Lecture 6: Receptors and Cell Signaling

Question 1

In lipophilic signaling, what is the difference between cytoplasmic and nuclear receptors?

Answer 1

Cytoplasm: Ligand binds to HSP, activating it. Hormone-receptor complex translocates to nucleus and binds to HRE (hormone response element) in promoter region

Nuclear: Binds to DNA directly and activates complex

Question 2

How does Gs signaling work? What are some examples?

Answer 2

GTP activates cAMP and pKa
Turns of through PDE

B adrenergic (epi) and Histamine

Question 3

How does Gi signaling work? What are some examples?

Answer 3

Inhibits cAMP and pKa is not activated

Dopamine: increases HR
Norepi: constricts smooth muscles

Question 4

How does Gt signaling work? What are some examples?

Answer 4

GTP activates cGMP
Turns of through PDE

Light: Rhodopsin

Question 5

How does Gq signaling work? What are some examples?

Answer 5

GTP activates phospholipase C
activates DAG/IP3 –> increase in intracellular Ca2+

Muscarinic (Acetylcholine) - bronchoconstriction and stimulation of salivary glands

Question 6

How do cyclic nucleotides work? What are some examples?

Answer 6

Gt signaling

• Hydrolyze cGMP and lasts longer
• PDE is inhibited
• smooth muscle relaxation and vasodilation

Example: viagra and caffeine (increased HR)

Question 7

How does cholera toxin work?

Answer 7

Gs cannot be shut off

• overproduction of cAMP
• CTFR ions are open –> chloride leaves
• water and salt lost too
• diarrhea

Question 8

How does whooping cough work?

Answer 8

Gi is inhibited

-overproduction of cAMP

Question 9

How does nitric oxide work?

Answer 9

NO activates cGMP
-smooth muscle relaxation and vasodilation

Cannot take drugs that inhibit cGMP PDE

Question 10

What docking proteins recognize RTK phosphorylation and promotes downstream pathways?

Answer 10

SH2 domain of Grb2