Biology of Ageing 2

Question 1

Name a cellular component that can’t be degraded by autophagy

Answer 1

Genomic DNA

Question 2

Describe an autophagolysosome

Answer 2

When autophagosome fuses with lysosome, it becomes a one layered membrane that is dark-coloured on electron micrograph because of dense material

Question 3

Why would autophagy need to degrade lysosomes?

Answer 3

Lysosomes seal enzymes inside, if there was a lysosomal disease the membrane could be damaged releasing these degradative enzymes

Question 4

What are AMPK and mTORC1?

Answer 4

Both kinases

Question 5

What triggers AMPK and mTORC1 activation and what is the outcome?

Answer 5

Under starvation and stress AMPK is turned on and initiates autophagy by phosphorylating ULK1

In the presence of nutrients, growth factors & amino acids, mTORC1 phosphorylates ULK1 inhibiting it from initiating autophagy

Question 6

What physiological conditions promote autophagy and why?

Answer 6

When a cell is under stress or starvation, autophagy is increased, and other systems are shut off

Autophagy removes toxic or obsolete proteins and organelles and recycles the degradation products for use as sources of energy and metabolites in anabolic pathway

Question 7

What is another function of AMPK?

Answer 7

Stimulates the insulin-independent glucose transporter = GLUT2

Question 8

What would glucose starvation cause?

Answer 8

Activation of AMPK because ATP levels would be low and AMP would be high

AMPK would phosphorylate ULK1 initiating autophagy

Question 9

How many AMPKs do we have vs yeast?

Answer 9

Humans = AMPK 1 & 2 so would need a double KO to inhibit the function

Yeast = 1 AMPK

Question 10

What are the sites on ULK1 that AMPK phosphorylates?

Answer 10

Ser 317 & Ser 777

This is in response to glucose starvation
No glucose = AMPK phosphoylation occurs

Question 11

How does mTORC1 prevent autophagy?

Answer 11

Disrupting the ULK1-AMPK interaction by phosphorylating the Ser 757 on ULK1

Question 12

What is rapamycin?

Answer 12

mTORC1 inhibitor = enhances the interaction of endogenous ULK1 and AMPK

Rapamycin increases autophagy activity

Question 13

What does TSC1 do?

Answer 13

TSC1 is the upstream inhibitor of mTROC1
KO of TSC1 causes hyperactivated mTORC1 that is INSENSITIVE to nutrient availability

Question 14

How does ULK1 iniate autophagy?

Answer 14

ULK1 phosphorylates LC3

Which is necessary for LC3 to conjugate and modify the autophagosome membrane

Question 15

Where is mTOR found?

Answer 15

Cytoplasm not plasma membrane

Nutrient signal is passed through the presence of whether there are amino acids in the lysosomes or not

Question 16

What does metformin do?

Answer 16

Activates AMPK but not sure by what mechanism

Question 17

Why is it beneficial to suppress mTOR to a certain degree?

Answer 17

mTOR promotes anabolic signalling
Slowing this down means the rate of synthesis can also be slowed, so there is more time for the checkpoints to check allowing the quality control to increase

Question 18

Why are dogs considered a good ageing model?

Answer 18

They live with us so are exposed to a similar environment leading to a similar microbiome

They have a shorter lifespan than us so a quicker model to observe

Rapa has already been tested on dogs

Question 19

What was the outcome of calorie restriction?

Answer 19

20% calorie restriction increased both female and male lifespan

But 40% CR had a detrimental effect on both, but more severely on females, killing them earlier

Question 20

What are the important signalling pathways to study?

Answer 20

Evolutionarily conserved nutrient signalling pathways that regulate longevity

[insert examples]

Question 21

What causes Laron syndrome?

Answer 21

Deficiency in growth hormone receptor = prevents their bodies from properly using the hormone

Question 22

What levels of GH and IGF-1 do people with Laron syndrome have?

Answer 22

They have normal or high levels of GH
Low levels of IGF-1

Question 23

What is the role of IGF-1?

Answer 23

Normally helps growth hormone (GH) promote the growth of bones and tissues

GH causes IGF-1 release

Question 24

What is the GH-IGF1 axis?

Answer 24

GH is released from the pituitary
Binds to GHR on the liver
Liver releases IGF-1

Question 25

What is a benefit of laron syndrome?

Answer 25

Protects from some age-related syndromes

Growth hormone receptor deficient subjects display lower serum glucose, insulin, blood pressure, smaller cardiac dimensions, similar pulse wave velocity etc

Conclusion: GHRD have normal or improved levels of CVD risk factors compared to their relatives

Question 26

What is a daf-2 mutants?

Answer 26

Mutation in the insulin-like growth factor receptor (IGFR) in WORMS

Loss-of-funciton mutation

This causes daf-2 mutants to be long-lived so increases the proportion of time spent in a frail state compared to WT