IDENTIFICATION OF THE GABA-A RECEPTOR ALPHA-3 SUBUNIT IN THE IMR-32 NEUROBLASTOMA CELL-LINE

A previous report has described the presence of t-[S-35]-butylbicyclop hosphorothionate binding sites and GABA-gated Cl- flux in the human ne uroblastoma IMR-32 cell line. We now report the further characterisati on of this binding site and, even more important, the identification o f the GABA(A) receptor a3 subunit expressed in these cells. Cell membr anes prepared from IMR-32 cells were screened by immunoblotting for re activity with various GABA(A) receptor a subunit-specific antibodies. Of these, only anti-Cys alpha3 454-467 antibodies recognised specifica lly and in a dose-dependent manner an immunoreactive band. This M(r) 5 8,000 immunoreactive species and the N-deglycosylated derivatives were both coincident with the respective homologues found in both calf cer ebral cortex membranes and purified receptor preparations. This is the first report of the identification of a specific GABA(A) receptor sub unit expressed in a human cell line, and it therefore provides a conve nient model for the study of receptor structure and regulation.