Localization of endogenous and recombinant Na+-driven anion exchanger protein NDAE1 from Drosophila melanogaster

Na⁺-dependent Cl/HCOexchange activity helps maintain intracellular pH (pH_i)homeostasis in many invertebrate and vertebrate cell types. Ourlaboratory cloned and characterized a Na⁺-dependentCl/HCO exchanger (NDAE1) fromDrosophila melanogaster (Romero MF, Henry D, Nelson S, HartePJ, and Sciortino CM. J Biol Chem 275:24552-24559, 2000). In the present study we usedimmunohistochemical and Western blot techniques to characterize thedevelopmental expression, subcellular localization, and tissue distribution of NDAE1 protein in D. melanogaster. We haveshown that a polyclonal antibody raised against the NH₂terminus of NDAE1 (CWR57) recognizes NDAE1 electrophysiologicallycharacterized in Xenopus oocytes. Moreover, our resultsbegin to delineate the NDAE1 topology, i.e., both the NH₂and COOH termini are intracellular. NDAE1 is expressed throughoutDrosophila development in the central and peripheral nervoussystems, sensilla, and the alimentary tract (Malpighian tubules, gut,and salivary glands). Coimmunolabeling of larval tissues with NDAE1antibody and a monoclonal antibody to theNa⁺-K⁺-ATPase -subunit revealed that themajority of NDAE1 is located at the basolateral membranes of Malpighiantubule cells. These results suggest that NDAE1 may be a keypH_i regulatory protein and may contribute to basolateralion transport in epithelia and nervous system of Drosophila.