Insulin Signalling

Question 1

What is leprechaunism?

Answer 1

Usually fatal within two years of life
Big ears, large hands and feet
Decreases amount of subcutaneous fat and muscle mass is seen
Hair overgrowth

Question 2

What is Rabson Mendenhall syndrome?

Answer 2

Skin and teeth abnormalities
Hair overgrowth
Pineal Hyperplasia

Question 3

Where is insulin made?

Answer 3

In the beta cells of islet of langerhans in the pancreas

Question 4

What are the immediate and long term effects of insulin?

Answer 4

Immediate = glucose uptake from the blood in to muscle cells and adipocytes (1 minute)
Longterm = increased expression of liver enzymes that synthesis glycogen and of adipocytes that synthesise triacylglycerols (2 hours)

Question 5

Describe the steps of how insulin is matured

Answer 5

It undergoes proteolytic cleavage and is held together by sulfide bridges
proinsulin -> insulin

Question 6

What does insulin result in?

Answer 6

IRS activation

Question 7

What is IRS?

Answer 7

Insulin receptor substrate
Contains a phosphotyrosine binding domain (PTB)
Highly phosphorlyated by the insulin receptor
Then acts as a docking site for many other proteins eg GRB2

Question 8

What does GRB2 activate?

Answer 8

The RAS pathway

Question 9

What two pathways does insulin signalling use?

Answer 9

Ras Pathway

Ras Independent signalling pathway

Question 10

Describe the steps in the Ras independent signalling pathway

Answer 10

1) Insulin binds to receptor = autophosphorylation
2) IRS binds
3) PI3 kinase binds to IRS and phosphorylates so PI3 kinase is recruited to the membrane
4) It then phosphorylates