WILD-TYPE AND INSECTICIDE-RESISTANT HOMOOLIGOMERIC GABA RECEPTORS OF DROSOPHILA-MELANOGASTER STABLY EXPRESSED IN A DROSOPHILA CELL-LINE

RDL is an ionotropic GABA receptor subunit, a product of the Rdl gene, originally identified in the Maryland strain of Drosophila melanogast er. Here, we report the generation of a Drosophila melanogaster cell l ine (S2-RDL(A302S)) stably expressing a mutated, dieldrin-resistant (A 302S) form of RDL. The properties of this dieldrin-resistant, homo-oli gomeric receptor have been compared with those of the stably expressed , wildtype form (S2-RDL). Using these stable lines, a striking reducti on in sensitivity to both picrotoxinin and dieldrin was observed for r esponses to GABA of S2-RDL(A302S) compared to S2-RDL. To determine if these stable insect cell lines generate results similar to those obtai ned by transient expression in Xenopus laevis oocytes, we have examine d the actions of two widely used convulsants, EBOB and TBPS, and a rec ently developed convulsant BIDN, on RDL-mediated GABA responses in the two expression systems. In both oocytes and S2 cells, the three convu lsants suppressed the amplitude of responses to GABA. Thus, in accord with earlier work on agonist and allosteric sites, the S2-RDL cell lin e is found to yield similar pharmacological results to those obtained in transient expression studies. Stable cell lines are now available e xpressing susceptible and resistant forms of an ionotropic receptor ta rgetted by GABAergic insecticides. Copyright (C) 1996 Elsevier Science Ltd.