Cytoskeleton Flashcards
(45 cards)
1
Q
Microfilaments
A
- actin
- binds ATP
- form rigid gels, networks, and other linear bundles
- regulated assembly from large number of locations
- highly dynamic
- polarized
- tracks for myosins
- contractile machinery and network at the cell cortex
2
Q
microtubules
A
- alpha beta tubulin dimer
- binds GTP
- rigid and not easily bent
- regulated assembly from a small number of locations
- highly dynamic
- polarized
- tracks for kinesins and dyneins
- organization and long-range transport of organelles
3
Q
intermediate filament
A
- subunits don’t bind a nucleotide
- great tensile strength
- assembled onto preexisting filaments
- less dynamic
- unpolarized
- no motors
- call and tissue integrity
4
Q
F-actin
A
- filament= linear chain of actin subunits
- in vitro polymerization of G-actin monomers forms F-actin
- major component of microfilaments
- polarity: addition of subunits at + end, removal of subunits at - end
5
Q
G-actin
A
- actin exists as a globular monomer called G-actin
- can polymerize into F-actin
6
Q
Critical concentration
A
- the concentration of G-actin where there is no net change in length
- Cc+= 0.12 micrometers
- CC- = 0.60 micrometers
- treadmilling
7
Q
examples of actin filaments
A
- microvilli
- cell cortex
- adherens belt
- filapodia
- phagocytosis
8
Q
actin filament pointed end
A
- negative end
9
Q
actin filament barbed end
A
positive end
10
Q
actin assembly
A
1) nucleation phase= G-actin combines into 2/3 subunits length
2) elongation phase= rapidly increases in length by addition of monomers to both ends
3) steady state= G-actin monomers exchange with subunits at filament ends, but no net change in total length
11
Q
Cytochalasin D
A
- fungal product
- inhibits F-actin polymerization
12
Q
Phalloidin
A
- from the Angel of Death (death cap) mushroom
- promotes polymerization
- actin poison
13
Q
Thymosin B4
A
- sequestering protein
- increases G-actin pool
14
Q
Profilin
A
ATP/ADP exchange
15
Q
Cofilin
A
- severing proteins
- makes more filament ends
16
Q
Capping proteins
CAPZ and Tropomodulin
A
- ex: CAPZ–> caps the positive end (stops assembly)
- Tropomodulin–> caps the negative end (stops dissembly)
- block assembly and dissembly at filament ends
17
Q
Formin
A
- facilitates nucleation
- nucleates actin filaments
- inserts additional subunits
18
Q
Optical traps(tweezers)
A
- can measure force of a myosin molecule and its association with actin
19
Q
Listeria monocytogenes
A
- bacterium
- food poisoning–> death
- motile with F-actin–> organize it into a “comet tail”= bacteria become motile and can spread from cell to cell
- crosses the placental barrier
20
Q
Arp2/3
A
- during endocytosis
- driven by F-actin like listeria
- can be analyzed in cell free systems with rhodamine-labeled transferrin and fluorescein-labelled actin
- burst of Arp2/3-dependent actin assembly drives internalization of endocytotic vesicles away from the plasma membrane
- endosomes bind and activated Arp2/3 to make actin tails that propel them through the cytoplasm
21
Q
opsonization
A
- opsonins(antibodies) coat antigens–> immune cells recognize and engulf antigens
- shape phagocytic cup
22
Q
phagocytosis
A
- invading bacteria is coated with antibodies= opsonization
- Fc region of antibodies is displayed–> cell assembles a contractile actin structure that results in internalization and engulfment of the bacterium
- once in phagosome, the bacteria is killed and degraded by enzymes from lysosomes
23
Q
actin and cell movement
A
- locomotion is driven by actin network beneath the cell membrane and can be divided into 3 components
- extension (protrusion of leading edge)
- adhesion
- translocation
- de-adhesion of lagging edge
24
Q
Diaphanous Gene
A
- actin assembly defect in hair cells
- inherited hearing problems
- formin-like molecule
25
Brain aging in fruit flies by suppressing F-actin
- flies live longer if fed a low protein diet--> aging neurons fed the high protein diet accumulate excess F-actin
- Rapamycin can extend Fly lifespan and brain neurons having less F-actin as a result of rapamycin treatment
- less F-actin= lived 25-30% longer and were healthier because F-actin inhibits the removal of dysfunctional cellular components in cells such as proteins and organelles
26
intermediate filaments
- toughest of the three
- form parallel dimers through a highly conserved coiled-coil core domain
- tetramer is formed by antiparallel, staggered, side-by-side association of two identical dimers--> associate end to end and laterally
27
Type I and II intermediate filaments
- Type !: acidic keratins
- Type II: basic keratins
- both are on epithelial cells and used for tissue strength and integrity
28
Type III Intermediate Filaments
- Desmin, GFAP, vimentin
- in muscle, glial cells, mesenchymal cells
- function= sarcomere organization, integrity
29
Type IV Intermediate Filaments
- neurofilaments
- in neurons
- used for axon organization
30
Type V Intermediate filaments
- laminins
- in nucleus
- used for nuclear structure and organization
31
Epidermolysis Bullosa Simplex
- defect in keratin filament
- basement membrane-> regeneration layer-> epidermis
- cells will shear in half on regeneration layer causing painful blisters
- caused by defects in the COL7A1 gene which encodes type VII collagen(important to anchoring of fibrils that attach the epidermis to the dermis)--> layers of skin separate, causing blisters
32
Operation Desert Storm
- mustard gas
- similar effect as epidermis bullosa simplex
33
VYJUVEK
- restores ability of cells to make functional type VII collagen protein and form anchoring fibrils
- applied topically directly to wounds and will help the wounds heal and prevent blisters from forming
34
microtubules
- building block: alpha beta tubulin dimer
- alpha tubulin= non-exchangeable GTP
- Beta tubulin= exchangeable GTP
- 13 protofilaments (in a singlet)
- tracks for molecular motors that can move vesicles, organelles
35
MTOCs
- microtubules are assembles from microtubule organizing centers (MTOCs)
36
Microtubule treadmilling
- growing microtubule= blunt end
- shrinking microtubule= curls like rams horns
- microtubule with GTP beta tubulin on end is favored to grow, microtubule with GDP beta tubulin will undergo rapid disassembly
37
MAPs
- microtubule associated proteins
- MAP2= long arm
- Tau= short arm; microtubule stabilizing protein
- grow axon-like processes
- both contain approximately the same number of microtubules
- Tau is involved in Alzheimers and Parkinsons (forms tangles when imbalanced--> neurodegenerative diseases)
38
Kinesin-13 and Stathmin
- kinesin-13: enhances disassembly
- stathmin= binds selectively to curved protofilaments and enhances their disassociation from a microtubule end
39
XMAP215
- supports polymerization
- binds protofilaments of growing microtubule ends
- can also bind alpha beta tubulin dimers to enhance growth
40
Katanin
severs longer microtubules during neuronal development
41
Colchicine
- depolymerizes microtubules
- gout--> cancer
42
Taxol
- promotes polymerization of microtubules
- disrupts mitotic spindle--> blocks growth of cancer cells in body
- triggers dividing cells to commit to apoptosis
- blocks Bcl-2
43
kinesin
- anterograde movement
- transport vesicles from the - end to the + end of a stationary microtubule
- ATP is required for movement
- walks down microtubule
44
Dynein
- retrograde= toward - end
- 8 subunits
- power stroke
45
Kartagener Syndrome
- ciliary dyskinesia
- defect in dynein arms in cilia
- affects movement of cilia and flagella
- can cause lung problems
