DOCSLIB.ORG

Cilia and Flagella: from Discovery to Disease Dylan J

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Cilia and Flagella: from Discovery to Disease Dylan J Dartmouth Undergraduate Journal of Science Volume 20 Article 2 Number 1 Assembly 2017 Cilia and Flagella: From Discovery to Disease Dylan J. Cahill Dylan Cahill, [email protected] Follow this and additional works at: https://digitalcommons.dartmouth.edu/dujs Part of the Engineering Commons, Life Sciences Commons, Medicine and Health Sciences Commons, Physical Sciences and Mathematics Commons, and the Social and Behavioral Sciences Commons Recommended Citation Cahill, Dylan J. (2017) "Cilia and Flagella: From Discovery to Disease," Dartmouth Undergraduate Journal of Science: Vol. 20 : No. 1 , Article 2. Available at: https://digitalcommons.dartmouth.edu/dujs/vol20/iss1/2 This Research Article is brought to you for free and open access by the Student-led Journals and Magazines at Dartmouth Digital Commons. It has been accepted for inclusion in Dartmouth Undergraduate Journal of Science by an authorized editor of Dartmouth Digital Commons. For more information, please contact [email protected]. BIOLOGY Cilia and Flagella: FromCilia and Discovery Flagella: to Disease From Discovery to Disease BY DYLAN CAHILL ‘18 Introduction certain insect sperm fagella (3, 5, 6). A unique Figure 1: Chlamydomonas intracellular transport mechanism known as reinhardtii, a single-celled, bi- In 1674, peering through the lens of a crude flagellate green alga, viewed intrafagellar transport is responsible for the light microscope, Antoni van Leeuwenhoek with a scanning electron assembly and maintenance of these organelles Chlamydomonas observed individual living cells for the frst time microscope. is (3, 6). Cilia and fagella are primarily composed a model organism in flagellar in history (1). He noted long, thin appendages of the protein tubulin, which polymerizes into dynamics and motility studies. protruding out of some of the otherwise globular long tracks called microtubules. However, cells that seemed to provide locomotion, like proteomic analysis, the analysis of the total “litle feet” (1, 2). Leeuwenhoek’s description of Source: Wikimedia Commons protein complement of a sample at a single time (Credit: Rippel Electron what we now know to be cilia, the frst organelle point, has revealed the presence of 600 – 1000 Microscope Facility, Dartmouth discovered, initiated centuries of research on the College) diferent polypeptides in a single fagellum (7, structure and function of this versatile organelle. 8). Cilia and fagella are hair-like organelles While many ciliary and fagellar proteins that project out from the cell surface in are known to play a structural role in the cilia eukaryotic organisms (3). Cilia come in two and fagella scafolding, known as the axoneme, varieties, motile cilia and non-motile, primary the structure and function of the majority of this cilia, and share many characteristics with diverse protein array remains unknown and is fagella. Te membranes of both cilia and an active area of research (4, 7). Recent research fagella are continuous with the cell membrane, has focused on the role cilia play in ciliopathies, but possess a distinctive lipid and protein a broad and enlarging class of diseases linked to composition (4). Most cilia and fagella are 200 defects in cilia, particularly primary cilia, as well – 300 nm in diameter and range from 1 – 5 μm as the role cilia may play in cancer progression. long for most cilia and up to more than 2 mm for FALL 2017 3 Cilia and Flagella: layer of cells; the mechanism by which cilia and The Dividing Line fagella generate propulsion also varies such that fagella primarily beat in a regular sine Cilia and fagella are so similar in terms wave motion while cilia move by a “power and of structure and function that the terms are recovery stroke” in much the same way that a ofen used interchangeably (4, 7). Structurally, swimmer’s arm generates thrust. Unlike fagella, cilia and fagella are identical; a cross section primary cilia are found on nearly all vertebrate of either organelle reveals the same ordered cells (8). arrangement of proteins in the axoneme, which is highly conserved across species (8). Te More than Movement following generalizations highlight their few distinguishing characteristics: cells typically A critical distinction within cilia is that have few, long fagella or many short cilia; between motile cilia and primary cilia, which fagella function to propel a cell through a liquid difer both structurally and functionally. medium whereas cilia, in addition to propelling Te structural component of motile cilia, some cell types through a liquid medium, the axoneme, has a “9+2” arrangement of function to propel fuid across a stationary microtubules in which 9 pairs of microtubule Figure 2: Primary cilium structure. a. Transmission electron microscopy of a primary cilium. b. Schematic of intraflagellar transport. c. Cross section of motile cilium with 9+2 microtubule arrangement and dynein arms. d. Cross section of primary cilium with 9+0 microtubule arrangement. Source: Waters, A. M., & Beales, P. L. (2011). Ciliopathies: An expanding disease spectrum. Pediatric Nephrology, 26(7), 1039-1056. doi: 10.1007/s00467-010-1731- 7. Reprinted with permission. 