G Protein Coupled Receptors

Question 1

Gq

Answer 1

Phospholipase C –> cleavage of PIP2 into DAG and IP3

DAG –> protein kinase C

IP3 –> inc intracellular Ca ++ –> smooth muscle contraction

**makes sense b/c alpha 1 - vasoconstriction and M3 secretions, etc

Question 2

Gs

Answer 2

STIM adenylyl cyclase –> inc cAMP –> protein kinase A –> inc intracellular Ca in heart and myosin light chain kinase activation in smooth muscle

Question 3

Gi

Answer 3

INHIBIT adenylyl cyclase –> dec cAMP –> no activation of protein kinase A

**makes sense b/c alpha 2 is neg feedback, M2 is dec HR and contractility, D2 inhibits indirect path of striatum

Question 4

Which G protein is each adrenergic receptor?

Answer 4

QISSS (“kiss”)

alpha 1 - q
alpha 2 - i
beta 1, 2, 3 - s

Question 5

Which G protein is each muscarinic receptor?

Answer 5

QIQ (“kick”)

M1 - q
M2 - i
M3 - q

Question 6

Which G protein is each dopamine receptor?

Answer 6

D1 - s (for activating direct path of Striatum)

D2 - i (for Inactivating Indirect path of striatum)

Question 7

Which G protein is each histamine receptor?

Answer 7

H1 - q (mucus, permeability, bronchoconstriction, pruritus, pain)
H2 - s (gastric acid - parietal cells inc cAMP)

Question 8

Which G protein is each vasopressin receptor?

Answer 8

V1 - q (vasoconstriction so smooth muscle contraction)

V2 - s (reabsorption of water involves inc cAMP in tubules)