title: A minimal system allowing tubulation with molecular motors pulling on giant liposomes.
abstract: The elucidation of physical and molecular mechanisms by which a membrane tube is generated from a membrane reservoir is central to the understanding of the structure and dynamics of intracellular organelles and of transport intermediates in eukaryotic cells. Compelling evidence exists that molecular motors of the dynein and kinesin families are involved in the tubulation of organelles. Here, we show that lipid giant unilamellar vesicles (GUVs), to which kinesin molecules have been attached by means of small polystyrene beads, give rise to membrane tubes and to complex tubular networks when incubated in vitro with microtubules and ATP. Similar tubes and networks are obtained with GUVs made of purified Golgi lipids, as well as with Golgi membranes. No tube formation was observed when kinesins were directly bound to the GUV membrane, suggesting that it is critical to distribute the load on both lipids and motors by means of beads. A kinetic analysis shows that network growth occurs in two phases: a phase in which membrane-bound beads move at the same velocity than free beads, followed by a phase in which the tube growth rate decreases and strongly fluctuates. Our work demonstrates that the action of motors bound to a lipid bilayer is sufficient to generate membrane tubes and opens the way to well controlled experiments aimed at the understanding of basic mechanisms in intracellular transport.
authors.affiliation: Laboratoire Mécanismes Moléculaires du Transport Intracellulaire, Unité Mixte de Recherche 144 Centre National de la Recherche Scientifique/Institut Curie, 26 Rue d'Ulm, 75248 Paris Cedex 05, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Roux
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cappello
authors.forename: Jean
authors.initials: J
authors.lastname: Cartaud
authors.forename: Jacques
authors.initials: J
authors.lastname: Prost
authors.forename: Bruno
authors.initials: B
authors.lastname: Goud
authors.forename: Patricia
authors.initials: P
authors.lastname: Bassereau
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D019921:Biotinylation; D004331:Drosophila melanogaster; D006056:Golgi Apparatus / Q000737:chemistry*; D016547:Kinesins / Q000737:chemistry*; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008099:Liver / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D051381:Rats; D013997:Time Factors
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D000255:Adenosine Triphosphate; D016547:Kinesins