Intermediate filaments

• What do intermediate filaments do (basic)?

  Strong, flexible, and unbranched fibers that provide mechanical strength to cells such as neurons, muscle cells, and epithelial cells.
• What does it mean when intermediate filaments are described as chemically heterogeneous?

  There is no consistent protein that makes up intermediate filaments; intermediate filaments in different parts of the body are made up of different proteins
• How are intermediate filaments assembled?

  1. Monomers of intermediate filament combine to make a dimer
  2. Two dimers combine in opposite directs to make a tetramer with no direction
  3. Eight tetramers combine to make an intermediate filament
  4. Dynamic remodeling of intermediate filaments inserts (or dissociates) unit lengths of filaments into (from) the middle of existing filaments. Process controlled by phosphorylation status and doesn't require ATP or GTP.
• Bridging protein: Plectin (epithelial cell)

  • Bridging intermediate filaments using plectin helps stabilize other cytoskeletal elements, increasing cell stability
• What is the function of intermediate filaments in neurons?

  Neurofilaments:

  • Made up of 3 distinct proteins
  • Have sidearms that help maintain proper spacing
  • Important for determining the axon's diameter
• The cross-bridges that hold intermediate filaments together (or connect them with microtubules or microfilaments) are composed of?

  plectin