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

2008 ◽  
Vol 295 (1) ◽  
pp. R329-R335 ◽  
Author(s):  
Iban Seiliez ◽  
Jean-Charles Gabillard ◽  
Sandrine Skiba-Cassy ◽  
Daniel Garcia-Serrana ◽  
Joaquim Gutiérrez ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Amino Acid ◽  
Mammalian Target Of Rapamycin ◽  
Mrna Translation ◽  
Target Of Rapamycin ◽  
Nutritional Regulation ◽  
Tor Signaling ◽  
Meal Feeding

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.

scholarly journals Mechanisms involved in the nutritional regulation of mRNA translation: features of the avian model

2006 ◽  
Vol 19 (1) ◽  
pp. 104-116 ◽  
Author(s):  
Sophie Tesseraud ◽  
Mourad Abbas ◽  
Sophie Duchene ◽  
Karine Bigot ◽  
Pascal Vaudin ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Growth ◽  
Mammalian Target Of Rapamycin ◽  
Mrna Translation ◽  
Initiation Factor ◽  
Nutritional Regulation ◽  
Translational Repressor

Abstract:Insulin and amino acids are key factors in regulating protein synthesis. The mechanisms of their action have been widely studied for several years. The insulin signal is mediated by the activation of intracellular kinases such as phosphatidylinositol–3'kinase and the mammalian target of rapamycin (mTOR), affecting the phosphorylation of some major effectors involved in the regulation of translation initiation, i.e. p70 S6 kinase (p70S6K) and the translational repressor eukaryotic initiation factor 4E binding protein (4E-BP1). The amino acid–induced signalling cascade also originates from mTOR and promotes p70S6K and 4E–BP1 activation. However, the mechanisms of regulation are complex and little understood, especially in vivo. Elucidating these mechanisms is important for both fundamental physiology and nutritional applications, i.e. better control of the use of nutrients and optimisation of dietary amino acid supplies in various physiological and physiopathological situations. In comparative physiology, the chicken is an interesting model to gain better understanding of the nutritional regulation of mRNA translation because of the very high rates of muscle growth and protein synthesis, and the unusual features compared with mammals. In the present review we provide an overview of the roles of insulin and amino acids as regulators of protein synthesis in both mammals and avian species.

scholarly journals The Rapamycin-Binding Domain Governs Substrate Selectivity by the Mammalian Target of Rapamycin

2002 ◽  
Vol 22 (21) ◽  
pp. 7428-7438 ◽  
Author(s):  
Lloyd P. McMahon ◽  
Kin M. Choi ◽  
Tai-An Lin ◽  
Robert T. Abraham ◽  
John C. Lawrence
Keyword(s):  
Translation Initiation ◽  
Mammalian Target Of Rapamycin ◽  
Mrna Translation ◽  
Binding Domain ◽  
Target Of Rapamycin ◽  
Substrate Selectivity ◽  
Hydrophobic Amino Acid ◽  
Translational Regulators ◽  
Mtor Activity

ABSTRACT The mammalian target of rapamycin (mTOR) is a Ser/Thr (S/T) protein kinase, which controls mRNA translation initiation by modulating phosphorylation of the translational regulators PHAS-I and p70S6K. Here we show that in vitro mTOR is able to phosphorylate these two regulators at comparable rates. Both (S/T)P sites, such as Thr36, Thr45, and Thr69 in PHAS-I and the h(S/T)h site (where h is a hydrophobic amino acid) Thr389 in p70S6K, were phosphorylated. Rapamycin-FKBP12 inhibited mTOR activity. Surprisingly, the extent of inhibition depended on the substrate. Moreover, mutating Ser2035 in the rapamycin-binding domain (FRB) not only decreased rapamycin sensitivity as expected but also dramatically affected the sites phosphorylated by mTOR. The results demonstrate that mutations in Ser2035 are not silent with respect to mTOR activity and implicate the FRB in substrate recognition. The findings also impose new limitations on interpreting results from experiments in which rapamycin and/or rapamycin-resistant forms of mTOR are used to investigate mTOR function in cells.

scholarly journals Identification of mammalian target of rapamycin as a direct target of fenretinide both in vitro and in vivo

2012 ◽  
Vol 33 (9) ◽  
pp. 1814-1821 ◽  
Author(s):  
H. Xie ◽  
F. Zhu ◽  
Z. Huang ◽  
M.-H. Lee ◽  
D. J. Kim ◽  
...  
Keyword(s):  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin ◽  
Direct Target

scholarly journals Differential Antitumoral Properties and Renal-Associated Tissue Damage Induced by Tacrolimus and Mammalian Target of Rapamycin Inhibitors in Hepatocarcinoma: In Vitro and In Vivo Studies

PLoS ONE ◽  
2016 ◽  
Vol 11 (8) ◽  
pp. e0160979 ◽  
Author(s):  
Elena Navarro-Villarán ◽  
José Tinoco ◽  
Granada Jiménez ◽  
Sheila Pereira ◽  
Jize Wang ◽  
...  
Keyword(s):  
Tissue Damage ◽  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin ◽  
In Vivo Studies

scholarly journals Inhibitors of mammalian target of rapamycin downregulate MYCN protein expression and inhibit neuroblastoma growth in vitro and in vivo

