Lecture 18: Autophagy

Question 1

What type of autophagy is the model used?

Answer 1

Macroautophagy

Question 2

What is needed to drive autophagy?

Answer 2

K63 ubiquitin chains

Question 3

What labels the isolation membrane?

Answer 3

LC3

Question 4

What cargo receptor is key and why?

Answer 4

p62 receptor bridges between ub and LC3 on the isolation membrane to pull them together

Question 5

What do adaptor proteins like p62 have to be able to do?

Answer 5

Bind and recognise LC3 and ubiquitin

Question 6

Where is p62’s ubd?

Answer 6

C terminus

Question 7

What domain binds LC3?

Answer 7

LIR domain

Question 8

What is another adaptor molecule with LIR and UBD?

Answer 8

NDP52

Question 9

Where is LC3 located?

Answer 9

Autophagosome

Question 10

What do growth pathways and low metabolism do?

Answer 10

inhibit and activate autophagy respectively

Question 11

What does the ULK1 complex do?

Answer 11

induces localisation of beclin-1/Vps34 complex to the isolation membrane.

Question 12

What does vps34 do?

Answer 12

Produces PIP3 which, via WIP induces membrane elongation

Question 13

What happens after the initial membrane elongation?

Answer 13

two ubiquitin like reactions take place to further elongate the isolation membrane and to recruit cargos ATG5/12/16 and ATG8/LC3

Question 14

How are autophagosomes trafficked?

Answer 14

LC3 and dynein traffick a mature autophagosome to the minus end of the mocrotubule, towards the microtubule organising centre.

Question 15

What happens to the fully formed autophagosome?

Answer 15

It fuses with a lysosome to form an autophagolysosome

Question 16

What happens to the material sequestered in the autophagolysosome?

Answer 16

It is degraded and released into the cytoplasm for use in cellular processes including protein biosynthesis

Question 17

Give a definition of autophagy

Answer 17

It is a cell survival pathway that is required to keep cells healthy by degrading damaged organelles and eliminating invading pathogens.

Question 18

What diseases is autophagy implicated in?

Answer 18

it can be disregulated in Crohn’s, cancer and neurodegeneration.

Question 19

Where have isolation membranes been shown to ermerge from?

Answer 19

the omegasome of the ER

Question 20

What is required for autophagosome formation

Answer 20

localisation of ATG14L to the ER.

Question 21

What role could ESCRT proteins have?

Answer 21

Might be involved in autophagosome separation from the ER.

Question 22

What accumulates?

Answer 22

ULK complex at the PI3P positive omegasome and associates with it until it reaches a threshold size.

Question 23

What happens to the ULK?

Answer 23

When the isolation membrane has reached a sufficient size, ULK dissociates from the omegasome and there is autophagosome closure

Question 24

What is the recruitment of ULK mediated partly through?

Answer 24

ATG13

Question 25

What accumulates at ER-mt sites upon starvation and how was this shown?

Answer 25

ATG14L through fluorescent and immuno fluorescent electron microscopy.

Question 26

What is also present at the ER-mt contact point?

Answer 26

ATG5

Question 27

What are physical contact sites between the ER and mt required for?

Answer 27

ca2+ signalling, lipid transfer between the two organelles and mt fusion

Question 28

How exactly is ATG14L recruited to the ER-mt contact site?

Answer 28

the ER resident SNARE protein 17 binds to it and recruits it there.

Question 29

How is the omegasome identified? Where does this come from?

Answer 29

by the presence of double FYVE containing protein 1 (DFCP1). The golgi.

Question 30

What is also recruited to the omegasome?

Answer 30

WIPI2

Question 31

Where is further membrane obtained from?

Answer 31

The golgi.

Question 32

What controls the fusion between autophagosomes and MVBs and lysosomes?

Answer 32

VAMP3 and VAMP8 respectively.