The main difference between hemidesmosomes and desmosomes is that hemidesmosomes resemble half a desmosome and mediate adhesion between the basal layer of epithelial tissue and substratum, whereas desmosomes facilitate the adhesion between epithelial cells.
Hemidesmosomes and desmosomes are major types of cell surface attachment sites. They are important in cell-cell adhesion.
Key Areas Covered
1. What are Hemidesmosomes
– Definition, Structure, Function
2. What are Desmosomes
– Definition, Structure, Function
3. Similarities – Hemidesmosomes and Desmosomes
– Outline of Common Features
4. Difference Between Hemidesmosomes and Desmosomes
– Comparison of Key Differences
Key Terms
Desmosomes, Hemidesmosomes
What are Hemidesmosomes
Hemidesmosomes are very small, stud-like structures occurring in keratinocytes that attach to the extracellular matrix of the skin. They attach basal epithelial cells to the lamina lucida, a part of the basal lamina. They are also multiprotein complexes made up of proteins called integrins, which are transmembrane receptors facilitating cell-cell adhesion. According to the protein constituents, there are two types of hemidesmosomes. They are type 1 hemidesmosomes and type 2 hemidesmosomes. Type 1 hemidesmosomes occur in the stratified epithelium and pseudostratified epithelium. Integrin α6β4, P1a, tetraspanin protein CD151, BPAG2, and BPAG1e are the five types of elements found in type 1 hemidesmosomes. Moreover, the elements of the type 2 hemidesmosomes are integrin α6β4 and plectin.
Figure 1: Hemidesmosomes
Furthermore, Integrin α6β4 and BPAG2 are the two membrane-spanning components of the hemidesmosomes. Meanwhile, integrin α6β4 and P1a form the core of the hemidesmosome complex. Here, plectin is a cytoskeletal linker protein associated with hemidesmosomes.
What are Desmosomes
Desmosomes are structures of cell-cell adhesion. They are spot-like adhesions that are randomly arranged on the lateral side of the plasma membrane. The main importance of desmosomes is that they are stronger cell-cell adhesions providing mechanical strength to the cells in the cardiac muscle tissue, gastrointestinal mucosa, bladder tissue, and in epithelia. The key feature of desmosomes is the presence of desmosome-intermediate filament complexes (DIFC), a network composed of cadherin proteins, intermediate filaments, and linker proteins. DIFC contains three regions: the extracellular core region, the outer dense plaque, and the inner dense plaque.
Figure 2: Desmosomes
Moreover, the two main types of cadherin proteins that occur in the extracellular core region are desmoglein and desmocollin. The outer dense plaque contains desmoglein and desmocollin’s intracellular ends, while the inner dense plaque contains the C-terminus end of desmoplakin and their attachment to keratin intermediate filaments.
Similarities Between Hemidesmosomes and Desmosomes
- Hemidesmosomes and desmosomes are two types of cell-cell adhesions important for the attachment of cells.
- They occur in tissues and epithelia.
Difference Between Hemidesmosomes and Desmosomes
Definition
Hemidesmosomes refer to a specialization of the plasma membrane of an epithelial cell that is similar to half a desmosome and serves to connect the basal surface of the cell to the basement membrane, while desmosomes refer to a specialized structure of the cell membrane, especially of an epithelial cell that serves as a zone of adhesion to anchor contiguous cells together.
Occurrence
Hemidesmosomes occur in keratinocytes, while desmosomes occur in tissues that experience intense mechanical stress, such as cardiac muscular tissue, gastrointestinal mucosa, bladder tissue, and epithelium.
Anatomy
Moreover, hemidesmosomes are multiprotein complexes that facilitate stable adhesion of basal epithelial cells to the underlying basement membrane, while desmosomes are made up of distinct, cadherin- and plaque-associated complexes forming in the cytoplasm and delivered into the regions of cell-cell contact for the final assembly.
Function
Hemidesmosomes involve in the mechanical stability of cells, while desmosomes maintain tissue architecture and provide sites for the binding of intermediate filaments.
Type of Adhesion
Hemidesmosomes attach keratinocytes to the extracellular matrix, while desmosomes attach cells to adjacent cells.
Adhesion Proteins
In addition, hemidesmosomes use integrins as the adhesion proteins, while desmosomes use desmogleins and desmocollins as the adhesion proteins.
Conclusion
In brief, hemidesmosomes and desmosomes are two types of cell-cell adhesions important for the mechanical strength of the tissue. Hemidesmosomes are cell-cell adhesions that are half of a desmosome. They mainly occur in keratinocytes. In addition, hemidesmosomes are multiprotein complexes that provide mechanical stability for the cells. They attach cells to the extracellular matrix. On the other hand, desmosomes are a type of cell-cell adhesion that occur in cardiac muscular tissue, gastrointestinal mucosa, bladder tissue, and epithelium. They are cadherin- and plaque-associated complexes. However, desmosomes are important in tissue architecture and provide binding sites for intermediate filaments. Desmosomes attach cells to the adjacent cells. Therefore, the main difference between hemidesmosomes and desmosomes is their structure and function.
References:
- Green KJ, Jones JC. Desmosomes and hemidesmosomes: structure and function of molecular components. FASEB J. 1996 Jun;10(8):871-81. doi: 10.1096/fasebj.10.8.8666164. PMID: 8666164.
- Walko G, Castañón MJ, Wiche G. Molecular architecture and function of the hemidesmosome. Cell Tissue Res. 2015 May;360(2):363-78. doi: 10.1007/s00441-014-2061-z. Epub 2014 Dec 9. PMID: 25487405; PMCID: PMC4544487.
Image Courtesy:
- “Ultrastructure of tracheal hemidesmosomes in mice.” By Nguyen NM, Pulkkinen L, Schlueter JA, Meneguzzi G, Uitto J, Senior RM. – Own work (CC-BY SA 2.0) via Commons Wikimedia
- “Desmosome cell junction en” By Mariana Ruiz LadyofHats – Own Work (Public Domain) via Commons Wikimedia
Leave a Reply