卵巢细胞内小体酸化突变体显示出非tf铁摄取增加，也显示出Cd2+摄取增加。这些观察结果表明，HeLa细胞中非tf铁转运系统的特征即使不完全相同，也与报道的灌注大鼠肝脏相似（Wright， T. L., Brissot， P., Ma, w . L.）。，和Weisiger， p.a. (1986) J. Biol。化学，261,10909-10914)，并表明存在一个过渡金属转运系统家族，每一个都有不同的金属特异性。
HeLa cells incubated in serum-free medium accumulated 59Fe ("non-transferrin iron") when incubated with either 59Fe-citrate, 59Fe-nitrilotriacetate, or 59Fe dissolved in Tricine ascorbate. Accumulation of iron was time-, concentration-, and Ca2+-dependent and was saturable. Uptake of non-transferrin (non-Tf) iron was transferrin-independent because of the fact that uptake occurred at pH 5.5, a pH at which transferrin binds iron poorly and at which transferrin is not internalized by cells. Uptake of non-Tf iron was less affected than uptake of transferrin iron by 1) exposure of cells to trypsin, a maneuver that cleaves Tf receptors, or 2) incubation of cells with phenylarsine oxide, an agent that inhibits both fluid- and receptor-mediated internalization. After exposure of cells to non-Tf iron at 37 degrees C, most of the cell-associated radioactivity was recovered in heme and ferritin, demonstrating that iron gained access to intracellular compartments and was not simply adsorbed to the cell surface. Uptake of non-Tf iron could be partially blocked by Cu2+ in a dose-dependent manner, while the accumulation of transferrin-bound iron was unaffected by Cu2+. Other transition metals, such as Zn2+, Cd2+, and Mn2+ were able to inhibit the uptake of non-Tf iron to different degrees. The accumulation of 109Cd was inhibited by incubation of cells with non-Tf iron, Cu2+, or Mn2+. The extent of inhibition was concentration- and metal-dependent. A number of cultured cell lines including HeLa, human skin fibroblasts, and Chinese hamster ovary cells demonstrated uptake of non-Tf iron and 109Cd. Additionally, an endosome acidification mutant of Chinese hamster ovary cells, which exhibited an increase in non-Tf iron uptake, also exhibited an increase in the uptake of Cd2+. These observations suggest that the characteristics of the non-Tf iron transport system in HeLa cells are similar if not identical to those reported for perfused rat liver (Wright, T. L., Brissot, P., Ma, W.-L., and Weisiger, P. A. (1986) J. Biol. Chem. 261, 10909-10914) and suggest the existence of a family of transition metal transport systems, each with a different metal specificity.