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z:Cell 300 > Lecture 22: Apoptosis > Flashcards

Lecture 22: Apoptosis Flashcards

1
Q

Two main ways in which cells die/types of death:

A

-death by injurious events or toxic agents (necrosis)
-induced to commit suicide (apoptosis)

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2
Q

necrosis (def.) and happens in cells that are ______

A

-unnatural death
-damaged by injury (mechanical damage + exposure to toxic chemicals/viruses)

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3
Q

Necrosis steps

A

1) Damage by injury
2) Cell + its organelles swell -> ability of the plasma to control passage of ions + water is disrupted
3) Cell contents leak out
4) Inflammation of surrounding tissues

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4
Q

Apoptosis is ____ process that is intrinsic to ______

A

orderly
cell physiology

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5
Q

Characteristics of cells undergoing apoptosis

A

-shrinkage
- mitochondrial integrity is disrupted -> release of cytochrome C
-blebs on the surface
-chromatin in nuclei degraded
-break into small, membrane-wrapped fragments called apoptotic bodies
-phosphatidylserine (PS) exposed on cell surface

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6
Q

Purpose of apoptotic bodies (+ method)

A

limits inflammation; immune cells remove the bodies

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7
Q

purpose of apoptosis (aka _____)

A

-programmed cell death
-needed to remove unwanted tissues

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8
Q

apoptosis is the controlled _____

A

demolition of the cell

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9
Q

in healthy cells, PS is _____

A

on the inner leaflet of PM

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10
Q

What is the purpose of exposing PS in outer leaflet during apoptosis?

A

PS is bound by receptors on phagocytic cells (macrophages and dendritic cells) which engulf apoptotic bodies

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11
Q

necrosis typically involves a ____ and a necrotic cell can ____

A

-reversible injury
-recover

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12
Q

necrosis + apoptosis both involves ____ but apoptosis has smaller _____ for controlled destruction

A

membrane blebs

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13
Q

necrosis doesn’t _____ like apoptosis

A

break into apoptotic bodies

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14
Q

single dead cell = ______

A

many apoptotic bodies

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15
Q

epithelial cell vs apoptotic cell

A

epithelial cell are in contact with one another
apoptotic cell round up & withdraw connections

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16
Q

drug that induces apoptosis

A

Daunorubicin

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17
Q

Importance of Apoptosis

A
  1. Needed for proper development (fingers/toes needed the apoptosis of tissue between them, removal of embryonic tails)
  2. Needed to destroy cells that threaten organism (virus-infected cells, cell with DNA damage -> cancer)
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18
Q

________ can kill virus-infected cells by inducing apoptosis. Some viruses _____

A

-Cytotoxic T lymphocytes (CTLs)
-counteract apoptosis

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19
Q

Damage to genome can cause cell to:

A

-Disrupt proper embryonic development leading to birth defects
-Become cancerous

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20
Q

Cells respond to DNA damage by _______, a potent inducer of _____.

A

-increasing their production of the transcription factor p53
-apoptosis

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21
Q

Mutations in ______ found in >50% of cancer cells

A

p53 gene

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22
Q

______ induces apoptosis in some types of cancer
cells

A

Radiation/chemotherapy

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23
Q

As immune response wanes, effector cells
must be _______

A

-removed to prevent them from attacking the body

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24
Q

______ induce apoptosis in other immune cells (and in themselves). Defects in the apoptotic machinery associated with _______

A

-Cytotoxic T lymphocytes
-autoimmune diseases (e.g. lupus erythematosus and rheumatoid arthritis)

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25
Q

DISC stands for ______

A

Death-Inducing Signaling Complex

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26
Q

Assembly of DISC involves _____

A

1) killer lymphocyte displays Fas ligand
2) target cell has Fas death receptor
3) Fas death receptor interacts with FADD adaptor protein via death domain (on both proteins)
4) FADD adaptor protein interacts with caspase 8 via death effector domain (on both proteins)

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27
Q

DISC = _______

A

FAS death receptor + FADD adaptor protein + caspase

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28
Q

FADD adaptor proteins have two domains (+ what they bind to)

A

-death domain (Fas death receptor)
-death effector domain (initiator caspase)

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29
Q

initiator caspase proteins have two domains (+ what they bind to)

A

-adaptor binding domain
-protease domain (has cleavage site)

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30
Q

apoptotic signal lead to the _____

A

dimerization, activation and cleavage of the inactive initiator caspase –> active initiator caspase

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31
Q

active caspase does what?

A

cleaves executioner caspase –> active caspase

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32
Q

Caspases stands for _____

A

Cysteinyl aspartyl proteinases

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33
Q

Caspases cleave after _______

A

aspartate residues in substrates

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34
Q

How different caspases in human cells?

