Regulation of mTOR Complex 1 (mTORC1) by Raptor Ser863 and Multisite Phosphorylation

Foster, Kathryn G.; Acosta-Jaquez, Hugo A.; Roméo, Yves; Ekim, Bilgen; Soliman, Ghada A.; Carrière, Audrey; Roux, Philippe P.; Ballif, Bryan A.; Fingar, Diance C.

doi:10.1074/jbc.m109.029637

Cited by 168 publications

(179 citation statements)

References 74 publications

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“…However, despite the plethora of mTOR and Raptor phosphorylation sites that have been identified to date, none appear to regulate complex formation (44)(45)(46)(47)(48), and our own attempts at identifying phosphorylation sites critical for mTORC1 formation have not yielded conclusive results. Whether complex formation is due to phosphorylation sites on mTOR or Raptor that are as yet unidentified, or if a combination of phosphorylation sites on either molecule are involved, remains to be determined.…”

Section: Discussionmentioning

confidence: 87%

Control of mTORC1 signaling by the Opitz syndrome protein MID1

Liu

Knutzen

Krauß

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Mutations in the MID1 gene are causally linked to X-linked Opitz BBB/G syndrome (OS), a congenital disorder that primarily affects the formation of diverse ventral midline structures. The MID1 protein has been shown to function as an E3 ligase targeting the catalytic subunit of protein phosphatase 2A (PP2A-C) for ubiquitinmediated degradation. However, the molecular pathways downstream of the MID1/PP2A axis that are dysregulated in OS and that translate dysfunctional MID1 and elevated levels of PP2A-C into the OS phenotype are poorly understood. Here, we show that perturbations in MID1/PP2A affect mTORC1 signaling. Increased PP2A levels, resulting from proteasome inhibition or depletion of MID1, lead to disruption of the mTOR/Raptor complex and downregulated mTORC1 signaling. Congruously, cells derived from OS patients that carry MID1 mutations exhibit decreased mTORC1 formation, S6K1 phosphorylation, cell size, and cap-dependent translation, all of which is rescued by expression of wild-type MID1 or an activated mTOR allele. Our findings define mTORC1 signaling as a downstream pathway regulated by the MID1/PP2A axis, suggesting that mTORC1 plays a key role in OS pathogenesis.ubiquitin ligase | proteasome-mediated degradation M utations in the MID1 gene are causally linked to X-linked Opitz BBB/G syndrome (OS), a congenital disorder that primarily affects the formation of ventral midline structures. The clinical manifestations of Opitz syndrome are characterized by a diverse spectrum of symptoms, including hypertelorism and hypospadias, cleft lip/palate, dysphagia, heart defects, and mental retardation (1).The MID1 protein is a member of the RBCC/TRIM family, which contains a conserved module of the RING domain, followed by B-boxes and a coiled-coil domain (2). MID1 also contains fibronectin type III and B30.2/SPRY domains. The RING domain has been well characterized in ubiquitin-mediated protein degradation, whereas the other domains mediate proteinprotein interactions (3-6). Opitz syndrome-derived mutations in MID1 have been identified throughout the protein and show several functional consequences such as compromised association with microtubules and/or transport along microtubules (4, 7-9). In addition to its microtubule-binding function, MID1 also functions as an E3 ligase that targets the microtubule-associated pool of the catalytic subunit of protein phosphatase 2A (PP2A-C) for ubiquitin-mediated degradation through an interaction with the protein α4 (3). Perturbation of the E3 ligase function of MID1 in OS cells leads to the accumulation of PP2A-C and the dramatic dephosphorylation of microtubule-associated proteins, which is postulated to contribute to OS pathogenesis (3).Signaling from the mammalian target of rapamycin (mTOR) controls diverse cellular processes such as growth, autophagy, stress responses, cytoskeletal reorganization, cell motility, metabolism, and aging (10-12). mTORC1 consists of mTOR and the interacting proteins, Raptor, and mLST8. In particular, Raptor plays an essential scaffolding...

