L4 - Cytoskeleton

Question 1

cytoskeleton function

Answer 1

1) framework for cell
2) stability
3) shape change (spreading)
4) cell movement

Question 2

3 types of polymers

Answer 2

1) actin filaments
2) microtubules
3) intermediate filaments

Question 3

actin filament monomer

Answer 3

actin

Question 4

actin filament size

Answer 4

smallest

Question 5

microtubules monomer

Answer 5

heterodimer made of a + B subunits of tubulin

Question 6

intermediate filaments

Answer 6

intermediate filament proteins

Question 7

what is the nuclear lamina beneath the inner nuclear membrane made of?

Answer 7

intermediate filaments

Question 8

what are some times of intermediate filament proteins?

Answer 8

1) keratin

2) vimentin

Question 9

describe mechanical characteristic of intermediate filaments

Answer 9

flexible and rope-like

Question 10

why are intermediate filaments so flexible

Answer 10

staggered long subunits

Question 11

similarities between microtubules and actin filaments

Answer 11

1) single protofilament is thermally unstable

2) two ends polymerize at different rates

Question 12

minus end speed

Answer 12

slow growing

Question 13

plus end speed

Answer 13

fast growing

Question 14

how are microtubules assembled?

Answer 14

GTP hydrolysis (GTP-tubulin dimers = fast growing, GDP-tubulin dimers = fast disassembly)

Question 15

in microtubules, where does disassembly occur?

Answer 15

at plus end

Question 16

how are actin filaments assembled?

Answer 16

ATP hydrolysis

Question 17

what is the rate determining step for actin polymerization?

Answer 17

nucleation (3 actin monomers forming a trimer)

Question 18

F-actin

Answer 18

actin filament

Question 19

G-actin

Answer 19

oligomer (3 actin monomers coming together)

Question 20

critical concentration

Answer 20

minimum concentration of monomers needed for the net addition

Question 21

where is critical concentration higher?

Answer 21

• end

Question 22

where is critical concentration lower?

Answer 22

+ end

Question 23

treadmilling range

Answer 23

range where concentration of monomers between CcT and CcD

Question 24

nucleation

Answer 24

where monomers come together and form an initial stable structure to act as “seed” for polymerization

Question 25

lag phase

Answer 25

time taken for nucleation

Question 26

growth phase

Answer 26

monomers added to exposed ends of growing filament -“ elongation

Question 27

eqm phase

Answer 27

growth of polymer balanced with shrinkage

Question 28

dynamic instability

Answer 28

microtubules - phenomenon where microtubules alternate between a period of slow growth and rapid disassembly at one side

Question 29

actin cytoskeleton function

Answer 29

cell spreading/migration

Question 30

ARP2/3 complex function

Answer 30

adds additional nucleation sites and catalyze the formation of a branched actin network to grow near a cell membrane (stays at - end)

Question 31

formin

Answer 31

nucleates new filaments at + end to accelerate polymerization

Question 32

profilin

Answer 32

binds to subunits and brings to growing chain to speed elongation

Question 33

cofilin

Answer 33

binds and destabilizes disassembly

Question 34

capZ

Answer 34

caps actin filament at + end and prevents growth (greatly increases the critical concentration). only can grow at minus end so much slower

Question 35

tropomyosin

Answer 35

stabilizes actin filament

Question 36

stress fibres actin configuration

Answer 36

contractile bundle (by a-actinin)

Question 37

cell cortex actin configuration

Answer 37

gel-like network (by filamin A)

Question 38

filopodium

Answer 38

tight parallel bundles (by fimbrin)

Question 39

phalloidin

Answer 39

Drug that binds F-actin and stabilizes it (can have fluorescent tag)

Question 40

cytochalasin

Answer 40

drug that caps actin filament plus end

Question 41

swinholide

Answer 41

drug that severs actin filaments

Question 42

latrunculin

Answer 42

drug that binds actin subunits and prevent polymerization

Question 43

taxol

Answer 43

drug that binds and stabilizes microtubules

Question 44

colchicine

Answer 44

drug that binds MT subunits and prevents polymerization

Question 45

colcemid

Answer 45

drug that binds MT subunits and prevents polymerization

Question 46

vinblastine

Answer 46

drug that binds MT subunits and prevents polymerization

Question 47

vincristine

Answer 47

drug that binds MT subunits and prevents polymerization

Question 48

nocodazole

Answer 48

drug that binds MT subunits and prevents polymerization

Question 49

Rho GTPase

Answer 49

catalyze important cell shape

Question 50

cell shapes catalyzed by Rho GTPase

Answer 50

1) filopodia (spike-like proj)
2) lamellipodia (sheet-like proj)
3) stress fibers (contractile actin bundles)

Question 51

RhoA activation

Answer 51

stress fibers (contractile actin bundles) -> more integrin + focal adhesion

Question 52

Cdc42 activation

Answer 52

filopodia (spike-like proj)

Question 53

Rac1 activation

Answer 53

lamellipodia (sheet-like proj)

Question 54

Rac-Rho antagonism

Answer 54

Rac promotes protrusion

Rho promotes contract (opposite so need to be coordinated)

Question 55

how is RhoGTPase deactivation regulated?

Answer 55

GEFs

Question 56

how is RhoGTPase activation regulated?

Answer 56

GAPs

Question 57

what protein is needed for cell-matrix adhesion?

Answer 57

integrin, transmembrane receptors (actin and intermediate filaments)

Question 58

how is integrin activated?

Answer 58

receives signal and catalyze conformation chain where it opens up and allows for strong ligand binding

Question 59

focal adhesion

Answer 59

catalyzed by FAK (involve integrin, actin and actin-binding proteins)