Monoclonal antibodies reveal structural homogeneity of gamma-aminobutyric acid/benzodiazepine receptors in different brain areas.

Publisher Website
Google Scholar
Abstract
Monoclonal antibodies (mAb) against a GABA/benzodiazepine receptor complex (GABAA/BZR) were produced by using spleen cells from a mouse immunized with GABAABZR purified from bovine cerebral cortex. The mAb, most of which were of the IgG1 isotype could be divided into 4 groups (I-IV) specifying different antigenic structures. On immunoblots, group I mAb recognized exclusively the MW 55,000 .beta.-subunit, while groups II and IV mAb recognized the MW 50,000 .alpha.-subunit of bovine GABAA-BZR. Three of the 4 groups of mAb (I, III, and IV) crossreacted with both human and rat GABAA/BZR with the same subunit specificity as in bovine brains; the 4 group (II) crossreacted with human but not with the rat receptor. The binding sites for benzodiazepines as well as the high and low affinity GABA sites precipitation. Ligand binding to these sites was not inhibited by mAb. Since quantitative immunoprecipitation of GABAA-BZR was achieved with mAb selective for either the .alpha.- or .beta.-subunit, both subunits occur in each individual receptor complex. The pattern of immunoblot staining suggests that the smaller .alpha.-subunit is not a processing product of the larger .beta.-subunit. Both .alpha.- and .beta.-subunits were present in all brain areas and species tested (rat cerebral cortex, cerebellum and hippocampus; bovine cerebral cortex and cerebellum; human cerebral cortex). This suggests a uniform subunit composition of the receptor throughout the brain.