Autophagy Flashcards
Describe the autophage pathway
PI3K –> AKt –| TSC1/2 –| Rheb –> mTOR1 –| autophagy
how many forms of mTOR are there
2
When does autophagy occur
Starvation
Cellular Stresss
Developmental and structural Remodelling
Removed damaged cytoplasmic components
What 2 things can activate AMPK
Metformin
Resveratenol (grape skins)
What does ULK1 phosphorylate in the initiation of autophage
Components of the PI3KC3 complex
What occurs in the nucleation stage of autophagy
vpo34 or PI3KC3 complex phosphorylates PI3P –> PI3P is alipid that trafficks proteins to the isolation membrane
Beclin-1 is a key scaffold protein of the isolation membrane
How is LC3 alteredt
It has a lipid attached to it via atg3 and atg7 –> these lipids are eseential and knockout prevents the formations of autophagosomes.
LC311 is a crucial part of the autphagosome membrane
How does mTOR inhibit autophage
inhibits phosphorylations in the initiation complex
How does AMPK trigger autophagy
1) Phosphorylaiton of ULK1
2) Phosphoryation of Raptor ( A component of mTOR)
3) Phosphorylates TSC2 –> this causes inhibition of mTOR
How is ULK1 normally activated
Starvation or nutrient deprivation –> mTOR moves away from ULK1 –> unmasks ULK1 kinase activity –> FIP200 phosphorylated and Atg proteins are recruited to the autophagosome site.
What phosphorylations are inhibitor on ULK1
Phosphorylations by mTOR and on Atg13
Roles of autophagy in cancer
1) Can be a cell survival mechanism
2) Method of caspase-independent cell death
3) Arsenic trioxide can cause a selective autophagosome degradtion of oncogenic fusion proteins e.g. bcr-abl and Pml-Rar
What do we want to do autophagy in cancer
Some cancers are addicited to autophagy i.e. Ras driven cancer –> hence inhibitoin of autophagy can increase the sensitivity of tumour cells to cytotoxic drugs
Name an autophagy inhibitor
Gossypol
Did gossypol have good effects
1) Caused pro -survival autophagy in breast and cervical hela cancer cells
BUT cause autophagic death in glioma cells!
What are the 3 criteria to prove a cell dies from autophage
1) Cell dies without apoptosis
2) iIncrease in autophagic flux
3 ) autophagy inhibited with autophagy inhibitors
DISCUSS THE BH3 MIMETIC AND AUTOPHAGY DRUG USED IN OVARRIAN CANCER CELLS
Obatoclax (A BH3 mimetic) accumulated in lysosomes during treatment and alkalinised them and inhibited the end stage of autophagy hence stopped sucesful treatment
Name inhibitors of mTOR
Rapamycin! / Everolimus
what can phosphorylate Beclin-1
DAPK
What p53 target can promote autophagosome formations
DRAM
Name some autophagy inhibitors
1) Hydroxychloroquine –> Disrupts lysosomal functional2
2) Lucanthone –> traditionally used to treat Schistosomiasis –> also disrupts lysosomal function and inhibit autophage –> made breast cancer cells 10x more potent
3) Lys 05 –> a water soluble compound that can accumulate ready in the lysosome!
What therapy has been shown to induce apoptosis and necrosis
Photodynamic therapy!
What are the molecules called that can induce Lysosomal Membrane Permeabilisation
Lusosomotropic molecules e.g. Hydrochloroquine !!
Most of these molecules are weak bases that become trapped in the lysosome and increases its leakiness
Why do lysosomotropic molecules have great potential
Because they dont rely on other pathways!
What protein can inhibit LMP
HSP70 and this protien is overexpressed in many cancers!!
