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Cytoskeleton II Flashcards

1
Q

Cellular movement/migration, intracellular transport, and ciliar and flagellar beating are all dependent on the

A

Cytoskeleton

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2
Q

Involved in spindle assembly, chromosome alignment, and segregation in mitosis

A

Kinesins and dynein

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3
Q

Cleave the cell in the contractile ring during mitosis

A

Actin and myosin II

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4
Q

The driver of morphogenesis

A

Cytoskeleton

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5
Q

The folding of the epithelial sheet is driven by myosin II-dependent contraction of the

A

Adhesion belt

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6
Q

The transport of vesicles between cellular compartment and to the cell periphery requires

A

Cytoskeleton

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7
Q

Molecular motors carry cargo on

A

Microtubules and actin filaments

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8
Q

Intracellular transport involves which cytoskeletal elements?

A

Actin filaments and microtubules

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9
Q

In the intracellular transport on actin filaments and microtubule, the traffic goes

A

Both ways

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10
Q

What are the three classes of cytoskeletal motors?

A
  1. ) Myosins
  2. ) Dyneins
  3. ) Kinesins
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11
Q

Move along actin filaments

A

Myosins

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12
Q

Move along microtubules

A

Dyneins and kinesins

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13
Q

ATPases that have multiple isoforms encoded by multiple genes

A

Myosins, dyneins, and kinesins

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14
Q

Have related structures and mechanisms, but different functions

A

Kinesins and Myosins

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15
Q

A particular isoform (type) of myosin, dynein, and kinesin on an actin filament or microtubule moves in

A

One direction

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16
Q

Vesicles/organelles can move on microtubules and actin filaments and have more than one kind of

A

Motor

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17
Q

The downstream targets of cellular signaling cascades

A

Molecular motors

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18
Q

Myosins, Dyneins, and Kinesins are all classified as

A

Mechanochemical enzymes

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19
Q

Work by generating tension or movement of an object along a filament or microtubule

-ex: muscle contraction, chromosome segregation, vesicle movement

A

Myosins, Dyneins, and Kinesins

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20
Q

Myosin has a large gene family. The enzyme is made up of

A

Two heavy chains and two light chains

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21
Q

Most myosins move towards the

A

(+) end of actin (“plus-end directed)

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22
Q

The globular head, or motor domain, of myosin contains the

A

ATPase

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23
Q

Variable domain of myosin. Contains coiled coil for dimerization, and/or binds to membrane or target vesicle

A

Tail domain

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24
Q

The myosin superfamily shows homologous motor domains, but variable

A

Tail domains

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25
Q

The classification of a myosin protein is based on its

A

Motor domain

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26
Q

Each member of the myosin super family has specific cellular

A

Localizations and functions

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27
Q

Mutations in myosin family cause inherited human diseases such as

A

Myopathies, deafness, blindness, etc

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28
Q

Myosin has many roles including

A
  1. ) cytokinesis
  2. ) intracellular transport
  3. ) endocytosis
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29
Q

First isolated as the motor responsible for anterograde axonal transport

  • Smaller than myosin
  • mutations cause human inherited diseases
A

Kinesin

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30
Q

Like the myosins, most kinesis are what type of movers?

A

(+)-end directed

-some are (-)-end

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31
Q

The head domain of kinesins,which contains the ATPase, is structurally related to

A

Myosin and G proteins

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32
Q

Located in the heavy chain and contains the ATPase and microtubule binding site

-conserved across kinesin family

A

Motor domain (“head”)

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33
Q

Which type of kinesin motor is (+)-end directed?

A

N-terminal motor

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34
Q

Which type of kinesin motor is (-)-end directed?

A

C-terminal motor

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35
Q

Located next to the motor region and determines the polarity of the kinesin

A

Kinesin Neck region

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36
Q

Allows for dimerization when it is a coiled coil

A

Kinesin Stalk region

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37
Q

Binds to the target, variable across kinesin family, and binds light chains

A

Kinesin Tail region

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38
Q

A minus-end directed motor

-an ATPase

A

Dynein

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39
Q

Dynein is a very large protein. It weighs approximately

A

2 Million daltons

40
Q

Dynein is an AAA protein, meaning it is

A

ATPase associated w/ diverse cellular activity

41
Q

Dynein typically contains 6 domains. The energy of hydrolysis leads to a conformational change which leads to

42
Q

Dynein is found in

-necessary for beating

A

Ciliary/flagellar arms

43
Q

The cytoplasmic forms of dynenin function in

A

retrograde axonal transport

44
Q

Functions during mitosis and in the transport of mRNA, vesicles, organelles, and viruses

45
Q

The tail of dynein binds cargo or to another

A

Microtubule

46
Q

What is an example of a dynein associated disease?

