Different roles for Gi and Go proteins in modulation of adenylyl cyclase type-2 activity.
The effect of Gi/o protein-coupled receptors on adenylyl cyclase type 2 (AC2) has been studied in Sf9 insect cells. Stimulation of cells expressing AC2 with the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) led to a twofold stimulation of cAMP synthesis that could be blocked with the protein kinase C inhibitor GF109203X. Activation of a coexpressed alpha2A-adrenoceptor or muscarinic M4 receptor inhibited the stimulation by TPA almost completely in a pertussis toxin-sensitive manner. Activation of Gs proteins switched the response of the alpha2A-adrenoceptor to potentiation of prestimulated AC2 activity. The potentiation, but not the inhibition, could be blocked by a Gbetagamma scavenger. A novel methodological approach, whereby signalling through endogenous G proteins was ablated, was used to assess specific G protein species in the signal pathway. Expression of Go proteins (alphao1 + beta1gamma2) restored both the inhibition and the potentiation, whereas expression of Gi proteins (alphai1 + beta1gamma2) resulted in a potentiation of both the TPA- and the Gs-stimulated AC2 activity. The data presented supports the view of AC2 as a molecular switch and implicates this isoform as a target for Go protein-linked signalling.
Näsman
Johnny
J
Department of Neuroscience, Division of Physiology, Uppsala University, BMC, Uppsala, Sweden.
Kukkonen
Jyrki P
JP
Holmqvist
Tomas
T
Akerman
Karl E O
KE
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000493:pharmacokinetics; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D019329:Idazoxan / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D037342:Pertussis Toxin / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D018411:Spodoptera; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
C547768:ADRA2A protein, human; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D018341:Receptors, Adrenergic, alpha-2; D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000242:Cyclic AMP; C058525:2-methoxyidazoxan; D037342:Pertussis Toxin; D011493:Protein Kinase C; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019205:GTP-Binding Protein alpha Subunits, Gs; D020962:Heterotrimeric GTP-Binding Proteins; D000262:Adenylyl Cyclases; C100622:adenylyl cyclase 2; D013755:Tetradecanoylphorbol Acetate; D019329:Idazoxan