Meeting Abstract
Cation-chloride cotransporters (CCCs) regulate cell volume and intracellular chloride and contribute to transepithelial salt secretion and absorption. CCCs include the K-Cl, Na-Cl, and Na-K-Cl cotransporters, which move monovalent cations and chloride in electroneutral fashion. The Aedes aegypti transporter aeCCC2 belongs to an insect specific clade of transporters that group with the sodium-dependent CCCs. Transcripts of aeCCC2 are highly expressed in epithelial tissues, especially the hindgut. Surprisingly, aeCCC2 induces sodium-dependent currents when expressed in Xenopus oocytes. We have further characterized the transport activity of aeCCC2 and its Drosophila melanogaster ortholog ncc83. In voltage clamp experiments, oocytes expressing aeCCC2 and ncc83 had greater sodium currents than water-injected controls. When membrane potential was allowed to fluctuate, it was strongly dependent on external sodium in oocytes expressing aeCCC2 and ncc83, but not in water-injected oocytes. Following a 10-minute hypotonic treatment, changes in membrane potential in response to sodium replacement were 20 ± 3 mV in ncc83 and 26 ± 4 mV in aeCCC2, approximately two-fold greater than before swelling. Changes in membrane potential or current due to sodium replacement occurred in the absence of external chloride and potassium. These results lead to the hypothesis that aeCCC2 and ncc83 are electrogenic sodium transporters that contribute to transepithelial salt transport in insects. Funding: American Physiological Society RCEA, NIH F33 GM131599, and Kenyon College.
