Immunochemical identification of the alpha 1- and alpha 3-subunits of the GABAA-receptor in rat brain.

To identify subunit variants of the GABAA-receptor antisera were developed against specific cDNA-derived peptide sequences of the alpha 1- and alpha 3-subunits of rat brain. The alpha 1-subunit antiserum selectively recognized a protein of 50 +/- 1 kDa in rat and bovine GABAA-receptor preparations, while the alpha 3-subunit antiserum interacted with a protein doublet of 59 +/- 2 kDa and 61 +/- 3 kDa. The alpha 1-subunit immunoreactivity resides in a large population of GABAA-receptors as shown by immunoprecipitation of 63 +/- 6% of [3H]flumazenil binding sites with the alpha 1-subunit antiserum. In contrast, only 24 +/- 3% of receptor binding sites were precipitated with the alpha 3-subunit antiserum. Co-precipitation studies suggest that the alpha 1- and alpha 3-subunit immunoreactivities do not share the same receptor population while the gamma 2-subunit immunoreactivity is associated with the alpha 1-subunit immunoreactivity.