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Cells to Tissues > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

1
Q

What holds filaments together?

A

Weak non-covalent interactions

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2
Q

What shape do filaments usually have?

A

Helices joined together laterally.

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3
Q

What are 3 major roles of microtubules?

A
  1. Organelle transport (tracks)
  2. Cilia and flagella
  3. Cell division
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4
Q

Describe the microtubule structure.

A

2 tubulin subunits: alpha and beta forma hetrodime

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5
Q

How do microtubules grow?

A

MTOC nucleate the growth at the minus end with the plus end growing away from it. Facilitated by MAPS (e.g. Tau).

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6
Q

What drugs affect microtubule function?

A

KN_ [Taxol (binds and occupies)
Colchicine (prevents polymerization)
Vinblastine (prevents polymerization)

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7
Q

What roles do actin play?

A
  1. Cell shape
  2. Cell locomotion
  3. Cytokinesis
  4. Phagocytosis
  5. Platelet aggregation
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8
Q

What are the 6 classes of intermediate filaments?

A
  1. Lamins
  2. Keratins
  3. Neurofilaments
  4. Vimentins
  5. GFAP (glia)
  6. Desmin
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9
Q

What are the 3 steps of cell movement?

A
  1. Protrusion of the leading edge
  2. Adhesion of the leading edge/deadhesion of trailing edge
  3. Movement of the cell body
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10
Q

What structure operates at the protruding edge of actin cytoskeletons?

A

Lamellipodia, thin sheet-like projections that pull cells through tissues.

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11
Q

What is behind the lamellipodia?

A

A more stable region of lamella which couples the actin network to myosin II-mediated contractility substrates (e.g. ECM of another cell)

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12
Q

What severs the ends of existing actin filaments in response to growth factors or other signals?

A

Cofilin

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13
Q

Describe the activation of actin nucleation.

A

Rac1, a Rho GTPase, is activated/PIP2 -> activates WAVE complex (a type of WASP -> Wave complex uses molecules Arp2/3 to generate a branched actin network.

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14
Q

What protects the + end of actin filaments?

A

Formin family proteins

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15
Q

What are integrins composed of?

A

Heterodimers: alpha and ebta subunits

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16
Q

What are the adhesion sites composed of?

A

Fibronectin in the ECM binds the extracellular portions of integrins. These points serve as traction points for contractile forces.

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17
Q

What do adhesion points do (other than adhere)?

A

Regulate Rho GTPases to control polymerization and organization of actin!

18
Q

How does the trailing edge detach?

A
  1. Rho A, a Rho GTPase, inhibits Rac1 to prevent lamellipodia formation and actomyosin contractility.
  2. Microtubule-induced adhesion disassembly.
  3. Integrin endocytosis
  4. proteolytic cleavage of linker proteins.
19
Q

How does the cell body move?

A

Molecular clutching, a process that integrates adhesion, retrograde flow, and actin polymerization.

20
Q

What is non-muscle myosin II (NMII)?

A

A motor protein/ATPase that moves along actin filaments towards the PLUS end (actin filaments provide the track, myosin motor, and AT the energy). This is retrograde flow(??)

21
Q

Describe the structure of NMII.

A

Globular head (binds actin and ATP)

Light chain linkers (ELC + RLC)

Helical heavy chain

22
Q

What happens when the molecular clutch is disengaged?

A

Actin is not anchored to the substratum and actin polymerization is counterbalanced by retrograde flow: no movement!

23
Q

What happens when the molecular clutch is engaged?

A

Actin is coupled to ECM and retrograde flow is impeded b the ECM. New actin polymerization exceeds retrograde flow and the cell moves forward.

24
Q

The ____ chain of the microtubule is the fastest growing.

A

Beta

25
Q

Can both ends of a microtubule both grow and depolymerize?

A

Yes

26
Q

In microtubules, the ____ end grows fastest.

A

+

27
Q

What is the function of gamma tubulin?

A

Functions as a template for the correct assembly of microtubules

28
Q

What stabilizes the end of of microtubules?

A

Capping proteins

29
Q

What are MAPS

A

Microtubuels-associated proteins can stabilize/destabilize/regulate, etc.

30
Q

What does taxol do?

A

Stabilize microtubules. Used to treat breast cancer, lung cancer, ovarian cancer, Kaposi’s sarcoma.

31
Q

What drugs prevent microtubule polymerization?

A

Colchicine and Vinblastine

32
Q

What does Colchicine treat?

A

Gout

Familial Mediterranean Fever

33
Q

What does Vinblastine treat?

A

Testicular and breast caners
Lymphomas
Kaposi’s sarcoma

34
Q

What is the final intermediate filament assembly?

A

Eight tetramers twisted into a rope-like structure.

35
Q

What are the 3 types of actin monomer subunits?

A

Alpha
Beta
Gamma

36
Q

One actin subunit is made of ____ type of actin.

A

One

37
Q

One strand of actin is amde of ____ actin subunits.

A

2

38
Q

What types of messengers cause actin filaments to reorganize and move?

A

Growth factors (e.g. PDGF, EGF, VEGF)
Amino acids
Second messengers (e.g. Ca2+)
Formylated peptides

39
Q

Detachment of the lagging edge is regulated by ____.

A

Rho A (also a GTPase)

40
Q

Each step of NMII corresponds with hydrolysis of how many ATP?

A

One

41
Q

What are the 4 steps of movement in actin-myosin contraction?

A
  1. Actin cytoskeleton coupled to the ECM by interaction of actin-binding proteins with integrins.
  2. Actin polymerization at front of cell pushes out membrane: leading edge
  3. Actomyosin contraction pulls the rear of the cell forward.
  4. The cell moves

Cells to Tissues (23 decks)

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