scholarly journals Ku-0063794 is a specific inhibitor of the mammalian target of rapamycin (mTOR)

2009 ◽  
Vol 421 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Juan M. García-Martínez ◽  
Jennifer Moran ◽  
Rosemary G. Clarke ◽  
Alex Gray ◽  
Sabina C. Cosulich ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cell Growth ◽  
Mammalian Target Of Rapamycin ◽  
Specific Inhibitor ◽  
Initiation Factor ◽  
Target Of Rapamycin ◽  
S6 Kinase ◽  
Class 1 ◽  
Hydrophobic Motif ◽  
Ribosomal S6 Kinase

mTOR (mammalian target of rapamycin) stimulates cell growth by phosphorylating and promoting activation of AGC (protein kinase A/protein kinase G/protein kinase C) family kinases such as Akt (protein kinase B), S6K (p70 ribosomal S6 kinase) and SGK (serum and glucocorticoid protein kinase). mTORC1 (mTOR complex-1) phosphorylates the hydrophobic motif of S6K, whereas mTORC2 phosphorylates the hydrophobic motif of Akt and SGK. In the present paper we describe the small molecule Ku-0063794, which inhibits both mTORC1 and mTORC2 with an IC50 of ∼10 nM, but does not suppress the activity of 76 other protein kinases or seven lipid kinases, including Class 1 PI3Ks (phosphoinositide 3-kinases) at 1000-fold higher concentrations. Ku-0063794 is cell permeant, suppresses activation and hydrophobic motif phosphorylation of Akt, S6K and SGK, but not RSK (ribosomal S6 kinase), an AGC kinase not regulated by mTOR. Ku-0063794 also inhibited phosphorylation of the T-loop Thr308 residue of Akt phosphorylated by PDK1 (3-phosphoinositide-dependent protein kinase-1). We interpret this as implying phosphorylation of Ser473 promotes phosphorylation of Thr308 and/or induces a conformational change that protects Thr308 from dephosphorylation. In contrast, Ku-0063794 does not affect Thr308 phosphorylation in fibroblasts lacking essential mTORC2 subunits, suggesting that signalling processes have adapted to enable Thr308 phosphorylation to occur in the absence of Ser473 phosphorylation. We found that Ku-0063794 induced a much greater dephosphorylation of the mTORC1 substrate 4E-BP1 (eukaryotic initiation factor 4E-binding protein 1) than rapamycin, even in mTORC2-deficient cells, suggesting a form of mTOR distinct from mTORC1, or mTORC2 phosphorylates 4E-BP1. Ku-0063794 also suppressed cell growth and induced a G1-cell-cycle arrest. Our results indicate that Ku-0063794 will be useful in delineating the physiological roles of mTOR and may have utility in treatment of cancers in which this pathway is inappropriately activated.

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.

Activation of the cardiac mTOR/p70S6K pathway by leucine requires PDK1 and correlates with PRAS40 phosphorylation

2010 ◽  
Vol 298 (4) ◽  
pp. E761-E769 ◽  
Author(s):  
Cossette Sanchez Canedo ◽  
Bénédicte Demeulder ◽  
Audrey Ginion ◽  
Jose R. Bayascas ◽  
Jean-Luc Balligand ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Mammalian Target Of Rapamycin ◽  
Phosphorylation Site ◽  
Phosphatidylinositol 3 Kinase ◽  
Dependent Protein Kinase ◽  
S6 Kinase ◽  
Mtor Phosphorylation ◽  
Dependent Protein ◽  
Ribosomal S6 Kinase ◽  
Mtor Activity

