PDF(Pubmed)
Abstract：
Junctions between the endoplasmic reticulum (ER) and the outer membrane of the nuclear envelope (NE) physically connect both organelles. These ER-NE junctions are essential for supplying the NE with lipids and proteins synthesized in the ER. However, little is known about the structure of these ER-NE junctions. Here, we systematically study the ultrastructure of ER-NE junctions in cryo-fixed mammalian cells staged in anaphase, telophase, and interphase by correlating live cell imaging with three-dimensional electron microscopy. Our results show that ER-NE junctions in interphase cells have a pronounced hourglass shape with a constricted neck of 7-20 nm width. This morphology is significantly distinct from that of junctions within the ER network, and their morphology emerges as early as telophase. The highly constricted ER-NE junctions are seen in several mammalian cell types, but not in budding yeast. We speculate that the unique and highly constricted ER-NE junctions are regulated via novel mechanisms that contribute to ER-to-NE lipid and protein traffic in higher eukaryotes.
摘要：
内质网（ER）和核膜外膜（NE）之间的结物理连接两个细胞器。这些ER-NE连接对于向NE提供在ER中合成的脂质和蛋白质是必需的。然而,对这些ER-NE结的结构知之甚少。这里,我们系统地研究了冷冻固定的哺乳动物细胞在后期阶段的ER-NE连接的超微结构，终端，和间期通过关联活细胞成像与三维电子显微镜。我们的结果表明，间期细胞中的ER-NE连接具有明显的沙漏形，颈部狭窄，宽度为7-20nm。这种形态与ER网络中的连接处明显不同，它们的形态早在末期就出现了。在几种哺乳动物细胞类型中可以看到高度收缩的ER-NE连接，但不是在萌芽酵母中。我们推测，独特且高度收缩的ER-NE连接是通过新的机制调节的，这些机制有助于高等真核生物中ER-NE脂质和蛋白质的运输。
