» Articles » PMID: 19402821

Ku-0063794 is a Specific Inhibitor of the Mammalian Target of Rapamycin (mTOR)

Overview
Journal Biochem J
Specialty Biochemistry
Date 2009 May 1
PMID 19402821
Citations 251
Authors
Affiliations
Soon will be listed here.
Abstract

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 approximately 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.

Citing Articles

LRRC8A-containing anion channels promote glioblastoma proliferation via a WNK1/mTORC2-dependent mechanism.

Fidaleo A, Bach M, Orbeta S, Abdullaev I, Martino N, Adam A bioRxiv. 2025; .

PMID: 39975357 PMC: 11838495. DOI: 10.1101/2025.02.02.636139.


Unveiling the Role of Mechanistic Target of Rapamycin Kinase (MTOR) Signaling in Cancer Progression and the Emergence of MTOR Inhibitors as Therapeutic Strategies.

Mehta D, Rajput K, Jain D, Bajaj A, Dasgupta U ACS Pharmacol Transl Sci. 2024; 7(12):3758-3779.

PMID: 39698262 PMC: 11650738. DOI: 10.1021/acsptsci.4c00530.


Effects of Target of Rapamycin and Phosphatidylinositol 3-Kinase Inhibitors and Other Autophagy-Related Supplements on Life Span in Male .

Bearden A, Stewart E, Casher C, Shaddix M, Nobles A, Mockett R Int J Mol Sci. 2024; 25(21).

PMID: 39519056 PMC: 11547029. DOI: 10.3390/ijms252111504.


Differential regulation of expression of the protein kinases DYRK1A and DYRK1B in cancer cells.

Vorwerk V, Wilms G, Babendreyer A, Becker W Sci Rep. 2024; 14(1):23926.

PMID: 39397076 PMC: 11471791. DOI: 10.1038/s41598-024-74190-1.


Using protein turnover assay to explore the drug mechanism of Carfilzomib.

Tao Y, Ding X, Jia C, Wang C, Li C Acta Biochim Biophys Sin (Shanghai). 2024; 57(2):209-222.

PMID: 38978505 PMC: 11877146. DOI: 10.3724/abbs.2024104.


References
1.
Gray A, Olsson H, Batty I, Priganica L, Downes C . Nonradioactive methods for the assay of phosphoinositide 3-kinases and phosphoinositide phosphatases and selective detection of signaling lipids in cell and tissue extracts. Anal Biochem. 2003; 313(2):234-45. DOI: 10.1016/s0003-2697(02)00607-3. View

2.
Kobayashi T, Cohen P . Activation of serum- and glucocorticoid-regulated protein kinase by agonists that activate phosphatidylinositide 3-kinase is mediated by 3-phosphoinositide-dependent protein kinase-1 (PDK1) and PDK2. Biochem J. 1999; 339 ( Pt 2):319-28. PMC: 1220160. View

3.
Yang J, Cron P, Thompson V, Good V, Hess D, Hemmings B . Molecular mechanism for the regulation of protein kinase B/Akt by hydrophobic motif phosphorylation. Mol Cell. 2002; 9(6):1227-40. DOI: 10.1016/s1097-2765(02)00550-6. View

4.
Nicklin P, Bergman P, Zhang B, Triantafellow E, Wang H, Nyfeler B . Bidirectional transport of amino acids regulates mTOR and autophagy. Cell. 2009; 136(3):521-34. PMC: 3733119. DOI: 10.1016/j.cell.2008.11.044. View

5.
Lizcano J, Deak M, Morrice N, Kieloch A, Hastie C, Dong L . Molecular basis for the substrate specificity of NIMA-related kinase-6 (NEK6). Evidence that NEK6 does not phosphorylate the hydrophobic motif of ribosomal S6 protein kinase and serum- and glucocorticoid-induced protein kinase in vivo. J Biol Chem. 2002; 277(31):27839-49. DOI: 10.1074/jbc.M202042200. View