IMMUNOCHEMICAL IDENTIFICATION OF THE ALPHA-1-SUBUNIT AND ALPHA-3-SUBUNIT OF THE GABA-A-RECEPTOR IN RAT-BRAIN

To identify subunit variants of the GABA(A)-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 GABA(A)-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 GABA(A)-receptors as shown by immunoprecipitation of 63 +/- 6% of [H-3]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.