Chapter 16 (Part 1) the Cytoskeleton
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The Cytoskeleton in Cell-Autonomous Immunity: Structural Determinants of Host Defence
Mostowy & Shenoy, Nat Rev Immunol, doi:10.1038/nri3877 The cytoskeleton in cell-autonomous immunity: structural determinants of host defence Serge Mostowy and Avinash R. Shenoy Medical Research Council Centre of Molecular Bacteriology and Infection (CMBI), Imperial College London, Armstrong Road, London SW7 2AZ, UK. e‑mails: [email protected] ; [email protected] doi:10.1038/nri3877 Published online 21 August 2015 Abstract Host cells use antimicrobial proteins, pathogen-restrictive compartmentalization and cell death in their defence against intracellular pathogens. Recent work has revealed that four components of the cytoskeleton — actin, microtubules, intermediate filaments and septins, which are well known for their roles in cell division, shape and movement — have important functions in innate immunity and cellular self-defence. Investigations using cellular and animal models have shown that these cytoskeletal proteins are crucial for sensing bacteria and for mobilizing effector mechanisms to eliminate them. In this Review, we highlight the emerging roles of the cytoskeleton as a structural determinant of cell-autonomous host defence. 1 Mostowy & Shenoy, Nat Rev Immunol, doi:10.1038/nri3877 Cell-autonomous immunity, which is defined as the ability of a host cell to eliminate an invasive infectious agent, is a first line of defence against microbial pathogens 1 . It relies on antimicrobial proteins, specialized degradative compartments and programmed host cell death 1–3 . Cell- autonomous immunity is mediated by tiered innate immune signalling networks that sense microbial pathogens and stimulate downstream pathogen elimination programmes. Recent studies on host– microorganism interactions show that components of the host cell cytoskeleton are integral to the detection of bacterial pathogens as well as to the mobilization of antibacterial responses (FIG. -
Soft Matter PAPER
View Article Online / Journal Homepage / Table of Contents for this issue Soft Matter Dynamic Article LinksC< Cite this: Soft Matter, 2012, 8, 7446 www.rsc.org/softmatter PAPER Growth of curved and helical bacterial cells Hongyuan Jiang and Sean X. Sun* Received 26th February 2012, Accepted 17th May 2012 DOI: 10.1039/c2sm25452b A combination of cell wall growth and cytoskeletal protein action gives rise to the observed bacterial cell shape. Aside from the common rod-like and spherical shapes, bacterial cells can also adopt curved or helical geometries. To understand how curvature in bacteria is developed or maintained, we examine how Caulobacter crescentus obtains its crescent-like shape. Caulobacter cells with or without the cytoskeletal bundle crescentin, an intermediate filament-like protein, exhibit two distinct growth modes, curvature maintenance that preserves the radius of curvature and curvature relaxation that straightens the cell (Fig. 1). Using a proposed mechanochemical model, we show that bending and twisting of the crescentin bundle can influence the stress distribution in the cell wall, and lead to the growth of curved cells. In contrast, after crescentin bundle is disrupted, originally curved cells will slowly relax towards a straight rod over time. The model is able to quantitatively capture experimentally observed curvature dynamics. Furthermore, we show that the shape anisotropy of the cross-section of a curved cell is never greater than 4%, even in the presence of crescentin. 1. Introduction forces applied by external constraints generate curved cells. Strikingly, the growth modes of the cell with or without cres- Bacterial cell walls are built through a complex biochemical centin are different17,18 as shown in Fig. -
Microtubule Nucleation Remote from Centrosomes May Explain
