BEGIN:VCALENDAR VERSION:2.0 PRODID:-//wp-events-plugin.com//6.4.7.2//EN TZID:Europe/Paris X-WR-TIMEZONE:Europe/Paris BEGIN:VEVENT UID:0-678@lptms.universite-paris-saclay.fr DTSTART:20190619T110000Z DTEND:20190619T120000Z DTSTAMP:20190527T162158Z URL:http://www.lptms.universite-paris-saclay.fr/seminars/physics-biology-i nterface-seminar-stephanie-mangenot-aurelie-bertin/ SUMMARY:Physics-Biology interface seminar: Stéphanie Mangenot &\; Auré lie Bertin - Moyen Amphi\, Building 510\, Université Paris-Saclay Orsay - 19 Juin 19 11:00 DESCRIPTION:Membrane reshaping induced by Curvature sensitive Septin filame nts: A story of paired filaments told by a pair of Orsay alumni\nStéphani e Mangenot &\; Aurélie Bertin (Institut Curie\, Paris)\nSeptins are cy toskeletal proteins that assemble into a variety of supramolecular organiz ations from paired filaments to bundles\, ring like structures or gauzes o f orthogonal filaments [1‐3]. Septins are bound to the inner plasma memb rane through specific interactions with phosphoinositides [1\,4]. Septins are essential for cell division\, participate in the formation of diffusio n barrier and might be involved in membrane deformation and rigidity. Thro ughout cell division\, septins undertake major rearrangements. Septin fila ments are first aligned toward the mother‐daughter cell axis and then ro tate to be circumferential around the constriction site.\n\nWe have shown that septins arrange differently on positive or negative curvatures using Scanning Electron Microscopy on micro‐patterned PDMS periodic undulated substrates. Besides\, this curvature preference is closely related to the ability of septins to reshape and deform membranes. Indeed\, bound to Gian t unilamellar Vesicles (GUVs)\, septins induce striking deformations with regular spikes and hollow micrometric deformations at the surface of lipos omes\, as visualized by fluorescence microscopy. Smaller vesicles (LUVs of 100‐300 nm in diameter)\, highly positively curved\, are flattened by S eptin filaments into “pancake”like objects as shown in 3D by cryo‐el ectron tomography. With the resolution of cryo‐EM and sub‐tomogram ave raging we visualize both the septin filaments and the deformed vesicles. W e propose a simple model where the filamentous properties of septins contr ol their curvature sensitivity and thus impose their orientation in situ [ 5].\n\n[1] A. Bertin\, et al. (2010)\, Phosphatydinositol 4\,5 biphosphate promotes budding yeast septin filament assembly and organization\, J. Mol . Biol.\, 404(4)\, 711‐31.\n[2] G. Garcia et al. (2011)\, The regulatory budding yeast septin Shs1 promotes ring and gauze formation in a phosphor ylation dependent manner.\, J. Cell. Biol.\, 195(6)\, 993‐1004.\n[3] A.B ertin\, et al. (2008)\, Saccharomyces Cerevisiae septins: supramolecular o rganization of heterooligomers and the mechanism of filament assembly\, Pr oc.Natl. Acac. Sci USA\, 105\, 8274‐8279\n[4] Beber A et al.\,Septin‐b ased readout of PI(4\,5)P2 incorporation into membranes of giant unilamell ar vesicles. (2018) Cytoskeleton. doi: 10.1002/cm.21480\n[5] A. Beber et a l. (2019)\, Membrane reshaping by micrometric curvature sensitive septin f ilaments\, Nat. Commun.\, 10\, 420.\n CATEGORIES:physbio,seminars LOCATION:Moyen Amphi\, Building 510\, Université Paris-Saclay Orsay\, 15 R ue Georges Clemenceau\, orsay\, France GEO:48.698187;2.181768 X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=15 Rue Georges Clemenceau\, orsay\, France;X-APPLE-RADIUS=100;X-TITLE=Moyen Amphi\, Building 510\, Un iversité Paris-Saclay Orsay:geo:48.698187,2.181768 END:VEVENT END:VCALENDAR