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BIO230 Section 2 > 2.11: Programmed Cell Death > Flashcards

2.11: Programmed Cell Death Flashcards

1
Q

why is programmed cell death an essential part of normal development

A

cleanly removing excess, old, damaged, abnormal, or malfunctioning cells
(embryonic development, metamorphosis, immune system function)

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2
Q

p__ can activate cell death

A

p53

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3
Q

differentiate between apoptosis vs necrosis

A

apoptosis: highly regulated, reproducible programmed cell death; carefully dismantles the cell and signals for its removal by engulfment
necrosis: accidental, uncontrolled cell death and can cause inflammation

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4
Q

explain how inflammation occurs

A

as apoptosis carefully dismantles the cell and signals for its removal by engulfment. the innards goes out and neighboring cells know this is wrong = inflammation

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5
Q

list the changes that happen during apoptosis:

A
  • cell shape changes and shrinkage
  • cytoskeleton disassembly
  • decreased cell adhesion
  • dna fragmentation
  • surface lipid changes
  • cell removal by engulfment
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6
Q

state the signal for engulment

A

surface lipid changes

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7
Q

____________ trigger apoptosis and have specific targets

A

caspase proteases

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8
Q

caspases are synthesized as __________, signals initiate caspase cleavage to form active ______________

A

inactive procaspases, caspase dimers

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9
Q

how are caspase cascades created and examples

A

some caspases can cleave and activate other caspases to create an amplified caspase cascade.
ex: active initiator caspases can cleave and activate executioner caspases = cascade and one initiator can cleave many executioners amplifying the signal = cascade

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10
Q

t/f caspases cleave specific target proteins to trigger apoptosis

A

true

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11
Q

________ caspases activate _________ caspases

A

initiator caspases activate executioner caspases

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12
Q

which caspases are initiator and which are executioner

A

initiator: caspase 8 and 9
executioner: caspase 3, 6, 7

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13
Q

how are initiator caspases formed

A

they are cleaved and activated in response to apoptotic signals

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14
Q

how are executioner caspases formed

A

active initiator caspases can cleave and activate executioner caspases creating a caspase cascade

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15
Q

t/f one initiator caspase can cleave many executioners

A

true

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16
Q

executioner/initiator caspases cleave target proteins in the cell to initiate apoptosis

A

executioner

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17
Q

caspases mediate key changes during apoptosis, state the caspase targets for the following phenotypic changes during apoptosis:
1. cell shape changes and shrinkage
2. dna fragmentation
3. cytoskeleton disassembly
4. surface lipid changes

A
  1. cell shape changes and shrinkage: cell-cell adhesion proteins
  2. dna fragmentation: breakdown of nuclear lamins, activation of dna endonucleases
  3. cytoskeleton disassembly: alter actin regulating proteins
  4. surface lipid changes: lipid distribution proteins: flippase inactivation and scramblase activation
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18
Q

explain how executioner caspases indirectly cause DNA breakdown

A

inactive CAD is bound to iCAD (i stands for inhibitor) and an active executioner caspase (eg 3) comes and cleaves iCAD = activate cad to cause dna cleavage of dna between nucleosomes

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19
Q

describe how caspase 3 causes cleavage of dna between nucleosome

A

caspase 3 cleaves off iCAD from CAD to allow CAD to do the cleave

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20
Q

executioner caspases alter cell surface lipid composition, compare and contrast between health cells and when apoptotic cells fail to maintain this balance

A

Healthy cells:
- Have a specific lipid makeup at the cell surface
- Flippases move lipids from one side to the other (ec to cytosol) to maintain this distribution

Apoptotic cells fail to maintain this balance:
- Caspase cleaves flippase to inactivate it
- Caspase activates scramblase (random flipping) to move more lipids to the outer layer

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21
Q

t/f apoptosis can be triggered by extrinsic or intrinsic pathways

A

true - Both pathways activate executioner caspases & caspase cascade

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22
Q

describe the extrinsic pathway of apoptosis

A

Extrinsic pathway: depends on cell surface receptors binding to an extracellular signal molecule to activate executioner caspases

