Electroneutral Na + /Cl - cotransport activity of zebrafish Slc12a10.1 expressed in Xenopus oocytes.

Na + /Cl - cotransporter 2 (Ncc2 or Slc12a10) is a membrane transport protein that belongs to the electroneutral cation-chloride cotransporter family. The Slc12a10 gene ( slc12a10 ) is widely present in bony vertebrates but is deleted or pseudogenized in birds, some bony fishes, and most mammals. Slc12a10 is highly homologous to Ncc (Slc12a3 or Ncc1); however, there are only a few reports measuring the activity of Slc12a10. In this study, we focused on zebrafish Slc12a10.1 (zSlc12a10.1) and analyzed its activity using Xenopus oocyte electrophysiology. Analysis using Na + -selective microelectrodes showed that intracellular sodium activity ( a Na i ) in zSlc12a10.1 oocytes was significantly decreased in Na + - or Cl - -free medium and recovered when Na + or Cl - was readded to the medium. Similar analysis using a Cl - -selective microelectrode showed that intracellular chloride activity ( a Cl i ) in zSlc12a10.1 oocytes significantly decreased in Na + - or Cl - -free medium and recovered when Na + or Cl - was readded to the medium. When a similar experiment was performed with a voltage clamp, the membrane current did not change when a Na i of zSlc12a10.1 oocytes was decreased in Na + -free medium. Molecular phylogenetic and synteny analyses suggest that gene duplication between slc12a10.2 and slc12a10.3 in zebrafish is a relatively recent event, whereas gene duplication between slc12a10.1 and the ancestral gene of slc12a10.2 / slc12a10.3 occurred at least about 2 million years ago. slc12a10 deficiency was observed in species belonging to Ictaluridae, Salmoniformes, Osmeriformes, Batrachoididae, Syngnathiformes, Gobiesociformes, Labriformes, and Tetraodontiformes. These results indicate that zebrafish Slc12a10.1 is an electroneutral Na + /Cl - cotransporter and establish its evolutionary position among various teleost slc12a10 paralogs. NEW & NOTEWORTHY Na + /Cl - cotransporter 2 (Slc12a10; Ncc2) is a protein highly homologous to Ncc (Slc12a3; Ncc1); however, there are only a few reports measuring the activity of Slc12a10. Electrophysiological analysis of Xenopus oocytes expressing zebrafish Slc12a10.1 showed that Slc12a10.1 acts as an electroneutral Na + /Cl - cotransporter. This is the third report on the activity of Slc12a10, following previous reports on Slc12a10 in eels.