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Disease > Exam 2 - Apoptosis > Flashcards

Exam 2 - Apoptosis Flashcards

1
Q

Apoptosis is the _____ for cells unless they are provided survival factors.

A

default

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2
Q

What are 4 instances when cells need to die?

A
  1. Infected with viruses
  2. Elimination of immune cells
  3. Tissue development
  4. DNA damage
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3
Q

T/F: Apoptosis is a part of animal development

A

True

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4
Q

What is an example of apoptosis being involved in an animal’s development?

A

Interdigital tissue being removed in orderly function

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5
Q

What type of molecule is MDM2?

A

E3 ubiquitin ligase

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6
Q

What does phosphate do to p53?

A

Frees it once bound

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7
Q

What phases does phosphorylation of p53 trigger to start in the cell cycle?

A

G2/M

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8
Q

What happens to cell division and apoptosis when there are mutations in Rb or Ras?

A

Increased cell division; normal apoptosis

= tumor

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9
Q

What happens to cell division and apoptosis when there is a mutation in p53?

A

Normal cell division; decreased apoptosis

= tumor

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10
Q

What is the cell shape/size in apoptosis vs. necrosis?

A

Apoptosis: single cells/small clusters; cell shrinkage/convolution

Necrosis: contiguous cells; cell swelling

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11
Q

What is the state of the nucleus in apoptosis vs. necrosis?

A

Apoptosis: pyknosis and karyorrhexis

Necrosis: Karyolysis, pyknosis, karyorrhexis

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12
Q

What is pyknosis?

A

Nucleus condensation

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13
Q

What is karyorrhexis?

A

Fragmentation of nucleus

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14
Q

What is karyolysis?

A

Chromatin dissolution

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15
Q

What is the state of the cell membrane in apoptosis vs. necrosis?

A

Apoptosis: intact cell membrane

Necrosis: Disrupted cell membrane

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16
Q

What is the state of the cytoplasm in apoptosis vs. necrosis?

A

Apoptosis: cytoplasm retained in apoptotic bodies

Necrosis: cytoplasm released

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17
Q

In which cell (apoptotic or necrotic) does inflammation occur?

A

Necrotic

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18
Q

What takes up vesicles released due to apoptosis?

A

Macrophages

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19
Q

What is a CAD?

A

Caspase activated DNA endonuclease

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20
Q

How is CAD activated?

A
  1. Inactive CAD bound to iCAD
  2. Executioner caspase cleaves iCAD
  3. CAD is active
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21
Q

What does CAD do when active and which assay can measure this?

A

Plays a role in DNA fragmentation by cleaving DNA everywhere that it is not protected by histones.
- TUNEL assay

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22
Q

How does the TUNEL assay work?

A

DNA-damaged site is labeled in the cell using a fluorescent assay.

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23
Q

What events does necrosis typically follow?

A

Injury, trauma, lack of blood, lack of nutrient supply

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24
Q

In what organism is apoptosis normally seen?

A

Animals

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25
Q

What changes orientation in the cell membrane during apoptosis and why is this important?

A

Phospholipid phosphatidyl serine; presents an “eat-me” signal to macrophages so they can be phagocytosed

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26
Q

Where is the active site on a caspase?

A

Cysteine

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27
Q

Where do caspases cleave?

A

Aspartic acid

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28
Q

What are the 2 classes of caspases?

A
  1. Initiator caspases

2. Executioner caspases

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29
Q

What is the signal flow of an initiator caspase/how is it activated?

A

Inactive monomers dimerize upon receiving an apoptotic signal on adaptor proteins (binds to pts)

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30
Q

How is the executioner caspase activated?

A

It is cleaved by the active initiator caspase

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31
Q

What does an active initiator caspase do?

A

Activates executioner caspase by cleaving it

32
Q

What does an active executioner caspase do?

A

Cleaves multiple substrates leading to apoptosis

33
Q

T/F: Once a caspase activates another to begin a cascade, the cell can sometimes escape that cascade to avoid apoptosis.

A

False; once the cell is in the cascade, there is no turning back – it is destined to apoptose.

34
Q

What protein is cleaved by caspase to allow the cell to collapse and shrink?

A

actin

35
Q

What proteins are cleaved by caspase that breaks down the nucleus and what is the result?

A

Lamins; result in the cell’s DNA being exposed, allowing endonucleases to come in and break down the DNA.

36
Q

What are the 2 mechanisms by which initiator caspase activates?

A
  1. Extrinsic pathway

2. Intrinsic pathway

37
Q

What is the extrinsic pathway?

A

Death receptor pathway; always involves 2 cells (ligand–receptor)

38
Q

What is the intrinsic pathway?

A

Mitochondrial pathway

39
Q

What activates the intrinsic pathway?

A

Intracellular factors (oxidative stress, hypoxia, nutrient deprivation)

40
Q

What does the intrinsic pathway cause?

