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Nakashima A, Kawanishi I, Eguchi S, Yu EH, Eguchi S, Oshiro N, Yoshino KI, Kikkawa U, Yonezawa K. Association of CAD, a multifunctional protein involved in pyrimidine synthesis, with mLST8, a component of the mTOR complexes. J Biomed Sci 2013; 20:24. [PMID: 23594158 PMCID: PMC3639846 DOI: 10.1186/1423-0127-20-24] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 04/15/2013] [Indexed: 11/10/2022] Open
Abstract
Background mTOR is a genetically conserved serine/threonine protein kinase, which controls cell growth, proliferation, and survival. A multifunctional protein CAD, catalyzing the initial three steps in de novo pyrimidine synthesis, is regulated by the phosphorylation reaction with different protein kinases, but the relationship with mTOR protein kinase has not been known. Results CAD was recovered as a binding protein with mLST8, a component of the mTOR complexes, from HEK293 cells transfected with the FLAG-mLST8 vector. Association of these two proteins was confirmed by the co-immuoprecipitaiton followed by immunoblot analysis of transfected myc-CAD and FLAG-mLST8 as well as that of the endogenous proteins in the cells. Analysis using mutant constructs suggested that CAD has more than one region for the binding with mLST8, and that mLST8 recognizes CAD and mTOR in distinct ways. The CAD enzymatic activity decreased in the cells depleted of amino acids and serum, in which the mTOR activity is suppressed. Conclusion The results obtained indicate that mLST8 bridges between CAD and mTOR, and plays a role in the signaling mechanism where CAD is regulated in the mTOR pathway through the association with mLST8.
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Fujii K, Suzuki K, Goto A, Nakahata K, Matsunaga Y, Wakasugi H, Itoh M, Yonezawa K, Abe T, Shinomura Y. Pancreatic-colonic fistula successfully treated with endoscopic transpapillary nasopancreatic drainage. Endoscopy 2011; 43 Suppl 2 UCTN:E154-5. [PMID: 21563059 DOI: 10.1055/s-0030-1256259] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
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Stoffels B, Yonezawa K, Yamamoto Y, Schäfer N, Overhaus M, Klinge U, Kalff JC, Minor T, Tolba RH. Meloxicam, a COX-2 inhibitor, ameliorates ischemia/reperfusion injury in non-heart-beating donor livers. ACTA ACUST UNITED AC 2011; 47:109-17. [PMID: 21757922 DOI: 10.1159/000329414] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 05/17/2011] [Indexed: 01/14/2023]
Abstract
BACKGROUND/AIMS Chronic organ donor shortage has led to the consideration to expand the donor pool with livers from non-heart-beating donors (NHBD), although a higher risk of graft dys- or nonfunction is associated with these livers. We examined the effects of selective cyclooxygenase-2 (COX-2) inhibition on hepatic warm ischemia (WI) reperfusion (I/R) injury of NHBD. METHODS Male Wistar rats were used as donors and meloxicam (5 mg/kg body weight) was administered into the preservation solution. Livers were excised after 60 min of WI in situ, flushed and preserved for 24 h at 4°C. Reperfusion was carried out in vitro at a constant flow for 45 min. During reperfusion (5, 15, 30 and 45 min), enzyme release of alanine aminotransferase and glutamate lactate dehydrogenase were measured as well as portal venous pressure, bile production and oxygen consumption. The production of malondialdehyde was quantified and TUNEL staining was performed. Quantitative PCR analyzed COX-2 mRNA. COX-2 immunohistochemistry and TxB(2) detection completed the measurements. RESULTS Meloxicam treatment led to better functional recovery concerning liver enzyme release, vascular resistance and metabolic activity over time in all animals. Oxidative stress and apoptosis were considerably reduced. CONCLUSION Cold storage using meloxicam resulted in significantly better integrity and function of livers retrieved from NHBD. Selective COX-2 inhibition is a new therapeutic approach achieving improved preservation of grafts from NHBD.
