Changes in expression of proteolytic genes in response to anabolic and catabolic signals in rainbow trout

Authors: Cleveland, Beth; Silverstein, Jeffrey; Weber, Gregory - Greg

Submitted to: American Fisheries Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/30/2009
Publication Date: 8/30/2009
Citation: Cleveland, B.M., Silverstein, J., Weber, G.M. 2009. Changes in expression of proteolytic genes in response to anabolic and catabolic signals in rainbow trout. American Fisheries Society Annual Meeting.

Interpretive Summary:

Technical Abstract: Rates of protein accrual are largely affected by rates of protein degradation. Determining how proteolytic pathways are affected by catabolic and anabolic signals will contribute to the understanding of the impact and regulation these pathways have on protein turnover. Real time RT-PCR was used to investigate changes in expression of proteolytic genes in rainbow trout (Oncorhynchus mykiss) in response to feed deprivation, anabolic hormones, or both. After two weeks of feed deprivation white muscle expression of the cathepsins and the ubiquitin ligase protein F-box were increased 50% and 500%, respectively. Treatment with insulin-like growth factor (IGF-I) reduced weight loss during feed deprivation and prevented the upregulation of these genes, suggesting that IGF-I reduced protein loss by reducing the capacity for proteolysis via the proteasome and cathepsin pathways. Mechanisms for the actions of metabolic hormones were investigated further using myocyte cell culture. Myocyte treatment with IGF-I or insulin reduced expression of the ubiquitin ligase proteins F-box and MuRF in a dose-dependent manner via PI3K/AKT activation and FOXO phosphorylation. Therefore, the anabolic properties of these hormones partially results from their ability to reduce protein degradation by decreasing transcription of ubiquitin ligases, which target proteins to the proteasome. Additionally, F-box mRNA abundance in liver and muscle was positively correlated with feed conversion (feed/gain) and negatively correlated with body weight in liver, suggesting that a reduced capacity to degrade proteins results in better feed conversion and growth performance.