Cytoskeleton

• What are the three classes of cytoskeleton components?

  Actin microfilaments, intermediate filaments, microtubules
• What should you be able to explain by the end of the cytoskeleton lecture?

  • Terms: microfilament, intermediate filament, microtubule
  • Structure and polymerisation of actin and function of myosin
  • Properties of tubulin and microtubules
  • Factors affecting tubulin polymerisation
  • Role of cytoskeleton in cell structure, shape, and motility
  • Role of motor proteins (kinesin and dynein) in organelle transport
• In which types of cells is actin found?


  In all eukaryotic cells
• How is actin organized in cells?


  In bundles or meshed networks/branched arrays
• What are the functions of actin in cells?


  Defines cell shape, exerts force, enables cell movement, and aids in cell division
• What are stress fibers in motile cells?


  Contractile actin-myosin bundles in the cytoplasm
• What is a lamellipodium?


  A thin, sheet-like extension containing a dense meshwork of actin filaments
• What are filopodia?


  Transient finger-like protrusions containing loose bundles of actin filaments
• What is the most abundant protein in eukaryotic cells?

  Actin
• What is the structure of the actin molecule?


  It has 375 amino acids and two similar domains
• What happens during the dynamic polymerisation of actin filaments?


  1. actin reversibly polymerises into F-actin, forming microfilaments
• What is actin treadmilling?


  It is the process where individual actin molecules migrate from the barbed to the pointed end
• What regulates microfilament dynamics?


  Approximately 60 actin-binding proteins
• What is the role of actin-myosin in cell division?


  It forms a contractile ring that squeezes cells apart
• What is a sarcomere?


  The basic unit of contractile muscle fibers
• What are the components of a sarcomere?


  Actin and myosin
• What do intermediate filaments provide to cells?


  Stability and cohesion against stretch
• What can mutations in keratin cause?


  Epidermolysis bullosa (EB)
• What are microtubules primarily involved in?


  They are the main component of the mitotic spindle
• Where do microtubules originate?


  In microtubule organizing centers (MTOCs) such as the centrosome
• What is the effect of drugs on microtubules?


  They can affect microtubule stability
• What are the effects of different drugs on microtubules?


  • Colchicine: Inhibits microtubule formation (treatment for gout)
  • Nocodazole: Inhibits microtubule formation (cancer chemotherapy)
  • Taxol (Paclitaxel): Stabilizes microtubules (cancer chemotherapy)
  • Vinblastine: Inhibits microtubule formation (cancer chemotherapy)
• What is the role of kinesin and dynein motor proteins?


  Kinesin moves cargo from minus to plus end, while dynein moves cargo from plus to minus end
• What types of cargo do motor proteins transport?


  Proteins, RNAs, vesicles, organelles, etc.
• What is the role of dynein in cilia?


  It enables cilia to beat
• What can ciliary mutations affect?


  They can affect ciliary functions including motility and signaling
• What is the significance of Emmeline Jean Hanson in muscle studies?


  She is recognized as a pioneer of muscle studies