A Cluster of Thin Tubular Structures Mediates Transformation of the Endoplasmic Reticulum to Autophagic Isolation Membrane
A Cluster of Thin Tubular Structures Mediates Transformation of the Endoplasmic Reticulum to Autophagic Isolation Membrane
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DOI：
10.1128/mcb.01327-13
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发表时间：
2014-05-01
影响因子：
5.3
通讯作者：
Waguri, Satoshi
中科院分区：
文献类型：
--
作者：
Uemura, Takefumi;Yamamoto, Masaya;Waguri, Satoshi
最近的研究表明，自噬隔离膜（IM）可能起源于内质网（ER）的一个域称为omegasome。然而，ER、omegasome和IM之间的形态学关系仍不清楚。在本研究中，我们发现由双FYVE结构域蛋白1（DFCP 1）阳性omegasome和IM组成的杂合结构在Atg 3缺陷的小鼠胚胎成纤维细胞（MEFs）中积累。此外，相关的光学和电子显微镜和免疫电子显微镜显示，绿色荧光蛋白（GFP）标记的DFCP 1被定位在邻近IM边缘的管状或囊状元件。通过详细的形态学分析，包括固定方法和电子断层扫描的优化，我们观察到一组薄的管状结构之间的IM边缘和ER，其中一部分是连续的IM和/或ER。在Atg 5、Atg 7或Atg 16 L1缺陷的几种细胞系和MEFs中观察到这些细管状簇的形成，但在FIP 200缺陷的细胞中没有观察到，这表明它们与自噬体形成的早期事件有关。总之，我们的研究结果表明，这些管状轮廓代表了连接ER与IM的omegasome的一部分。
Recent findings have suggested that the autophagic isolation membrane (IM) might originate from a domain of the endoplasmic reticulum (ER) called the omegasome. However, the morphological relationships between ER, omegasome, and IM remain unclear. In the present study, we found that hybrid structures composed of a double FYVE domain- containing protein 1 (DFCP1)positive omegasome and the IM accumulated in Atg3- deficient mouse embryonic fibroblasts (MEFs). Moreover, correlative light and electron microscopy and immunoelectron microscopy revealed that green fluorescent protein (GFP)- tagged DFCP1 was localized on tubular or vesicular elements adjacent to the IM rims. Through detailed morphological analyses, including optimization of a fixation method and electron tomography, we observed a cluster of thin tubular structures between the IM edges and ER, part of which were continuous with IM and/ or ER. The formation of these thin tubular clusters was observed in several cell lines and MEFs deficient for Atg5, Atg7, or Atg16L1 but not in FIP200- deficient cells, suggesting that they were relevant to the earlier events in autophagosome formation. Taken together, our findings indicate that these tubular profiles represent a part of the omegasome that links the ER with the IM.