autophagy

Question 1

what is macro autophagy

Answer 1

→ a mechanism to digest intracellular material
-> exchange in cytosol → engulfs into cell

Question 2

why do cells need degredation

Answer 2

• homeostasis - was to rid of damaged components
• signalling - changing protein composition
• reprogramming cells
• removing damaged components
• recycling nutrients

Question 3

ubiquitin system of degredation

Answer 3

• proteosome - certain proteins in cytosol that target degradation
• proteosome recognises cargo protein → degradation

Question 4

different types of autophagy

Answer 4

• macroautophagy
• chaperone autophagy
• microautophagy

Question 5

chaperone autophagy

Answer 5

receptor on surface of lysosome that recognise target proteins with spectific amino acids

Question 6

microautophagy

Answer 6

direct engulfment of cytoplasmic cargo at a boundary membrane by autophagic tubes, which mediate both invagination and vesicle scission into the lumen

Question 7

compare proteasome, macroautophagy and chaperone mediated autophagy

Answer 7

proteasome = no lysosomes and targets individual proteins
macroA = targets many proteins simultaneously
chaperone mediated = lower capacity, targets one protein at a time, specific subset targets

Question 8

functions of macroautophagy

Answer 8

nutrient recycling
- upregulated during cell starvation -> smaller

cellular remodelling
- erythropoisis = loss of nucleus/other organelles
- remove sperm-derived mitochondria = rid of male mito = so dont have double

removal of damaged components
- mitochon, induction of autophagosomes etc

Question 9

dietary restriction hypothesis

Answer 9

eating less -> live longer?
constant diet = yes e.g eat2 inhibition
fall off = no

Question 10

how can autophagy target bacteria

Answer 10

trap bacteria in cytosol as a back up mechanism

Question 11

how can autophagy be used in disease

Answer 11

• cancer - inhibit autophagy
• aging - boost autophagy
• pathogens - mechanisms for survival

Question 12

how to make an autophagosome

Answer 12

• yeast - useful model organism
  
  • one vacuole inside cell
  • take mtuant where you dont have enough proteases - degradation activity is compromised - vacuole fills with vesicles - autophagosomes form

Question 13

use of identifying the Atg genes

Answer 13

• disruption of autophagy to investigate its functions
• start on dissecting how the machinery works
• observed of autophagy in live cells

Question 14

groups of autophagy machinery

Answer 14

• kinase - turns process on and off
• P13K
  
  • defines where phagosomes form
• complex module
  
  • addition of new lipids
  • fuse with vesicles
  • expand membrane
• snares
  
  • recognise autophagosomes and allows fusion

Question 15

what is selective autophagy

Answer 15

1. ubiquitin tag
2. adaptor proteins
   
   • scafolding
   • ubuqitn binding domain and atg8 protein domain (lipidated and encorporated into the membrane)
   • adaptors → bind ubuiqitn and agt8 and drag into the membrane

Question 16

Functions of autophagy:

Answer 16

• recycling nutrients
• damaged protein
• cellular remodelling
• intracellular pathogen removal

Question 16

Functions of autophagy:

Answer 16

• recycling nutrients
• damaged protein
• cellular remodelling
• intracellular pathogen removal

Question 16

Functions of autophagy:

Answer 16

• recycling nutrients
• damaged protein
• cellular remodelling
• intracellular pathogen removal

Question 17

proteinopathies in neurodegeneration

Answer 17

• huntington and parkinsons diseases have ubuquitin aggregates found in brain

Question 18

cause of huntingtons disease

Answer 18

• monogenic
• polyglutamine (polyQ) expansion in Huntingtin protein = amplification of gene, causing protein aggregation
• more glutamines = earlier onset

Question 19

function of huntington protein

Answer 19

• protein/neurone maintenance
• accumulation of protein = forms aggresomes = clump

Question 20

mechanisms of toxicity during protein misfolding

Answer 20

• loss of normal function
• toxic oligomer
• aggresomes
• adapter sequestration
• proteosomal damage

