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Chieh Lun Liu*, Yu-Hsuan Kai, Erica Dasi, Aaron Watson, Shau-Chi Chi, Allen R. Place, & Rosemary Jagus
Institute of Marine and Environmental Technology
University of Maryland Center for Environmental Science
Baltimore, MD 21202

The regulation of protein synthesis is a key component of metabolic depression in response to environmental stress for fish. Phosphorylation of eukaryotic translational initiation factor 2 (eIF2) appears to be a general mechanism for inhibiting initiation of protein synthesis. There are four eIF2α-specific kinases in most vertebrates, two of which, GCN2 and PERK, respond to changes in nutritional status. GCN2 is a sensor of amino-acid levels and is the primary eIF2α-kinase that responds to nutritional deprivation. PERK is an endoplasmic reticulum (ER) protein activated by the accumulation of misfolded proteins in the ER, as well as by glucose deprivation and high levels of fatty acids. In aquaculture species, there is increasing pressure to develop cost effective sustainable diets providing high growth rate and product yield. Since

dietary studies are both time consuming and expensive, we have evaluated eIF2α phosphorylation state as potential rapid indicator of diet quality. Preliminary studies in a zebrafish Danio rerio liver cell line (ZFL), laid the groundwork, showing increased phosphorylation of eIF2α in response to nutrient limitation and endoplasmic reticulum stress, consistent with activation of the eIF2α-kinases GCN2 and PERK. A cell line (CM) derived from muscle of cobia, Rachycentron canadum, shows similar responses. Furthermore, initial studies in cobia juveniles have shown that quality of diet affects the phosphorylation state of eIF2α indicating it could have potential as an early marker to evaluate diets and as an analytical tool in determining the basis of nutrient pathologies.   

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