Cytoskeletons

The cytoskeleton is a dynamic network of protein filaments that pervades the cytoplasm of eukaryotic cells. It is composed mainly of actin filaments (microfilaments), microtubules, and intermediate filaments, with accessory proteins shaping their organization and activity.

Actin filaments support cell shape and enable changes in shape, movement, and muscle contraction. Microtubules resist compression, organize organelles, and form tracks for motor proteins. Intermediate filaments provide mechanical strength and resilience to stress, helping cells withstand deformation and maintain integrity.

The cytoskeleton is highly dynamic. Filaments polymerize and depolymerize rapidly in response to signals. Microtubules exhibit dynamic instability; actin filaments can undergo treadmilling. Nucleation and organization are controlled by specific factors and motor proteins such as kinesins, dyneins, and myosins, which convert chemical energy into mechanical work.

In many cells, microtubules emanate from microtubule-organizing centers and help assemble the spindle during cell division. Actin-based networks drive cell migration and cytokinesis, while intermediate filaments connect to cell junctions to stabilize tissue architecture. The cytoskeleton thus coordinates intracellular organization with cell movement and division.

The cytoskeleton interacts with membranes and organelles through linker proteins, and its function is essential for development, signaling, and homeostasis. Disruptions of its dynamics underlie various diseases, and drugs that alter cytoskeletal components are used in research and medicine.