lec 15: cell migration

single cell and collective cell

what are the two main subsets of cell migration

amoeboid (blebby or pseudopodal) and mesenchymal

what are the two types of single cell migration

epithelial and mesenchymal

what are the two types of collective cell migration

cells squeeze/bleb by extending cell membranes and contracting

how do cells move in amoeboid migration

some cells act as leaders, border cells keep cell-cell junctions as they migrate (important for wound healing)

how does sheet migration work

1. cells attach to substrate via integrins

2. cells protrude membrane via actin in direction of migration

3. protrusion attaches, myosin pulls cell forward

4. repeat, old focal adhesions at back of cell break and new ones form at front

what are the main 4 steps of migration

cell can’t move forward

what happens if actin filaments are disengaged w focal adhesions

traction

what happens if actin filaments are engaged w focal adhesions

lamellipodia are wide and thin from branched f-actin, filipodia are skinny and thin spikes

whats the difference between lamellipodia and filipodia

Cdc42

which GTPase controls filopodia formation

Rac

which GTPase controls lamellipodia formation

Rho

which GTPase controls stress fiber formation and contraction

Rho and Rac (mutual inhibition to maintain balance)

which two GTPases fight with each other

bundles

which actin based structures are most likely to be found in filopodia

they remodel actin by activating WASP, which activates Arp2/3 complex to extend or branch actin

how do cells change direction

adhesion strength (stronger attachment = harder to move, flatter shape)

what determines how fast cells move

establish and maintain polarity

what is the main role of microtubules in migration

tips of growing axons made by actin protrusions

what are growth cones

growth cone plasma membrane senses attractant and repulsive cues

how do growth cones respond to cues to find right path

form concentration gradient sensed by growth cone, secreted by other cells

how do long range cues work

on surface of other cells or bound to ECM, direct contact

how do short range cues work

cells lose polarity, remodel junctions, and start expressing migratory integrins

how do cells transition from epithelial migration to mesenchymal migration