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Cell and Molecular Biology > Module 6: The Cytoskeleton (Intermediate Filaments and Septins, Cell Polarization and Migration) > Flashcards

Module 6: The Cytoskeleton (Intermediate Filaments and Septins, Cell Polarization and Migration) Flashcards

1
Q
  • forms cytoplasmic filaments.
  • have cells that are subject to mechanical stress.
  • not found in animals with rigid exoskeletons
A

intermediate filaments

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2
Q

Types of intermediate filament (4)

A
  • Nuclear
  • Vimentin-like
  • Epithelial
  • Axonal
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3
Q
  • The central domain of elongated proteins in intermediate filaments is a conserved __ containing 40 or so __ that forms an extended coiled-coil structure.
  • a pair of __ then associates in an antiparallel fashion to form a __.

intermediate filament construction

A
  • α-helical domain
  • heptad repeat motifs
  • parallel dimers
  • staggered tetramer
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4
Q

Do intermediate filaments contain a binding site for nucleotides?

A

No

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5
Q

Are the two ends of an intermediate filament the same or different?

A

Same

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6
Q

They pack together laterally to form the filament, which includes eight parallel protofilaments made up of tetramers.

intermediate filament construction

A

tetramers

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7
Q

How many individual α-helical coils are present in a cross-section of the filament?

intermediate filaments

A

32

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8
Q

The mechanical properties of intermediate filaments: They have a __ character, are easily __, but are extremely difficult to __and can be __.

intermediate filaments

A
  • ropelike
  • bent
  • break
  • stretched
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9
Q

Which is the most diverse intermediate filament family?

A

Keratins

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10
Q

Made up of equal mixture of type I (acidic) and type II (neutral/basic) keratin proteins, forming a heterodimer.

intermediate filaments

A

Keratin filament

each

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11
Q
  • What holds cross-linked keratin networks together?
  • What happens to cross-linked keratin networks after cell death?

intermediate filaments

A
  • Disulfide bonds
  • Survive
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12
Q

Keratins are used in the diagnosis of __(__).

intermediate filaments

A

epithelial cancers (carcinomas)

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13
Q

A single epithelial cell produces __ types of keratins, they __ into a __ network.

intermediate filaments

A
  • multiple
  • copolymerize
  • single
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14
Q

What structure is involved in cell-cell contact?

intermediate filaments

A

desmosomes

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15
Q

What structure is involved in cell-matrix contact?

intermediate filaments

A

Hemidesmosomes

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16
Q
  • defective keratins in the basal cell layer of the epidermis.
  • causes skin blisters in response to even very slight mechanical stress, which ruptures the basal cells.
  • mouth, esophageal lining, and cornea of the eye can be affected
  • Cell rupture as a consequence of mechanical trauma and a disorganization or clumping of the keratin filament cytoskeleton.

intermediate filaments; a condition

A

epidermolysis bullosa complex

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17
Q
  • found in high concentrations along axons
  • have subunits NF-L, NF-M, and NF-H, assemble in vivo into heteropolymers.

intermediate filaments

A

neurofilament

in vivo-performed or taking place in a living organism.

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18
Q
  • During axonal growth, new neurofilament subunits are incorporated all along the axon in a dynamic process that involves the __ of subunits along the filament length as well as the ends.
  • The level of __ controls axonal diameter during axonal growth.
A
  • addition
  • neurofilament gene expression
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19
Q

What disease is associated with neurofilaments?

A

Amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease)

sclerosis- areas of scar-like tissue (also called plaques or lesions)

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20
Q
  • A vimentin-like filaments expressed in skeletal, cardiac, and smooth muscle, where it forms a scaffold around the Z disc of the sarcomere.
  • It stabilizes muscle fibers.

intermediate filaments

A

desmin

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21
Q

They exhibit muscle-cell abnormalities such as misaligned muscle fibers. They lack desmin.

intermediate filaments; what animal?

A

mice

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22
Q

What human conditions are associated with defective desmin? (2)

A
  • Muscular dystrophy
  • cardiac myopathy

MD- progressive weakness and degeneration of skeletal muscles

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23
Q

Scaffold proteins that control myriad cellular processes including, transcription, chromatin organization, and signal transduction.

intermediate filaments

A

A-type lamins

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24
Q

Tissue-specific diseases associated with mutant versions of lamin A.

