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  Up-regulation of sodium pump activity in Xenopus laevis oocytes by expression of heterologous beta 1 subunits of the sodium pump

Schmalzing, G., Gloor, S., Omay, H., Kröner, S., & Appelhans, H. (1991). Up-regulation of sodium pump activity in Xenopus laevis oocytes by expression of heterologous beta 1 subunits of the sodium pump. Biochemical Journal, 279(2), 329-336. doi:10.1042/bj2790329.

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Schmalzing, Günther1, Author           
Gloor, Sergio2, Author
Omay, Halit1, Author           
Kröner, Silke1, Author           
Appelhans, Heribert1, Author           
Affiliations:
1Department of Cell Physiology, Max Planck Institute of Biophysics, Max Planck Society, ou_3264817              
2Department of Neurobiology, Swiss Federal Institute of Technology, Hönggerberg, CH-8093 Zürich, Switzerland, ou_persistent22              

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 Abstract: Recent evidence suggests that the beta subunit of the Na+ pump is essential for the alpha subunit to express catalytic activity and for assembly of the holoenzyme in the plasma membrane. We report here that injection into Xenopus laevis oocytes of cRNAs specific for beta 1 subunit isoforms of the Na+ pump of four species (Torpedo californica, chicken, mouse and rat) causes a time-dependent increase in the number of ouabain-binding sites, both in the plasma membrane and in internal membranes. Expression of the beta 1 subunit of the Na+ pump of mouse and rat in the oocytes could be substantiated by immunoprecipitation using a polyclonal antiserum against the mouse beta 1 subunit. Scatchard analysis in permeabilized cells disclosed that the affinity for ouabain is unchanged after expression of each of the beta 1 subunits. A proportional increase in ouabain-sensitive 86Rb+ uptake indicates that the additionally expressed ouabain-binding sites on the cell surface represent functional Na+ pumps. The findings support the concept of Geering. Theulaz, Verrey, Häuptle & Rossier [(1989) Am. J. Physiol. 257, C851-C858] that beta 1 subunits expressed in oocytes associate with an excess of endogenous alpha subunits of the Na+ pump to form a hybrid enzyme. In addition, all of the beta 1 isoforms investigated in the present study were also capable of combining with the co-expressed alpha 1 subunit of the Torpedo Na+ pump to produce a functional enzyme. Injection of cRNA encoding for the Torpedo alpha 1 subunit alone had no effect on the ouabain-binding capacity of the surface and intracellular membranes of the oocyte.

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Language(s): eng - English
 Dates: 1991-05-201991-04-171991-05-211991-10-15
 Publication Status: Published in print
 Pages: 8
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1042/bj2790329
PMID: 1719955
 Degree: -

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Title: Biochemical Journal
Source Genre: Journal
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Publ. Info: London : Published by Portland Press on behalf of the Biochemical Society.
Pages: - Volume / Issue: 279 (2) Sequence Number: - Start / End Page: 329 - 336 Identifier: ISSN: 0264-6021
CoNE: https://pure.mpg.de/cone/journals/resource/110992357308158