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Advanced Cellular and Molecular Biology > Apoptosis Extrinsic > Flashcards

Apoptosis Extrinsic Flashcards

1
Q

What are the two general processes by which cells die?

A

Necrosis

Apoptosis

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2
Q

Necrosis refers to cell death that results from ______________________.

A

Injury

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3
Q

Following necrosis, three things occur. What are they?

A
  1. Cell swells
  2. Cell bursts
  3. Inflammatory response follows
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4
Q

Apoptosis refers to cell death that results from ______________, __________________, __________________, and ______________.

A

DNA damage

Withdrawal of essential growth factors or nutrients

Detachment from substrate

Attack by cytotoxic lymphocyte

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5
Q

What word means a literal “falling away”?

A

Apoptosis

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6
Q

Apoptosis can be caused by external stimuli or internal events; regardles, it is an orderly process where the cell systematically breaks down all of its organells, forming __________ bodies that are picked up by _______________, resulting in no inflammatory response.

A

Apoptotic bodies

Phagocytes

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7
Q

What are the three events that comprise apoptosis?

A
  1. Nucleus fragments
  2. Cell fragments (apoptotic bodies)
  3. Fragments are engulfed (by phagocytes), no inflammatory response initiated
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8
Q

What does “ischemia” mean?

A

Inadequate blood flow

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9
Q

What two things can cause necrosis?

A

Overwhelming toxic insult

Ischemia

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10
Q

Necrosis is characterized by cell __________________.

A

Cell swelling

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11
Q

Extracellular signals activate the ______________ pathway of apoptosis.

A

Extrinsic

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12
Q

What causes apoptosis?

A

Normal development and metamorphosis

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13
Q

What are two extracellular signals that can activate the extrinsic apoptotic pathway?

A

Tumor necrosis factors, which are produced by immune cells

Fas ligand, expressed on surface of cytotoxic T cells

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14
Q

Internal signals activate the ____________ pathway of apoptosis.

A

Intrinsic

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15
Q

What internal signals can activate the intrinsic pathway of apoptosis?

A

DNA damage

Loss of cell-extracellular matrix contact

Insufficient nutrients and/or hormone stimulation

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16
Q

What are the four characteristics of apoptosis?

A
  1. Membrane blebbing
  2. Organelle, cytoskeleton, and nuclear lamin degradation
  3. Appearance of phosphatidylserine on the outer leaflet of the plasma membrane
  4. DNA fragmentation
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17
Q

What is known as the “eat me” signal for phagocytes?

A

Phosphatidylserine

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18
Q

Appearance of ______________________ on the outer leaf of the plasma membrane function as the “eat me” signals for phagocytes

A

Phosphatidylserine

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19
Q

DNA fragmentation leads to a DNA ________________.

A

“laddering”

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20
Q

What is a DNA ladder?

A

A banding pattern of DNA where DNA is found in 200 base pair fragments

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21
Q

Why does DNA fragment into ladders?

A

Around 200 base pairs wrap around a histone

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22
Q

What enzymes are activated during apoptosis?

A

Caspases

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23
Q

The enzyme group _____________________ are responsible for the characteristics of apoptosis

A

Caspase

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24
Q

What are caspases?

A

Proteases that contain cysteine in their active site and cleave proteins next to aspartate residues in substrates

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25
Q

Caspases are ____________ that contain cysteines in their active sites and cleave next to aspartate residues in their substrates

A

Proteases

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26
Q

There are two categories of caspases: ___________ and __________.

A

Initatior caspases

Executioner caspases

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27
Q

What do initiator caspases do?

A

Initate apoptosis

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28
Q

What do executioner caspases do?

A

Ultimately cause cell death

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29
Q

Caspases like all proteins are synthesized in a _____-form that must be _______________ cleaved in order to become active.

A

Pro-form

Protealytically

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30
Q

What are the two primary initiator caspases in mammals?

A

Caspase 8

Caspase 9

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31
Q

Initiator caspases are found as inactive _______________ that dimerize upon binding with their ________________ proteins. Once dimerized, they are cleaved, resulting in active initiator caspases.

A

Monomers

Adaptor proteins

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32
Q

When do caspases 8 and 9 become active?

A

After binding adaptor proteins, dimerizing, and undergoing proteolytic cleavage

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33
Q

What activates executioner caspases?

A

Active initiator caspases (e.g., caspase 8 and caspase 9)

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34
Q

What are the three executioner caspases found in mammals?

