Invasion - Regulation of Cell Migration Flashcards
: Most human tumours are derived from X tissues
Epithelial
2 types of cell migration?
- Individual cell migration
- Collective cell migration- group of cells which maintain cell-cell contacts
What is needed uniquely for collective cell migration regarding cell adhesion
- Cadherins and gap junctions are needed for collective migration
Examples of times cells need to move? (3)
organogenesis and morphogenesis, or in wound healing
What are the usual stimuli for cell movement (2)
growth factors or chemoattractants
How does the morphology of a cell change when they are stimulated to migrate
retraction at the back of the cell and protrusions appear at the front- this helps the cell to move efficiently
What stop cells moving and guides them in the right direction
Contact inhibition
What specialized structures allow efficient movement (3)
focal adhesions, lamellae, filopodium
What are focal adhesions
Points where the cell can hook on to ECM proteins
Points where the cell can hook on to ECM proteins are known as …
focal adhesions
What protein facilitates hooking of the cell to ECM proteins
Integrins
What ends at the point of focal adhesions
Actin filaments
Tracks of actin filaments end at …
focal adhesions
What are integrins
are transmembrane protein dimers with a short cytoplasmic tail with docking sites for cytoskeletal proteins
What are filopodia (consist of (2)… shape…)
Finger-like protrusions rich in actin filaments (and vinculin)
What do filopodia do
- They allow cells to sense their environment and coordinate their movement
What are lamellipodia (consist of … shape…)
Sheet-like protrusions rich in actin filaments
What do lamellipodia do (how do they facilitate movement)
- Sheets project to the front and then ruffle back to allow the cell to move
2 types of motility? (regarding cause of movement)
MOTILITY can be HAPOPTATIC (random) or CHEMOTATIC (has purpose e.g. responding to growth factor etc.)
4 stages of cell movement?
- Extension
- Adhesion
- Translocation
- De-adhesion
2 types of actin
G and F actin
Difference between G and F actin
- G actin (small and soluble) and F actin which is polymerized G actin. F actin is also polar
What is the polymerised filamentous form of actin known as
F actin
Filaments are X (have different structures in one end compared to the other)
Polarised
organisation of F actin in filopodium?
Bundles of parallel filaments
organisation of F actin in stress fibres?
antiparallel contractile structures
organisation of F actin in lamellipodium?
Branched and cross linked filaments
What three structures can actin filaments form
Lamellipodium, filopodium and stress fibres
What is the rate limiting step in the organisation of the cytoskeleton
Nucleation
What does nucleation of actin achieve
formation of trimers to initiate polymerization
What proteins are need for nucleation? what complex does this form
- Arp2 and Arp3 form ARP complexes
How does ARP complex interact with actin (which end does it bind to)
- These bind to actin monomers and will be bound at the –ve end of the filament when it has formed
What proteins facilitate elongation of filaments
- Prolifin
What does prolifin do (which end)
- Prolifin is a protein that binds to actin monomers (G-actin) and brings them to the actin filament to the +ve end to elongate it
What does thymosin do
- Thymosin is a protein that binds to actin monomers but doesn’t bring them to the actin filament -> Inhibit the polymerization process
What do sequestering protein beta4thymosin and ADF/cofilin do
- Sequestering proteins called beta4-thymosin and ADF/cofilin bind to monomers but do not inhibit polymerization
What protein inhibits the elongation of actin filaments
- Thymosin is a protein that binds to actin monomers but doesn’t bring them to the actin filament Inhibit the polymerization process
What proteins sequester actin monomers
- Sequestering proteins called 4-thymosin and ADF/cofilin bind to monomers but do not inhibit polymerization
What do capping proteins do
- Capping proteins regulate the elongation process of the filaments
What is MoA of capping proteins
- They bind to the end of the filament and prevent monomers binding
- After a capping protein binds to one end, you get disassembly of some of the filament which causes shortening of the filament
What capping proteins bind to the negative end of actin filaments (2)
Tropomodulin
Arp complex
What capping proteins bid to the positive end of actin filaments (3)
Cap Z
Gelsolin
Fragmin/severin
What do severing proteins do
Regulates filament size
What happens in unsevered population of actin filaments regarding growth
- In un-severed populations, filaments grow and shrink relatively slowly
What happens in severed population of actin filaments regarding growth
- In severed populations, actin filaments grow and shrink more rapidly
Example of severing proteins
Gelsolin, ADF/cofilin, fragmin/severin
Bundles of parallel filaments describes the structure of …
Filopodia
antiparallel contractile structures describes the structure of …
Stress fibres
Branched and cross linked filaments describes the structure of …
Lamellipodia
What does fascin do
Protein that bundles filaments at a particular distance
What does FIMBRIN do
Does the same but at longer distance between filaments
What does alpha-ACTININ do
Bundles
What does SPECTRIN do
Cross-links filaments at particular angles
What does FILAMIN do
Cross-links filaments at particular angles
What does DYSTROPHIN do
Cross-links filaments at particular angles.
Proteins that bundle?
FASCIN
FIMBRIN
-ACTININ
Proteins that cross link?
SPECTRIN
FILAMIN
DYSTROPHIN
Depending on the width of the gap between filaments, motor proteins can or cannot ……..
travel along the actin filaments
What is responsible for branching in lamellae
- Arp2 complex
What angle does branching occur at
70 degree angles
What is gel-sol transition and when does it take place and by what
When the cell needs to move, the membrane will need to flow- in gel form, the actin cytoskeleton is rigid, but in sol form, the filaments are severed to allow flow
Which actin modifying processes are involved in filopodia formation
elongation
bundling
actin assembly
Which actin modifying processes are involved in lamellae formation
Assembly Elongation Capping Branching Severing
Signalling mechanisms that regulate actin cytoskeleton
- Ion flux changes (i.e. intracellular calcium)
- Phosphoinositide signalling (phospholipid binding)
- Kinases/phosphatases (phosphorylation cytoskeletal proteins)
- Signalling cascades via small GTPases
What GTPase subfamily regulates the actin cytoskeleton
Rho subfamily
What 3 things activate the Rho subfamily
receptor tyrosine kinase, adhesion receptors (integrins cadherins) and signal transduction pathways
Which small GTPase causes lamellipodia
Rac
What do stress fibres do
Contractile fibres
Which small GTPase causes filopodia
Cdc42
Which small GTPase causes stress fibres
Rho
What does activation of Cdc42 cause the formation of
Filopodia
What does activation of Rho cause the formation of
Stress fibres
What does activation of Rac cause the formation of
Lamellipodia