L23 - Cell Motility Flashcards
What is the ECM made up from
Many components including firbronectin, laminin, collagen and elastin
Is fibronectin membrane bound?
No is a secreted molecules
How many domains does fibronectin contain - what is the function of these
Many domains, one domain binds heparin
Describe the structure of laminin
Trimer
What does laminin interact with at its Cā terminal end
Integrins, dystroglycans, perelecans
Describe what may increase integrin binding to the ECM
Intracellular signsls
Integrins forms
Heterodimers
Each monomer of the integrin heterodimer contains
One single transmembrane domain
What sort of bonds are found in the a subunit of integrin - where do these bonds form
Disulphide bonds - cytenine rich doamins
The N terminal of integrins is capable of binding
Divalent cations
What are the two itnegrin subints
a and B
What does integrin connect to inside of the cell - what mediates this
Binds actin filaments which is mediated by tali and vinculin
How many a integrin types
18
How many b integrin subtypes
8
How many total variatns can the different a and b integrin subunits form
24 variants
Describe the structure of inactive integrin
EC domain is folded up into its inactive state
When the EC domain of integrin bind s to the ECM describe what happens
Induction of confirmational changes which causes activation of the IC domain this is outside in activation
Desribe inside out activation of integrins
Activation of the IC domain through IC signalling - interaction with talin causing the activation of the EC domain
What is FAK
Focal adhesion kinase
Describe how FAK is activated
Intregrin binding to the ECM causes phosphorylation and activation of FAK
Describe the FAK pathway
Fibroncectin interacts with integrin - activates FAK - Phosphorylation of tyrosines in that region of focal adhesion - polymerisation of actin fibres
What is Fak involved in
The recycling of focal adhesions to enable migration - acts a timer for the adhesion
If certain cell types are not adhered to their substrate describe what happens
Cell death follows this is mediated throguh focal adhesion kinases
What is the name of the process of cell death which occurs when attachement to the substrate is lost
Anoikis
Mammalian cell motility is mostly based on which molecule
Actin based
What are excluded from the region where actin filaments push through
Microtubules and intermediate filaments
Ruffling is dependent on what and allows the sensing of
Actin and allows the sensing of guidance cues
Myosin II assists in the
Retraction of the tail
The lamellipodium extends in direction
Of migration
What does the cortex aid
Membrane tension
What is added at the leading edge
Actin fibres
Tension is transmitted via the
Cortex
How is the cell highly polarised during migration
Different things are happening at either of the ends
What is the action of cytochalasin B
Lands on + ends of the actin and prevents any further elongation
Once actin is capped what begins to be seen
Actin filaments begin to depolymerise
What activateds the ARP complex
Rax kinase
What is the function of the ARP complex
Nucleation of actin monomrs to form filaments
How does ARP2/3 aid in actin nucelation
Both resemble actin so aid nucleation in this way
Actin branches from at what angle
70
Describe how branch formation aids in the movement of the cell
Branches are forming to push the leading edge forward
What happens to actin at the - end? What must then happen to it
Actin depolymerises - must be transported back to the leading edge so that they can be assemble
When the rear edge is moving forward - what must happen to interactions
They are broken
Focal contacts are
Turned over
What have roles in the maturation of focal adhesions
Actin binding proteins, small G-proteins, myosins
Low density adhestions are
Very sparse
Low density adhesions require
Rac1 and cdc42
High density adhesions require
RhoA and actin-myosin interaction
Describe the mobility of low density adhesions
Immobile
Descirbe the mobility of high density adhesions
Slide in the membrane
Example of a soluble molecules as a signal for motility
Netrins
How can fibronectin be a signal for migrating cells
Specific forms of fibronecctin can be laid down which other cells are then able to follow
Describe the affect of using antibodies to fibronectin
Inhibits migration as interaction with fibronectin is no longer possible
Which motif does fibronectin recongise and bind to
Arg Gly, Asp
What is the Arg, Gly, Asp motif also known as
RGD
What is the effect of injection of an RGD motif
Inhibits migration since fibronectin binding sites are swamped out and binding no longer possible
Exocytosis occurs where
At the leading end
Where does endocytosis occur
Arround the cell
Overall is there a net membrane addition or removal
Addition
If membrane is fixed by focal contacts and membrane cycling is occuring what is the effect of this on the cell
Cell is able to move forward
What are the roles (4) of endocytosis in motility
Shaping chemotactic gradients: Confining signalling: Modulation of adhesion contacts and ECM: Polarisation of endocytosis
How is adhesion removed
Receptor pulled out of the membrane
