An in vivo and in vitro assessment of TOR signaling cascade in rainbow trout (Oncorhynchus mykiss)

1 INRA, UMR1067 Nutrition Aquaculture et Génomique, F-64310 Saint-Pée-sur-Nivelle, France; 2 INRA, UR1037 Station Commune de Recherches en Ichtyophysiologie Biodiversité et Environnement, Campus de Beaulieu, Rennes, France; 3 Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain; and 4 Institut National de la Recherche Agronomique, UR83 Recherches Avicoles, Nouzilly, France Submitted 28 February 2008 ; accepted in final form 17 April 2008 In mammals, feeding promotes protein accretion in skeletal muscle through a stimulation of the insulin- and amino acid- sensitive mammalian target of rapamycin (mTOR) signaling pathway, leading to the induction of mRNA translation. The purpose of the present study was to characterize both in vivo and in vitro the activation of several major kinases involved in the mTOR pathway in the muscle of the carnivorous rainbow trout. Our results showed that meal feeding enhanced the phosphorylation of the target of rapamycin (TOR), PKB, p70 S6 kinase, and eIF4E-binding protein-1, suggesting that the mechanisms involved in the regulation of mRNA translation are well conserved between lower and higher vertebrates. Our in vitro studies on primary culture of trout muscle cells indicate that insulin and amino acids regulate TOR signaling and thus may be involved in meal feeding effect in this species as in mammals. In conclusion, we report here for the first time in a fish species, the existence and the nutritional regulation of several major kinases involved in the TOR pathway, opening a new area of research on the molecular bases of amino acid utilization in teleosts. feeding; signaling; protein synthesis; muscle; fish Address for reprint requests and other correspondence: I. Seiliez, INRA, UMR1067 Nutrition Aquaculture et Génomique, F-64310 Saint-Pée-sur-Nivelle, France (e-mail: seiliez{at}st-pee.inra.fr )