Efficient adenylyl cyclase activation by a beta2-adrenoceptor-G(i)alpha2 fusion protein

• Published in: Biochemical and biophysical research communications 2002-11, Vol.298 (5), p.824-828
• Main Authors: Seifert, Roland, Wenzel-Seifert, Katharina, Arthur, John M, Jose, Powell O, Kobilka, Brian K
• Format: Article
• Language: English
• Subjects: Adenylyl Cyclases - metabolism; Animals; Cell Line; Colforsin - pharmacology; Enzyme Activation - drug effects; GTP-Binding Protein alpha Subunit, Gi2; GTP-Binding Protein alpha Subunits, Gi-Go - genetics; GTP-Binding Protein alpha Subunits, Gi-Go - metabolism; Guanosine 5'-O-(3-Thiotriphosphate) - pharmacology; Isoproterenol - pharmacology; Models, Biological; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - metabolism; Receptors, Adrenergic, beta-2 - genetics; Receptors, Adrenergic, beta-2 - metabolism; Receptors, Formyl Peptide; Receptors, Immunologic - genetics; Receptors, Immunologic - metabolism; Receptors, Peptide - genetics; Receptors, Peptide - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Spodoptera
• ISSN: 0006-291X

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.