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23
Q

describe how apoptosis can be triggered by intrinsic pathways

A

Intrinsic pathway: depends on intracellular receptors (depends on cytochrome C release) to activate executioner caspases

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24
Q

provide an example of outside signal triggering intrinsic apoptosis

A

uv light

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25
Q

Fas ligand functions as a monomer, dimer or trimer

A

trimer

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26
Q

which caspase has a death effector domain (DED)
*actually has two of them

A

caspase 8

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27
Q

which protein has both a death effector domain and death domain

A

FADD adaptor protein

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28
Q

which domains do FADD adaptor proteins have

A

death effector domain and death domain

29
Q

Fas death receptor at the plasma membrane has which domain

A

death domain

30
Q

death domains can be found where, death effector domains can be found where

A

death domains: FADD adaptor proteins, Fas death receptor
death effector domain: FADD adaptor protein, caspase 8

31
Q

killer lymphocytes express cell surface _____ ligands that bind to ?

A

cell surface fas ligands that bind to fas death receptor on the target cell pm

32
Q

which apoptosis pathway is activated by cell surface receptors

A

extrinsic pathway

33
Q

describe how the extrinsic apoptosis pathway is activated by cell surface receptors

A
  • the fas ligand on the killer lymphocyte plasma membrane comes and binds to the fas death receptor on target cell pm
  • fas receptor activation, DISC (death inducing signaling complex) assembly, caspase 8 activation by dimerization
  • Fas death receptor with exposed death domains, exposed DEDs on caspase 8 and FADD
  • caspase 8 filaments do criss cross (cross cleavage), subunit rearrangement, release of mature activated caspase 8 dimers into cytosol
  • on the DISC you can release prodomains and activate new caspases - there is activation by cleavage of executioner caspases 3 & 7 leading to apoptosis of the target cell
  • release of killer lymphocyte
34
Q

what is the active form of caspase 8; mono, dimer, trimer

A

dimer

35
Q

______ receptors help healthy cells stay alive

A

decoy receptors

36
Q

what do decoy receptors lack

A

the ic death domain

37
Q

what is the point of decoy receptors

A

evade extrinsic apoptosis pathway signals

38
Q

what happens when Fas ligand binds a decoy receptor

A

no DISC assembles so apoptosis not triggered

39
Q

the intrinsic apoptosis pathway depends on ______ and _______

A

apaf1 and cytochrome C

40
Q

what are the functions of cyt C and apaf1

A

cytochrome C binds to Apaf1, this exposes the CARD domain (on apaf1) and oligomerization domain on Apaf1

41
Q

which protein is the CARD domain apart of

A

apaf1

42
Q

explain the intrinsic apoptosis pathway that is activated by cyt c release

A
  • the apoptotic stimulus causes cyt c release from the intermembrane space of the mitochondrion
  • the inactive apaf1 protein comes and when cyt c + dATP bind to apaf 1 it activates it
  • active apaf1 has bound dATP, exposed oligomerization domain, exposed CARD
  • oligomerization of apaf1 causes pinwheel structure
  • recruitment of caspase 9 monomers to form apoptosome and caspase 9 activation by dimerization (the inactive caspase 9 has unexposed CARD) == apoptosome’
  • apoptosome causes cleavage and activation of executioner caspases by activated caspase 9 dimers
43
Q

where in the mitochondrion are cyt c usually at

A

intermembrane space

44
Q

how are caspase 9s activated

A

dimerization

45
Q

What will happen in cells containing a mutant Apaf1 that lacks a CARD
domain?
a) Apaf1 will bind to cytochrome c released from mitochondria, but will not
associate with Caspase-9.
b) Apoptosome formation will be unaffected, and cell death will occur
because of cytochrome c loss.
c) Cytochrome c release from mitochondria will be prevented.
d) Apaf1 will not bind to cytochrome c.

