Na+-dependent HCO3- import by the slc4a10 gene product involves Cl- export
Helle Hasager Damkier1, Christian Aalkjaer2, Jeppe Praetorius1
1Water and Salt Research Center, Aarhus University, DK-8000 Aarhus, Denmark; Department of Anatomy, Aarhus University, DK-8000 Aarhus, Denmark.
The Journal of Biological Chemistry
|June 23, 2010
Summary
The slc4a10 gene functions as a sodium-dependent chloride/bicarbonate exchanger, crucial for intracellular pH regulation in mammalian cells. Specific charged amino acids are essential for its ion transport activity.
Area of Science:
- Molecular Biology
- Cell Physiology
- Biochemistry
Background:
- The slc4a10 gene's precise function as a sodium-dependent bicarbonate importer was unclear.
- Understanding its transport mechanism is vital for cellular homeostasis.
Purpose of the Study:
- To elucidate the exact transport mechanism and ion stoichiometry of the slc4a10 gene product.
- To identify key amino acid residues involved in slc4a10-mediated transport.
Main Methods:
- Intracellular pH (pH(i)) recordings using BCECF fluorometry in slc4a10-transfected NIH-3T3 fibroblasts.
- Measurements of intracellular sodium concentration using CoroNa Green.
- Site-directed mutagenesis of charged amino acids within the slc4a10 gene.
Main Results:
- slc4a10 expression facilitated significant Na(+)-dependent pH(i) recovery with a 1:2 Na(+):HCO(3)(-) stoichiometry.
- Electroneutrality is maintained by chloride (Cl(-)) as the counterion, confirmed by experiments in Cl(-)-depleted cells and DIDS-sensitive (36)Cl(-) efflux.
- Mutagenesis studies revealed that specific charged amino acids (E890, E892, H976, H980) are critical for slc4a10 function, with quadruple mutants completely losing activity.
Conclusions:
- The slc4a10 gene encodes a Na(+)-dependent Cl(-)/HCO(3)(-) exchanger.
- Four specific charged amino acids are essential for the ion transport activity of slc4a10.
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