G Protein Linked 2nd Messengers

Question 1

What are the three G proteins, and what are their basic function?

Answer 1

Gs: Increase cAMP
Gi: Decrease cAMP
Gq: Activation of Phospholipase C

Question 2

If Gq is activated, what are the cascade of events that follows?

Answer 2

Increased Phospholipase C

This releases IP3 and DAG from PIP2 (phospholipid phosphotidylinositol bisphosphate)

IP3 releases Ca from Sarco reticulum

Ca with DAG activates PKC

Question 3

Which ANS receptors have Gs proteins?

Answer 3

B1 & B2...... (catecholamines)
D1.......... (in renalvasculature-->vasodilation)
H2 .........(Histamine) 
Glucagon
Prostacyclins
Some Serotonins

Remember these all activate adenylyl cyclase

Question 4

Which ANS receptors have Gi proteins?

Answer 4

M2……….(Ach)
a2………..(adrenoreceptors)
D2………..(important in CNS)
Some serotonin and opioids

Think the inhibitor is MAD X2

They all inhibit AC

Question 5

Which ANS receptors have Gq proteins?

Answer 5

M1 & M3……….(Ach)
a1………………….(Norepi)
Angio II
Some serotonin

MaM 113

Question 6

Where is M1, M3 and a1 effective

Answer 6

M1–>CNS
M3–>peripheral autonomics
a1–>on blood vessels, activated by norepi and ep and controls BP

Question 7

What are the 4 sympathetic receptor types?

Answer 7

a1
a2
B1
B2

Question 8

What is the major function of a1 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 8

Ligand: Norepi & Epi

Function:
Increase
-vascular s. muscle contraction
-pupillary dilator muscle contraction (mydriasis)
-intestinal and bladder sphincter muscle contraction

Protein Class: Gq
Receptor Type: Sympathetic

Question 9

What is the major function of a2 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 9

Ligand: Norepi & Epi (higher affinity for norepi)

Function:
Decrease
   -Sympathetic outflow
   -Insulin release
   -Lipolysis

Increase
-platelet aggregation

Protein class: Gi

Receptor Type: Sympathetic

Question 10

What is the major function of B1 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 10

Ligand: Catecholamines

Function:
Increase
  -HR
  -Contractility
  -Renin Release
  -Lipolysis

Protein Class Gs

Receptor Type: Sympathetic

Question 11

What is the major function of B2 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 11

Ligand: Catecholamines

Function:

• Vasodilation
• Bronchodilation (s. muscle relax’n in bronchi)
• Increase:
  
  • HR
  • Contractility
  • lipolysis
  • insulin release
  • uterine tone (tocolysis)
  • ciliary muscle relaxation
  • aqueous humor production

Protein Class: Gs

Receptor Type: Sympathetic

Question 12

What is the major function of M1 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 12

Ligand: Ach

Function: CNS, Enteric Nervous System

Protein Class: Gq

Receptor Type: Parasympathetic

Question 13

What is the major function of M2 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 13

Ligand: Ach

Function:
-Decrease HR and contractility of atria

Protein Class: Gi

Receptor Type: Parasympathetic

Question 14

What is the major function of M3 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 14

Ligand: Ach

Function:

 - Increase: 
     - Exocrine Gland Secretions (lacrimal, salivary, gastric)
     - Bladder Contraction
     - Bronchoconstriction
     - Pupillary sphincter muscle contraction (miosis)
     - Ciliary muscle contraction (accommodation)

Protein Class: Gi

Receptor Type: Parasympathetic

Question 15

What is the major function of D1 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 15

Ligand: Dopamine

Function:
-Relaxes renal vascular s. muscle

Protein Class: Gs

Receptor Type: Dopamine

Question 16

What is the major function of D2 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 16

Ligand: Dopamine

Function: Modulates transmitter release, especially in brain

Protein Class: Gi

Receptor Type: Dopamine

Question 17

What is the major function of H1 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 17

Ligand: Histamine

Function:

• Increase
  
  • Nasal and bronchial mucus production
  • Vascular permeability (duh)
  • Contraction of bronchioles
  • Pruritis
  • Pain

Protein Class: Gq

Receptor Type: Histamine

Question 18

What is the major function of H2 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 18

Ligand: Histamine

Function: Increase gastric acid secretion

Protein class: Gs

Receptor Type: Histamine

Question 19

What is the major function of V1 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 19

Ligand: Vasopressin

Function: Increase vascular smooth muscle contraction

Protein Class: Gq

Receptor Type: Vasopressin

Question 20

What is the major function of V2 receptor and what is it’s ligand? What is it’s protein class, and what receptor type is it?

Answer 20

Ligand: Vasopressin

Function:
-Increase H2O permeability and reabsorption in the collecting tubules of the kidney (V2 is found in the 2 kidneys)

Protein Class: Gs

Receptor Type: Vasopressin

Question 21

What is the mnemonic for the receptor types?

Answer 21

Qiss (sympathetic a1-B2) and
qiq (para M1-M3) til ur
siq (dopa D1/2 and H1) of
sqs (H2, V1 and V2)

Question 22

What is the mnemonic for the Gq receptor?

Answer 22

HaV 1 M&M (or 3)

H1, a1, V1, M1, and M3