Stein B S, Bensch K G, Sussman H H
J Biol Chem. 1984 Dec 10;259(23):14762-72.
Monensin blocks human transferrin recycling in a dose-dependent and reversible manner in K562 cells, reaching 100% inhibition at a noncytocidal dose of 10(-5) M, whereas transferrin recycling is virtually unaffected by noncytocidal doses of chloroquine. The intracellular pathway of human transferrin in K562 cells, both in the presence and absence of 10(-5) M monensin, was localized by indirect immunofluorescence. Monensin blocks transferrin recycling by causing internalized ligand to accumulate in the perinuclear region of the cell. The effect of 10(-5) M monensin on human transferrin kinetics was quantitatively measured by radioimmunoassay and showed a positive correlation with immunofluorescent studies. Immunoelectron microscopic localization of human transferrin as it cycles through K562 cells reveals the appearance of perinuclear transferrin-positive multivesicular bodies within 3 min of internalization, with subsequent exocytic delivery of the ligand to the cell surface via transferrin-staining vesicles arising from these perinuclear structures within 5 min of internalization. Inhibition of ligand recycling with 10(-5) M monensin causes dilated transferrin-positive multivesicular bodies to accumulate within the cell with no evidence of recycling vesicles. A coordinated interaction between multivesicular bodies and the Golgi apparatus appears to be involved in the recycling of transferrin in K562 cells. Cell-surface-binding sites for transferrin were reduced by 50% with 10(-5) M monensin treatment; however, this effect was not attenuated by 80% protein synthesis inhibition with cycloheximide, supporting the idea that the transferrin receptor is also recycled through the Golgi.
莫能菌素以剂量依赖且可逆的方式阻断K562细胞中人类转铁蛋白的循环利用，在非细胞毒性剂量10⁻⁵ M时达到100%抑制，而在非细胞毒性剂量下，氯喹对转铁蛋白循环利用几乎没有影响。通过间接免疫荧光对存在和不存在10⁻⁵ M莫能菌素时K562细胞中人类转铁蛋白的细胞内途径进行了定位。莫能菌素通过使内化的配体在细胞的核周区域积累来阻断转铁蛋白的循环利用。通过放射免疫测定法定量测量了10⁻⁵ M莫能菌素对人类转铁蛋白动力学的影响，结果显示与免疫荧光研究呈正相关。人类转铁蛋白在K562细胞中循环时的免疫电子显微镜定位显示，内化后3分钟内出现核周转铁蛋白阳性多囊泡体，随后在内化后5分钟内，配体通过源自这些核周结构的转铁蛋白染色囊泡以胞吐方式传递到细胞表面。用10⁻⁵ M莫能菌素抑制配体循环会导致转铁蛋白阳性多囊泡体在细胞内积累，且没有循环囊泡的证据。多囊泡体与高尔基体之间的协同相互作用似乎参与了K562细胞中转铁蛋白的循环利用。用10⁻⁵ M莫能菌素处理后，转铁蛋白的细胞表面结合位点减少了50%；然而，用环己酰亚胺抑制80%的蛋白质合成并没有减弱这种作用，这支持了转铁蛋白受体也通过高尔基体循环的观点。
