The α-Bungarotoxin-binding Nicotinic Acetylcholine Receptor from Rat Brain Contains Only the α7 Subunit

Abstract

When expressed in Xenopus oocytes, the rat alpha7 subunit forms homo-oligomeric nicotinic acetylcholine receptors, which are blocked by alpha-bungarotoxin. Since the pharmacological and physiological properties of the alpha7 receptor expressed in oocytes are similar to those of the alpha-bungarotoxin-sensitive nicotinic currents recorded from neuronal preparations and the distribution patterns of alpha7 mRNA and alpha-bungarotoxin-binding sites in the rat brain are very similar, alpha7 is thought to be the main component of the alpha-bungarotoxin-binding nicotinic receptor in the mammalian brain. However, while alpha7 is found in purified alpha-bungarotoxin-binding complexes from rat brain or PC12 cells, other proteins copurify with it. Therefore, the question whether alpha7 forms a homo-oligomeric alpha-bungarotoxin-binding nicotinic receptor in the mammalian brain remains. We have developed and characterized affinity-purified polyclonal antibodies and used these antibodies in Western blot analyses of alpha-bungarotoxin-binding proteins purified from rat brains. We report here that our experimental data support the current working hypothesis that the alpha-bungarotoxin-binding nicotinic receptor is a homo-oligomer of alpha7 subunits in the rat brain.