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Matunaga Y, Goto A, Fujii K, Nakamura H, Itoh M, Wakasugi H, Suzuki K, Yonezawa K, Abe T, Shinomura Y. Desquamative esophagitis due to pemphigus vulgaris. Endoscopy 2011; 42 Suppl 2:E285. [PMID: 21086254 DOI: 10.1055/s-0030-1255569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
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Yonezawa K, Horie O, Yoshioka A, Matsuki S, Tenjin T, Tsukamura Y, Yoneda M, Shibata K, Koike Y, Nomura T, Yokoyama M, Urahama N, Ito M. Association between the neutrophil myeloperoxidase index and subsets of bacterial infections. Int J Lab Hematol 2011; 32:598-605. [PMID: 20201994 DOI: 10.1111/j.1751-553x.2010.01227.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The mean myeloperoxidase index (MPXI) is calculated during the routine complete blood count performed using the autoanalyzer ADVIA120/2120. The pattern of changes in the neutrophil myeloperoxidase levels in patients with specific infectious diseases was analyzed by assessing the MPXI levels. In patients with bacterial sepsis, identified by positive blood-culture tests, with (n = 29) and without (n = 51) systemic inflammatory response syndrome, the mean MPXI significantly reduced to -3.18 and -2.06, respectively. In contrast, among patients with nontuberculous nonseptic bacterial infections (n = 40), the mean MPXI significantly elevated to 5.51, while tuberculosis patients (n = 37) and patients with viral infection (n = 60) showed an unchanged MPXI (mean values, -0.46 and -1.06, respectively). Among the parameters of inflammation, only the C-reactive protein values showed a weak correlation with the MPXI levels. [Conclusion] These results indicate that MPXI is correlated with some specific infectious states, i.e. MPXI is low in bacterial sepsis and high in nontuberculous nonseptic bacterial infections. MPXI appears to be an independent and useful biomarker for the diagnosis and follow-up of infectious diseases, especially when the MPXI values are obtained at regular intervals during the disease courses of the patients.
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Qi S, Mizuno M, Yonezawa K, Nawa H, Takei N. Activation of mammalian target of rapamycin signaling in spatial learning. Neurosci Res 2010; 68:88-93. [DOI: 10.1016/j.neures.2010.06.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 06/14/2010] [Accepted: 06/14/2010] [Indexed: 12/20/2022]
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Kaizuka T, Hara T, Oshiro N, Kikkawa U, Yonezawa K, Takehana K, Iemura SI, Natsume T, Mizushima N. Tti1 and Tel2 are critical factors in mammalian target of rapamycin complex assembly. J Biol Chem 2010; 285:20109-16. [PMID: 20427287 DOI: 10.1074/jbc.m110.121699] [Citation(s) in RCA: 187] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mammalian target of rapamycin (mTOR) is a member of the phosphatidylinositol 3-kinase-related kinase (PIKK) family and is a major regulator of translation, cell growth, and autophagy. mTOR exists in two distinct complexes, mTORC1 and mTORC2, that differ in their subunit composition. In this study, we identified KIAA0406 as a novel mTOR-interacting protein. Because it has sequence homology with Schizosaccharomyces pombe Tti1, we named it mammalian Tti1. Tti1 constitutively interacts with mTOR in both mTORC1 and mTORC2. Knockdown of Tti1 suppresses phosphorylation of both mTORC1 substrates (S6K1 and 4E-BP1) and an mTORC2 substrate (Akt) and also induces autophagy. S. pombe Tti1 binds to Tel2, a protein whose mammalian homolog was recently reported to regulate the stability of PIKKs. We confirmed that Tti1 binds to Tel2 also in mammalian cells, and Tti1 interacts with and stabilizes all six members of the PIKK family of proteins (mTOR, ATM, ATR, DNA-PKcs, SMG-1, and TRRAP). Furthermore, using immunoprecipitation and size-exclusion chromatography analyses, we found that knockdown of either Tti1 or Tel2 causes disassembly of mTORC1 and mTORC2. These results indicate that Tti1 and Tel2 are important not only for mTOR stability but also for assembly of the mTOR complexes to maintain their activities.