A

15

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35
Q

Two main types of caspases

A

1) Initiator caspases
2) Executioner/effector caspases

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36
Q

Initiator caspases are _____

A

Caspases 8,9

37
Q

Executioner/effector caspases are _____

A

Caspases 3,6,7

38
Q

Role of Initiator caspases 8, 9

A

-activate executioner caspases and some Bcl-2 family members (Bid)

39
Q

zymogen (def.)

A

inactive precursor of an enzyme

40
Q

Activation of Initiator caspases 8,9 triggered by ______

A

oligomerization of the zymogen on adaptor or scaffold (eg. FADD-Fas associated death domain) followed by autocleavage

41
Q

Executioner/effector capsases 3,6,7 function

A

-Cleave wide variety of substrates including proteins that confer structure to cells (cytoskeletal and nuclear proteins)

42
Q

Executioner/effector caspases 3,6,7 are activated _____

A

by cleavage by caspases 8,9

43
Q

Caspases can be activated by _______

A

to distinct apoptotic pathways

44
Q

Two apoptotic pathways

A

-Intrinsic/Mitochondrial pathway
-Extrinsic/Death receptor pathway

45
Q

Intrinsic/Mitochondrial Pathway is activated by _______

A

-lack of survival factors
-intracellular damage (oxidative or radiation damage)

46
Q

Intrinsic/Mitochondrial Pathway: Survival factors for lymphocytes & neurons that prevent apoptosis)

A

-Interleukin-2 (IL-2) for lymphocytes
-growth factors for neurons

47
Q

Activation of Intrinsic/Mitochondrial Pathway leads to ______

A

activation of caspase-9

48
Q

Intrinsic/Mitochondrial Pathway process involves ____

A

Bcl-2 family members

49
Q

Intrinsic/Mitochondrial Pathway does not require _____

A

outside signal

50
Q

neurons (and other cell types) undergo apoptosis when? why?

A

-absence of growth factors
-to adjust number of nerve cells to size of target

51
Q

_____ regulate apoptosis. They divided into _____

A

-Bcl-2 family members (20)
-Bcl-2, Bax, BH3-only

52
Q

Bcl-2 family members require _______ which is important for function and function as ______

A

-association with members
-oligomers

53
Q

Bcl-2 subgroup is _____

A

anti-apoptotic; inhibit Bax (mainly) and initiator caspases
(eg. Bcl2, BclXl)

54
Q

Bax subgroup is _____

A

pro-apoptotic; forms pores in mitochondrial membrane, activates initiator caspases
(eg. Bax, Bak)

55
Q

BH3-only subgroup is _____

A

primarily apoptotic initiators that function by inhibiting function of Bcl-2 members (mainly) + activating Bax –> tips balance of power to apoptosis
(eg. Baf, Bim, Bid, Puma, Noxa)

56
Q

anti-apoptotic Bcl2 protein had these domain: _______

A

BH4
BH3
BH1
BH2

57
Q

pro-apoptotic Bax effector protein had these domains: _______

A

BH3
BH1
BH2

58
Q

pro-apoptotic BH3 protein had these domains: _______

A

BH3

59
Q

In healthy cells, ____ Bcl-2 protein is where?

A

anti-apoptotic
in outer membrane of mitochondria (transmembrane protein)

60
Q

Internal damage to the cell (ex. _____) leads to _____ production of _______ which does what?

A

-DNA damage
-p53-dependent production of Bax (pro-apoptotic protein) which bind to mitochondria

61
Q

Alteration of ratio of ________in mitochondrial membrane determines whether _____

A

-death promoting/death preventing Bcl-2 family members
-cell lives or dies

62
Q

Pro-apoptotic conditions cause ________

A

release of cytochrome c from mitochondria through aggregated Bax proteins that forms a pore in mitochondrial membrane

63
Q

In healthy cells, cytochrome c is in ______ and _____=_____

A

-intermembrane space
-Bcl2=Bax

64
Q

Released cytochrome c binds to _____forming ______

A

-Apaf-1 (Apoptotic protease activating factor) and procaspase 9
-the apoptosome

65
Q

Apaf-1 functions as a ________ and causes recruitment and activation of ________ which then _____

A

-scaffold for oligomerization of procaspase 9
-caspase 9
-cleaves and activates the effector caspase 3»downstream events leading to apoptosis

66
Q

Anti-apoptotic Bcl2 proteins maintain ______ and prevent ______

A

-mitochondrial integrity by preventing aggregation of Bax proteins in membrane
-cytochrome c release

67
Q

intrinsic pathway: apoptotic stimulus -> ____

A

-activated BH3-only protein (Bid/Bad) –>
-inactivated anti-apoptotic Bcl2 protein & activated Bax protein forms pores in mitochondrial membrane
-cytochrome C release through pore

68
Q

Some viral proteins (like RV capsid) do what to Bax?

