Cytoskeleton and Cell Motility
The cytoskeleton is a dynamic network of protein filaments that gives cells their shape, organizes their interior, and powers movement and intracellular transport.
Definition
The cytoskeleton is the system of filamentous protein polymers and associated proteins that structures the cytoplasm and enables cell movement and intracellular transport.
Scope
This area covers the three main cytoskeletal systems, actin filaments, microtubules, and intermediate filaments, their assembly dynamics, the molecular motors that move along them, and how these components drive cell shape, crawling, division, and the transport of cargo.
Sub-topics
Core questions
- What are the three main types of cytoskeletal filaments and their roles?
- How do actin filaments and microtubules assemble and disassemble dynamically?
- How do molecular motors generate force and movement?
- How does the cytoskeleton drive cell crawling and intracellular transport?
Key theories
- Dynamic instability of microtubules
- Microtubules switch between phases of growth and rapid shrinkage, a stochastic dynamic that lets them rapidly reorganize and explore cellular space.
- Actin treadmilling and assembly-driven motility
- Directed assembly and disassembly of actin filaments, with addition at one end and loss at the other, generates the pushing forces that drive cell-edge protrusion and crawling.
Mechanisms
Actin filaments form a dynamic network, especially at the cell cortex, that drives shape changes and protrusion through polymerization and motor activity. Microtubules grow and shrink by dynamic instability and serve as tracks for long-range transport and as the spindle in division. Intermediate filaments provide mechanical strength. Molecular motors, myosins on actin and kinesins and dyneins on microtubules, hydrolyze ATP to move directionally, carrying organelles and vesicles and producing contraction and motility.
Clinical relevance
The cytoskeleton underlies cell architecture, division, migration, and transport, making it a foundational system in cell biology. The treatment here is descriptive and non-prescriptive.
History
Discovery of microtubule dynamic instability and detailed studies of actin assembly established how the cytoskeleton reorganizes; the identification of motor proteins such as kinesin by Vale and colleagues revealed how movement along filaments is powered.
Key figures
- Tim Mitchison
- Marc Kirschner
- Thomas Pollard
- Ronald Vale
Related topics
Seminal works
- mitchison1984
- pollard2003
Frequently asked questions
- What are the main parts of the cytoskeleton?
- The three main filament systems are actin filaments, which drive shape and movement, microtubules, which organize transport and division, and intermediate filaments, which provide mechanical strength.
- How do cells move?
- Many cells crawl by assembling actin filaments to push out the leading edge, forming adhesions, and using motor proteins to pull the cell body forward.