Involvement of phosphoinositide 3-kinase and Akt in the induction of muscle protein degradation by proteolysis-inducing factor


In the present study the role of Akt/PKB (protein kinase B) in PIF- (proteolysis-inducing factor) induced protein degradation has been investigated in murine myotubes. PIF induced transient phosphorylation of Akt at Ser(473) within 30 min, which was attenuated by the PI3K (phosphoinositide 3-kinase) inhibitor LY294002 and the tyrosine kinase inhibitor genistein. Protein degradation was attenuated in myotubes expressing a dominant-negative mutant of Akt (termed DNAkt), compared with the wild-type variant, whereas it was enhanced in myotubes containing a constitutively active Akt construct (termed MyrAkt). A similar effect was observed on the induction of the ubiquitin-proteasome pathway. Phosphorylation of Akt has been linked to up-regulation of the ubiquitin-proteasome pathway through activation of NF-kappaB (nuclear factor kappaB) in a PI3K-dependent process. Protein degradation was attenuated by rapamycin, a specific inhibitor of mTOR (mammalian target of rapamycin), when added before, or up to 30 min after, addition of PIF. PIF induced transient phosphorylation of mTOR and the 70 kDa ribosomal protein S6 kinase. These results suggest that transient activation of Akt results in an increased protein degradation through activation of NF-kappaB and that this also allows for a specific synthesis of proteasome subunits.

Publication DOI:
Divisions: College of Health & Life Sciences > Aston Pharmacy School
College of Health & Life Sciences
College of Health & Life Sciences > Chronic and Communicable Conditions
Additional Information: The final version of record is available at
Uncontrolled Keywords: Akt/PKB,protein kinase B,nuclear factor κB,NF-κB,proteasome expression,protein degradation,proteolysis-inducing factor,PIF),phosphoinositide 3-kinase,Biochemistry
Publication ISSN: 1470-8728
Full Text Link: http://www.bioc ... 1/bj4090751.htm
Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2008-02-01
Authors: Russell, Steve T. (ORCID Profile 0000-0002-5491-900X)
Eley, Helen L.
Wyke, Stacey M.
Tisdale, Michael J.



Version: Accepted Version

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