A

Mitochondrial outer membrane permeabilization and cytochrome C leakage into the cytoplasm from mitochondria

41
Q

Where is cytochrome C present in mitochondria?

A

Intermembrane space

42
Q

How many subunits does the human apoptosome have?

A

7

43
Q

What activates the human apoptosome?

A

cytochrome C

44
Q

How many subunits does the fruit fly apoptosome have?

A

8

45
Q

What activates the fruit fly apoptosome?

A

Cytochrome C BUT may not always need it for activation

46
Q

Where do caspases bind on the nematode apoptosome?

A

Back side of the ring

47
Q

What does cytochrome C fuse with when it leaves the cell?

A

Green Fluorescent Protein

48
Q

Bax is a type of _____ protein.

A

Bcl2

49
Q

How does Bax assist in cytochrome C leakage?

A

Bax proteins are present in the mitochondrial membrane; they aggregate under an apoptotic stimulus and provide pores for cytochrome C and other pts to exit the cell

50
Q

What are the 3 types of Bcl2 proteins that regulate the intrisic pathway?

A
  1. Pro-apoptotic (pore-forming) Bax
  2. Anti-apoptotic Bcl2
  3. Proapoptotic BH3-only Bad
51
Q

What happens if Bcl-2 binds Bax?

A

No cytochrome C leakage bc no pores can be formed

52
Q

What happens when Bad binds Bax?

A

Bax aggregation and cytochrome C leakage (formation of pores)

53
Q

What does IGF-1 stimulate?

A

Cell survival and growth

54
Q

What does IGF-1 inhibit?

A

Apoptosis

55
Q

What type of signaling pathway does IGF-1 utilize?

A

enzyme-linked

56
Q

What are the 7 steps of the IGF-1 pathway to inhibit apoptosis?

A
  1. IGF-1 (survival signal) binds receptor tyrosine kinase
  2. RTK is phosphorylated and activated
  3. PIP₂ –> PIP₃
  4. Akt is phosphorylated and activated
  5. Akt phosphorylates Bad (bound to Bcl-2)
  6. Bad dissociates from Bcl-2
  7. Bcl-2 is activated and inhibits apoptosis
57
Q

Other than going into the nucleus, what other way does p53 induce apoptosis?

A

By dissociating from mdm2 and stimulating aggregation of Bax and Bak proteins, which form pores in mitochondria for cytochrome C leakage.

58
Q

p53 is mutated in over ___% of cancers.

A

50%

59
Q

What are the 2 main ways that apoptosis can be inhibited through survival factors?

A
  1. Receptor regulates transcription in the nucleus, resulting in Bcl-2 proteins being present
  2. Active Akt kinase causes dissociation of Bcl-2 and Bad – Bad is inactivated, Bcl-2 is active and inhibits apoptosis
60
Q

What is a DISC?

A

Death-Inducing Signaling Complex

61
Q

How does the death receptor (extrinsic) pathway function (5 steps)?

A
  1. Killer lymphocyte with Fas ligand binds to Fas death receptor on cell surface
  2. DISC is assembled
  3. Caspase-8 is cleaved and activated
  4. Executioner caspases are activated
  5. Target cell udergoes apoptosis
62
Q

How is apoptosis activated from inside the cell (intrinsic pathway) (4 steps)?

A
  1. Cytochrome C released and binds to Apaf-1
  2. Apaf-1 aggegates and binds to procaspase-9
  3. Procaspase-9 is activated
  4. Caspase cascade is activated
63
Q

Cells are constantly _____ multiple inputs to decide whether to divide, differentiate, or die.

A

balancing

64
Q

What 3 processes can cells go through during proper organ development?

A
  1. Proliferation
  2. Survival
  3. Apoptosis
65
Q

Proper organ development requires _____.

A

Coordination of cellular processes

66
Q

What is microphthalmia?

A

“Small eye” phenotype; proliferation defect; genetic/infectious/environmental

67
Q

Microphthalmia is a _____ defect.

A

proliferation

68
Q

What occurs when there is too much proliferation of muscle cells?

A

Hypertrophy; myostatin mutation

69
Q

What is the normal role of myostatin?

A

Differentiation factor that inhibits myogenesis.

70
Q

What are 4 examples of mutations in myostatin?

A
  1. Mighty mice
  2. Belgian Blue Cattle
  3. Texel sheep
  4. Whippets
71
Q

What occurs in a myostatin mutation at the genetic level?

A

Sequence is truncated (313 AAs instead of normal 375 AA protein)

  • TGT –> TGA
  • Cysteine –> stop codon
72
Q

What is syndactyly?

A

Fusion of digits

73
Q

How does syndactyly occur?

A

Incomplete apoptosis of interdigital cells between developing digits

74
Q

Where is survival best understood?

A

developing brain

75
Q

What do cells compete for in survival?

A

Survival factors

76
Q

What 2 things are required by cells for normal development?

A
  1. Proliferation

2. Apoptosis

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