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histology (E1 Woods) > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

1
Q

what 3 kinds of protein structures is the cytoskeleton made up of

A

microfilaments (actin)
intermediate filaments
microtubules

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2
Q

what does highly conserved mean

A

the chemical/molecular structure is very similar among a wide range of different organisms

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3
Q

what are the filaments of actin microfilaments organized into

A

bundles and 3D networks

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4
Q

what doe actin microfilaments bind to and how

A

bind to specific transmembrane proteins either directly or indirectly

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5
Q

how do actin microfilaments exists as

A

monomers (G-actin) and long chains (F-actin)

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6
Q

what are the 3 major varieties of actin filaments

A

alpha-actin (found in muscle tissue)
beta-actin (non muscle actin)
gamma-actin (non muscle actin)

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7
Q

what is the first step of actin polymerization

A

nucleation

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8
Q

what occurs during nucleation during actin polymerization

A

a trimer is formed

addition actin monomers can then be added to either end

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9
Q

what happens following polymerization of microfilaments

A

ATP-actin associates with the growing (plus or barbed) ends, and the ATP is hydrolyzed to ADP following polymerization

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10
Q

which end of microfilaments is the slower growing end

A

minus end (pointed or depolymerization end)

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11
Q

what doe very low concentrations of F actin favor

A

disassembly of actin filaments

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12
Q

what do intermediate concentrations of G actin favor

A

dynamic equilibrium between the minus end and the plus end (tread milling)

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13
Q

what do high concentrations of G actin favor

A

net addition at both ends and therefore growth of the actin filament

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14
Q

what does cytochalasins do

A

drug that affects actin polymerization:

binds to barbed ends, blocks elongation, can inhibit movement

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15
Q

what does phalloidin do

A

drug that affects actin polymerization
binds to actin filaments and prevents dissociation
can be labeled with fluorescent dyes to allow visualization of actin filaments

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16
Q

what are the actin binding proteins & what do they do

A
  • spectrin: (found in RBC) binds cortical cytoskeleton to the plasma membrane
  • dystrophin: binds cortical cytoskeleton to the plasma membrane
  • villin and fimbrin: cross-links in microvilli
  • calmodulin and myosin I: cross-links actin to plasma membrane in microvilli
  • alpha-actinin: cross-links stress fibers and connects actin to protein-plasma membrane complex complexes
  • filamin: cross-links actin at wide angles to form screen-like gels
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17
Q

what are the actin-binding molecules that control treadmilling

A
  • thymosin: captures actin monomers and prevents actin monomers from being polymerized
  • profilin: binds to actin monomers and prevents monomers form being polymerized, facilities exchange of bound ADP for ATP-favors polymerization
  • gelsolin: destabilizes F-actin and caps actin filaments (preventing loss and addition of G-actin)
  • cofilin: triggers depolymerization of ADP-bound actin at the minus end
  • Arp2/3: initiates growth of F actin from sides of existing filaments-causes branching
  • phalloidin: prevents depolymerization by binding to actin filaments
  • latrunculins: binds to G-actin and induces F-actin depolymerization
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18
Q

what does spectrin do?

A

(found in RBC) binds cortical cytoskeleton to the plasma membrane

19
Q

what does dystrophin do

A

binds cortical cytoskeleton to the plasma membrane

20
Q

what does villain and fimbrin do

A

cross-links in microvilli

21
Q

what does calmodulin and myosin I do

A

cross-links actin to plasma membrane in microvilli

22
Q

what does alpha-actinin do

A

cross-links stress fibers and connects actin to protein-plasma membrane complex complexes

23
Q

what does filamin do

A

cross-links actin at wide angles to form screen-like gels

24
Q

what does thymosin do?

A

(tread milling)captures actin monomers and prevents actin monomers from being polymerized

25
Q

what does profiling do

A

(tread milling) binds to actin monomers and prevents monomers form being polymerized, facilities exchange of bound ADP for ATP-favors polymerization

26
Q

what does gelsolin do

A

(tread milling)destabilizes F-actin and caps actin filaments (preventing loss and addition of G-actin)

27
Q

what do cofilin do

A

(tread milling)triggers depolymerization of ADP-bound actin at the minus end

28
Q

what does Arp2/3 do

A

(tread milling)initiates growth of F actin from sides of existing filaments-causes branching

29
Q

what does phalloidin do

A

(treadmilling) prevents depolymerization by binding to actin filaments

30
Q

what does latrunculins do

A

(treadmilling) binds to G-actin and induces F-actin depolymerization

31
Q

what are characteristics of intermediate filaments

A
  • abundant cells subject to mechanical stress
  • provide tensile strength in cells
  • strengthen epithelial cells (as desmosomes and hemidesmosomes)
32
Q

how do tetramers assemble in intermediate filaments

A

end to end to form protofilaments

33
Q

what are some intermediate filament functions

A
  • form a cytoplasmic network in most cells

* associate with other cytoskeletal elements to form a scaffolding that organizes the internal structure of the cell

34
Q

what is a type I intermediate filament

A

acidic keratins

35
Q

what is an example of a type 2 intermediate filament

A

neutral to basic keratins

36
Q

what are examples of type 3 intermediate filaments

A

vimentin, desmin, glial fibrillary acidic protein, peripherin

37
Q

what is an example of type 4 intermediate filament

A

neurofilaments

38
Q

what is an example of a type 5 intermediate filament

A

nuclear lamins

39
Q

what is an example of a type 6 intermediate filament

A

nestin

40
Q

what happens following polymerization in mircotubules

A

GTP is hydrolyzed to GDP and the tubulin is less stable * dimers at the minus end dissociate

41
Q

what are some factors that inhibit microtubule polymerization

A

colchicines, colcemid, vincristine, vinblastin

42
Q

what factor stabilizes microtubules

A

taxol (often used to treat breast cancer)

43
Q

what are the functions of the cytoskeleton

A
  • cell movement
  • support and strength for the cell
  • phagocytosis
  • mitotic spindle formation
  • cytokinesis
  • cell-to-cell and cell-to-Extracellular Matrix adherence
  • changes in cell shape

histology (E1 Woods) (22 decks)

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