Na+:HCO3 − Cotransporters (NBC): Cloning and Characterization

Na+:HCO3 − Cotransporters (NBC): Cloning and Characterization The sodium bicarbonate cotransporter (NBC1) is essential for bicarbonate transport across plasma membranes in epithelial and nonepithelial cells. The direction of the NaHCO3 movement in secretory epithelia is opposite to that in reabsorptive epithelia. In secretory epithelia (such as pancreatic duct cells) NBC is responsible for the transport of bicarbonate from blood to the cell for eventual secretion at the apical membrane. In reabsorptive epithelia (such as kidney proximal tubule cells) NBC is responsible for the reabsorption of bicarbonate from cell to the blood. In nonepithelial cells this transporter is mainly involved with cell pH regulation. Recent molecular cloning experiments have identified the existence of four NBC isoforms (NBC1, 2, 3 and 4) and two NBC-related proteins AE4 and NCBE (Anion Exchanger 4 and Na-dependent Chloride-Bicarbonate Exchanger). All but AE4 are presumed to mediate the cotransport of Na+ and HCO3 − under normal conditions and may be functionally altered in certain pathologic states. NBC1 shows a limited tissue expression pattern, is electrogenic and plays an important role in bicarbonate reabsorption in kidney proximal tubule. In addition to the kidney, NBC1 is expressed in pancreatic duct cells, is activated by cystic fibrosis transmembrane conductance regulator (CFTR) and plays an important role in HCO3 − secretion. NBC2 and NBC3 have a wider tissue distribution than NBC1, are electroneutral, and are involved with cell pH regulation. The characterization of NBC4 is incomplete. The NBC-related protein called NCBE mediates Na-dependent, Cl−/Bicarbonate Exchange. The purpose of this review is to summarize recent advances on the cloning of NBC isoforms and related proteins and their role and regulation in physiologic and pathologic states. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Na+:HCO3 − Cotransporters (NBC): Cloning and Characterization

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 2001 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-001-0055-8
Publisher site
See Article on Publisher Site

Abstract

The sodium bicarbonate cotransporter (NBC1) is essential for bicarbonate transport across plasma membranes in epithelial and nonepithelial cells. The direction of the NaHCO3 movement in secretory epithelia is opposite to that in reabsorptive epithelia. In secretory epithelia (such as pancreatic duct cells) NBC is responsible for the transport of bicarbonate from blood to the cell for eventual secretion at the apical membrane. In reabsorptive epithelia (such as kidney proximal tubule cells) NBC is responsible for the reabsorption of bicarbonate from cell to the blood. In nonepithelial cells this transporter is mainly involved with cell pH regulation. Recent molecular cloning experiments have identified the existence of four NBC isoforms (NBC1, 2, 3 and 4) and two NBC-related proteins AE4 and NCBE (Anion Exchanger 4 and Na-dependent Chloride-Bicarbonate Exchanger). All but AE4 are presumed to mediate the cotransport of Na+ and HCO3 − under normal conditions and may be functionally altered in certain pathologic states. NBC1 shows a limited tissue expression pattern, is electrogenic and plays an important role in bicarbonate reabsorption in kidney proximal tubule. In addition to the kidney, NBC1 is expressed in pancreatic duct cells, is activated by cystic fibrosis transmembrane conductance regulator (CFTR) and plays an important role in HCO3 − secretion. NBC2 and NBC3 have a wider tissue distribution than NBC1, are electroneutral, and are involved with cell pH regulation. The characterization of NBC4 is incomplete. The NBC-related protein called NCBE mediates Na-dependent, Cl−/Bicarbonate Exchange. The purpose of this review is to summarize recent advances on the cloning of NBC isoforms and related proteins and their role and regulation in physiologic and pathologic states.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Sep 15, 2001

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