Lecture: 23

Question 1

G-protein couple receptor (GPCR) function?

Answer 1

Passes on a signal (message) from outside the cell by producing a second messenger inside the cell

Question 2

CAMP Pathway

Answer 2

-glucagon and catecholamines (Epinephrine, norepinephrine)

Pathway:
1) (Heptahelical receptors) GPCR passes on a signal from outside the cell by producing a second messenger inside the cell

2) Epinephrine/norepinephrine or glucagon binds to GPCR = binding it to G-S-Beta-2
3) GDP bond to Gs falls off and GTP comes out activating it
4) Gs moves to adenylyl cyclase = activation
5) Adenylyl cyclase forms cAMP

6) cAMP can activate Protein kinase A + PKA phosphorylates of cellular proteins = cellular response
(CREB, CREB-P = Change in gene expression) ALSO turns ATP to SER/THR)

7) Or cAMP can be degraded by cyclic phosphodiesterase (Hydrolyzes cAMP to 5’ -AMP)

Question 3

Cholera

Answer 3

(Toxin)

What it does:
-ADP-Ribosylates G-ALPHA-S resulting in continuous = CONTINUOUSLY ACTIVE G- ALPHA-S (BC GTP constantly activated)

CAMP effects:
-INCREASES in intestines

Question 4

Pertussis

Answer 4

(Toxin)

What it does:
-ADP-Ribosylates G-ALPHA-I resulting in continuous = CONTINUOUSLY INACTIVE G- ALPHA-I

CAMP effects:
-INCREASED in respiratory-tract cells

Effects:

• Respiratory distress
• Whooping cough

Question 5

E. Coli

Answer 5

-Can produce a toxin that ADP-Ribosylates G-ALPHA-I = INCREASED CAMP

Question 6

IP3, DAG, Ca2+ Pathway

Answer 6

Pathway: (Phosphoinositide System:)

1) (Heptahelical receptors) GPCR passes on a signal from outside the cell by producing a second messenger inside the cell
2) Epinephrine/Norepinephrine binds to GPCR = binding it to G-Q-Alpha-1
3) G-Q-Alpha activates phospholipase C (PLC)
4) PLC cleaves PIP2 to IP3 and DAG
5) IP3 and CA2+ activate the Protein Kinase C = cellular response

(Protein Kinase C requires DAG, Ca2+ and Phospholipid for maximal activity)

Question 7

G-Q-Alpha-1

Answer 7

Increases IP3/DAG, Ca2+, Protein kinase c (PKC)

Question 8

G-I-Alpha-2

Answer 8

Decreases cAMP, IP3/DAG (everything)

Question 9

G-S-Beta-1

Answer 9

Increases cAMP, Ca+

Question 10

G-S-Beta-2

Answer 10

Increases cAMP, Protein kinase A (PKA)

relaxation smooth muscle