4BBY1030 L4 Cell Biology & Neuroscience Lecture PDF

Institute of Psychology, Psychiatry and Neuroscience Dr Clemens Kiecker 4BBY1030 Cell Biology & Neuroscience Lecture 4 Neuroscience Education Cytoskeleton Learning outcomes By the end of this lecture you should be able to explain: a) the terms microtubule, microfilament, intermediate filament b) the...

Institute of Psychology, Psychiatry and Neuroscience Dr Clemens Kiecker 4BBY1030 Cell Biology & Neuroscience Lecture 4 Neuroscience Education Cytoskeleton Learning outcomes By the end of this lecture you should be able to explain: a) the terms microtubule, microfilament, intermediate filament b) the structure and polymerisation of actin and the function of myosin c) the properties of tubulin and microtubules d) how tubulin polymerises and discuss factors that affect tubulin polymerisation e) the role of the cytoskeleton in maintaining cell structure and shape, and in cell motility f) the role of motor proteins (kinesin and dynein) in organelle transport and the ATP-dependence of their action Dr Clemens Kiecker Topic title: Cell types and subcellular structures Chapter 1 Actin and microfilaments Dr Clemens Kiecker Topic title: Cell types and subcellular structures 3 Actin is found in all eukaryotic cells A – microvilli of intestinal epithelial cells (actin = red, nuclei = blue) B – smooth muscle cells C – maize epidermis D – dividing yeast cells Dr Clemens Kiecker Topic title: Cell types and subcellular structures Pollard & Earnshaw, Cell Biology, Chapter 33 4 Actin is organised in bundles or meshed networks/branched arrays Defines the shape of cells and cellular sub-structures Exerts force Cell movement Cell division Pollard & Earnshaw, Cell Biology, Chapter 33 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 5 Actin defines the shape and sub-structure of cells wild-type fruit fly eye slingshot mutant Exerts force (actin-binding proteins) Cell movement Cell division Dr Clemens Kiecker Topic title: Cell types and subcellular structures 6 Actin-based structures in motile cells Stress fibres Contractile actin-myosin bundles in the cytoplasm Lamellipodium Thin, sheet-like extension that contains dense meshwork of actin filaments Filopodia Transient finger-like protrusions that contains loose bundles of actin filaments The Cytoskeleton and Cell Migration - Actin Cytoskeleton (oeaw.ac.at) Dr Clemens Kiecker Topic title: Cell types and subcellular structures 7 Forces and dynamic shape changes: stress fibres Matsubayashi et al. (2017) Dr Clemens Kiecker Topic title: Cell types and subcellular structures 8 The actin molecule Pollard & Earnshaw, Cell Biology, Chapter 33 Dr Clemens Kiecker Topic title: Cell types and subcellular structures Most abundant protein in eukaryotic cells (approx. 15% + 10% actin-binding proteins) 375 amino acids 55 kDa monomer (G-actin) Two similar domains Binds ATP/ADP Mutations cause multiple disorders including muscular dystrophy and haemolytic anaemias 9 Dynamic polymerisation of actin filaments Dr Clemens Kiecker Topic title: Cell types and subcellular structures G-actin reversibly polymerises into doublehelical fibres = F-actin = actin filaments = microfilaments Diameter 5-8 nm Plus and minus end (pointed and barbed end) Addition of subunits can happen at both ends, but it happens faster at the barbed end; thus, individual actin molecules seem to migrate from the barbed to the pointed end = actin treadmilling ATP is hydrolysed to ADP 10 Approx. 