Kinases and Cancer Flashcards
what are the differences between conventional and modern cancer treatments
conventional - targets generic properties such as rapid proliferation
modern - targeting specific proteins/receptors - such as monoclonal antibodies
what occurs from paracrine ErbB stimulation
ERB ligands are released from stromal cells
what occurs from autokrin ErbB stimulation
activates metalloproteinases - cleaves pro-ERBB ligands
what is the basis and idea behind EGF/ErbB receptor and kinase receptor intervention
ErbB receptors are dysregulated in wide range of cancers
1 - inhibit dimerisation of EGF/ErbB receptors to suppress proliferation
2 - inhibit kinase activity via small molecule tyrosine kinase domain inhibitors
what is the mechanism of trastuzumab (herceptin) on Erb2
binds to the juxtamembrane region of Erb2 - inhibits proteolytic cleavage of Erb2 ectodomain
this is antibody-dependent cellular cytotoxicity
what is the mechanism of action of pertuzumab on Erb2
binds directly to the Erb2 dimerisation arm
blocks both dimerisation and activation
what is the mechanism of action of cetuximab (erbitux) on EGFR
competes with ligand for binding to EGFR
uses a dual mechanism:
- blocks the binding site on EGFR domain III
- steric inhibition of active EGFR conformaiton
what is the mechanism of matuzumab on EGFR
does not compete for binding but reduces affinity of EGF for EGFR - in matuzumab presence EGF can only contact EGFR domain III - reducing affinity
interferes with formation of active EGFR
what is the overall structure of kinases
N lobe and C lobe - hinge region in between
ATP binding site is located in the cleft between the lobes
N- lobe - 5 beta-pleated sheets and 1 alpha-helix
C lobe - mainly alpha helical
what are the residues important for catalysis in kinases
present on both lobes
N lobe:
P-loop (glycine rich)
beta-strand 3
alpha-helix C
C lobe:
beta-strands 6/7
A-loop (activation loop)
what is difference between an activated/inactive A-loop
inactive - tyrosine residues are unphosphorylated
active - tyrosine residues are phosphorylated
A-loop acts as a pseudo substrate
what does chronic myelogenous leukemias (CML) effect
early haematopoetic stem cells
what are the two phases of CML
acute - significant increase in immature white blood cells
chronic - elevated number of mature white blood cells
what causes CML
reciprocal translocation between chromosome 9 and 22
what are the key regulatory domains for Abl regulation and their functions
SH3 - poly-proline binding domain
SH2 - phosphotyrosine recognition domain
what are some of the features of Abl
Abl knockout in mice is lethal
ABL shuttles between the nucleus and the cytosol - in response to ECM adhesion
features of the basal state of ABL and what maintains it
basal state - low phosphorylation activity, in an off state
maintained by:
cis - self interactions
trans - interactions with range of targets
what are the essential features of maintaining the auto inhibited state of ABL
association of SH3 with its N-lobe
insertion of myristol group in the C-lobe
outline partial activation of ABL
1 - unlatching - removal of myristyl group from C-lobe leads to partial activation
2 - unclamping - displacement of SH3 from N-lobe
how is full activation of ABL achieved
switching - phosphorylation of tyr-412 on the activation loop and tyr-245 in the SH2 kinase linker
how is cis/trans activation of ABL regulated
inhibitor and activator proteins
how does ABL lead to cell survival
in response to growth factors concomitant with cytosolic localisation
how can ABL lead to cell death
in response to DNA damage and oxidation concomitant with nuclear accumulation
what odes the lack of SH3 domain of GAG-ABL indicate
suggests that the lack of SH3 - N lobe interaction leads to constitutive activity
