Cell Death

Question 1

Why does type of cell death matter?

Answer 1

• different triggers for each
• different consequences for the cell/ tissue after death for disease progression/ medicines
• necrosis vs apoptosis

Question 2

apoptosis 5 general characteristics ( swell? compaction? initation? passive/active? inflammatory?)

Answer 2

1) cell shrinks; DNA fragments in 200bp ladder
2) compaction of chromatin; apoptotic body forms
3) imitated by signal transduction
4) active process; requires macromolecule synthesis
5) DOES NOT cause inflammation (can be anti-inflammatory)

is a PROCESS like cell cycle

Question 3

Necrosis 5 key characteristics? (swell? compaction? initation? passive/active? inflammatory?)

Answer 3

1) cell swelling & DNA fragments random (smear on gel)
2) no chromatin compaction or apoptotic body formation
3) initiated by direct cell damage
4) passive process= no macromolecule synthesis
5) cause inflammation

Question 4

why does DNA have 200bp ladder in apoptosis?

Answer 4

-because it is the distance between the 2 histones

Question 5

why does swelling happen in necrosis?

Answer 5

-is passive has no energy & maintaining correct cell plumbness requires energy

Question 6

nomenclature committee on Cell Death (NCDD)?

Answer 6

1) address related to nomenclature of cell death based on morphological grounds
2) define major cell death on functional basis
3) distinguish essential (causal) vs accessory (correlative) aspects of death process
4) ID consensus criteria for identification of dead cells w/ permeable PM or complete cell fragmentation

Question 7

two types of apoptosis?

Answer 7

1) intrinsic pathway
2) extrinsic pathway

both w/ specific cascade, both lead to apoptotic bodies w/ membrane blabbing
-both have executioner & initiator caspases

Question 8

apoptosis

Answer 8

• programmed cell death
• orderly cell self destruction
• this process is as crucial for survival of multi-cellular organisms as cell division

Question 9

sequence of apoptosis? (x7)

Answer 9

1) enzymes break down cell cytoplasm
2) cytoplasm becomes dense (shrinks)
3) organelles tightly packed
4) cell surface membrane changes, bleb forms
5) chromatin condenses, nuclear envelope breaks
6) cell breaks into vesicles
7) phagocytosis

Question 10

cell fragments of apoptosis?

Answer 10

• are produced with intact Plasma membrane containing organelles
• are ingested/digested by phagocytic cells

Question 11

cell fragments of necrosis?

Answer 11

• DO NOT produce blebs w/ intact memrbane

- shit is just falling apart, external parts of cell are now outside it (key part!)

Question 12

what eats apoptosis vesicles?

Answer 12

• WBC (phagocytes)
• see the plasma membrane and no internal cell parts so calmly disposes of the vesicles
• necrosis WBC in panic because see internal cell organs floating around

Question 13

what causes apoptosis?

Answer 13

1) normal physiological processes
- healthy & helps us adapt to cell damage we may have
2) pathological processes

Question 14

Physiological processes that require apoptosis? (x)

Answer 14

1) embryo/fetal development
2) hormone dependent involution
3) cell loss in proliferating cell populations
4) elimination of self-reactive lymphocytes
5) death of cells that have served their function

Question 15

What is hormone dependent involution?

Answer 15

-ex: regression/ stopping of lactation of breast after weening

Question 16

Apoptosis & death of cells that have served their function ?

Answer 16

-lymphocytes are hugely activated (in response to pathogen) but no way to deactivate them except to do apoptosis

Question 17

Apoptosis & elimination of self-reactive lymphocytes ?

Answer 17

• in B & T cells, test to see if they are potentially self reative, if ARE we do apoptoiss.
• If apotptosis doesn’t work then we are at risk for autoimmune disease

Question 18

Apoptosis in embryo/fetal development?

Answer 18

• frequently make temporary structure in fetal development to get cells from one place to next
  
  • start w/ webbed hands
• incorrect/failure leads to morpholigcal birth defects

Question 19

pathological reasons for apoptosis? (4)

Answer 19

1) DNA damage due to radiation/chemo
2) accumulation of misfolded proteins–>ER stress–> apoptosis
3) host immune response to virally infected cells
4) organ atrophy after duct obstruction

Question 20

Viral infections & apoptosis?

