MODULE 8: Chapter 8.4

Question 1

What is the role of tumor necrosis factor-α (TNF-α) in cell signaling?

Answer 1

TNF-α initiates programmed cell death (apoptosis) and stimulates a cell survival pathway.

Question 2

What determines the downstream cellular response in TNF receptor signaling?

Answer 2

The relative levels of downstream pro-apoptotic and anti-apoptotic proteins.

Question 3

What is the function of the death domain (DD) in TNF receptors?

Answer 3

It acts as a protein-protein interaction module for assembling adaptor signaling complexes.

Question 4

Fill in the blank: The two types of pathways regulated by TNF receptor signaling are ______ and ______.

Answer 4

[cell death pathway] and [cell survival pathway]

Question 5

What is the primary function of caspases in the apoptosis pathway?

Answer 5

They are enzymes that degrade cellular proteins and kill the cell.

Question 6

What is the role of the adaptor protein TRADD in TNF receptor signaling?

Answer 6

TRADD binds to the TNF receptor and facilitates the assembly of downstream signaling complexes.

Question 7

True or False: The Fas receptor is a member of the TNF receptor family.

Answer 7

True

Question 8

What complex is formed in the apoptosis pathway when TRADD binds to FADD?

Answer 8

The TRADD–FADD complex.

Question 9

What does the activation of caspase 8 lead to in the apoptosis pathway?

Answer 9

The cleavage and activation of caspase 3.

Question 10

What is the outcome of the TNF receptor signaling pathway when levels of TRAF2 and RIP are higher than FADD?

Answer 10

The cell stimulated by TNF-α will survive.

Question 11

What is the role of IκBα in the TNF receptor signaling pathway?

Answer 11

IκBα inhibits NFκB by retaining it in the cytosol until degraded.

Question 12

Fill in the blank: The proteolytic processing of TNF-α releases a ______ signaling molecule.

Answer 12

[185-amino-acid]

Question 13

What type of proteins do caspases cleave during apoptosis?

Answer 13

Cysteine–aspartate proteases.

Question 14

What is the function of the protein receptor interacting protein (RIP) in the survival pathway?

Answer 14

It binds to TRADD and participates in the phosphorylation cascade.

Question 15

What is a potential therapeutic target for cancer treatment regarding apoptotic signaling?

Answer 15

Blocking the function of anti-apoptotic proteins.

Question 16

What is the significance of the death-inducing signaling complex (DISC)?

Answer 16

It activates caspase 8, which then activates executioner caspase 3.

Question 17

True or False: The TNF receptor signaling pathway includes only pathways leading to cell death.

Answer 17

False

Question 18

What is the consequence of the phosphorylation of IκB by IKK?

Answer 18

The degradation of IκBα, leading to NFκB activation.

Question 19

Fill in the blank: The mature form of caspase 3 is a ______ complex.

Answer 19

[p17p12]2 heterotetramer

Question 20

What is the role of the Fas receptor in the immune system?

Answer 20

It regulates apoptosis in B and T lymphocytes.

Question 21

What happens when procaspase 8 is activated?

Answer 21

It initiates a proteolytic cascade leading to cell death.

Question 22

How do neurodegenerative diseases relate to apoptotic pathways?

Answer 22

They may be caused by increased activation of apoptotic pathways leading to cell death.

Question 23

What is the primary function of NFκB in cell survival signaling?

Answer 23

To activate transcription of anti-apoptotic genes.

Question 24

What is apoptosis?

Answer 24

Programmed cell death in which a cell causes its own death and lysis.

Apoptosis is a crucial process for maintaining cellular homeostasis and preventing the survival of damaged cells.

Question 25

What is the role of the death domain (DD) in TNF receptors?

Answer 25

A region in the cytoplasmic tail of TNF receptors that functions as a protein–protein interaction module. ## Footnote The death domain is essential for signaling pathways that lead to apoptosis.

Question 26

What are cysteine–aspartate proteases (caspases)?

Answer 26

A class of proteins that initiates a proteolytic cascade leading to protein degradation and cell death. ## Footnote Caspases are key executors of the apoptotic process.

Question 27

What does TNF receptor–associated death domain (TRADD) do?

Answer 27

A downstream signaling protein that binds to TNF receptors in the absence of SODD proteins, regulating apoptosis. ## Footnote TRADD is crucial for the transmission of apoptotic signals.

Question 28

What is the function of the Fas-associated death domain (FADD)?

Answer 28

A protein complex that binds with TRADD as part of the cell death signaling pathway. ## Footnote FADD acts as an adaptor protein in the apoptotic signaling cascade.

Question 29

What is the death effector domain (DED)?

Answer 29

A protein–protein interaction module that enables the TRADD–FADD complex to bind with procaspase 8 as part of the cell death pathway. ## Footnote DED is essential for the activation of initiator caspases.

Question 30

What role does TNF receptor–associated factor 2 (TRAF2) play?

Answer 30

A protein complex that binds with TRADD as part of the cell survival pathway alternative to apoptosis. ## Footnote TRAF2 helps promote cell survival under certain conditions.

Question 31

What is the function of receptor interacting protein (RIP)?

Answer 31

A protein recruited to the TNF receptor complex to bind with the TRADD–TRAF2 complex as part of the cell survival pathway. ## Footnote RIP is involved in signaling pathways that prevent apoptosis.

Question 32

Why do cells have both apoptotic and survival pathways?

Answer 32

To provide a 'toggle switch' to kill or rescue the cell quickly, depending on stimuli. ## Footnote This mechanism allows cells to adapt to changing conditions and maintain homeostasis.

Question 33

True or False: Apoptosis is beneficial to the organism as a whole.

Answer 33

True. ## Footnote Apoptosis prevents damaged or inappropriate cells from surviving, contributing to overall health.

Question 34

Fill in the blank: The key activating signal in the TNF receptor signaling pathway occurs downstream of _______ binding.

Answer 34

[TNF-α] ## Footnote TNF-α binding initiates the signaling cascade that can lead to either cell survival or apoptosis.

Question 35

What is the purpose of having opposing cell death and survival pathways in the same cell?

Answer 35

To quickly adapt to the quantity and quality of stimuli, allowing for rapid decisions about cell fate. ## Footnote This flexibility is crucial in responding to environmental changes.