The main difference between adherence junctions and desmosomes is that the extracellular region of adherens junctions lacks a highly organized structure, whereas the extracellular region of desmosomes exhibits a highly organized structure.
Intercellular junctions are specialized regions of contact between the plasma membranes of adjacent cells. They provide structural means of connecting a group of cells. In fact, these junctions play a critical role in maintaining tissue integrity, regulating cell signalling, and controlling the movement of molecules and cells across tissue boundaries. These are mostly present in the epithelial cells and attach strongly to the extracellular matrix and one another. Adherens junctions and desmosomes are two important intercellular adhesive structures present in the body.
Key Areas Covered
1. What are Adherens Junctions
– Definition, Structure, Function
2. What are Desmosomes
– Definition, Structure, Function
3. Similarities Between Adherens Junctions and Desmosomes
– Outline of Common Features
4. Difference Between Adherens Junctions and Desmosomes
– Comparison of Common Features
Adherens Junctions, Belt Desmosomes, Desmosomes, Intermediate Junctions, Macula Adherens, Zonula Adherens
What are Adherens Junctions
Adherens junctions are cell-to-cell adhesion complexes that continuously assemble and dissemble. Adherens junctions are also called zonula adherens, intermediate junctions, or belt desmosomes. These junctions allow the cells to respond to biochemical signals, forces, and structural changes within a tissue. They are most commonly present in epithelial cells, endothelial cells, and cardiac muscle tissue. In epithelial tissues, adherens junctions are located below the tight junctions that seal the spaces between cells. However, in endothelial tissues, adherens junctions are present between adjacent endothelial cells, which help maintain the structural integrity of blood vessels. Adherens junctions are also present in the intercalated discs, allowing them to contract in a coordinated manner in the cardiac muscle tissue.
Moreover, adherens junctions are formed by a complex of proteins, including catenins, actin filaments, and cadherins. Cadherins, which are transmembrane proteins, create a homophilic interaction that holds cells together. Catenin proteins bind to the cytoplasmic tail of cadherins and link them to the actin cytoskeleton, providing stability to the junction. Actin filaments maintain the structure and shape of the cells and regulate the movement of cells during development and wound healing.
Disruption in adherens junctions paves the way for a variety of illnesses, including cancer, developmental disorders, and cardiovascular diseases.
What are Desmosomes
Desmosomes are specialized and highly ordered membrane domains. They are involved in the mediation of cell-to-cell contact and strong adhesion. They mechanically integrate cells within the tissues functioning to resist mechanical stress. Another name for desmosomes is macula adherens. Desmosomes are one of the strongest types of adhesion; hence, they are present in tissues that bear intense mechanical stress, such as cardiac muscle tissue, epithelia, gastrointestinal mucosa, and bladder tissue.
The structure of desmosomes includes desmosome intermediate filament complexes (DIFC). This is a network of cadherin proteins, linker proteins, and intermediate filaments. Moreover, three regions of DIFC can be identified as the outer dense plaque, the inner dense plaque, and the extracellular core region. Additionally, in desmosomes, there are two plaque proteins: plakoglobins and plakophilins. These proteins anchor desmosomal cadherins to the cytoskeleton of the cell, providing additional strength and stability to the junction.
When the adhesion of desmosomes does not occur properly, tissues that undergo mechanical stresses do not function properly. Moreover, the desmosome intermediate filament complex maintains the integrity of such tissues.
Desmosomes also play a role in the cell signallling pathways. For example, plakoglobin regulates the activity of the Wnt signalling pathway, which helps in cell proliferation and differentiation.
Furthermore, a mutation in genes encoding desmosomal proteins can lead to a variety of diseases. For example, mutations in the desmoglein-1 gene are associated with the pemphigus foliaceus skin disorder, while mutations in the desmoplakin gene are associated with arrhythmogenic right ventricular cardiomyopathy.
Similarities Between Adherens Junctions and Desmosomes
- Adherens junctions and desmosomes are intercellular junctions.
- Moreover, they facilitate adhesion and cohesion.
- In addition, both consist of cell adhesion molecules.
Difference Between Adherens Junctions and Desmosomes
Adherens junctions are cell-to-cell adhesion complexes that are continuously assembled and disassembled, while desmosomes are specialized and highly ordered membrane domains that mediate cell-to-cell contact and strong adhesion.
Adherens junctions do not have highly ordered structures in their extracellular region, whereas desmosomes have highly ordered structures in their extracellular region.
Regulation of Cellular Processes
Moreover, adherens junctions regulate different cellular processes, such as cell shape, division, growth, apoptosis, and barrier function, whereas desmosomes do not take part in many cellular functions other than cell cohesion.
While adherens junctions are calcium-dependent, desmosomes are calcium-independent.
Cell Adhesion Molecules
Adherens junctions consist of type -1 cadherins, whereas desmosomes consist of desmosomal cadherins.
In brief, intercellular junctions are regions of contact between the plasma membranes of adjacent cells. They provide structural means of connecting a group of cells. Adherens junctions and desmosomes are two main intercellular adhesive structures in the body. The main difference between adherence junctions and desmosomes is that the extracellular region of adherens junctions lacks a highly organized structure, whereas the extracellular region of desmosomes exhibits a highly organized structure.
1. Hartsock, Andrea, and W James Nelson. “Adherens and Tight Junctions: Structure, Function and Connections to the Actin Cytoskeleton.” National Library of Medicine.
2. Kowalczyk, Andrew P, and Kathleen J Green. “Structure, Function and Regulation of Desmosomes.” National Library of Medicine.