Desmosomes are specialized cell structures that act as anchoring junctions, providing robust connections between neighboring cells. They are localized, spot-like adhesions situated along the lateral sides of cell membranes.
The Core Function of Desmosomes
Desmosomes serve as strong, stable adhesion complexes that mechanically integrate adjacent cells, particularly in tissues that undergo significant mechanical stress. They function like “spot welds” or “rivets,” distributing mechanical forces across tissues and resisting pulling forces. This role is achieved by coupling adhesive interactions between cells with the internal cytoskeletal network.
The mechanical strength provided by desmosomes is especially important for maintaining tissue architecture and integrity. Without functional desmosomes, tissues would be susceptible to disruption and failure when subjected to external forces like stretching or shearing.
Inside a Desmosome
Desmosomes achieve their strong adhesion through a complex arrangement of proteins. The extracellular region contains desmosomal cadherins, which are cell adhesion proteins. These include desmoglein and desmocollin, which directly link adjacent cells.
On the inside of the cell, these cadherins connect to a dense cytoplasmic plaque. This plaque is made up of proteins like plakoglobin, plakophilin, and desmoplakin. Plakoglobin acts as a bridge between the cadherin tails and desmoplakin, which then anchors the entire complex to intermediate filaments within the cell.
Desmosomes in Action
Desmosomes are found in tissues that endure considerable mechanical forces. The skin, particularly the epidermis, is rich in desmosomes, which are responsible for its integrity and resistance to physical stress. Similarly, heart muscle (myocardium) relies heavily on desmosomes to maintain structural cohesion during continuous contractions.
Their presence in these tissues allows them to withstand stretching and shearing forces without tearing apart. Desmosomes also appear in other epithelial tissues, bladder tissue, and gastrointestinal mucosa, where they contribute to the mechanical stability and proper function of these organs.
Desmosomes and Health
When desmosomes do not function correctly, it can lead to various health conditions. Defects in desmosomal proteins can result from genetic mutations or autoimmune attacks. For instance, skin blistering disorders like Pemphigus are often caused by the immune system attacking desmoglein proteins, leading to a loss of cell adhesion and subsequent blistering.
Heart conditions such as arrhythmogenic cardiomyopathy (ACM) are also linked to desmosomal dysfunction. Mutations in genes coding for desmosomal proteins like plakophilin-2, desmoglein-2, and desmoplakin can lead to the degeneration of heart muscle tissue and irregular heart rhythms. Desmosome integrity is directly related to tissue health and function.