EGF induces recycling membrane to form ruffles
EGF induces recycling membrane to form ruffles
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DOI：
10.1016/s0960-9822(98)70281-7
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发表时间：
1998-06-04
期刊：
影响因子：
9.2
通讯作者：
Aguado-Velasco, C
中科院分区：
文献类型：
--
作者：
Bretscher, MS;Aguado-Velasco, C
已知KB细胞通过在几分钟内在质膜中产生巨大的荷叶边来对表皮生长因子（EGF）做出反应。成纤维细胞中这种作用的信号转导途径是通过RAC（RAS样的GTPases家族的成员）介导的[1,2]。由于荷叶蛋白富含肌动蛋白的细胞骨架的成分，并且已经提出Ezrin-iT，当激活的PAC调节肌动蛋白细胞骨架以推出膜突出时，会出现荷叶蛋白。我们着手看看新荷叶边的表面是否来自相邻的膜，还是来自内吞膜的细胞内池。如果它是由内体的胞吐作用引起的，则预计它将富集在循环的内吞一侧的涂层坑中的回收受体中，另一方面，如果它是从相邻的质膜中被动地引起的，它是均匀的这些受体的分布将被期望。在这里，我们表明，一旦荷叶边响应于EGF [3,4]，荷叶边就会富含转铁蛋白和低密度脂蛋白（LDL）受体。已知这两种蛋白质都通过网格蛋白介导的内吞作用选择性地浓缩到内体膜中。我们的结果表明，荷叶边的表面是通过内吞周期内膜的胞吐作用而产生的，因此，RAC的主要作用是将回收膜的胞吐作用重定向到那些形成荷叶边形成的特定部位。
KB cells are known to respond to epidermal growth factor (EGF) by producing prodigious ruffles in the plasma membrane within minutes. The signal transduction pathway underlying this effect in fibroblasts is mediated through Rac, a member of the Ras-like family of GTPases [1,2]. As ruffles are rich in components of the cytoskeleton-particularly in actin and ezrin-it has been suggested that ruffles arise when activated pac modulates the actin cytoskeleton to push out a membrane protrusion. We set out to see whether the surface of new ruffles arises from neighbouring membrane, or whether it comes from an intracellular pool of endocytosed membrane. If it arose by exocytosis from endosomes, it would be expected to be enriched in those recycling receptors that are concentrated in coated pits in the endocytic side of the cycle, On the other hand, if it arose passively from the adjacent plasma membrane, a uniform distribution of these receptors would be expected. Here, we show that as soon as ruffles appear on KB cells in response to EGF [3,4], their membrane surfaces are enriched in both transferrin and low density lipoprotein (LDL) receptors. Both these proteins are known to be selectively concentrated into endosomal membranes by clathrin-mediated endocytosis. Our results reveal that the surfaces of ruffles arise by exocytosis of internal membrane from the endocytic cycle and, therefore, that a primary action of Rac is to redirect the exocytosis of recycling membrane into just those specific sites where ruffles form.