Related Experiment Videos
Electrogenic Na+/HCO3- cotransporters: cloning and physiology
1Department of Physiology and Biophysics and Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4790, USA. mfr2@po.cwru.edu
Annual Review of Physiology
|April 1, 1999
Summary
The cloning of the Na+ bicarbonate cotransporter (NBC) reveals a new family of HCO3- transporters. This discovery impacts our understanding of pH buffering and transport in various organs.
Area of Science:
- Physiology
- Molecular Biology
- Biochemistry
Background:
- Bicarbonate (HCO3-) and CO2 are primary biological pH buffers.
- Renal proximal tubule reabsorbs most filtered HCO3- via a basolateral Na+/HCO3- cotransporter (NBC).
Purpose of the Study:
- To review recent developments concerning the cloning and characterization of the Na+ bicarbonate cotransporter (NBC).
- To explore the physiological properties, isoforms, gene expression, and tissue distribution of NBC.
Main Methods:
- Expression cloning of the NBC.
- Analysis of protein features and physiological characteristics.
- Investigation of mRNA and protein distribution across various tissues.
Main Results:
- The Na+ bicarbonate cotransporter (NBC) has been cloned, revealing a 30-35% amino acid sequence identity with anion exchangers (AE1-3).
- NBC functions electrogenically, is dependent on Na+ and HCO3-, independent of Cl-, and inhibited by stilbenes (DIDS, SITS).
- NBC has been identified in multiple tissues beyond the kidney, including pancreas, prostate, brain, heart, and gastrointestinal tract, suggesting diverse physiological roles.
Conclusions:
- The cloning of NBC supports the emergence of a superfamily of HCO3- transporters.
- At least two genes encode NBC proteins, highlighting complexity in HCO3- transport regulation.
- Further research into NBC's distinct physiological roles in various tissues is warranted.