M&R Session 7 (Lecture 7.2)

Question 1

What does cyclic AMP do in the cell once created?

Answer 1

Activates cyclic AMP - dependant protein kinase A

Question 2

What receptors are examples of Gs coupled?

Answer 2

1) Beta - adrenoceptors
2) D1 dopamine receptors
3) H2 histamine receptors

Question 3

What receptors are examples of Gi coupled?

Answer 3

1) Alpha 2 - adrenoceptors
2) D2 dopamine receptors
3) Mu opioid receptors

Question 4

Describe the structure of PKA. What happpens when cAMP binds?

Answer 4

1) Contains R and C subunits (2 of each)
2) R subunits sits within C subunit catalytic site
3) cAMP binds to R subunit causing the two subunits to dissociate allowing the C subunits to activate other proteins

Question 5

What does PLC cleave and generate?

Answer 5

Cleaves PIP2 into IP3 and DAG

Question 6

What are examples of Gq coupled receptors?

Answer 6

1) Alpha 1 - adrenoceptors
2) M1 muscarinic
3) H1 histamine receptors

Question 7

What do IP3 and DAG do after being generated?

Answer 7

IP3 - interacts with IP3R causing calcium release from S.R

DAG - interacts with PKC as a ligand

Question 8

How is positive inotropy brought about in the heart?

Answer 8

1) Adr/Norad acts on beta 1 adrenoceptors
2) GPCR -GP interaction (Gs)
3) GTP for GDP exchange
4) Activation of AC
5) cAMP causes PKA to be activated
6) PKA phosphorylates VOCC allowing Ca2+ infux increasing contractility

Question 9

What does activation of a Mu opioid receptor cause?

Answer 9

1) Activation by morphine
2) Activates Gi
3) Decreases cAMP and increases K+ conductance.
4) Beta gamma subunit inhibits VOCC so no Ca2+ influx.

Question 10

Describe the process of signal amplification in cells.

Answer 10

1) One receptor activated
2) Many G protein interact
3) Generate more cAMP
4) Activate more PKA
5) Target proteins e.g. ion channels, enzymes