Introduction[edit | edit source]
Within all eukaryotic cells there exists a network of filaments, which is a complex mesh of protein filaments and motor proteins that aid in cell movement and stabilize the cell . They help cells maintain their shape and internal structure and mechanical support, enabling cells to carry out basic functions like division and movement. By means of this cytoskeletal network, the cell integrates numerous signals in order to coordinate its behavior, communicate with other cells, and adjust to its environment.
Genetic defects in cytoskeletal proteins are associated with mechanical defects in cells and tissues, leading to eg Focal Segmental Glomerulosclerosis, Epidermolysis Bullosa, Muscular Dystrophy, Intermediate filament gene mutations cause Charcot–Marie–Tooth disease and motor neurone disease.
Filament Types[edit | edit source]
There are three types of filaments make up the cytoskeleton:
- Actin filaments occur in a cell in the form of meshwork or bundles of parallel fibres. They help in controlling the shape of the cell and also adhere the cell to the substrate. These filaments are constantly rearranging, helping move the cell and bring about specific activities within it e.g. cell cleavage during mitosis. Size, 6 nm in diameter and are composed of a protein called actin.
- Microtubules (MT) are longer filaments that are constantly assembling and disassembling. MTs play a crucial role in e.g. moving the daughter chromosomes to the newly forming daughter cells during mitosis. Bundles of MTs form the cilia and flagella found in protozoans and in the cells of some multicellular animals. Largest filaments, 24 nm in diameter, composed of a protein called tubulin.
- Intermediate filaments, in contrast to actin filaments and microtubules, are very stable structures that form the true skeleton of the cell. They anchor the nucleus and position it within the cell, and they give the cell its elastic properties and its ability to withstand tension. Size, 10 nm in diameter, built from a number of different subunit proteins.
Filaments in Neurons[edit | edit source]
All the types of cytoskeleton filaments work together to guarantee correct formation of the nervous system during the embryonic development and to assure its function in adulthood. Both cytoskeletal filaments and motor proteins are required for axonal transport. Important neuronal events where the function of cytoskeletal filaments are required are
- During embryonic development: the cytoskeleton participating in the growth and guidance of axons
- Adult life: the cytoskeleton essential for maintaining neuronal homeostasis and neuronal plasticity
- Injury repair: peripheral axon needs to regenerate after being injured, peripheral neurons requiring a specific set of cytoskeletal proteins to ensure nerve regeneration upon damage.
Given the importance of cytoskeleton for neurons, it is easy to see how neurological disorders involve changes either in the expression, dynamics, and and/or the stability of cytoskeletal proteins or their mutations. e.g. tauopathies, all share the common denominator of the altered structure or function of the microtubule-associated protein tau .
Striated Muscle Filaments[edit | edit source]
The cytoskeleton fibres in striated muscle have diverse roles as mentioned above, including as functioning as a structure for inter- and intracellular signaling. It does this by linking the complex functioning units of thee sarcomeres, enabling them to function effectively, and in turn provide a connection for these structures in turn to the sarcolemma, cell–cell junctions, the mitochondria, and nucleus. When not functioning correctly pathologies occur as in e.g. myopathies.
References[edit | edit source]
- Anne-Betty Ndiaye eg al.Intermediate Filaments in Cellular Mechanoresponsiveness: Mediating Cytoskeletal Crosstalk From Membrane to Nucleus and Back Available:https://www.frontiersin.org/articles/10.3389/fcell.2022.882037/full (accessed 7.7.2022)
- Frans CS Ramaekers, Fred T Bosman The cytoskeleton and disease. Available: https://onlinelibrary.wiley.com/doi/full/10.1002/path.1665 (accessed 7.7.2022)
- Britannica Cytoskeleton Available:https://www.britannica.com/science/cytoskeleton (accessed 7.7.2022)
- Scitable Microtubules and filaments Available:https://www.nature.com/scitable/topicpage/microtubules-and-filaments-14052932/ (accessed 7.7.2022)
- Diana C. Muñoz-Lasso, Carlos Romá-Mateo, [...], and Pilar Gonzalez-Cabo Much More Than a Scaffold: Cytoskeletal Proteins in Neurological Disorders Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7072452/(accessed 7.7.2022)
- J Robbins Chapter 9 - Diseases of the Cytoskeleton: The Desminopathies Available: https://www.sciencedirect.com/science/article/pii/B9780128000403000091(accessed 7.7.2022)