Human &mgr; Opioid Receptor Expressed in Sf9 Insect Cells was Functionally Coupled to Endogenous G Protein.

Human &mgr; opioid receptor(H&mgr;OR) with a tag of six consecutive histidines at its carboxyl terminus overexpressed in recombinant baculovirus infected Sf9 insect cells was demonstrated to be functionally coupled to endogenous G proteins. Na(+) and GTP could reduce the affinity binding of etorphine and Ohmefentanyl(Ohm) to H&mgr;OR overexpressed in Sf9. The binding of (35)S GTPgammaS to Sf9 cell membranes containing H&mgr;OR was stimulated by DAGO and Ohm. This stimulation could be blocked by naloxone or the pretreatment of PTX. Also, DAGO and Ohm could inhibit the increasing of intracellular cAMP stimulated by forskolin. The results showed H&mgr;OR expressed in Sf9 insect cells were functionally coupled to endogenous PTX sensitive G(i/o) proteins.