A

laminopathies

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25
Q
  • intermediate filament network linked to the rest of the cytoskeleton
  • members of a family of proteins
  • They are large and modular, containing multiple domains that connect cytoskeletal filaments to each other and to junctional complexes.
A

Plakins

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26
Q

Interacts with protein complexes that connect the cytoskeleton to the nuclear interior.

intermediate filaments

A

Plectin

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27
Q
  • an additional filament system that forms ring and cagelike structures.
  • act as scaffolds to compartmentalize membranes into distinct domains.
  • recruit and organize the actin and microtubule cytoskeleton.
A

Septins

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28
Q
  • form a neck between a dividing yeast mother cell and its growing bud.
  • recruit the actin-myosin machinery necessary for cytokinesis.
  • involved in cell division, migration, vesicle trafficking, and act as a diffusion barrier.
A

Septins

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29
Q

How many septin genes are present in humans?

A

13

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30
Q
  • relies on the coordinated deployment of components and processes.
  • involves the dynamic assembly and disassembly of cytoskeletal polymers.
  • structure of cytoskeletal polymers is through regulation and modification of their structure.
  • action of motor proteins moving along cytoskeletal polymers or exert tension against them.
A

cell migration

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31
Q

How do cells move? Which cells do this to search for food? Which cell is an exception? (3)

cell migration

A
  • by crawling
  • Amoebae
  • Sperm

unicellular, can alter its shape( extending and retracting pseudopods)

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32
Q

Structure of an animal is created through the __ of individual cells to specific target locations.

A

migrations

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33
Q

Which cells crawl during nervous system construction?

A

Neural crest cells

34
Q

Which cells crawl to sites of infection to engulf foreign invaders? (2)

A
  • macrophages
  • neutrophil
35
Q

Which cells crawl for bone remodeling and renewal?

A

Osteoclasts

36
Q

Which cells migrate through connective tissues?

A

Fibroblasts

37
Q

What is a pathological example of cell crawling?

A

Cancer cells

38
Q

Steps in cellular migration (3)

A
  1. protrusion
  2. attachment
  3. traction
39
Q

The plasma membrane is pushed out at the front of the cell.

a step in cell migration

A

protrusion

Protrude - to stick out

40
Q

The actin cytoskeleton connects across the plasma membrane to the substratum.

a step in cell migration

A

attachment

41
Q

The bulk of the trailing cytoplasm is drawn forward.

a step in cell migration

A

traction

pulling something over a surface

42
Q

What generates the forces required for protrusion?

cell migration

A

actin polymerization

43
Q

What do protrusive structures contain?

cell migration

A

Dense cores of filamentous actin

44
Q

Give 5 protrusive structures/protrusions (5)

cell migration

A
  • filopodia
  • lamellipodia
  • invadopodia
  • podosomes
  • blebbing
45
Q

One-dimensional protrusions formed by migrating growth cones of neurons and some types of fibroblast, containing a core of long, bundled actin filaments.

46
Q

Two-dimensional sheetlike structures formed by epithelial cells and fibroblasts, containing a cross-linked mesh of actin filaments.

A

lamellipodia

47
Q

Three-dimensional actin-rich protrusions important for cells to cross tissue barriers. (2)

A
  • invadopodia
  • podosomes
48
Q

A protrusion that depends on hydrostatic pressure within the cell, generated by the contraction of actin and myosin.

49
Q
  • Epithelial cells of the epidermis in fish and frogs that are rich in keratin filaments.
  • They function form an epithelial sheet that covers the animal and specialize in closing wounds.
  • It has a large lamellipodium and a small trailing cell body that is not attached to the substratum.
A

keratocyte

50
Q

While the lamellipodia crawl forward, the __ remain stationary with respect to the __.

A
  • actin filaments
  • substratum
51
Q

Orientation of actin filaments in the lamellipodia: The __ ends face forward, and the __ ends are attached to the sides of other actin filaments by __.

A
  • plus
  • minus
  • Arp2/3 complexes
52
Q

The two-dimensional actin web in lamellipodia is formed by cross-linking __ through __.

A
  • actin filaments
  • Arp2/3 complexes
53
Q

refers to the process where actin filaments assemble at the front of the lamellipodium and disassemble at the back, maintaining dynamic turnover.

Actin Filament Dynamics in Lamellipodia

A

Treadmilling

54
Q
  • Where is actin filament nucleation localized in lamellipodia?
  • Where does filament depolymerization occur in lamellipodia?
A
  • At the leading edge
  • behind the leading edge
55
Q
  • binds preferentially to actin filaments containing ADP-actin.
  • New T-form filaments are resistant to depolymerization because this efficiently disassembles older filaments but does not act on the new T-form filaments at the leading edge.
  • maintains actin turnover in lamellipodia.

