Mattia E, Josic D, Ashwell G, Klausner R, van Renswoude J
J Biol Chem. 1986 Apr 5;261(10):4587-93.
Following a pulse with 59Fe-transferrin, K562 erythroleukemia cells incorporate a significant amount of 59Fe into ferritin. Conditions or manipulations which alter the supply of iron to cells result in changes in the rate of ferritin biosynthesis with consequent variations in the size of the ferritin pool. Overnight exposure to iron donors such as diferric transferrin or hemin increases the ferritin level 2-4- or 6-8-fold above that of the control, respectively. Treatment with the anti-human transferrin receptor antibody, OKT9 (which reduces the iron uptake by decreasing the number of transferrin receptors) lowers the ferritin level by approximately 70-80% with respect to the control. The fraction of total cell-associated 59Fe (given as a pulse via transferrin) that becomes ferritin bound is proportional to the actual ferritin level and is independent of the instantaneous amount of iron taken up. This has allowed us to establish a curve that correlates different levels of intracellular ferritin with corresponding percentages of incoming iron delivered to ferritin. Iron released from transferrin appears to distribute to ferritin according to a partition function; the entering load going into ferritin is set for a given ferritin level over a wide range of actual amounts of iron delivered.
用59Fe - 转铁蛋白脉冲处理后，K562红白血病细胞会将大量的59Fe掺入铁蛋白中。改变细胞铁供应的条件或操作会导致铁蛋白生物合成速率发生变化，从而使铁蛋白池的大小也随之改变。过夜暴露于铁供体（如二价铁转铁蛋白或血红素）中，铁蛋白水平分别比对照升高2 - 4倍或6 - 8倍。用抗人转铁蛋白受体抗体OKT9处理（通过减少转铁蛋白受体数量来降低铁摄取），相对于对照，铁蛋白水平降低约70 - 80%。通过转铁蛋白以脉冲形式给予的与细胞相关的总59Fe中，与铁蛋白结合的部分与实际铁蛋白水平成正比，且与瞬时摄取的铁量无关。这使我们能够建立一条曲线，将细胞内不同水平的铁蛋白与输送到铁蛋白的相应百分比的进入铁相关联。从转铁蛋白释放的铁似乎根据分配函数分布到铁蛋白中；在广泛的实际输送铁量范围内，对于给定的铁蛋白水平，进入铁蛋白的输入负荷是固定的。