Like insulin, leucine stimulates the mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (p70S6K) axis in various organs. Insulin proceeds via the canonical association of phosphatidylinositol 3-kinase (PI3K), phosphoinositide-dependent protein kinase-1 (PDK1), and protein kinase B (PKB/Akt). The signaling involved in leucine effect, although known to implicate a PI3K mechanism independent of PKB/Akt, is more poorly understood. In this study, we investigated whether PDK1 could also participate in the events leading to mTOR/p70S6K activation in response to leucine in the heart. In wild-type hearts, both leucine and insulin increased p70S6K activity whereas, in contrast to insulin, leucine was unable to activate PKB/Akt. The changes in p70S6K activity induced by insulin and leucine correlated with changes in phosphorylation of Thr389, the mTOR phosphorylation site on p70S6K, and of Ser2448 on mTOR, both related to mTOR activity. Leucine also triggered phosphorylation of the proline-rich Akt/PKB substrate of 40 kDa (PRAS40), a new pivotal mTOR regulator. In PDK1 knockout hearts, leucine, similarly to insulin, failed to induce the phosphorylation of mTOR and p70S6K, leading to the absence of p70S6K activation. The loss of leucine effect in absence of PDK1 correlated with the lack of PRAS40 phosphorylation. Moreover, the introduction in PDK1 of the L155E mutation, which is known to preserve the insulin-induced and PKB/Akt-dependent phosphorylation of mTOR/p70S6K, suppressed all leucine effects, including phosphorylation of mTOR, PRAS40, and p70S6K. We conclude that the leucine-induced stimulation of the cardiac PRAS40/mTOR/p70S6K pathway requires PDK1 in a way that differs from that of insulin.

scholarly journals BI-D1870 is a specific inhibitor of the p90 RSK (ribosomal S6 kinase) isoforms in vitro and in vivo

2006 ◽  
Vol 401 (1) ◽  
pp. 29-38 ◽  
Author(s):  
Gopal P. Sapkota ◽  
Lorna Cummings ◽  
Felicity S. Newell ◽  
Christopher Armstrong ◽  
Jennifer Bain ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinases ◽  
Phorbol Ester ◽  
Glycogen Synthase ◽  
Specific Inhibitor ◽  
Camp Response Element Binding ◽  
S6 Kinase ◽  
Ribosomal S6 Kinase

Hormones and growth factors induce the activation of a number of protein kinases that belong to the AGC subfamily, including isoforms of PKA, protein kinase B (also known as Akt), PKC, S6K p70 (ribosomal S6 kinase), RSK (p90 ribosomal S6 kinase) and MSK (mitogen- and stress-activated protein kinase), which then mediate many of the physiological processes that are regulated by these extracellular agonists. It can be difficult to assess the individual functions of each AGC kinase because their substrate specificities are similar. Here we describe the small molecule BI-D1870, which inhibits RSK1, RSK2, RSK3 and RSK4 in vitro with an IC50 of 10–30 nM, but does not signi-ficantly inhibit ten other AGC kinase members and over 40 other protein kinases tested at 100-fold higher concentrations. BI-D1870 is cell permeant and prevents the RSK-mediated phorbol ester- and EGF (epidermal growth factor)-induced phosphoryl-ation of glycogen synthase kinase-3β and LKB1 in human embry-onic kidney 293 cells and Rat-2 cells. In contrast, BI-D1870 does not affect the agonist-triggered phosphorylation of substrates for six other AGC kinases. Moreover, BI-D1870 does not suppress the phorbol ester- or EGF-induced phosphorylation of CREB (cAMP-response-element-binding protein), consistent with the genetic evidence indicating that MSK, and not RSK, isoforms mediate the mitogen-induced phosphorylation of this transcription factor.

scholarly journals Signaling by Target of Rapamycin Proteins in Cell Growth Control

2005 ◽  
Vol 69 (1) ◽  
pp. 79-100 ◽  
Author(s):  
Ken Inoki ◽  
Hongjiao Ouyang ◽  
Yong Li ◽  
Kun-Liang Guan
Keyword(s):  
Cell Growth ◽  
Molecular Mechanism ◽  
Translational Control ◽  
Mammalian Cells ◽  
Control Cell ◽  
Small Gtpase ◽  
Initiation Factor ◽  
Target Of Rapamycin ◽  
Tor Signaling ◽  
Ribosomal S6 Kinase

SUMMARY Target of rapamycin (TOR) proteins are members of the phosphatidylinositol kinase-related kinase (PIKK) family and are highly conserved from yeast to mammals. TOR proteins integrate signals from growth factors, nutrients, stress, and cellular energy levels to control cell growth. The ribosomal S6 kinase 1 (S6K) and eukaryotic initiation factor 4E binding protein 1(4EBP1) are two cellular targets of TOR kinase activity and are known to mediate TOR function in translational control in mammalian cells. However, the precise molecular mechanism of TOR regulation is not completely understood. One of the recent breakthrough studies in TOR signaling resulted in the identification of the tuberous sclerosis complex gene products, TSC1 and TSC2, as negative regulators for TOR signaling. Furthermore, the discovery that the small GTPase Rheb is a direct downstream target of TSC1-TSC2 and a positive regulator of the TOR function has significantly advanced our understanding of the molecular mechanism of TOR activation. Here we review the current understanding of the regulation of TOR signaling and discuss its function as a signaling nexus to control cell growth during normal development and tumorigenesis.

scholarly journals mRNA-Selective Translation Induced by FSH in Primary Sertoli Cells

2012 ◽  
Vol 26 (4) ◽  
pp. 669-680 ◽  
Author(s):  
Astrid Musnier ◽  
Kelly León ◽  
Julia Morales ◽  
Eric Reiter ◽  
Thomas Boulo ◽  
...  
Keyword(s):  
Sertoli Cells ◽  
Mammalian Target Of Rapamycin ◽  
Initiation Factor ◽  
Target Of Rapamycin ◽  
Target Cells ◽  
Eukaryotic Initiation Factor ◽  
S6 Kinase ◽  
P70 S6 Kinase ◽  
Eukaryotic Initiation Factor 4E ◽  
Selective Translation

Abstract FSH is a key hormonal regulator of Sertoli cell secretory activity, required to optimize sperm production. To fulfil its biological function, FSH binds a G protein-coupled receptor, the FSH-R. The FSH-R-transduced signaling network ultimately leads to the transcription or down-regulation of numerous genes. In addition, recent evidence has suggested that FSH might also regulate protein translation. However, this point has never been demonstrated conclusively yet. Here we have addressed this issue in primary rat Sertoli cells endogenously expressing physiological levels of FSH-R. We observed that, within 90 min of stimulation, FSH not only enhanced overall protein synthesis in a mammalian target of rapamycin-dependent manner but also increased the recruitment of mRNA to polysomes. m7GTP pull-down experiments revealed the functional recruitment of mammalian target of rapamycin and p70 S6 kinase to the 5′cap, further supported by the enhanced phosphorylation of one of p70 S6 kinase targets, the eukaryotic initiation factor 4B. Importantly, the scaffolding eukaryotic initiation factor 4G was also recruited, whereas eukaryotic initiation factor 4E-binding protein, the eukaryotic initiation factor 4E generic inhibitor, appeared to play a minor role in translational regulations induced by FSH, in contrast to what is generally observed in response to anabolic factors. This particular regulation of the translational machinery by FSH stimulation might support mRNA-selective translation, as shown here by quantitative RT-PCR amplification of the c-fos and vascular endothelial growth factor mRNA but not of all FSH target mRNA, in polysomal fractions. These findings add a new level of complexity to FSH biological roles in its natural target cells, which has been underappreciated so far.

scholarly journals Regulation of Ribosomal S6 Kinase 2 by Mammalian Target of Rapamycin

2002 ◽  
Vol 277 (35) ◽  
pp. 31423-31429 ◽  
Author(s):  
In-Hyun Park ◽  
Rebecca Bachmann ◽  
Haider Shirazi ◽  
Jie Chen
Keyword(s):  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin ◽  
S6 Kinase ◽  
Ribosomal S6 Kinase 2 ◽  
Ribosomal S6 Kinase
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