Desmosome
Desmosomes ( ancient Greek δεσμός desmós , German 'connection' and ancient Greek σῶμα sṓma , German 'body' ), also macula adhaerens , are cell structures in cell membranes that create close disc-shaped connections between two cells. They occur particularly in cells with intensive mechanical stress, such as epithelial cells and some non-epithelial tissues, such as the heart muscles, and improve mechanical cohesion (protection against shear forces ). This happens mainly because they connect the cell's own intermediate filaments with those of other cells. In epithelial cells, these are mostly the keratin filaments and in heart muscle cells, desmin filaments.
Desmosomes appear like spherical densities on the side walls of epithelial cells - comparable to snaps or rivets. The intercellular space is sometimes slightly widened at these points, as it is filled with filamentous material ( glycoproteins and mucopolysaccharides ), similar to a cement substance.
On the inside of the cell membrane there are plate-shaped structures made of Desmoplakin at these points. Numerous non-contractile fibril bundles made of keratin, the so-called tonofilaments, are anchored in these cells, tapering from the entire cell interior. As these continue to run through the entire cell, they link the desmosome with the cytoskeleton and thus stabilize its location on the cell surface.
Homotypically binding cadherins ( desmoglein and desmocollin ), which are also anchored in the cytoplasmic plate , protrude through the junction (plaque) . They combine with cadherins from other cells in the intercellular space and thus establish a connection.
Autoantibodies against desmoglein lead to the clinical picture of pemphigus vulgaris .
Hemidesmosomes are desmosome-like compounds, which, however, do not connect two identical cell membranes of similar cells, but rather the cell membrane of a cell with a basal lamina , for example in epithelia.
See also
The cell contact article provides an overview of the different types of cell contact. Among these there are adhesive connections, the desmosomes, adherens junctions and focal adhesions described here , closing connections such as the tight junctions (Zonulae occludentes), which can create very tight, more impermeable connections between cell membranes than the desmosomes, as well as the communicating connections , the gap junctions (nexus), which connect pore-like compartments separated by two cell membranes and allow mass transfer.
Web links
- Université de Friborg, Département de Médecine: Intercellular connections (with drawings)
literature
- Alberts, B. et al .: Molecular Biology of the Cell . Garland Science, 4th Edition, 2002. ISBN 0-8153-4072-9 .