Intracellular signalling

Question 1

What is the most abundant enzyme linked cell surface receptor?

Answer 1

receptor tyrosine kinases (RTK)

Question 2

To activate a RTK….

Answer 2

To activate a receptor tyrosine kinase the ligand usually has to bind simultaneously to two adjacent receptor chains – forming a dimer and because of intrinsic tyrosine kinase activity, becomes auto-phosphorylated.

Question 3

What does the PI3K pathway regulate?

Answer 3

The PI3K pathway regulates cell growth and survival (inhibition of apoptosis)

Question 4

When is Ras active and inactive?

Answer 4

Ras is inactive when GDP is bound, active when GTP is bound

Question 5

Which pathway does insulin use?

Answer 5

PI3K

Question 6

What are the effects of insulin on the cell?

Answer 6

inhibits gluconeogenesis and glycogenolysis
induces translocation of the glucose transporter to the membrane (so glucose can be transported inside the cell)
stimulates amino acid uptake and protein synthesis
stimulates lypid synthesis and inhibits lipid metabolism

Question 7

What can effector proteins do?

Answer 7

Signals are transduced and amplified and finally integrated by an “effector protein”
Effector proteins can translocate into the nucleus to modulate gene expression
Modulation of gene expression is accomplished by binding of the effector protein (ex. transcription factor) to “signal response element” on gene promoters