Hemidesmosome

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Hemidesmosome
Lamc2 -/- tracheas (b) are less organized, the intracellular component is more diffuse, and the lamina densa directly below the hemidesmosomal areas lacks the electron density seen in the littermate control (arrows). From Nguyen et al., 2006.[1]
Details
Identifiers
Latinhemidesmosoma
MeSHD022002
THH1.00.01.1.02029
FMA67415
Anatomical terminology]

Hemidesmosomes are very small stud-like structures found in

epidermis of skin that attach to the extracellular matrix. They are similar in form to desmosomes when visualized by electron microscopy, however, desmosomes attach to adjacent cells. Hemidesmosomes are also comparable to focal adhesions, as they both attach cells to the extracellular matrix. Instead of desmogleins and desmocollins in the extracellular space, hemidesmosomes utilize integrins. Hemidesmosomes are found in epithelial cells connecting the basal epithelial cells to the lamina lucida, which is part of the basal lamina.[2] Hemidesmosomes are also involved in signaling pathways, such as keratinocyte migration or carcinoma cell intrusion.[3]

Structure

Hemidesmosomes can be categorized into two types based on their protein constituents. Type 1 hemidesmosomes are found in

BPAG2 (also known as BP180 or type 17 collagen).[2] Type 1 hemidesmosomes are found in stratified and pseudostratified epithelial tissue. Type 2 hemidesmosomes contain integrin α6β4 and plectin without the BP antigens.[4]

Hemidesmosomes have two membrane-spanning components: Integrin α6β4 and BPAG2. Integrin α6β4 operates as a laminin-332 receptor. Integrin α6β4 is composed to two α and β subunit dimers. The larger β4 subunit has domains that bind to fibronectin III and calcium. The α6 subunit binds to extracellular BP180, CD151 and laminin-322. When integrin α6β4 binds to Plectin 1a and BPAG1, it associates with the keratin intermediate filaments in the cytoskeleton.[2]

Hemidesmosomes are linked to keratin by plectin isoform 1a from the

isoforms that binds to integrin α6β4, BPAG2 and keratin 5 and 14. The main role of BPAG1e is for hemidesmosome stability.[2]

Diseases

Keeping the basal epidermal keratinocytes attached to the basal lamina is vital for skin homeostasis. Genetic or acquired diseases that cause disruption of hemidesmosome components can lead to skin blistering disorders between different layers of the skin. These are collectively coined epidermolysis bullosa, or EB. Typical symptoms include fragile skin, blister development, and erosion from minor physical stress.[2] However, the disease also can manifest as erosions on the cornea, trachea, gastrointestinal tract, esophagus, muscular dystrophy and muscular deformity.[5]

Mutations in 12 different genes that code for parts of the hemidesmosome have led to epidermolysis bullosa.

papillary dermis separate from the anchoring fibrils. This is caused by mutations in the collagen 7
gene.

See also

References

  1. PMID 16483354
    .
  2. ^
    PMID 25487405
    .
  3. PMID 16581764
    .
  4. PMID 10413585
    .
  5. S2CID 221861310
    .
  6. PMID 24690439
    .
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