A

Caspase 3

Caspase 6

Caspase 7

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35
Q

Caspases 3, 6, and 7 are synthesized as _______________ and are activated via dimerization and _______________ cleavage.

A

Pro-caspases

Proteolytic

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36
Q

Executioner caspases cleave other executioner caspases to _____________ them and many cellular targets to produce the apoptotic ______________.

A

Activate

Phenotype

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37
Q

Initiator or executioner caspases lead to DNA laddering?

A

Executioner caspases

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38
Q

Executioner caspases can target ______________ proteins, including cohesions, cadherins, lamins, spectrin, troponin, etc.

A

Structural

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39
Q

Regulators of transcription and translation are cellular targets for ___________________ caspases.

A

Executioner caspases

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40
Q

______________ and signaling molecules are targetted by executioner caspases.

A

Kinases

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41
Q

What are three primary targets of executioner caspases?

A

Structural targets, regulators of transcription and translation, and kinases and signaling molecules

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42
Q

What inhibits executioner (and initiator) caspases?

A

Inhibitor of apoptosis proteins (IAPs)

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43
Q

What does IAP stand for?

A

Inhibitors of apoptosis proteins (IAPs)

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44
Q

Why are initatiors of apoptosis proteins (IAPs) important?

A

They inhibit caspases and function as a “safety net” in case of accidental activation of apoptosis

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45
Q

The extrinsic pathway of apoptosis requires the targetted cell has __________ receptors.

A

Death receptors

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46
Q

The two most common ligands for death receptors are __________________ and __________________.

A

Fas ligands

Tumor necrosis factors (TNF-alpha)

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47
Q

Death receptors contain a cytosolic ______________ domain.

A

Cytoplasmic death domain

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48
Q

Death receptors form ______________________, trimerizing after ligand binding.

A

Homotrimers

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49
Q

What are two common death receptors?

A

Fas death receptor

TNF-alpha death receptor

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50
Q

Death receptors recruit adaptor proteins on the cytosolic side called FADDs, which stands for _________________________.

A

Fas associated protein with death domain

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51
Q

FADD (Fas associated protein with death domain) possess two domains. What are they?

A
  1. A death domain that binds the receptor
  2. A death effector domain (DED) that recruits and activates initiator caspases 8 and 9
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52
Q

What does DED stand for?

A

Death effector domain

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53
Q

The _________domain of a receptor interacts with the ________ domain of adaptor protein.

A

Death domain

Death domain

54
Q

A death effector domain (DED) interact with initiator procaspases, which also have _____________.

A

DED (death effector domains)

55
Q

The Fas and/or TNF receptor binds its adaptor protein ___________________________ (FADD) and together form the ________________________ (DISC).

A

Fas associated protein with death domain

Death-inducing signaling complex

56
Q

What does DISC stand for?

A

Death-inducing signaling complex

57
Q

What do we mean by homotypic binding?

A

In the case of death receptors, both the death receptor and the adaptor protein contain death domains

58
Q

There is another type of TNF receptor that assembles a complex of three parts: __________________, ___________________,and ___________________.

A

TNF receptor associated protein with death domain and (DED) (TRADD)

TNF receptor associated factor (TRAF)

FADD, which recruits and activates procaspase 8

59
Q

Fas and most TNF receptors simply recruit _________________ (FADD) upon ligand binding, which then recruits initiator procaspases 8 and 9.

A

Fas associated protein with death domain

60
Q

There is another type of TNF receptor that assembles a complex of three parts to initiate the extrinsic pathway of apoptosis: __________________, _________________, and __________________.

A

TNF receptor associated protein with dead domain (and DED) (TRADD), an adaptor protein

TNF receptor associated factor (TRAF)

Fas associated protein with death domain (FADD), which ultimately recruits procaspase 8

61
Q

TRADD refers to ______________________.

A

TNF receptor associated protein with death domain (and DED)

62
Q

TRAF refers to ____________________.

A

TNF receptor associated factor

63
Q

FADD refers to __________________________.

A

Fas associated protein with death domain

64
Q

The TNF receptor recruits the adaptor protein _______________, which then recruits procaspase 8 to the site.

A

Fas associated protein with death domain

65
Q

In immune cells, the TNF receptor binding its ligand is “pro-life” as opposed to “__________.” Ligand binding recruits TRAF (_________________) that forms a __________________________________ scaffold and leads to ______________ activation, which then activates immune cells and leads to the ______________ response.

