Apoptosis/DNA damage Flashcards
Programmed necrosis mechanism
Consumption of NAD+ through PARP-dependent modification –> ADP-ribose
- Leads to NAD+ depeltion and inhibition of glycolysis, no ATP so pump doesn’t work and sodium can’t leave cell, water rushes in and it bursts
IHC to detect apoptosis
best method, antibodies used for specific caspases
propidium iodide and cell sorting to detect apoptosis
PI intercalates DNA and is fluorescent
- DNA content analyzed using flow cytometry
< 2N have lost DNA content due to DNA fragmentation
Annexin V staining
PS found on outer leaflet during apoptosis, stain with antibodies
TUNEL
labeling nicks in DNA
extrinsic pathway ligands
TNFalpha
TRAIL
Fas
unique extrinsic caspase initiators
8, 10
caspase initiators for both intrinsic and extrinsic
2, 9
effector caspases
3, 6, 7
IAPs
IAP1, IAP2, XIAP, Livin
- inhibit effector and initiator caspases
Pro-death Bcl-2 proteins: effectors
BAK and BAX
Pro-death Bcl-2 proteins: BH3- only
BID, BIM, PUMA
BH-3 only activators
BID, BIM, PUMA
- bind and neutralize pro-survival Bcl-2 family members
- promote BAX and BAK oligomerization and pore formation –> cyt c release
BH3-only sensitizers
BAD, BIK, NOXA…. etc
BAX and BAK functions
oligomerize to form pore in mitochondria, release of cyt C
pro-survival Bcl-2 proteins
bind and sequester BAX and BAK
BID
extrinsic, activated in response to death receptors
BIM, PUMA
intrinsic,
BIM activated in response to MT stress
PUMA activated in response to p53
apoptosome
cyt C binds Apaf1, these then bind pro-caspase 9 to cleave and activate it, triggering caspase cascade
5 proteins released from mitochondria
- cyt c: forms apoptosome
- AIF: triggers chromatin condensation, DNA deg, disrupts ETC
- Smac/Diablo: inhibit IAPs
- Omi/HtrA2: inhibit IAPs
- Endo G: endonuclease that cleaves DNA
One of most common events to occur during oncogenesis
upregulation ofNF-kappa B activity: upregulates gene products that block apoptosis
damage by UVB
pyrimidine dimers
damage by UVA
free radicals
ionizing radiation/X rays
DS breaks in DNA strands or SS
polycyclic hydrocarbons
bulky adducts
direct DNA repairs uses…
MGMT
NER
fixes dimers and adducts