60 actin-binding proteins regulate microfilament dynamics Dr Clemens Kiecker Topic title: Cell types and subcellular structures 11 Forces and dynamic shape changes: cell division and muscle fibres Cell division: contractile actin-myosin ring that ‘squeezes’ cells apart Actin-myosin (= actomyosin) filaments in muscle fibres Pollard & Earnshaw, Cell Biology, Chapter 33 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 12 Actomyosin in muscle contraction Light band Dark band Z disk M line Dr Clemens Kiecker Light band Z disk Topic title: Cell types and subcellular structures 13 Myosin II is a motor protein that interacts with F-actin Actin Dr Clemens Kiecker Topic title: Cell types and subcellular structures 14 Emmeline Jean Hanson – a pioneer of muscle studies at King’s Dr Clemens Kiecker Topic title: Cell types and subcellular structures 15 Chapter 2 Intermediate filaments Dr Clemens Kiecker Topic title: Cell types and subcellular structures 16 Classes of intermediate filaments Dr Clemens Kiecker Topic title: Cell types and subcellular structures 17 Keratin Dr Clemens Kiecker Topic title: Cell types and subcellular structures 18 Intermediate filaments provide support against mechanical stress Dr Clemens Kiecker Topic title: Cell types and subcellular structures 19 Mutations in keratin can cause epidermolysis bullosa (EB) Dr Clemens Kiecker Topic title: Cell types and subcellular structures 20 Nuclear lamins Control Dr Clemens Kiecker Lamin A/B knockout Topic title: Cell types and subcellular structures 21 Chapter 3 Microtubules Dr Clemens Kiecker Topic title: Cell types and subcellular structures 22 Microtubules are the main component of the mitotic spindle HeLa cell in mitosis - YouTube Pollard & Earnshaw, Cell Biology, Chapter 33 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 23 Microtubules originate in MTOCs such as the centrosome MTOC = microtubule organising centre The centrosome is a MTOC – it becomes duplicated during mitosis A significant % of cancers have abnormal centrosomes Dr Clemens Kiecker Topic title: Cell types and subcellular structures 24 Microtubules are the substrate of organelle transport and the major component of cellular cilia Pollard & Earnshaw, Cell Biology, Chapter 33 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 25 Microtubule stability is regulated by a large number of microtubule-associated proteins Pollard & Earnshaw, Cell Biology, Chapter 33 Dr Clemens Kiecker Topic title: Cell types and subcellular structures 26 Drugs can affect microtubule stability Drug Colchicine Origin Effect Application Plants (certain crocuses and Inhibits microtubule lilies) formation by binding to tubulin Treatment of gout, Behcet’s disease Nocodazole Synthetic Inhibits microtubule formation Cancer chemotherapy Taxol (commercial name: Paclitaxel, PTX) Yew tree (Taxus brevifolia) Stabilises microtubules Cancer chemotherapy Vinblastine (commercial name: Velban, VBL) Plants (Madagascan periwinkle) Inhibits microtubule formation Cancer chemotherapy Dr Clemens Kiecker Topic title: Cell types and subcellular structures Generating seedless fruit 27 Chapter 4 Motor proteins Dr Clemens Kiecker Topic title: Cell types and subcellular structures 28 Motor proteins that act on microtubules Kinesin: from minus to plus end Dynein: from plus to minus end Dr Clemens Kiecker Utilise ATP to generate kinetic energy Cargo: proteins, RNAs, vesicles, organelles etc. Topic title: Cell types and subcellular structures 29 Microtubule-based axonal transport in neurons Dr Clemens Kiecker Topic title: Cell types and subcellular structures 30 A form of dynein enables cilia to beat Pollard & Earnshaw, Cell Biology, Chapter 33 Beating cilia on epithelia (e.g. removal of mucus) Cilia as signalling antennae Cilia in sperm motility All these roles can be affected by ciliary mutations including those in ciliary dyneins à Bardet-Biedl Syndrome Dr Clemens Kiecker Topic title: Cell types and subcellular structures 31 Motor proteins that interact with actin: myosin But no motor proteins that work on intermediate filaments (at least to my knowledge…)! Why?? Dr Clemens Kiecker Topic title: Cell types and subcellular structures 32 Thank you for your attention [email protected] © King’s College London. All rights reserved