Microtubule nucleation remote from centrosomes may INAUGURAL ARTICLE explain how asters span large cells Keisuke Ishiharaa,b,1, Phuong A. Nguyena,b, Aaron C. Groena,b, Christine M. Fielda,b, and Timothy J. Mitchisona,b,1 aDepartment of Systems Biology, Harvard Medical School, Boston, MA 02115; and bMarine Biological Laboratory, Woods Hole, MA 02543 This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected in 2014. Edited by Ronald D. Vale, Howard Hughes Medical Institute and University of California, San Francisco, CA, and approved November 13, 2014 (received for review October 6, 2014) A major challenge in cell biology is to understand how nanometer- aster growth in large cells, such as microtubule sliding, tread- sized molecules can organize micrometer-sized cells in space and milling, or nucleation remote from centrosomes. time. One solution in many animal cells is a radial array of Previously we developed a cell-free system to reconstitute microtubules called an aster, which is nucleated by a central cleavage furrow signaling where growing asters interacted (5, organizing center and spans the entire cytoplasm. Frog (here 12). Here, we combine cell-free reconstitution and quantitative Xenopus laevis) embryos are more than 1 mm in diameter and imaging to identify microtubule nucleation away from the cen- divide with a defined geometry every 30 min. Like smaller cells, trosome as the key biophysical mechanism underlying aster they are organized by asters, which grow, interact, and move to growth. We propose that aster growth in large cells should be precisely position the cleavage planes. -
A Metabolic Assembly Line in Bacteria
NEWS AND VIEWS A metabolic assembly line in bacteria Matthew T. Cabeen and Christine Jacobs-Wagner The bacterial cytoplasm is rich in filament-forming proteins, from homologues of eukaryotic cytoskeletal elements to other scaffolding and segregation proteins. We now learn that even the metabolic enzyme CTP synthase forms cytoplasmic filaments that affect bacterial cell shape. Bacteria keep surprising us. It was not so long in mediating cell curvature in Caulobacter cres- and analysing their function later. Using high- ago that they were thought to be mere bags of centus9; subsequent characterization revealed resolution electron cryotomography (ECT), an chemicals, possessing only the cell wall as a sort its intermediate filament-like properties9. But unbiased method which uses no labels, Jensen of exoskeleton to hold everything together. As what about proteins with functions that would and colleagues uncovered several filament-like it turns out, bacterial cells have a sophisticated never suggest any polymerizing property? structures in the cytoplasm of C. crescentus internal organization. They possess counter- Recent work has approached the discovery of that could not be identified by disrupting or parts of tubulin, actin and intermediate fila- subcellular structures from the opposite direc- eliminating known cytoskeletal structures10. ment proteins, suggesting that a cytoskeleton tion by searching for filamentous structures first Meanwhile, in another unbiased approach, first evolved in bacteria. Moreover, in recent years the known bacterial filament-forming proteins have expanded beyond the traditional cytoskeleton to include DNA segregators, structural scaffolds and proteins, the function of which are still unknown. On page 739 of this TubZ issue, Ingerson-Mahar et al. -
Profilin and Formin Constitute a Pacemaker System for Robust Actin
RESEARCH ARTICLE Profilin and formin constitute a pacemaker system for robust actin filament growth Johanna Funk1, Felipe Merino2, Larisa Venkova3, Lina Heydenreich4, Jan Kierfeld4, Pablo Vargas3, Stefan Raunser2, Matthieu Piel3, Peter Bieling1* 1Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany; 2Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany; 3Institut Curie UMR144 CNRS, Paris, France; 4Physics Department, TU Dortmund University, Dortmund, Germany Abstract The actin cytoskeleton drives many essential biological processes, from cell morphogenesis to motility. Assembly of functional actin networks requires control over the speed at which actin filaments grow. How this can be achieved at the high and variable levels of soluble actin subunits found in cells is unclear. Here we reconstitute assembly of mammalian, non-muscle actin filaments from physiological concentrations of profilin-actin. We discover that under these conditions, filament growth is limited by profilin dissociating from the filament end and the speed of elongation becomes insensitive to the concentration of soluble subunits. Profilin release can be directly promoted by formin actin polymerases even at saturating profilin-actin concentrations. We demonstrate that mammalian cells indeed operate at the limit to actin filament growth imposed by profilin and formins. Our results reveal how synergy between profilin and formins generates robust filament growth rates that are resilient to changes in the soluble subunit concentration. DOI: https://doi.org/10.7554/eLife.50963.001 *For correspondence: peter.bieling@mpi-dortmund. mpg.de Introduction Competing interests: The Eukaryotic cells move, change their shape and organize their interior through dynamic actin net- authors declare that no works. -