A

Pro-death

TNF receptor associated factor

Polyubiquitin

NF-kappaB

Inflammatory

66
Q

NF-kappaB is a ______________ factor that triggers upregulation of genes involved in the ___________________ response.

A

Transcription factor

Inflammatory

67
Q

In cell except immune cells, TNF receptor binding leads to _______________.

68
Q

NF-kappaB is a ________________ factor and increases expression of a protein called ______________.

69
Q

c-FLIP is a protein that is upregulated by _____________.

70
Q

How does c-FLIp function as a “pro-life” transcription factor?

A

Because it possesses a death effector domain (DED) that competes with procaspase 8 for binding to FADD (Fas associated protein with death domain); binding of c-FLIP to FADD, instead of procaspase 8, inhibits the apoptotic pathway

71
Q

What happens when c-FLIP outcompetes procaspase 8 for FADD binding?

A

The apoptotic pathway is inhibited

72
Q

What is DED?

A

Death effector domain

73
Q

Which orgenlle is most important to the intrinsic pathway of apoptosis?

A

The mitochondria

74
Q

What does the instrinsic pathway of apoptosis require?

A

The release of proteins from the mitochondrial intermembrane space, specifically cytochrome C

75
Q

______________________ is the most critical protein released from the mitochondrial intermembrane space in the ______________ pathway of apoptosis.

A

Cytochrome C

76
Q

Why can cytochrome C leave the mitochondrial intermembrane space during apoptosis?

A

Because of mitochondrail outer membrane permeabilization (MOMP)

77
Q

What does MOMP stand for?

A

Mitochondrial outer membrane permeabilization

78
Q

What proteins function in mitochondrial outer membrane permeabilization (MOMP)?

A

Bcl2 proteins

79
Q

What does Bcl2 stand for?

A

B-cell lymphona (2)

80
Q

Proteins that mediate MOMP are a family of proteins called _______________.

A

Bcl2 (B-cell lymphoma 2)

81
Q

Anti-apoptotic ______ proteins prevent cells from engaging in MOMP. These inculde ______, Bcl-xL, Bcl-W, and Mcl-1.

82
Q

There are three types of proteins in the Bcl2 family: _____-apoptotic, _____-apoptotic, and ____-only.

A

Anti-apoptotic (Bcl-2, Bcl-xL, Bcl-W, Mcl-1)

Pro-apoptotic (Bax, Bak, Bok)

BH3-only (Bad, Bim, Bid, Puma)

83
Q

What Blc2 proteins are pro-apoptotic?

A

Bax, Bak, and Bok

84
Q

Which Bcl2 proteins are anti-apoptotic?

A

Bcl-2, Bcl-xL, Bcl-W, Mcl-1

85
Q

Which Bcl2 proteins are BH3-only?

A

Bid, Bim, Bad, Puma

86
Q

Which group of Bcl2 proteins can be inserted into the outer mitochondrial membrane and result in MOMP?

A

Bax and Bak or the pro-apoptotic group

87
Q

To what does BH refer in BH3-only proteins of the Bcl2 family?

A

“Bcl2 homology domain”

88
Q

What does Bax stand for?

A

Bcl-2 associated protein X

89
Q

What does Bak stand for?

A

Bcl2 associated killer protein

90
Q

Mitochondrial outer membrane permeabilization (MOMP) is inhibited by which anti-apoptotic proteins?

A

Bcl-2, Bcl-xL, etc.

91
Q

How do Bcl-2 and Bcl-xL inhibit MOMP?

A

By binding Bcl2 effector proteins and preventing pro-apoptotic factors Bax and Bak from binding and asssembling

92
Q

Which Bcl2 proteins are responsible for activating MOMP?

A

Bax and Bak

93
Q

Which proteins are required for activation of Bax and Bak and therefore MOMP?

A

The BH3-only proteins: Bid, Bim, Bad, PUMA

94
Q

______, ___________, ____________, and _______________ are BH3-only proteins of the Bcl2 family and are required for assembly of Bax and Bak.

A

Bid, Bad, Bim, PUMA

95
Q

What is the mechanism for mitochondrial outer membrane permeabilization (MOMP)?

A

Bax and Bak dimerize and oligomerize in the outer mitochondrial memb rane, forming channels or pores that allow cytochrome C to escape

96
Q

_________ and Bak can form homodimers; they can sometimes for ______________.

A

Bax

Heterodimers

97
Q

Once dimerized, Bax and Bak form _____________.

98
Q

Oligomerization is required for the process of ________________ in the mitochondria.

