Actin based cell movement

#Identify and explain the basic mechanisms controlling actin-based motility #Give examples of actin-based motile structures #Explain how ABP’s with different activities can work together to make cells motile #Explain how cells co-ordinate contraction, polymerisation and adhesion to move

What is a key feature of the actin cytoskeleton

highly dynamic

what controls Actin dynamics

Actin-binding proteins

what is recruited by Listeria

host cell Actin and ABPs

what allows listeria to propel

hijacking of cells actin macheinery

4 minimum requirements for actin based motility

Nucleation of new filaments, capping old filaments, recycling monomers of old filaments

what is the favourability of trimers and dimers

unfavourable

in the nucleation of new proteins how do you overcome the unfavourable reaction

Several protein components are known to nucleate from the fast-growing end of the actin filaments

give the three types of capping proteins

Capping proteins, Gelsolin, gCap39

where do you find capping proteins

muscle and non muscle

what is Gelsolin

severs actin filaments and binds to the plus ends

where is gCap39 found

non muscle

what does is gCap39

similar to gelsolin but does not severe

why is there a need for capping proteins

switch polymerisation off and on, restricts polymerisation and prevents disassembly

where do all capping proteins bind

barbed end

what recycles actin monomers

ADF / Cofilin

what does the binding of Cofilin to actin filaments do

destabalises them

how large is the diameter of filopodia

50 – 300 nm in diameter

how many actin filaments in a bundle of filopodeia

10-30

what are fiopedia used for

Used in sensing the enviornment

what is a lamellipodeia

•Thin sheet like protrusions of membrane at front of cell

what do Lamellipodia do

•Contain a dense network of branched actin filaments – barbed end pointed towards tip

what is actin polymerisation used for in Lamellipodeia?

•Actin polymerisation for used to push leading edge of cell forwards

do filopedia and Lamellipodeia often appear together or apart

together

what are stress fibres

•Highly ordered structures containing cross-linked actin filaments and myosin

size of stress fibres

1- 2uM in length

the use of stress fibres

•Used to generate tension within the cell

what are Dorsal and ventral stress fibres

main generators of cell force

Transverse arcs

movement of actin towards centre of the

3 movement stages

Protrusion, Translocation and Detachment

how do new adhesions form

via integrins and new stress fibres

actin-myosin contractillity or what allows adhesion

stress fibres

what is traction generated by

adhesion

detatchment

1.Actin-myosin contractility

2.Traction generated by adhesion (integrins)

3.Proteases degrade contacts