What is the Difference Between Desmosomes and Hemidesmosomes?

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Desmosomes and hemidesmosomes are both cellular junctions that play crucial roles in cell adhesion and tissue integrity. However, they have distinct functions and structures:

Desmosomes:

  • Facilitate adhesion between adjacent epithelial cells.
  • Involved in intercellular adhesion of epithelial cells.
  • Consist of dense cytoplasmic plaques, which are linked to the cytoskeleton.
  • Contain long carboxy-terminal domains in their cytoplasmic domains, which are thought to be important for regulation of junction assembly and specific cell signaling.
  • Found in cardiac muscle tissue and the gastrointestinal tract.

Hemidesmosomes:

  • Mediate adhesion between basal cells of epithelial tissues and the substratum (basal lamina).
  • Involved in adhesion of epithelia to the underlying extracellular matrix.
  • Also characterized by dense cytoplasmic plaques, but these do not resemble desmosomes as their name suggests.
  • Comprise transmembrane molecules of the cadherin family of calcium-dependent cell-cell adhesion proteins.
  • Contain long carboxy-terminal domains in their cytoplasmic domains, which are thought to be important for regulation of junction assembly and specific cell signaling.
  • Primarily found in keratinocytes, facilitating the adhesion of keratinocytes to the basement membrane.

Despite their differences, desmosomes and hemidesmosomes share some common features, such as being membrane-bound organelles and having a round shape. Both junctions also play a role in cell signaling pathways in addition to their structural functions in tissue integrity.

Comparative Table: Desmosomes vs Hemidesmosomes

Desmosomes and hemidesmosomes are both types of cellular junctions that play crucial roles in maintaining the integrity of tissues and organs. Here is a table comparing their differences:

Feature Desmosomes Hemidesmosomes
Definition Desmosomes are adhesion structures that act as cell-to-cell adhesions. Hemidesmosomes are adhesions that form between cells and the basement membrane.
Location Primarily found in epithelial cells such as the skin and heart muscle. Found in the epidermis of the skin, where they connect cells to the extracellular matrix.
Function Desmosomes ensure cells in organs and tissues that stretch remain connected. Hemidesmosomes anchor cells to the basement membrane, maintaining skin and muscle integrity.
Structure Desmosomes consist of desmoplakin and other proteins that form a plaque. Hemidesmosomes connect the basal surface of an epithelial cell to the underlying basal lamina.
Intermediate Filaments Desmosomes serve as anchoring sites for ropelike intermediate filaments, creating a structural framework of great tensile strength. Hemidesmosomes also connect to intermediate filaments, but their main role is to attach cells to the extracellular matrix.
Disease Connection Damages to desmosomes and mutations in desmosomes can lead to conditions such as arrhythmogenic. Damage to hemidesmosomes can lead to the loss of skin integrity and muscle function, and mutations in hemidesmosome expression can cause epidermolysis bullosa.

In summary, desmosomes are responsible for binding adjacent cells together, while hemidesmosomes anchor cells to the basement membrane. Both these cellular junctions play essential roles in maintaining the structure and function of various tissues in the body.