A

Mitochondrial outer membrane permeabilization (MOMP)

99
Q

Bak is constitutively ______________-bound.

A

Membrane-bound

100
Q

Activation of Bak in the mitochondrial outer member causes its __-______ to extend, and the _________________ side of the _______________core to latch and collapse into the membrane, thererby separating the two parts of Bak.

A

C-terminus

Hydrophobic

Amphipathic

101
Q

What does this picture refer to?

A

Activation of Bak in the outer mitochondrial membrane

102
Q

Which alpha helix of Bak is embedded in the membrane?

A

Alpha helix 9

103
Q

Which alpha helices constitute the core of Bak?

A

Alpha helices 3, 4 and 5

104
Q

Which alpha helix of Bak contains the BH3 domain?

A

Alpha helix 2

105
Q

Which alpha helices form the latch of Bak?

A

Alpha helices 6, 7, and 8

106
Q

How does Bak dimerization occur?

A

The exposed BH3 domain of the alpha 2 helix binds to the hydrophobic groove of another activated Bak molecule

107
Q

The exposed _____ domain of Bak’s alpha 2 helix binds to the hydrophobic groove of another activated Bak molecule, facilitating ____________.

A

BH3 domain

Dimerization

108
Q

______ shuttles between the cytosol and the membrane, and when in the membrane, it undergoes a _______________ change and dimerizes.

A

Bax

Conformational change

109
Q

Is it Bak or Bax that shuttles between the cytosol and membrane?

110
Q

There are several theories regarding how pores form: (1) Bax and Bak oligomers for protein channel pores; (2) Bax and Bak modulate pre-existing channels; and (3) Bax and Bak facilitate formation of lipidic or toroidal pores. Which of the three theories is most supported by current research?

A

The third model

111
Q

Some ___________ toxins have been shown to produce ______ pores.

A

Bacterial

Lipidic

112
Q

It is hypothesized that these proteins exert a ________-like action that induces curvature of the membrane and ultimately formation of the pore.

113
Q

The core and latch domains of ______ and ______ share structural features with the _________ toxins and antibacterial peptides known to form _____________ pores.

A

Bax

Bak

Bacterial toxins

Lipidic pores

114
Q

Bax and Bak share structural similarities to what proteins, which supports the theory that lipidic pores are formed and facilitate MOMP?

A

Bacterial toxins

Antibacterial peptides

115
Q

In the _____________ model of pore formation, the ________________ latch may slide into a nascent pore to line and stabilize it and then the amphipathic core dimer lines the pore, generating ______________________ alpha9 helices.

A

Clamp

Amphipathic

Antiparallel

116
Q

Explain the clamp model of pore formation.

A

The ampiphatic latch may slide into a nascent pore, lining and stabilizing it. Then the amphipathic core dimer lines the pore, generating antiparallel alpha-9 helices

118
Q

What type of microscopy confirms the lipidic pore model of MOMP?

A

Atomic force microscopy

119
Q

Upon its release, cytochrome C binds _________________.

A

Apaf-1 (apoptotic protease activating factor 1)

120
Q

What does Apaf-1 mean?

A

Apoptotic protease activating factor 1

121
Q

What is an apoptosome?

A

A wheel-shaped heptamer that recurits initiator procaspase 9 to the mitochondrial membrane

122
Q

What domains bind the apoptosome together?

A

CARD domains

(Caspase recruitment domains)

123
Q

Cytochrome C binds __________ and recruit initiator _____________ 9, forming the apoptosome.

A

Apoptotic prootease activating factor 1 (Apaf-1)

Procaspase 9

124
Q

What is a CARD?

A

A caspase recruitment domain

125
Q

Procaspase 9 and cytochrome C bind via ____________ interactions.

A

Caspase recruitment domains (CARD)

126
Q

What are IAPs?

A

Inhibitors of apoptosis proteins

127
Q

What happens as cytochrome C is released?

A

So too are other proteins that bind IAPs or inhibitors of apoptosis proteins

128
Q

As cytochrome C is released, so are other proteins that can bind _________________, which prevents them from inhibiting _____________.

A

Inhibitors of apoptosis proteins (IAPs)

Apoptosis

129
Q

Which two other proteins are released from the mitochondria alongside cytochrome C?

A

Smac/DIABLO

OMI

130
Q

To what do IAPs normally interact?

A

Inhibitors of apoptosis proteins (IAPs) usually interact with caspases, thereby inhibiting apoptosis

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