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Cell adhesion in desmosomes
A desmosome, also known as macula adherens (Latin: adhering spot), is a cell structure specialized for cell-to-cell adhesion. A type of junctional complex, they are 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 30nm). 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 Desmoplatkin 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 desmoplatkin 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.

References

  • Green KJ and Jones JC. (1996). "Desmosomes and hemidesmosomes: structure and function of molecular components". The FASEB Journal 10 (8): 871-81.  Full text online
  • Desmosomes Connect Intermediate Filaments from Cell to Cell in Molecular Biology of the Cell by Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts and Peter Walter (2002) Published by Garland Science. ISBN 0-8153-4072-9

External links

Cell junctions - [ edit]
Adherens junction | Desmosome | Hemidesmosome | Gap junction | Tight junction
Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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Cellular adhesion is the binding of a cell to another cell or to a surface or matrix. Cellular adhesion is regulated by specific adhesion molecules that interact with molecules on the opposing cell or surface.
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A cell junction is a structure within a tissue of a multicellular organism. Cell junctions are especially abundant in epithelial tissues. They consist of protein complexes and provide contact between neighbouring cells, between a cell and the extracellular matrix, or they built up
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squamous epithelium (from Latin squama, "scale") is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous cells.
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squamous epithelium (from Latin squama, "scale") is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous cells.
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Keratins are a family of fibrous structural proteins; tough and insoluble, they form the hard but nonmineralized structures found in reptiles, birds, amphibians and mammals. They are rivaled as biological materials in toughness only by chitin.
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cytoskeleton is a cellular "scaffolding" or "skeleton" contained, as all other organelles, within the cytoplasm. It is contained in all eukaryotic cells and recent research has shown it can be present in prokaryotic cells too.
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Cadherins are a class of type-1 transmembrane proteins. They play important roles in cell adhesion whereby they ensure cells within tissues are bound together. They are dependent on calcium (Ca2+) ions to function, hence their name.
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A transmembrane protein is a protein that spans the entire biological membrane. Transmembrane proteins aggregate and precipitate in water. They require detergents or nonpolar solvents for extraction, although some of them (beta-barrels) can be also extracted using denaturing agents.
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epithelium is a tissue composed of a layer of cells. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies. The outermost layer of our skin is composed of dead stratified squamous, keratinized epithelial cells.
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Homophilic binding is a common name for process that is involved in cell adhesion, also called cell-junction. Homophilic binding is a binding between two identical components of the cell junction.
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Desmoplakin is a protein associated with desmosomes.

External links

  • MeSH Desmoplakins


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Plakoglobin (gamma-catenin, was originally identified as a component of desmosomes where it can bind to the cadherin family member desmoglein I.

Plakoglobin also associates with classical cadherins such as E-cadherin and in that context it was called gamma-catenin.
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Intermediate filaments (IFs) are cytoskeletal structures formed by members of a family of related proteins. Intermediate filaments have a diameter between that of actin (microfilaments) and microtubules.
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Skin layers: epidermis, dermis, and subcutis, showing a hair follicle, sweat gland & sebaceous gland.]] In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs.
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MeSH D010392 Pemphigus is an autoimmune disorder that causes blistering and raw sores on skin and mucous membranes. As with other autoimmune disorders, it is caused when the body's defenses mistake its own tissues as foreign, and attack the cells.
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Genetics is the science of heredity and variation in living organisms.[1][2] Knowledge of the inheritance of characteristics has been implicitly used since prehistoric times for improving crop plants and animals through selective breeding.
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MeSH D001327 Autoimmunity is the failure of an organism to recognize its own constituent parts (down to the sub-molecular levels) as "self", which results in an immune response against its own cells and tissues.
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Antibodies (also known as immunoglobulins) are proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses.
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Hemidesmosomes (HD) are very small stud- or rivet-like structures on the inner basal surface of keratinocytes in the epidermis of skin. They are similar in form to desmosomes.
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extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.
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Cadherins are a class of type-1 transmembrane proteins. They play important roles in cell adhesion whereby they ensure cells within tissues are bound together. They are dependent on calcium (Ca2+) ions to function, hence their name.
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Integrins are cell surface receptors that interact with the extracellular matrix and mediate various intracellular signals. They define cellular shape, mobility, and regulate the cell cycle.
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Loyola University Chicago is a private co-educational religious-affiliated university established in Chicago in 1870 as Saint Ignatius College. It was founded by the Roman Catholic religious order of the Society of Jesus and bears the name of the Jesuit patron, Saint Ignatius of
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Boston University (BU) is a private research university located in Boston, Massachusetts, United States. Although chartered by the Massachusetts Legislature in 1869, Boston University traces its roots to the establishment of the Newbury Biblical Institute in Newbury,
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Boston University (BU) is a private research university located in Boston, Massachusetts, United States. Although chartered by the Massachusetts Legislature in 1869, Boston University traces its roots to the establishment of the Newbury Biblical Institute in Newbury,
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Boston University (BU) is a private research university located in Boston, Massachusetts, United States. Although chartered by the Massachusetts Legislature in 1869, Boston University traces its roots to the establishment of the Newbury Biblical Institute in Newbury,
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A cell junction is a structure within a tissue of a multicellular organism. Cell junctions are especially abundant in epithelial tissues. They consist of protein complexes and provide contact between neighbouring cells, between a cell and the extracellular matrix, or they built up
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Adherens junctions (or zonula adherens) are protein complexes that occur at cell-cell junctions in epithelial tissues, usually more basal than tight junctions.
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