Section 7 - CBLG311 S2016 - cytoskeleton .pptx - THE...

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THE CYTOSKELETONCHAPTER 161
LECTURE SECTION: THE CYTOSKELETON21. Cytoskeleton types and propertiesActinMicrotubules2. Cytoskeletal functionsStatic and dynamic functions3. Cytoskeletal filaments and protofilamentsSubunit interactionsNucleation4. Cytoskeletal StructureG-actin and F-actinTubulin and Microtubules5.Filament polymerization and depolymerization ratesRatesCritical concentrationPlus and minus end behaviour & kineticsNucleotide-binding TreadmillingDynamic Instability 6. Motor ProteinsMyosins, Kinesins and DyneinsCoupling ATP-hydrolysis to movementMuscle organizationIntracellular organelle movement7. Cytoskeletal RegulationSee Panel 16.3NucleationCytoskeletal binding proteins8. Cytoskeletal higher-order structuresBundlingCross-linking
3Types of Cytoskeleton: Actin FilamentsActin filament (microfilament):2-stranded helical non-covalent polymer of globular (G-actin) actin5-9 nm in diameterLinear bundles, 2-D and 3-D networksCell shapeCell movement and force
4Types of Cytoskeleton: MicrotubulesMicrotubules:Cylindrical non-covalent polymer of tubulinOriginate from the microtubule-organizing center (MTOC)Cell shape and movementCell divisionMembrane trafficking and intracellular distribution of organelles
5Cytoskeletal functions in:1. Dynamic processes (undergo rapid changes):Cell motilityPhagocytosisCell divisionCell contraction Intracellular transport2. Static processes (undergo very slow changes):Epithelium tissueNeuronal networksNuclear envelopeCytoskeleton is dynamic and adaptable
6Cytoskeletal changes during cell divisionRed = actinGreen = microtubules1. Actin filaments form the contractile ring that splits the cell in cytokinesis2. Microtubules form the mitotic spindle that separates chromosomes during mitosisWhen cells enter cell cycle:
7Cytoskeletal functions in:1. Dynamic processes (undergo rapid changes):Cell motilityPhagocytosisCell divisionCell contraction Intracellular transport2. Static processes (undergo very slow changes):Epithelium tissueNeuronal networksNuclear envelope
8Epithelium: Stable and strong cytoskeleton networkActin = forms microvilli that increase surface area of cells and stabilize tight junctionsMicrotubules = form “transport” tracks from one end to the other in epithelial cellsIntermediate filaments = stabilize cell connections called desmosomes
9Cytoskeleton: dynamic, rapid changes e.g.: phagocytosisCytoskeleton: slow, lasting structurese.g. epitheliumSame type of cytoskeleton in both cases! So, how can this be?Cytoskeleton is not cement! It is dynamic – maintain or change size, stability, strength, etcHow? Because they are made of subunit building blocks
10Cytoskeletal filaments are built from monomer protein subunitsAssembly and disassembly of filaments is regulatedHeld by non-covalent bondsunlike polymers like nucleic acids(however note that each “building block” is itself a protein)
Fig. 16-7

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