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MCBM Part 2 > Talbot - cytoskeleton and actin filaments > Flashcards

Talbot - cytoskeleton and actin filaments Flashcards

1
Q

what is the dynamic instability of actin filaments

A

the filament is always growing and shrinking = “treadmilling” any given G-actin appears to move along a treadmill adding to plus end and falling off minus end

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2
Q

how is actin formed

A

ATP-actin binds to another ATP-actin - but it is unstable so if adds a 3rd ATP-actin = trimer/oligomer that serves as nucleus and induces formation

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3
Q

how does actin provide structural support and integrity of epithelial cells

A

as microvilli and as an “adhesion belt” of actin linking cytoskeleton to adjacent cells

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4
Q

where is actin used to sense vibrations

A

stereocilia in inner ear

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5
Q

why is dynamic instability important

A

for motility - rapid assembly and disassembly (migrated/crawl through environment)

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6
Q

how are actin filaments involved in cell division

A

contribute to miotic spindles and form contractile ring that helps pinch cell into daughter cells

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7
Q

how are actin filaments arranged in stress fibers

A

anti-parallel contractile bundles (help pull cell body towards front/leading edge)

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8
Q

how are actin filaments arranged in the cell cortex

A

loose, 3D gel-like network underlying the plasma membrane

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9
Q

how are actin filaments arranged in filopodiums (spike like projections of plasma membrane near leading edge)

A

tight, parallel bundles all orientated in same direction

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10
Q

what are monomer binding (sequestering) proteins

A

ex. thymosin - bind to G-actin and prevent them from adding to growing end; decrease concentration of free action monomers

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11
Q

what are nucleating proteins

A

ex. ARP 2/3 complex and profilin

they interact with the minus end to promote growth

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12
Q

what does ARP 2/3 do (nucleating/cross linking protein)

A

promotes networks: forms branch off existing filament and forms complex web

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13
Q

what are severing proteins

A

cut actin filament in middle exposing ADP-actin - promotes depolymerization and converts gel-like structures into liquid

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14
Q

what are cross-linking proteins

A

ex. filamin and ARP 2/3 complex

cross-link actin at angles to each other, web like structure

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15
Q

what are end-binding (capping) proteins

A

CapZ= specific for plus end
Tropomodulin = specific for minus end
prevent assembly and/or disassembly at capped off ends

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16
Q

what are stabilizing proteins

A

ex. tropomysin
helps stabilize filament and prevent depolymerization by competing with depolymerizing proteins like cofilin/ADF for binding sites

17
Q

what are motor proteins

A

ex. myosin

walks along filaments

18
Q

what are bundling proteins

A

help arrange actin filaments in stable/parallel structures

19
Q

what do all types of myosin share

A

high degree of homology in N-terminus amino acid sequence, however C-terminus has variation

20
Q

what is the myosin 1 subfamily

A

in all/most eukaryotic cells - monomeric myosin with single ATPase head and tail

21
Q

which direction do myosins “walk”

A

towards the plus end of the actin filament

22
Q

what is the myosin 2 subfamily

A

“muscle” myosins - 2 subunits interact to form structurally polar homodimer with tails forming coil

23
Q

where are bi-polar thick myosin filaments located

A

in skeletal or cardiac muscle

24
Q

why are bi-polar thick myosin filaments called bipolar

A

one end is exposed and other is oriented into center - N-terminus is found at either end and C-terminus is towards center

25
Q

how are actin filaments related to muscular disease (muscular dystrophy)

A

dystrophin is actin binding protein that helps like cytosplasmic cortical actin to plasma membrane - if it is non-functional it leads to muscular necrosis

26
Q

how are actin filaments and neurological diseases related

A

synaptic function is dependent on synaptic morphology - on proper functioning of actin filaments -> Alzheimer’s, Parkinson’s, Huntington’s

27
Q

how are actin filaments and immunological diseases related

A

immune cells are involved in migrating, phagocytosis, cell to cell interactions and all require rearrangements of actin cortical filaments - impaired regulated leads to immunodeficient and autoimmune diseases

28
Q

how are actin filaments and cancer related

A

metasizing cells = migratory cells and actin moves cargo with myosin

MCBM Part 2 (15 decks)

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