A mutation of the drosophila sodium pump α subunit gene results in bang-sensitive paralysis

A bang-sensitive enhancer trap line was isolated in a behavioral screen. The flies show a weak bang-sensitive paralysis, recovering after about 7 s. The P element insert is localized at 93131-2 on the salivary chromosomes, the site of the (Na⁺,K⁺)ATPase a subunit gene. Molecular characterization demonstrates that the transposon is inserted into the first intron of this gene. This insertion leads to normal-sized transcripts, but reduced levels of expression. This change is also reflected in lower amounts of a normal-sized a subunit protein. Mutant flies show a much greater sensitivity to ouabain, likewise indicating, on a functional level, a reduction in Na⁺ pump activity. Furthermore, the bang-sensitive behavior can also be mimicked by injecting sublethal doses of ouabain into wild-type flies. The molecular and functional evidence indicates that the insertion has produced a hypomorphic mutation of the (Na⁺,K⁺)ATPase α subunit gene, opening the way to future studies of the regulation of the Na⁺ pump.