Hypertonic media inhibit receptor-mediated endocytosis by blocking clathrin-coated pit formation.
Hypertonic media inhibit receptor-mediated endocytosis by blocking clathrin-coated pit formation.
复制标题
高渗培养基通过阻断网状蛋白包被的凹坑的形成来抑制受体介导的内吞作用。
DOI：
10.1083/jcb.108.2.389
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发表时间：
1989-02
期刊：
影响因子：
--
通讯作者：
Anderson RG
中科院分区：
文献类型：
--
作者：
Heuser JE;Anderson RG
两种看似无关的实验处理抑制受体介导的内吞作用：（a）细胞内K+的消耗（Larkin，J.M.，M. S.布朗，J.L. Goldstein和R. G. W.安德森。1983. Cell. 33：273- 285）;和（B）用高渗介质处理（Daukas，G.，和S. H.齐格蒙1985. 101：1673-1679）。由于前者抑制网格蛋白包被的凹坑的形成（Larkin，J.M.，W. D. Donzell和R. G. W.安德森，1986年。103：2619-2627），我们感兴趣的是确定高渗治疗是否具有相同的效果，如果是，为什么。将成纤维细胞（人或鸡）在用0.45 M蔗糖制成高渗的生理盐水中孵育，然后通过超声处理和冷冻蚀刻破碎以产生其内膜表面的复制品。而未处理的细胞显示典型的网格蛋白的测地线网格下每个包被的坑，高渗细胞显示，此外，一些空网格蛋白的“微笼”。起初，这些出现在正常的涂层坑格的边缘周围。然而，随着时间的推移，在高渗介质中，正常的晶格在很大程度上消失，取而代之的是积累的微笼。同时，低密度脂蛋白（LDL）受体失去其正常的聚集分布，并成为分散在整个细胞表面，如所看到的荧光显微镜和冷冻蚀刻电子显微镜的LDL连接到细胞表面。当回到37摄氏度的正常介质时，这些变化迅速逆转。在2分钟内，小集群的LDL重新出现在细胞表面和正常网格蛋白晶格开始内重新出现，这些受体/网格蛋白复合物的大小和数量在接下来的10分钟内恢复正常。因此，尽管他们似乎无关，K+耗竭和高渗治疗导致涂层坑消失，都诱导异常网格蛋白聚合成空的微笼。这表明，在这两种情况下，异常形成的微笼抑制内吞作用，使网格蛋白无法组装成正常的涂层坑。
Two seemingly unrelated experimental treatments inhibit receptor mediated endocytosis: (a) depletion of intracellular K+ (Larkin, J. M., M. S. Brown, J. L. Goldstein, and R. G. W. Anderson. 1983. Cell. 33:273- 285); and (b) treatment with hypertonic media (Daukas, G., and S. H. Zigmond. 1985. J. Cell Biol. 101:1673-1679). Since the former inhibits the formation of clathrin-coated pits (Larkin, J. M., W. D. Donzell, and R. G. W. Anderson, 1986. J. Cell Biol. 103:2619-2627), we were interested in determining whether hypertonic treatment has the same effect, and if so, why. Fibroblasts (human or chicken) were incubated in normal saline made hypertonic with 0.45 M sucrose, then broken open by sonication and freeze-etched to generate replicas of their inner membrane surfaces. Whereas untreated cells display typical geodesic lattices of clathrin under each coated pit, hypertonic cells display in addition a number of empty clathrin "microcages". At first, these appear around the edges of normal coated pit lattices. With further time in hypertonic medium, however, normal lattices largely disappear and are replaced by accumulations of microcages. Concomitantly, low density lipoprotein (LDL) receptors lose their normal clustered distribution and become dispersed all over the cell surface, as seen by fluorescence microscopy and freeze-etch electron microscopy of LDL attached to the cell surface. Upon return to normal medium at 37 degrees C, these changes promptly reverse. Within 2 min, small clusters of LDL reappear on the surfaces of cells and normal clathrin lattices begin to reappear inside; the size and number of these receptor/clathrin complexes returns to normal over the next 10 min. Thus, in spite of their seeming unrelatedness, both K+ depletion and hypertonic treatment cause coated pits to disappear, and both induce abnormal clathrin polymerization into empty microcages. This suggests that in both cases, an abnormal formation of microcages inhibits endocytosis by rendering clathrin unavailable for assembly into normal coated pits.