Desmosomes

They are found in animal tissues, for example, cardiac muscle tissue, bladder tissue, gastrointestinal mucosa, and epithelial tissue of the outer skin. They are also found between the squamous epithelial cells in the lining of body parts like the heart, blood vessels, air sacs of the lungs, and esophagus.

It is a complex of proteins bearing a disk-shaped structure from which protein fibers extend into the cytoplasm. Some of these proteins extend across the membrane, while others anchor the junction within the cell.

Desmosomes have a highly organized, electron-dense structure. They are less than one μm in diameter and consist of three parts.

What are Desmosomes Made of

They are composed of desmosome-intermediate filament complexes (DIFC), a network of cadherin proteins, linker proteins, and keratin intermediate filaments.

A DIFC consists of three parts:

1. Extracellular Core Region (Desmoglea) is approximately 34 nm in length containing the cadherin family of cell adhesion proteins – desmoglein and desmocollin.

2. Outer Dense Plaque (ODP) is about 15–20 nm in length containing the intracellular ends of desmocollin and desmoglein, the N-terminus portion of desmoplakin, and the armadillo family proteins plakoglobin and plakophilin.

3. Inner Dense Plaque (IDP) is about 15–20 nm in length containing the C-terminus portion of desmoplakin and their attachment to keratin intermediate filaments. Desmoplakin is most abundant in desmosome, acting as the moderator between the cadherin proteins in the plasma membrane and the keratin filaments

The primary function of desmosomes is to provide strong adhesion between adjacent cells, acting like spot welds holding the tissues together. They mediate direct cell-cell contacts and provide anchorage sites for intermediate filaments essential for maintaining tissue integrity.

Since desmosomes connect intermediate filaments of the cell cytoskeletons of adjacent cells, they provide mechanical strength to tissues. Also, they are found to affect the cadherin protein-based intracellular signaling pathways.

Malfunctioning of desmosomes is often the cause of certain human diseases, such as arrhythmogenic cardiomyopathy and blistering diseases.

Arrhythmogenic cardiomyopathy is usually caused due to mutations in desmoglein 2, but sometimes in desmocollin 2. Blistering disease such as pemphigus vulgaris (PV) is an autoimmune disease where auto-antibodies target desmogleins. PV is caused by circulating autoantibodies (IgG) that target Dsg3 (Desmoglein 3) and sometimes Dsg1.