Induction of protein catabolism in myotubes by 15(S)-hydroxyeicosatetraenoic acid through increased expression of the ubiquitin-proteasome pathway


The potential role of 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) as an intracellular signal for increased protein catabolism and induction of the expression of key components of the ubiquitin-proteasome proteolytic pathway induced by a tumour cachectic factor, proteolysis-inducing factor has been studied in murine C2C12 myotubes. 15(S)-HETE induced protein degradation in these cells with a maximal effect at concentrations between 78 and 312 nM. The effect was attenuated by the polyunsaturated fatty acid, eicosapentaenoic acid (EPA). There was an increase in 'chymotrypsin-like' enzyme activity, the predominant proteolytic activity of the proteasome, in the same concentration range as that inducing total protein degradation, and this effect was also attenuated by EPA. 15(S)-hydroxyeicosatetraenoic acid also increased maximal expression of mRNA for proteasome subunits C2 and C5, as well as the ubiquitin-conjugating enzyme, E214k, after 4 h incubation, as determined by quantitative competitive RT-PCR. The concentrations of 15-HETE affecting gene expression were the same as those inducing protein degradation. Western blotting of cellular supernatants of myotubes treated with 15(S)-HETE for 24 h showed increased expression of p42, an ATPase subunit of the regulatory complex at similar concentrations, as well as a decrease in expression of myosin in the same concentration range. 15(S)-hydroxyeicosatetraenoic acid activated binding of nuclear factor-κB (NF-κB) in the myotube nucleus and stimulated degradation of 1-κBα. The effect on the NF-κB/1-κBα system was attenuated by EPA. In addition, the NF-κB inhibitor peptide SN50 attenuated the increased chymotrypsin-like enzyme activity in the presence of 15(S)-HETE. These results suggest that 15(S)-HETE induces degradation of myofibrillar proteins in differentiated myotubes through an induction of an increased expression of the regulatory components of the ubiquitin-proteasome proteolytic pathway possibly through the intervention of the nuclear transcription factor NF-κB, and that this process is inhibited by EPA. © 2003 Cancer Research UK.

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Divisions: College of Health & Life Sciences > Aston Pharmacy School
College of Health & Life Sciences > Chronic and Communicable Conditions
College of Health & Life Sciences
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Uncontrolled Keywords: 15(S)-hydroxyeicosatetraenoic acid (15-HETE),nuclear factor-κB (NF-κB),protein catabolism,protenscore induction,Cancer Research,Oncology
Publication ISSN: 1532-1827
Last Modified: 27 Feb 2024 08:08
Date Deposited: 19 Aug 2019 08:49
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
http://www.natu ... l/6601184a.html (Publisher URL)
PURE Output Type: Article
Published Date: 2003-08-18
Authors: Whitehouse, A.S.
Khal, J.
Tisdale, Michael J.

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