Insulin-stimulated fluid-phase pinocytosis and internalization of the insulin receptor: differences between the U-937 monocyte and rat adipocyte.
Insulin-stimulated fluid-phase pinocytosis and internalization of the insulin receptor: differences between the U-937 monocyte and rat adipocyte.
复制标题
胰岛素刺激的液相胞饮作用和胰岛素受体的内化：U-937 单核细胞和大鼠脂肪细胞之间的差异。
DOI：
10.1016/0026-0495(86)90222-2
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Livingston,JN
中科院分区：
文献类型：
--
作者：
Oefelein,MG;Arsenis,G;Livingston,JN
U-937单核细胞是一种人类细胞系，通过内化胰岛素受体和加速液相吞饮而对胰岛素产生强烈反应。在目前的研究中，这两个过程都被证明需要能量，并且都依赖于胰岛素受体的数量。胰岛素受体数量减少的单核细胞，即被16小时的胰岛素处理下调的单核细胞，对胰岛素刺激的胞饮作用的反应显著降低，内化的胰岛素受体数量减少。然而，后一种特征是由于细胞中胰岛素受体含量的减少造成的。在胰岛素急性处理30分钟期间，内化受体的比例(例如，59%的细胞表面受体)略高于对照细胞内化的比例。因此，下调不会选择性地破坏循环中的受体，只留下固定在膜上的一小部分受体。显然，胰岛素受体只有一个群体，它们在内化方面都具有同等的能力。尽管这些结果表明胞饮作用和受体内化之间有密切的关系，但将这两个系统分开是可能的。在没有增加胰岛素受体内化的情况下，多聚L赖氨酸的加入产生了显着的液体相吞饮作用刺激。因此，受体进入内池需要的不仅仅是胞饮速率的增加。大鼠脂肪细胞也进行了研究，结果在几个方面与U-937单核细胞的结果不同。虽然胰岛素刺激脂肪细胞受体内化，但它并不增加液体相吞噬作用。此外，能量消耗本身也增加了受体的内在化。因此，尽管这两种细胞在急性胰岛素刺激过程中都经历了受体加速循环，但导致这种现象的分子事件在整个过程中的某个步骤是不同的。这些研究还表明，吞饮作用的增加本身不足以导致胰岛素受体向内部池移动的增强。
U-937 monocytes, a human cell line, respond acutely to insulin by internalization of the insulin receptor and acceleration of fluid-phase pinocytosis. In the present studies, both processes were shown to require energy and both were dependent on the number of insulin receptors. Monocytes with a reduced number of insulin receptors, ie, down-regulated by a 16-hour insulin treatment, had a markedly reduced response to insulin-stimulation of pinocytosis and a decrease in the amount of insulin receptors internalized. This latter feature resulted, however, from the reduction in the cellular content of insulin receptors. The proportion of receptor internalized during a 30-minute acute treatment with insulin (eg, 59% of the cell surface receptors) was slightly greater than the proportion internalized in control cells. Therefore, down-regulation does not selectively destroy receptors that cycle, leaving only a subpopulation of receptors anchored in the membrane. Apparently, there is only one population of insulin receptors, all of which are equally competent with respect to internalization. Although these results suggest a close relationship between pinocytosis and receptor internalization, it was possible to separate the two systems. The addition of poly-l-lysine produced a marked stimulation of fluid-phase pinocytosis in the absence of any increase in insulin receptor internalization. Thus, movement of the receptor into the internal pool requires more than an increase in the rate of pinocytosis. Rat adipocytes were also studied, and the results differed in several aspects from those of U-937 monocytes. Although insulin stimulated adipocyte receptor internalization, it did not increase fluid-phase pinocytosis. Also, energy depletion itself increased receptor internalization. Thus, even though both cell types undergo accelerated receptor cycling during acute insulin stimulation, the molecular events responsible for this phenomenon differ at some step in the overall process. These studies also show that an increased rate of pinocytosis is of itself not enough to cause an enhanced movement of the insulin receptor to internal pools.