EGFR Signalling Flashcards
What are the 4 domains of the EGF receptor?
What are the 2 features of the extracellular domain?
What does the transmembrane domain induce?
What are the 3 functions of EGFR?
What are the 2 structural points of the EGF ligand?
What are 3 other ligands for EGFR?
Which Erb (1-4) does not signal the traditional way and why?
Ligand binding/extracellular, kinase, transmembrane, C-terminal tail
Highly glycosylated & disulphide bonds (oxidising environment)
Hydrophobic helix
Cell proliferation, differentiation & regulating differentiated functions
1 polypeptide that wraps into compact structure, 6 cysteine residues & disulphide bond formation
TGFa, HB-EGF & other growth factors
Erb-2 doesn’t have any major ligands, Erb-3 doesn’t have a functional kinase domain
What are the 3 steps of EGFR activation?
What happens to the kinase activity of EGFR when the C-tail is phosphorylated?
What happens to the kinase activity of EGFR when other proteins are phosphorylated?
How would you describe the EGFR?
How do the following interact with EGFR:
- SH2 domains
- SH3 domains
- Adaptor proteins
- Clathrin
- EGF binds & allows for receptor dimerisation
- 2 kinase domains are in close proximity in a dimer but their activation loops are not good consensus sequences for receptor tyrosine kinase
- Phosphorylation of tyrosine kinase due to length of time & close proximity in activation loops, C-terminus & membrane region
Removes inhibition & conformational change such that there’s more binding sites for proteins so activity increases
Proteins dock onto intracellular domain resulting in increased activity
Master docking site due to its many phosphorylated tyrosines
- pY
- proline-rich motifs
- SH2 domains
- by AP2 complex & internalisation of receptor
In 4 steps, how does the EGFR pathway regulate survival via the PI3K pathway?
In 7 steps, how does the EGFR pathway regulation proliferation via the MAPK pathway?
- EGFR phosphorylated at pY which PI3K binds to it via its SH2 domains
- PI3K activated
- PI3K phosphorylates/activates Akt/PKB
- Akt activates intermediates leading to the expression of pro-survival genes in the nucleus
br
- Grb2 binds Sos & has SH2 domains recognising pY on active EGF
- GAPs have SH2 recognising pY on active EGF
- Can go towards GTP & GDP form of Ras - both agonistic & antagonistic mechanisms
- Ras-GTP leads to activation of Raf
- Raf activates MEK1/2
- MEK1/2 activates MAPK
- Initiates transcription/gene expression for proliferation
How does EGFR activate the PI3K Pathway (via PDK1 and Akt?) 5 steps
How does PTEN regulate signalling in this pathway?
In 3 steps, how do GPCRs switch on the Matrix Metallo Pathway? MMP
In 2 steps, how do GPCRs activate PLCß & alter calcium levels?
- PI3K binds to the pY with its SH2 domains and phosphorylates lipids at their 3’ position to form PIP2 and PIP3
- PIP2 & PIP3 recruit proteins with PH domains
- The PH domains co-recruit PDK1 & Akt/PKB
- PDK1 phosphorylates Akt for activation and other kinases for downstream signalling
- Akt will phosphorylate other kinases for downstream signalling
Phosphatase that break down phospholipids to control strength & length of signalling
- MMP can interact with heparin-binding form of EGF
- MMP releases EGF of HB-EGF
- EGF can now activate receptors to switch on cascade via Ras & MAPK signalling leading to gene transcription
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- Calcium dependent kinases (Pyk2) activate Src
- Src phosphorylates EGFR to drive their activity as well
How do steroids induce gene transcription?
How does Src activate EGFR?
What does PKC do to EGFR?
What does EGFR signal transduction depend on? 2 things
Bind to steroid receptor & change gene transcription e.g genes for producing EGF
Phosphorylates tyrosine residues of EGFR via its SH2 domain for activation
Phosphorylates serine & threonine sites to inactivate GPCR
- Amount of time EGFR spends on cell surface
- Extent it is phosphorylated by PKC
What are the 3 ways in which EGFR signalling can be terminated?
How does over-expressed EGFR on the cell surface lead to cancer?
How can this be used to detect cancer?
What occurs in the DNA of C-erbB2 mutation of EGFR?
What happens to the signalling?
What occurs in the DNA of V-erbB mutation of EGFR?
Where is a similar structure of this seen?
- Dephosphorylation of EGFR by tyrosine phosphatases
- Negative feedback loop of phosphorylation by PKC at Thr654
- Endocytosis by clathrin coated pits/internalisation
More spontaneous dimerisation and more productive collisions leading to autophosphorylation and downstream signalling
Detect increased level of receptors on the cell surface is good indication
V to E point mutation in the transmembrane domain leading to transverse of pyrimidine to purine
It is increased
Ligand-binding domain is removed so it’s only transmembrane, kinase domain & C-terminus
In viruses to drive proliferation in host cells
What 5 types of genes are increased in expression due to de-regulation of EGFR signalling?
How do tyrosine kinase inhibitors down-regulate the EGFR signalling pathway?
What are two examples of these?
How do monoclonal antibodies down-regulate the EGFR signalling pathway?
What is an example of this?
How do anti-ligand mAbs down-regulate the EGFR signalling pathway?
What is an example of this?
What does mab and nib mean?
- Pro survival
- Metastasis (grow secondary tumours)
- Secretion of angiogenic factors - infiltrate tumours with blood vessels
- Proliferation/maturation (Ras)
- Resistance to chemo/radiotherapy
Bind to active sites of tyrosine kinase domains to compete at its ATP binding site to reduce activity
Gefitinib and ertolinib
Block receptors by binding to them
Herceptin mAb binds to HERP2 receptor seen in breast & colon cancers
Binds to EGF to prevent their binding to receptors
Cetuximab
Mab = monoclonal antibody
nib = small
