Kinetic characterization of a stably expressed novel Na+/H+ exchanger (NHE-2)

Tatsuya Honda, Susan M. Knobel, Nada M. Bulus, Fayez K. Ghishan

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

We have recently reported the molecular cloning, sequencing and tissue distribution of a novel Na+/H+ exchanger (NHE-2). The cDNA for NHE-2 was cloned by screening a rat intestinal cDNA library. This clone was unique due to the fact that it lacks the first two transmembrane domains which are present in the other Na+/H+ exchanger isoforms (NHE-1, NHE-3, NHE-4). This structural change in the cDNA offered a unique opportunity to study in detail the properties of this stably expressed cDNA in chinese lung fibroblasts that lack the Na+/H+ exchanger (PS120) cells. Amiloride-sensitive Na+ uptake was linear up to 2 min in PS120 cells transfected with the cDNA. Kinetics of the amiloride-sensitive Na+ uptake showed a Vmax of 24.7 ± 5 nmol/μl ICW per min and a Km of 33.1 ± 2.0 mM. The inhibitory constant (KI) for amiloride and its analogue 5-N-ethyl-N-isopropylamiloride (EIPA) was 0.15 μM and 0.66 μM, respectively. Epidermal growth factor, a known stimulator of NHE-1, also upregulated the expressed NHE-2. These results characterize the kinetic properties of this unique exchanger and suggests that the first two transmembrane domains of the Na+/H+ exchanger isoforms are not essential for the expression of amiloride-sensitive Na+ uptake.

Original languageEnglish (US)
Pages (from-to)199-202
Number of pages4
JournalBBA - Biomembranes
Volume1150
Issue number2
DOIs
StatePublished - Aug 15 1993
Externally publishedYes

Keywords

  • Expression
  • Intestinal transport
  • Kinetics
  • Sodium ion-proton exchanger

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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