Lecture 7--cell motility

Adfcofilin and profilin promote actin treadmilling 2

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Unformatted text preview: admilling 2. The Arp2/3 complex promotes nucleation and branching of actin filaments and is activated by WASp proteins 3. Nulceation (formins) and bundling (fascin) proteins are required to form filopodia 4. Rho family GTPases organize actin filaments into specific structures Actin Depolymerizing Factor (ADF) / Cofilin: • Ubiquitous, conserved, stimulus-responsive regulators of actin dynamics in motile processes: • Embryonic development • Endocytosis • Cytokinesis • Listeria propulsion • Localized in motile regions of cells (at the leading edge) ADF increases the treadmilling of F-actin ADF binds F-ADP-Actin better than F-ATP-Actin T T D D D D ADF x 30 T Increase in Css => faster + end growth D D ADF ADP ATP ADF increases the treadmilling of F-actin by breaking actin filaments at the pointed end Profilin increases motility by promoting the recycling of actin molecule that binds to ATP bound G actin; catalyzes the echange of GDP for GTP; atin monomers are able to reassemble at the barbed end Profilin Actin filament Synergy between Profilin and ADF ADF ADF D D ADF T T Profilin Profilin T D x125 ADP ATP 1. ADF/Cofilin removes actin from the - end, increasing the concentration of G-actin Profilin P D 2. Profilin binding increases rate of actin-ADP to actin-ATP. Synergy between Profilin and ADF ADF/ colifili (green) causes monomers to break off and xhange ATP to ADP, facilitated by profilin Actin Dynamics 31 Branching of actin cytoskeleton atin lamellipodia Filament branching array the leading edge requires Arp 2/3 Arp 2/3 Branching of actin cytoskeleton atin lamellipodia Filament branching array the leading edge requires Arp 2/3 Arp 2/3 Fish keratocytes have large actin-filled lamellipodia Pat Wadsworth lab Fish keratocytes have large actin-filled lamellipodia cells that people get from fish skin; break off some gold fish skin, these things grow out.fastest cells that people have recorded; enormous lemelopodia; maybe they are so fast that the long lamelopodia gives it a lot of traction Pat Wadsworth tagged microtubules with GFP; microtubules lab are mostly found in the body, so it is actin that is rally allowing the crawling. Fish keratocytes have large actin-filled lamellipodia P...
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This note was uploaded on 02/23/2014 for the course MCDB 165A taught by Professor Iruela-arispe during the Winter '08 term at UCLA.

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