4 DARTMOUTH UNDERGRADUATE JOURNAL OF SCIENCE doublets surround a central pair of microtubule much of the material is applicable to motile cilia Figure 3: The four stages of singlets, as shown in Figure 2 (8). Motile cilia, also and fagella as well. primary cilia assembly. called secondary cilia, are capable of rhythmic movements that provide propulsion, such as Four-Stage Assembly Source: Pedersen, L. B., Veland, I. R., Schrøder J. M., in protists or spermatozoa, and function in the Primary cilia are assembled in four main passage of fuid over a stationary membrane, & Christensen, S. T. (2008). stages, according to the hypothesis illustrated Assembly of primary cilia. such as in the epithelia of the respiratory tract (6, in Figure 3 (10). In stage one, a membrane- Developmental Dynamics, 9). Underlying this motion are arms composed bound vesicle within the cell buds of the Golgi 237(8), 1993-2006. doi: of the motor protein dynein. Every motile cilium 10.1002/dvdy.21521. Reprinted apparatus, an organelle composed of layers of with permission. contains thousands of dynein proteins, each of membrane sacks that is involved in protein which is fxed in place on one end and free to packaging and modifcation. Tis vesicle merges walk a short distance along microtubule tracks with a centriole, a cylindrical organelle also at the other end. Tis structural arrangement of composed of microtubules, but in a triplet, not the axoneme gives cells the ability to coordinate a doublet, array, to form the centriolar vesicle. the walking of thousands of dynein proteins Te membrane-associated centriole, designated over short distances along the length of the as the “mother centriole,” forms the base of cilia. Te summation of this process generates the growing cilium (10). Te mother centriole “More recent bending and rhythmic beating (4, 8). begins to grow into the centriolar vesicle, which experimentation Primary cilia are non-motile organelles wraps around the centriole much like a partially found in most non-dividing vertebrate cells (2, and research defated balloon wraps around a fst pressed into has revealed that 8). Primary cilia lack dynein motor proteins and it. other structural features common to motile cilia, In stage two, the centriolar vesicle and primary cilia play such as the central pair of singlet microtubules, mother centriole migrate together toward the critical roles in and are therefore classifed as having a “9+0” cell membrane. Meanwhile, additional smaller arrangement of microtubules, also demonstrated diverse signaling vesicles called secondary centriolar vesicles pathways both in Figure 2. Because primary cilia are incapable fuse with the primary centriolar vesicle. Te of motion, some researchers initially concluded rudimentary axoneme growing out of the during development that primary cilia were merely vestigial mother centriole continues to grow rapidly and in maintaining structures (2). More recent experimentation through polymerization of tubulin at its tip. Te homeostasis.” and research has revealed that primary cilia extent to which cilium growth occurs during play critical roles in diverse signaling pathways transport before docking with the membrane both during development and in maintaining remains unknown (10). homeostasis (2). Primary cilia are optimized for In stage three, the centriolar vesicle fuses this signaling role via their unique, high-density with the cell membrane. Here, the nomenclature arrangement of receptors and ion channels changes and the mother centriole now becomes (2). Because of the growing interest in the link known as the basal body, the organelle at the between primary cilia and disease, the remainder base of the cilium (10). of this article focuses on primary cilia, although Finally, in stage four the primary cilium FALL 2017 5 is elongated and maintained by intrafagellar the microtubule-based axoneme in a particular transport, as discussed in the following section. direction. Microtubules have polarity inherent to their structure, which gives them a head or The Intraflagellar Transport Train “plus end” and tail or “minus end.” Kinesin-II and In the 1990s, advances in light microscopy OSM-3 are plus-end directed motor proteins that “IFT serves this transport proteins away from the cell body to function as a facilitated the discovery at Yale University of intrafagellar transport (IFT), a revolutionary the tip of the cilium in the anterograde direction bidirectional transport mechanism unique to cilia and fagella (7, 12). Cytoplasmic dynein (a version diferent transport system, (7, 11). Given that the proteins comprising the than the dynein atached to the outer doublets) moving protein axoneme of cilia and fagella are synthesized is a minus-end directed motor protein that transports proteins from the tip of the cilium to complexes from the in the cell body but assemble at the tip, the tip gets further away from the cell as the the cell body in the retrograde direction. Early base of the cilium fagellum grows.
