The key difference between adherens junctions and desmosomes is that adherens junctions do not have highly ordered structures in their extracellular region, while desmosomes have a highly ordered structure in their extracellular region.
Intercellular adhesive junctions are different adhesive structures that provide adhesion, cohesion, and cell communication between cells. These junctions are mostly present in epithelial cells. These structures show strong attachment to one another and to the extracellular matrix. Adherens junctions and desmosomes are two significant intercellular adhesive structures present in the body.
CONTENTS
1. Overview and Key Difference
2. What are Adherens Junctions
3. What are Desmosomes
4. Similarities – Adherens Junctions and Desmosomes
5. Adherens Junctions vs Desmosomes in Tabular Form
6. Summary – Adherens Junctions vs Desmosomes
What are Adherens Junctions?
Adherens junctions (AJs) are cell-to-cell adhesion complexes that continuously assemble and dissemble, allowing cells to respond to biochemical signals, forces, and structural changes within a tissue. AJ is a cell junction, and its cytoplasmic face links to actin cytoskeletons. They usually appear as bands around the cell or spots attaching to the extracellular matrix.
AJs are mainly composed of four proteins. They are cadherins, delta catenin, plakoglobin, and alpha-catenin. Cadherins are transmembrane proteins that form homodimers in a calcium-dependent manner. Delta catenin, which is also known as p120, binds juxta membrane regions of the cadherin. Plakoglobin or gamma-catenin binds catenin binding regions in the cadherin. Alpha catenin binds cadherin through beta-catenin or plakoglobin indirectly to link the actin cytoskeleton with cadherin. The formation of AJs goes via initiation, cadherin recruitment, and recruitment of plaque proteins. The functions of AJs are initiation and stabilization of cell-to-cell adhesions, intracellular signaling, regulation of actin cytoskeleton, and transcriptional regulation.
What are Desmosomes?
Desmosomes are cell structures that specialize in cell-to-cell adhesions. They are mechanical junctions primarily involved in cell cohesion. It is a type of cell junction complex that localizes spot-like adhesions on the lateral sides of plasma membranes. Desmosomes are one of the strongest types of adhesion. They are especially found in tissues and experience intense mechanical stresses such as cardiac muscle tissues, gastrointestinal mucosa, epithelia, and bladder tissues.
Figure 2: Desmosomes
Desmosomes are mainly composed of desmosome-intermediate filament complexes (DIFC), including cadherin proteins, linker proteins, and keratin intermediate filaments. DIFCs consist of three regions: extracellular core region or desmoglea, outer dense plaque (ODP), and inner dense plaque (IDP). In desmosomes, two distinguishable plaque proteins are present. They are plakoglobins and plakophilins, which belong to the armadillo repeat protein family, and plakin family, which includes desmoplakin, envoplakin, periplakin, and plectin. During the movement of keratinocytes through the epidermal layers, they form and retrieve desmosomes at the cell periphery.
What are the Similarities Between AdherensJunctions and Desmosomes?
- Adherens junctions and desmosomes are intercellular junctions.
- They facilitate adhesion and cohesion.
- Both consist of cell adhesion molecules.
- Moreover, they are essential for the development and integrity of vertebrate tissue.
- Both consist of different types of cadherin as cell adhesion molecules.
- Both adherens junctions and desmosomes are anchoring junctions.
What is the Difference Between Adherens Junctions and Desmosomes?
Adherens junctions lack highly ordered structure in their extracellular region, while desmosomes consist of highly ordered structure in their extracellular region. Thus, this is the key difference between adherens junctions and desmosomes. Adherens junctions are always calcium-dependent, while desmosomes are calcium-independent hyper-adhesions. Moreover, adherens junctions do not contain plaque proteins, but desmosomes consist of distinguishable plaque proteins.
The below infographic presents the differences between adherens junctions and desmosomes in tabular form for side-by-side comparison.
Summary – Adherens Junctions vs Desmosomes
Intercellular adhesive junctions are different adhesive structures that provide adhesion, cohesion, and cell communication between cells. Adherens junctions and desmosomes are two significant intercellular adhesive structures present in the body. Adherens junctions lack highly ordered structure in their extracellular region, while desmosomes consist of highly ordered structure in their extracellular region. Adherens junctions regulate different cellular processes such as cell shape, division, growth, apoptosis, and barrier function, but desmosomes are not involved in many cellular functions other than cell cohesion. Moreover, adherens junctions are always calcium-dependent, but desmosomes are calcium-independent hyper-adhesions. So, this summarizes the difference between adherens junctions and desmosomes.
Reference:
1. Garrod, David, and Martyn Chidgey. “Desmosome Structure, Composition and Function.” Biochimica Et Biophysica Acta (BBA) – Biomembranes, Elsevier, 9 Aug. 2007.
2. Tariq, H et al. “Cadherin Flexibility Provides a Key Difference between Desmosomes and Adherens Junctions.” Proceedings of the National Academy of Sciences of the United States of America, U.S. National Library of Medicine.
Image Courtesy:
1. “402 Types of Cell Junctions new” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
2. “Desmosome Cell Junction” By Artwork by Holly Fischer – Cell Biology Slide 23; Epithelia Slide 23 (CC BY 3.0) via Commons Wikimedia