signal transduction

Question 1

agonists at GPCRs- drugs

Answer 1

beta 2-adrenoreceptor agonists- salbutamol and salmelterol

u-opioid receptor agonists
-morphine and fentanyl

Question 2

antagonists at GPCRs- drugs

Answer 2

beta adrenoreceptor antagonist
-propranol and atenolol

D2 dopamine receptor antagnosts
-haloperidol and sulpride

Question 3

structure of g protein coupled receptor

Answer 3

• single polypeptide chain
• 7 transmembrane spanning region s
• extracellular N terminal
• intracellular C terminal

Question 4

what 2 sites can a ligand bind to

Answer 4

1) formed by 2-3 of the transmembrane domains

2) in other cases the N - terminal region form the ligand binding site

Question 5

How do GCPRs cause a change in cellular activity?

Answer 5

an activated GCPR must interact with a G protein which is made up of 3 subunits- alpha, beta and gamma

the GPCR-G protein interaction activates the G protein by causing the GDP to be repalced by GTP

the alpha-beta,gamma complex immediately dissociates and each can then interact with effector proteins

this lasts until teh alpha subunit GTPase activity hydrolyses GTP to GDP which causes the affinty of the alpha -GDP and betagamma subunit complex to reform

Question 6

What do Galpha s g proteins do

g alpha i

g alpha q

Answer 6

stimulates adenylyl cyclase

inhibits adenylyl cyclase

stimulates phospholipase C

Question 7

How does the pertussis toxin work

Answer 7

it prevents the Gi proteins from being activated as GDP isnt swapped for GTP- no inhibiton so no regulation

it uncouples Gi preffering GPCRs from mediating signal transduction events

Question 8

how does the cholera toxin work

Answer 8

prevents termination of signalling by Gs-preferring GPCRs leading to long-lasting activation of downstream pathways