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Tagami T, Tosa R, Hirama H, Yonezawa K, Omura M, Akiyama G, Masuno T, Yamamoto Y, Kushimoto S, Yokota H. A prospective pilot study of the effect of neutrophil elastase on the pulmonary vascular permeability in patients with pneumonia. Crit Care 2010. [PMCID: PMC2934490 DOI: 10.1186/cc8411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Hasegawa Y, Goto A, Nishimura S, Sukawa Y, Fujii K, Suzuki K, Yonezawa K, Abe T, Shinomura Y, Yoshida Y. Cytomegalovirus gastritis after treatment with rituximab. Endoscopy 2009; 41 Suppl 2:E199. [PMID: 19637127 DOI: 10.1055/s-0029-1214855] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
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Sukawa Y, Goto A, Okuda H, Suzuki K, Hasegawa Y, Yonezawa K, Abe T, Shinomura Y. Unexplained melena associated with a history of endovascular stent grafting of abdominal aortic aneurysms: aortoduodenal fistula. Endoscopy 2009; 41 Suppl 2:E84. [PMID: 19370524 DOI: 10.1055/s-0029-1214484] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
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Tagami T, Kushimoto S, Masuno T, Tosa R, Yonezawa K, Hirama H, Imazu Y, Matsuda K, Yamamoto Y, Kawai M, Yokota H. Validation of the extravascular lung water by single transpulmonary thermodilution in the clinical setting. Crit Care 2009. [PMCID: PMC4084112 DOI: 10.1186/cc7390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Song SW, Tolba RH, Yonezawa K, Manekeller S, Minor T. Exogenous superoxide dismutase prevents peroxynitrite-induced apoptosis in non-heart-beating donor livers. Eur Surg Res 2008; 41:353-61. [PMID: 18852490 DOI: 10.1159/000162294] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Accepted: 05/13/2008] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To investigate the role of oxygen free radicals in the induction of apoptosis in non-heart-beating donor (NHBD) livers, and if superoxide dismutase (SOD) ameliorates these alterations. METHODS Rat livers were perfused via the portal vein with histidine/tryptophan/alpha-ketoglutarate solution from heart-beating donors (HBD) or 60-min warm ischemia from NHBD, with or without the addition of SOD. After 24 h, cold storage livers were evaluated by isolated reperfusion. RESULTS NHBD showed significantly higher enzyme leakage and elevated portal venous pressure (PVP) versus HBD. Bile and total adenine nucleotides (TAN) were significantly decreased. Apoptosis was prominent in sinusoidal lining cells, coupled with strong nitrotyrosine staining (NTR). The concentrations of nitric oxide and lipoperoxides were largely increased. SOD medication reduced hepatic enzyme release by 30% and lipoperoxides by nearly 50%. Apoptosis and NTR were significantly decreased, and PVP was strikingly reduced to normal values. A 3-fold enhancement in bile production and 1.5-fold increase in TAN of the liver tissue were also observed. CONCLUSION NHBD livers are prone to severe reoxygenation injury promoted by oxygen free radicals, massive nitrite oxide production and peroxynitrite-induced apoptosis within the sinusoids. Antioxidant medication with SOD should be considered as a useful means of preserving NHBD livers.
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Komuro K, Nakanishi Y, Iwashiro N, Ohara M, Ishizaka M, Takeda S, Kaneko R, Ogasawara Y, Yonezawa K. Examination of sentinel lymph node in breast cancer by the combination of computed tomography lymphography, blue dye method and fluorescence navigation. EJC Suppl 2008. [DOI: 10.1016/s1359-6349(08)70492-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Zhou J, Hara K, Inoue M, Hamada S, Yasuda H, Moriyama H, Endo H, Hirota K, Yonezawa K, Nagata M, Yokono K. Regulation of hypoxia-inducible factor 1 by glucose availability under hypoxic conditions. THE KOBE JOURNAL OF MEDICAL SCIENCES 2008; 53:283-296. [PMID: 18762723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Hypoxia-inducible transcription factor 1 (HIF-1), consisting of HIF-1 alpha and HIF-1 beta subunits, regulates the expression of a variety of genes involved in diverse adaptive processes in response to hypoxia. While oxygen availability regulates HIF-1 alpha by proteolytic degradation, some growth factors regulate HIF-1 alpha by protein synthesis in part through mammalian target of rapamycin complex 1 (TORC1) pathway. We herein report the role of nutrient availability on the regulation of HIF-1. A reduced availability of glucose, not amino acids, results in a decrease of the expression of HIF1-dependent genes and HIF-1 alpha protein in response to hypoxia. HIF-1 alpha mRNA expression was not significantly suppressed and DMOG, an inhibitor for proteasomal degradation of HIF-1 alpha, did not induce HIF-1 alpha protein expression under hypoxia combined with glucose depletion. In comparison to the effect in the presence of glucose, glucose depletion under hypoxia induced a much stronger activation of the AMP-dependent kinase pathway and phosphorylation of eIF2 alpha, and nearly complete inhibition of the TORC1 pathway. These findings imply that the reduced availability of glucose under hypoxia downregulates HIF-1 in part through the inhibition of HIF-1 alpha mRNA translation, which is occasionally observed in pathophysiological situations such as ischemic diseases.
