8. Apoptosis & Autophagy

Question 1

Activation of PI3K causes…

Answer 1

Phosphorylation and inactivation of BH3-only proteins eg. Bad and Caspase 9

Question 2

Autophagy

Answer 2

Degration of protein aggregates and organelles. Induced by starvation or stress.

Question 3

Phases of autophagy: Initiation

Answer 3

Formation of a preautophagosomal membrane, leading to an isolation membrane (phagophore)

Question 4

Phases of autophagy: Elongation

Answer 4

Phagophore elongates around target.

Question 5

Phases autophagy: maturation

Answer 5

Creation of a autophagosome

Question 6

Phases of autophagy: docking and fusion

Answer 6

Fusion of autophagosome with lyzosome.

Question 7

Last phase of autophagy

Answer 7

Vesicle breakdown and degradation.

Question 8

Beclin-1

Answer 8

Involved in initiation.

Question 9

LC3

Answer 9

Involved in elongation.

Question 10

mTOR and PI3K in autophagy

Answer 10

Prevents autophagy.

Question 11

Three types of autophagy

Answer 11

Microautophagy, macroautophagy, chaperone-mediated autophagy.

Question 12

Selective autophagy

Answer 12

Cargo are recognized through specific receptor proteins and targeting to autophagocytic proteins as Atg10 LC3.

Question 13

Results of autophagy

Answer 13

Can result in cell survival of starved cells. Alternatively cell death.

Question 14

Inducers of autophagy

Answer 14

Starvation, GF-deprivation, oxygen shortage, IR, chemotherapy.

Question 15

Autophagy and apoptosis regulatory relationship.

Answer 15

Mutally inhibitory but can share upstream activator.

Question 16

Ways for autophagic cytoprotection

Answer 16

Restoring metabolic homeostasis, removal of protein aggregates and harmful organelles.

Question 17

Ways for autphagy-mediated cell deaths

Answer 17

Self-destruction, cellular atrophy.

Question 18

Hallmarks of autophaic cell death.

Answer 18

Membrane blebbing, no DNA damage, increased number if autophagic vesicles, caspase independent.

Question 19

LC3 puncta

Answer 19

Indicative of autophagic initiation

Question 20

Beclin-1 regulation

Answer 20

Regulated by Bcl-2 proteins by binding and sequestering Beclin-1 throigh Beclin-1 BH3. BH3-only proteins can bind and sequester Bcl-2 and induce autophagy.

Question 21

Autophagic tumor supression

Answer 21

Autophagy can be an adaptation to limited nutrients in tumors but can be detrimental to tumor cells.

Question 22

Tumor initiation vs. progression

Answer 22

Autophagy can limit tumor initiation by clearing damaged proteins and organelles. In contrast it can also promote further tumor growth.