title: Atrophy-related ubiquitin ligases, atrogin-1 and MuRF1 are up-regulated in aged rat Tibialis Anterior muscle.
abstract: A phenotypic feature of aging is skeletal muscle wasting. It is characterized by a loss of muscle mass and strength. Age-related loss of muscle mass occurs through a reduction in the rate of protein synthesis, an increase in protein degradation or a combination of both. However, the underlying mechanism is still poorly understood. To test the hypothesis that the ubiquitin-proteasome pathway contributes to this phenomenon, we studied MuRF1 and atrogin-1 expression in Tibialis Anterior muscle of aged rats. These two E3 ligases are considered as sensitive markers of muscle protein degradation by the ubiquitin-proteasome system. Our results revealed that, in skeletal muscle of aged rats, the decline in muscle mass is accompanied by an increase in the level of oxidized proteins and ubiquitin conjugates (90%) whereas the functionality of the proteasome remains constant compared to young rats. Furthermore, the level of both MuRF1 and atrogin-1 mRNA is markedly up-regulated in aged muscle (respectively x2 and x2.5). Taken together these data argue for the involvement of the ubiquitin-proteasome pathway in sarcopenia of fast-twitch muscle, in particular through increased expression of MuRF1 and atrogin-1. Moreover, we observed a decrease in the IGF-1/Akt signalling pathways and elevated level of TNFalpha mRNA in aged rat muscle. Therefore, IGF-1/Akt and TNFalpha represent potential mediators implicated in the regulation of MuRF1 and atrogin-1 genes during aging.
authors.affiliation: Laboratoire de Physiologie Cellulaire et Moléculaire, CNRS UMR 6548, Faculté des Sciences, Université de Nice Sophia Antipolis, 28 Avenue Valrose, 06108 Nice Cedex 2, France.
authors.forename: Stephan
authors.initials: S
authors.lastname: Clavel
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Coldefy
authors.forename: Emilie
authors.initials: E
authors.lastname: Kurkdjian
authors.forename: Jérôme
authors.initials: J
authors.lastname: Salles
authors.forename: Irène
authors.initials: I
authors.lastname: Margaritis
authors.forename: Benoît
authors.initials: B
authors.lastname: Derijard
mesh_terms: D000375:Aging; D000818:Animals; D002244:Carbon / Q000737:chemistry; D005786:Gene Expression Regulation; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism*; D018384:Oxidative Stress; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D044843:SKP Cullin F-Box Protein Ligases / Q000096:biosynthesis*; D015398:Signal Transduction; D000070584:Tripartite Motif Proteins; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000096:biosynthesis*
chemical_list: D009124:Muscle Proteins; D000070584:Tripartite Motif Proteins; D014409:Tumor Necrosis Factor-alpha; D007334:Insulin-Like Growth Factor I; D002244:Carbon; C486692:Fbxo32 protein, rat; D044843:SKP Cullin F-Box Protein Ligases; C499086:Trim63 protein, rat; D044767:Ubiquitin-Protein Ligases; D051057:Proto-Oncogene Proteins c-akt