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Original Paper

Protein Kinase B Alpha (PKBα) Stimulates the Epithelial Sodium Channel (ENaC) Heterologously Expressed in Xenopus laevis Oocytes by Two Distinct Mechanisms

Diakov A. · Nesterov V. · Mokrushina M. · Rauh R. · Korbmacher C.

Author affiliations

Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen

Corresponding Author

Prof. Dr. med. Christoph Korbmacher

Institut für Zelluläre und Molekulare Physiologie

Waldstr. 6, 91054 Erlangen (Germany)

Tel. +49-9131-8522301, Fax +49-9131-8522770

E-Mail christoph.korbmacher@physiologie2.med.uni-erlangen.de

Related Articles for ""

Cell Physiol Biochem 2010;26:913–924

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Kinases contribute to the regulation of the epithelial sodium channel (ENaC) in a complex manner. For example, SGK1 (serum- and glucocorticoid-inducible kinase type 1) enhances ENaC surface expression by phosphorylating Nedd4-2, thereby preventing ENaC retrieval and degradation. An additional mechanism of ENaC activation by SGK1 involves an SGK consensus motif (616RSRYWS621) in the C-terminus of the channel’s Α-subunit. This consensus motif may also be a target for ENaC regulation by protein kinase B Α (PKBΑ) known to be activated by insulin and growth factors. Therefore, we investigated a possible role of PKBΑ in the regulation of rat ENaC heterologously expressed in Xenopus laevis oocytes. We found that recombinant PKBΑ included in the pipette solution increased ENaC currents in outside-out patches by about 4-fold within 15-20 min. Replacing the serine residue S621 of the SGK consensus motif by an alanine (S621A) abolished this stimulatory effect. In co-expression experiments active PKBΑ but not catalytically inactive PKBΑ significantly increased ENaC whole-cell currents and surface expression by more than 50 % within 24 hours of co-expression. Interestingly, this stimulatory effect was preserved in oocytes expressing ENaC with the S621A mutation. We conclude that the acute stimulatory effect of PKBΑ involves a specific kinase consensus motif in the C-terminus of the channel’s Α-subunit. In contrast, the increase in channel surface expression caused by co-expression of PKBΑ does not depend on this site in the channel and is probably mediated by an effect on channel trafficking.

© 2010 S. Karger AG, Basel

Article / Publication Details

First-Page Preview
Abstract of Original Paper

Accepted: October 13, 2010
Published online: January 04, 2011
Issue release date: January 2011

Number of Print Pages: 12
Number of Figures: 0
Number of Tables: 0

ISSN: 1015-8987 (Print)
eISSN: 1421-9778 (Online)

For additional information: http://www.karger.com/CPB

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