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Cell and molecular extras > Lecture 21 Autophagy 1 > Flashcards

Lecture 21 Autophagy 1 Flashcards

1
Q

Define macroautophagy

A

A mechanism to digest IC material

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2
Q

Why do cells need degradation x5

A 
homeostasis 
signalling
removing damaged components
recycling nutrients 
reprogramming cells (differentiation)
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3
Q

Name 2 mechanisms of degradation

A
  • The ubiquitin/proteasome system (UPS)

* Autophagy

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4
Q

Name 3 flavours of autophagy

A

Macroautophagy
Microautophagy
Chaperone-mediated autophagy

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5
Q

Briefly explain macroautophagy

A

autophagosomes fuse to lysosome

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6
Q

Briefly explain microautophagy

A

Lysosome invaginates to capture the cargo material

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7
Q

Briefly explain chaperone-mediated autophagy

A

Specific proteins are unfolded by HSC70 and threaded 1 by 1 threaded via LAMP-2A for degradation by the lysosome

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8
Q

Which pathways are/are not lysosomal

A

Proteasome - not

Macro/chaperone mediated/micro autophagy - is

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9
Q

Which pathways do/do not degrade individual proteins

A

proteasome - individual
macroautophagy - bulk
chaperone-mediated/micro - individual

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10
Q

Which pathway is a major turnover route for short-lived proteins

A

proteasome

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11
Q

Which pathway can remove whole organelles

A

Macroautophagy

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12
Q

Which pathway turns over specific, long-lived proteins

A

Chaperone-mediated autophagy/microautophagy

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13
Q

Molecules released by … can support what

A

the macroautophagy pathway

metabolism

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14
Q

Which pathway has a relatively low capacity

A

Chaperone/micro

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15
Q

Name the 4 functions of macroautophagy

A

Nutrient recycling
Cellular remodelling
Removal of damaged components
Killing IC pathogens

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16
Q

Nutrient recycling:
When is autophagy rapidly unregulated?
This causes…

A

Under nutrient starvation

Causes non-selective bulk degradation of the cytosol

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17
Q

What occurs in cells lacking autophagy vs WT in starvation

A

Death vs the WT which get smaller due as they digest themselves

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18
Q

When do autophagy-deficient mice die

A

during neonatal starvation

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19
Q

Give an example where autophagy is needed for survival

A

Cancer cells in solid tumours

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20
Q

Autophagy is the only mechanism for…

A

the degradation of organelles

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21
Q

Autophagy is essential for forming which cell types?

A

Erythropoiesis (red blood cell differentiation)

Removal of sperm-derived mitochondria in C.Elegans fertilisation

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22
Q

Describe the process of erythropoiesis

A

reticulocyte denucleated

mitochondrial clearance

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23
Q

You only inherit mitochondria from…

A

mother

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24
Q

Why are components removed by autophagy

A

Cellular components accumulate damage over time

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25
Q

examples of when damaged components needed to be removed by autophagy

A

mechanical damage in muscles

damaged mitochondria selectively removed

26
Q

How can mitochondria become damaged

A

CCCP decoupled the mitochondria respiratory train i.e. depolarises the mitochondria

27
Q

What happens to the lysosomal capacity as we age

A

decreases

28
Q

What disease is autophagy related to

A

Neurodegenerative and ageing

29
Q

What causes age-related degeneration

A

Reduced autophagy

30
Q

What cells are most susceptible to damage

A

Long lived neurons

metabolic muscle cells

31
Q

Name the hypothesis associated to autophagy and what it states

A

The dietary restriction hypothesis:

Starvation/exercise leads to increased autophagy which in turn leads to increased damage repair

32
Q

What could starvation prevent according to the hypothesis

A

prevent ageing

33
Q

Eat2 mutant worms vs WT

A

Calorific restricted worms

Live significantly longer vs WT

34
Q

How do we know eat2 mutant worms live longer via an autophagy dependent pathway

A

Removing autophagy in these worms has no affect on dietary restriction

35
Q

What happens to the effect of dietary restriction on life span, the higher up through evolution you go

A

The less the effect is

36
Q

How does dietary restriction increase autophagy

A

If starving, ATP levels drop. AMPK/SIRT1 detect to ATP/AMP levels and activate autophagy and inhibit TORC1 which inhibits autophagy

37
Q

What does TORC1 recongise

A

Torc1 recognises amino acids. If cell is deficient in amino acids, you upregulate autophagy.

