Previous studies provided evidence that sepsis is associated with increased ubiquitin-proteasome-dependent protein breakdown in skeletal muscle. The 14-kDa ubiquitin-conjugating enzyme (E2_14k) has been proposed to be a key regulator of the ubiquitin proteolytic pathway. We tested the hypothesis that E2_14k message and protein levels are increased in skeletal muscle during sepsis. Sepsis was induced in rats by cecal ligation and puncture (CLP). Control rats were sham operated. E2_14k mRNA and protein levels were quantitated after Northern and Western blot analysis, respectively, 16 h after CLP or sham operation. Sepsis resulted in a 70% increase in the 1.2-kb E2_14k transcript in the fast-twitch extensor digitorum longus muscle, whereas no changes were seen in the slow-twitch soleus muscle. E2_14k protein levels were not influenced by sepsis in any of the muscles studied. Although the changes in the expression of the E2_14k 1.2-kb transcript paralleled the differential effect of sepsis on protein breakdown in fast- and slow-twitch muscle, the potential role of E2_14k in the regulation of sepsis-induced muscle proteolysis needs to be interpreted with caution, because the results demonstrated that increased message levels were not associated with increased E2_14k protein levels.

proteolysis; cachexia; proteasome

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