Insulin and α2‐macroglobulin‐methylamine undergo endocytosis by different mechanisms in rat adipocytes: I. Comparison of cell surface events
Insulin and α2‐macroglobulin‐methylamine undergo endocytosis by different mechanisms in rat adipocytes: I. Comparison of cell surface events
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胰岛素和α2-巨球蛋白-甲胺在大鼠脂肪细胞中通过不同机制进行内吞作用：I.细胞表面事件的比较
DOI：
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发表时间：
1987
影响因子：
5.6
通讯作者：
L. Jarett
中科院分区：
文献类型：
--
作者：
R. Goldberg;Robert M. Smith;L. Jarett
这项超微结构研究比较了多肽激素铁蛋白标记胰岛素(Fm-I)或金标胰岛素(Au-I)和非激素配体金标记α-2-巨球蛋白-甲胺(Au-α2MGMA)对大鼠脂肪细胞的内吞作用。细胞表面的定量分析表明，包被的凹坑占脂肪细胞表面的0.4%。这是已报道的成纤维细胞和肝细胞的五分之一到十分之一，在这些细胞类型中，受体介导的内吞作用已经得到了广泛的研究。相比之下，未包被的微吞饮内陷相当多，占脂肪细胞表面的13.1%。小吞噬细胞内陷的频率，每μm~2质膜13.8%，是已报道的成纤维细胞的7-12倍。因此，大鼠脂肪细胞的内吞细胞器的超微结构不同于更常见的细胞类型。在4℃时，Au-α2MGMA集中在被涂层的凹坑中，密度是未被涂层的质膜的52倍。Au-α2MGMA可排除93%以上的微吞饮内陷，这种排除与Au-α2MGMA颗粒的大小无关。相反，在4℃时，FM-I没有集中在包被的凹坑中，以随机的方式占据微吞饮内陷。在37℃时，Au-α2MGMA的所有内吞作用都被包被的凹坑占据，证明这些结构是有功能的，尽管它们的密度非常低。相比之下，超过99%的FM-I或Au-I的内吞作用是通过微胞内吞发生的。这些结果首次用比较的、定量的、超微结构的方法证明了胰岛素和Au-α2MGMA在大鼠脂肪细胞上以不同的机制发生内吞作用。胰岛素和Au-α2MGMA内吞作用的不同可能与这两个分子的不同生物学作用有关。
This ultrastructural study compared the endocytosis of a peptide hormone, ferritin‐labeled insulin (Fm‐I) or gold‐labeled insulin (Au‐I), and a non‐hormonal ligand, gold‐labeled alpha‐2‐macroglobulin‐methylamine (Au‐α2MGMA), by rat adipocytes. Quantitative analysis of the cell surface showed that coated pits occupied 0.4% of the adipocyte surface. This was one fifth to one tenth of that which has been reported on fibroblasts and hepatocytes, cell types in which receptor‐mediated endocytosis has been extensively studied. In contrast, uncoated micropinocytotic invaginations were quite numerous and occupied 13.1% of the adipocyte cell surface. The frequency of microphinocytotic invaginations, 13.8 per μm2 of plasma membrane, was 7–12 times greater than has been reported on fibroblasts. Therefore, the ultrastructure of the endocytic apparatus on rat adipocytes was different from more commonly studied cell types. At 4°C, Au‐α2MGMA concentrated within coated pits to a density that was 52 times greater than that on the uncoated plasma membrane. Au‐α2MGMA was excluded from micropinocytotic invaginations by more than 93%; this exclusion was unrelated to the size of the Au‐α2MGMA particle. In contrast, at 4°C, Fm‐I did not concentrate within coated pits and occupied micropinocytotic invaginations in a random manner. At 37°C, coated pits accounted for all of the endocytosis of Au‐α2MGMA, proving that these structures were functional despite their atypically low density. In contrast, greater than 99% of the endocytosis of Fm‐I or Au‐I occurred through micropinocytotic invaginations. These results demonstrated for the first time by a comparative, quantitative, ultrastructural method that insulin and Au‐α2MGMA undergo endocytosis by dissimilar mechanisms on rat adipocytes. Dissimilarities in the endocytosis of insulin and Au‐α2MGMA may be related to the different biological roles of these two molecules.
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DOI：
10.1073/pnas.84.2.459
发表时间：
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影响因子：
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DOI：
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发表时间：
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期刊：
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DOI：
--
发表时间：
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期刊：
The Journal of biological chemistry
影响因子：
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