Cell Adhesion

Question 1

What are occluding junctions?

Answer 1

tight junctions
-seal gap between epithelial cell
-allow things to go through the cell and not around

Question 2

What are adherens junctions?

Answer 2

cell junctions that connects the actin filament bundle in one cell with that of the next cell

Question 3

What are desmosomes?

Answer 3

cell junctions that connect keratin intermediate filaments in one cell to those in the next cell

Question 4

What are gap junctions?

Answer 4

cell junctions that allow the passage of small water soluble molecules from cell to cell

Question 5

What are hemidesmosomes?

Answer 5

cell junctions that anchor intermediate filaments in a cell to the extra cellular matrix

Question 6

What are actin linked cell-matrix adhesions? (focal adhesions)

Answer 6

cell junctions that anchor actin filament in cell to extracellular matrix

Question 7

What is the first principle of adhesion?

Answer 7

cells define their capacity for adhesive interactions by selectively expressing plasma membrane receptors
-limited ligand binding activity
-can influence gene expression

Question 8

What is the second principle of adhesion?

Answer 8

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

Question 9

What do cadherins normally bind to?

Answer 9

they normally bind to other cadherins on neighboring cells
-this creates a cell to cell interaction
-homophilic interaction
-requires calcium

Question 10

What is it called when two unlike receptors interact with one another?

Answer 10

heterophilic interaction

Question 11

What do selectins bind to?

Answer 11

anionic polysaccharides
-bind two different types of cells together

Question 12

why do integrins stand apart from other CAMs?

Answer 12

b/c they bind to a variety of ligands

Question 13

What is the transmembrane protein involved with adherens junctions?

Answer 13

cadherins (classic)

Question 14

What is the transmembrane protein involved with desmosomes?

Answer 14

cadherins
-desmoglein and desmocollin

Question 15

What transmembrane protein is involved in focal adhesions?

Answer 15

integrin

Question 16

What transmembrane protein is involved in hemidesmosomes?

Answer 16

integrin alpha6beta4 and type XVII collagen

Question 17

What type of filament are adherens junctions associated with?

Answer 17

actin

Question 18

What type of filament are desmosomes associated with?

Answer 18

intermediate filaments

Question 19

What type of filament are focal adhesions associated with?

Answer 19

actin

Question 20

What type of filament are hemidesmosomes associated with?

Answer 20

intermediate filaments

Question 21

What allow the transmembrane proteins to associate with the cytoskeletal filaments?

Answer 21

intracellular anchor proteins

Question 22

What is the third principle of adhesion?

Answer 22

cells modulate adhesion by controlling the surface density, state of aggregation, and state of activation of their adhesions receptors

Question 23

What is an example of surface density affecting the expression of transmembrane receptors?

Answer 23

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

Question 24

What does calcium do to cadherins?

Answer 24

make them more rigid and allow them to bind to cadherins on neighboring cells

Question 25

What are the intracellular proteins that allow cadherins to bind to the cytoskeletal elements?

Answer 25

catenins

Question 26

what is the interesting property of cadherins?

Answer 26

they have the ability to sort cells according to type and level of cadherins they express

Question 27

What is the fourth principle of adhesion?

Answer 27

the rates of ligand binding and dissociation are important determinants of cellular adhesion

Question 28

Do ligands bind tightly to receptors?

Answer 28

no not really -allow association and dissociation -they can be but not always

Question 29

What is adivity?

Answer 29

the strength of the interaction between ligand and receptor

Question 30

What is the fifth principle of adhesion?

Answer 30

many adhesion receptors interact with cytoskeleton inside the cell

Question 31

What is the sixth principle of adhesion?

Answer 31

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

Question 32

Extracellular structure of cadherins:

Answer 32

5 cadherin repeats and calcium binds between the cadherins

Question 33

what are the two types of integrin-related junctions?

Answer 33

focal adhesions and hemidesmosomes

Question 34

are focal adhesions permanent?

Answer 34

no- they have a dynamic assembly and disassembly

Question 35

Intracellular anchoring proteins of focal adhesions:

Answer 35

talin and vinculin

Question 36

What is an adhesion plaque?

Answer 36

spot on the cell membrane where many activated integrin dimers are located

Question 37

How do focal adhesions change gene expression?

Answer 37

where there is stress on these fibers, the actomyosin (cytoskeletal interaction) gets tugged and can move the nucleus and the contents

Question 38

What intracellular anchoring proteins are hemidesmosomes interacting with?

Answer 38

plectin and dystonin

Question 39

where are hemidesmosomes normally found?

Answer 39

basal surface of epithelial cells

Question 40

role of hemidesmosomes

Answer 40

increase the overall rigidity of epithelial tissues

Question 41

Why is the basal lamina important in the kidneys?

Answer 41

act as a molecular filter -determine which molecules will pass into urine from blood

Question 42

Why is the basal lamina important in the skin?

Answer 42

attach epidermis to dermis

Question 43

Why is the basal lamina important in the oral mucosa?

Answer 43

critical for attaching epithelium to lamina propria

Question 44

Why is the basement membrane important in tooth development?

Answer 44

separate ameloblasts and odontoblasts

Question 45

What is it called when you have a deficiency in GpIIb-IIIa complex?

Answer 45

Glanzmann thrombasthenia

Question 46

what is it called when you have a deficiency in GpIb?

Answer 46

von Willebrand disease

Question 47

what does von Willebrand factor bind to on platelets?

Answer 47

GpIb

Question 48

what binds fibrinogen during platelet adhesion?

Answer 48

GpIIb-IIIa complex

Question 49

What does P-cadherin do in embryogenesis?

Answer 49

allows the implantation of the embryo to the wall of the uterus

Question 50

What do N-cadherins do during embryogenesis?

Answer 50

have an important role in determine right and left asymmetry -also role in determining neural development

Question 51

What do P-selectins do when activated?

Answer 51

allow the leukocytes circulating to slow down and bind and eventually allow them to move between cells -transendothelial migration -extravagation

Question 52

Mutations in integrins, or things that are involved with activating integrins can cause what?

Answer 52

leukocyte adhesion deficiencies -first symptom can be periodontal disease

Question 53

What do disintegrins do?

Answer 53

cause dissociation of cells from the extracellular matrix

Question 54

What are RGD sequences?

Answer 54

known sequences that bind to integrins and competitively bind and cause the dissociation of cell from extracellular matrix

Question 55

What are ADAMs?

Answer 55

de-adhesion factors that catalyze the shedding of transmembrane proteins