Functional analysis and tissue-specific expression of Drosophila Na+,K+-ATPase subunits.

We have previously purified and characterized a nervous system-specific glycoprotein antigen from adult Drosophila heads, designated Nervana [nerve antigen (NRV)] and identified two separate genes coding for three different proteins. All three proteins share homology with the beta subunits of Na+,K+-ATPase from various other species. In this study we have isolated a new Drosophila Na+,K+-ATPase alpha subunit cDNA clone (PSalpha; GenBank accession no. AF044974) and demonstrate expression of functional Na+,K+-ATPase activity when PSalpha mRNA is coinjected into Xenopus oocytes along with any of the three different Nrv mRNAs. Western blotting, RNase protection assays, and immunocytochemical staining of adult fly sections indicate that NRV2 is expressed primarily in the nervous system. Staining is most intense in the brain and thoracic ganglia and is most likely associated with neuronal elements. NRV1 is more broadly expressed in muscle and excretory tissue and also shows diffuse distribution in the nervous system. Similar to other species, Drosophila expresses multiple isoforms of Na+,K+-ATPase subunits in a tissue- and cell type-specific pattern. It will now be possible to use the advantages of Drosophila molecular and classical genetics to investigate the phenotypic consequences of altering Na+,K+-ATPase expression in various cell and tissue types.