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Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/23/2010 Publication Date: 7/1/2010 Citation: Cleveland, B.M., Evenhuis, J. 2010. Molecular characterization of atrogin-1/F-box protein-32 (FBXO32) and F-box protein 25 (FBXO25) in rainbow trout (Oncorhynchus mykiss); expression across tissues in response to feed deprivation. Comparative Biochemistry and Physiology. 157:248-257. Interpretive Summary: Reducing rates of protein degradation can have significant impacts on fish growth performance and feed efficiency. To minimize protein degradation first requires an understanding of factors that regulate this process. One such factor is an enzyme called atrogin1, that may control the rate of protein degradation. Here, the full-length rainbow trout atrogin1 sequence was characterized and the effects of feed deprivation on its abundance were determined. The rainbow trout atrogin1 sequence was highly similar to homologous proteins in other fishes and mammals, indicating that its function is likely conserved across species. Atrogin1 abundance was up-regulated in atrophying tissues and down-regulated in tissues critical for nutrient metabolism and excretion. These results suggest that improvements in protein retention may be achieved by suppressing levels of atrogin1, which would reduce the capacity to degrade proteins and subsequently improve growth and feed efficiency. Technical Abstract: The characteristic increase in protein catabolism during muscle atrophy is largely the result of an increase in E3 ubiquitin ligase expression, specifically that of atrogin-1, or FBXO32, which functions to polyubiquitinate proteins. In rainbow trout, the cDNA sequences of two E3 ubiquitin ligase F-box proteins, FBXO32 and FBXO25, were characterized and their expression across tissues in response to feed deprivation was determined. The cDNA sequence for FBXO32 encodes a protein 355 amino acids long with a 97% identity to the homologous protein in salmon, 85% in zebrafish and a 72% identity to that in both human and mouse. The cDNA for FBXO25 encodes a protein 356 amino acids in length that is 98% similar to the homologous protein in salmon, 84% in zebrafish, and 75% in human. Feed deprivation increased FBXO32 expression by approximately 13-fold, 3-fold, and 5-fold in white muscle, red muscle, and intestine, respectively (P<0.05). Expression of FBXO32 and FBXO25 in kidney decreased 0.3-fold and 0.2-fold, respectively, and FBXO25 expression decreased by 0.2-fold in liver (P<0.05). These results indicate that these protein sequences are conserved and suggest that the up-regulation of FBXO32 is significant for skeletal and smooth muscle atrophy that occurs during fasting. |
