What is the cortical cytoskeleton?

The cortical cytoskeleton is a specialized and dynamic part of the cell's cytoskeleton located just beneath the plasma membrane. It is primarily composed of actin filaments (microfilaments) along with associated proteins like spectrin, ankyrin, filamin and ERM (ezrin, radixin, moesin) proteins. This region forms a dense network of filamentous proteins that help maintain the cell's shape, provide mechanical support and regulate interactions with the external environment. The cortical cytoskeleton plays a key role in cellular processes like endocytosis, cell motility, signal transduction and adhesion, especially in animal cells.

Structure of the Cortical Cytoskeleton

The main structural element of the cortical cytoskeleton is F-actin, which forms a thin, mesh-like layer closely attached to the inner surface of the plasma membrane. This layer is cross-linked by actin-binding proteins such as filamin and is anchored to membrane proteins via adaptor proteins like spectrin and ankyrin. The actin network is not static; it is continuously undergoing polymerization and depolymerization, which allows the cell to adapt its shape and mechanical properties in response to internal and external signals. The thickness of this actin-rich layer varies with the type and condition of the cell but typically remains between 100–500 nm.

Functions of Cortical Cytoskeleton

There are five main functions of the cortical cytoskeleton:

1. Maintenance of Cell Shape:
  • It provides mechanical strength to the cell membrane and helps the cell resist deformation, especially during external pressure or stress.
2. Cell Motility and Migration:
  • By controlling actin polymerization at the cell edges, it enables amoeboid or crawling-type movement in cells like leukocytes, fibroblasts, and epithelial cells.
3. Endocytosis and Exocytosis:
  • It facilitates vesicle formation and membrane trafficking by coordinating with clathrin and dynamin complexes during endocytosis and vesicle docking during exocytosis.
4. Cell Adhesion and Cortical Tension:
  • It stabilizes cell junctions and generates cortical tension required for tissue integrity and cell positioning within tissues.
5. Signal Transduction:
  • It acts as a platform for membrane-bound signaling complexes and transduces signals from the external environment to the internal cytosol.






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