G Protein Couple Receptors And Second Messenger Signalling

Question 1

7TM receptors

Answer 1

Binds a ligand and transmits a signal to the inside of the cell
Activates a G protein bound to the inner surface of the 7TM

Question 2

life cycle of GPCR signalling

Answer 2

1) ligand binds to 7TMR receptor
2) Conformation change 7TMR activates G protein (GTP binds)
3) G protein dissociates from 7TMR, Ga and Gby can interact with effectors
4) GTP is hydrolysed to GDP and the Ga is no longer active and rebinds Gby
5) effectors can go on to activate other proteins= signal cascades and amplification

Question 3

Gs
Gi
Gq

Answer 3

stimulating (activates adenylyl cyclase)- beta 1 adrenergic receptor
inhibitory (inhibits adenylyl cyclase)
activates PLC

Question 4

what is G protein signalling determined by

Answer 4

the a subunit of the G protein (Gq, Gi, Gs)

Question 5

how does the same GPCR provoke different responses in different cells

Answer 5

different adrenergic receptors have different responses

Question 6

protein kinase mediated phosphorylation in cardiac myocytes

Answer 6

increase calcium influx though voltage gated ion channels
increase calcium release from sarcoplasmic reticulum
increase myosin ATPase activity
increase calcium re-uptake into sarcoplasmic reticulum (promotes more rapid relaxation)

Question 7

protein kinase mediated phosphorylation in bronchial smooth muscle

Answer 7

decrease in calcium influx through voltage gated ion channels
decrease calcium release from sarcoplasmic reticulum
decrease myosin ATPase activity
increase calcium re-uptake into sarcoplasmic reticulum (promotes rapid relaxation)

Question 8

receptor tyrosine kinase

Answer 8

single transmembrane proteins that activate intracellular kinases
important for neuronal development and survival

Question 9

constitutive activity

Answer 9

capacity to phosphorylate itself
the activation of a receptors as well as the production of a second messenger, without the binding of an agonist