REINHART 4

Question 1

what is the structure of P selectin

Answer 1

binds to actin filaments through anchor proteins in the cytosol
has a lectin domain and an EGF like domain in the ECM (extracellular matrix)
it is calcium dependent

Question 2

what are the different types of selectins

Answer 2

oligosaccharide binding proteins
L selectin=lymphocytes (white blood cells)
E selectin= activated endothelial cells
P selectin=platelets, endothelial cells

Question 3

where are endothelial cells found?

Answer 3

present in the intima layer of blood vessels

Question 4

what do lymphocytes do and how do they move through the blood stream

Answer 4

remove impurities
constantly circulate
extremely fast
need to slow down

Question 5

what happens at the inflammation site

Answer 5

endothelial cells express selectins, oligosaccharides are located on lymphocytes

Question 6

what is the nature of the bond between selectins and oligosaccharides

Answer 6

not a very strong integration

Question 7

how are lymphocytes pulled out of the blood vessels into the tissue?

Answer 7

white blood cells roll along the endothelial cells, and by strong interaction (integrin dependent) they have a strong interaction
but they move so fast that there is sequential unbinding and binding.
this makes the blood cells roll
till they are slowed down enough and go to the inflamed tissue to carry out their function, exit the blood vessel

Question 8

what is the structure of calcium independent cell adhesion molecules

Answer 8

different types of ways they are attached to the membrane (long C terminus, short C terminus, GPI anchor, or not attached at all)
have a fibronectin type III domain
have an Ig like domain
have disulfide bonds that hold them together

Question 9

what are disulfide bonds indicative of

Answer 9

extracellular domains

Question 10

what two proteins are frequently co expressed together?

Answer 10

cadherins and ig like cell adhesion molecules

Question 11

what are the different types of cell adhesion molecules

Answer 11

N CAM (neural) = fine tuning of interactions during development and regeneration
I CAM: intercellular
V CAM: vascular

Question 12

what are the non junctional adhesion mechanisms (transient) mechanisms of cell attachment?

Answer 12

cell matrix adhesion:
integral membrane proteoglycan
integrins
cell cell adhesion:
cadherins
Ig like CAMs
itegrins
selectins

Question 13

what are the different types of junctional adhesion mechanisms (permanent)?

Answer 13

cell matrix adhesion
hemidesmosomes (integrins)
focal adhesions (integrins)
cell cell adhesion:
actin filaments
intermediate filaments
tight junctions (claudins)
adhesion belt (cadherins)
desmosomes (cadherins)
gap junction (connexins)

Question 14

what subunits do integrins possess?

Answer 14

alpha and beta subunits
heterodimers

Question 15

in which types of organisms are integrins not found?

Answer 15

prokaryotes
plants
fungi

Question 16

how many units of each subunit of integrins do C. elegans have?

Answer 16

two alpha subunits and one beta subunit -> form two integrins

Question 17

how many units of each subunit of integrins do vertebrates and how many theoretical possibilities does that make?

Answer 17

18 alpha subunits
8 beta subunits
18*8=144 theoretical possibilities

Question 18

how many different integrins do vertebrates have?

Answer 18

24 integrin heterodimers

Question 19

what do integrins participate in?

Answer 19

cell matrix adhesion
cell cell adhesion
cell aggregation

Question 20

what do leukocyte specific receptors do?

Answer 20

cell cell recognition
recognise IG superfamily counter receptors

Question 21

what do collagen receptors do?

Answer 21

recognised ECM molecules

Question 22

what do laminin receptors do?

Answer 22

major proteins in basement membrane

Question 23

what do RGD receptors do?

Answer 23

RGD motifs in ECM motifs

i dont really know what i was trying to say with this one

Question 24

how are the subunits that can bind to multiple things made to be different for each of those binding combinations?

Answer 24

alternative splicing

Question 25

what do integrins need to work?

Answer 25

calcium

Question 26

what is the structure of integins

Answer 26

very small C terminus in the cytosol (20-50AAs)
alpha subunit:
Furin cleavage, held together with disulfide bond
alpha chain
very large N terminus doain
beta subunit:
cysteine rich domains
beta chain
matrix binding domain with mental binding sites
the side is 90-160kDa

Question 27

what types of TM proteins are integrins?

Answer 27

type I: C in cytosol N, in matrix

Question 28

what are most integrins connected to and how?

Answer 28

connected via intracellular anchor proteins to actin (except a6b4 intermediate filaments which bind laminin)

Question 29

what does RGD stand for and what are the charges?

Answer 29

R: arginine, positively charged
G: glycine, neutral
D: aspartic acid, negatively charged

Question 30

what can be added to RGD to make a synthetic circular RGD

Answer 30

phenylalanine, to make cyclo RGDF

Question 31

what amino acid makes contact with the metal on the beta head domain

Answer 31

aspartic acid

Question 32

what do integrin ligand often contain

Answer 32

accessory or synergy sites for receptor binding

Question 33

what sites does fibronectin have

Answer 33

fibronectin is an integrin ligand
synergy site (Fn9)
RGD (Fn10)
RGD integrin binding site domain= how it binds to integrin

Question 34

how do unbound integrins go through the plasma membrane

Answer 34

diffuse freely

Question 35

how are integrins activated when they are not constitutively active

Answer 35

extracellular ligand binding: outside in activation and/or from within the cell via the integrin cytoplasmic tail
inside out activation

Question 36

what are not constitutively active integrins important for?

Answer 36

cell aggregation (adhesion of circulating platelets to soluble matrix)
cell cell adhesion (leukocytes and inflammation)

Question 37

what are the different conformation of when the ligand is bound vs unbound

Answer 37

unbound: bent, inactive
bound: straight, active

Question 38

how does outside in integrin activation happen

Answer 38

via extracellular ligand binding to the bend inactive conformation (weak interaction)
straightening of alpha and beta chains
ligand will bind much stronger
conformational change in beta subunit head domain
separation of the entire alpha and beta subunits (move away from each other)
active integrin

Question 39

which integrin mediates blood platelet aggregation

Answer 39

aIIb3
via binding to fibrinogen
the activation of this integrin is necessary

Question 40

how does the activation of aIIb3 integrin happen?

Answer 40

via exposure to collagen IV or thrombin (outside blood vessels)

Question 41

what happens once aIIb3 integrin is activated?

Answer 41

binds fibrinogen, and then you have the formation of a blood clot

Question 42

what is the size of integrin cytosolic domains?

Answer 42

generally less than 50 amino acids

Question 43

what is the function of the cytosolic domain of integrin

Answer 43

• sites of interaction with, and linkage to, the cytoskeletal and signalling partners of integrins
• the cytoplasmic domains can regulate the activation state of integrins

Question 44

what does the deletion of the conserved membrane proximal segment from either subunit lead to

Answer 44

activation

Question 45

what do point mutations in some of the cytosolic domain sequences lead to?

Answer 45

activation

Question 46

what does talin do?

Answer 46

binds to beta subunit
disrupts the ionic salt bridge ->
separation of alpha and beta subunits
activation

Question 47

how can talin be activated?

Answer 47

talin can be activated for binding to beta tails by cleavage to release the integrin binding head
talin also can be activated by interaction with phosphoinositol-4,5-bisphosphate (PIP2)