A

interact with Bax and block it’s pore function thereby blocking release of cytochrome c&raquo_space; blocks apoptosis of virus-infected cell

69
Q

Extrinsic/Death Receptor Pathway is activated by _______

A

ligand-induced aggregation of receptors (tumor-necrosis receptor family, Fas) on cell surface

70
Q

Activation of Extrinsic/Death receptor pathway leads to ________

A

clustering of caspase-8 (or -10) zymogens followed by
autocatalysis and activation

71
Q

Death Receptor Pathway has signaling through _______

A

“death receptors” including Fas (CD95), TNFR & others

72
Q

Death Receptor Pathway: Ligands initiate signaling via _______

A

receptor oligomerization, recruitment of adaptor proteins and activation of caspases

73
Q

Death Receptor Pathway steps

A
  1. FasL (ligand on lymphocyte/T cells) binding induces Fas oligomerization
  2. Recruits pro-caspase 8 via the adapter protein FADD to form the death inducing signaling complex (DISC).
  3. Pro-caspase 8 then oligomerizes and is activated via autoproteolysis.
  4. Activated caspase 8 (initiator caspase) stimulates apoptosis via two parallel cascades
74
Q

Activated caspase 8 (initiator caspase) stimulates apoptosis via two parallel cascades:

A

A. Directly cleaves and activates caspase-3.
B. Activates mitochondrial (Stress) pathway by cleaving Bid (Bcl-2 family)

75
Q

mitochondrial (Stress) pathway

A

-cleaves Bid (Bcl-2 family)
-truncated Bid (tBid) is then myristoylated and translocates to mitochondria
-induces cytochrome c release, which activates caspases 9 and then 3.
-activated effector caspases (3, 6 and 7) cleave cytoskeletal, nuclear proteins and activate nucleases that destroy chromatin.

76
Q

When cytotoxic T cells recognize (bind to) their target, they ______.

A

produce more FasL at their surface

77
Q

Intersection of Extrinsic and Intrinsic pathways via _____

A

Bid (BH3-only protein)

78
Q

Apoptosis can be induced experimentally by ______

A

the microinjection of cyto-c into cytoplasm
adding ant-Fas antibody&raquo_space; clustering of Fas

79
Q

Regulators of Intrinsic & Extrinsic pathways

A

Intrinsic: BH3, BCl-2, Bax
Extrinsic: Death receptors

80
Q

Scaffolds of Intrinsic & Extrinsic pathways

A

Intrinsic: Apaf-1
Extrinsic: FADD

81
Q

Initiators of Intrinsic & Extrinsic pathways

A

Intrinsic: caspase-9
Extrinsic: caspase-8

82
Q

Effectors of Intrinsic & Extrinsic pathways

A

Intrinsic + Extrinsic : caspase 3,6,7

83
Q

Apoptotic pathways are often _____ in cancer cells by ______

A

-impaired
-increasing the transcription and production of anti-apoptotic Bcl2 protein or
-inactivating pro-apoptotic BH3-only protein (Bad)

84
Q

Cancer cells have a lot of this protein?

A

Bcl2 proteins

85
Q

BH3-only protein (Bad) normally does this to promote apoptosis? but when phosphorylated by ____ it does this?

A

-binds to Bcl2 protein keeping it inactivate
-active Akt kinase (PKB)
-releases active Bcl2 which blocks apoptosis

86
Q

Survival of cells often requires _____ and/or _____. Without signal, _____blocks protective effects of Bcl-2/Bcl-XL —> _____

A

-continuous stimulation from other cells
-adhesion to the surface on which they are growing
-Bad
-stops preventing apoptosis&raquo_space; apoptosis

87
Q

In the presence of trophic/growth factors, signal transduction pathway leads to ______which inhibits ________(by _____)&raquo_space;>Apoptosis is _____

A

-activation of protein kinase B (PKB) = Akt
-the function of the pro-Apoptotic protein Bad
-phosphorylation
-blocked and cell survived

88
Q

Growth/Trophic factors can induce _____

A

inactivation of pro-Apoptotic regulators

89
Q

Possible cancer treatments

A

1) PI-3 kinase inhibitors (PI-3 activates PKB which inactivates Bad to release anti-apoptotic Bcl2 protein&raquo_space; constitutively activate PKB mutant rescues cell)
2) Bcl-2 inhibitors (Bcl2 is anti-apoptotic -> inhibitor leads to apoptosis)

z:Cell 300 (17 decks)

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