Presley John F, Ward Theresa H, Pfeifer Andrea C, Siggia Eric D, Phair Robert D, Lippincott-Schwartz Jennifer
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Nature. 2002 May 9;417(6885):187-93. doi: 10.1038/417187a.
Cytosolic coat proteins that bind reversibly to membranes have a central function in membrane transport within the secretory pathway. One well-studied example is COPI or coatomer, a heptameric protein complex that is recruited to membranes by the GTP-binding protein Arf1. Assembly into an electron-dense coat then helps in budding off membrane to be transported between the endoplasmic reticulum (ER) and Golgi apparatus. Here we propose and corroborate a simple model for coatomer and Arf1 activity based on results analysing the distribution and lifetime of fluorescently labelled coatomer and Arf1 on Golgi membranes of living cells. We find that activated Arf1 brings coatomer to membranes. However, once associated with membranes, Arf1 and coatomer have different residence times: coatomer remains on membranes after Arf1-GTP has been hydrolysed and dissociated. Rapid membrane binding and dissociation of coatomer and Arf1 occur stochastically, even without vesicle budding. We propose that this continuous activity of coatomer and Arf1 generates kinetically stable membrane domains that are connected to the formation of COPI-containing transport intermediates. This role for Arf1/coatomer might provide a model for investigating the behaviour of other coat protein systems within cells.
可与膜可逆结合的胞质衣被蛋白在分泌途径中的膜运输中发挥着核心作用。一个经过充分研究的例子是 COPI 或衣被蛋白复合物，它是一种七聚体蛋白复合物，由 GTP 结合蛋白 Arf1 募集到膜上。组装成电子致密衣被有助于从膜上出芽，以便在内质网（ER）和高尔基体之间运输。在此，我们基于对活细胞高尔基体膜上荧光标记的衣被蛋白复合物和 Arf1 的分布及寿命分析结果，提出并证实了一个关于衣被蛋白复合物和 Arf1 活性的简单模型。我们发现，活化的 Arf1 将衣被蛋白复合物带到膜上。然而，一旦与膜结合，Arf1 和衣被蛋白复合物具有不同的驻留时间：在 Arf1 - GTP 水解和解离后，衣被蛋白复合物仍留在膜上。衣被蛋白复合物和 Arf1 与膜的快速结合和解离是随机发生的，即使没有囊泡出芽。我们提出，衣被蛋白复合物和 Arf1 的这种持续活性产生了动力学稳定的膜结构域，这些结构域与含 COPI 的运输中间体的形成相关。Arf1/衣被蛋白复合物的这种作用可能为研究细胞内其他衣被蛋白系统的行为提供一个模型。