Load more

Recommended publications
  • Bacterial Cell Membrane
    BACTERIAL CELL MEMBRANE Dr. Rakesh Sharda Department of Veterinary Microbiology NDVSU College of Veterinary Sc. & A.H., MHOW CYTOPLASMIC MEMBRANE ➢The cytoplasmic membrane, also called a cell membrane or plasma membrane, is about 7 nanometers (nm; 1/1,000,000,000 m) thick. ➢It lies internal to the cell wall and encloses the cytoplasm of the bacterium. ➢It is the most dynamic structure of a prokaryotic cell. Structure of cell membrane ➢The structure of bacterial plasma membrane is that of unit membrane, i.e., a fluid phospholipid bilayer, composed of phospholipids (40%) and peripheral and integral proteins (60%) molecules. ➢The phospholipids of bacterial cell membranes do not contain sterols as in eukaryotes, but instead consist of saturated or monounsaturated fatty acids (rarely, polyunsaturated fatty acids). ➢Many bacteria contain sterol-like molecules called hopanoids. ➢The hopanoids most likely stabilize the bacterial cytoplasmic membrane. ➢The phospholipids are amphoteric molecules with a polar hydrophilic glycerol "head" attached via an ester bond to two non-polar hydrophobic fatty acid tails. ➢The phospholipid bilayer is arranged such that the polar ends of the molecules form the outermost and innermost surface of the membrane while the non-polar ends form the center of the membrane Fluid mosaic model ➢The plasma membrane contains proteins, sugars, and other lipids in addition to the phospholipids. ➢The model that describes the arrangement of these substances in lipid bilayer is called the fluid mosaic model ➢Dispersed within the bilayer are various structural and enzymatic proteins, which carry out most membrane functions. ➢Some membrane proteins are located and function on one side or another of the membrane (peripheral proteins).
    [Show full text]
  • 하구 및 연안생태학 Estuarine and Coastal Ecology
    하구 및 연안생태학 Estuarine and coastal ecology 2010 년 11월 2 계절적 변동 • 빛과 영양염분의 조건에 따라 • 봄 가을 대발생 계절적 변동 Sverdrup 에 의한 대발생 모델 • Compensation depth (보상심도) • Critical depth (임계수심) Sverdrup 에 의한 대발생 모델 홍재상외, 해양생물학 Sverdrup 에 의한 대발생 모델 봄 여름 가을 겨울 수심 혼합수심 임계수심 (mixed layer depth) (critical depth) Sverdrup 에 의한 대발생 모델 봄 여름 가을 겨울 수심 혼합수심 임계수심 (mixed layer depth) (critical depth) Diatoms (규조류) • Bacillariophyceae (1 fragment of centrics, 19 fragments of pennates in Devonian marble in Poland Kwiecinska & Sieminska 1974) Diatoms (규조류) • Bacillariophyceae • Temperate and high latitude (everywhere) Motility: present in pennate diatoms with a raphe (and male gametes) Resting cells (spores): heavily silicified, often with spines (Î보충설명) Biotopes: marine and freshwater, plankton, benthos, epiphytic, epizooic (e.g., on whales, crustaceans) endozoic, endophytic, discolouration of arctic and Antarctic sea ice Snow Algae (규조류 아님) Snow algae describes cold-tolerant algae and cyanobacteria that grow on snow and ice during alpine and polar summers. Visible algae blooms may be called red snow or watermelon snow. These extremophilic organisms are studied to understand the glacial ecosystem. Snow algae have been described in the Arctic, on Arctic sea ice, and in Greenland, the Antarctic, Alaska, the west coast, east coast, and continental divide of North America, the Himalayas, Japan, New Guinea, Europe (Alps, Scandinavia and Carpathians), China, Patagonia, Chile, and the South Orkney Islands. Diatoms (규조류) • Bacillariophyceae • Temperate and high latitude (everywhere) • 2~1000 um • siliceous frustules • Various patterns in frustule Centric vs Pennate Centric diatom Pennete small discoid plastid large plate plastid Navicula sp.
