Induction of MuRF1 is essential for TNF-alpha-induced loss of muscle function in mice.

Abstract

BACKGROUND:

Humoral circulating inflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha) can impair skeletal muscle contractility. Furthermore, TNF-alpha expression correlates with elevated levels of atrogin-like muscle-specific ubiquitin E3 ligases, which are presumed to mediate muscle protein breakdown and atrophy. However, the casual relationships between MuRF1 and TNF-alpha and their relative contributions to muscle function impairment are not known.

METHODS:

TNF-alpha or saline was injected into either C57Bl6 or MuRF1(-/-) mice. After 16-24 h, the expression of MuRF1 in skeletal muscle was quantified by quantitative reverse transcription-PCR and Western blot analysis. Muscle function was measured in an organ bath. To obtain a broader overview on potential alterations, two-dimensional gel electrophoresis was performed.

RESULTS:

Wild-type animals injected with TNF-alpha had higher MuRF1 mRNA expression (saline versus TNF-alpha: 56.6+/-12.1 versus 133.6+/-30.3 arbitrary units; p<0.05) and protein expression (saline versus TNF-alpha: 0.38+/-0.11 versus 1.07+/-0.25 arbitrary units; p<0.05) as compared to saline-injected littermates. Furthermore, TNF-alpha reduced force development at 150 Hz by 25% in C57Bl6 animals (saline versus TNF-alpha: 2412+/-120 versus 1799+/-114 g/cm(2); p<0.05), but not in MuRF1(-/-) mice (saline versus TNF-alpha: 2424+/-198 versus 2431+/-180 g/cm(2); p=NS). Proteome analysis revealed a significant down-regulation of fast skeletal muscle troponin T in wild-type animals treated with TNF-alpha as compared to MuRF1(-/-) mice that received TNF-alpha.

CONCLUSION:

The results of this study demonstrate for the first time that TNF-alpha-induced reduction in skeletal muscle force development depends on the induction of the atrophy-related E3 ubiquitin ligase MuRF1. A link for the reduction in muscle force may be the TNF-alpha/MuRF1-mediated down-regulation of fast skeletal muscle troponin T.

• Authors: Volker Adams, Norman Mangner, Alexander Gasch, Christian Krohne, Stephan Gielen, Stephanie Hirner, Hermann-Josef Thierse, Christian C Witt, Axel Linke, Gerhard Schuler, Siegfried Labeit
• Journal: Journal of molecular biology (J Mol Biol) Vol. 384 Issue 1 Pg. 48-59 (Dec 05 2008) ISSN: 1089-8638 [Electronic] Netherlands
• PMID: 18804115 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Eukaryotic Initiation Factor-4E
• Muscle Proteins
• Peptide Elongation Factor 1
• Tripartite Motif Proteins
• Troponin T
• Tumor Necrosis Factor-alpha
• Ubiquitin
• Trim63 protein, mouse
• Ubiquitin-Protein Ligases

Topics

• Animals
• Cell Line
• Down-Regulation (drug effects)
• Eukaryotic Initiation Factor-4E (metabolism)
• Immunoprecipitation
• In Vitro Techniques
• Mice
• Models, Biological
• Muscle Contraction (drug effects)
• Muscle Fibers, Skeletal (cytology, drug effects, metabolism)
• Muscle Proteins (genetics, metabolism)
• Muscle, Skeletal (cytology, drug effects, physiology)
• Peptide Elongation Factor 1 (metabolism)
• Tripartite Motif Proteins
• Troponin T (metabolism)
• Tumor Necrosis Factor-alpha (pharmacology)
• Ubiquitin (metabolism)
• Ubiquitin-Protein Ligases (genetics, metabolism)