Activation of ATP-ubiquitin-dependent proteolysis in skeletal muscle in vivo and murine myoblasts in vitro by a proteolysis-inducing factor (PIF)

M.J. Lorite, Helen J. Smith, J.A. Arnold, A. Morris, M.G. Thompson, Michael J. Tisdale*

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Loss of skeletal muscle is a major factor in the poor survival of patients with cancer cachexia. This study examines the mechanism of catabolism of skeletal muscle by a tumour product, proteolysis-inducing factor (PIF). Intravenous administration of PIF to normal mice produced a rapid decrease in body weight (1.55 ± 0.12 g in 24 h) that was accompanied by increased mRNA levels for ubiquitin, the Mr 14 000 ubiquitin carrier-protein, E2, and the C9 proteasome subunit in gastrocnemius muscle. There was also increased protein levels of the 20S proteasome core and 19S regulatory subunit, detectable by immunoblotting, suggesting activation of the ATP-ubiquitin-dependent proteolytic pathway. An increased protein catabolism was also seen in C2C12 myoblasts within 24 h of PIF addition with a bell-shaped dose-response curve and a maximal effect at 2-4 nM. The enhanced protein degradation was attenuated by anti-PIF antibody and by the proteasome inhibitors MG115 and lactacystin. Glycerol gradient analysis of proteasomes from PIF-treated cells showed an elevation in chymotrypsin-like activity, while Western analysis showed a dose-related increase in expression of MSSI, an ATPase that is a regulatory subunit of the proteasome, with a dose-response curve similar to that for protein degradation. These results confirm that PIF acts directly to stimulate the proteasome pathway in muscle cells and may play a pivotal role in protein catabolism in cancer cachexia. © 2001 Cancer Research Campaign.

Original languageEnglish
Pages (from-to)297-302
Number of pages6
JournalBritish Journal of Cancer
Volume85
Issue number2
DOIs
Publication statusPublished - 11 Aug 2001

Bibliographical note

From twelve months after its original publication, this work is licensed under the Creative Commons Attribution-NonCommercial-Share Alike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/

Keywords

  • cachexia
  • muscle proteolysis
  • proteolysis-inducing factor (PIF)
  • ubiquitin-proteasome proteolysis

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