A

A. the pinwheel won’t form
B is wrong bc apoptosome won’t form. C is wrong be it still happens

46
Q

how are cyt c able to pass through mitochondrial outer membrane

A
  • Cyt c cannot usually pass through the
    mitochondrial outer membrane
  • Apoptotic stimuli trigger Bak & Bax
    proteins to form a channel in the outer
    mitochondrial membrane
47
Q

what channels promote MOMP (mitochondrial outer membrane permeabilization)

A

Bak and Bax

48
Q

t/f only cyt c can leave the mitochondrial intermembrane after bak and bax channel formed

A

false, other proteins can also exit

49
Q

how can other Bcl2 family proteins inhibit MOMP

A
  • Bcl2 family members Bcl2 & BclxL are similar to Bak & Bax
  • These can can bind to Bak/Bax and prevent them from forming channels (ie BclxL blocks oligomerization of activated Bak)
  • So, Bcl2 & BclxL block MOMP and are anti-apoptotic proteins
50
Q

list the antiapoptotic bcl2 family proteins

A

Bcl2, BclxL, Mcl1

51
Q

list the pro-apoptotic Bcl2 family effectors

A

bak, bax

52
Q

list the pro-apoptotic BH3 only proteins

A

Bad, Bim, Bid, Puma, Noxa

53
Q

after an apoptotic stimulus, Bak becomes activated and exposes what domain

A

BH3 domain

54
Q

what happens if you have too much antiapoptotic bcl2 family proteins

A

makes cells hard to kill = cancer

55
Q

describe how Bcl2 family proteins can promote MOMP

A
  • Bad is another Bcl2 family - binds to Bcl2 & BclxL: liberates the activated Bak that the BclxL prevented the oligomerization of
  • Bad promotes MOMP and is an
    pro-apoptotic protein
56
Q

t/f IAPs block apoptosis

A

true, they stand for inhibitors of apoptosis

57
Q

IAPs block apoptosis from accidentally occurring, provide an example

A

XIAP can directly block initiator and executioner caspases (eg caspase 9, caspase 3 and 7) = XIAP is an antiapoptotic protein

58
Q

anti-iaps are pro/anti apoptotic

A

pro

59
Q

describe how MOMP releases anti-IAP proteins

A
  • Anti-IAP proteins are usually in the
    mitochondrial intermembrane space
  • Anti-IAPs are released with Cyt c when
    MOPM is triggered
  • Anti-IAPs inhibit XIAP, allowing the caspase
    cascade to trigger apoptosis
60
Q

many cells will undergo apoptosis if they are not continually supplied with _______________

A

survival factors

61
Q

what will happen to cells that leave their correct environment

A

no longer be protected by survival factors

62
Q

limited availability of ___________ can regulate cell numbers

A

survival factors

63
Q

distinguish between how survival factors can activate anti-apoptotic proteins and how they can inactivate pro-apoptotic proteins

A

Survival factors can activate anti-apoptotic proteins
- Survival factor initiates a signaling cascade
- Bcl2 transcription increases
- Bcl2/BclxL block Bak/Bax from forming a channel in the mitochondrial outer membrane
- MOMP is blocked, apoptosis does not proceed

Survival factors can inactivate pro-apoptotic proteins
- Survival factor initiates a signaling cascade
- Akt kinase is activated and phosphorylates Bad
- Phosphorylated Bad is inactive so Bad cannot
inhibit Bcl2 & BclxL
- Bcl2/BclxL block MOMP, apoptosis does not proceed

64
Q

does Bcl2 transcription increase or decrease when survival factors are activating anti-apoptotic proteins

A

increase

65
Q

what enzyme is activated when survival factors can inactivate pro-apoptotic proteins

A

Akt Kinase

66
Q

what does Akt kinase do

A

phosphorylates Bad during the inactivation of pro-apoptotic proteins mechanism by survival factors

67
Q

is phosphorylated Bad active or inactive

A

inactive

68
Q

explain how inappropriate cell death can lead to disease

A
  • cancer cells display properties that should mark them for apoptosis, including: changes to cell adhesion, DNA damage, survival outside their usual environment
  • To grow and proliferate, cancer cells must escape apoptosis
69
Q

Which of the following would increase apoptosis?
a) Overexpression of a decoy FAS receptor.
b) Reduced cytosolic concentration of IAPs.
c) Increased Bad phosphorylation.
d) Increased Akt kinase activity.

A

B.
A the decay helps you live. C it inactivate pro-apoptosis. Akt kinase phosphorylates bad rendering it inactive

BIO230 Section 2 (12 decks)

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