Question 21

what is parkinsons

Answer 21

• affects dopaminergic neurones
• Main neuropathology is aggregates of α-synuclein (Lewy Bodies)

Question 22

mutation causing parkinsons

Answer 22

a-synuclein mutations
-> α-syn normally degraded by chaperone-mediated autophagy, if not it accumulates in cytosol and blocks lysosomes from degrading

Question 23

how can mitochondrial dysfunction contribute to parkinsons

Answer 23

- parkinsons may be caused by mitochondrial-derived oxidative damage - damaged mitochondria can accumulate - mitochondria are the main source of Reactive Oxygen Species (ROS) - ROS damages cellular components

Question 24

enzymes regulating mitophagy

Answer 24

PINK1 - mitochondrial kinase - LOF - linked with early onset PARKIN - Cytosolic E3 ubiquitin ligase = adds ubiquitin - AR - early onset

Question 25

function of mitochondrial enzymes

Answer 25

- kinase and u ligase allow targeting of damaged mitochondria to allow autophagy - without these enzymes you accumulate damaged organelles and products - ROS: Oxidative damage Protein misfolding Damaged organelles

Question 26

role of autophagy in cancer

Answer 26

- autophagy is tumour suppressive and prevents dna damage in cells - Autophagy is unregulated in hypoxic, nutrient-poor tumour regions - blocking autophagy causes necrosis / apoptosis

Question 27

beclin1 (Atg6) gene role

Answer 27

- important gene for autophagy - gene that is monoallellically deleted in 40-75% of ovarian, breast and prostate carcinomas

Question 28

what does unregulated autophagy cause

Answer 28

Autophagy is unregulated in hypoxic, nutrient-poor tumour regions

Question 29

what does blocking autophagy cause

Answer 29

necrosis / apoptosis

Question 30

effect of beclin 2 on surface of mitochondria

Answer 30

inhibition of apoptosis and interacts with beclin 1 = death

Question 31

effect of beclin 1

Answer 31

autophagosome formation -> survival

Question 32

what genes are linked to tumour survival via autophagosome formation

Answer 32

vps34 and UVRAG

Question 33

list 2 strategies for autophatic therapy

Answer 33

inhibition of authophagy = increases apoptosis = prevent tumour growth in cancers

Question 34

how does autophagy inhibit apoptosis

Answer 34

Bcl-2 inhibits apoptosis by blocking activation of Bax (and Bak) to prevent MOMP and subsequent release of cytochrome c and other apoptogenic proteins from the mitochondria

Question 35

what affects autophagy activation

Answer 35

genes beclin and bcl2 membrane permeabilisaiton/caspase activation

Question 36

anti-oncogenic autophagy processes

Answer 36

cell homeostasis damage removal reduced ROS/genotoxicity reducing inflammation

Question 37

pro-oncogenic autophagy processes

Answer 37

survival during oxygen/nutrient shortage prevention of apoptosis survival during chemotherapy

Question 38

how do issues with autophagy cause neurodegeneration

Answer 38

impaired autophagosome formation disrupted cargo recognition disrupted lysosomal function autophagic cargo inhibited autolysosome formation autolysosome secretion

Question 39

how does mitophagy contribute to neurodegeneration

Answer 39

ROS, ocidative damage, protein misfolding, damaged organelles -> inhibits mitophagy and ubuquitination of mitochondria => damaged mitochondria accumulate

Question 40

how is autophagy tumour suppressive

Answer 40

decreased damaged organelles, protein toxicity, ROS = less oxidative stress, DNA damage, tumourigenesis

Question 41

how can autophagy be manipulated in huntingtons treatment

Answer 41

induction of autophagy in HD cells cales accelerated breakdown of huntintin aggregates -> neuroprotection

Question 42

how is a-syn normally degraded

Answer 42

chaperone-mediated autophagy