Answer 20

• viruses don’t want apoptosis, want cells to stay alive & divide so our host cells are virus factories
• we defend ourselves by killing cells, turning off pathogen factories

Question 21

caspases?

Answer 21

• apoptosis entirely dependent on their presence
• look for actviated caspapses to see if tissue in apotptosis or necrosis
• mutations cause inability to do apoptosis
• are in PRO-FORM

Question 22

Apoptosis step 1

Answer 22

activation of initiator caspases by cleavage of pro-caspase

Question 23

Caspase initation?

Answer 23

• caspases exist in pro-form, must be activated to begin apoptosis by cleavage of the pro-caspase
• pro-caspase portion of caspase have no function other than prevent caspase dimerization and activation

Question 24

Apoptosis step 2?

Answer 24

• initiator caspases activate executioner caspases
• AMPLIFICATION STEP
• 1 active caspase activates a TON of executioner caspases

-need this because a lot of work has to be done to prepare cell for apoptosis

Question 25

apoptosis step 3?

Answer 25

- executioner caspases cleave cell proteins, condense & pack chromosomes and cytoplasm, cleave nuclear lamina

Question 26

extrinsic pathway of apoptosis? (x6)

Answer 26

1) cells have Fas death receptor on surface 2) killer lymphocyte w/ death signal binds Fas receptor 3) pro-caspase binds Fas receptor (both inactive) 4) Killer lymphocyte w/ Fas ligand binds, forms DISC complex 5) DISC activate caspases 8 or 10 via pro form cleavage 6) initiator caspases activate executioner caspases--> apoptosis

Question 27

expression of fas death receptor on cell membrane?

Answer 27

DOES NOT cause apoptosis, just means is capable of listening to external death signal

Question 28

do all cells express fas death receptor?

Answer 28

- some always do; some only express in distress, - one way cells differnetiate between being prone/not prone to apoptosis - MOST CASES have Fas receptor; NO fas ligand - only when fas ligand binds receptor, does disc complex get made

Question 29

intrinsic apoptosis pathway?

Answer 29

1) stressful event occurs, mito disfunctions & releases Cytochrome C into cytoplasm 2) Cytochrome C binds molecules, forms APOPTOSOME 3) apoptosome recruits caspases, forms INFLAMASOME 4) inflamasome activates initiator caspase 9, 5) caspase 9 activates executioner caspases--> apoptosis

Question 30

Are all molecules that form inflamasome always in the cell?

Answer 30

- depends on how prone cell is to apotptosis, some cells the molecules have to be induced (slow apoptosis requrie txn/trans to make moelcules; like neurons) others will always be present (fast apoptosis like lympphocytes) - earlier molecules typically trend/trans and ready to go, later molecules haven't yet

Question 31

GSK?

Answer 31

- ex of molecule that has different regulatory consequences on the intrinsic & extrinsic pathways - can cause excessive cell death (neurodegenerative disease; or deficient apoptosis (cancer) *is the SAME GSK-3 either way*

Question 32

Intrinsic pathway and GSK-3?

Answer 32

- GSK-3 exerts a PRO-APOPTOTIC role, acting on targets Bax, Bim, VDAC - helps in disintegration of mito. & release of cytochrome c

Question 33

Extrinsic pathway and GSK-3?

Answer 33

- anti-apoptotic, GSK-3 prevents DISC complex formation | - means that initiator caspases can't be activated, so executioner caspases aren't formed so no apoptosis

Question 34

BCL2, BH2, BH123?

Answer 34

``` BCL2= anti-apoototic ( all 4 domains) BH123 = ppro-apoptoic (3 domains) BH3-only= pro- apoptotic (1 domain) ```

Question 35

How BCL2 effect apoptosis? BH3 effect apoptosis?

Answer 35

- is anti-apoptotic, inhibits BH123 protein activation of intrinsic apoptosis pathway - BH=pro-apoptotic; inactivates BCL2 therefore allows BH123 to dimerize & activate intrinsic apoptosis pathway

Question 36

how do extracellular survival factors inhibit apoptosis?

Answer 36

1) by inducing expression of Bcl2 2) turning off expression of BH3-only proteins - which results in increased amounts of activated Bcl2