Actin in Locomotion Flashcards
What happens when 2 cells contact each other?
They stop moving in that direction, repolarize, and migrate away from one another
What is the structure of actin stress fibres?
Thick bundles of microfilaments held together by alpha-actinin and decorated with myosin II molecules
What do actin stress filaments do?
- Cause cell contraction
- Allow mechanical force to be applied across cell
Where are actin stress fibres found in the cell?
Span cell and anchor at plasma membrane focal adhesions
Why is the distance between actins crucial in actin stress fibres?
The space must be sufficient for myosin II to allow for actin sliding
What supports lamellipodia?
A mesh of actin underneath
What do lamellipodia require for formation?
Arp 2/3 complex
Where does Arp 2/3 bind?
To the side of an exisiting filament
At what angle do new actin branches in lamellipodia form at?
70º
What on nucleation promoting factors activates Arp2/3?
VCA domain
On which terminus is the VCA domain found on nucleation factors?
C terminus
How does the VCA domain help actin to branch?
- Binds to Arp2/3 and another actin monomer which is a stabilised polymer of almost actin
- This is sufficient to nucleate actin polymerisation and trigger formation of actin filament
What is the structure of filopodia?
Thin actin-rich projections
What is the model for the formation of filopodia?
- Tip complex binds and allows barbed ends to elongate continuously without being capped
- These barbed ends drift together and elongate
How is filament crosslinking initiated in filopodia formation?
Via recruitment of fascin
