Cell motility and migration Flashcards
1
Q
What is the function of cell motility?
A
- wound healing
- chemotaxis
- development
2
Q
What controls cell motility and migration?
A
- RHO GTPases
- GAP = GTPase activating factor
- GEF = GTPase exchange factor
- GDI = GTPase dissociation inhibitor
- describe process of RHO GTPases*
3
Q
How do we know that small GTPases are regulated by G-proteins?
A
- use starved fibroblasts
- add serum to cells results in fibroblasts creating actin filaments
4
Q
What is the actin tread-milling cycle?
A
- start with one monomeric actin, globular actin - g-actin
- form actin filaments - f-actin
- filament branching
- 2 filaments can br brought together = contraction (stress fibres) - done by myosin II
5
Q
What is required for contraction?
A
- MLC - myosin light chain
- MLCK - myosin light chain kinase phosphorylates 2 actin filaments
- MP - myosin phosphatase can remove phosphate group
6
Q
What is the role of RHO?
A
- RHO binds GTP = RHO-GTP
- activates 2 proteins - one = diaphanous (protein which responds to actin assembly)
Cof. (cofilin) can remove actin filaments - second protein = ROCK, which phosphorylates LIMK = produced Cofilin (Actin stabilisation)
7
Q
What is the function of ROCK?
A
- ROCK can phosphorylate MP
- MP cannot dephosphorylate MLC
- causes contraction
8
Q
What is the function of RAC and CDC42-GTP
A
- regulate actin polymerisation
- CDC42 promotes branching by activating ARP2/3 (bind to one filament of actin, promotes new formation of actin)
- RAC - promotes actin stabilisation
- prevent actin disassembly
9
Q
During motility, what is expressed at either ends of the cell?
A
- at the leading edge = CDC42 and RAC
- Rho at the tail (forms new actin filaments = contraction and detachment of tail)
- ruffles at front
10
Q
How does RHO GTPase regulate microtubules?
A
- RHO - diaphanous = stabilisation
- RAC - p65PAK = elongation
- CDC42 - Par6/PKCdelta = elongation
11
Q
What pathways are the GTPases involved in ?
A
- RHOA - leads to dec p21 and p27
- CDC42 - activates JNK/p38 - AP1 = inc cyclin D
- RAC - activated superoxides - NK-Kb = inc cyclin D (cell cycle expression)
12
Q
How are Rho proteins involved in tumourigenesis?
A
- activated RHO, RAC and CDC42 are transforming
- inactivation of RHO, RAC and CDC42 prevent transformation
- RHO-GEFs - have been isolated in transformation screens and found in translocations
- RHOA - overexpressed in colon, breast and lung carcinomas
- RHOC - overexpressed in breast and pancreatic cancers
- RAC1 and CDC42- overexpressed in breast cancer
- EGF, HGF, LPA = growth factor in tumour environment that activate RHO
13
Q
What controls cell polarity?
A
- RHOA, RAC1 and CDC42
14
Q
What happens if polarity is lost?
A
loss of polarity = RAC1, RHOA not working
- multilayering by RHOE start EMT
- forming benign tumour
15
Q
How are invasive tumour caused?
A
- loss of cell junctions - RAC1, RHOA, ROCK stop working
- increased motility by RHOA, ROCK, RAC1
- protease expression = RHOA, RAC1 in the basal membrane
