Cell Migration Flashcards
Why do cells migrate?
- Embryonic development
- Axon guidance
- Tissue repair
- Immune defence
How do fibroblasts move in tissue repair?
- Migrate into wound space and form fibrin clot
- Convert into myofibroblasts
Give 2 types of disease cell migration is implicated in
- Cancer
- Inflammatory diseases
What is the general model for cells migrating?
- Cells polarise
- Push front of cell forawrd
- Adhere via focal adhesions
- Retract the back of the cell
- Detach from substrate at rear
Which end of Actin is favoured for growth?
Barbed (positive) end
Outline Brownian Ratchet mechanism for membrane protrusion
- Actin filaments wobble just beneath plasma membrane
- as they wobble away from plasma membrane a new actin monomer can bind
- As polymer goes back it can push membrane forwards
What destabilises actin filaments?
Energy released by hydrolysis of ATP
What actin subunits are prefertially depolymerised?
ADP-actin
How does F actin stay the same length?
Treadmilling of actin due to nucleotide hydrolysis which acts as an inbuilt timer of filament stability
How is ADP actin removed from F actin?
ADP actin is recognised by enzymes which hydrolyse actin monomers
What is the rate limiting step of actin polymerisation?
Nucleation
What acts as a nucleus for polymerisation of actin?
A 4th actin monomer binding to actin trimer and stabilising it
Once an actin polymer has started how do monomers add on?
Spontaneously
What accessory protein is involved in the sequestration of actin subunits?
Thymosin
What does profilin do?
Prevent actin from binding to minus end so supports barbed end only elongation
