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Identification of a region within the Na,K-ATPase alpha subunit that contributes to differential ouabain sensitivity

J R Emanuel1, S Graw, D Housman

  • 1Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510.

Molecular and Cellular Biology
|September 1, 1989
PubMed

Insights

Researchers identified key regions in the sodium-potassium pump (Na,K-ATPase) alpha subunit that determine ouabain sensitivity. These findings pinpoint amino-terminal areas responsible for ouabain resistance in rat alpha 1 and alpha 2 subunits.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Physiology

Background:

  • The sodium-potassium pump (Na,K-ATPase) is crucial for maintaining cellular ion gradients.
  • Ouabain sensitivity varies among Na,K-ATPase alpha subunit isoforms, impacting cellular function and drug response.

Purpose of the Study:

  • To investigate the specific determinants within the Na,K-ATPase alpha subunit responsible for differential ouabain sensitivity.
  • To elucidate the structural basis of ouabain resistance and sensitivity in different alpha subunit isoforms.

Main Methods:

  • Construction and expression of chimeric cDNA molecules between ouabain-resistant and ouabain-sensitive alpha subunit genes.
  • Transfection of chimeric cDNAs into ouabain-sensitive monkey CV-1 cells.
  • Assessment of ouabain resistance through cell survival selection assays.

Main Results:

  • Rat alpha 1 subunit cDNA and specific rat alpha 1/human alpha 1 or rat alpha 1/rat alpha 2 chimeras conferred high-level ouabain resistance (100 microM).
  • Reciprocal chimeras showed sensitivity to low ouabain concentrations (1 microM).
  • Rat alpha 2 subunit cDNA and a rat alpha 2/rat alpha 1 chimera conferred intermediate ouabain resistance (0.5 microM).

Conclusions:

  • Determinants of ouabain resistance are located in the amino-terminal regions of the rat alpha 1 and alpha 2 Na,K-ATPase subunits.
  • Chimeric alpha subunit expression is a valuable tool for understanding Na,K-ATPase structure-function relationships.

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