Page 288 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

A. cAMP as second messenger
Extracellular space Deactivation:
First messenger
M s level
Stimulatory M s M i Inhibitory decreases
messenger Messenger (M) messenger
binds to
e.g., epinephrine receptor (R) e.g., epinephrine B i level
(β adrenoceptors) (α 2 adrenoceptor) decreases
R s R i
cAMP
Cell β β γ cAMP
membrane GDP γ GDP
α s α i β γ γ
G s protein G i protein β GDP Cellular Signal Transmission I
1 GDP
Adenylate cyclase α s α i
Intracellular space G s G i
M-R complex M i
M s
binds to
G protein R i
R s
β γ β β γ Plate 11.5
γ β γ
GDP GDP
α s α i
2 Return
Adenylate cyclase to inactive
state
α-GTP
M s M i
influences
adenylate cyclase
R s R i
Mg 2+
5
Mg 2+ GTP GTP GTP
α s α i α
GTPase
3 GDP Stimulates Inhibits GDP splits to
form GDP
Adenylate cyclase
Phospho-
ATP Second cAMP diesterase 5’-AMP
messenger
Activates Degradation of
Protein kinase A cAMP
Phosphatases
6
Proteins Proteins Protein
PO 4
Phosphorylation
4 ATP
ADP Cell response 275

Despopoulos, Color Atlas of Physiology © 2003 Thieme
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