38
Q

What pathogens can escape into the cytoplasm

A

TB

Salmonella

39
Q

How are pathogens usually killed

A

Encased in a phagolysosome
Fuses to lysosome
Digestion

40
Q

Why is the cytoplasm favourable for pathogens

A

They use nutrients here to grow

Macrophages cannot detect them

41
Q

How does autophagy play a role in killing IC pathogens

A

Cells recognise the bacteria in the cytosol and targets them for autophagy

42
Q

Effect of inhibiting autophagy in myocardium infection

A

TB bacteria can escape into the cytoplasm and grow unchecked leading to infection

43
Q

Effect of inhibiting autophagy in MRSA

A

They grow less well as autophagy promotes their growth

44
Q

Recycling nutrients causes

How manipulate?

A
  1. to survive starvation
  2. helps cancer to grow

So could inhibit autophagy to prevent cancer yet cells accumulate damage over time so will get mutations if not removed

45
Q

Damaged protein/organelle removal causes

How manipulate?

A
  • Ageing
  • Muscular dystrophy
  • Neurodegeneration
  • Cancer

Increase autophagy in all these cases

46
Q

Cellular remodelling causes

A
  • Erythrocyte differentiation

- Removing sperm-derived mitochondrial

47
Q

Intracellular pathogen removal causes

How manipulate?

A
  • Tuberculosis
  • MRSA
  • viruses

Inhibiting autophagy removes MRSA as cant hide in autophagosomes but makes more susceptible to TB

48
Q

When/what/who were autophagosomes first discovered by?

A

EM
1963
Christian De Duve

49
Q

When/who/how shown autophagy occurred in yeast?

A

1992
Yoshimori Oshumi
- Nitrogen-starved protease deficient S.cerevisiae
- In cells slightly mutated, starving them leads to accumulation of vesicles inside the vacuole

50
Q

How many autophagy genes were identified?

A

1993 Performed genetic screen to identify 15 autophagy genes

51
Q

Identifying the Atg genes allowed?

A
  • Disruption of autophagy to investigate its functions
  • A start on dissecting how the machinery works
  • Observation of autophagy in live cells
52
Q

Describe the 4 steps in the formation of autophagosomes

A
  1. Initiation
  2. Expansion into cup shapes (phagophore) – formed from fats using lipid transport
  3. Cup shape closes (autophagosome)
  4. Fusion with lysosome (autolysosome) using Syntaxin 17
53
Q

How is the organelle made compared to most organelles?

A

Only organelle in the cell to be made de novo – every other vesicle is generated by budding off from the organelles

54
Q

When are autophagosomes upregulated?

A

Starvation

55
Q

Why are autophagosomes easy to visualise with EM?

A

It has 2 membranes

56
Q

Where are autophagosomes formed?

A

At the ER

57
Q

How does selective autophagy occur?

A

Ubiquitination

Protein aggregates

58
Q

How are things targeted to phagosomes

A

Ubiquitination

59
Q

What aids in selective autophagy

A

Adaptor proteins

60
Q

How do adaptor proteins work

A
  • Adaptor proteins have a ubiquitin binding domain on one end and an Atg binding motif on the other end (LC3)
  • This binds and targets specific proteins/organelles e.g. mitochondria to the phagosome
61
Q

Are adaptor proteins vital?

A

No, some proteins directly bind to the Atg8, independent of adaptors

62
Q

Why do ubiquitin protein aggregates accumulate?

A

Removing autophagy means they accumulate ubiquitin protein aggregates

Cell and molecular extras (16 decks)

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