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The sodium-bicarbonate cotransporter NBCe1 supports glutamine efflux via SNAT3 (SLC38A3) co-expressed in Xenopus oocytes

  • Christina Wendel
  • Holger M. Becker
  • Joachim W. DeitmerEmail author
Cell and Molecular Physiology

Abstract

The glutamine transporter SNAT3 contributes to the glutamine fluxes in liver, kidney, and brain. We heterologously co-expressed SNAT3 with the electrogenic sodium-bicarbonate cotransporter NBCe1 in Xenopus laevis oocytes and measured cytosolic pH and membrane current in voltage clamp. Because of the increased buffer capacity contributed by the NBCe1 (Becker and Deitmer in J Biol Chem 279:28057–28062, 2004), we hypothesized that this may enhance the proton-coupled glutamine transport via SNAT3 in the presence of CO2/\( \operatorname{HCO} _{3} ^{ - } \). Addition and removal of glutamine activated not only SNAT3 but also NBCe1, as indicated by the increased membrane current. The NBCe1 current during glutamine removal was more than 50% larger than during glutamine addition, suggesting that NBCe1 enhances glutamine efflux rather than glutamine uptake. This was confirmed by radio-labeled glutamine flux measurements; influx of glutamine was significantly decreased, whereas efflux of glutamine was increased when SNAT3 was co-expressed with NBCe1. A model is presented that attempts to explain the role of intracellular pH, bicarbonate transport, and buffering capacity mediated by NBCe1 for uptake and efflux of glutamine via SNAT3.

Keywords

Membrane transport Acid/base balance Intracellular pH Bicarbonate transport Protons 

Notes

Acknowledgment

We thank Dr. L. Felipe Barros Olmedo for his valuable comments on an earlier version of this manuscript, and we are grateful for the financial support by grants from the Deutsche Forschungsgemeinschaft (DE 231/16-4; GRK 845).

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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Christina Wendel
    • 1
  • Holger M. Becker
    • 1
  • Joachim W. Deitmer
    • 1
    Email author
  1. 1.Abteilung für Allgemeine ZoologieFB BiologieKaiserslauternGermany

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