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bioRxiv · 10.1101/2023.01.31.526419

The junctions connecting the endoplasmic reticulum to the nuclear envelope are constricted and remodelled during the cell cycle

Bragulat-Teixidor, H.·Ishihara, K.·Szucs, G. M.·Otsuka, S.
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Abstract

The endoplasmic reticulum (ER) is physically connected to the nucleus by junctions with the outer membrane of the nuclear envelope (NE). The 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 studied 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. Strikingly, our results revealed 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 among the ER, and it 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.

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Bragulat-Teixidor, H., Ishihara, K., Szucs, G. M., Otsuka, S.. 2023-02-01. The junctions connecting the endoplasmic reticulum to the nuclear envelope are constricted and remodelled during the cell cycle. https://doi.org/10.1101/2023.01.31.526419

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