Oncogene ◽  
2007 ◽  
Vol 27 (20) ◽  
pp. 2910-2922 ◽  
Author(s):  
J I Johnsen ◽  
L Segerström ◽  
A Orrego ◽  
L Elfman ◽  
M Henriksson ◽  
...  
Keyword(s):  
Protein Expression ◽  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin

Effects of the Mammalian Target of Rapamycin Inhibitor Everolimus on Hepatitis C Virus Replication In Vitro and In Vivo

2017 ◽  
Vol 49 (8) ◽  
pp. 1947-1955 ◽  
Author(s):  
A. Frey ◽  
E.-M. Ecker ◽  
K. Piras-Straub ◽  
A. Walker ◽  
T.G. Hofmann ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Virus Replication ◽  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin

scholarly journals Mammalian target of rapamycin is a direct target for protein kinase B: identification of a convergence point for opposing effects of insulin and amino-acid deficiency on protein translation

1999 ◽  
Vol 344 (2) ◽  
pp. 427-431 ◽  
Author(s):  
Barbara T. NAVÉ ◽  
D. Margriet OUWENS ◽  
Dominic J. WITHERS ◽  
Dario R. ALESSI ◽  
Peter R. SHEPHERD
Keyword(s):  
Amino Acid ◽  
Protein Kinase ◽  
Protein Kinase B ◽  
Mammalian Target Of Rapamycin ◽  
Protein Translation ◽  
Target Of Rapamycin ◽  
Direct Target ◽  
Regulatory Effects ◽  
Stimulation Of

Growth factor induced activation of phosphoinositide 3-kinase and protein kinase B (PKB) leads to increased activity of the mammalian target of rapamycin (mTOR). This subsequently leads to increased phosphorylation of eIF4E binding protein-1 (4EBP1) and activation of p70 ribosomal S6 protein kinase (p70S6K), both of which are important steps in the stimulation of protein translation. The stimulation of translation is attenuated in cells deprived of amino acids and this is associated with the attenuation of 4EBP1 phosphorylation and p70S6K activation. It has been suggested that PKB regulates mTOR function by phosphorylation although direct phosphorylation of mTOR by PKB has not been demonstrated previously. In the present work, we have found that PKB directly phosphorylates mTOR and, using phosphospecific antibodies, we have shown this phosphorylation occurs at Ser2448. Insulin also induces phosphorylation on Ser2448 and this effect is blocked by wortmannin but not rapamycin, consistent with the effect being mediated by PKB. Amino-acid starvation rapidly attenuated the reactivity of the Ser2448 phosphospecific antibody with mTOR and this could not be restored by either insulin stimulation of cells or incubation with PKB in vitro. Our findings demonstrate that mTOR is a direct target for PKB and support the conclusion that regulation of phosphorylation of Ser2448 is a point of convergence for the counteracting regulatory effects of growth factors and amino acid levels.

scholarly journals mTORC1-Activated S6K1 Phosphorylates Rictor on Threonine 1135 and Regulates mTORC2 Signaling

2009 ◽  
Vol 30 (4) ◽  
pp. 908-921 ◽  
Author(s):  
Louis-Andre Julien ◽  
Audrey Carriere ◽  
Julie Moreau ◽  
Philippe P. Roux
Keyword(s):  
Ribosome Biogenesis ◽  
Cellular Localization ◽  
Glycogen Synthase ◽  
Mammalian Target Of Rapamycin ◽  
Mrna Translation ◽  
Growth Factor Signaling ◽  
Mtorc1 Signaling ◽  
Ribosomal S6 Kinase

ABSTRACT The mammalian target of rapamycin (mTOR) is a conserved Ser/Thr kinase that forms two functionally distinct complexes important for nutrient and growth factor signaling. While mTOR complex 1 (mTORC1) regulates mRNA translation and ribosome biogenesis, mTORC2 plays an important role in the phosphorylation and subsequent activation of Akt. Interestingly, mTORC1 negatively regulates Akt activation, but whether mTORC1 signaling directly targets mTORC2 remains unknown. Here we show that growth factors promote the phosphorylation of Rictor (rapamycin-insensitive companion of mTOR), an essential subunit of mTORC2. We found that Rictor phosphorylation requires mTORC1 activity and, more specifically, the p70 ribosomal S6 kinase 1 (S6K1). We identified several phosphorylation sites in Rictor and found that Thr1135 is directly phosphorylated by S6K1 in vitro and in vivo, in a rapamycin-sensitive manner. Phosphorylation of Rictor on Thr1135 did not affect mTORC2 assembly, kinase activity, or cellular localization. However, cells expressing a Rictor T1135A mutant were found to have increased mTORC2-dependent phosphorylation of Akt. In addition, phosphorylation of the Akt substrates FoxO1/3a and glycogen synthase kinase 3α/β (GSK3α/β) was found to be increased in these cells, indicating that S6K1-mediated phosphorylation of Rictor inhibits mTORC2 and Akt signaling. Together, our results uncover a new regulatory link between the two mTOR complexes, whereby Rictor integrates mTORC1-dependent signaling.

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