Mammalian Target of Rapamycin Complex 1 (mTORC1) Activity Is Associated with Phosphorylation of Raptor by mTOR

Wang, Lifu; Lawrence, John C.; Sturgill, Thomas W.; Harris, Thurl E.

doi:10.1074/jbc.c109.002907

Cited by 100 publications

(95 citation statements)

References 27 publications

(35 reference statements)

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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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“…In Vitro Kinase Assay-As described (38), immune complex beads were rinsed with 1 ml of kinase buffer (50 mM NaCl, 0.1 mM EGTA, 1 mM dithiothreitol, 0.5 M microcystin LR, 10 mM Hepes, and 50 mM ␤-glycerophosphate, pH 7.4) and suspended in 60 l of kinase buffer. The kinase reactions were initiated by adding to 20 l of the suspension 5 l of kinase buffer supplemented with 0.5 mM [␥-…”

Section: Methodsmentioning

confidence: 99%

The Nuclear Import of Oncoprotein Hepatitis B X-interacting Protein Depends on Interacting with c-Fos and Phosphorylation of Both Proteins in Breast Cancer Cells

Zhang

Zhao

et al. 2013

Journal of Biological Chemistry

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Background:The oncoprotein HBXIP acts as a coactivator of transcription factor in cancer. Results: The nuclear import of HBXIP depends on interacting with c-Fos and ATM-mediated phosphorylation of HBXIP and p-ERK1/2-mediated phosphorylation of c-Fos. Conclusion: The nuclear import of HBXIP is required for collaboration with c-Fos. Significance: We provide new insights into the mechanism that HBXIP imports into the nucleus in breast cancer cells.

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“…Our current study confirms that several phosphorylated forms of Raptor notably display a nuclear localization, thus suggesting that Raptor phosphorylation might induce conformational changes in the mTORC1 complex that would allow its nuclear import to al. 17 …”

Section: Ser877mentioning

confidence: 99%