Two human α2-adrenoceptor subtypes α2A-C10 and α2B-C2 expressed in Sf9 cells couple to transduction pathway resulting in opposite effects on cAMP production

The baculovirus expression vector system utilizing the strong polyhedrin gene promoter of the Autographa californica nuclear polyhedrosis virus (AcNPV) was used for high level expression of the two α₂-adrenoceptor subtypes α₂A-C10 and α₂B-C2 in Spodoptera frugiperda (Sf-9) insect cells. For rapid screening of recombinant viruses the luciferase gene was expressed under the early ETL-promoter (early transcript large) in the same plasmid. Both receptor subtypes showed the same rank order of binding affinity for four agonists tested: dexmedetomidine > l-medetomidine = clonidine > noradrenaline. For the α₂A-C10 subtype, these agonists inhibited forskolin stimulated cAMP production through pertussis toxin sensitive G-proteins. In contrast, for the α₂B-C2 subtype the agonists stimulated both basal and forskolin stimulated cAMP production.