Functional differences between alpha subunit isoforms of the rat Na,K-ATPase expressed in Xenopus oocytes.

Details

Serval ID
serval:BIB_3A936A6FB95D
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Functional differences between alpha subunit isoforms of the rat Na,K-ATPase expressed in Xenopus oocytes.
Journal
Journal of Physiology
Author(s)
Horisberger J.D., Kharoubi-Hess S.
ISSN
0022-3751
Publication state
Published
Issued date
03/2002
Peer-reviewed
Oui
Volume
539
Number
Pt 3
Pages
669-680
Language
english
Abstract
The functional properties of the three most widely distributed alpha subunit isoforms of the Na,K-ATPase are not well known, particularly concerning the voltage dependence of their activity and cation binding kinetics. We measured the electrogenic activity generated by Na,K-ATPases resulting from co-expression of the rat alpha1, alpha2* or alpha3* subunits with the rat beta1 subunit in Xenopus oocytes; alpha2* and alpha3* are ouabain-resistant mutants of the alpha2 and alpha3 isoform, which allowed selective inhibition of the endogenous Na(+),K(+)-pump of the oocyte. In oocytes expressing the three isoforms of the alpha subunit, K(+) induced robust outward currents that were largely ouabain-sensitive. In addition, ouabain-sensitive inward currents were recorded for all three isoforms in sodium-free and potassium-free acid solutions. The very similar voltage dependence of the Na(+),K(+)-pump activity observed in the absence of extracellular Na(+) indicated a similar stoichiometry of the transported cations by the three isoforms. The affinity for extracellular K(+) was slightly lower for the alpha2* and alpha3* than for the alpha1 isoform. The alpha2* isoform was, however, more sensitive to voltage-dependent inhibition by extracellular Na(+), indicating a higher affinity of the extracellular Na(+) site in this isoform. We measured and controlled [Na(+)](i) using a co-expressed amiloride-sensitive Na(+) channel. The intracellular affinity for Na(+) was slightly higher in the alpha2* than in the alpha1 or alpha3* isoforms. These results suggest that the alpha2 isoform could have an activity that is strongly dependent upon [Na(+)](o) and [K(+)](o). These concentrations could selectively modulate its activity when large variations are present, for instance in the narrow intercellular spaces of brain or muscle tissues.
Keywords
Animals, Binding, Competitive, Electric Conductivity, Extracellular Space/metabolism, Female, Oocytes, Potassium/metabolism, Rats/metabolism, Sodium/physiology, Sodium-Potassium-Exchanging ATPase/metabolism, Sodium-Potassium-Exchanging ATPase/physiology, Xenopus laevis
Pubmed
Web of science
Create date
24/01/2008 12:38
Last modification date
20/08/2019 13:30
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