6 Flashcards
Akt can directly shut off —–, which “activates” the cell cycle
p27 (CKI’s)
PI3K and Ras can activate —— signaling?
MAPK (ERK)
Ga proteins activate RTKs and then PI3K but so can —— (directly)?
Gbg subunits
what are trophic factors?
Trophic factors are often proteins, that act as signals to promote cell survival, growth, and differentiation
- normal cells require trophic factors just to survive, if missing, a suicide program is initiated
Necrosis Vs Apoptosis
Necrosis:
- Injury
- inflammation
- usually many cells
Apoptosis:
- Cell suicide
- usually one cell
- DNA specific cleavages
- no Inflammation
Intrinsic pathway (APOP) is regulated by what family ?
Bcl - family
Pro-survival: Bcl-2,
Pro-apoptotic: Bax, Bak, BH3 (Bid, Bad)
Intrinsic pathway is also known as the?
mitochondrial pathway
The Extrinsic pathway is initiated by what?
receptors on the cell surface (death receptors)
- FasR
- TNFa
compare c.elegans and mammal apoptosis proteins
C. elegans:
- CED-9 (Bcl-2)
- CED-4 (Apaf-1)
- CED-3 (Caspase-9)
Mammals
- Bcl-2
- Cyto-c
- Apaf-1
- Caspase-9
- caspase- 3
what is the executioner in intrinsic apoptosis ?
Cleaved Caspase-3
What is the initiator caspase in the intrinsitc pathway?
Caspase-9
caspase in the extrinsic pathway ?
Caspase-8
What is Bid?
BH3 interacting death domain
- activated by casp-8
- binds Bax/Bad and forms pore
Extrinsic Apoptosis (STEPS)
- Binding of death ligands
(e.g., FasL, TNF-α) to death receptors (e.g., Fas, TNFR). - Death receptor recruits FADD → forms DISC → activates caspase-8.
- Caspase-8 directly activates caspase-3, -6, -7 → apoptosis.
** Cross-talk: Caspase-8 can activate Bid, linking to the intrinsic pathway.
Intrinsic Apoptosis (STEPS)
- Internal stress (e.g., DNA damage, oxidative stress, ER stress).
- Bcl-2 family proteins regulate cytochrome c release.
- Cytochrome c binds Apaf-1 → activates caspase-9.
- Caspase-9 activates caspase-3, -6, -7 →
apoptosis.
How does Caspase 3 become activated by Caspase 9?
Caspase-9 cleaves pro-caspase-3 at specific aspartate residues, removing inhibitory domains and converting it into its active form.
What leaks out of the mitochondria?
cytochrome c
Apaf-1 stands for?
Apoptosis protease activating factor
what forms the apoptosome ?
- cyto-c
- procaspase-9
- Apaf-1
what are ICAD’s ?
ICAD’s (Inhibitors of Cas-activated DNase) are chaperone proteins that binds and inhibits CAD to prevent premature DNA fragmentation.
What are CAD’s ?
CAD’s (Caspase-Activated DNase): A nuclease that degrades DNA into fragments during apoptosis.
what do Caspases stand for?
Cysteine-dependent, Aspartate-Directed Proteases
What is the TUNEL assay used for?
TUNNEL ASSAY detects DNA fragmentation in apoptotic cells.
Works by labeling free 3’-OH ends of fragmented DNA (caused by Caspase-3) with fluorescent or colorimetric tags.
Key enzyme: TdT
Apoptotic cells appear fluorescent
what is Etoposide?
chemotherapeutic agent
- Etoposide is a DNA adduct and works on Topoisomerase II
- induces apoptosis
What is Staurosporine? and Why is it not used in Humans?
Non-Specific Action: It inhibits multiple protein kinases (broad-spectrum inhibitor), leading to widespread effects beyond apoptosis.
- not a chemotherapeutic agent
