{Reference Type}: Journal Article
{Title}: The endoplasmic reticulum connects to the nucleus by constricted junctions that mature after mitosis.
{Author}: Bragulat-Teixidor H;Ishihara K;Szücs GM;Otsuka S;
{Journal}: EMBO Rep
{Volume}: 25
{Issue}: 7
{Year}: 2024 Jul 14
{Factor}: 9.071
{DOI}: 10.1038/s44319-024-00175-w
{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.