Functional characterization of the human intestinal NaPi-IIb cotransporter in hamster fibroblasts and Xenopus oocytes

Hua Xu, Michael Inouye, Timothy Missey, James F. Collins, Fayez K. Ghishan

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

The recently cloned NaPi-IIb cotransporter is an apical membrane protein that is involved in the absorption of phosphate in the intestine. To expedite functional and structural studies, the human intestinal NaPi-IIb cotransporter was stably expressed in hamster fibroblast (PS120) cells. The hNaPi-IIb cDNA stably transfected cells exhibited a 1.8-fold higher sodium-dependent phosphate uptake than vector DNA transfected cells, and had a Km for Pi of ∼106 μM and a Km for Na+ of ∼34 mM. The hNaPi-IIb cotransporter was also expressed in Xenopus oocytes and it exhibited a Km for Pi of ∼113 μM and a Km for Na+ of ∼65 mM. The hNaPi-IIb cotransporter expressed in both PS120 cells and oocytes was inhibited by high external pH. Furthermore, the phosphate uptake mediated by the hNaPi-IIb cotransporter was inhibited by 5 mM phosphonoformic acid (PFA), 1 mM arsenate and 100 nM phorbol myristate acetate (PMA). These results demonstrate that the human intestinal NaPi-IIb cotransporter is functional when expressed in hamster fibroblasts, and that this model system may be useful in the future to identify NaPi-IIb cotransporter-specific inhibitors.

Original languageEnglish (US)
Pages (from-to)97-105
Number of pages9
JournalBiochimica et Biophysica Acta - Biomembranes
Volume1567
Issue numberSUPPL.
DOIs
StatePublished - Dec 23 2002

Keywords

  • PS120 cell
  • Type IIb sodium-phosphate cotransporter
  • Xenopus oocyte

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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