Intermediate filaments
| Parent |
| Cytoskeleton |
| Gene Ontology |
|---|
| QuickGO |
Intermediate filaments ( Filamenta intermedialia ) are structures made of proteins in the cytoplasm of a cell , which serve to increase the mechanical stability of the cell. In addition to microtubules and microfilaments, they are among the main structural components of the cytoskeleton . The name comes from the fact that they are around 10 nanometers in diameter between the microfilaments (7 nm) and the microtubules (20 to 30 nm). There are no intermediate filaments in plants .
construction
A single monomer , the subunit of the intermediate filaments, is about 48 nm long and very thin. The monomer has globular domains at both ends that are type-specific, i.e. they can differ from protein to protein. A coiled coil dimer consists of two parallel monomers wound around themselves like ropes. Several of these dimers are antiparallel and slightly shifted by non-covalent bonds to one another to form tetramers. Many of these tetramers in turn form a rope-like filament with a tetramer in the center and seven tetramers wound around it with a total diameter of approx. 10 nm.
The intermediate filaments are connected to one another to form larger bundles ( tonofibrils ) by specific proteins ( intermediate filament-associated proteins , e.g. desmoplakin ) . These proteins also serve to connect the intermediate filaments to the other elements of the cytoskeleton.
Types
There are currently six types of intermediate filaments, some of which are still unclassified, so that up to nine types are conceivable. Some are tissue-specific, lamines are found in all cells.
| Type | Representative | Occurrence |
| 1 (acidic keratin) | acidic keratin | Epithelia |
| 2 (basic keratins) | basic keratin | Epithelia |
| 3 ( Desmine ) |
GFAP (glial fibrillar acidic protein) Desmin Vimentin peripherin |
Glial cells , astrocytes, muscle cells, cells of mesenchymal origin, peripheral neurons |
| 4th | α-internexin | CNS during development |
| 5 ( lamines ) | Lamin A Lamin B Lamin C |
Nucleus nucleus nucleus |
| 6 ( neurofilaments ) | NF-L β-internexin NF-M NF-H nestin |
Neurons neurons neurons neurons neuroepithelial stem cells |