    [Show full text]
  • Size Changes in Eukaryotic Ribosomes
    Proc. Nat. Acad. Sci. USA Vol. 68, No. 12, pp. 3021-3025, December 1971 Size Changes in Eukaryotic Ribosomes (diffusion constant/sedimentation constant/ribosomal dissociation/chick embryo) JOHN VOURNAKIS AND ALEXANDER RICH Department of Biology, Massachusetts Institute of Technology, Cambridge, Mass. 02139 Contributed by Alexander Rich, September 20, 1971 ABSTRACT Evidence is presented that ribosomes two particles are similar. However, these changes suggest active in protein synthesis and attached to messenger that when the ribosome is attached to messenger RNA it has a RNA on polysomes have a smaller diameter than free cytoplasmic single ribosomes. Measurements have been smaller diameter than is found for the free cytoplastic ribo- made on these two types of ribosomes of differences in some. This more compact form of the ribosome is maintained sedimentation velocity and diffusion constant. Differences even when the nascent polypeptide chain is relased by puro- in these quantities suggest about a 20-A decrease in the mycin. We thus infer that there are substantial differences diameter of the ribosomes from chick embryo muscles in the interactions between the ribosomal subunits when when they are attached to messenger RNA. Similar dif- they ferences are also observed in rabbit reticulocytes and are attached to messenger RNA as compared to the free cyto- mouse ascites tumor cells. These two ribosomal states plasmic single ribosome, which is inactive in protein synthesis. have different sensitivity to Pronase digestion and dis- sociate into ribosomal subunits at different KCI concen- METHODS AND MATERIALS trations. This size difference is not associated with a sig- nificant difference in overall ribosomal mass and appears Preparation of Ribosomes.
    [Show full text]
  • Swimming with Protists: Perception, Motility and Flagellum Assembly
    REVIEWS Swimming with protists: perception, motility and flagellum assembly Michael L. Ginger*, Neil Portman‡ and Paul G. McKean* Abstract | In unicellular and multicellular eukaryotes, fast cell motility and rapid movement of material over cell surfaces are often mediated by ciliary or flagellar beating. The conserved defining structure in most motile cilia and flagella is the ‘9+2’ microtubule axoneme. Our general understanding of flagellum assembly and the regulation of flagellar motility has been led by results from seminal studies of flagellate protozoa and algae. Here we review recent work relating to various aspects of protist physiology and cell biology. In particular, we discuss energy metabolism in eukaryotic flagella, modifications to the canonical assembly pathway and flagellum function in parasite virulence. Protists The canonical ‘9+2’ microtubule axoneme is the prin- of inherited pathologies (or ciliopathies), including Eukaryotes that cannot be cipal feature of many motile cilia and flagella and is infertility, chronic respiratory disease, polycystic kid- classified as animals, fungi or one of the most iconic structures in cell biology. The ney disease and syndromes that include Bardet–Biedl, plants. The kingdom Protista origin of the eukaryotic flagellum and cilium is ancient Alstrom and Meckel syndrome6–12. Even illnesses such includes protozoa and algae. and predates the radiation, over 800 million years ago, as cancer, diabetes and obesity have been linked to cili- 1 6 Ciliates of the lineages that gave rise to extant eukaryotes . ary defects . The biological basis for some ciliopathies A ubiquitous group of protists, Therefore the absence of cilia and flagella from yeast, is undoubtedly defective sensing (an essential function members of which can be many fungi, red algae and higher plants are all examples provided by cilia), rather than defects in the assembly found in many wet of secondary loss.