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Eguchi S, Oshiro N, Miyamoto T, Yoshino KI, Okamoto S, Ono T, Kikkawa U, Yonezawa K. AMP-activated protein kinase phosphorylates glutamine : fructose-6-phosphate amidotransferase 1 at Ser243 to modulate its enzymatic activity. Genes Cells 2008; 14:179-89. [PMID: 19170765 DOI: 10.1111/j.1365-2443.2008.01260.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Glutamine : fructose-6-phosphate amidotransferase 1 (GFAT1) was identified as a protein phosphorylated in glucose-deprived cells by immunoprecipitation using the anti-phospho Akt substrates (PAS) antibody, which recognizes the phosphorylation motif site by AMP-activated protein kinase (AMPK), followed by mass fingerprinting analysis. Glucose depletion-induced phosphorylation of endogenous GFAT was potentiated by 2-deoxyglucose (2-DG), an AMPK activator, and the 2-DG-stimulated phosphorylation of FLAG-tagged GFAT1 in transfected cells was suppressed by Compound C, an AMPK inhibitor. The 2-DG induced phosphorylation of GFAT1 was attenuated by the introduction of the kinase-negative mutant of AMPK, and the phosphorylation was observed in the cells expressing the constitutively active mutant of AMPK even in the absence of 2-DG. Subsequent analysis revealed that the PAS antibody recognized GFAT1 phosphorylated at Ser243, which is conserved among different species. The assay of the GFAT enzymatic activity in the cell lysates indicated that the 2-DG-treatment inhibited the enzymatic activity, and Compound C-preincubation partially prevented the 2-DG-induced decrease of the activity. Furthermore, the mutant replacing Ser243 by alanine partially prevented the decrease of GFAT activity by 2-DG treatment. These results indicate that the phosphorylation of GFAT1 at Ser243 by AMPK has an important role in the regulation of the GFAT1 enzymatic activity.
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Miyamoto T, Oshiro N, Yoshino KI, Nakashima A, Eguchi S, Takahashi M, Ono Y, Kikkawa U, Yonezawa K. AMP-activated protein kinase phosphorylates Golgi-specific brefeldin A resistance factor 1 at Thr1337 to induce disassembly of Golgi apparatus. J Biol Chem 2007; 283:4430-8. [PMID: 18063581 DOI: 10.1074/jbc.m708296200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sufficiency and depletion of nutrients regulate the cellular activities through the protein phosphorylation reaction; however, many protein substrates remain to be clarified. GBF1 (Golgi-specific brefeldin A resistance factor 1), a guanine nucleotide exchange factor for the ADP-ribosylation factor family associated with the Golgi apparatus, was isolated as a phosphoprotein from the glucose-depleted cells by using the phospho-Akt-substrate antibody, which recognizes the substrate proteins of several protein kinases. The phosphorylation of GBF1 was induced by 2-deoxyglucose (2-DG), which blocks glucose utilization and increases the intracellular AMP concentration, and by AICAR, an AMP-activated protein kinase (AMPK) activator. This phosphorylation was observed in the cells expressing the constitutively active AMPK. The 2-DG-induced phosphorylation of GBF1 was suppressed by Compound C, an AMPK inhibitor, and by the overexpression of the kinase-negative AMPK. Analysis using the deletion and point mutants identified Thr(1337) as the 2-DG-induced phosphorylation site in GBF1, which is phosphorylated by AMPK in vitro. ATP depletion is known to provoke the Golgi apparatus disassembly. Immunofluorescent microscopic analysis with the Golgi markers indicated that GBF1 associates with the fragmented Golgi apparatus in the cells treated with 2-DG and AICAR. The expression of the kinase-negative AMPK and the GBF1 mutant replacing Thr(1337) by Ala prevented the 2-DG-induced Golgi disassembly. These results indicate that GBF1 is a novel AMPK substrate and that the AMPK-mediated phosphorylation of GBF1 at Thr(1337) has a critical role, presumably by attenuating the function of GBF1, in the disassembly of the Golgi apparatus induced under stress conditions that lower the intracellular ATP concentration.
