What is the difference between desmosomes and hemidesmosomes?

Desmosomes and hemidesmosomes are two important types of anchoring junctions that help maintain the structural stability of tissues. These junctions are mainly found in epithelial tissues and other tissues that experience mechanical stress like heart muscles and skin. While both are involved in anchoring functions and connect to intermediate filaments inside the cell, they still differ based on several aspects such as:

1. Based on Definition and Location

Desmosomes are specialized intercellular junctions that form strong adhesion between two adjacent cells. They are mainly located in tissues that need to withstand stretching and pressure, such as cardiac muscles and stratified epithelium.

Hemidesmosomes, on the other hand, are junctions that connect the basal surface of epithelial cells to the basement membrane. They are especially found in the skin, where they attach the lower layer of epidermis to the dermis.

2. Based on Shape and Structure

Desmosomes appear as round, button-like or disc-shaped structures located at the lateral surfaces of cells where two cells are tightly joined.

In contrast, hemidesmosomes appear as half-disc or semi-circular structures located only at the basal surface of the epithelial cells, attaching them to the basement membrane.

3. Based on Visibility under electron microscope

Under an electron microscope, desmosomes appear as symmetrical dense plaques on both adjacent cell membranes, giving a mirror-like image.

Hemidesmosomes, however, appear asymmetrical and are seen only on one side, at the basal plasma membrane of the cell, where it attaches to the extracellular basement membrane.

4. Based on Type of Connection

Desmosomes form a cell-to-cell connection. They link the plasma membrane of one cell to the plasma membrane of another neighboring cell.

Hemidesmosomes form a cell-to-extracellular matrix connection. They link the epithelial cell to the basement membrane, not to another cell.

5. Based on Protein Composition

Desmosomes use cadherin family proteins, especially desmoglein and desmocollin, which extend from the cell membrane and form homophilic interactions with cadherins of the neighboring cell. Inside the cell, these proteins connect to plaque proteins such as plakoglobin, plakophilin and desmoplakin, which in turn anchor to keratin intermediate filaments.

Hemidesmosomes use integrin family proteins, mainly α6β4 integrins, which bind to laminin-332 in the basal lamina. Internally, integrins connect to proteins like plectin and BP230 (bullous pemphigoid antigen 1), which bind to keratin intermediate filaments.

6. Based on Interaction Type

Desmosomes use homophilic interactions between cadherin proteins, like desmoglein and desmocollin, that bind similar proteins on neighboring cells.

Hemidesmosomes use heterophilic interactions, where integrins on the basal cell surface bind to different extracellular proteins like laminin in the basement membrane.

7. Based on Function

Desmosomes provide mechanical strength and stability between adjacent cells. They act like spot welds or rivets and help resist shearing forces.

Hemidesmosomes provide anchorage to the basement membrane and help in cell-matrix adhesion, preventing the detachment of epithelial cells from the underlying connective tissue.

8. Based on Diseases Involved

Desmosomal defects can cause pemphigus vulgaris, an autoimmune disorder where antibodies target desmogleins, leading to loss of cell adhesion and blistering.

Hemidesmosomal defects can lead to bullous pemphigoid, where antibodies target proteins like BP230 or BP180, causing separation of the epidermis from the dermis.
Desmosomes and hemidesmosomes are two important types of anchoring junctions that help maintain the structural stability of tissues. These junctions are mainly found in epithelial tissues and other tissues that experience mechanical stress like heart muscles and skin. While both are involved in anchoring functions and connect to intermediate filaments inside the cell, they still differ based on several aspects such as:








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