Lecture 18: Autophagy Flashcards
What type of autophagy is the model used?
Macroautophagy
What is needed to drive autophagy?
K63 ubiquitin chains
What labels the isolation membrane?
LC3
What cargo receptor is key and why?
p62 receptor bridges between ub and LC3 on the isolation membrane to pull them together
What do adaptor proteins like p62 have to be able to do?
Bind and recognise LC3 and ubiquitin
Where is p62’s ubd?
C terminus
What domain binds LC3?
LIR domain
What is another adaptor molecule with LIR and UBD?
NDP52
Where is LC3 located?
Autophagosome
What do growth pathways and low metabolism do?
inhibit and activate autophagy respectively
What does the ULK1 complex do?
induces localisation of beclin-1/Vps34 complex to the isolation membrane.
What does vps34 do?
Produces PIP3 which, via WIP induces membrane elongation
What happens after the initial membrane elongation?
two ubiquitin like reactions take place to further elongate the isolation membrane and to recruit cargos ATG5/12/16 and ATG8/LC3
How are autophagosomes trafficked?
LC3 and dynein traffick a mature autophagosome to the minus end of the mocrotubule, towards the microtubule organising centre.
What happens to the fully formed autophagosome?
It fuses with a lysosome to form an autophagolysosome
What happens to the material sequestered in the autophagolysosome?
It is degraded and released into the cytoplasm for use in cellular processes including protein biosynthesis
Give a definition of autophagy
It is a cell survival pathway that is required to keep cells healthy by degrading damaged organelles and eliminating invading pathogens.
What diseases is autophagy implicated in?
it can be disregulated in Crohn’s, cancer and neurodegeneration.
Where have isolation membranes been shown to ermerge from?
the omegasome of the ER
What is required for autophagosome formation
localisation of ATG14L to the ER.
What role could ESCRT proteins have?
Might be involved in autophagosome separation from the ER.
What accumulates?
ULK complex at the PI3P positive omegasome and associates with it until it reaches a threshold size.
What happens to the ULK?
When the isolation membrane has reached a sufficient size, ULK dissociates from the omegasome and there is autophagosome closure
What is the recruitment of ULK mediated partly through?
ATG13
What accumulates at ER-mt sites upon starvation and how was this shown?
ATG14L through fluorescent and immuno fluorescent electron microscopy.
What is also present at the ER-mt contact point?
ATG5
What are physical contact sites between the ER and mt required for?
ca2+ signalling, lipid transfer between the two organelles and mt fusion
How exactly is ATG14L recruited to the ER-mt contact site?
the ER resident SNARE protein 17 binds to it and recruits it there.
How is the omegasome identified? Where does this come from?
by the presence of double FYVE containing protein 1 (DFCP1). The golgi.
What is also recruited to the omegasome?
WIPI2
Where is further membrane obtained from?
The golgi.
What controls the fusion between autophagosomes and MVBs and lysosomes?
VAMP3 and VAMP8 respectively.
