Na+:HCO(3-) cotransporters (NBC): cloning and characterization
1Department of Medicine, University of Cincinnati, Cincinnati, OH 45267-0585, USA. Manoocher.Soleimani@uc.edu
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 HCO(3-) 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.
More Related Videos
07:38Functional Characterization of Na+/H+ Exchangers of Intracellular Compartments Using Proton-killing Selection to Express Them at the Plasma Membrane
Published on: March 30, 2015
10:08Study of the Functions and Activities of Neuronal K-Cl Co-Transporter KCC2 Using Western Blotting
Published on: December 9, 2022
Related Concept Videos
Secondary Active Transport
Membrane Transporters
Transporters are mainly composed of alpha-helices, built from bundles of ten or more helices traversing the plasma membrane. The solute-binding sites are located midway, where some of the helices are broken or distorted, making space for the binding site through...
ABC Transporters: Exporter
Secondary Active Transport
Secondary Active Transport
Active Transport
Primary active transporters, like Na+, K+ and -ATPase, directly utilize ATP to move ions across the membrane. These transporters play significant roles in various physiological processes. For instance, Na+, K+ and -ATPase maintain...
