Cell Adhesion Flashcards
What are occluding junctions?
tight junctions
-seal gap between epithelial cell
-allow things to go through the cell and not around
What are adherens junctions?
cell junctions that connects the actin filament bundle in one cell with that of the next cell
What are desmosomes?
cell junctions that connect keratin intermediate filaments in one cell to those in the next cell
What are gap junctions?
cell junctions that allow the passage of small water soluble molecules from cell to cell
What are hemidesmosomes?
cell junctions that anchor intermediate filaments in a cell to the extra cellular matrix
What are actin linked cell-matrix adhesions? (focal adhesions)
cell junctions that anchor actin filament in cell to extracellular matrix
What is the first principle of adhesion?
cells define their capacity for adhesive interactions by selectively expressing plasma membrane receptors
-limited ligand binding activity
-can influence gene expression
What is the second principle of adhesion?
many adhesion proteins bind one main ligand, and many ligands bind a single type of receptor
-however, this is not a hard and fast rule
-integrin family of receptors bind to more than one ligand
What do cadherins normally bind to?
they normally bind to other cadherins on neighboring cells
-this creates a cell to cell interaction
-homophilic interaction
-requires calcium
What is it called when two unlike receptors interact with one another?
heterophilic interaction
What do selectins bind to?
anionic polysaccharides
-bind two different types of cells together
why do integrins stand apart from other CAMs?
b/c they bind to a variety of ligands
What is the transmembrane protein involved with adherens junctions?
cadherins (classic)
What is the transmembrane protein involved with desmosomes?
cadherins
-desmoglein and desmocollin
What transmembrane protein is involved in focal adhesions?
integrin
What transmembrane protein is involved in hemidesmosomes?
integrin alpha6beta4 and type XVII collagen
What type of filament are adherens junctions associated with?
actin
What type of filament are desmosomes associated with?
intermediate filaments
What type of filament are focal adhesions associated with?
actin
What type of filament are hemidesmosomes associated with?
intermediate filaments
What allow the transmembrane proteins to associate with the cytoskeletal filaments?
intracellular anchor proteins
What is the third principle of adhesion?
cells modulate adhesion by controlling the surface density, state of aggregation, and state of activation of their adhesions receptors
What is an example of surface density affecting the expression of transmembrane receptors?
P-selectin is made all the time by endothelial cells and are stored in intracellular compartments
-when inflammation occurs, the P-selectins are brought to the cell surface
What does calcium do to cadherins?
make them more rigid and allow them to bind to cadherins on neighboring cells
What are the intracellular proteins that allow cadherins to bind to the cytoskeletal elements?
catenins
what is the interesting property of cadherins?
they have the ability to sort cells according to type and level of cadherins they express
What is the fourth principle of adhesion?
the rates of ligand binding and dissociation are important determinants of cellular adhesion
Do ligands bind tightly to receptors?
no not really
-allow association and dissociation
-they can be but not always
What is adivity?
the strength of the interaction between ligand and receptor
What is the fifth principle of adhesion?
many adhesion receptors interact with cytoskeleton inside the cell
What is the sixth principle of adhesion?
association of ligands with adhesion receptors can activate intracellular signal transduction pathways, leading to changes in gene expression, cellular differentiation, secretion, motility, receptor activation, and cell division
Extracellular structure of cadherins:
5 cadherin repeats and calcium binds between the cadherins
what are the two types of integrin-related junctions?
focal adhesions and hemidesmosomes
are focal adhesions permanent?
no- they have a dynamic assembly and disassembly
Intracellular anchoring proteins of focal adhesions:
talin and vinculin
What is an adhesion plaque?
spot on the cell membrane where many activated integrin dimers are located
How do focal adhesions change gene expression?
where there is stress on these fibers, the actomyosin (cytoskeletal interaction) gets tugged and can move the nucleus and the contents
What intracellular anchoring proteins are hemidesmosomes interacting with?
plectin and dystonin
where are hemidesmosomes normally found?
basal surface of epithelial cells
role of hemidesmosomes
increase the overall rigidity of epithelial tissues
Why is the basal lamina important in the kidneys?
act as a molecular filter
-determine which molecules will pass into urine from blood
Why is the basal lamina important in the skin?
attach epidermis to dermis
Why is the basal lamina important in the oral mucosa?
critical for attaching epithelium to lamina propria
Why is the basement membrane important in tooth development?
separate ameloblasts and odontoblasts
What is it called when you have a deficiency in GpIIb-IIIa complex?
Glanzmann thrombasthenia
what is it called when you have a deficiency in GpIb?
von Willebrand disease
what does von Willebrand factor bind to on platelets?
GpIb
what binds fibrinogen during platelet adhesion?
GpIIb-IIIa complex
What does P-cadherin do in embryogenesis?
allows the implantation of the embryo to the wall of the uterus
What do N-cadherins do during embryogenesis?
have an important role in determine right and left asymmetry
-also role in determining neural development
What do P-selectins do when activated?
allow the leukocytes circulating to slow down and bind and eventually allow them to move between cells -transendothelial migration
-extravagation
Mutations in integrins, or things that are involved with activating integrins can cause what?
leukocyte adhesion deficiencies
-first symptom can be periodontal disease
What do disintegrins do?
cause dissociation of cells from the extracellular matrix
What are RGD sequences?
known sequences that bind to integrins and competitively bind and cause the dissociation of cell from extracellular matrix
What are ADAMs?
de-adhesion factors that catalyze the shedding of transmembrane proteins