INTERMEDIATE FILAMENT Dr Krishnendu Das Assistant Professor Department of Zoology City College
INTERMEDIATE FILAMENT Dr Krishnendu Das Assistant Professor Department of Zoology City College Q.What are the intermediate filaments? State their role as cytoskeleton. How its functional significance differs from others? This component of cytoskeleton intermediates between actin filaments (about 7 nm in diameter) and microtubules (about 25 nm in diameter). In contrast to actin filament and microtubule the intermediate filaments are not directly involved in cell movements, instead they appear to play basically a structural role by providing mechanical strength to cells and tissues. (Figure 1: Structure of intermediate filament proteins- intermediate filament proteins contain a central α-helical rod domain of approximately 310 amino acids (350 amino acids in the nuclear lamins). The N-terminal head and C-terminal tail domains vary in size and shape. Q.How intermediate filaments differ from actin filaments and microtubules in respect of their components? Actin filaments and microtubules are polymers of single types of proteins (e.g; actin tubulins), whereas intermediate filaments are composed of a variety of proteins that are expressed in different types of cells (as given in the tabular form) Type Protein Size (kd) Site of expression I Acidic keratin 40-60 Epithelial cells II Neutral or basic keratin 50-70 Do III Vimentin 54 Fibroblasts, WBC and other cell types Desmin 53 Muscle cells Periferin 57 Peripheral neurons IV Neurofilament proteins NF-L 67 Neurons NF-M 150 Neurons NF-H 200 Neurons V Nuclear lamins 60-75 Nuclear lamina of all cell types VI nestin 200 Stem cells, especially of the central nervous system Q.How do intermediate filaments assemble? (Figure 2) The central rod domains of two polypeptides wind around each other in a coiled-coil structure to form dimmers. -
Patterning and Polarization of Cells by Intracellular Flows
Author Accepted Manuscript - A published version of this article is available. Illukkumbura, R., Bland, T., and Goehring, N.W. (2020). Curr. Opin. Cell Biol. 62, 123–134. Available at: https://doi.org/10.1016/j.ceb.2019.10.005. Patterning and polarization of cells by intracellular flows Rukshala Illukkumburaa, Tom Blanda,b, Nathan W. Goehringa,b,c aThe Francis Crick Institute, London, UK bInstitute for the Physics of Living Systems, University College London, London, UK c MRC Laboratory for Molecular Cell Biology, University College London, London, UK Abstract Beginning with Turing’s seminal work [1], decades of research have demonstrated the fundamental ability of biochemical networks to generate and sustain the formation of patterns. However, it is increasingly appreciated that biochemical networks both shape and are shaped by physical and mechanical processes [2, 3, 4]. One such process is fluid flow. In many respects, the cytoplasm, membrane and actin cortex all function as fluids, and as they flow, they drive bulk transport of molecules throughout the cell. By coupling biochemical activity to long range molecular transport, flows can shape the distributions of molecules in space. Here we review the various types of flows that exist in cells, with the aim of highlighting recent advances in our understanding of how flows are generated and how they contribute to intracellular patterning processes, such as the establishment of cell polarity. (Word Count: 3200) Keywords: advection, cortical flow, membrane flow, actomyosin, cell polarity, self- organization © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ 1. -
Arxiv:1105.2423V1 [Physics.Bio-Ph] 12 May 2011 C
