Apoptosis

Question 1

What are examples of the phenotype of cells undergoing apoptosis?

Answer 1

Overall shrinkage in volume of cell and its nucleus; loss of adhesion to neighboring cells; formation of blebs on surface; DNA fragmentation; cytoskeleton collapses; nuclear envelope disassemebes; rapid engulfment of dying cell by phagocytosis (macrophages)

Question 2

What is a marker of apoptosis?

Answer 2

Cytochrome c released from mitochondria

Question 3

Definition of caspase (cysteine aspartyl specific protease)

Answer 3

Proteases that mediate apoptosis

Question 4

What is the importance of cysteine in caspase?

Answer 4

It is in the active site; it targets proteins and cleaves them in their sequence where an aspartic amino acid residue occurs

Question 5

Define procaspase

Answer 5

The inactive precursor of caspases

Question 6

What activates the procaspase to cleave and become active?

Answer 6

Already active caspases

Question 7

Define and give examples of initiator caspases

Answer 7

Caspases that initiate apoptosis. Ex: caspase-8 and caspase-9

Question 8

Define and give examples of executioner caspases

Answer 8

Caspases that destroy the actual targets - executes apoptosis. Ex: caspase-3. Cleaves downstream proteins and inactive endonuclease. Attacks cell adhesion proteins- cells roll up in ball.

Question 9

What is an example of an internal stimuli that could induce apoptosis?

Answer 9

Abnormalities in DNA

Question 10

What is an example of external stimuli that could induce apoptosis?

Answer 10

Removal of survival factors and proteins of tumor necrosis factor family

Question 11

The intrinsic pathway of apoptosis is dependent on what?

Answer 11

Mitochondria

Question 12

The extrinsic pathway of apoptosis is. ?

Answer 12

Mitochondrial independent

Question 13

Describe the extrinsic pathway steps

Answer 13

Extracellular signals bind cells surface death receptors to trigger; Fas binds Fas death receptor; adaptor proteins, FADD and procaspase-8 are recruited; brings death domains together to form DISC; activates caspase-8 or -10; activates downstream executioner caspases (caspase-3)

Question 14

What type of receptor are the death receptors?

Answer 14

Homotrimers; 3 proteins of same type (members of TNF family of proteins)

Question 15

What are the inhibitory proteins that restrain the extrinsic pathway?

Answer 15

Decoy receptors that have ligand binding domain but no death domain so apoptosis is not activated; FLIP = protein resembling initiator procaspase w/ no proteolytic domain so is a competitive inhibitor against procaspase-8 and -10

Question 16

What is a key event in the intrinsic pathway?

Answer 16

Translocation of cytochrome c from the intermediate space of mitochondria - released to cytosol and will bind to adaptor protein to activate procaspase said

Question 17

Describe the steps in the intrinsic pathway

Answer 17

Cytochrome c released from mito binds Apaf1 which forms the apoptosome which activates caspase-9; caspase-9 activates downstream executioner caspases (3)

Question 18

What controls the release of cytochrome c into the cytosol?

Answer 18

Bcl (b cell lymphoma)

Question 19

What are the 2 types of bcl proteins?

Answer 19

1. Pro-apoptotic - promotes release of cytochrome c

2. Bcl2 - anti-apoptotic: pro survival; blocks release of cytochrome c

Question 20

How many domains do the anti-apoptotic Bcl proteins have?

Answer 20

4: BH domains

Question 21

What are examples of pro-apoptotic proteins?

Answer 21

BH123 and BH-3 only protein