Raj Patel L2

Question 1

What are the five main components of apoptotic machinery in mammalian cells?

Answer 1

1) Bcl-2 proteins; antiapoptotic, proapoptotic, BH3 only proapoptotic proteins; 2) Caspases; 3) IAPs; 4) Mitochondria; 5) Death receptors

Question 2

Bcl-2 proteins are found translocated next to immunoglobulin in lymphoma cells. What is the result of this?

Answer 2

High/ectopic expression, resulting in blocked apoptosis

Question 3

What distinguishes proapoptotic Bcl proteins from antiapoptotic?

Answer 3

Antiapoptotic Bcl proteins must posses a BH4 domain which is able to bind APAF1, while proapoptotic cells require only a BH3 domain.

Question 4

Describe the structure of dimerised Bcl-2 family proteins?

Answer 4

Alpha 5 & 6 domains form the pore in the outer mitochondrial membrane.

Question 5

What is the effect of pro/anti apoptotic proteins?

Answer 5

Proapoptotic proteins increase the permiability of the mitochondrial outer membrane

Question 6

What are caspases?

Answer 6

Caspases are cysteine-aspartate specific proteases

Question 7

What is the consensus sequence of a caspase?

Answer 7

DxxD

Question 8

What are the 3 groups/functions of caspases?

Answer 8

Inflammation, Initiation of apoptosis, execution of apoptosis

Question 9

Caspases are synthesised as?

Answer 9

Zymogens

Question 10

Initiator and effector caspases are activated by different mechanisms. Describe this?

Answer 10

Initiators are activated by proximity, where they must be recruited to the adaptor to activate, e.g. activation of caspase 9 requiring formation of the apoptosome. Effector caspases are activated by being cleaved by initiating caspases.

Question 11

What is a death receptor?

Answer 11

A death receptor is a cell surface receptor, which transduces cell death signals

Question 12

How do death receptors recruit caspases?

Answer 12

Death receptors recruit caspases via adapter proteins such as Fas associated death domain (ADD - associated death domain).

Question 13

What are IAPs?

Answer 13

IAPs are inhibitor of apoptosis proteins, which inhibit the caspases until cell death is ready to occur

Question 14

What domain must IAPs include?

Answer 14

BIR (Baculovirus inhibitor or apoptosis repeat), to bind caspases

Question 15

Role of the RING domain in IAPs?

Answer 15

The RING domain binds a substrate which is ubiquitinated by E3 ubiquitin ligase. Promotes IAP auto destruction.

Question 16

What are the two ways in which apoptosis can be induced?

Answer 16

Intracellularly and extracellularly

Question 17

How does extracellular apoptosis induction occur?

Answer 17

Extracellular apoptosis induction occurs via death receptors

Question 18

How can intracellular apoptosis induction occur?

Answer 18

Intrinsic signals are induced from within the cell; programmed cell death, developmental cell death. Can also be triggered by UV, superoxide radicals, DNA damage/p53