Cell Death Flashcards
How does cell cycle arrest occur?
DNA Damage results in p53 phosphorylation
• p53 stimulates transcription of p21(Cdk inhibitor protein)
• Results in cell cycle arrest.
• Under normal conditions p53 is degraded so the cell cycle can proceed.
What is caused by overexpression of Myc?
Our cells prevent cancer by inhibiting Mdm2, leading to the production of active p53. • p53 causes cell cycle arrest or cell death (apoptosis).
What is the difference between mitosis and meiosis?
Mitosis happens in somatic cells, same number of chromosomes as starting cell (diploid) Needed for growth and repair.
Meiosis occurs in germ cells, Half # chromosomes as starting cell (haploid) • Needed for sexual reproduction
Describe how homologous pairs line up and separate in meiosis
They line up on the spindle and separate and anaphase 1, sister chromatids separate at anaphase 2.
Mitosis - duplicated chromosomes line up individually
How to kinetochores on sister chromatids attach in mitosis and meiosis?
Mitosis - they’re attached to diffrent poles. Meiosis - attached to same pole.
What are the types of cell death?
Programmed - cells kill themselves in a controlled way, necrosis - cells swell and burst in response to insult.
Cell death can occur to help development.
Describe apoptosis -
One type of programmed cell death.
Depends on cascade of degradation enzymes called caspases.
Cytoskeleton disassembly, breakdown of nuclear envelope, and DNA is cleaved. •
Describe caspase activation during apoptosis -
caspases are activated by cleavage to cause apoptosis. Activation of initiator caspase by apoptotic signal causes executioner caspase to be activated by cleavage, leading to apoptosis.
Describe the extrinsic pathway of apoptosis -
activated by a signal from outside target cell, fas ligand binds to fas death receptor, causing DISC to assemble. Cleavage and activation of caspase 8 occurs, activating executioner caspases and leading to apoptosis.
Describe the intrinsic pathway of apoptosis -
activated by a signal from inside the target cell, release of cytochrome c in intermembrane space, activating Apaf1,
CARD domains come together assembling apoptosome, caspase 9 recruited and activated, executioner caspases activated, leading to apoptosis.
Describe anti-apoptotic bcl2 proteins -
maintains membrane integrity, keeps cytochrome c in cell, bax/back is inactive.
What happens when BH3 only protein is activated by apoptotic stimulus?
anti apoptotic Bcl2 protein turneed off, BaxBak protein activated, come together to let cytochrome c move out.
Describe inhibitors of apoptosis -
Bind and inhibit activated caspases • Anti-IAPs prevent IAPs from binding caspases.
How do Anti-IAPs work?
They are released to prevent IAPs from interfering with apoptosis.
What survival factors inhibit apoptosis?
increased production of anti-apoptotic Bcl2 protein, inactivation of pro apoptotic BH3 only protein, inactivation of anti IAPs
