Characterization of the mRNA and the Gene of a Putative Neuronal Nicotinic Acetylcholine Receptor Protein from Drosophila

Abstract

In insects, acetylcholine is a major excitatory transmitter of the central nervous system, while neuromuscular transmission is mediated by amino acids (1). A variety of studies have identified an α-bungarotoxin-binding component in the brain of Drosophila, which displays a pharmacology similar to that of the nicotinic acetycholine receptor (AChR) from the vertebrate nervous system (2–5). The concentration of α-toxin-binding sites in Drosophila heads is remarkably higher than in any nervous tissue of vertebrates (6). Recently the α-bungarotoxin-binding protein of the locust central nervous system has been shown to be a functional AChR protein containing four identical (or very similar) polypeptides of Mr = 65,000 which are immunologically related to the nicotinic AChR of Torpedo electroplax (7, 8). Using DNA probes of the Torpedo receptor γ-subunit we have isolated cDNA clones encoding a putative neuronal AChR protein of Drosophila (ARD protein). The appearance of its mRNA during development coincides with the major periods of differentiation of the Drosophila central nervous system (9). Here, the general features of the ARD cDNA/mRNA and the deduced protein are summarized and compared to the structure of the vertebrate AChR subunits. A preliminary characterization of organization of the ARD gene is presented.