Apoptosis

Question 1

Cells have intrinsic apoptosis pathways for suicide without the release of _______.

Answer 1

Cytosolic contents.

Question 2

Apoptosis involves activation of cellular ____ that cleave cellular proteins.

Answer 2

Caspase proteases

Question 3

Describe the difference between necrosis and apoptosis.

Answer 3

Necrosis is cell repture, and cellular contents pour out leading to an inflammatory response. In apoptosis however, the cell remains intact, the cell is dismantleda dn packaged into apoptotic bodies, cellular contents stay within vesicles, and are absorbed by macrophages to be recycled.

Question 4

Cell death by apoptosis is a highly regulated process. Give three main parts of it.

Answer 4

1. Mild convolution, chromatin compaction and margination and condensation of cytoplasm.
2. Breakup of the nuclear envelope, nuclear fragmentation, blebbing and cell fragmentation.
3. Phagocytosis.

Question 5

Apoptotic stimuli triggers DNA degrading __________ that cleave DNA between nucleosomes.

Answer 5

Nucleases.

Question 6

What does caspases stand for?

Answer 6

Cysteninyl aspartate-specific proteinase

Question 7

What is the role of initiator caspases in apoptosis and name three of them.

Answer 7

Process and activate effector caspases.

Caspase-9: Intrinsic pathway

Caspase-8 and 10: Extrinsic pathway

Question 8

What is the role of effector (executioner) caspases in apoptosis and name three of them.

Answer 8

• Cleave specific cellular proteins leading to apoptosis.
• Digest the proteins of the cell and activate nucleases that degrade DNA and chromatin.

Caspase-3,6,7

Question 9

The intrinsic death pathway is activated by the release of ______ from the mitochondria.

Answer 9

Cyt C

Question 10

List the three pro-apoptotic proteins.

Answer 10

1. Bak
2. Bax
3. Boc

Question 11

List the three pro-survival proteins.

Answer 11

1. Bcl-2
2. Bcl-xl

Question 12

All pro-apoptotic and pro-survival proteins are homologous to ____ and contain these homology domains (BH1, BH2, BH3, BH4).

Answer 12

Bcl-2

Question 13

What is the role of BH3-only proteins.

Answer 13

Regulate pro-survival proteins.

• Regulate activity of the Bcl-2 and Bax/Bak proteins: Bio, Puma, Noxa, Bik, Bmf, Bad, Hrk, and Bid

Question 14

List the three BH3-only proteins.

Answer 14

1. Bad
2. Bim
3. Puma

Question 15

Where do pro-apoptotic members form channels?

Answer 15

In the mitochondrial outer membrane.

Question 16

The Bcl-2 family of proteins control the transport through the __________.

Answer 16

Outer mitochondrial membrane.

Question 17

Pro-surivial proteins close pores of the outer mitochondrial membrane and surprises the release of __________.

Answer 17

Cytochrome C

Question 18

Pro-apoptotic proteins open the channels to release ____.

Answer 18

Cyc C

Question 19

Describe the difference between the intrinsic and extrinsic death pathway in vertebrates.

Answer 19

Intrinsic death pathway is activated by proteins that reside in the mitochondria (Bak, Bax, Bcl-2, Cytochrome C (CytC) and is activated in response to DNA damage, cell stress.

The extrinsic death pathway is activated through cell surface death receptors. It is activated by a direct contact with other cells that direct them to self-destruct by apoptosis.

Question 20

Describe the steps of the intrinsic death pathway.

Answer 20

1. Pro-apoptotic proteins (Bak or Bax) open pores on the mitochondrial membrane.
2. Pro-survival proteins (Bcl-2, Bcl-x) bind to pro-apoptotic proteins (Bak or Bax) and close the pore in the outer mitochondrial membrane.
3. Bad, Bim, Puma displace Bel-2 from Bak or Bax.
4. Bad, Bim, Puma can be activated by cell stress, DNA damage. They release Bak, Bax from their contact with Bcl-2.
5. Bak and Bax oligomerize and open the pore.
6. CytC is release, bids to Apaf-1 and and activates Capase 9, which activates the execution caspases.
7. Trophic factor signaling through Bad.