Actin Filament Dynamics in Lamellipodia

56
Q
  • For the leading edge of a migrating cell to advance, __ of the membrane must be followed by __ to the __ at the front.
  • For the cell body to follow, __ must be coupled with de-adhesion at the rear of the cell.

Actin Filament Dynamics in Lamellipodia

A
  • protrusion
  • adhesion
  • substratum
  • contraction
57
Q

What mediates the connection between the actin cytoskeleton and the substratum?

Actin Filament Dynamics in Lamellipodia

A

Integrin-mediated adhesions.

58
Q

Dynamic assemblies of structural and signaling proteins that connect the actin cytoskeleton to the substratum.

Actin Filament Dynamics in Lamellipodia

A

focal adhesions

59
Q

Forms bipolar filaments that associate with actin filaments at the rear of the lamellipodium, pulling them into a new orientation.

Cell migration

60
Q

Which cytoskeletal processes are essential for cell migration? (3)

A
  • Actin polymerization
  • dynamic adhesions
  • myosin contraction
61
Q

Disengaged interaction between actin network and focal adhesions, polymerization pressure at the leading edge, and myosin-dependent contraction cause the actin network to slip back.

A

Retrograde flow

62
Q

The front end of the cell remains structurally and functionally distinct from the back end.

A

Cell migration

63
Q

What is required for oriented cell divisions in tissues and for the formation of a coherent, organized multicellular structure?

cell migration

A

Cell polarization processes

64
Q

Cytoskeletal coordination manifests during cell migration through the establishment of __.

A

cell polarity

65
Q

Establishment of cell polarity depends on the local regulation of the __ by __ signals.

A
  • actin cytoskeleton
  • external
66
Q

Which monomeric GTPases are members of the Rho protein family? (3)

A
  • Cdc42
  • Rac
  • Rho
67
Q

involved in bundling actin filaments with myosin II filaments into stress fibers and clustering integrins and associated proteins to form focal adhesions.

actin cytoskeleton regulation

68
Q

Promotes actin polymerization and bundling to form filopodia at the plasma membrane.

actin structure; actin cytoskeleton regulation

69
Q

Actin polymerization at the cell periphery and the formation of sheetlike lamellipodial extensions.

actin dynamics; actin cytoskeleton regulation; what facilitates these?

70
Q

What proteins are activated by Cdc42 and are associated with the Wiskott-Aldrich Syndrome?

A

WASp proteins

71
Q

A severe form of immunodeficiency in which immune system cells have abnormal actin-based motility and platelets do not form normally.

A

Wiskott-Aldrich Syndrome

72
Q
  • activates WASp family members
  • activates the cross-linking activity of the gel-forming protein filamin
  • It inhibits the contractile activity of myosin II.
  • It stabilizes lamellipodia and inhibits the formation of contractile stress fibers.
73
Q
  • turns on formin proteins to construct parallel actin bundles
  • activates a protein kinase that in indirectly inhibits the activity of cofilin, leading to actin filament stabilization
  • inhibits a phosphatase acting on myosin light chains
74
Q

What does Rho-GTP activate to construct parallel actin bundles?

A

Formin proteins

75
Q

The movement of a cell toward or away from a source of some diffusible chemical.

A

chemotaxis

76
Q

How do cells set up large-scale cell polarity in chemotaxis?

what molecule is used? Throug…

A

Through Rho family proteins

77
Q

Which cells are known to move toward a source of bacterial infection?

A

Neutrophils

78
Q

Neutrophils ability to detect very low concentrations of __ derived from __ enables them to detect bacterial infections.

A
  • N-formylated peptides
  • bacterial proteins
79
Q

When a chemoattractant binds to its __, it activates __, leading to the production of [PI(3,4,5)P3], which activates __ and subsequently __, resulting in __.

Neutrophil polarization and chemotaxis

A
  • GPCR
  • PI3Ks
  • Rac GTPase
  • Arp 2/3
  • lamellipodial protrusion
80
Q

Binding of a chemoattractant activates __, which enhances myosin-based contractility

Neutrophil polarization and chemotaxis

81
Q

Rac and Rho activation directly inhibit each other, such that Rac activation dominates in the __ of the cell and Rho activation dominates in the __.

A
  • front
  • rear
82
Q

What is the result of the interactions between Rac and Rho activation?

A

Functional polarity in the cell

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