This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Edinger, A. L. Articles by Abraham, R. T. Search for Related Content PubMed PubMed Citation Articles by Edinger, A. L. Articles by Abraham, R. T.

Differential Effects of Rapamycin on Mammalian Target of Rapamycin Signaling Functions in Mammalian Cells

¹ Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, Pennsylvania;
² Departments of Pediatrics and Pharmacology and Cancer Biology, Duke University, Durham, North Carolina; and
³ Program in Signal Transduction Research, The Burnham Institute, La Jolla, California

Rapamycin and its analogues have shown promising anticancer activities in preclinical and clinical studies. However, the mechanism whereby rapamycin inhibits signaling through the mammalian target of rapamycin (mTOR) remains poorly understood. Here, we show that the FKBP12/rapamycin complex is an essentially irreversible inhibitor of mTOR kinase activity in vitro. However, we observe no suppression of mTOR catalytic activity after immunoprecipitation from rapamycin-treated cells. These results suggest either that rapamycin acts as a reversible kinase inhibitor in intact cells or that the cellular effects of rapamycin are not mediated through global suppression in mTOR kinase activity. To better understand the cellular pharmacology of rapamycin, we compared the individual and combined effects of rapamycin and kinase-inactive mTOR expression on a panel of mTOR-dependent cellular responses. These studies identified glycolytic activity, amino acid transporter trafficking, and Akt kinase activity as novel, mTOR-modulated functions in mammalian cells. Whereas kinase-inactive mTOR did not enhance the decreases in cell size and glycolysis induced by rapamycin, expression of this mTOR mutant significantly enhanced the inhibitory effects of rapamycin on cell proliferation, 4EBP1 phosphorylation, and Akt activity. Unexpectedly, amino acid transporter trafficking was perturbed by kinase-inactive mTOR but not by rapamycin, indicating that this process is rapamycin insensitive. These results indicate that rapamycin exerts variable inhibitory actions on mTOR signaling functions and suggest that direct inhibitors of the mTOR kinase domain will display substantially broader anticancer activities than rapamycin.

This article has been cited by other articles:

				X. Jiang, H. Kenerson, L. Aicher, R. Miyaoka, J. Eary, J. Bissler, and R. S. Yeung The Tuberous Sclerosis Complex Regulates Trafficking of Glucose Transporters and Glucose Uptake Am. J. Pathol., June 1, 2008; 172(6): 1748 - 1756. [Abstract] [Full Text] [PDF]

				L. H. Wei, H. Su, I. J. Hildebrandt, M. E. Phelps, J. Czernin, and W. A. Weber Changes in Tumor Metabolism as Readout for Mammalian Target of Rapamycin Kinase Inhibition by Rapamycin in Glioblastoma Clin. Cancer Res., June 1, 2008; 14(11): 3416 - 3426. [Abstract] [Full Text] [PDF]

				J. Dal Col, P. Zancai, L. Terrin, M. Guidoboni, M. Ponzoni, A. Pavan, M. Spina, S. Bergamin, S. Rizzo, U. Tirelli, et al. Distinct functional significance of Akt and mTOR constitutive activation in mantle cell lymphoma Blood, May 15, 2008; 111(10): 5142 - 5151. [Abstract] [Full Text] [PDF]

				D. Barbone, T.-M. Yang, J. R. Morgan, G. Gaudino, and V. C. Broaddus Mammalian Target of Rapamycin Contributes to the Acquired Apoptotic Resistance of Human Mesothelioma Multicellular Spheroids J. Biol. Chem., May 9, 2008; 283(19): 13021 - 13030. [Abstract] [Full Text] [PDF]

				X. Yang, C. Yang, A. Farberman, T. C. Rideout, C. F. M. de Lange, J. France, and M. Z. Fan The mammalian target of rapamycin-signaling pathway in regulating metabolism and growth J Anim Sci, April 1, 2008; 86(14_suppl): E36 - E50. [Abstract] [Full Text] [PDF]

				P. Amornphimoltham, V. Patel, K. Leelahavanichkul, R. T. Abraham, and J. S. Gutkind A Retroinhibition Approach Reveals a Tumor Cell-Autonomous Response to Rapamycin in Head and Neck Cancer Cancer Res., February 15, 2008; 68(4): 1144 - 1153. [Abstract] [Full Text] [PDF]

				Y. Jossin and A. M. Goffinet Reelin Signals through Phosphatidylinositol 3-Kinase and Akt To Control Cortical Development and through mTor To Regulate Dendritic Growth Mol. Cell. Biol., October 15, 2007; 27(20): 7113 - 7124. [Abstract] [Full Text] [PDF]

				B. C. Fuchs, R. E. Finger, M. C. Onan, and B. P. Bode ASCT2 silencing regulates mammalian target-of-rapamycin growth and survival signaling in human hepatoma cells Am J Physiol Cell Physiol, July 1, 2007; 293(1): C55 - C63. [Abstract] [Full Text] [PDF]

				T. L. Phung, G. Eyiah-Mensah, R. K. O'Donnell, R. Bieniek, S. Shechter, K. Walsh, C. Kuperwasser, and L. E. Benjamin Endothelial Akt Signaling Is Rate-Limiting for Rapamycin Inhibition of Mouse Mammary Tumor Progression Cancer Res., June 1, 2007; 67(11): 5070 - 5075. [Abstract] [Full Text] [PDF]

