An electrogenic Na(+)-HCO(-)(3) cotransporter (NBC) with a novel COOH-terminus, cloned from rat brain

Am J Physiol Cell Physiol. 2000 Jun;278(6):C1200-11. doi: 10.1152/ajpcell.2000.278.6.C1200.


We screened rat brain cDNA libraries and used 5' rapid amplification of cDNA ends to clone two electrogenic Na(+)-HCO(-)(3) cotransporter (NBC) isoforms from rat brain (rb1NBC and rb2NBC). At the amino acid level, one clone (rb1NBC) is 96% identical to human pancreas NBC. The other clone (rb2NBC) is identical to rb1NBC except for 61 unique COOH-terminal amino acids, the result of a 97-bp deletion near the 3' end of the open-reading frame. Using RT-PCR, we confirmed that mRNA from rat brain contains this 97-bp deletion. Furthermore, we generated rabbit polyclonal antibodies that distinguish between the unique COOH-termini of rb1NBC (alpharb1NBC) and rb2NBC (alpharb2NBC). alpharb1NBC labels an approximately 130-kDa protein predominantly from kidney, and alpharb2NBC labels an approximately 130-kDa protein predominantly from brain. alpharb2NBC labels a protein that is more highly expressed in cortical neurons than astrocytes cultured from rat brain; alpharb1NBC exhibits the opposite pattern. In expression studies, applying 1.5% CO(2)/10 mM HCO(-)(3) to Xenopus oocytes injected with rb2NBC cRNA causes 1) pH(i) to recover from the initial CO(2)-induced acidification and 2) the cell to hyperpolarize. Subsequently, removing external Na(+) reverses the pH(i) increase and elicits a rapid depolarization. In the presence of 450 microM DIDS, removing external Na(+) has no effect on pH(i) and elicits a small hyperpolarization. The rate of the pH(i) decrease elicited by removing Na(+) is insensitive to removing external Cl(-). Thus rb2NBC is a DIDS-sensitive, electrogenic NBC that is predominantly expressed in brain of at least rat.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibodies
  • Brain / metabolism*
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / physiology*
  • Cloning, Molecular
  • Female
  • Gene Library
  • Humans
  • Membrane Potentials
  • Molecular Sequence Data
  • Oocytes / physiology
  • Protein Isoforms / chemistry
  • Protein Isoforms / genetics
  • Protein Isoforms / physiology
  • RNA, Messenger / genetics
  • Rabbits
  • Rats
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Alignment
  • Sequence Deletion*
  • Sequence Homology, Amino Acid
  • Sodium-Bicarbonate Symporters
  • Xenopus laevis


  • Antibodies
  • Carrier Proteins
  • Protein Isoforms
  • RNA, Messenger
  • Recombinant Proteins
  • Sodium-Bicarbonate Symporters

Associated data

  • GENBANK/AF124441
  • GENBANK/AF254802