A COMBINATION OF HUMAN ALPHA-1 AND BETA-1 SUBUNITS IS REQUIRED FOR FORMATION OF DETECTABLE GABA-ACTIVATED CHLORIDE CHANNELS IN SF9 CELLS

The baculovirus expression system was used to produce alpha1 and beta1 subunits of the human GABA(A) receptor in Sf9 cells. In cells infected with both alpha1 and beta1 recombinent viruses, GABA elicited an outwardly rectifying chloride current that was blocked by bicuculline and potentiated by pentobarbitone. GABA did not produce detectable currents in cells infected with either alpha1 or beta1 recombinant viruses alone. In these cells, and in control (non-infected) Sf9 cells, pentobarbitone depressed the leakage current (K(i) = 55 muM). Fluorescently labelled monoclonal antibodies to the alpha1 subunit showed greater amounts of the alpha1 subunit in cells infected with only the al recombinant virus than in cells co-infected with the alpha1 and beta1 recombinant viruses. Fluorescence of the plasma membrane was seen in cells co-infected with the alpha1 and beta1 recombinant viruses, but was absent in cells infected with only the alpha1 recombinant virus. It was concluded that the alpha1 subunit normally interacts with the beta1 subunit to be transported to the plasma membrane in Sf9 cells.