cell migration Flashcards

1
Q

what are small GTPases

A
  • Small - 21 kDa proteins
  • One of the largest groups of signalling proteins: Ras superfamily
  • Change conformation upon activation e.g gpcr
  • Bind and activate downstream effectors
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2
Q

effect of active ARf6

A

inhibitory

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3
Q

what does signalling active mean

A

signalling = gtp active

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4
Q

what does hydrolysis active mean

A

hydrolysis = chopping up enzyme = switching off

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5
Q

GTPase structure

A
  • Phosphate coordination by P-loop
    • phosphates are coordinated by p loop
    • controls shape of gtpase
  • Mg2+ essential for nucleotide binding and activity
  • Switch regions bind effectors
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6
Q

how can gtpase activity be measured

A

measuring effector binding by measuring activity of switch proteins
staining doesn’t work bc too small

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7
Q

why is catalysis of hydrolysis important

A

GTP hydrolysis is a biologically crucial reaction, being involved in regulating almost all cellular processes

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8
Q

how does catalysis of GTP hydrolysis occur

A
  1. attacking water -> catalytic glutamine
  2. counteracting of negative charge at phosphates
    - glutamine 61 holds water in place best
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9
Q

molecules involved in cyclic regulation of gtpases

A

GEFs - Accelerate exchange of GDP for GTP and stabilises nucleotide free form = GDP can fall off and GTP can come in
GAPs - accelerate hydrolysis of bound nucleotide

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10
Q

how do GTPase activating proteins work

A
  • less flexible structure to increase change of reaction
  • have restricted freedom to lower entropy barrier and accelerate hydrolysis = stable catalytic glutamine
  • argenine brings in a + charge to draw - charge away from phosphate
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11
Q

how do GEFs work

A

stabilises nucleotide free form = GDP can fall off and GTP can come in = Accelerates exchange of GDP for GTP

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12
Q

how does T17N mutation affect Rac in GEFs

A
  • disrupts nucleotide binding at all
  • turns off all gtpases in cell
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13
Q

domain and family of GEFs

A

dbl-homology domain
dock-family
sec7 domain

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14
Q

how do GTPases control actin-based motility

A

stimulate a cell with growth factor → activation of cdc42(rho gtpase) → formation of filopodia (arms) → activation of Rac1 → formation of lamellipodia (head moving forward) → RhoA activation → actin stress fibres are formed causing contraction of cell

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15
Q

gtpase forming filopodia during actin-based motility

A

cdc42 (rho)

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16
Q

gtpase forming lamellipodia during actin-based motility

A

activation of Rac1

17
Q

gtpase forming actin stress fibres and contraction of cell during actin-based motility

A

rhoA

18
Q

how does rhoA cause actomyosin contraction

A

GTP-RhoA activates Rho K → phosphorylates MLC → contraction of A-M contraction = pulls cell forward, muscle movement of organism

19
Q

features of cdc42, rac and rhoa signals

A
  • Cdc42/Rac are protrusive signals (grow)
  • RhoA is a contractile signal (shorten)
20
Q

effect of rac 1 localisation on migration

A

activity at front of cell = positive effect forward
spread out = less movement
without direction e.g skin fibroblasts they can’t move in right place to heal wound