				R. T. Abraham and J. J. Gibbons The Mammalian Target of Rapamycin Signaling Pathway: Twists and Turns in the Road to Cancer Therapy Clin. Cancer Res., June 1, 2007; 13(11): 3109 - 3114. [Abstract] [Full Text] [PDF]

				S. Corbacioglu, M. Kilic, M.-A. Westhoff, D. Reinhardt, S. Fulda, and K.-M. Debatin Newly identified c-KIT receptor tyrosine kinase ITD in childhood AML induces ligand-independent growth and is responsive to a synergistic effect of imatinib and rapamycin Blood, November 15, 2006; 108(10): 3504 - 3513. [Abstract] [Full Text] [PDF]

				D. C. Birle and D. W. Hedley Signaling interactions of rapamycin combined with erlotinib in cervical carcinoma xenografts. Mol. Cancer Ther., October 1, 2006; 5(10): 2494 - 2502. [Abstract] [Full Text] [PDF]

				K. W.L. Yee, Z. Zeng, M. Konopleva, S. Verstovsek, F. Ravandi, A. Ferrajoli, D. Thomas, W. Wierda, E. Apostolidou, M. Albitar, et al. Phase I/II Study of the Mammalian Target of Rapamycin Inhibitor Everolimus (RAD001) in Patients with Relapsed or Refractory Hematologic Malignancies Clin. Cancer Res., September 1, 2006; 12(17): 5165 - 5173. [Abstract] [Full Text] [PDF]

				S. Di Paolo, A. Teutonico, D. Leogrande, C. Capobianco, and P. F. Schena Chronic Inhibition of Mammalian Target of Rapamycin Signaling Downregulates Insulin Receptor Substrates 1 and 2 and AKT Activation: A Crossroad between Cancer and Diabetes? J. Am. Soc. Nephrol., August 1, 2006; 17(8): 2236 - 2244. [Abstract] [Full Text] [PDF]

				X. Jiang and R. S. Yeung Regulation of Microtubule-Dependent Protein Transport by the TSC2/Mammalian Target of Rapamycin Pathway. Cancer Res., May 15, 2006; 66(10): 5258 - 5269. [Abstract] [Full Text] [PDF]

				D. J. VanderWeele and C. M. Rudin Mammalian Target of Rapamycin Promotes Vincristine Resistance through Multiple Mechanisms Independent of Maintained Glycolytic Rate Mol. Cancer Res., November 1, 2005; 3(11): 635 - 644. [Abstract] [Full Text] [PDF]

				G. G. Chiang and R. T. Abraham Phosphorylation of Mammalian Target of Rapamycin (mTOR) at Ser-2448 Is Mediated by p70S6 Kinase J. Biol. Chem., July 8, 2005; 280(27): 25485 - 25490. [Abstract] [Full Text] [PDF]

				M. Liu, A. Howes, J. Lesperance, W. B. Stallcup, C. A. Hauser, K. Kadoya, R. G. Oshima, and R. T. Abraham Antitumor Activity of Rapamycin in a Transgenic Mouse Model of ErbB2-Dependent Human Breast Cancer Cancer Res., June 15, 2005; 65(12): 5325 - 5336. [Abstract] [Full Text] [PDF]

				H. Takeuchi, Y. Kondo, K. Fujiwara, T. Kanzawa, H. Aoki, G. B. Mills, and S. Kondo Synergistic Augmentation of Rapamycin-Induced Autophagy in Malignant Glioma Cells by Phosphatidylinositol 3-Kinase/Protein Kinase B Inhibitors Cancer Res., April 15, 2005; 65(8): 3336 - 3346. [Abstract] [Full Text] [PDF]

				X. Wang, A. Beugnet, M. Murakami, S. Yamanaka, and C. G. Proud Distinct Signaling Events Downstream of mTOR Cooperate To Mediate the Effects of Amino Acids and Insulin on Initiation Factor 4E-Binding Proteins Mol. Cell. Biol., April 1, 2005; 25(7): 2558 - 2572. [Abstract] [Full Text] [PDF]

				D. D. Sarbassov, D. A. Guertin, S. M. Ali, and D. M. Sabatini Phosphorylation and Regulation of Akt/PKB by the Rictor-mTOR Complex Science, February 18, 2005; 307(5712): 1098 - 1101. [Abstract] [Full Text] [PDF]

				O. Vallon Chlamydomonas Immunophilins and Parvulins: Survey and Critical Assessment of Gene Models Eukaryot. Cell, February 1, 2005; 4(2): 230 - 241. [Full Text] [PDF]

				R. Weisman, I. Roitburg, T. Nahari, and M. Kupiec Regulation of Leucine Uptake by tor1+ in Schizosaccharomyces pombe Is Sensitive to Rapamycin Genetics, February 1, 2005; 169(2): 539 - 550. [Abstract] [Full Text] [PDF]

				I. Mothe-Satney, N. Gautier, C. Hinault, J. C. Lawrence Jr., and E. Van Obberghen In Rat Hepatocytes Glucagon Increases Mammalian Target of Rapamycin Phosphorylation on Serine 2448 but Antagonizes the Phosphorylation of Its Downstream Targets Induced by Insulin and Amino Acids J. Biol. Chem., October 8, 2004; 279(41): 42628 - 42637. [Abstract] [Full Text] [PDF]