Desmosomes are a specific type of cell junction that form strong adhesive connections between neighboring cells. They link cells together, providing tissues with the mechanical strength to withstand physical stresses. Imagine them as cellular spot-welds or rivets, anchoring cells to one another. This connection helps maintain the integrity and cohesion of tissues throughout the body.
How Desmosomes Are Built and What They Do
Desmosomes are intricate structures built from several protein components that create a robust cellular bond. At their core are cadherin proteins, specifically desmogleins and desmocollins, which extend from the cell membrane into the extracellular space to link with cadherins from an adjacent cell. These cadherins initiate cell-to-cell adhesion, forming a strong connection between the two membranes.
Inside the cell, these cadherins connect to a dense cytoplasmic plaque, a complex assembly of linker proteins. This plaque includes proteins such as plakoglobin, plakophilins, and desmoplakin. Desmoplakin acts as a bridge, anchoring the cadherin-linker protein complex to the cell’s internal scaffolding system. This internal scaffolding is composed of intermediate filaments, strong, rope-like protein fibers that extend throughout the cell’s cytoplasm.
The primary function of this structure is to provide mechanical strength and resist pulling forces within tissues. By connecting the intermediate filament networks of adjacent cells, desmosomes ensure that mechanical stress applied to one cell is distributed across many cells. This distribution prevents individual cells from tearing apart under tension, maintaining the structural integrity of tissues that frequently experience stretching, friction, or other mechanical stresses.
Where Desmosomes Are Found and Their Role
Desmosomes are abundant in tissues that experience mechanical stress, where their adhesive strength is important for tissue function. The skin, specifically the epidermis, contains a high concentration of desmosomes. Here, they help the skin endure friction and stretching, preventing cells from detaching and maintaining its barrier function against the external environment.
Heart muscle, known as the myocardium, also relies on desmosomes. These junctions are found at specialized structures called intercalated discs, unique to cardiac muscle cells. Desmosomes ensure heart muscle cells remain firmly connected during the continuous contractions required to pump blood. This connection is vital for the coordinated mechanical action and overall stability of the heart tissue.
Other epithelial tissues, such as those lining the bladder and gastrointestinal tract, also feature desmosomes. In these locations, desmosomes contribute to the mechanical resilience needed to withstand forces associated with organ function, such as bladder expansion and contraction or food movement through the digestive system. Their presence ensures these tissues maintain structural integrity despite recurring physical demands.
When Desmosomes Malfunction
When desmosomes do not function correctly, it can lead to weakened tissue structure and various diseases. One group of conditions involves autoimmune blistering diseases, such as Pemphigus. In Pemphigus, the body’s immune system mistakenly produces antibodies that attack desmogleins, cadherin proteins forming part of the desmosome. This attack disrupts cell-to-cell adhesion, causing skin and mucous membrane cells to detach and form painful blisters.
Another condition linked to desmosome dysfunction is Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC). This genetic disorder primarily affects the heart muscle and is often caused by mutations in genes coding for desmosomal proteins, such as desmoglein 2 or desmocollin 2. Faulty desmosomes lead to a breakdown in connections between heart muscle cells, causing progressive loss of heart muscle tissue and its replacement by fatty and fibrous tissue. This structural compromise can result in heart rhythm abnormalities and an increased risk of sudden cardiac arrest.
In both scenarios, whether due to autoimmune attack or genetic mutation, the underlying issue is the failure of desmosomes to maintain strong intercellular bonds. The resulting cell detachment or weakened tissue integrity directly manifests as the symptoms observed in these conditions, highlighting the role desmosomes play in tissue health.