The O-fucosyltransferase O-fut1 is an extracellular component that is essential for the constitutive endocytic trafficking of Notch in Drosophila
The O-fucosyltransferase O-fut1 is an extracellular component that is essential for the constitutive endocytic trafficking of Notch in Drosophila
复制标题
DOI：
10.1242/dev.02811
复制
发表时间：
2007-04-01
期刊：
影响因子：
4.6
通讯作者：
Matsuno, Kenji
中科院分区：
文献类型：
--
作者：
Sasamura, Takeshi;Ishikawa, Hiroyuki O.;Matsuno, Kenji
Notch 是一种跨膜受体，可介导许多细胞命运决定所必需的细胞间相互作用。 Notch 的内吞运输在该受体的激活和下调中发挥重要作用。果蝇 O-FucT-1 同源物由 O-fut1 编码，催化 Notch 的 O-岩藻糖基化，这是 Notch 信号传导和配体结合所必需的修饰。最近有人提出，O-fut1 在内质网中充当 Notch 的伴侣，并且是 Notch 离开内质网所必需的。在此，我们报告 O-fut1 在 Notch 的内吞运输中具有附加功能。 O-fut1对于Notch从质膜到早期内体的组成性运输是不可或缺的，我们证明这与O-fut1的O-岩藻糖基转移酶活性无关。我们还发现 O-fut1 促进了 Notch 的更新，从而下调了 Notch 信号传导。 O-fut1 与 Notch 胞外结构域形成稳定的复合物。此外，将 O-fut1 蛋白添加到条件培养基中并进行内吞足以挽救 O-fut1 敲低细胞中正常的 Notch 转运至早期内体。因此，Notch 和 O-fut1 之间的细胞外相互作用对于 Notch 的正常内吞运输至关重要。我们认为，O-fut1 是除配体之外的第一个通过胞吞作用在细胞外进行受体运输所需的分子的例子。
Notch is a transmembrane receptor that mediates the cell-cell interactions necessary for many cell-fate decisions. Endocytic trafficking of Notch plays important roles in the activation and downregulation of this receptor. A Drosophila O-FucT-1 homolog, encoded by O-fut1, catalyzes the O-fucosylation of Notch, a modification essential for Notch signaling and ligand binding. It was recently proposed that O-fut1 acts as a chaperon for Notch in the endoplasmic reticulum and is required for Notch to exit the endoplasmic reticulum. Here, we report that O-fut1 has additional functions in the endocytic transportation of Notch. O-fut1 was indispensable for the constitutive transportation of Notch from the plasma membrane to the early endosome, which we show was independent of the O-fucosyltransferase activity of O-fut1. We also found that O-fut1 promoted the turnover of Notch, which consequently downregulated Notch signaling. O-fut1 formed a stable complex with the extracellular domain of Notch. In addition, O-fut1 protein added to conditioned medium and endocytosed was sufficient to rescue normal Notch transportation to the early endosome in O-fut1 knockdown cells. Thus, an extracellular interaction between Notch and O-fut1 is essential for the normal endocytic transportation of Notch. We propose that O-fut1 is the first example, except for ligands, of a molecule that is required extracellularly for receptor transportation by endocytosis.