Historically, the trans-Golgi network (TGN) has been recognized as a sorting center of newly synthesized proteins, whereas the recycling endosome (RE) is a compartment where endocytosed materials transit before being recycled to the plasma membrane. However, recent findings revealed that both the TGN and RE connect endocytosis and exocytosis and, thus, are functionally overlapping. Here we report, in both Drosophila and microtubule-disrupted HeLa cells, that REs are interconvertible between two distinct states, namely Golgi-associated REs and free REs. Detachment and reattachment of REs and Golgi stacks are often observed, and newly synthesized glycosylphosphatidylinositol-anchored cargo protein but not vesicular stomatitis virus G protein is transported through these two types of RE. In plants, there are two types of TGN - Golgi-associated TGN and Golgi-independent TGN. We show that dynamics of REs in both Drosophila and mammalian cells are very similar compared with those of plant TGNs. And, together with the similarity on the molecular level, our results indicate that fly and mammalian REs are organelles that are equivalent to TGNs in plants. This suggests that the identities and functional relationships between REs and TGNs should be reconsidered.

中文翻译：

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在果蝇和哺乳动物细胞中，回收内体附着在高尔基体堆的反侧。

从历史上看，反式高尔基体网络（TGN）被认为是新合成蛋白质的分选中心，而再循环内体（RE）是内吞物质在再循环到质膜之前转运的隔室。然而，最近的研究结果表明，TGN 和 RE 都连接胞吞作用和胞吐作用，因此在功能上是重叠的。在这里，我们报告，在果蝇和微管破坏的 HeLa 细胞中，RE 可以在两种不同状态（即高尔基体相关 RE 和游离 RE）之间相互转换。经常观察到 RE 和高尔基体堆叠的分离和重新附着，并且新合成的糖基磷脂酰肌醇锚定的货物蛋白而不是水泡性口炎病毒 G 蛋白通过这两种类型的 RE 运输。在植物中，有两种类型的 TGN：高尔基相关 TGN 和高尔基独立 TGN。我们发现果蝇和哺乳动物细胞中 RE 的动态与植物 TGN 的动态非常相似。而且，结合分子水平上的相似性，我们的结果表明，果蝇和哺乳动物的 RE 是与植物中的 TGN 等效的细胞器。这表明应重新考虑 RE 和 TGN 之间的身份和功能关系。