Desmosomes cells linked

Desmoplakin is the most abundant desmosomal component that plays a critical role in linking intermediate filament networks to the desmosomal plaque. Desmoplakin forms rod-like dimers that bind to intermediate filaments and to the cadherin-associated proteins plakoglobin and plakophilin. Gene knock-out experiments have revealed an essential role of desmoplakin in establishing cell-cell contacts in early mouse embryos. 

The columnar, cuboidal basal cells are 18-20 xm in height and 8-10 iim in diameter. They form a monolayer adhered to a basement membrane by hemidesmosomes which are linked to anchoring fibrils of collagen type VII. At the lateral borders, basal cells are extensively interdigitated and joined together in places only by junctional complexes (zonula adherens), desmosomes, and gap junctions. 

Cadherins are calcium-dependent and establish molecular links between adjacent cells. They include neural cadherins (NC), epithelial cadherins (EC), placental cadherins (PC), protocadherins and desmosomal cadherins. Cadherins mediate homophilic interactions and form zipper-like structures at adherens junctions and... 

Intermediate filament associated proteins (IFAPs) coordinate interactions between intermediate filaments (IFs) and other cytoskeletal elements and organelles, including membrane-associated junctions such as desmosomes and hemidesmosomes in epithelial cells, costameres in striated muscle, and intercalated discs in cardiac muscle. IFAPs thus serve as critical connecting links in the IF scaffolding that organizes the cytoplasm and confers mechanical stability to cells and tissues. However, in recent years it has become apparent that IFAPs are not limited to structural... 

Plakin proteins link intracellular keratin intermediate filaments to hemidesmosomes of basal epidermal cells, or to desmosomes on suprabasal epidermal cells (Sect. 5.2.1), whereas type XVII collagen (the only collagen secreted by epithelial cells ) and integrins attach hemidesmosomes to a basal lamina. Three p 1 integrins (with al, a3 or a5 partners)... 

A FIGURE 5-32 Fluorescence micrograph of a PtK2 fibroblast cell stained to reveal keratin intermediate filaments. A network of filaments crisscrosses the cell from the nucleus to the plasma membrane. At the plasma membrane, the filaments are linked by adapter proteins to two types of anchoring junctions desmosomes between adjacent cells and hemidesmosomes between the cell and the matrix. [Courtesy of R. D. Goldman.]... 

The epidermis Is a tough outer layer of tissue, which acts as a water-tight barrier to prevent desiccation and serves as a protection against abrasion. In epidermal cells, bundles of keratin filaments are cross-linked by filaggrin, an IFAP, and are anchored at their ends to desmosomes. As epidermal cells differentiate, the cells condense and die, but the keratin filaments remain intact, forming the structural core of the dead, keratinized layer of skin. The structural Integrity of keratin Is essential in order for this layer to withstand abrasion. 

Anchoring junctions may link cellular cytoskeleton proteins through the plasma membrane to the extracellular matrix or an adjacent cell. Such an anchoring junction involves a transmembrane protein that binds the cytoskeleton on the cytoplasmic face of the plasma membrane. On the extracellular face of the plasma membrane, the anchoring junction binds either the extracellular matrix (focal contacts, adhesion plaques, or hemidesmosomes) or a receptor on another cell (adhesion belt or desmosomes). 

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