title: Actin kinetics shapes cortical network structure and mechanics.
abstract: The actin cortex of animal cells is the main determinant of cellular mechanics. The continuous turnover of cortical actin filaments enables cells to quickly respond to stimuli. Recent work has shown that most of the cortical actin is generated by only two actin nucleators, the Arp2/3 complex and the formin Diaph1. However, our understanding of their interplay, their kinetics, and the length distribution of the filaments that they nucleate within living cells is poor. Such knowledge is necessary for a thorough comprehension of cellular processes and cell mechanics from basic polymer physics principles. We determined cortical assembly rates in living cells by using single-molecule fluorescence imaging in combination with stochastic simulations. We find that formin-nucleated filaments are, on average, 10 times longer than Arp2/3-nucleated filaments. Although formin-generated filaments represent less than 10% of all actin filaments, mechanical measurements indicate that they are important determinants of cortical elasticity. Tuning the activity of actin nucleators to alter filament length distribution may thus be a mechanism allowing cells to adjust their macroscopic mechanical properties to their physiological needs.
authors.affiliation: MRC Human Immunology Unit, Weatherall Institute for Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK.
authors.forename: Marco
authors.initials: M
authors.lastname: Fritzsche
authors.affiliation: Theoretische Physik, Universität des Saarlandes, 66041 Saarbrücken, Germany.; Institut Curie, 26 Rue d'Ulm, 75248 Paris Cedex 05, France.
authors.forename: Christoph
authors.identifier: 0000-0001-6496-6929
authors.initials: C
authors.lastname: Erlenkämper
authors.affiliation: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.; Department of Mechanical Engineering, University College London, London WC1E 7JE, UK.
authors.forename: Emad
authors.identifier: 0000-0002-7019-3907
authors.initials: E
authors.lastname: Moeendarbary
authors.affiliation: London Centre for Nanotechnology, Institute for the Physics of Living Systems, and Department of Cell and Developmental Biology, University College London, London WC1H 0AH, UK.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Charras
authors.affiliation: Theoretische Physik, Universität des Saarlandes, 66041 Saarbrücken, Germany.
authors.forename: Karsten
authors.identifier: 0000-0001-8665-2349
authors.initials: K
authors.lastname: Kruse
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000648:ultrastructure*; D051376:Actin-Related Protein 2-3 Complex / Q000737:chemistry / Q000648:ultrastructure; D000199:Actins / Q000737:chemistry / Q000648:ultrastructure*; D000577:Amides / Q000494:pharmacology; D000818:Animals; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D055595:Mechanical Phenomena; D008840:Microfilament Proteins / Q000737:chemistry; D018625:Microscopy, Atomic Force; D011725:Pyridines / Q000494:pharmacology
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D000577:Amides; D008840:Microfilament Proteins; D011725:Pyridines; C108830:Y 27632
keywords: Actin cytoskeleton; actin cortex; cell mechanics; filament lengths