Everything about Desmosome totally explained
A
desmosome, also known as
macula adherens or
macula adherentes (
Latin:
adhering spot), is a
cell structure specialized for cell-to-cell
adhesion. A type of
junctional complex, they're localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes.
Desmosomes help to resist shearing forces and are found in
simple and
stratified squamous epithelium. The intercellular space is very wide (about 30 nm). Desmosomes are also found in muscle tissue where they bind muscles cells to one another.
Structure
Desmosomes are molecular complexes of cell adhesion proteins and linking proteins that attach the cell surface adhesion proteins to intracellular
keratin cytoskeletal filaments.
The cell adhesion proteins of the desmosome, desmoglein and desmocollin, are members of the
cadherin family of cell adhesion molecules. They are
transmembrane proteins that bridge the space between adjacent
epithelial cells by way of
homophilic binding of their extracellular domains to other desmosomal cadherins on the adjacent cell. Both have five extracellular domains, and have calcium-binding motifs.
The extracellular domain of the desmosome is called the Extracellular Core Domain (ECD) or the Desmoglea, and is bisected by an electron-dense midline where the desmoglein and desmocollin proteins bind to each other. These proteins can bind in a W, S, or λ manner.
On the cytoplasmic side of the plasma membrane, there are two dense structures called the Outer Dense Plaque (ODP) and the Inner Dense Plaque (IDP), spanned by the
Desmoplakin protein. The Outer Dense Plaque is where the cytoplasmic domains of the cadherins attach to
desmoplakin via
plakoglobin and plakophillin. The Inner Dense Plaque is where
desmoplakin attaches to the
intermediate filaments of the cell.
Desmosomes function like rivets.
Blistering diseases
If the desmosomes connecting adjacent epithelial cells of the
skin are not functioning correctly, layers of the skin can pull apart and allow abnormal movements of fluid within the skin, resulting in blisters and other tissue damage. Blistering diseases such as
Pemphigus vulgaris can be due to
genetic defects in desmosomal proteins or due to an
autoimmune response. These patients are often found to have
antibodies that bind to the desmosomal cadherins and disrupt the desmosomes.
Hemidesmosomes
When visualized by electron microscopy,
hemidesmosomes are similar in appearance to desmosomes. Rather than linking two cells, hemidesmosomes attach one cell to the
extracellular matrix. Rather than using
cadherins, hemidesmosomes use
integrin cell adhesion proteins. Hemidesmosomes are asymmetrical and are found in epithelial cells connecting the basal face to other cells.
Further Information
Get more info on 'Desmosome'.
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