Efficient adenylyl cyclase activation by a beta2-adrenoceptor-G(i)alpha2 fusion protein.
The G-protein G(i)alpha can activate adenylyl cyclase (AC), but the relevance of this AC activation is unknown. We used receptor-G protein co-expression and receptor-G protein fusion proteins to investigate G(i)alpha(2) regulation of AC in Sf9 cells. G(i)alpha(2) was fused to the beta(2)-adrenoceptor (beta(2)AR), a preferentially G(s)-coupled receptor, or the formyl peptide receptor (FPR), a G(i)-coupled receptor. The FPR co-expressed with, or fused to, G(i)alpha(2), reduced AC activity. In contrast, the beta(2)AR fused to G(i)alpha(2) was a highly efficient AC activator, while the beta(2)AR co-expressed with G(i)alpha(2) was not. Agonist efficiently stimulated incorporation of [alpha-32P]GTP azidoanilide into beta(2)AR-G(i)alpha(2). We explain AC activation by beta(2)AR-G(i)alpha(2) by a model in which there is interaction of the beta(2)AR and AC, preventing tethered G(i)alpha(2) from interacting with the inhibitory G(i)alpha site of AC. The postulated beta(2)AR/AC interaction brings G(i)alpha(2) into close proximity of the G(s)alpha site of AC, enabling G(i)alpha(2) to activate AC.
Seifert
Roland
R
Howard Hughes Medical Institute, Beckman Center, B-157, Stanford University Medical Center, CA 94305-5428, USA. rseifert@ku.edu
Wenzel-Seifert
Katharina
K
Arthur
John M
JM
Jose
Powell O
PO
Kobilka
Brian K
BK
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000235:genetics / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008954:Models, Biological; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism*; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018411:Spodoptera
D011518:Proto-Oncogene Proteins; D018343:Receptors, Adrenergic, beta-2; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; D018000:Receptors, Peptide; D011993:Recombinant Fusion Proteins; D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D000262:Adenylyl Cyclases; D007545:Isoproterenol