Association with membrane protrusions makes ErbB2 an internalization-resistant receptor
Association with membrane protrusions makes ErbB2 an internalization-resistant receptor
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DOI：
10.1091/mbc.e03-08-0596
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发表时间：
2004-04-01
影响因子：
3.3
通讯作者：
van Deurs, B
中科院分区：
文献类型：
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作者：
Hommelgaard, AM;Lerdrup, M;van Deurs, B
与表皮生长因子 (EGF) 受体相反，ErbB2 在配体结合和二聚化后仍保留在质膜上。然而，为什么 ErbB2 没有被有效下调仍不清楚。基本上，存在两种可能性：ErbB2 具有抗内化性，或者在内化后被有效回收。通过结合共聚焦显微镜、免疫金标记电子显微镜和生化技术，我们发现 ErbB2 优先与膜突起相关。此外，它被有效地从网格蛋白包被的凹坑中排除，并且在含有转铁蛋白受体的内体中未见。这种模式在 EGF、heregulin 或赫赛汀结合后不会改变。包被凹坑的排除是如此明显，以至于不能仅仅用缺乏内化信号来解释。尽管 ErbB2 是筏相关蛋白，但 ErbB2 定位到突起并不是筏结合的结果。此外，不需要完整的肌动蛋白细胞骨架来使 ErbB2 远离包被的凹坑。然而，在有效交联后，ErbB2 从突出物中去除，出现在本体膜、包被的凹坑和内涵体中。这些数据表明，ErbB2 是一种显着的内化抗性受体，并表明 ErbB2 与突起牢固结合的机制也是这种抗性的原因。
In contrast to the epidermal growth factor (EGF) receptor, ErbB2 is known to remain at the plasma membrane after ligand binding and dimerization. However, why ErbB2 is not efficiently down-regulated has remained elusive. Basically, two possibilities exist: ErbB2 is internalization resistant or it is efficiently recycled after internalization. By a combination of confocal microscopy, immunogold labeling electron microscopy, and biochemical techniques we show that ErbB2 is preferentially associated with membrane protrusions. Moreover, it is efficiently excluded from clathrin-coated pits and is not seen in transferrin receptor-containing endosomes. This pattern is not changed after binding of EGF, heregulin, or herceptin. The exclusion from coated pits is so pronounced that it cannot just be explained by lack of an internalization signal. Although ErbB2 is a raft-associated protein, the localization of ErbB2 to protrusions is not a result of raft binding. Also, an intact actin cytoskeleton is not required for keeping ErbB2 away from coated pits. However, after efficient cross-linking, ErbB2 is removed from protrusions to occur on the bulk membrane, in coated pits, and in endosomes. These data show that ErbB2 is a remarkably internalization-resistant receptor and suggest that the mechanism underlying the firm association of ErbB2 with protrusions also is the reason for this resistance.