Lecture 31: Cell Motility II

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10 Terms

1
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How do bacteria, such as listeria, hijack host actin cytoskeleton

ActA in bacteria can activate Arp 2/3

  • result:polymerization at surface of bacteria so it can now be displaced / moved

can also recruit coffin to sever old actin at the minus end so that we can remain at Cc and keep adding to the plus end

<p>ActA in bacteria can activate Arp 2/3</p><ul><li><p>result:polymerization at surface of bacteria so it can now be displaced / moved</p></li></ul><p>can also recruit coffin to sever old actin at the minus end so that we can remain at Cc and keep adding to the plus end</p><p></p>
2
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what kind of actin can push the membrane forward

branched actin

  • activation of ARP 2/3 change dynamics of plasma membrane

<p>branched actin</p><ul><li><p>activation of ARP 2/3 change dynamics of plasma membrane</p></li></ul><p></p>
3
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name some key differences between the protrusive actin structures filopodia and lamellipodia

filopodia:

  • sent out first to make sure things are going in the right direction

  • unbranched → formin

  • finger like protrusions

  • CDC42

Lamellipodia

  • sheets that protrude

  • branched → ARP 2/3

  • Rac

<p>filopodia: </p><ul><li><p>sent out first to make sure things are going in the right direction</p></li><li><p>unbranched → formin</p></li><li><p>finger like protrusions </p></li><li><p>CDC42</p></li></ul><p>Lamellipodia </p><ul><li><p>sheets that protrude </p></li><li><p>branched → ARP 2/3</p></li><li><p>Rac </p></li></ul><p></p>
4
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what is a stress fiber

a contractile bundle that is unbranched (therefore formin nucleated) and is associated with non muscle myosin

<p>a contractile bundle that is unbranched (therefore formin nucleated) and is associated with non muscle myosin </p>
5
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briefly describe cell crawling

  • protrusion, attachment, contraction

actin polymerization at plus end protrudes lamellipdium

integrin help attach to substratum/ECM

stress fibers in back allow for actin myosin contraction

<p>actin polymerization at plus end protrudes lamellipdium </p><p>integrin help attach to substratum/ECM</p><p>stress fibers in back allow for actin myosin contraction </p>
6
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<p>what is the function of integrins</p>

what is the function of integrins

they link the cytoskeleton and ECM/substratum

  • active when stretched out

  • link through focal adhesions

<p>they link the cytoskeleton and ECM/substratum </p><ul><li><p>active when stretched out </p></li><li><p>link through focal adhesions </p></li></ul><p></p>
7
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Summarize how different members of the Rho family of GTPases alter the organization of actin filaments.

Rho: promotes stress fibers (contractile actin)

  • effector: whatever controls actin myosin contractility

  • rho must be in back for directionality (visualize how the cell crawls)

Rac: promotes lemellipodial extension

  • effector: ARP 2/3

  • must be in front for protrusion

CDC42: promotes filipodia

  • effector: formin

  • must go first in front to make sure everything is in correct direction

  • initiates actin polymerization

8
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what would occur if Rho was mutated

this would affect cell crawling

  • double negative: locked in the inactive GDP bound state

9
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how do Rho family GTPases promote actin filament nucleation

they stimulate profiling-bound actin recruitment to NPF/WAVE and forming

<p>they stimulate profiling-bound actin recruitment to NPF/WAVE and forming</p>
10
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WASP/WAVE/NPF os activated downstream of ______ leading to Rac activation and ____ generation at cell edge

CDC42

PI(4,5)P2

<p>CDC42</p><p>PI(4,5)P2</p>