Cell Cycle 7 Flashcards
What is the viral mutant of EGFR called?
v-ErB2
What is altered in the viral mutant of Akt?
It is constitutively bound at the plasma membrane.
What growth factor was identified in the media of cancer cells?
TGFB
What antibody blocked the binding of TGFB?
c225
What did Cohen discover and how?
EGF - injected new born mouse saliva into eyes and found that they opened earlier.
How many disulphide bonds are there in EGF?
3
What does EGF bind?
EGFR
When EGF binds EGFR, what happens to the receptor?
It dimerises and undergoes trans-auto-phosphorylation.
Which two proteins bind to phosphorylated tyrosines on EGFR?
Grb2 and PI3K via SH2 domains
What binding domains does Grb2 have?
One SH2 domain and two SH3 domains either side
What does Grb2 bind via its SH3 domains?
Binds two proline rich sequences in Sos
What is the function of Sos when at PM?
It catalyses the nucleotide exchange for Ras protein.
What groups allow Ras to attached to the PM?
Farnesyl groups
What pathway is downstream of activated Ras?
MAP kinase pathway
How does Ras activate Raf?
Allosterically
What does Raf phosphorylate? and what does this cause?
Mek, which in turns phosphorylates Erk
What does Erk do?
Phosphorylates the TFs jun and fos - these activate the expression of cyclin D.
What does PI3K phosphorylate?
The inositol head group of lipids, on position 3 - to give PIP3
What is recruited by PIP3 and via what domain?
PDK1 and Akt - have PH domains which bind to PIP3.
What is a PH domain made up of?
Many beta strands and one alpha helix - the loop between provides specificity.
What type of kinases are PDK1 and Akt?
Serine/Threonine kinases
Is PDK1 constitutively active?
Yes
What does recruiting of PDK1 and Akt to PM allow?
Allows for phosphorylation on T308 of Akt by PDK1, activating it.
What are the 4 downstream effects of Akt?
- Phosphorylates GSK3 on Ser9, this prevents inhibition of cyclins.
- Phosphorylation of FOXO (TF), causing nuclear export and preventing expression of p27.
- Phosphorylation of p27 - nuclear export
- Phosphorylation of p21, causing degradation.
What does PTEN do?
It is a phosphatase that removes phosphorylation from inositol head groups. This prevents Akt and PDK1 binding.
Is PTEN a tumour supressor?
Yes
Give the name of the drug that prevents farnesylation of Ras.
Farnesyltransferase inhibitors - prevent membrane localisation of Ras.
What drug targets the V600E mutation in constitutively Raf?
PLX4032
