ECM & Cell Interactions

Question 1

Outline the primary structures and functions of the five different types of cell junctions

Answer 1

1) Tight juntcions: limits movement of integral protein movement; maintains the polarity of the cell
2) Gap junctions: connexins between cells allow small molecules to flow freely between
3) Adherens junctions: adhere to cells using actin, cadherin family
4) hemi-desmosomes: anchor cells to basal lamina, connected to intermediate filaments
5) desmosomes: anchor cells to one another, uses intermeditae filaments within cell, cadherin family

Question 2

Explain the roles of adhesion receptors, CAMs and adapter proteins in cell adhesion

Answer 2

CAMs anchor to one another
adhesion receptors adhere to ECM
adapter proteins connect to cytoskeleton

Question 3

Describe the three major classes of proteins found in the extracellular matrix

Answer 3

1) proteoglycans: glycosylated proteins, repeats of disaccharides, negatively charged
2) collagens: triple helix formed in secretory pathway
3) multiadhesive matrix proteins: laminins, entactin, important for strucrture of ECM

Question 4

Describe the functions of the extracellular matrix (ECM)

Answer 4

1) provide structure for cells in a tissue to adhere
2) provide cushioning in cartilage
3) provides a lattice on which cells can move-particularly during embryonic development

Question 5

Give examples of specific protein families found in each type of cell junction

Answer 5

Cadherin Family: adherins and desmosomes
Claudin, occludin, & JAM families: Tight junctions
Integrin family: hemidesmosomes
Connexin family: Gap junctions

Question 6

Outline the inherited diseases resulting from defects in ECM components or adhesive proteins

Answer 6

Collagen: scurvy, ehlers-danlos, osteogenesis, alport syndrome, menke’s disease
Multiadhesive: Marfan’s syndrome