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Section: Discussionmentioning

confidence: 87%

Control of mTORC1 signaling by the Opitz syndrome protein MID1

Liu

Knutzen

Krauß

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…Insulin and nutrients (e.g., amino acids and glucose) weaken the mTOR-raptor interaction via an unknown mechanism(s), which correlates with active mTORC1 signaling (1,21,38,39). Raptor possesses dual functions in mTORC1 regulation, as it both suppresses and promotes mTORC1 signaling via a strong, inhibitory interaction and a weaker, required interaction, respectively (38).…”

Section: Discussionmentioning

confidence: 99%

“…Insulin/ PI3K signaling leads to Akt-and mTOR-mediated phosphorylation of PRAS40, which relieves the inhibitory effect of PRAS40 on mTORC1 (20,50,57,67,69). Insulin/PI3K signaling also increases mTOR S1261 and mTOR-mediated raptor S863 phosphorylation, events that promote mTORC1 function (1,21,71). In addition to phosphorylating PRAS40 and raptor, activated mTOR also phosphorylates deptor, leading to its degradation and thus relieving its mTOR-inhibitory action (52).…”

mentioning

confidence: 99%

mTOR Kinase Domain Phosphorylation Promotes mTORC1 Signaling, Cell Growth, and Cell Cycle Progression

Ekim

Magnuson

Acosta-Jaquez

et al. 2011

Molecular and Cellular Biology

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109

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The mammalian target of rapamycin complex 1 (mTORC1) functions as an environmental sensor to promote critical cellular processes such as protein synthesis, cell growth, and cell proliferation in response to growth factors and nutrients. While diverse stimuli regulate mTORC1 signaling, the direct molecular mechanisms by which mTORC1 senses and responds to these signals remain poorly defined. Here we investigated the role of mTOR phosphorylation in mTORC1 function. By employing mass spectrometry and phospho-specific antibodies, we demonstrated novel phosphorylation on S2159 and T2164 within the mTOR kinase domain. Mutational analysis of these phosphorylation sites indicates that dual S2159/T2164 phosphorylation cooperatively promotes mTORC1 signaling to S6K1 and 4EBP1. Mechanistically, S2159/T2164 phosphorylation modulates the mTOR-raptor and raptor-PRAS40 interactions and augments mTORC1-associated mTOR S2481 autophosphorylation. Moreover, mTOR S2159/T2164 phosphorylation promotes cell growth and cell cycle progression. We propose a model whereby mTOR kinase domain phosphorylation modulates the interaction of mTOR with regulatory partner proteins and augments intrinsic mTORC1 kinase activity to promote biochemical signaling, cell growth, and cell cycle progression.

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“…mTORC1 activation by diverse stimuli (e.g. the PI3K/TSC/Rheb pathway, amino acids, EGF, energy sufficiency) promotes the rapamycin-sensitive and thus mTORmediated phosphorylation of raptor Ser 863 , which promotes mTORC1 activity (32,83 ) to inhibit mTORC1 signaling, which activates a metabolic checkpoint to cause cell cycle arrest (56,85). Most recently, the mitotic kinase Cdc2 was reported to phosphorylate raptor Ser 696 and Thr 706 , with unknown functional significance (86).…”

Section: Direct Molecular Mechanisms Of Mtorc Regulationmentioning

confidence: 99%

“…The avidity of interactions within mTORC1 has emerged as an important point of mTORC1 regulation. mTORC1 activation leads to modest weakening of the mTOR-raptor, mTOR-deptor, and raptor-PRAS40 interactions (20,29,30,32,76). Although quite controversial, Rheb-GTP reportedly interacts with FKBP38, an endogenous mTORC1 inhibitor that binds to the mTOR FRB domain, thereby blunting the inhibitory FKBP38-mTOR interaction (3,48,77).…”

Section: Direct Molecular Mechanisms Of Mtorc Regulationmentioning

confidence: 99%

Mammalian Target of Rapamycin (mTOR): Conducting the Cellular Signaling Symphony

Foster

Fingar

2010

Journal of Biological Chemistry

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475

458

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The mammalian target of rapamycin (mTOR) protein kinase responds to diverse environmental cues to control a plethora of cellular processes. mTOR forms the catalytic core of at least two distinct signaling complexes known as mTOR complexes 1 and 2. Differing sensitivities to the mTOR inhibitor rapamycin, unique partner proteins, distinct substrates, and unique cellular functions distinguish the complexes. Here, we review recent progress in our understanding of the regulation and function of mTOR signaling networks in cellular physiology.

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Regulation of mTOR Complex 1 (mTORC1) by Raptor Ser863 and Multisite Phosphorylation

Cited by 168 publications

References 74 publications

Control of mTORC1 signaling by the Opitz syndrome protein MID1

Control of mTORC1 signaling by the Opitz syndrome protein MID1

mTOR Kinase Domain Phosphorylation Promotes mTORC1 Signaling, Cell Growth, and Cell Cycle Progression

Mammalian Target of Rapamycin (mTOR): Conducting the Cellular Signaling Symphony

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