14. Intracellular Signalling Pathways

Question 1

How does agonist-stimulated regulation of adenylyl cyclase work in Gs coupled receptors?

Answer 1

Agonist binds to receptor and changes conformational shape
G protein is activated
GDP is exchanged for GTP on alpha subunit
Alpha subunit binds to adenylyl cyclase and ATP is converted to cAMP

Question 2

How doe agonist-stimulated regulation of adenylyl cyclase work in Gi coupled receptors?

Answer 2

Agonist binds to receptor and changes conformational shape
G protein is activated
GDP on alpha subunit is exchanged for GTP
Alpha subunit binds to adenylyl cyclase and inhibits it
ATP cannot be converted to cAMP

Question 3

What are the 2 parts of cAMP-dependent protein kinase?

Answer 3

R = regulatory
C = catalytic
When cAMP binds to the regulatory subunit, it releases the catalytic subunits

Question 4

How does agonist-stimulated regulation of phospholipase C (PLC) in Gq coupled receptors?

Answer 4

Agonist binds to the receptor
Activates G protein
GDP is exchanged for GTP on alpha subunit
Alpha subunit binds to PLC
Activated PLC hydrolyses PIP2 which splits it into IP3 and DAG
IP3 then binds to IP3 receptor on ER membrane and Ca2+ moves out towards the PKC
Ca2+ binds to PKC which is on DAG