The Journal of Membrane Biology

, Volume 169, Issue 1, pp 39–44

Characterization of the Fourth α Isoform of the Na,K-ATPase

  • A.L.  Woo
  • P.F.  James
  • J.B.  Lingrel

DOI: 10.1007/PL00005899

Cite this article as:
Woo, A., James, P. & Lingrel, J. J. Membrane Biol. (1999) 169: 39. doi:10.1007/PL00005899

Abstract.

The Na,K-ATPase is a major ion transport protein found in higher eukaryotic cells. The enzyme is composed of two subunits, α and β, and tissue-specific isoforms exist for each of these, α1, α2 and α3 and β1, β2 and β3. We have proposed that an additional α isoform, α4, exists based on genomic and cDNA cloning. The mRNA for this gene is expressed in rats and humans, exclusively in the testis, however the expression of a corresponding protein has not been demonstrated. In the current study, the putative α4 isoform has been functionally characterized as a novel isoform of the Na,K-ATPase in both rat testis and in α4 isoform cDNA transfected 3T3 cells. Using an α4 isoform-specific polyclonal antibody, the protein for this novel isoform is detected for the first time in both rat testis and in transfected cell lines. Ouabain binding competition assays reveal the presence of high affinity ouabain receptors in both rat testis and in transfected cell lines that have identical KD values. Further studies of this high affinity ouabain receptor show that it also has high affinities for both Na+ and K+. The results from these experiments definitively demonstrate the presence of a novel isoform of the Na,K-ATPase in testis.

Key words: Na,K-ATPase —α4 isoform — testis — ouabain — 3T3 cell expression system 

Copyright information

© 1999 Springer-Verlag New York Inc.

Authors and Affiliations

  • A.L.  Woo
    • 1
  • P.F.  James
    • 1
  • J.B.  Lingrel
    • 1
  1. 1.Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, 231 Bethesda Avenue, ML 0524, Cincinnati, OH 45267-0524, USAUS