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

Abstract

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.

Dietary phenylalanine-improved intestinal barrier health in young grass carp (Ctenopharyngodon idella) is associated with increased immune status and regulated gene expression of cytokines, tight junction proteins, antioxidant enzymes and related signalling molecules

“…In humans, Phe deficiency reduced serum insulin concentrations [63]. It was reported that low insulin concentrations decreased TOR expression in the muscle cells of rainbow trout (Oncorhynchus mykiss) [64]. These observations suggested that Phe may modulate the expression of TOR partly through affecting insulin production, which awaits further investigation.…”

Autophagy as a defense strategy against stress: focus on Paracentrotus lividus sea urchin embryos exposed to cadmium

“…Several studies indicate that autophagy plays a key role in controlling muscle mass by protein degradation (Mommsen 2004;Salem et al 2006;Seiliez et al 2012). Most components of autophagy and its associated signaling pathways (AKT1, TOR, AMPK, FOXO) are evolutionarily conserved in the rainbow trout (Polakof et al 2011;Seiliez et al 2008;Seiliez et al 2012). Using qRT-PCR and Western blot analysis, Seiliez and colleagues were able to demonstrate that fasting fish or serum depletion of trout myocytes strongly induces the expression of several major genes involved in autophagy (LC3B, gabarapl1, atg12l, atg4b), suggesting that autophagy is acting as a cell survival mechanism to provide the energy and the nutrients essential for allowing fish to survive during nutritional starvation (Seiliez et al 2010).…”

Postprandial molecular responses in the liver of the barramundi, Lates calcarifer

“…Primary antibodies for the analysis of the insulin signaling pathway were obtained from Cell Signaling Technologies (Akt-p #9272; Akt #9271; mTOR-p #2972; mTOR#2971S; S6-p #4856S; S6 #2217S). All were used at a dilution of 1:1000 and have previously been shown to cross-react with rainbow trout proteins of interest (Seiliez et al 2008). After incubation with a goat anti-rabbit IRDye infrared secondary antibody (LI-COR Inc. Biotechnology), bands were visualized and quantified by Infrared fluorescence using the OdysseyH Imaging System (LI-COR Inc.…”