microfilaments text and image sources are included using the notes function of this file...
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Microfilaments
Text and image sources are included using the notes function of this file
Microtubules Microfilaments
Microfilament(thin filament)
structure
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25nm
--- 7-8nm
G-actinmonomer
ATP
minus
plus
G-actin (42-43kD; 375 aas)(minus)
(plus) Changes upon hydrolysis
Animation
Intrafilament contacts
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Polarity of assembly(in vitro assay) QuickTime™ and a
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Red arrow = minus endGreen arrow = initial plus end
Bulls-eye = contact point on surface
Video
+
-
+ G-actin, ATP
S1 Decoration
+
-
S1 decoration reveals
microfilament polarities in
situ
a. Cytoplasm (mixed polarities)b. Stress fibers (bundled mixed polarities)c. Lamellipodia (uniform polarity, points in)
The Angel of Death Mushroom
Phalloidin
Amanita phalloides
Cells labeled with Phalloidin (F-actin)
and DNase I (G-actin)
Actin Binding Proteins (ABPs)
modulate architectures
“. . . the actin cytoskeleton is a complex three-dimensional molecular jigsaw puzzle” - Tom Pollard
Profilin is involved in ATP recharge
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profilin
Cofilin weakens subunit interactions
by structuralintrogression
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Alpha-actinin crosslinks
microfilaments
Amoeboid motility
uses Gelsolin
Actin subunit
Gelsolin (partial structure) in presence of Ca++
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Video
F-actinmotilities
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Composite time lapse segments
Actin dynamics at the leading
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GFP::actin in a tissue culture cell
2 time-lapse video sequences
Axonal growth cones
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GFP-actin dynamics
Microtubules are excluded from the periphery
Cell microinjected with fluorescent tubulin to label microtubules
Video
Video
Treadmilling within the lamellipodium
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Video
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Keratocyte motility
Video
Branching out on the family tree:
the Arp2/3 complexQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
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Arp2/3 immunolocalization
Nucleation PromotingCoronin Factors (NPFs)
WASp/SCAR/Wave
70o
minus
plus
The Actin Family Tree
Formin those long filaments
G-actin monomer
-
+
Assembly Cycles
translation
G-actinATP
DynamicF- actinADP microfilament
StableF-actinmicrofilament
G-actinADP
Thymosin
Profilin
ADP(exchange)
ATP
ATP
CCT
Arp2/3
WASpSCAR
StabilizingABPs
SeverinGelsolin
PIP2
WASpVASp
Formin VASp
NPF: VASp(vasodilator stimulated
phosphoprotein)
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Video
F-actinAnd VASp
Signal transduction links
Cdc42
Rac
Rho
WASp
WASp*P
PIPkinase
MLCK
Arp2/3
PIP
PIP2
Myosin
Formin
FilipodiaLocalized Initiation
LamellipodiaFrontal Initiation
Increased Turnover
Stress fibersForm and Tension
G-proteins
Stress fibers distribute forces
Arrows highlight microtubules adjacent to the stress fiber bundle
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Getting in shape
Neutrophil motility
Video
Microvilli
Anchored in the terminal web
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Stereocilia
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MyoVIIa is involved in
Ca++ regulated adaptation
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Act’in Up
Listeria monocytogenes moving in PtK2 cells
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Video