    [Show full text]
  • Ciliary Chemosensitivity Is Enhanced by Cilium Geometry and Motility
    bioRxiv preprint doi: https://doi.org/10.1101/2021.01.13.425992; this version posted January 14, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. Ciliary chemosensitivity is enhanced by cilium geometry and motility David Hickey,1 Andrej Vilfan,1, 2, ∗ and Ramin Golestanian1, 3 1Max Planck Institute for Dynamics and Self-Organization (MPIDS), 37077 G¨ottingen,Germany 2JoˇzefStefan Institute, 1000 Ljubljana, Slovenia 3Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, United Kingdom (Dated: January 13, 2021) Cilia are hairlike organelles involved in both sensory functions and motility. We discuss the question of whether the location of chemical receptors on cilia provides an advantage in terms of sensitivity. Using a simple advection-diffusion model, we compute the capture rates of diffusive molecules on a cilium. Because of its geometry, a non-motile cilium in a quiescent fluid has a capture rate equivalent to a circular absorbing region with ∼ 4× its surface area. When the cilium is exposed to an external shear flow, the equivalent surface area increases to ∼ 10×. Alternatively, if the cilium beats in a non-reciprocal way, its capture rate increases with the beating frequency to the power of 1=3. Altogether, our results show that the protruding geometry of a cilium could be one of the reasons why so many receptors are located on cilia. They also point to the advantage of combining motility with chemical reception.
    [Show full text]
  • Unfolding the Secrets of Coral–Algal Symbiosis
    The ISME Journal (2015) 9, 844–856 & 2015 International Society for Microbial Ecology All rights reserved 1751-7362/15 www.nature.com/ismej ORIGINAL ARTICLE Unfolding the secrets of coral–algal symbiosis Nedeljka Rosic1, Edmund Yew Siang Ling2, Chon-Kit Kenneth Chan3, Hong Ching Lee4, Paulina Kaniewska1,5,DavidEdwards3,6,7,SophieDove1,8 and Ove Hoegh-Guldberg1,8,9 1School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia; 2University of Queensland Centre for Clinical Research, The University of Queensland, Herston, Queensland, Australia; 3School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland, Australia; 4The Kinghorn Cancer Centre, Garvan Institute of Medical Research, Sydney, New South Wales, Australia; 5Australian Institute of Marine Science, Townsville, Queensland, Australia; 6School of Plant Biology, University of Western Australia, Perth, Western Australia, Australia; 7Australian Centre for Plant Functional Genomics, The University of Queensland, St Lucia, Queensland, Australia; 8ARC Centre of Excellence for Coral Reef Studies, The University of Queensland, St Lucia, Queensland, Australia and 9Global Change Institute and ARC Centre of Excellence for Coral Reef Studies, The University of Queensland, St Lucia, Queensland, Australia Dinoflagellates from the genus Symbiodinium form a mutualistic symbiotic relationship with reef- building corals. Here we applied massively parallel Illumina sequencing to assess genetic similarity and diversity among four phylogenetically diverse dinoflagellate clades (A, B, C and D) that are commonly associated with corals. We obtained more than 30 000 predicted genes for each Symbiodinium clade, with a majority of the aligned transcripts corresponding to sequence data sets of symbiotic dinoflagellates and o2% of sequences having bacterial or other foreign origin.
    [Show full text]
  • Flagellum Couples Cell Shape to Motility in Trypanosoma Brucei
    Flagellum couples cell shape to motility in Trypanosoma brucei Stella Y. Suna,b,c, Jason T. Kaelberd, Muyuan Chene, Xiaoduo Dongf, Yasaman Nematbakhshg, Jian Shih, Matthew Doughertye, Chwee Teck Limf,g, Michael F. Schmidc, Wah Chiua,b,c,1, and Cynthia Y. Hef,h,1 aDepartment of Bioengineering, James H. Clark Center, Stanford University, Stanford, CA 94305; bDepartment of Microbiology and Immunology, James H. Clark Center, Stanford University, Stanford, CA 94305; cSLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025; dDepartment of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030; eVerna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030; fMechanobiology Institute, National University of Singapore, Singapore 117411; gDepartment of Mechanical Engineering, National University of Singapore, Singapore 117575; and hDepartment of Biological Sciences, Center for BioImaging Sciences, National University of Singapore, Singapore 117543 Contributed by Wah Chiu, May 17, 2018 (sent for review December 29, 2017; reviewed by Phillipe Bastin and Abraham J. Koster) In the unicellular parasite Trypanosoma brucei, the causative Cryo-electron tomography (cryo-ET) allows us to view 3D agent of human African sleeping sickness, complex swimming be- supramolecular details of biological samples preserved in their havior is driven by a flagellum laterally attached to the long and proper cellular context without chemical fixative and/or metal slender cell body. Using microfluidic assays, we demonstrated that stain. However, samples thicker than 1 μm are not accessible to T. brucei can penetrate through an orifice smaller than its maxi- cryo-ET because at typical accelerating voltages (≤300 kV), few mum diameter.