Cytoskeleton and Cell Motility Thomas Risler Institut Curie, Centre de Recherche, UMR 168 (UPMC Univ Paris 06, CNRS), 26 rue d'Ulm, F-75005 Paris, France Article Outline C. Macroscopic phenomenological approaches: The active gels Glossary D. Comparisons of the different approaches to de- scribing active polymer solutions I. Definition of the Subject and Its Importance VIII. Extensions and Future Directions II. Introduction Acknowledgments III. The Diversity of Cell Motility Bibliography A. Swimming B. Crawling C. Extensions of cell motility IV. The Cell Cytoskeleton A. Biopolymers B. Molecular motors C. Motor families D. Other cytoskeleton-associated proteins E. Cell anchoring and regulatory pathways F. The prokaryotic cytoskeleton V. Filament-Driven Motility A. Microtubule growth and catastrophes B. Actin gels C. Modeling polymerization forces D. A model system for studying actin-based motil- ity: The bacterium Listeria monocytogenes E. Another example of filament-driven amoeboid motility: The nematode sperm cell VI. Motor-Driven Motility A. Generic considerations B. Phenomenological description close to thermo- dynamic equilibrium arXiv:1105.2423v1 [physics.bio-ph] 12 May 2011 C. Hopping and transport models D. The two-state model E. Coupled motors and spontaneous oscillations F. Axonemal beating VII. Putting It Together: Active Polymer Solu- tions A. Mesoscopic approaches B. Microscopic approaches 2 Glossary I. DEFINITION OF THE SUBJECT AND ITS IMPORTANCE Cell Structural and functional elementary unit of all life forms. The cell is the smallest unit that can be We, as human beings, are made of a collection of cells, characterized as living. which are most commonly considered as the elementary building blocks of all living forms on earth [1]. -
Identification and Characterization of Novel Filament-Forming Proteins In
www.nature.com/scientificreports OPEN Identifcation and characterization of novel flament-forming proteins in cyanobacteria Benjamin L. Springstein 1,4*, Christian Woehle1,5, Julia Weissenbach1,6, Andreas O. Helbig2, Tal Dagan 1 & Karina Stucken3* Filament-forming proteins in bacteria function in stabilization and localization of proteinaceous complexes and replicons; hence they are instrumental for myriad cellular processes such as cell division and growth. Here we present two novel flament-forming proteins in cyanobacteria. Surveying cyanobacterial genomes for coiled-coil-rich proteins (CCRPs) that are predicted as putative flament-forming proteins, we observed a higher proportion of CCRPs in flamentous cyanobacteria in comparison to unicellular cyanobacteria. Using our predictions, we identifed nine protein families with putative intermediate flament (IF) properties. Polymerization assays revealed four proteins that formed polymers in vitro and three proteins that formed polymers in vivo. Fm7001 from Fischerella muscicola PCC 7414 polymerized in vitro and formed flaments in vivo in several organisms. Additionally, we identifed a tetratricopeptide repeat protein - All4981 - in Anabaena sp. PCC 7120 that polymerized into flaments in vitro and in vivo. All4981 interacts with known cytoskeletal proteins and is indispensable for Anabaena viability. Although it did not form flaments in vitro, Syc2039 from Synechococcus elongatus PCC 7942 assembled into flaments in vivo and a Δsyc2039 mutant was characterized by an impaired cytokinesis. Our results expand the repertoire of known prokaryotic flament-forming CCRPs and demonstrate that cyanobacterial CCRPs are involved in cell morphology, motility, cytokinesis and colony integrity. Species in the phylum Cyanobacteria present a wide morphological diversity, ranging from unicellular to mul- ticellular organisms. -
Cytoskeleton and Cell Motility Thomas Risler
Cytoskeleton and Cell Motility Thomas Risler To cite this version: Thomas Risler. Cytoskeleton and Cell Motility. Robert A. Meyers. Encyclopedia of Complexity and System Science, Springer, pp.1738-1774, 2009, 978-0-387-75888-6. 10.1007/978-0-387-30440-3_112. hal-00961037 HAL Id: hal-00961037 https://hal.archives-ouvertes.fr/hal-00961037 Submitted on 22 Mar 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Cytoskeleton and Cell Motility Thomas Risler Institut Curie, Centre de Recherche, UMR 168 (UPMC Univ Paris 06, CNRS), 26 rue d'Ulm, F-75005 Paris, France Article Outline C. Macroscopic phenomenological approaches: The active gels Glossary D. Comparisons of the different approaches to de- scribing active polymer solutions I. Definition of the Subject and Its Importance VIII. Extensions and Future Directions II. Introduction Acknowledgments III. The Diversity of Cell Motility Bibliography A. Swimming B. Crawling C. Extensions of cell motility IV. The Cell Cytoskeleton A. Biopolymers B. Molecular motors C. Motor families D. Other cytoskeleton-associated proteins E. Cell anchoring and regulatory pathways F. The prokaryotic cytoskeleton V. Filament-Driven Motility A. Microtubule growth and catastrophes B. -
