Growth Factors + EGF Flashcards
What do growth factors do?
regulate cellular processes such as proliferation, differentiation and maturation
What are cytokines
Cytokines are growth factors of blood cells:
hematopoiesis and immune cell differentiation
Explain why the definition of a cytokine ands growth hormones don’t always fit
Cytokines can affect cells other than blood cells
Cytokines may lead to growth, but they might also
induce apoptosis (neutral definition)
Growth factors and cytokines are proteins, but we also know steroid growth hormones (don’t need proteins)
Explain where EGF comes from/how it gets released
GPCR recieves saignal e.g. Ach
Causes conformational change in the GPCR that causes signal to be sent to a different membrane protein (either ADAM or MMP)
Causes cleavage of membrane proteins to release EGF
EGF then binds to an EGFR and causes the MAPK cascade
explain simply the specificity of GH binding to GHR
Limited number of AAs recognised
If change them, change Kd and therefore output
does the same signalling molecule do the same thing in every cell
NO
What is the most widely used technique to study drug binding
SPR - Surface plasmin resonance
Explain how SPR works
Uses bait and prey molecules
ligand binding (association) and then wash buffer over (dissociation)
takes minutes
Interested in rate ligand falls off
Bait is attached to gold film by a flexible tether
Incident loght shined and the reflected light angle is detected by a detector, angle changes depending in what is attched
Explain immediate early gene expression in cell cycle control
MAP kinase cascade leads to immediate early gene expression
Make TFs, new proteins that control cell cycle: cyclins and CDKs controlled by Myc
Myc leads to a delayed response gene expression, important in call cycle regulation
After we have delated response, then G1-CDK can become active
Explain the cyclin/cdk partner occurring at different cell cycle stages
G1: Cyclin D/Cdk4/6
G1/S: Cyclin E/Cdk2
S: Cyclin A/Cdk2/1
M: Cyclin B/Cdk1
Explain kinase/cdk activation
Wee1 deactivates CDK by phosphorylation on tyrosine 15
CAK can activate CDK by phosphorylation on threonine 161 (even when this happens, still inactive as phosphorylation of Y15 still there, needs Cdc25)
Cdc25 activates CDK by dephosphorylation on tyrosine 15 (M checkpoint?)
Explain how cyclin A/Cdk2 goes from low to high activity
Phosphorylation of Thr160 on the T loop of CDK2
Explain steps of the cell cycle using CDKs
SEE PHOTO
What is Nef
Viral protein
Inihibits progression from Ras to Raf
Found in HIV – promotes viral replication
Explain p53 in the DNA damage checkpoint
normal conditions:
p53 is attached to Mdm2 and ubiquitinated and therefore degraded
When DNA damage occurs - kinase cascade leads to phosphorylation of p53 and releade of Mdm2 - p53 now active
P53 is a TF, and attaches to p21 gene
P21 is then transcribed - it regulates cdks, it is an inhibitor
When transcribed the p21 protein is produced - cdk inhibator (clamps over cyclin/cdk) and so stops cell cycle progression
features of EGF
Epidermal growth factor
- about 40 residues:
- 3 disulphide bonds.
- two-stranded beta-sheet followed by a loop to a C-terminal short two-stranded sheet.
- Subdomains (between the conserved cysteines) vary in length
What does cbEGF stand for
Calcium bindinhg EGF
Features of cbEGF
Often as tandem repeat
Main building block for fibrillin
Explain the domain organisation of Fibrillin
Ca2+ binding EGFs – about 37
Also other domains – TB domain
A few EGFs that are non-calcium binding
Hybrid domains (2)
at the N terminus theres a unique region
Also a proline rich region
function of fibrillin
Forms microfibrils (8 fibrillins) - part of the ECM
Diseases caused by fibrillin mutations
500 mutations - all associated with a class of diseases called Marfan synrdome
Mild - Tall + lanky
Severe - Cardiovascular problems, vision problems, lethal at development stage
What to EMs show about microfibrils?
show elongated ‘beaded’ structures
What techniques can/cant be used to see microfibril structure
EM (doesnt show much though)
NOT - CryoEM, Crystallisation as fibril is too complex in structure
only option is to ‘dissect and conquer’
two microfibril models
- antiparallel staggered conformation – fibrillins layed out partially overlapping generating a repetitive pattern with a 50nm register
- “Jack knife” model – Fibrillin arranged in a jack knife conformation and then these are arranged on top of each other – there is growing evidence that this is the correct model
-Generation of elongated structures from domain building blocks
-domain junctions potential hinge regions
