title: Multiple mechanisms determine ER network morphology during the cell cycle in Xenopus egg extracts.
abstract: In metazoans the endoplasmic reticulum (ER) changes during the cell cycle, with the nuclear envelope (NE) disassembling and reassembling during mitosis and the peripheral ER undergoing extensive remodeling. Here we address how ER morphology is generated during the cell cycle using crude and fractionated Xenopus laevis egg extracts. We show that in interphase the ER is concentrated at the microtubule (MT)-organizing center by dynein and is spread by outward extension of ER tubules through their association with plus ends of growing MTs. Fusion of membranes into an ER network is dependent on the guanosine triphosphatase atlastin (ATL). NE assembly requires fusion by both ATL and ER-soluble N-ethyl-maleimide-sensitive factor adaptor protein receptors. In mitotic extracts, the ER converts into a network of sheets connected by ER tubules and loses most of its interactions with MTs. Together, these results indicate that fusion of ER membranes by ATL and interaction of ER with growing MT ends and dynein cooperate to generate distinct ER morphologies during the cell cycle.
authors.affiliation: Department of Cell Biology and Howard Hughes Medical Institute and 2 Department of Systems Biology, Harvard Medical School, Boston, MA 02115.
authors.forename: Songyu
authors.initials: S
authors.lastname: Wang
authors.forename: Fabian B
authors.initials: FB
authors.lastname: Romano
authors.forename: Christine M
authors.initials: CM
authors.lastname: Field
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Mitchison
authors.forename: Tom A
authors.initials: TA
authors.lastname: Rapoport
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002458:Cell Fractionation; D004398:Dyneins / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure*; D020558:GTP Phosphohydrolases / Q000502:physiology; D007399:Interphase; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure; D008561:Membrane Fusion; D022101:Microtubule-Organizing Center / Q000378:metabolism; D009685:Nuclear Envelope / Q000378:metabolism / Q000648:ultrastructure; D014982:Xenopus laevis
chemical_list: D020558:GTP Phosphohydrolases; D004398:Dyneins