Desmosome Diseases

  Adherens Junctions, also known as desmosomes, are complex disc shaped structures at the surface on one epithelial cell which is matched with an identical structure on the surface of an adjacent cell. In close approximation to the junction is a circular plaque made of some 12 proteins called the attachment plaque about 300 nanometers in length, with the interior portion of the plaque having a sort of fuzzy appearance. The desmosome is made up of several specialized proteins including: Desmocollins, which are large proteins (MW 130,000) that are responsible for the actual adhesion of the cells -- desmocollins from one cell reach out and attach to desmocollins in the adjacent cell. Others are the desmogleins (MW 165,000) & plakoglobins (MW 83,000) which extend into the cytoplasm. Another set of proteins, desmoplakins, are entirely cytoplasmic and connect the desmosome with intermediate filament proteins. The plaques have numerous intermediate filaments (keratin) entering and leaving them. Desmosomes function as points of especially firm adhesion between adjacent cells. This is the only type of junction seen in the stratified squamous epithelium of the skin. Hemidesmosomes, or half desmosomes, can be found in the interaction of a cell membrane with the basement membrane where they serve to bind the cell to the membrane.
Desmosomes form a tight, impenetrable barrier anchoring cells to each other or to a substrate. A disease known as pemphigus, which is a rather painful condition characterized by the formation of large blisters on the skin, is caused by a breakdown of desmosomal structures. Carcinomas are cancers of epithelia. However, the cells of carcinomas no longer have desmosomes. This may account for their ability to metastasize. .