STABLE EXPRESSION OF MAMMALIAN TYPE-A GAMMA-AMINOBUTYRIC-ACID RECEPTORS IN MOUSE CELLS - DEMONSTRATION OF FUNCTIONAL ASSEMBLY OF BENZODIAZEPINE-RESPONSIVE SITES

The differential sensitivity of type A gamma-aminobutyric acid (GABA(A)) receptors to benzodiazepine ligands seen in the mammalian nervous system is thought to be generated by the existence of a number of different receptor subtypes, assembled from a range of closely related subunits (alpha-1-6, beta-1-3, gamma-1-3, and delta) encoded by discrete genes. The characteristics of a given subtype can be determined by the coexpression of cloned cDNAs encoding the subunits of interest. Two transient expression systems have so far been employed in the study of the ligand-binding characteristics and chloride channel properties of such GABA(A) receptors-Xenopus oocytes and transfected mammalian cells. Here we report on the use of a steroid-inducible promoter expression system for the production of a permanently transfected clonal cell line expressing the alpha-1-beta-1-gamma-2L GABA(A) receptor subtype. Using both immunoprecipitation by subunit-specific antisera and gel-exclusion chromatography, we have shown that the alpha-1, beta-1, and gamma-2L subunits coassemble to form receptor macromolecules that are of the same size as native GABA(A) receptors. Additionally, the recombinant receptors have the same benzodiazepine pharmacology as native alpha-1-containing GABA(A) receptors and function as GABA-gated chloride channels. Such cell lines expressing individual GABA(A) receptor subtypes will prove important tools in the study of the structure, function, and pharmacology of GABA(A) receptors and in the development of subtype-specific drugs.