Cell bio exam 4 - autophagy

• Proteasome

• short

• monomers

• Autophagy

• long

• oligomers/monomers

• ubiqutin

PROTEIN NEEDS TO BE REMOVED DUE TO DAMAGE OR REGULATION OF ACTIVITY

• ______ - direct degradation

  • ____ lived proteins

  • misfolded _____

• _____ - delivery to lysosome

  • ____ lived proteins

  • misfolded _______

• Both are tagged with _____

• Autophagy → delivers to lysosome

• Self eating 

read and comprehend

WHEN DO WE DO AUTOPHAGY?

Purpose of autophagy

• nutrient and energy homeostasis

• removal of damaged organelles

• removal of aggregate proteins

• removal of intracellular pathogens

  Discovery of this double membrane structure lead to a Noble Prize

Macroautophagy

• autophagosome

• lysosome

  Microautophagy

  Chaperone Mediated Autophagy (CMA)

3 TYPES OF AUTOPHAGY

_________

• molecules are enveloped by a membrane to form ______

• membrane fuses with ______

  _______

• small debris are sequestered into lysosome

  _______

• proteins are transported through a channel

Phagophore

Cargo; autophagosome

endosome

lysosome

PROCESS OF AUTOPHAGY

1. _______ or isolation membrane forms from membrane

2. _____ is brought to ______

3. Autophagosome fuses with _____ (amphisome)

4. Amphisome fuses with _____ (autolysosome)

SPECIALIZED

• isolation membrane (IM)

• PI3P

• VPS34

• ATG9

• LC3

FORMING THE PHAGOPHORE REQUIRES _____ MEMBRANE

UNKNOWN WHERE MEMBRANE FOR PHAGOPHORE ORIGINATES

Phagophore formation-

• All autophagosomes start as an ________

• Membrane for IM could come from Golgi, endosomes, ER, mitochondria associate membrane (MAM) interface

MEMBRANE IS TAGGED IN SEVERAL WAYS TO FORM THE PHAGOPHORE

• Complex mechanisms enable formation of autophagic vesicle

• Components of mechanism:

  • _____

  • _____ complex

  • _____ - membrane receptor

  • ____ - autophagy receptor

• PI to PI3P

VPS34 PHOSPHORYLATES PI (PHOSPHOTIDYLINOSITOL) TO PI3P

(phagophore formation)

• Vps34 is phosphotidylinositol kinase (PI3K)

  • each version of PIP has a different kinase

  • Turns_______

• PI3P is sensed by other proteins

PI3P → phosphorylates things

• PAS

• autophagosomes

ATG9 BRINGS NEW MEMBRANE TO AREAS TAGGED WITH PI3P

(phagophore formation)

• ATG9 containing vesicles bud from source membrane

• Vesicles assemble into preautophagosomal structure (PAS)

• ______ forms isolation membrane

• ATG9 senses PI3P to bring new membrane to forming _____

***Senses PI3P to bring more membrane, growing the autophagosome 

• PE; LC3

• autophagosome

LC3-II IS A PHOSPHOLIPID TAG FOUND ONLY IN AUTOPHAGOSOMES

(phagophore formation)

• LC3-II is lipidated form of LC3-I

• lipidation is when ____ is added to ____

• LC3-II is a molecule used to “tag” PE

• Found only in ______

• PE part of LC3-II can be inserted to membranes to allow ‘tag’ to be associated with membrane

*****

• Add lipid to LC3-I to make LC3-II 

• II is only found on autophagosomes 

• This is the part that is actually becomes an autophagosome 

• TOR

• autophagy

• insulin and amino acids

• Class III PI3K (kinase)

• ATG

SIMPLIFIED AUTOPHAGY REGULATION

induction-

• Starvation induced autophagy

• ____ complex inhibits autophagy

  • anything that inhibits TOR will activate ______ and vice versa

  • ______ activate TOR

• _______ activates autophagy

• ____ proteins - autophagy related

  • work with kinase to form protein complexes

• Insulin and amino acids activate TOR 

• ubiquitin

• LC3II

• auotphagosome

CARGO IS LOADED INTO PHAGOPHORE AND BECOMES THE ISOLATION MEMBRANE

MITOPHAGY

• Damaged mitochondria are tagged with _____

• Ubiquitin recognizes _____ (potentially using an adaptor protein)

• Mitochondria is loaded into the _____

• Mitochondria are tagged with ubiquitin 

• Ubiquitin recognized LC3II

• Because we have LC3II which is only present in autophagosomes… it finds the mitochondria and envelopes it so it can be destroyed 

• Aging

• Neurodegeneration

• Infection

• Cancer

• Neurodegeneration

• Infection

• Cancer

AUTOPHAGY HAS CONSEQUENCES FOR MANY DISEASES

Pros-

• _____ - removes damaged organelles

• _______ - prevents accumulation of aggregate proteins

• ______ - this is one of the way that cells get rid of viruses and bacteria that get inside

• _____ - removes damaged organelles

Cons-

• _____ - accumulation of autophagic vesicles may be involved in AD

• _______ - some bacteria have evolved to subvert the system for their lifestyle

• ______ - can help cancer cells resist cancer drugs and survive with low nutrients

• Phagophore

• Cargo

• autophagosome

• endosome; amphisome

• lysosome; autolysosome

AUTOPHAGY PATHWAY SUMMARY

• _____ forms

• ____ is targeted to phagophore

• Phagophore membrane expands to encapsulate cargo (now called _____)

• Autophagosome fuses with _____ to form ______

• Amphisome fuses with _____ to form ______

• PI3P

• ATG9

• LC3-II

• autophagosome

• lysosome

AUTOPHAGY “SPECIAL MEMBRANE” SUMMARY

• Autophagy starts by making phagophore and tagging it with modified phospholipids allowing 2 things to occur:

• _____ - modified PI

  • allows ____ to recognize the phagophore and bring new membrane to expand the autophagic membrane

• _____ - modified PE

  • allow adaptors to recognize phagophore and bring “cargo” that will be transported by the completed _____ to the _____.

• autophagy increases (disinhibition) 

• Autophagy decreases 

• More autophagy 

• Less autophagy 

What happens when you block something- 

• Block TOR → _______

  • TOR inhibits ATG9, which is required for autophagy 

• Block ATG9 → ______

  • ATG9 is the protein that allows new membranes to be brought in. If its blocked, you cannot bring in new membrane for it to grow 

• Block Insulin → _____

  • Insulin activates TOR, which inhibits ATG9 and autophagy 

• Block P62 → _____

  • If you cannot recognize the cargo, you cannot destroy it