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Site-specific mTOR phosphorylation promotes mTORC1-mediated signaling and cell growth.

ABSTRACT: The mammalian target of rapamycin (mTOR) complex 1 (mTORC1) functions as a rapamycin-sensitive environmental sensor that promotes cellular biosynthetic processes in response to growth factors and nutrients. While diverse physiological stimuli modulate mTORC1 signaling, the direct biochemical mechanisms underlying mTORC1 regulation remain poorly defined. Indeed, while three mTOR phosphorylation sites have been reported, a functional role for site-specific mTOR phosphorylation has not been demonstrated. Here we identify a new site of mTOR phosphorylation (S1261) by tandem mass spectrometry and demonstrate that insulin-phosphatidylinositol 3-kinase signaling promotes mTOR S1261 phosphorylation in both mTORC1 and mTORC2. Here we focus on mTORC1 and show that TSC/Rheb signaling promotes mTOR S1261 phosphorylation in an amino acid-dependent, rapamycin-insensitive, and autophosphorylation-independent manner. Our data reveal a functional role for mTOR S1261 phosphorylation in mTORC1 action, as S1261 phosphorylation promotes mTORC1-mediated substrate phosphorylation (e.g., p70 ribosomal protein S6 kinase 1 [S6K1] and eukaryotic initiation factor 4E binding protein 1) and cell growth to increased cell size. Moreover, Rheb-driven mTOR S2481 autophosphorylation and S6K1 phosphorylation require S1261 phosphorylation. These data provide the first evidence that site-specific mTOR phosphorylation regulates mTORC1 function and suggest a model whereby insulin-stimulated mTOR S1261 phosphorylation promotes mTORC1 autokinase activity, substrate phosphorylation, and cell growth.

SUBMITTER: Acosta-Jaquez HA

PROVIDER: S-EPMC2715808 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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Site-specific mTOR phosphorylation promotes mTORC1-mediated signaling and cell growth.

Acosta-Jaquez Hugo A HA Keller Jennifer A JA Foster Kathryn G KG Ekim Bilgen B Soliman Ghada A GA Feener Edward P EP Ballif Bryan A BA Fingar Diane C DC

Molecular and cellular biology 20090601 15

The mammalian target of rapamycin (mTOR) complex 1 (mTORC1) functions as a rapamycin-sensitive environmental sensor that promotes cellular biosynthetic processes in response to growth factors and nutrients. While diverse physiological stimuli modulate mTORC1 signaling, the direct biochemical mechanisms underlying mTORC1 regulation remain poorly defined. Indeed, while three mTOR phosphorylation sites have been reported, a functional role for site-specific mTOR phosphorylation has not been demonst ...[more]

PMID: 19487463

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Project description:BackgroundA number of JmjC domain-containing histone demethylases have been identified and biochemically characterized in mammalian models and humans. JMJD2A is a transcriptional co-factor and enzyme that catalyzes the demethylation of histone H3 lysine 9 and 36 (H3K9 and H3K36). Here in this study, we reported the role of JMJD2A in human glioma.MethodsQuantitative real-time PCR and western blot were performed to analyzed JMJD2A expression in glioma. Log-rank was performed to plot the survival curve. JMJD2A was knocked or overexpressed with lentivirus. Cell proliferation and colony formation were performed to assess the effects of JMJD2A on glioma cell growth. Xenograft experiment was performed the evaluate the growth rate of glioma cells in vivo. The signaling pathway was analyzed with western blot and mTOR was inhibited with rapamycin.ResultsQuantitative real-time PCR and western blot experiments revealed higher expression of JMJD2A and lower levels of H3K9me3/H3K36me3 in glioma tissues than that in normal brain tissues. We showed that knockdown of JMJD2A expression attenuated the growth and colony formation in three lines of glioma cells (U251, T98G, and U87MG), whereas JMJD2A overexpression resulted in opposing effects. Furthermore, we performed in vivo xenograft experiments and our data demonstrated that JMJD2A knockdown reduced the growth of glioma T98G cells in vivo. Further mechanism study implicated that JMJD2A activated the Akt-mTOR pathway and promoted protein synthesis in glioma cells via promoting phosphoinositide-dependent kinase-1 (PDK1) expression. The activation of the Akt-mTOR pathway was also validated in human glioma tissues. Finally, we showed that inhibition of mTOR with rapamycin blocked the effects of JMJD2A on protein synthesis, cell proliferation and colony formation of glioma cells.ConclusionsThese findings demonstrated that JMJD2A regulated glioma growth and implicated that JMJD2A might be a promising target for intervention.

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Site-specific mTOR phosphorylation promotes mTORC1-mediated signaling and cell growth.

Publications

Site-specific mTOR phosphorylation promotes mTORC1-mediated signaling and cell growth.

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