slide set 12 Flashcards

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1
Q

for most cells, motility is guided by….

A

extracellular cues!

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2
Q

small G proteins

A

small G proteins control where actin polymerizes and the type of network formed

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3
Q

small G protein experiment

A

cells injected with constitutively active forms of small G proteins
cells were then stained for filamentous actin

constitutively active = consistently formed no matter what the cell needs

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4
Q

filopodia

A
  • finger-like projections that extend from surface of cells
  • G protein Cdc42 is activated on inner surface of the plasma membrane, which stimulates actin polymerization and bundling (parallel bundles)
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5
Q

Cdc42 activation

A

activated Cdc42 targets members of the WASp protein family

patients deficient in WASp have Wiskott-Aldrich syndrome (immune cells have abnormal actin-based motility

WASp activates formins and bundling proteins

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6
Q

lamellipodia

A

G protein Rac is activated at the cell periphery, which stimulates actin polymerization and sheet-like extensions (branched, dendritic network)

Rac also activates WASp proteins, which then activate Arp2/3

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7
Q

weird diagram

A
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8
Q

Rac

A

promotes branched actin network assembly AND inhibits myosin activity

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9
Q

stress fibers

A
  • stress fibers are contractile bundles of actin filaments and myosin
  • G protein Rho activation stimulates bundling of actin filaments with myosin II into stress fibers (and also clustering of integrins and other proteins to form focal adhesions)
  • Rho activates formins and myosin
  • Rho inactivates cofilin, so filaments are more stable
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