Lecture 5 Flashcards
Epithelial Tissues: Cell Adhesion Molecules (CAMs) (31 cards)
What are the two components of the basement membrane?
- basal lamina
- reticular lamina
What is the origin of each component of the basement membrane?
- the basal lamia is produced by the epithelium
- the reticular lamina is produced by connective tissue
What is the basal lamina composed of?
- laminin
- fibronectin
- type IV collagen
- entactin (nidogen)
- proteoglycans
What type of collagen is associated with the basal lamina?
Type IV collagen
What is the major component of the basal lamina?
laminin
What are the characteristics of laminin?
- made of three chains (alpha, beta, and gamma)
- has binding sites for 1. integrins (cell surface receptors), 2. type IV collagen, and 3. other adhesion proteins (enactin and proteoglycans)
What are some characteristics of fibronectin?
- protein made of two polypeptide chains that are cross-linked by disulfide bonds
- there are two forms of fibronectin: cellular and plasma
What other components does fibronectin bind to?
fibronectin has binding sites for 1. heparin 2. integrins 3. collagen and 4. fibrin
What are the characteristics of calcium dependent and calcium independent CAMs?
- calcium dependent CAMs include cadherins and selectins
- calcium independent CAMs include integrins and immunoglobulin superfamily molecules (Ig superfamily)
What are the three classes of cadherins?
- E-cadherins
- N-cadherins
- P-cadherins
Where are each of the three cadherin classes found?
- E-cadherins are found in the epithelium
- N-cadherins are found in the nerve cells
- P-cadherins are found in the placenta
What is the most common type of cadherin?
E-cadherins
Which type of cadherin is found to be associated with invasive behavior of tumor cells?
E-cadherins, the loss of e-cadherins is associated with the invasive behavior of tumor cells
Why are selectins classified as lectins?
selectins are classified as lectins because they bind to carbohydrates
What is the function of selectins?
selectins are involved in the movement of leukocytes in the blood to the surrounding tissues (extravasation)
Explain the major function of integrin.
integrin proteins bind to the extracellular matrix as well as the internal cytoskeleton
What are catenins?
catenins are small proteins that serve as the interface between the cadherins that hold adjacent cells together, and the actin cytoskeletons of those cells.
What are the three classes of selectins?
- P-selectins (platelets)
- E-selectins (activated endothelial cells)
- L-selectins (leukocytes)
What is the amino acid sequence in fibronectin and laminin that integrins interact with?
RGD (Arg-Gly-Asp)
What are the members of the Ig superfamily?
- N-CAM (neural adhesion molecules)
- I-CAM and I-CAM-2
What are the three categories of junctional complexes?
- adherens
- occludens
- gap junctions
How can you distinguish between zonula and macula types of junctional complexes?
- Zonula complexes travel all the way around the cell and link all neighboring cells to the central cell. (belt-like complexes)
- Macula junctions are thought of as a “spot” or “snap-like” junction. Maculas include desmosomes and hemidesmosomes
Describe the molecular structure of the zonula and macula adherentes.
- Zonulas have actin filaments linked by a catenin complex to a central cadherin. (afadin-nectin complex)
- Maculas have keratin intermediate filaments connected to cytoplasmic dense plaques on either side of a central cadherin
Describe the molecular structure of a hemidesmosome.
A hemidesmosome consists of a cytoplasmic plate that is associated with intermediate filaments such as keratin. A membrane plaque links the hemidesmosome to the basal lamina with anchoring filaments.
