title: Contribution of the autophagy-lysosomal and ubiquitin-proteasomal proteolytic systems to total proteolysis in rainbow trout (Oncorhynchus mykiss) myotubes.
abstract: The ubiquitin-proteasome system (UPS) is recognized as the major contributor to total proteolysis in mammalian skeletal muscle, responsible for 50% or more of total protein degradation in skeletal muscle, whereas the autophagic-lysosome system (ALS) plays a more minor role. While the relative contribution of these systems to muscle loss is well documented in mammals, little is known in fish species. The current study uses myotubes derived from rainbow trout myogenic precursor cells as an in vitro model of white muscle tissue. Cells were incubated in complete or serum-deprived media or media supplemented with insulin-like growth factor-1 (IGF-1) and exposed to selective proteolytic inhibitors to determine the relative contribution of the ALS and UPS to total protein degradation in myotubes in different culture conditions. Results indicate that the ALS is responsible for 30-34% and 50% of total protein degradation in myotubes in complete and serum-deprived media, respectively. The UPS appears to contribute much less to total protein degradation at almost 4% in cells in complete media to nearly 17% in serum-deprived cells. IGF-1 decreases activity of both systems, as it inhibited the upregulation of both proteolytic systems induced by serum deprivation. The combined inhibition of both the ALS and UPS reduced degradation by a maximum of 55% in serum-deprived cells, suggesting an important contribution of other proteolytic systems to total protein degradation. Collectively, these data identify the ALS as a potential target for strategies aimed at improving muscle protein retention and fillet yield through reductions in protein degradation.
authors.affiliation: Institut National de la Recherche Agronomique, Nutrition Métabolisme Aquaculture, St-Pée-sur-Nivelle, France; and.
authors.forename: Iban
authors.initials: I
authors.lastname: Seiliez
authors.affiliation: Institut National de la Recherche Agronomique, Nutrition Métabolisme Aquaculture, St-Pée-sur-Nivelle, France; and.
authors.forename: Karine
authors.initials: K
authors.lastname: Dias
authors.affiliation: National Center for Cool and Cold Water Aquaculture, Agricultural Research Service/United States Department of Agriculture, Kearneysville, West Virginia beth.cleveland@ars.usda.gov.
authors.forename: Beth M
authors.initials: BM
authors.lastname: Cleveland
mesh_terms: D000818:Animals; D001343:Autophagy / Q000502:physiology*; D001798:Blood Proteins / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008247:Lysosomes / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000254:growth & development; D017686:Oncorhynchus mykiss / Q000502:physiology*; D010447:Peptide Hydrolases / Q000502:physiology*; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000502:physiology*; D059748:Proteolysis / Q000187:drug effects*; D025801:Ubiquitin / Q000502:physiology*
chemical_list: D001798:Blood Proteins; D011480:Protease Inhibitors; D025801:Ubiquitin; D007334:Insulin-Like Growth Factor I; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex
keywords: autophagy; proteasome; protein turnover; proteolysis