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28 Cards in this Set

  • Front
  • Back
Why is cell adhesion important?
development, survival, and organization of tissues
What are integrins? (
-proteins located on the cell surface

-attaches cytoskeleton (inside cell) to extracellular matrix outside the cell

-signal transduction from ECM to inside the cell
What are integrins used for?
-cell motility
-transmembrane heterodimers

-binds to a matrix protein outside the cell and to the actin cytoskeleton inside the cell creating a transmembrane linker

-alpha subunit is cleaved into one small transmembrane domain, and 1 large extracell domain that has 4 calcium binding sites

- the 2 domains can be reduced bc held together by dsulfide bond

-Beta subunit is 1 chain w/ cysteine rich region
why cation binding sites?
-type of divalent cation can influence both the affinity and specificity of the binding of an integrin to its ligand
What are integrins used for?
-cell motility
-Signal transduction from the ECM to the cell

-Connection with ECM molecules can cause a signal to be relayed into the cell through protein kinases that are connected with the intracellular end of the integrin molecule.

-these signals promote cell growth, survival and proliferation
How are integrins involved in adhesion and signaling events?
extracell talks to inside cell by lateral shifts and conf. changes that leads to clustering
What disease states are associated with a loss of cellular adhesion?
-Beta 4 mutation (JEB):blistering disease

-Beta 3 mutation in blood platelets can't bind matrix protein fibrinogen used for blood clotting so glanzmann's disease causes excess bleeding
How are integrins activated?
outside in: ligand binding alters integrin conformation

inside out: signals inside cell alter integrin affinity for ligand (possible phosphorylation of cytoplasmic tails of integrin) that induces conf. chang of extracell domain (calcium shifts)
why are there so many integrin combinations ?
-they are all tissue specific

- very different distributions

-a variety of heterodimers can be formed from many alpha and beta subunits

-beta 1 has huge phenotype
How can integrins be turned off ?
degrade them
what integrins are associated with epethilial cancers ?
alpha 6 and alpha 3 laminin receptors
How are integrins involved in cell migration?
integrin is part of the focal adhesion, a little back from the leading edge, connected to actin fillaments which coordinate pushing and pulling of cytoskeleton--nucleus is included
what normal processes require cell migration?
wound healing
new vessels
blood clotting
immunes system
what cellular components are essentail for cell migration?
actin fillaments, integrins, kinases, filopodia, lamellopodia
Give some examples of abnormal cell migration
metastisis, excessive bleeding
what are the major dependent steps in metastasis
1)migrate in the stroma
2)migrate along the extracellular matrix
3)intravisate, extravisate
How are migration signals coordinated with growht signals
-receptor tyrosine kinases

-you won't get migration unless you have both growth factors and activated integrins working together
when a cell migrates what components are in the leading strand

filopdia:contains bundles of actin
How is the leading edge of the cell different from the lagging edge?
leading edge: electon dense (protein concentration)-interact with extracellmatrix

lagging edge: no contact
what is Epidermolysis Bullosa?
-blistering caused by mutation

divided into:

-(epidermal/simplex)mild trauma,hemidesmosome changes

-JEB: Junctional types have blisters separateing at the lamina lucuda of the basement membrane ,includes A6B4 integrin, laminin

-dermal type with blisters below basement membrane (damgage to anchoring fibrils)
Name the genes that are mutated leading to JEB
-collagen fibrils
-laminins-> extracellular ligand
what determines the severity of the disease?
what the position is for the defect
Most integrin knock-out phenotypes are lethat after birth of the mouse. Why are the B1 integrin gene mutations lethal at stage 5.5?
B1 forms dimers with many distinct alpha subunits, so therfore it is needed
JEB patients may benefit from the use of keratinocyte stem cells. What are the benefits and risks of such a strategy?
-might get too much adhesion
-it needs to be very directed in terms of location amount and percistence
what disease is characterized by a defect in collagen VII
dystrophic/ dermal epidermolysis bullosa

-blistering below basal lamina
what molecules are involved in autoimmune blistering disease
Postulate why autoimmune blistering diseases are associated with malignancy?
promote inflammation, chronic wound healing, disorganization of structure