Second messengers

Question 1

Which second messengers do you know?

Answer 1

cAMP, cGMP, IP3, DAG and Ca^2+

Question 2

What are the advantages of second messenger signaling?

Answer 2

High sensitivity and the possibility for regulation by crosstalk

Question 3

Explain the signal pathway of Gs.

Answer 3

Gs coupled GPCR binds extracellular ligand, and are activated. The coupled Gs is activated, and the Galfa S activates an adenylyl cyclase, which converts ATP to cAMP, cAMP activates a PKA, which can then induce a cascade of signaling

Question 4

Explain the signal pathway of Gq.

Answer 4

Gq coupled GPCR binds extracellular ligand, and are activated. The coupled Gq is activated, and the Galfa q activates phospholipase C (PLC), which cleaves PIP2 to IP3 and DAG. IP3 gates a Ca^2+ channel on ER, and DAG + Ca^2+ activates PKC, which can then induce a cascade of signaling

Question 5

Which cell responses are mediated by cAMP?

Answer 5

Glycogen breakdown in skeletal muscles, increease of heart rate and force of contraction, fat breakdown, cortisol secretion in the adrenal glands

Question 6

Which cell responses are mediated by Ca^2+?

Answer 6

Muscle contraction, cell differentiation, gene regulation, enzyme and allosteric protein regulation, neurotransmitter release

Question 7

How can the second messenger signal be ended?

Answer 7

GPCR desensitization, removal of the active GPCR ligand, inactivation of the G-protein, removal of the second messenger

Question 8

Explain the internalization via clatrhin-coated vesicles.

Answer 8

GRK phosphorylate the GPCR, beta-arrestin binds to the phosphorylated GPCR, clathrin-coated vesicle are formed