Handout 5 - Actin and Cell Movement

Handout 5 - Actin and Cell Movement - Actin Cytoskeleton...

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Actin Cytoskeleton Properties of Actin Actin assembly Role of ATP Treadmilling Role of actin in cell movement Actin is required for movement Actin assembly can drive movement Regulation of actin assembly in cells Proteins involved in actin assembly/disassembly Turning the protein involved in assembly and disassembly ON and OFF Building stable actin structures
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Actin: stable structures and dynamic structures
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Actin Polymarization Can Do Work G-actin F-actin + released energy Released energy can do work Work can result in membrane extension of leading edge or muscle contraction. G-actin F-actin + membrane extension
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How do we know that actin polymerization is required for migration? Use toxins that disrupt actin function Actin destabilizers: Cytochalasin (fungal alkaloid) binds (+) end, prevents subunit addition Latrunculin (toxin from sponges) binds G-actin, inhibits assembly into filaments Actin stabilizers: Phalloidin (cyclic peptide from poisonous mushroom) binds and stabilizes actin filaments, preventing depolymerization
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Effects of latrunculin on keratocyte migration
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How do we know that polymerization drives cell movement? The answer: from work with bacterium Listeria monocytogenes
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Listeria Movie: Comet tails Movie: movement in cell extract
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Listeria movement in vitro Movement only requires : Bacteria (Listeria) Actin ATP a few proteins to facilitate actin polymerization Conclusion : Listeria can induce actin polymerization to move. Actin polymerization is sufficient to drive movement.
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Hypothesis about Listeria movement in vitro No Motor - Polymerization drives movement Motor - required Polymerization (necessary), but not sufficient for movement.
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Listeria ActA protein Listeria triggers branched polymer formation through ActA (not a motor protein) Is ActA sufficient to drive motion?
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Lamellipodia are filled with branched F-actin polymers Movie: Lamellipodia
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needed for Movement? Plastic Bead
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This note was uploaded on 06/12/2010 for the course MCB 252 taught by Professor Prasanth during the Fall '08 term at University of Illinois at Urbana–Champaign.

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Handout 5 - Actin and Cell Movement - Actin Cytoskeleton...

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