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Title: Contribution of the autophagy-lysosomal and ubiquitin-proteasomal proteolytic systems to total proteolysis in rainbow trout (Oncorhynchus mykiss) myotubes

Author
item SIELIEZ, IBAN - Institut National De La Recherche Agronomique (INRA)
item DIAS, KARINE - Institut National De La Recherche Agronomique (INRA)
item Cleveland, Beth

Submitted to: American Journal of Physiology - Regulatory Integrative & Comparative Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2014
Publication Date: 12/1/2014
Citation: Sieliez, I., Dias, K., Cleveland, B.M. 2014. Contribution of the autophagy-lysosomal and ubiquitin-proteasomal proteolytic systems to total proteolysis in rainbow trout (Oncorhynchus mykiss) myotubes. American Journal of Physiology - Regulatory Integrative & Comparative Physiology. 307(11):R1330-R1337. DOI: 10.1152/ajpregu.00370.2014.

Interpretive Summary: In fish an increase in body weight is dependent on the continuous accumulation of proteins in white muscle tissue. This requires rates of protein synthesis to exceed rates of protein degradation (proteolysis). There are three independent biological processes associated with protein degradation in fish; it is unknown which process has the largest impact. We developed a model to determine the extent each process reduces total rates of protein degradation. Our data indicate that the lysosome system is responsible for 30-50% of total protein degradation while the proteasome system is responsible for up to 16% of total protein degradation. These findings suggest the lysosome system should be targeted in establishing strategies aiming to improve growth rates and fillet yields.

Technical Abstract: Two major proteolytic systems are thought to (co-) operate in the skeletal muscle of vertebrates, the ubiquitin-proteasomal system (UPS) and the autophagic/lysosomal system (ALS). While their relative contribution to muscle loss has been already well documented in mammals, little is known in fish species. The current study uses primary cell cultures derived from rainbow trout myosatellite cells as an in vitro model of white muscle tissue. Cells were exposed to selective proteolytic inhibitors to determine the relative contribution of the ALS and UPS to total protein degradation in myotubes. The obtained results show that the ALS is responsible for a significant portion of protein degradation, with this value averaging 30-34% in cells in complete media but reaching 50% during serum deprivation. In contrast, 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. Finally, 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 (e.g., calpains) in total protein degradation in our cell culture model. Collectively, these data identify the ALS as a potentially key target for strategies aimed at improving muscle protein retention and fillet yield.