Molecular Microscopy of Membranes

septins and cytoskeletal partners

Septins

Septins are cytoskeletal filamentous proteins which are bound to the inner cell membrane and are involved in membrane remodeling processes (constriction, invagination). Septins are multi-tasking proteins and have a prominent role in cell division, neuron morphogenesis, bacterial invasion, cell motility, membrane rigidity. This “so called” fourth cytoskeletal member can make scaffolds to recruit other factors and is implicated in establishing diffusion barriers between cellular compartments. Septins interact specifically with phosphoinositides. As opposed to other cytoskeletal proteins (actin, tubulin) septins polymerize in a non-polar fashion into paired filaments. Septins further self-assemble into variable organizations (rods, filaments, rings, gauzes) both in vitro and in situ (1-3), most likely depending on the proteic content and the post-translational modification state within the septin complexes.

We focus our interest in understanding how septins from distinct organisms interact with specific partners: membrane and proteins (cytoskeletal proteins (actin) and transmembrane proteins). To this end we are using a set of complementary microscopy methods (cryo-electron microscopy, fluorescence microcopy and atomic force microscopy).

Levy33

Bertin et al. (2012), Molecular Biology of the Cell, 23(3), 423-432. Bertin et al. (2010), J. Mol. Biol., 404(4), 711-31. Bertin et al. (2008), Proc.Natl. Acac. Sci USA, 105, 8274-8279

People involved in the project

Aurélie Bertin (PI), Cyntia Taveneau (Post-Doc), Alexandre Beber (PhD student), Julien Maufront (PhD Student), Daniel Lévy (DR)

Funding :

ANR JCJC « SEPTIME » 2013-2017. ANR PRC « SEPTIMORPH » 2018-2022 as partner. ANR PRC “CONFORMIN” 2017-2021 as partner. Van Gogh French Dutch collaborative grant.

Collaborations:

Stéphanie Mangenot, Patricia Bassereau: UMR 168 (Institut Curie). Manos Mavrakis (Institut Fresnel, Marseille). Pierre-Emmanuel Milhiet (CBS, Montpellier). Gijsje Koenderink (Amolf, Amsterdam). Guillaume Romet-Lemonne, Antoine Jégou (Institut Jacques Monod, Paris)

Related publications:

Bertin A. and Nogales E., Preparing recombinant septins and their analysis by electron microscopy, 2016, Methods in cell Biology, 136, 21-34.

Bertin A. and Nogales E., Characterization of Septin Ultrastructure in Budding Yeast Using Electron Tomography, 2016, Methods in Molecular Biology, 2016, 1369, 113-23.

Mavrakis M, Azou-Gros Y, Tsai FC, Alvarado J, Bertin A, Iv F, Kress A, Brasselet S, Koenderink GH, Lecuit T, Septins cross-link, bundle and bend actin,2014, Nat Cell Biol., 16 (4), 322-334.

de Val, McMurray, Lam, Bertin, Nogales and Thorner,2013, Native Cysteine Residues are Dispensable for the Structure and Function of All Five Yeast Mitotic Septins, Proteins, structure, function and bioinformatics, 81(11):1964-79.

A.Bertin and E. Nogales (2012), Septin filament organization in Saccharomyces cerevisiae, Communicative and Integrative Biology, 5 (5)

Bertin, M. McMurray, J. Pierson, L. Thai, E. Zehr, K. McDonald, J. Thorner, E. Nogales (2012) Three-dimensional ultra-structures of the septin filament network at the bud neck of S. Cerevisiae, Molecular Biology of the Cell, 23(3), 423-432 (highlight from MBoC selection).

Garcia, A. Bertin, Zhu Yi, Yi Song, M. McMurray, S. Gradia, A. Hartland, J, Thorner, E. Nogales (2011), The regulatory budding yeast septin Shs1 promotes ring and gauze formation in a phosphorylation dependent manner., J. Cell. Biol., 195(6), 993-1004.(highlight, in focus)

McMurray, A. Bertin, G. Garcia, L. Lam, Ho Leung Ng, T. Alber, E. Nogales, J. Thorner.(2011) Plasticity in higher order assembly: evidence that the septin filaments are essential in budding yeast, Dev. Cell, 20, 540-9.

Bertin, , M. McMurray, L. Thai , G. Garcia, V. Votin, P. Grob, T. Allyn, J. Thorner, E. Nogales (2010), Phosphatydinositol 4,5 biphosphate promotes budding yeast septin filament assembly and organization, J. Mol. Biol., 404(4), 711-31.

A.Bertin, P. Grob, M. McMurray, G.Garcia, S. Park, H. Ng, T. Alber, J. Thorner, E. Nogales (2008), Saccharomyces Cerevisiae septins: supramolecular organization of heterooligomers and the mechanism of filament assembly, Proc.Natl. Acac. Sci USA, 105, 8274-8279.cité par “Faculty of 1000 biology” (score 6: must read).