Lecture 16 : Cell movement Flashcards
What is the ‘comet trail’?
Formed by actin polymerisation, which helps to move vesicles or organelles
Actin based cell movement
- Movement comes from actin polymerisation
- Actin cytoskeleton very dynamic
- Actin monomers come together at the end of the filament
- rate limiting step is initial step of dimers and trimers coming together to form nucleus
- Stable nucleus rapidly elongates
- Actin polymer breaks down after by actin depolymerization
Minimum requirements :
- Nucleation of new actin filaments
- Capping of older filaments
- Recycling of monomers from old filaments (depolymerization and repolymerisation)
How do bacteria move through cell
Bacteria hijacks cell’s actin machinery to propel it through cell
Nucleation protein on bacterium’s tail end
How does nucleation of new filaments of actin occur
Trimers elongate into filaments
VCA proteins can bring arp 2/3 proteins close to form the trimer nucleus, then elongation occurs
What is the arp2/3 complex
- 7 protein complex, contains 2 actin-related proteins
What is the capping of filaments. Why do we need it
- capping proteins are dimers of alpha / beta subunits
- Bind to the barbed end near the cell membrane
- Stops polymerisation from happening
- Allows cell to switch on and off polymerisation
- Restricts polymerisation to the new filament barbed ends
- Prevents disassembly
How do we recycle the monomers
- ADF / cofilin does it
- Binds to actin monomer in ADP form
- Destabilises actin
What are filopodia
- FInger like projections from cell membrane
- Made of actin filaments
What are lamellipodia
- Thin sheet like projections at front of cell
- barbed ends, actin polymerisation, tracks
Stress fibres
- Contain actin adn myosin
- Generates tension in cell, generate cell force
Unfiniheed
