Table of Contents
Journal of Amino Acids
Volume 2013 (2013), Article ID 864757, 11 pages
http://dx.doi.org/10.1155/2013/864757
Research Article

Total 4EBP1 Is Elevated in Liver of Rats in Response to Low Sulfur Amino Acid Intake

1Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
2College of Animal Sciences, Zhejiang University, Hangzhou 310058, China

Received 19 April 2013; Accepted 30 July 2013

Academic Editor: Dorothy Gietzen

Copyright © 2013 Angelos K. Sikalidis et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Translation initiation is known to be regulated by the binding of eukaryotic initiation factor 4E (eIF4E) by binding proteins (4EBPs), and there is evidence that amino acid deprivation and other cellular stresses upregulate 4EBP1 expression. To pursue the question of whether diets limited in an essential amino acid lead to induction of 4EBP1 expression in vivo, diets that varied in methionine and cystine content were fed to rats for 7 days, and 4EBP1 mRNA and protein levels and 4EBP1 phosphorylation state were determined. Total 4EBP1 mRNA and protein abundance increased in liver of rats with severely deficient intakes of sulfur amino acids (0.23% or 0.11% methionine without cystine) but not in animals with a less restricted intake of sulfur amino acids (0.11% methionine plus 0.35% cystine) but a similarly restricted intake of total diet (53 to 62% of control). The amount of 4EBP1 binding activity (α + β forms) was elevated in liver of rats fed sulfur amino acid-deficient diets, whereas the hyperphosphorylation of 4EBP1 was not affected by dietary treatment. Results suggest that changes in total 4EBP1 expression should be considered when examining mechanisms that attenuate protein synthesis during amino acid deficiency states.