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32 Cards in this Set
- Front
- Back
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3 cytoskeletal systems |
microfilaments microtubules intermediate filaments |
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microfilament |
actin binds ATP rigid cells, networks regulated from large number of locations HIGHLY dynamic polarized tracks for myosin contractile |
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microtubules |
aB-tubulin bind GTP rigid not easily bent regulated from SMALL number of locations highly dynamic polarized tracks for kinesins and dyneins long range transport LARGEST- |
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processes of microfilaments |
morphology microvilli- increase SA adherens belt- seal off apical from basolateral fliopodia- cell movement- feet lamellipodium- push whole cell out- elongate and stretch cell cortex- strength the PM on back stress fibers- hold cell together contractile rings- mitosis |
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extracellular signals |
help with wounds and growth factors are released extracellular signal- binds to receptor the receptor will associate with GEF the GEF will exchange GDP for GTP on Rho Rho-GTP- landing pad to promote directional growth of MF
only receptors where conc is high is where itll move |
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actin |
most abundant protein- oldest protein to evolve conserved between cells ATP binding and Mg binding 4 domains- has cleft- where ATP binds
2 forms free- G-actin Filamentous F-actin ATP hydrolysis AFTER it polymerized polymerization doesnt need hydrolysis BUT influences polymerization kinetics |
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structure of MFs |
polarity right-handed double helix myosin decorates it an points to the (-)/ arrow ATP cleft is exposed on (-) and hidden at (+)/barbed grow? add G-actin to the (+) |
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poly and depoly |
needs time for nucleation- 3 actin nuclei are formed by FORMINS & Arp2/3 elongation is fast- add on both ends bias to (+) gets to steady state why? 1- run out of free G-actin 2- (-) actin falls off and then will add to (+) |
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formins and Arp2/3 |
high affinity landing pad for G-actins formin- single linear filaments Arp- make branches- push out wide area |
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critical conc |
if g-actin is greater then net growth if equal- steady state once hit Cc- monomer conc is steady as the filament increases monomer conc is steady bc will add both ends have different conc |
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difference in Cc |
(+) has lower Cc than (-)= 12x more when above both Cc- (+) grows faster than (-) when in between the Cc- the (+) will add and (-) will fall off= treadmilling
in reality- level of actin is constant and above both Cc |
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regulation of growth capping proteins |
block assembly when above Cc disassembly when below Cc CapZ- prevent adding to (+) Tropomodulin- prevent disassemble on (-) |
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Cofilin |
fragment the filament into small filaments with ADP-actin will recycle scissors- RAPID to collapse make little F-actin that act as new filaments happens on trailing edge |
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profilin |
convert ADP-actin to ATP-actin promote filament growth on the (+) end only |
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thymosin-B4 |
keep ATP-g-actin from polymerizing at BOTH ends control without changing conc of actin |
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ALS |
somatic mutation profilin is mutated aggregates on itself and cant function to direct MF growth neurons can direct axons= paralysis |
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MF organization |
strong when bundle together and cross link TIGHT bundles= FIMBRIN- microvilli- strong rigid LOOSE bundles= A-ACTININ- more space- myosin motors can move over them cable structure- SPECTRIN large networks- leading edge- FILAMIN- branch and push out dystrophin- connect to PM- if messed up then no contractile force
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Spectrin- cables to connect MF |
spectrin are attachment points of MF- spread stress across circumference is messed up- sickle cell anemia ANKYRIN- connect spectrins tails BAND 3-antiporter of HCO3- and Cl-- anykrin binds to it on PM BAND4.1- associate with spectrin head to the MF GLYCOPHORIN- associate with BAND4.1 to anchor the MF |
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signal-induced changes |
chemotaxis signal CDC42 Rac Rho CDC and Rac- MOBILIZE |
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Rho |
LipoproteinA pro-inflammatory cytokine they bind to receptor to activate the lipid anchored G-protein induce formin to make STRESS FIBERS |
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Rac |
fibroblast growth factor platelet derived growth factor bind to receptor to activate Rac to activate WAVE to activate Arp2/3 make lamellipodia- more SA BRANCHED |
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CDC42 |
stimulate WASP to Arp2/3 to make filopodia stimulate Par6 to polarity BRANCHED |
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determine where and how MF grow |
formin nucleates MF in response to extracellular signal that activate Rho-GTP
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formin |
inactive- folded when bind to Rho-GTP- associate with formin to unfold it unfolded has 2 other domains 1 to attract profilin- actin 2 to get the actin from 1- holds the (+) and adds on that end= push the PM |
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Arp2/3 |
branched! NPF associate with actin to associate with Arp2/3 the Arp will bind to side of MF Arp- hairpin like formin 70 degrees
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WASP |
will associate with CDC42 bind to actin that has NPF and Arp2/3 with another MF |
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moving forward |
cross talk of different G proteins- can others on or off signalling on leading edge will let the trailing end to contract- myosin motors will cause the stress fibers to contract! make integrins to detach |
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trailing edge proteins |
myosin-contraction cofilin- depolymerization thymosin B-4- bind to actin so cant add on trailing edge |
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leading proteins |
profilin Arp2/3 CDC42 and RAc for branched |
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dominant negatives |
Rac, Rho, CDC42- cant exhcnage GDP for GTP wont close the wound Rho has to most effect in less closure Cdc is less effected dominant bc only need one bad type |
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dominant active |
cant hydrolyze GTP- always active! loss directionality Rho- lots of stress fibers- stretch self apart Rac- networks within Cdc42- networks in and out |
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cell race |
tumor cells are the fastest slippery- dont attach to substrate well dont proliferate in extracellular signal- dont need them bc active al lthe time ability to push on PM |
