CAMS Flashcards
What are some examples of how adhesion is important
Adhesion of sperm to oocyte.
Cells in the morula undergo compaction using E cadherins to stick closely together.
Cells split into the inner cell mass and the trophoblast due to their differences in adhesion properties.
Implantation of the oocyte into the endometrium requires adhesion.
What are L cells
How can you use them to show homopholic sorting
They don’t express any cadherins and so they don’t aggregate.
You can transfer them with transgenes for different cadherins and then monitor their behaviour.
One group of cells with E cadherins and the other group with N cadherins. The cells will aggregate with eachother and and those with E go into the middle and those with N surround them. This is called homophilic sorting.
One group of cells with high levels of E cadherin and another group of cells with low levels of E cadherin.
The cells aggregate with eachother and sort into two groups.
The high E cadherin cells go into the middle and the low ones surround them.
Cadherins structure
Hinge regions
Have transmembrane domains and their extra cellular domain interacts with things at the N terminal.
Ca binds to the hinge regions on the extra cellular domain to stabilise them so they are not floppy.
This means cells can modulate how much adhesion they do by changing the Ca levels to allow cadherins to work better.
More Ca means more adhesion.
How are cadherins localised on the cell membrane
What is the first cadherin expresses in embryos
They all line up on the cell membrane.
The arrays on one cell will be perpendicular to the lines of arrays on the cells it binds to.
E cadherin
Where are cadherins normally expressed
In adherins junctions
Classical vs non classical cadherins
Examples
Structure
Classical - E, N, P, VE
Non- cadherin 23
Classical have a single transmembrane domain and then repeated hinge domains on the extracellular.
Non classical have varied structures with multiple transmembrane domains or kinase domains
Where are protocadherins found
NS
How did the many types of protocadherins occur and what do they do
Alternative splicing of the gene can give rise to various isoforms.
They play a role in specifying synapses in the brain allowing for complex connectivity.
What do catenins do ?
What happens when a cell is not using its cadherins compared to when it is
Bind to the intercellular domain of cadherins.
They link the cadherins to the cells cytoskeleton actin filaments.
The alpha catenin is in a folded state.
When a cell is interacting with another cell it creates tension and causes the catenin to go into an extended state.
This reveals a binding site for vinculin which binds to actin.
What does rho activation do
Leads to stress fibre formation where the actin filaments organise into parallel fibres.
What cadherins do newly formed mesoderm cells lose
What replaces E cadherin in the neural tube
Where is cadherin 6B expressed
What do neural crest cells express
E cadherin so they can migrate inside.
N cadherin.
In the floor and roof plate.
Cadherin 7
What is the structure of selectins and what do they bind to
What do they do
What is on their extra cellular domain and intracellular domain
Cell surface protein with a single transmembrane domain which is Ca dependant and binds to carbohydrates on neighbouring cells.
They are used in the immune system for neutrophil trapping.
EGF like domain and a lectin domain on the end of their extracellular domains.
Their intracellular domains are anchored to actin.
When are selectins induced
During inflammation in endothelial cells when white blood cells become adherent to the wall of the vessel and roll along it.
Once the cells stop rolling they leave the vessels going between cells using integrines.
Ca independent CAMS
WTF
Some are secreted and others are transmembrane.
Their extra cellular domains have many ig and fibronectin repeat domains.
There is one gene they all arise from the undergoes alternative splicing and post translational glycolysation.
What is the ECM made up of
Fibronectin, laminin, collagen and elastin which are all large secreted proteins.
What is laminins structure
It is a trimer.
It has integrity interacting domains and self assembly branches.
It has a coil coiled domain.
Integrins structure
What is on each domain
How may types of each subunit are there
They form heterodimers and each monomer has a single transmembrane domain.
They have cystine rich extracellular domains to interact with other extra cellular components.
At the end of the extra cellular domain they have a matrix binding domain which interacts with the ECM.
The intracellular domain is anchored to actin filaments using talin and vinculin.
There are 18 types of alpha subunit and eight types of beta making 24 variations.
How are integrins activated
What do they look like when active and inactive
Binding intra or extracellular. Inside out activation or outside in.
Inactive has a folded extracellular domain.
How is focal adhesion kinase activated
When integrins binds to the ECM it is activated.
It will phosphorylate tyrosine and cause actin polymerisation.
It will recycle focal adhesions to enable migration and acts in attachment dependant cell death.
How do cells migrate and what does the cell look like
How do they sense cues
Lamellipodia extend at the leading edge and attach to the substratum by focal adhesions.
New adhesions are made at the front and old ones are removed from the back.
Actin polymerisation pushes the membrane out. The cell is polarised.
To sense guidance cues the lamellipodia ruffle
What is cytochlasin B
It is used to study actin polymerisation
It lands on the plus end of the filament and blocks further adding of the actin.
This stops migration and actin starts to disassemble.
How does the arp 2/3 complex work
What activates it
Nucleates actin.
It binds to the minus end of the filament and monomers are added to the plus end.
Arp 2 and 3 have a similar structure to actin and this is why they are able to nucleate.
Another filmament extends at 70 to the original one. This gives stability.
RAC activates it
What two things treadmill during migration
Actin - as you grow fibres at the leading edge you take them away from the minus end.
Focal adhesion treadmills.
