Takahashi K, Tavassoli M
J Ultrastruct Res. 1983 Mar;82(3):314-21. doi: 10.1016/s0022-5320(83)80018-5.
To determine if the cellular uptake of iron is associated with internalization of iron-transferrin (TF) complex by the cell, we synthesized a visual probe in which TF is covalently bound to amide-modified latex minibead, submicrometer in size (0.345 micron). Incubation of the probe with L1210 leukemia cells and rat reticulocytes led to the binding of the probe to the cell surface visualized and semiquantified by scanning and transmission electron microscopy. The binding was inhibited by preincubation with nonderivatized iron-TF complex. Internalization of the probe occurred through clathrin-coated pits and vesicles. Minibeads derivatized by nontransport proteins or glycine as well as nonderivatized minibeads did not appreciably bind to the cells and were not internalized. Ethylamine, an inhibitor of receptor-mediated endocytosis abolished the internalization but not the binding of the probe which, then, accumulated on the cell surface. These findings provide direct evidence for internalization of TF during the iron uptake.
为了确定细胞对铁的摄取是否与细胞对铁 - 转铁蛋白（TF）复合物的内化作用相关，我们合成了一种可视化探针，其中TF与酰胺修饰的乳胶微珠共价结合，该微珠尺寸为亚微米级（0.345微米）。将该探针与L1210白血病细胞和大鼠网织红细胞一起孵育，通过扫描电子显微镜和透射电子显微镜观察并半定量探针与细胞表面的结合情况。预先用未衍生化的铁 - TF复合物孵育可抑制这种结合。探针的内化通过网格蛋白包被的凹陷和小泡进行。由非转运蛋白或甘氨酸衍生化的微珠以及未衍生化的微珠不会明显结合到细胞上，也不会被内化。受体介导的内吞作用抑制剂乙胺消除了探针的内化，但没有消除其结合，此时探针积聚在细胞表面。这些发现为铁摄取过程中TF的内化提供了直接证据。
