PG1005 Lecture 5 The Cellular Cytoskeleton Dr. Neil Docherty My Teaching Objec/ves • To outline the components of the cytoskeleton and its basic purpose • To explain the molecular composiBon of the cytoskeleton and describe its appearance on T.E.M. and fluorescence microscopy • To highlight cilia and microvilli as cytoskeletal specialisaBons and their implicaBon in specialised cellular/Bssue funcBons The Three Principal Components of the Cytoskeleton •  Microfilaments •  Intermediate Filaments •  Microtubules Microfilaments-­‐1 • Structure -­‐fine strands of acBn beads 5nm diameter -­‐Dynamic polymerisaBon and depolymerisaBon -­‐Adhere to proteins on inner side of plasma membrane -­‐In turn these adhesions are linked to the extracellular matrix academic.brooklyn.cuny.edu/. ../page/acBn.html • FuncBon -­‐Mechanosensing and mechanotransducBon -­‐Cell moBlity and contracBon -­‐Signalling pathway assembly Microfilaments on EM Intermediate Filaments • 
Structure -­‐10-­‐12nm diameter -­‐Lineage specific composiBon 1. 
cytokeraBn-­‐epithelia 2. 
desmin-­‐muscle 3. 
vimenBn-­‐mesenchymal 4. 
Neurofilament-­‐neuronal -­‐Fibrous non-­‐dynamic, non-­‐polar -­‐anchored to plasma membrane -­‐cross link to other cytoskeletal components and organelles • 
FuncBon Structural support Cell-­‐cell integrity Fluoresecent anBbody staining of cytokeraBn in kangaroo kidney www.microscopyu.com/ arBcles/fluorescence/fil.. Assembly of Intermediate Filaments • 50 kDa monomers • Coiled domains variable • Globular domains conserved • Non-­‐polar • Non-­‐dynamic Intermediate Filaments-­‐EM Transverse of nerve cell axon surrounded by Schwann cell Microtubules-­‐1 •  Structure -­‐25nm diameter tube -­‐Assembled from repeat ring assembly of 13 tubulin subunits -­‐Dynamic -­‐Grow out from the centrosome •  FuncBon -­‐SegregaBon of chromosomes during mitosis -­‐Organelle and vesicle shuUling -­‐Sensory structures (moBle and non moBle cilia) Microtubules-­‐EM Transverse Longitudinal Centrioles and Centrosome • Structure -­‐Closed cyclinder formed by 9 microtubule triplets -­‐Two per cell -­‐Long axes at right angles • FuncBon -­‐Outward growth of microtubules (aster) Centriole-­‐EM RadiaBng microtubules Cytoskeletal Specialisa/on 1:Mo/le Cilium Cytoskeletal Specialisa/on 2:Microvilli (ac/n projec/ons) Your Learning From Today Should focus on being able to; • Be proficient in navigaBng micrographs in order to idenBfy the 3 major components of the cellular cytoskeleton • Provide a basic descripBon of the molecular composiBon and funcBon of each cytoskeletal component Explain how moBle cilia and microvilli helps fulfill cell and Bssue FuncBon using the airways and gut as examples.