Effect of starvation on global gene expression and proteolysis in rainbow trout (Oncorhynchus mykiss).
BACKGROUND
Fast, efficiently growing animals have increased protein synthesis and/or reduced protein degradation relative to slow, inefficiently growing animals. Consequently, minimizing the energetic cost of protein turnover is a strategic goal for enhancing animal growth. Characterization of gene expression profiles associated with protein turnover would allow us to identify genes that could potentially be used as molecular biomarkers to select for germplasm with improved protein accretion.


RESULTS
We evaluated changes in hepatic global gene expression in response to 3-week starvation in rainbow trout (Oncorhynchus mykiss). Microarray analysis revealed a coordinated, down-regulated expression of protein biosynthesis genes in starved fish. In addition, the expression of genes involved in lipid metabolism/transport, aerobic respiration, blood functions and immune response were decreased in response to starvation. However, the microarray approach did not show a significant increase of gene expression in protein catabolic pathways. Further studies, using real-time PCR and enzyme activity assays, were performed to investigate the expression of genes involved in the major proteolytic pathways including calpains, the multi-catalytic proteasome and cathepsins. Starvation reduced mRNA expression of the calpain inhibitor, calpastatin long isoform (CAST-L), with a subsequent increase in the calpain catalytic activity. In addition, starvation caused a slight but significant increase in 20S proteasome activity without affecting mRNA levels of the proteasome genes. Neither the mRNA levels nor the activities of cathepsin D and L were affected by starvation.


CONCLUSIONS
These results suggest a significant role of calpain and 20S proteasome pathways in protein mobilization as a source of energy during fasting and a potential association of the CAST-L gene with fish protein accretion.
Salem
Mohamed
M
Laboratory of Animal Biotechnology and Genomics, Division of Animal and Nutritional Sciences, West Virginia University, Morgantown, WV 26505, USA. mohamed.salem@mail.wvu.edu
Silverstein
Jeff
J
Rexroad
Caird E
CE
Yao
Jianbo
J
D000818:Animals; D002135:Calcium-Binding Proteins / Q000502:physiology; D002154:Calpain / Q000502:physiology; D003199:Computer Systems; D004734:Energy Metabolism / Q000235:genetics; D005393:Fish Diseases / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D017686:Oncorhynchus mykiss / Q000235:genetics* / Q000502:physiology; D010447:Peptide Hydrolases / Q000378:metabolism; D016133:Polymerase Chain Reaction; D046988:Proteasome Endopeptidase Complex / Q000502:physiology; D014176:Protein Biosynthesis / Q000235:genetics*; D011506:Proteins / Q000378:metabolism*; D013217:Starvation / Q000235:genetics / Q000378:metabolism / Q000662:veterinary*
D002135:Calcium-Binding Proteins; D011506:Proteins; C033668:calpastatin; D010447:Peptide Hydrolases; D002154:Calpain; D046988:Proteasome Endopeptidase Complex