Okabayashi Y, Maddux B A, McDonald A R, Logsdon C D, Williams J A, Goldfine I D
Cell Biology Laboratory, Mount Zion Hospital, San Francisco, California 94120.
Diabetes. 1989 Feb;38(2):182-7. doi: 10.2337/diab.38.2.182.
The influence of insulin on the downregulation of its receptor was studied in AR42J cultured pancreatic acinar cells, a cell line that has been demonstrated to be metabolically responsive to insulin. Downregulation induced by insulin was time and dose dependent. After a 20-h incubation with 1 microM insulin, Scatchard analysis revealed approximately 80% loss of insulin receptors. Studies of receptor half-life indicated that treatment with insulin accelerated the degradation of both the alpha- and beta-subunits of the insulin receptor by 30-60%. In addition, biosynthetic-labeling studies indicated that insulin inhibited the biosynthesis of the insulin-receptor precursor by greater than 30%. This decreased biosynthesis of the precursor was associated with decreased production of mature receptor subunits. Poly(A)+ RNA was extracted from control cells and cells treated for 24 h with 100 nM insulin. Slot blots and Northern transfers revealed that insulin induced an approximately 50% decrease in insulin-receptor mRNA levels. Therefore, these studies indicate that insulin may diminish the concentration of its receptors in target cells by at least two mechanisms: acceleration of receptor degradation and inhibition of receptor biosynthesis at the level of mRNA.
在AR42J培养的胰腺腺泡细胞中研究了胰岛素对其受体下调的影响，该细胞系已被证明对胰岛素具有代谢反应性。胰岛素诱导的下调具有时间和剂量依赖性。用1微摩尔胰岛素孵育20小时后，Scatchard分析显示胰岛素受体损失约80%。受体半衰期研究表明，胰岛素处理使胰岛素受体的α亚基和β亚基的降解加速30%-60%。此外，生物合成标记研究表明，胰岛素抑制胰岛素受体前体的生物合成超过30%。前体生物合成的减少与成熟受体亚基产量的降低有关。从对照细胞和用100纳摩尔胰岛素处理24小时的细胞中提取聚腺苷酸加尾RNA。狭缝印迹和Northern印迹显示，胰岛素使胰岛素受体mRNA水平降低约50%。因此，这些研究表明，胰岛素可能通过至少两种机制降低其在靶细胞中的受体浓度：加速受体降解和在mRNA水平抑制受体生物合成。
