24 Questions
What type of proteins bind via anchor proteins to intermediate filaments?
Desmocollin and Desmoglein
What is the primary function of desmosomes?
To provide mechanical strength to tissues
Which of the following proteins is NOT part of the cytoplasmic plaque?
Desmocollin
What is the result of antibodies binding to desmosomal cadherins in autoimmune diseases such as pemphigus?
Disruption of desmosomes leading to skin blistering
What is the structure that provides attachment sites for intermediate filaments in desmosomes?
Cytoplasmic plaque
Which of the following tissues is NOT typically abundant in desmosomes?
Brain tissue
What is the function of Desmoglein and Desmocollin in desmosomes?
To link adjacent cells together
What is the name of the autoimmune disease that affects skin epithelial cells due to antibodies against desmosomal cadherins?
Pemphigus
What is the result of a severe Desmoglein 3 defect?
Leakage of body fluids into the loosened epithelium
What type of intermediate filaments are found in epithelial cells?
Keratin filaments
What is the function of anchoring junctions?
Cell-cell and cell-matrix adhesion
What is the characteristic of hemidesmosomes?
They have a single dense plaque on the cytoplasmic surface
What is the function of integrins in hemidesmosomes?
Binding to laminin protein in the basal lamina
What is the effect of autoantibodies attacking type XVII collagen?
Blisters in the skin
What is the result of mutations in plectin?
Skin blisters and muscular dystrophy
What is the function of hemidesmosomes in cell-matrix adhesion?
To anchor loops of intermediate filaments
What type of junction is characterized by actin filament attachment sites?
Adherens junctions
What type of collagen is targeted by autoantibodies in bullous pemphigoid?
Type XVII collagen
What is the role of integrins in focal adhesions?
To bind to components of the extracellular matrix
What is the consequence of mutations in plectin?
Skin blisters
What type of filaments are attached to focal adhesions?
Actin filaments
What is the function of anchoring junctions?
To anchor cells to the extracellular matrix
What is the function of the cytoplasmic domain of the integrin in focal adhesions?
To bind indirectly to actin filaments
What type of junctions are characterized by the presence of a dense plaque on the cytoplasmic surface?
Hemidesmosomes
Study Notes
Anchoring Junctions
- Anchoring junctions can be subclassified according to the cytoskeletal element involved
- Two types of anchoring junctions:
- Actin filament attachment sites
- Cell-cell junctions (ADHERENS JUNCTIONS)
- Cell-matrix junctions (FOCAL ADHESIONS)
- Intermediate filament attachment sites
- Cell-cell junctions (DESMOSOMES)
- Cell-matrix junctions (HEMIDESMOSOMES)
- Actin filament attachment sites
Desmosomes
- Desmosomes are strongest points of cell adhesion that provide mechanical binding
- Most abundant in tissues that are exposed to mechanical stress (Epidermis of the skin, heart muscle)
- Cell to cell binding depends on cadherin family of proteins called desmoglein and desmocollin
- Desmosomes contain plaque-shaped structures on the cytoplasmic face of the junction which provide attachment sites for intermediate filaments
- Plaque proteins: plakoglobins, desmoplakins, plakophilins
Hemidesmosomes
- Hemidesmosomes resemble desmosomes morphologically
- Hemidesmosomes have only a single dense plaque on the cytoplasmic surface of the hemidesmosome (hemi=half) that anchors loops of intermediate filaments
- Hemidesmosomes connect epithelial cells to the basal lamina
- Integrin (α6β4) and type XVII collagen (also called BPAG2) attach to the basal lamina
Importance of Desmosomes and Hemidesmosomes
- In a blistering skin disease called bullous pemphigoid, autoantibodies attack type XVII collagen
- Mutations in plectin cause skin blisters associated with late-onset muscular dystrophy
- Cataract, heart malformations, and skin blistering are examples of diseases related to desmosome and hemidesmosome dysfunction
This quiz covers the structure and function of cells, including desmoglein, pemphigus vulgaris, and types of intermediate filaments in different cell types.
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