Ezaki O, Kono T
Arch Biochem Biophys. 1984 Jun;231(2):280-6. doi: 10.1016/0003-9861(84)90389-8.
Comparative studies were made on the sedimentation characteristics of microsomal vesicles associated with internalized [125I]iodoinsulin and those bound with intracellular glucose transport activity. Upon linear sucrose density gradient centrifugation, the internalized hormone formed a peak slightly, but significantly, on the higher density side of the peak of intracellular glucose transport activity. After a long centrifugation, the peak of 125I activity became lower and broader than that of glucose transport activity. Internalized 125I activity was also found in the medium-density microsomal fraction, which had little glucose transport activity. Accumulation of 125I activity in the medium-density fraction and that in the low-density fraction were both completed in approximately 10 min. Under basal conditions, little, if any, insulin binding activity was detectable in either the medium- or low-density microsomal fractions; in contrast, some glucose transport activity was always present in the low-density fraction. These results indicate that the subcellular distribution of internalized insulin and of intracellular glucose transport activity are different, suggesting that the pathways of intracellular processing of the insulin receptor and the glucose transport mechanism are different.
对与内化的[125I]碘胰岛素相关的微粒体囊泡的沉降特性和与细胞内葡萄糖转运活性结合的微粒体囊泡的沉降特性进行了比较研究。在线性蔗糖密度梯度离心时，内化的激素在细胞内葡萄糖转运活性峰的较高密度侧形成一个稍高但明显的峰。长时间离心后，125I活性峰比葡萄糖转运活性峰更低且更宽。在中等密度的微粒体组分中也发现了内化的125I活性，而该组分几乎没有葡萄糖转运活性。中等密度组分和低密度组分中125I活性的积累均在约10分钟内完成。在基础条件下，在中等密度或低密度微粒体组分中几乎检测不到胰岛素结合活性；相反，低密度组分中总是存在一些葡萄糖转运活性。这些结果表明，内化胰岛素的亚细胞分布与细胞内葡萄糖转运活性的亚细胞分布不同，提示胰岛素受体的细胞内加工途径和葡萄糖转运机制不同。
