Gibbs E M, Lienhard G E, Gould G W
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03756.
Biochemistry. 1988 Sep 6;27(18):6681-5. doi: 10.1021/bi00418a006.
Insulin stimulation of hexose transport in 3T3-L1 adipocytes was studied at 27 degrees C. At this temperature, the transport of 2-deoxyglucose was stimulated 8-fold, with a half-time of 9.5 min. Under the same conditions, the increase in cell surface glucose transporters, as measured by labeling in the intact cell with galactose oxidase and tritiated borohydride, was only 2.6-fold. Moreover, the half-times for the increase in cell surface glucose transporters and for the decrease in transporter number in the intracellular pool were both 4 min. Thus, these processes clearly precede the full stimulation of transport. These data are in agreement with immunolocalization studies of the glucose transporter in this cell line and further support the hypothesis that a second mechanism besides translocation is involved in the stimulation of hexose transport by insulin [Blok, J., Gibbs, E. M., Lienhard, G. E., Slot, J. W., & Gueze, H. J. (1988) J. Cell Biol. 106, 69-76]. The findings presented here indicate that neither the translocation of glucose transporters to, nor their subsequent insertion into, the plasma membrane is the rate-limiting step in the stimulation of hexose transport by insulin. Rather, there is a second mechanism of activation, which is rate limiting and occurs after the transporter is in the plasma membrane.
在27摄氏度下研究了胰岛素对3T3-L1脂肪细胞中己糖转运的刺激作用。在此温度下，2-脱氧葡萄糖的转运被刺激了8倍，半衰期为9.5分钟。在相同条件下，通过用半乳糖氧化酶和氚化硼氢化钠对完整细胞进行标记来测量，细胞表面葡萄糖转运蛋白的增加仅为2.6倍。此外，细胞表面葡萄糖转运蛋白增加和细胞内池转运蛋白数量减少的半衰期均为4分钟。因此，这些过程显然先于转运的完全刺激。这些数据与该细胞系中葡萄糖转运蛋白的免疫定位研究一致，并进一步支持了这样的假设，即除了易位之外，还有第二种机制参与胰岛素对己糖转运的刺激作用[布洛克，J.，吉布斯，E.M.，利恩哈德，G.E.，斯洛特，J.W.，& 盖泽，H.J.（1988年）《细胞生物学杂志》106卷，69 - 76页]。此处呈现的研究结果表明，葡萄糖转运蛋白向质膜的易位及其随后插入质膜都不是胰岛素刺激己糖转运的限速步骤。相反，存在第二种激活机制，它是限速的，并且发生在转运蛋白位于质膜之后。
