1-34 Cytoskeleton II - Intermediate Filaments and Microtubules

Question 1

intermediate filament polarity?

Answer 1

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

Question 2

4 intermediate filament types

Answer 2

Keratins - epithelial cells, skin, hair

2. Vimentin & Related
3. Neurofilaments
4. Nuclear lamins

Question 3

Keratins

Answer 3

epithelial cells, hair nails

Question 4

vimentin

Answer 4

desmin - junctions between keratin, strengthening

glial fibrillary acid protein: mesodermal cells

Question 5

neurofilaments

Answer 5

neurons of both CNS and PNS

Question 6

nuclear lamins

Answer 6

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)

Question 7

Lamin A mutations cause

Answer 7

Lamin A mRNA splicing defects - progeria

Question 8

cancer diagnosis and treatment using intermediate filaments?

Answer 8

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

Question 9

demin mutations can cause

Answer 9

muscle weakness, heart disease

Question 10

keratin mutations can cause

Answer 10

skin blister disease

Question 11

microtubule properties

Answer 11

dynamic, not static arrays

structural polarity

tracks for motility

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

Question 12

microtubules are _____ assembled from?

Answer 12

hollow tubes assembled from dimers of alpha/beta tubulin

Question 13

assembly of microtubules

Answer 13

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

Question 14

microtubule associated proteins and drugs can….

Answer 14

regulate the assembly in vitro and in vivo

Question 15

microtubule dynamic instability model

Answer 15

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)

Question 16

MTOCS

help do what?

Answer 16

microtubule organizing centers

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

Question 17

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

Answer 17

paired centrioles and surrounding material which together makes a centrosome

Question 18

gamma tubulin

Answer 18

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

Question 19

not all MT arrays are..

Answer 19

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

Question 20

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

Answer 20

post translational modifications of alpha tubulin by acetylation/detyrosination

Question 21

microtubule associated proteins

Answer 21

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

Question 22

dyneins

Answer 22

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

Question 23

Kinesins

Answer 23

Outward motor

2 headed atpase that produce + end motility (outward)

Question 24

kinesin and dynein transport vesicles in nerve axons

Answer 24

outward transport (like neurotransmitters)

inward transport (like recycled membranes) use dyneins

Question 25

In Cilia, MT do what?

Answer 25

push out membrane, like actin meshwork

Question 26

cilia and flagella have...

Answer 26

conserved structure in a 9+2

Question 27

cilia and flagella are cylinders of.. they may be?

Answer 27

9 doublet microtubules that project from the cell surfce and are surrounded by PM. motile, sensory, or both.

Question 28

axoneme

Answer 28

the doublet MT's and associated proteins

Question 29

basal body?

Answer 29

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

Question 30

motile flagella are found on..

Answer 30

sperm

Question 31

cilia can be found on...

Answer 31

airways, fallopian tubes, brain ventricles

Question 32

embryonic cilia generates..

Answer 32

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

Question 33

wave types of cilia vs flagella

Answer 33

cilia - asymmetrical wave | flagella - symmetrical

Question 34

what produces movement of cilia and flagella?

Answer 34

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

Question 35

general structure of intermediate filaments

Answer 35

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)

Question 36

microtubule assembly - dynamic instability model in vivo

Answer 36

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.

Question 37

gout treatment?

Answer 37

colchicine that blocks microtubule formations

Question 38

cancer treatments?

Answer 38

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

Question 39

vinblastine

Answer 39

cancer treatment, blocks MT assembly in mitosis

Question 40

TAXOL

Answer 40

stabalizes assembly of MT, disrupts mitosis. no longer "dynamic"

Question 41

centrosome

Answer 41

where the (-) ends organize, plus ends radiate out. 1 per cell

Question 42

most interphase cells have a single

Answer 42

MTOC

Question 43

tubule maturation

Answer 43

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

Question 44

MAPS

Answer 44

microtubule may be stabalized by capping proteins or MAPS

Question 45

the microtubules in cilia are

Answer 45

stable. not growing and shrinking

Question 46

positioning of the ER and golgi relies on

Answer 46

microtubules and motor proteins - kinesin stretches the ER from the nucleus out towards the microtubule+ ends - dyneine keeps the golgi near the nucleus (-) end

Question 47

PCD, primary ciliary dyskinesia

Answer 47

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

Question 48

situs solitus situs inversus heterotaxy

Answer 48

ss - heart backwards si - everything backwards h - everything in the center (problematic)

Question 49

Polycystic Kidney Disease

Answer 49

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

Question 50

non motile cilia are needed for

Answer 50

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

Question 51

Bardet-Biedl Syndrome

Answer 51

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

Question 52

bacterial flagella nd eurkaryotic flagella are..

Answer 52

unrelated

Question 53

motile cilia are

Answer 53

cynlinders of microtubules that bend