    [Show full text]
  • Construction and Loss of Bacterial Flagellar Filaments
    biomolecules Review Construction and Loss of Bacterial Flagellar Filaments Xiang-Yu Zhuang and Chien-Jung Lo * Department of Physics and Graduate Institute of Biophysics, National Central University, Taoyuan City 32001, Taiwan; [email protected] * Correspondence: [email protected] Received: 31 July 2020; Accepted: 4 November 2020; Published: 9 November 2020 Abstract: The bacterial flagellar filament is an extracellular tubular protein structure that acts as a propeller for bacterial swimming motility. It is connected to the membrane-anchored rotary bacterial flagellar motor through a short hook. The bacterial flagellar filament consists of approximately 20,000 flagellins and can be several micrometers long. In this article, we reviewed the experimental works and models of flagellar filament construction and the recent findings of flagellar filament ejection during the cell cycle. The length-dependent decay of flagellar filament growth data supports the injection-diffusion model. The decay of flagellar growth rate is due to reduced transportation of long-distance diffusion and jamming. However, the filament is not a permeant structure. Several bacterial species actively abandon their flagella under starvation. Flagellum is disassembled when the rod is broken, resulting in an ejection of the filament with a partial rod and hook. The inner membrane component is then diffused on the membrane before further breakdown. These new findings open a new field of bacterial macro-molecule assembly, disassembly, and signal transduction. Keywords: self-assembly; injection-diffusion model; flagellar ejection 1. Introduction Since Antonie van Leeuwenhoek observed animalcules by using his single-lens microscope in the 18th century, we have entered a new era of microbiology.
    [Show full text]
  • Cell Membrane
    John Lenyo Corrina Perez Hazel Owens Cell Membrane http://micro.magnet.fsu.edu/cells/plasmamembrane/plasmamembrane.html • Cell membranes are composed of proteins and lipids. • Since they are made up of mostly lipids, only certain substances can move through. spmbiology403.blogspot.com •Phospholipids are the most abundant type of lipid found in the membrane. Phospholipids are made up of two layers, the outer and inner layers. The inside layer is made of hydrophobic fatty acid tails, while the outer layer is made up of hydrophilic polar heads that are pointed toward the water. academic.brooklyn.cuny.edu •Membrane structure relies on the tendency of fatty acid molecules to spread on the surface of water. • Membrane proteins (which take up half of the membrane) determine what gets into and leaves the cell. •Glycolipids are found on the outer part of the cell membrane. Single Chain vs. Phospholipid • Single chain lipids were assumed to be the first of those to form cell membranes with the more complex phospholipids evolving later • Phospholipids can be synthesized in an abiotic environment without enzymes now • Phosphoplipid bilayers now make up the plasma cell membranes that regulate movement into and out of prokaryotic and eukaryotic cells. Single chain lipid http://web.nestucca.k12.or.us/nvhs/staff/whitehead/homewor http://clincancerres.aacrjournals.org/content/11/5/2018/F1. k.htm expansion Types of Lipids • Today Plasma Membranes are made primarily of phospholipids • It is thought that early membranes may have been made of simpler fatty acids. http://exploringorigins.org/fattyacids.html Properties of Fatty Acids • They are Ampipathic, meaning that they have a hydrophobic (“water hating”) end and a hydrophilic (water loving”) end.
