title: Self-organizing actin patterns shape membrane architecture but not cell mechanics.
abstract: Cell-free studies have demonstrated how collective action of actin-associated proteins can organize actin filaments into dynamic patterns, such as vortices, asters and stars. Using complementary microscopic techniques, we here show evidence of such self-organization of the actin cortex in living HeLa cells. During cell adhesion, an active multistage process naturally leads to pattern transitions from actin vortices over stars into asters. This process is primarily driven by Arp2/3 complex nucleation, but not by myosin motors, which is in contrast to what has been theoretically predicted and observed in vitro. Concomitant measurements of mechanics and plasma membrane fluidity demonstrate that changes in actin patterning alter membrane architecture but occur functionally independent of macroscopic cortex elasticity. Consequently, tuning the activity of the Arp2/3 complex to alter filament assembly may thus be a mechanism allowing cells to adjust their membrane architecture without affecting their macroscopic mechanical properties.
authors.affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK.
authors.forename: M
authors.initials: M
authors.lastname: Fritzsche
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: D
authors.initials: D
authors.lastname: Li
authors.affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK.
authors.forename: H
authors.initials: H
authors.lastname: Colin-York
authors.affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK.|Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK.
authors.forename: V T
authors.initials: VT
authors.lastname: Chang
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA.|Department of Mechanical Engineering, University College London, London WC1E 7JE, UK.
authors.forename: E
authors.initials: E
authors.lastname: Moeendarbary
authors.affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK.
authors.forename: J H
authors.initials: JH
authors.lastname: Felce
authors.affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK.
authors.forename: E
authors.identifier: 0000-0002-4915-388X
authors.initials: E
authors.lastname: Sezgin
authors.affiliation: London Centre for Nanotechnology and Department of Cell &Developmental Biology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK.
authors.forename: G
authors.initials: G
authors.lastname: Charras
authors.affiliation: Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, Virginia 20147, USA.
authors.forename: E
authors.initials: E
authors.lastname: Betzig
authors.affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK.
authors.forename: C
authors.initials: C
authors.lastname: Eggeling
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D051376:Actin-Related Protein 2-3 Complex / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D002448:Cell Adhesion; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D055595:Mechanical Phenomena; D008560:Membrane Fluidity; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D011487:Protein Conformation
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins