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.

Baicalin Induces Apoptotic Death of Human Chondrosarcoma Cells through Mitochondrial Dysfunction and Downregulation of the PI3K/Akt/mTOR Pathway

Planta Medica ◽  
2018 ◽  
Vol 85 (05) ◽  
pp. 360-369 ◽  
Author(s):  
Minyu Zhu ◽  
Jinwei Ying ◽  
Chaowei Lin ◽  
Yu Wang ◽  
Kelun Huang ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase B ◽  
Tumour Size ◽  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin ◽  
Human Chondrosarcoma ◽  
Apoptotic Death ◽  
Phosphoinositide 3 Kinase

AbstractThe aim of the present study was to investigate the cytotoxic and antitumour effects of baicalin in human chondrosarcoma both in vivo and in vitro. We examined the effects of baicalin on the growth and apoptosis of human chondrosarcoma cells. Baicalin inhibited the growth of SW1353 and CH2879 cells in a dose- and time-dependent manner, but did not inhibit the growth of normal chondrocytes. Baicalin reduced tumour growth and induced apoptotic death in SW1353-transplanted nude mice without reducing their body weight. Further studies showed that baicalin reduced the mitochondrial membrane potential, upregulated the expression of Bax and cytoplasmic cytochrome c, downregulated the expression of Bcl-2 and mitochondrial cytochromes, and activated caspase-3 and caspase-9. Baicalin inhibited the phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin pathway by decreasing the expression of phosphorylated phosphoinositide 3-kinase, phosphorylated protein kinase B, and phosphorylated mammalian target of rapamycin both in vivo and in vitro. Moreover, the mice that received SC79 and baicalin exhibited a greater tumour size compared with the mice that received baicalin. The mice that received LY294002 and baicalin showed a smaller tumour size compared with the mice that received baicalin. In the in vitro study, SC79 and LY294002 affected the baicalin-induced cytotoxic effects on chondrosarcoma cells in the same manner. Our data suggest baicalin has therapeutic efficacy in human chondrosarcoma through the induction of apoptosis and inhibition of the phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin pathway. Baicalin can be considered a potential therapeutic agent for treating chondrosarcomas.

Lupeol Inhibits Proliferation and Promotes Apoptosis of Ovarian Cancer Cells by Inactivating Phosphoinositide-3-Kinase/Protein Kinase B/ Mammalian Target of Rapamycin Pathway

2020 ◽  
Vol 19 (2) ◽  
pp. 206-210
Author(s):  
Feng Chen ◽  
Bei Zhang
Keyword(s):  
Cell Cycle ◽  
Ovarian Cancer ◽  
Protein Kinase ◽  
Cell Viability ◽  
Cancer Cells ◽  
Protein Kinase B ◽  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin ◽  
Ovarian Cancer Cells ◽  
Phosphoinositide 3 Kinase

Lupeol exhibits multiple pharmacological activities including, anticancerous, anti-inflammatory, and antioxidant. The aim of this study was to explore the anticancerous activity of lupeol on ovarian cancer cells and examine its mechanism of action. To this end, increasing concentrations of lupeol on cell viability, cell cycle, and apoptosis in Caov-3 cells were evaluated. Lupeol inhibited cell viability, induced G1 phase arrest in cell cycle, increased cell apoptosis, and inhibited the ratio of phospho-Akt/protein kinase B and phospho-mammalian target of rapamycin/mammalian target of rapamycin. In conclusion, these data suggest that lupeol may play a therapeutic role in ovarian cancer.

scholarly journals Rag proteins regulate amino-acid-induced mTORC1 signalling

2009 ◽  
Vol 37 (1) ◽  
pp. 289-290 ◽  
Author(s):  
Yasemin Sancak ◽  
David M. Sabatini
Keyword(s):  
Amino Acid ◽  
Protein Kinase ◽  
Cell Growth ◽  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin ◽  
Master Regulator ◽  
Growth And Survival ◽  
Field Identification ◽  
Rag Proteins ◽  
Cell Growth And Survival

The serum- and nutrient-sensitive protein kinase mTOR (mammalian target of rapamycin) is a master regulator of cell growth and survival. The mechanisms through which nutrients regulate mTOR have been one of the major unanswered questions in the mTOR field. Identification of the Rag (Ras-related GTPase) family of GTPases as mediators of amino acid signalling to mTOR is an important step towards our understanding of this mechanism.

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

The kinase triad, AMPK, mTORC1 and ULK1, maintains energy and nutrient homoeostasis

2013 ◽  
Vol 41 (4) ◽  
pp. 939-943 ◽  
Author(s):  
Elaine A. Dunlop ◽  
Andrew R. Tee
Keyword(s):  
Amino Acid ◽  
Cell Growth ◽  
Protein Kinases ◽  
Mammalian Target Of Rapamycin ◽  
Nutrient Status ◽  
Protein Translation ◽  
Cellular Growth ◽  
Target Of Rapamycin ◽  
Amp Activated Protein Kinase ◽  
Rate Limiting

In order for cells to divide in a proficient manner, they must first double their biomass, which is considered to be the main rate-limiting phase of cell proliferation. Cell growth requires an abundance of energy and biosynthetic precursors such as lipids and amino acids. Consequently, the energy and nutrient status of the cell is acutely monitored and carefully maintained. mTORC1 [mammalian (or mechanistic) target of rapamycin complex 1] is often considered to be the master regulator of cell growth that enhances cellular biomass through up-regulation of protein translation. In order for cells to control cellular homoeostasis during growth, there is close signalling interplay between mTORC1 and two other protein kinases, AMPK (AMP-activated protein kinase) and ULK1 (Unc-51-like kinase 1). This kinase triad collectively senses the energy and nutrient status of the cell and appropriately dictates whether the cell will actively favour energy- and amino-acid-consuming anabolic processes such as cellular growth, or energy- and amino-acid-generating catabolic processes such as autophagy. The present review discusses important feedback mechanisms between these three homoeostatic protein kinases that orchestrate cell growth and autophagy, with a particular focus on the mTORC1 component raptor (regulatory associated protein of mammalian target of rapamycin), as well as the autophagy-initiating kinase ULK1.

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