U01.01.027 Cytoskeletal elements

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Learning Objectives

  • Differentiate between the three main types of cytoskeletal filaments.
  • Identify the unique functions of Microfilaments, Intermediate Filaments, and Microtubules.
  • Connect specific Intermediate Filaments to their respective tissue types.
  • Understand the role of the cytoskeleton in cell division and trafficking.

1. Overview of the Cytoskeleton

The cytoskeleton is a dynamic network of protein fibers that provides mechanical support, facilitates movement, and organizes the internal components of the cell.

2. The Three Filament Types

 

Filament Type Predominant Function Examples
Microfilaments Muscle contraction, cytokinesis, phagocytosis. Actin, microvilli.
Intermediate filaments Maintain cell structure and tensile strength. Vimentin, Desmin, Cytokeratin, Lamins, GFAP, Neurofilaments.
Microtubules Movement, cell division, and intracellular transport. Cilia, flagella, mitotic spindle, centrioles.

3. Intermediate Filaments: Tissue Specificity

Intermediate filaments are highly specific to tissue types, making them excellent immunohistochemical markers in pathology to identify the origin of tumors.

  • Vimentin: Connective tissue (Mesenchymal cells).
  • Desmin: Muscle (Skeletal, smooth, and cardiac).
  • Cytokeratin: Epithelial cells.
  • GFAP: Glial cells (Astrocytes, Schwann cells).
  • Neurofilaments: Neurons.
  • Nuclear Lamins: Inner nuclear membrane (Structure of the nucleus).

4. Microtubules: The Highway System

Microtubules are large, hollow tubes composed of \alpha– and \beta-tubulin dimers. They are essential for structural integrity and movement.

  • Axonal Trafficking: Serves as tracks for motor proteins.
    • Kinesin: Anterograde transport (towards the (+) end/periphery).
    • Dynein: Retrograde transport (towards the (-) end/nucleus).
  • Cell Division: Form the mitotic spindle, which pulls sister chromatids apart.

 

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