Protein Kinase B Alpha (PKBα) Stimulates the Epithelial Sodium Channel (ENaC) Heterologously Expressed in Xenopus laevis Oocytes by Two Distinct MechanismsDiakov A. · Nesterov V. · Mokrushina M. · Rauh R. · Korbmacher C.
Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen
Prof. Dr. med. Christoph Korbmacher
Institut für Zelluläre und Molekulare Physiologie
Waldstr. 6, 91054 Erlangen (Germany)
Tel. +49-9131-8522301, Fax +49-9131-8522770
Do you have an account?
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
Copyright / Drug Dosage / DisclaimerCopyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.