A

Primary Ciliary Dyskinesia (PCD)

-i.e. kartakener syndrome

47
Q

Characterized by respiratory tract infections and male infertility

A

Primary Ciliary Dyskinesia (PCD)

48
Q

In PCD, there is a mutation in the outer arm ciliary dynein heavy chain. This results in

A

Immobile cilia

49
Q

PCD is associated with

A

Situs inversus

50
Q

All function by converting the energy of hydrolysis of ATP into mechanical work

A

Cytoskeletal motors

51
Q

Causes a conformational change in the cytoskeletal motor

A

Binding and/or hydrolysis of ATP

52
Q

The rate-limiting step for cytoskeletal motors is

A

Product release following hydrolysis

53
Q

Accelerates the rate limiting step

A

Binding actin or microtubule

54
Q

You can think of the actin filament/microtubule as a

A

Nucleotide exchange factor (NEF)

55
Q

Differ in processivity and the fraction of the kinetic cycle they spend attached to microtubules or actin

A

Kinesin and Myosin

56
Q

Filament forming myosin

57
Q

Results in attachment of myosin II to actin and causes rigor mortis in mucle

A

Depletion of ATP

58
Q

The binding of ATP thus causes the

A

Release of Myosin II from actin

59
Q

In the myosin II reaction, the rate limiting step is

-accelerated by actin binding

A

Pi release

60
Q

Operates by an analogous mechanism to myosin

61
Q

The binding of ATP weakens the affinity of kinesin for

A

Microtubules

62
Q

After ATP hydrolysis, Kinesin binds microtubules with a

A

Higher affinity

63
Q

Binding to microtubules following ATP hydrolysis accelerates product release and conversion from

A

Weak to strong binding (power stroke)

64
Q

For myosin and kinesin, when ATP is bound we see which stroke?

A

Recovery stroke

65
Q

For myosin and Kinesin, when ATP is hydrolyzed, we see tighter binding to actin/microtubules and which stroke?

A

Power stroke

66
Q

In dynein, the microtubule binding site is remote from the

A

ATPase domain

67
Q

When nexin is present between two microtubules, they can not slide. The force generated by dynein movement then causes the cilium to

68
Q

A given motor moves in only

A

One direction

69
Q

Motor-cargo relationships are highly

70
Q

Single headed myosins: the tail can bind to the plasma membrane, and in microvilli, the actin filaments oriented so the (+)-end is pointed to the tip of the microvillus

71
Q

Form bipolar filaments as in: muscle, contractile ring of cytokinesis, stress fibers, and adhesion belts

72
Q

Allows for contraction, as in sliding filaments

73
Q

Carries cargos such as ER, vesicles, proteins, and nucleic acids, on its tail and walks towards the (+) end of the actin filament

74
Q

Designed for long range transport: processive, longer steps than other myosins

75
Q

Bipolar myosin filaments are involved in

A

Contractile functions

76
Q

For vesicles to reach the end of the growth cone or cell periphery they must travel from the cell body to the periphery, i.e. they must

A

Transfer from microtubules to actin filaments

77
Q

Which three motors are involved in vesicle transport?

A

Dynein, kinesin, and myosin V

78
Q

Defines the cell’s polarity and organization

A

Transport of vesicles

79
Q

Are transported from the ER to the cell periphery and back

-Can travel in both directions on a microtubule (motor-dependent)

A

Vesicles/organelles

-also proteins and nucleic acids

80
Q

Can occur on + end of a microtubule via a + tip protein, as a microtubule grows

A

Vesicle/organelle transport

81
Q

Can have more than one molecular motor on its surface

-can travel on both microtubules and actin filaments

A

Vesicle/organelle

82
Q

The model system for transport is the transport of

A

Pigment granules in skin

83
Q

Pigment is in vesicles called

A

Melanosomes

84
Q

Develop from neural crest cells, as do many neurons

A

Melanocytes

85
Q

They are transported on microtubules and actin filaments to the periphery of the cell where they are
taken up by keratinocytes.

-Myosin V is required for transport to the periphery

A

Melanosomes

86
Q

Normal melanosome distribution in the skin requires

87
Q

Binding of cargo causes a transition into it’s active conformation

-without cargo it exists in an inactive folded conformation

88
Q

Transports melanosomes and synaptic vesicles to the cell’s periphery

89
Q

Target myosins to specific intracellular membranes

A

Rab GTPases

90
Q

The motor domain of myosin Va moves along actin carrying the melanosomes to the periphery of the

A

Melanocyte

91
Q

The myosin V tail binds to its cargo by way of

A

Melanophilin (Mlph) and Rab27aGTP

92
Q

Mice null for Rab27a, melanophilin (Mlph) or
myosin Va results in clustering of melanosomes
around the

93
Q

In humans, mutations in myosin Va, melanophilin, or Rab27a cause

  • results in melanosomes remaining in the basal level of the epithelium
  • causes silvery hair and light skin in children of dark-skinned parents
A

Griscelli type 1 and Elejalde synromes

94
Q

Recent work on melanocytes shows that melanophilin not only links myosin Va to melanosomes, but that it also
regulates

95
Q

Involved in recruitment of vesicles carrying receptors into dendritic spines is associated with long term potentiation, synaptic changes that are believed to be
associated with learning and memory.

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