Cytoskeleton UCSD
Bacterial Cytoskeletal Elements Establishment of morphogenesis in bacteria ? ? Cytoskeletal elements The bacterial cytoskeleton Eukaryotes tubulin actin IFs Bacteria FtsZ MreB Ccrp (Crescentin) 3D structures of cytoskeletal elements Phylogeny of FtsZ Tubulin ortholog FtsZ forms a ring-like structure in the cell centre Immuno-fluorescence of FtsZ (red) and DNA (green) in Bacillus subtilis E. coli: FtsZ-GFP Tubulin forms hollow tubules, while FtsZ forms single strand polymers Assembly of the divisome Cell division in Bacillus subtilis Actin Treadmilling Plasmid segregation via a double protein filament K. Gerdes, J. Pogliano Bipolar movement through search and capturing of a second plasmid ParM-Alexa 488, ParR-Alexa red D. Mullins Structures of actin-like proteins F-actin and MreB filaments MreB MreB ParM ParM MreB J. Löwe Depletion of MreB (or MreC) leads to the formation of round cells and is lethal 2 4 6 doubling times membrane-stain The depletion of MreB leads to a loss in rod- shaped cell morphology GFP-MreB: dynamc helical filaments? GFP-MreB 2D arrangement of MreB filaments 3D arrangement of MreB filaments Filament dynamics at 100 nm resolution: TIRF-SIM YFP-MreB N-SIM A. Rohrbach Model for the generation of rod shape Intermediate-Filament proteins Crescentin affects cell curvature in Caulobacter crescentus C. Jacobs-Wagner, Yale Crescentin localizes to the short axis of the cell Crescentin forms left handed helices Crescentin-YFP Deletion of IF encoding genes leads to loss of cell shape in Helicobacter pylori Ccrps (coiled coil-rich proteins) form long bundles of filaments Cell curvature through mechanical bending of cells via a rigid protein filament Positioning of magnetosomes through an actin-like protein (MamK) Spiroplasma melliferum Bacterial cytoskeletal elements Model for the function of MreB Motility of Spiroplasma Filament formation in a mammalian cell system YFP-MreB CFP-Mbl mCherry-MreBH . -
9.4 | Intermediate Filaments
354 9.4 | Intermediate Filaments The second of the three major cytoskeletal Microtubule elements to be discussed was seen in the electron microscope as solid, unbranched Intermediate filaments with a diameter of 10–12 nm. They were named in- filament termediate filaments (or IFs ). To date, intermediate filaments have only been identified in animal cells. Intermediate fila- ments are strong, flexible, ropelike fibers that provide mechani- cal strength to cells that are subjected to physical stress, Gold-labeled including neurons, muscle cells, and the epithelial cells that line anti-plectin the body’s cavities. Unlike microfilaments and microtubules, antibodies IFs are a chemically heterogeneous group of structures that, in Plectin humans, are encoded by approximately 70 different genes. The polypeptide subunits of IFs can be divided into five major classes based on the type of cell in which they are found (Table 9.2) as well as biochemical, genetic, and immunologic criteria. Figure 9.41 Cytoskeletal elements are connected to one another by We will restrict the present discussion to classes I-IV, which are protein cross-bridges. Electron micrograph of a replica of a small por- found in the construction of cytoplasmic filaments, and con- tion of the cytoskeleton of a fibroblast after selective removal of actin sider type V IFs (the lamins), which are present as part of the filaments. Individual components have been digitally colorized to assist inner lining of the nuclear envelope, in Section 12.2. visualization. Intermediate filaments (blue) are seen to be connected to IFs radiate through the cytoplasm of a wide variety of an- microtubules (red) by long wispy cross-bridges consisting of the fibrous imal cells and are often interconnected to other cytoskeletal protein plectin (green).