L14: Cell adhesion part 2

Question 1

hemidesmosomes?

Answer 1

• Integrin containing adhesion linking
  ECM to intermediate filaments
• Intracellular domain of integrins
  linked to keratin via plectins
  (anchor proteins)

Question 2

gap junctions?

Answer 2

Channel forming junctions
* Main components are connexons
- consist of hexamers of connexins:
transmembrane proteins that
connect to form channels and can
open and close
* Allow passage of ions and small
2nd messenger molecules between
cells (1kD or less) and electrical signals.
* Important in epithelium, heart
muscle (signal to contract) and
neuronal synapses

Question 3

cell-cell junctions in EMT?

Answer 3

Epithelial-mesenchymal
transition (EMT) = change
from organised, polarised
epithelium to single
migratory cells. Proposed to
be an early step in cancer
progression
Loss of E-cadherin from cell-
cell contacts proposed to
initiate EMT as it weakens
epithelial cell contacts

Many epithelially-derived cancers have a loss
of function mutations in, or reduced
expression levels of, E-cadherin

Epithelial cells undergoes dysplasia (uncontrollable growth) form carcinoma, cells break away into blood move

Question 4

Cell junctions in skin blistering diseases?

Answer 4

Many skin blistering diseases are the result
of mutations or changes in expression of
proteins important in cell-cell adhesion
Examples include:
Pemphigus vulgaris: autoantibodies against
desmogleins 1+3 (in desmosomes). Leads
to separation of keratinocytes from each
other, and from the basal layer of the
epidermis
Epidermolysis bullosa: genetic conditions,
mutations in COLVII or Keratin genes
leading to reduced HD stability, reduced
adhesion to ECM and skin blistering