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MSI Unit I > 1-34 Cytoskeleton II - Intermediate Filaments and Microtubules > Flashcards

1-34 Cytoskeleton II - Intermediate Filaments and Microtubules Flashcards

1
Q

intermediate filament polarity?

A

these are non-polar and therefor are not suited to be motility tracks

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2
Q

4 intermediate filament types

A

Keratins - epithelial cells, skin, hair

  1. Vimentin & Related
  2. Neurofilaments
  3. Nuclear lamins
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3
Q

Keratins

A

epithelial cells, hair nails

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4
Q

vimentin

A

desmin - junctions between keratin, strengthening

glial fibrillary acid protein: mesodermal cells

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5
Q

neurofilaments

A

neurons of both CNS and PNS

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6
Q

nuclear lamins

A

present in ALL cell types

associated with innter surface of inner nuclear membrane and with chromatin

assembly regulated by cell cycle (disassembled during mitosis via phos)

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7
Q

Lamin A mutations cause

A

Lamin A mRNA splicing defects - progeria

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8
Q

cancer diagnosis and treatment using intermediate filaments?

A

tissue type of origin can be revealed by the type of IF proteins made

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9
Q

demin mutations can cause

A

muscle weakness, heart disease

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10
Q

keratin mutations can cause

A

skin blister disease

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11
Q

microtubule properties

A

dynamic, not static arrays

structural polarity

tracks for motility

two types of motors (dynein and kinesin) move cargo (organelles or chromosomes) along microtubules

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12
Q

microtubules are _____ assembled from?

A

hollow tubes assembled from dimers of alpha/beta tubulin

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13
Q

assembly of microtubules

A

requires GTP and Mg++ and a critical subunit concentration

beta tubulin in microtubule acts as a slow GTPase, GDP must be exchanged for GTP before a subunit is re-used for assembling another microtubule

end-end binding in tail-tail orientation results in structural polarity with a fast + and slow growing - end

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14
Q

microtubule associated proteins and drugs can….

A

regulate the assembly in vitro and in vivo

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15
Q

microtubule dynamic instability model

A
  1. whenn all GTP hydrolyzed, plus ends disassemble quickly
  2. continued disassembly and assembly allow cell to change microtubule distrubution by selective stabalization of MT + ends
  3. this behavior allows an MT array to search cytoplasm for structures to which MT’s need to attatch to (chromosomes)
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16
Q

MTOCS

help do what?

A

microtubule organizing centers

help determine MT distribution by providing sites for the stabilization of - ends (binding)

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17
Q

in most vertebrate cells, the cell has one main MTOC which consists of..

A

paired centrioles and surrounding material which together makes a centrosome

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18
Q

gamma tubulin

A

alpha/beta tubulin related protein; found in centrosomes and functions to nucleate MT assembly

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19
Q

not all MT arrays are..

A

dynamic. the MT’s that fail to show dynamic stability have undergone “maturation”

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20
Q

what adds to the stability of these stable “mature” MT arrays?

A

post translational modifications of alpha tubulin by acetylation/detyrosination

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21
Q

microtubule associated proteins

A

serve to created specialized MT arrays in different places within cells and tissues and change the surface of the MT’s for interaction with other cellular proteins

can also stabalize MT’s to decrese their probability of disassembling

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22
Q

dyneins

A

Inward Motor

one, two, or three headed ATPases that produce (-) end directed motility

cytoplasmic dyneins are 2 headed

cilia and flagella have 1 and 3 heads

23
Q

Kinesins

A

Outward motor

2 headed atpase that produce + end motility (outward)

24
Q

kinesin and dynein transport vesicles in nerve axons

A

outward transport (like neurotransmitters)

inward transport (like recycled membranes) use dyneins

25
Q

In Cilia, MT do what?

A

push out membrane, like actin meshwork

26
Q

cilia and flagella have…

A

conserved structure in a 9+2

27
Q

cilia and flagella are cylinders of..

they may be?

A

9 doublet microtubules that project from the cell surfce and are surrounded by PM.

motile, sensory, or both.

28
Q

axoneme

A

the doublet MT’s and associated proteins

29
Q

basal body?

A

protein structure found at the base of cilia/flagella that is formed from a centriole and serves as a nucleation site for the growth of axoneme MT’s

30
Q

motile flagella are found on..

A

sperm

31
Q

cilia can be found on…

A

airways, fallopian tubes, brain ventricles

32
Q

embryonic cilia generates..

A

body plane symmetry seen in adult organs such as heart, kidneys, liver

33
Q

wave types of cilia vs flagella

A

cilia - asymmetrical wave

flagella - symmetrical

34
Q

what produces movement of cilia and flagella?

A

MT sliding

regulated sliding results in localized bend formation

waves of dynein activity become waves of bend propogation

Bend propagation-bends in one direction require activity of dyneins between doublet MTs along one side of the flagellum. In order for the flagellum to bend the other direction, the first set of dyneins must be inactive while a second set along the other side of the flagellum is active

35
Q

general structure of intermediate filaments

A

built from long, helical subunits

  • initially forms dimer between subunits
  • molecule has polarity in dimer form, but loses polarity in the tetramer form (not good motility track)
36
Q

microtubule assembly - dynamic instability model in vivo

A

Tubulin binds GTP; only the GTP-bound form assembles.

Beta tubulin in assembled dimers can hydrolyze its GTP to GDP.

If assembly is faster than hydrolysis, the microtubule grows.

If assembly is slower than hydrolysis, the microtubule becomes unstable.

Unstable microtubules shrink rapidly, but may be ‘rescued’ by binding new GTP tubulin dimers at the end, and resume growth.

37
Q

gout treatment?

A

colchicine that blocks microtubule formations

38
Q

cancer treatments?

A

drugs that disrupt tubes in mitotic functions. must be able to assemble and disassemble the MT’s for mitosis

39
Q

vinblastine

A

cancer treatment, blocks MT assembly in mitosis

40
Q

TAXOL

A

stabalizes assembly of MT, disrupts mitosis. no longer “dynamic”

41
Q

centrosome

A

where the (-) ends organize, plus ends radiate out.

1 per cell

42
Q

most interphase cells have a single

A

MTOC

43
Q

tubule maturation

A

some microtubules are stablized by post trasnlational modifications (Acylation of lysine residue) and stop being dynamic.

44
Q

MAPS

A

microtubule may be stabalized by capping proteins or MAPS

45
Q

the microtubules in cilia are

A

stable. not growing and shrinking

46
Q

positioning of the ER and golgi relies on

A

microtubules and motor proteins

  • kinesin stretches the ER from the nucleus out towards the microtubule+ ends
  • dyneine keeps the golgi near the nucleus (-) end
47
Q

PCD, primary ciliary dyskinesia

A

mutation affecting ciliary motility, causes infertility (males), respiratory infections, development of assemetrical defects

48
Q

situs solitus

situs inversus

heterotaxy

A

ss - heart backwards

si - everything backwards

h - everything in the center (problematic)

49
Q

Polycystic Kidney Disease

A

mutation affecting ciliary membrane receptors

-caused by lack of receptors int he membrane on non-motile cilia in kidney tubules

50
Q

non motile cilia are needed for

A

many sensory systems and during limb development. Loss of these cilia results in wide range of symptoms

51
Q

Bardet-Biedl Syndrome

A

sensory cilia defect - obesity, diabetes, hearing loss, retardation, polycystic kidneys, retinal degenertion

52
Q

bacterial flagella nd eurkaryotic flagella are..

A

unrelated

53
Q

motile cilia are

A

cynlinders of microtubules that bend

MSI Unit I (52 decks)

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