DESMOSOME STRUCTURE & ITS FUNCTIONS|
Bricks in a building must be stuck together and also tied somehow to the foundation. Similarly, cells within tissues and organs must be anchored to one another and attached to components of the extracellular matrix. Cells have developed several types of junctional complexes to serve these functions, and in each case, anchoring proteins extend through the plasma membrane to link cytoskeletal proteins in one cell to cytoskeletal proteins in neighboring cells as well as to proteins in the extracellular matrix. ANCHORING JUNCTIONS
Three types of anchoring junctions are observed, and differ from one another in the cytoskeletal protein anchor as well as the transmembrane linker protein that extends through the membrane:
| JUNCTION| CYTOSKELETAL
LINKER| TIES CELL TO|
1| DESMOSOMES| INTERMEDIATE FILAMENTS| CADHERIN| OTHER CELLS| 2| HEMIDESMOSOMES| INTERMEDIATE FILAMENTS| INTEGRINS| EC MATRIX| 3| ADHERENS JUNCTIONS| ACTIN FILAMENTS| CADHERIN
INTEGRINS| OTHER CELLS
The desmosome was first observed in the spinous layer of epidermis by the Italian pathologist Giulio Bizzozero (1846–1901). Bizzozero's observations of these small dense nodules, subsequently named “nodes of Bizzozero,” led him to the insightful interpretation of these structures as adhesive cell–cell contact points. The term desmosome was later coined by Josef Schaffer in 1920 and is derived from the Greek words “desmo,” meaning bond or fastening, and “soma,” meaning body . The introduction of electron microscopy yielded a series of advances by Porter, Odland, and Kelly in the 1950s and 1960s, which revealed desmosome organization at the ultrastructural level.
A desmosome also known as macula adherens, is a cell structure specialized for cell-to-cell adhesion. Cell–cell adhesions are crucial for the function of multicellular organisms by providing mechanical stability and facilitating signal transmission between neighboring cells. Desmosomes are prominent adhesion sites that are tightly associated with the cytoplasmic intermediate filament cytoskeleton providing mechanical stability in epithelia and also in several nonepithelial tissues such as cardiac muscle and meninges.
Desmosomes help to resist shearing forces and are found in simple and stratified squamous epithelium. The intercellular space is very wide (about 30 nm). The desmosome is an adhesive intercellular junction that is crucial to tissues that experience mechanical stress, such as * THE MYOCARDIUM
* GASTROINTESTINAL MUCOSA
DEVELOPMENT OF DESMOSOME:
* Desmosome formed during development. Desmosomes are first detected together with keratin filaments in the trophectoderm during the blastocyst stage of preimplantation mouse embryos (Collins and Fleming, 1995; Collins et al., 1995; Ducibella et al., 1975; Eshkind et al., 2002; Fleming et al., 1991; Jackson et al., 1980).
* Desmosome formation strengthens adhesion to maintain tissue integrity in the presence of increasing mechanical stress imposed by the accumulating blastocoele fluid. (Fleming et al., 1991).
Desmogleins and desmocollins, members of the cadherin superfamily, mediate adhesion at desmosomes. THE ARMADILLO GROUP PROTEINS
These desmosomal plaque components include plakoglobin and the plakophilins, members of the armadillo gene family. Plakoglobin, a member of the armadillo family, binds directly to the cytoplasmic tails of both the desmogleins and...