    [Show full text]
  • Essential Function of the Alveolin Network in the Subpellicular
    RESEARCH ARTICLE Essential function of the alveolin network in the subpellicular microtubules and conoid assembly in Toxoplasma gondii Nicolo` Tosetti1, Nicolas Dos Santos Pacheco1, Eloı¨se Bertiaux2, Bohumil Maco1, Lore` ne Bournonville2, Virginie Hamel2, Paul Guichard2, Dominique Soldati-Favre1* 1Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland; 2Department of Cell Biology, Sciences III, University of Geneva, Geneva, Switzerland Abstract The coccidian subgroup of Apicomplexa possesses an apical complex harboring a conoid, made of unique tubulin polymer fibers. This enigmatic organelle extrudes in extracellular invasive parasites and is associated to the apical polar ring (APR). The APR serves as microtubule- organizing center for the 22 subpellicular microtubules (SPMTs) that are linked to a patchwork of flattened vesicles, via an intricate network composed of alveolins. Here, we capitalize on ultrastructure expansion microscopy (U-ExM) to localize the Toxoplasma gondii Apical Cap protein 9 (AC9) and its partner AC10, identified by BioID, to the alveolin network and intercalated between the SPMTs. Parasites conditionally depleted in AC9 or AC10 replicate normally but are defective in microneme secretion and fail to invade and egress from infected cells. Electron microscopy revealed that the mature parasite mutants are conoidless, while U-ExM highlighted the disorganization of the SPMTs which likely results in the catastrophic loss of APR and conoid. Introduction *For correspondence: Toxoplasma gondii belongs to the phylum of Apicomplexa that groups numerous parasitic protozo- Dominique.Soldati-Favre@unige. ans causing severe diseases in humans and animals. As part of the superphylum of Alveolata, the ch Apicomplexa are characterized by the presence of the alveoli, which consist in small flattened single- membrane sacs, underlying the plasma membrane (PM) to form the inner membrane complex (IMC) Competing interest: See of the parasite.
    [Show full text]
  • Cell Wall Constrains Lateral Diffusion of Plant Plasma-Membrane Proteins
    Cell wall constrains lateral diffusion of plant SEE COMMENTARY plasma-membrane proteins Alexandre Martinièrea, Irene Lavagia, Gayathri Nageswarana, Daniel J. Rolfeb, Lilly Maneta-Peyretc, Doan-Trung Luud, Stanley W. Botchwayb, Stephen E. D. Webbb, Sebastien Mongrandc, Christophe Maureld, Marisa L. Martin-Fernandezb, Jürgen Kleine-Vehne, Jirí Frimlf, Patrick Moreauc, and John Runionsa,1 aDepartment of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom; bCentral Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, United Kingdom; cLaboratoire de Biogenèse Membranaire, Unité Mixte de Recherche 5200 Centre National de la Recherche Scientifique, Université Bordeaux Segalen, 33076 Bordeaux, France; dLaboratoire de Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des Plantes, Unité Mixte de Recherche 5004, Centre National de la Recherche Scientifique/Unité Mixte de Recherche 0386 Institut National de la Recherche Agronomique, 34060 Montpellier, France; eDepartment of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, 1190 Vienna, Austria; and fDepartment of Plant Biotechnology and Genetics, Ghent University, 9052 Ghent, Belgium Edited by Daniel J. Cosgrove, Pennsylvania State University, University Park, PA, and approved May 16, 2012 (received for review February 3, 2012) A cell membrane can be considered a liquid-phase plane in which yeast lines lacking
    [Show full text]
  • Introduction to Bacteriology and Bacterial Structure/Function
    INTRODUCTION TO BACTERIOLOGY AND BACTERIAL STRUCTURE/FUNCTION LEARNING OBJECTIVES To describe historical landmarks of medical microbiology To describe Koch’s Postulates To describe the characteristic structures and chemical nature of cellular constituents that distinguish eukaryotic and prokaryotic cells To describe chemical, structural, and functional components of the bacterial cytoplasmic and outer membranes, cell wall and surface appendages To name the general structures, and polymers that make up bacterial cell walls To explain the differences between gram negative and gram positive cells To describe the chemical composition, function and serological classification as H antigen of bacterial flagella and how they differ from flagella of eucaryotic cells To describe the chemical composition and function of pili To explain the unique chemical composition of bacterial spores To list medically relevant bacteria that form spores To explain the function of spores in terms of chemical and heat resistance To describe characteristics of different types of membrane transport To describe the exact cellular location and serological classification as O antigen of Lipopolysaccharide (LPS) To explain how the structure of LPS confers antigenic specificity and toxicity To describe the exact cellular location of Lipid A To explain the term endotoxin in terms of its chemical composition and location in bacterial cells INTRODUCTION TO BACTERIOLOGY 1. Two main threads in the history of bacteriology: 1) the natural history of bacteria and 2) the contagious nature of infectious diseases, were united in the latter half of the 19th century. During that period many of the bacteria that cause human disease were identified and characterized. 2. Individual bacteria were first observed microscopically by Antony van Leeuwenhoek at the end of the 17th century.
    [Show full text]