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Biochem Biophys Res Commun. 2002 Nov 15;298(5):824-8.

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

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Howard Hughes Medical Institute, Beckman Center, B-157, Stanford University Medical Center, CA 94305-5428, USA.


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.

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