cytoskeleton

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Related to Cytoskeletal: actin, Cytoskeletal protein

Cytoskeleton

A system of filaments found in the cytoplasm of cells and responsible for the maintenance of and changes in cell shape, cell locomotion, movement of various elements in the cytoplasm, integration of the major cytoplasmic organelles, cell division, chromosome organization and movement, and the adhesion of a cell to a surface or to other cells.

Three major classes of filaments have been resolved on the basis of their diameter and cytoplasmic distribution: actin filaments (or microfilaments) each with an average diameter of 6 nanometers, microtubules with an average diameter of 25 nm, and intermediate filaments whose diameter of 10 nm is intermediate to that of the other two classes. The presence of this system of filaments in all cells, as well as their diversity in structure and cytoplasmic distribution, has been recognized only in the modern period of biology.

A technique that has greatly facilitated the visualization of these filaments, as well as the analysis of their chemical composition, is immunofluorescence applied to cells grown in tissue culture. See Immunofluorescence

Actin is the main structural component of actin filaments in all cell types, both muscle and nonmuscle. Actin filaments assume a variety of configurations depending on the type of cell and the state it is in. They extend a considerable distance through the cytoplasm in the form of bundles, also known as stress fibers since they are important in determining the elongated shape of the cell and in enabling the cell to adhere to the substrate and spread out on it. Actin filaments can exist in forms other than straight bundles. In rounded cells that do not adhere strongly to the substrate (such as dividing cells and cancer cells), the filaments form an amorphous meshwork that is quite distinct from the highly organized bundles. The two filamentous states, actin filament bundles and actin filament meshworks, are interconvertible polymeric states of the same molecule. Bundles give the cell its tensile strength, adhesive capability, and structural support, while meshworks provide elastic support and force for cell locomotion.

Microtubules are slender cylindrical structures that exhibit a cytoplasmic distribution distinct from actin filaments. Microtubules originate in structures that are closely associated with the outside surface of the nucleus known as centrioles. The major structural protein of these filaments is known as tubulin. Unlike the other two classes of filaments, microtubules are highly unstable structures and appear to be in a constant state of polymerization-depolymerization. See Centriole

Intermediate filaments function as the true cytoskeleton. Unlike microtubules and actin filaments, intermediate filaments are very stable structures. They have a cytoplasmic distribution independent of actin filaments and microtubules. In the intact cell, they anchor the nucleus, positioning it within the cytoplasmic space. During mitosis, they form a filamentous cage around the mitotic spindle which holds the spindle in a fixed place during chromosome movement.

cytoskeleton

[¦sīd·ō′skel·ə·tən]
(cell and molecular biology)
Protein fibers composing the structural framework of a cell.
References in periodicals archive ?
The effect of ageing on the water-holding capacity of pork: Role of cytoskeletal proteins.
This implies a previously unrecognized role for the prokaryotic cytoskeleton in which the cytoskeletal system participates in equipartition of the terminus regions of replicated chromosomes into daughter cells.
As the final design of the web portal was being developed, Bill and his students were starting to study the cytoskeletal events underlying the eccentric meiosis in the egg of the surf clam Spisula solidissima.
Recent progress in the study of cancer cell motility and invasion has generated greater understanding of the mechanical properties involved in malignant transformation and cell mechanics, which have emerged as important markers for cytoskeletal organization, cell adhesion, and spreading.
ROCK is an enzyme that phosphorylates cytoskeletal regulatory proteins and plays a role in cytoskeletal regulation.
However, each protein influenced the function of a different cytoskeletal part.
Rho-Rho-kinase pathway in smooth muscle contraction and cytoskeletal reorganization of non-muscle cells.
The cytoskeletal network along the edge of the infected cells was enhanced and could be involved in transporting and expelling the progeny virus particles.
Up to now, it has not been appreciated that cytoskeletal organization is an important element in the regulation of NK cell activity," Wuelfing emphasizes.
The water-swellable polyelectrolyte acts as a support for the biomembrane, not unlike the cytoskeletal support found in mammalian cell membranes.
To confirm the likely diagnosis of leiomyosarcoma, immunohistochemistry was performed for cytoskeletal proteins such as actin, myosin, and desmin; these proteins have been widely used in the differential diagnosis of sarcomas.