The human D4 dopamine receptor has been genetically engineered for expression in insect cells using the baculovirus system. A D4 cDNA gene fusion construct [(1991) Nature 350, 610-614] was synthetically modified to remove two introns from the coding region, and expressed in S. frugiperda (Sf9) cells as a fusion with a short sequence from the polyhedrin protein. Binding assays with [3H]spiperone indicated high levels of D4 receptor binding 90 h after infection and a pharmacological profile identical to that reported for D4 receptors expressed in COS-7 cells using the cDNA gene hybrid. We also show that the agonist binding affinity of D4 receptors expressed in Sf9 cells can be shifted by GTP-γ-S, indicating coupling to G-proteins.
