5-6, Apoptosis

Question 1

Default pathway ?

Answer 1

Apoptosis (cells require signals for cell survival, e.g. from cell-cell contact)

Question 2

Why apoptosis is important (4)

Answer 2

1. In development (sculpting structures)
2. Immune system shaping
3. Deleting damaged cells
4. Eliminating misplaced cells

Question 3

Morphological hallmarks of apoptosis (4)

Answer 3

1. Blebbing
2. Pyknosis
3. Nuclear fragmentation
4. DNA Fragmentation

Question 4

Intrinsic apoptosis

Answer 4

• activation of caspases
• due to permeabilisation of mitochondria,
• release of Cyt C (regulated by Bcl-2 fam)
• and formation of apoptosome

Question 5

Extrinsic apoptosis

Answer 5

• ligand activated death receptors form trimeric complexes,
• = formation of DISC
• = activation of caspase 8

Question 6

Apoptotic blebbing

Answer 6

side scatter in flow cytometry shows granularity,
blebbing makes cell more granular

Question 7

Pyknosis

Answer 7

condensing of nucleus

Question 8

DNA fragmentation

Answer 8

Junctions between nucleosomes chopped off

Question 9

Bax

Answer 9

Form pores in mitochondria, inducing apoptosis

Question 10

Lamins

Answer 10

Maintain the structural integrity of the nuclear envelope
- are cleaved by caspases (during caspase-mediated apoptosis)

Question 11

I/CAD

Answer 11

(caspases cleave I/CAD, releasing activated CAD)
activated by caspases,
CAD causes DNA fragmentation and chromatin condensation

Question 12

tBID

Answer 12

Type II intrinsic pathway (links extrinsic and intrinsic pathways)

Question 13

Core (protease) of apoptotic pathways

Answer 13

Caspases

Question 14

How are caspases activated

Answer 14

proteolytic cleavage of procaspases

(small + large subunits come together = (heterotetramer) ACTIVE caspase)

Question 15

whats the feedback amplification loop that ensures cell death will occur ?

Answer 15

effector caspases continue cleaving initiator caspases (activating them)

Question 16

Fas (ligand) binding Fas receptor triggers what complex ?

Answer 16

DISC (death inducing signal complex)

Question 17

what does DISC do? activates something …
(extrinsic)

Answer 17

= caspase 8 activation
(pro-caspases binding FADD, binding Fas receptor - DISC
pro-caspases are in close proximity in the DISC complex and can cleave each other
–> releasing active caspase

Question 18

what does the apoptosome do? activates …
(intrinsic)

Answer 18

= caspase 9 activation
(it binds the apoptosome wheel)
Cas 9 -> activates Cas cascade (Cas 3, 6 & 7) – cut substrates + kill cell

Question 19

Cyt C released from what

Answer 19

(through holes in) Mitochondria

Question 20

How does Cty C form apoptosome

Answer 20

Cyt C bind APAF-1,
= conformational change
= CARD domain exposed
= CARD domains create wheel structure, that Cas 9 can bind to

the apoptosome is the platform needed for proximity activation in the intrinsic pathway

Question 21

point of no return in apoptosis

Answer 21

loss of MMP

Question 22

no. of mitochondria in a cell

Answer 22

100-1000’s

Question 23

Key event in initiation of apoptosis

Answer 23

release of mitochondrial contents to cytoplasm
- Cytochrome C
- Calcium

Question 24

Bax induces apoptosis through …

Answer 24

forming holes in the mitochondria
(tubes formed by BH3 proteins)

Question 25

Fine tuners

Answer 25

BH3 domain-only proteins

Question 26

too many pro-survival (Bcl-2) signals cause …

Answer 26

cancer

Question 27

too many pro-apoptotic (Bax) signals cause …

Answer 27

cell death

Question 28

Bcl-2 family role …

Answer 28

bind to Bax family + restrain them

Question 29

BID and BIM activate …

Answer 29

BAX and BAK

Question 30

BCL-2 and BCL-xL sequester (isolate)…

Answer 30

BAX, BAM, BID AND BIM

Question 31

for activation of mitochondrial membrane permeabilisation what 2 event must occur …

Answer 31

1. All Bcl-2 family pro-survival members must be inhibited
2. BAX and BAK are activated by activator BH3-only proteins

Question 32

if no growth signals are received from outside how is apoptosis induced …

Answer 32

Fine tuners bind to Bax and Bak - opening them
exposing their BH3 helix (temporarily)
(if enough Bax/Bak proteins clustering, can form pores in membrane = apoptosis)

Question 33

deletion of pro-apoptotic genes (Bim)

Answer 33

cancer like results,
lumen full (similar to carcinoma in-situ)

Question 34

deletion of pro-apoptotic (Bim) and anti-apoptotic (Bcl-2) genes …

Answer 34

cells are rescued (as Bim and Bcl-2 are involved int eh same stress pathway - bind each other)

Question 35

deletion of anti-apoptotic Bcl-2 genes …

Answer 35

lots of cell death

Question 36

types of diseases associated with increased (dysregulated) apoptosis (5)

Answer 36

1. developmental disorders
2. viral infections (AIDs)
3. Neurological disorders (parkinsons)
4. acute neurological damage
5. cardiovascular disease

Question 37

types of diseases associated with decreased (dysregulated) apoptosis (3)

Answer 37

1. developmental disorders
2. autoimmunity
3. cancer (chronic lymphocytic leukemia)

Question 38

why we want to treat cancer through cell death by apoptosis ? …

Answer 38

other cell death mechanisms cause inflammation and can make cancer worse
more difficult to control

Question 39

how cancer cells use plasticity to evade chemo

Answer 39

EMT (epithelial-mesenchymal transition)

Question 40

alterations of genes in apoptotic pathways that cause cancer (2)

Answer 40

1. indirect (reduction of Bax)
2. direct (less/no critical caspases)

Question 41

how are normal cells tipped for survival

Answer 41

more Bcl-2 than Bax

Question 42

chemotherapeutic agent binds Bcl-2 e.g. …

Answer 42

ABT-199 (mimics BH3)

Question 43

ABT-199 does what …

Answer 43

replaces Bim and Puma, binding Bcl-2, causes apoptosis
allows free active Bax