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General Comment |
Grichtchenko et al 2000 reported the cloning, characterization and chromosomal mapping of a human electroneutral Na+- driven Cl-HCO3 exchanger.
The electroneutral Na+-driven Cl-HCO3 exchanger is a key mechanism for regulating intracellular pH (pHi) in neurons, glia and other cells. The authors report the cloning, tissue distribution, chromosomal location and functional characterization of the cDNA of such a transporter (NDCBE1) from human brain (AF069512). NDCBE1, which encodes 1044 amino acids, is 34% identical to the mammalian anion exchanger (AE2); ~50% to the electrogenic Na/HCO3 cotransporter (NBCe1) from salamander, rat and humans; ~73% to mammalian electroneutral Na/HCO3 cotransporters (NBCn1); 71% to mouse NCBE, and 47% to a Na+-driven anion exchanger (NDAE1) from Drosophila. Northern blot analysis of NDCBE1 shows a robust ~12-kb signal in all major regions of human brain and in testis, and weaker signals in kidney and ovary. This human gene (SLC4A8) maps to chromosome 12q13. When expressed in Xenopus oocytes and running in the forward direction, NDCBE1 is electroneutral and mediates increases in both pHi and [Na+]i (monitored with microelectrodes) that require HCO-3, and are blocked by DIDS. The pHi increase also requires extracellular Na+. The Na+:HCO-3 stoichiometry is 1:2.
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