Junctions Flashcards
Integrin
Transmembrane protein that ties the extracellular matrix to the cell cytoskeleton
“Velcro Effect” with integrins
bind with low affinity but in high numbers
What is the alpha subunit of an integrin mostly responsible for?
Binding specificity
What is the beta subunit of an integrin mostly responsible for?
interactions with the cytoskeleton
Cofactors necessary for integrins
Mg2+ or Mn2+
Which two proteins connect the beta subunit of integrin to actin filaments in the cytoskeletin?
Talin and α-actinin
Integrin binding to the cytoskeleton causes… (3)
- Increase in intracellular pH
- Increase in intracellular Ca2+ levels
- Tyrosine phosphorylation of proteins
Which cell surface protein has no enzymatic activity?
integrins
Contractile actin bundles attached to integrins/focal adhesions
Stress fibers
Extracellular matrix anchoring point of integrins
focal adhesions
Leukocyte Adhesion Deficiency
Loss of beta-2 integrins used for adhesion. Susceptibility to bacterial infection.
Missing beta-3 integrin in which platelets and fibrinogen cannot bind to initiate clots; patients bleed excessively
Glanzmann’s disease
aIIb b3 (integrin) antagonists are used for…
Preventing heart attacks and strokes. (they block platelet aggregation)
Three proteins involved in inflammatory cell adhesion
- Selectins
- ICAMs
- Integrins
Selectin
cell-surface carbohydrate-binding proteins synthesized by endothelial cells.
Three types of selectins
- E-selectin (endothelial)
- P-selectin (platelets)
- L-selectin (WBCs)
What two things bind to initiate the weak adhesion between WBCs and endothelial cells?
Selectins and oligosaccharides
What two things bind to strengthen initial binding of WBCs and endothelial cells?
ICAMs and integrins
What does ICAM stand for?
Intercellular Adhesion Molecules
Transmembrane glycoprotein promoting cell adhesion by homophillic binding
Cadherin
What does cadherin binding depend on?
Ca2+
What is required to bind cahderins to the actin cytoskeleton?
alpha and beta catenin
Binding chain of cadherins to cytoskeleton
Cadherin - beta catenin - alpha catenin - actin filaments
Where does p120 bind to provide stability?
cytoplasmic domain of cadherin
