04a: Cytoskeleton

Question 1

Roles of cytoskeleton

Answer 1

1. Structural scaffold
2. Cell movement
3. Intracellular traffic
4. Mitosis and meiosis

Question 2

How can targeting cytoskeleton be a method to treat cancer?

Answer 2

1. Cell movement (metastasis)
2. Cell division (proliferation)

Depend on cytoskeleton

Question 3

T/F: cell motility only dependent on actin.

Answer 3

False - MT also play a role

Question 4

Roles of MT:

Answer 4

Mitosis, motility, intracellular transport, secretion, cell shape/polarization

Question 5

Basic MT structure:

Answer 5

Long, hollow cylinder

Question 6

MT polymers are composed of (X) (monomers/dimers/trimers/other).

Answer 6

X = alpha and beta tubulin

Hererodumers

Question 7

There are how many isoforms of alpha and beta tubulin?

Answer 7

3 forms of alpha and 5 forms of beta

Question 8

Which structural component is responsible for the polarity of MT?

Answer 8

The head-to-tail association of the heterodimers

Question 9

(X) nucleate the MT at its (Y) end, and the MT begins to grow.

Answer 9

X = centrosome
Y = minus

Question 10

Which end of MT grows?

Answer 10

Both plus and minus ends grow. But different rates of polymerization.

Question 11

Beta tubulin points to (X) end of MT. Alpha tubulin points to (Y) end.

Answer 11

X = plus (faster-growing)
Y = minus (slower-growing)

Question 12

Gamma-tubulin is important for (MT/actin) formation. What’s its function?

Answer 12

MT; functions as template for correct MT assembly

Question 13

(X) proteins bind to MT for what purpose?

Answer 13

X = capping

Stabilization

Question 14

Capping proteins bind to (alpha/beta) tubulin.

Answer 14

Neither! Gamma-tubulin

Question 15

MT regulation depends on:

Answer 15

1. Proteins

2. Properties (isoforms and post-translational modifications)

Question 16

Taxol function.

Answer 16

Stabilizes MT; drug against a number of cancers

Question 17

Colchicine function.

Answer 17

Binds MT subunits and prevents polymerization

Question 18

Vinblastine function.

Answer 18

Binds ends of MT subunits and prevents polymerization.

Question 19

T/F: taxol, colchicine, and vinblastine are all chemotherapeutics.

Answer 19

False - colchicine used to treat gout and femial Mediterranean fever

Question 20

Intermediate filaments important for:

Answer 20

1. Mechanical integrity

2. Active sequestering, positioning, scaffolds for signal molecules

Question 21

Intermediate filaments are divided into (X) classes, based on:

Answer 21

X = 6

Specific cell type in which filaments are found

Question 22

Acidic keratin intermediate filaments play role in which cell type?

Answer 22

Epithelia

Question 23

Desmin intermediate filaments play role in which cell type?

Answer 23

Muscle

Question 24

Lamin intermediate filaments play role in which cell type?

Answer 24

Cell nuclei

Question 25

Actin filaments, aka (X), are important for:

Answer 25

X = microfilaments 1. Cell shape 2. Locomotion 3. Muscle contraction 4. Cytokinesis 5. Phagocytosis 6. Platelet aggregation

Question 26

What's the structure of actin polymer?

Answer 26

Two-stranded helix of actin monomers

Question 27

What are the types of actin monomers?

Answer 27

Alpha, beta, gamma

Question 28

An actin filament typically contains (X)% alpha monomer, (Y)% beta, (X)% gamma.

Answer 28

Each filament contains only one type of actin

Question 29

Which end of actin grows?

Answer 29

Both! But different rates of polymerization

Question 30

The basic requirements for a cell to move:

Answer 30

1. Change shape 2. Create traction/force 3. Balance attachment and detachment to ECM 4. Move in a direction

Question 31

T/F: all steps required for cell locomotion involve the actin cytoskeleton.

Answer 31

True

Question 32

List the steps of cell locomotion.

Answer 32

1. Protrusion of leading edge 2. Adhesion at leading edge and detachment at trailing edge 3. Movement of cell body

Question 33

Leading edge of cell protrudes in response to (X), such as:

Answer 33

X = Extracellular signal 1. Growth factors 2. AA or formylated peptides 3. Second messengers

Question 34

Detection of signal for cell movement will cause which intracellular event?

Answer 34

Activation of Rho GTPase Rac1 as well as PIP2

Question 35

Action of Rac1/PIP2

Answer 35

Activates WASP family/Scar

Question 36

(WAVE/WASP) is part of the (WAVE/WASP) family.

Answer 36

WAVE; WASP

Question 37

WAVE function.

Answer 37

Activated Arp2/3 complex

Question 38

Arp2/3 complex function

Answer 38

Actin nucleation (new filaments initiated)

Question 39

ADF/cofilin complex function

Answer 39

Severs/depolymerizes ends of existing actin filaments during protrusion of leading edge

Question 40

In protrusion of leading edge, (X) engulfs the severed actin subunits and breaks them down into (Y).

Answer 40

Actin units are bound to profiling and recycled for new filaments

Question 41

During protrusion of leading edge, prevention of further actin extension is done by:

Answer 41

Capping the plus ends by Formin proteins

Question 42

T/F: Actin polymerization generates branched 3D network and pushes membrane forward.

Answer 42

False - 2D network

Question 43

Attachment of leading edge to (X) is possible by:

Answer 43

X = ECM Actin interaction with integrins

Question 44

Detachment of trailing edge is carried out by:

Answer 44

Rho A (a Rho GTPase)

Question 45

(Alpha/beta) integrins interact with actin cytoskeleton.

Answer 45

Both alpha and beta

Question 46

Which key mechanisms allow cell body movement?

Answer 46

1. Actomyosin contraction | 2. Molecular clutching

Question 47

Actomyosin contraction involves which type of myosin.

Answer 47

Non-muscle myosin II

Question 48

Which myosin domain is responsible for movement down (X) filaments?

Answer 48

X = actin Globular head domain

Question 49

In actomyosin contraction, the myosin functions as (monomer/dimer/trimer/other).

Answer 49

Form bipolar filaments, with globular heads on opposite sides.

Question 50

Myosin moves toward (X) end of (Y) during actomyosin contraction

Answer 50

``` X = plus Y = actin filaments ```

Question 51

In locomotion, which part(s) of cell body movement require(s) ATP?

Answer 51

Hydrolysis of 1 ATP required for myosin conformational change that moves protein along actin filaments

Question 52

When molecular clutch (engaged/disengaged), actin cytoskeleton is anchored to (X).

Answer 52

Engaged; | X = ECM

Question 53

Integrins serve which function(s)?

Answer 53

1. Sites of adhesion for actin cytoskeleton | 2. Signaling centers (regulate Rho GTPases)