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Nakashima A, Yoshino KI, Miyamoto T, Eguchi S, Oshiro N, Kikkawa U, Yonezawa K. Identification of TBC7 having TBC domain as a novel binding protein to TSC1-TSC2 complex. Biochem Biophys Res Commun 2007; 361:218-23. [PMID: 17658474 DOI: 10.1016/j.bbrc.2007.07.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Accepted: 07/04/2007] [Indexed: 01/17/2023]
Abstract
TBC7, a TBC (Tre-2/Bub2/Cdc16) 1 domain protein, was identified as a novel binding protein to the TSC1-TSC2 tumor suppressor complex by peptide mass fingerprinting analysis of the proteins immunoprecipitated with FLAG-epitope tagged TSC1 and TSC2 from the transfected mammalian cells. The in vivo and in vitro association of TBC7 and the TSC1-TSC2 complex was confirmed by the co-immunoprecipitation and pull-down analysis, respectively, and TBC7 was revealed to bind to the C-terminal half region of TSC1, which is distinct from the binding site with TSC2. The immunofluorescence microscopy and subcellular fractionation showed that TBC7 co-localizes with the tumor suppressor complex in the endomembrane. Overexpression of TBC7 enhanced ubiquitination of TSC1 and increased phosphorylation of S6 protein by S6 kinase, that is located in the mTOR-signaling pathway. These results indicate TBC7 could take a part in the negative regulation of the tumor suppressor complex through facilitating the downregulation of TSC1.
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Oshiro N, Takahashi R, Yoshino KI, Tanimura K, Nakashima A, Eguchi S, Miyamoto T, Hara K, Takehana K, Avruch J, Kikkawa U, Yonezawa K. The proline-rich Akt substrate of 40 kDa (PRAS40) is a physiological substrate of mammalian target of rapamycin complex 1. J Biol Chem 2007; 282:20329-39. [PMID: 17517883 PMCID: PMC3199301 DOI: 10.1074/jbc.m702636200] [Citation(s) in RCA: 256] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The proline-rich Akt substrate of 40 kilodaltons (PRAS40) was identified as a raptor-binding protein that is phosphorylated directly by mammalian target of rapamycin (mTOR) complex 1 (mTORC1) but not mTORC2 in vitro, predominantly at PRAS40 (Ser(183)). The binding of S6K1 and 4E-BP1 to raptor requires a TOR signaling (TOS) motif, which contains an essential Phe followed by four alternating acidic and small hydrophobic amino acids. PRAS40 binding to raptor was severely inhibited by mutation of PRAS40 (Phe(129) to Ala). Immediately carboxyl-terminal to Phe(129) are two small hydrophobic amino acid followed by two acidic residues. PRAS40 binding to raptor was also abolished by mutation of the major mTORC1 phosphorylation site, Ser(183), to Asp. PRAS40 (Ser(183)) was phosphorylated in intact cells; this phosphorylation was inhibited by rapamycin, by 2-deoxyglucose, and by overexpression of the tuberous sclerosis complex heterodimer. PRAS40 (Ser(183)) phosphorylation was also inhibited reversibly by withdrawal of all or of only the branched chain amino acids; this inhibition was reversed by overexpression of the Rheb GTPase. Overexpressed PRAS40 suppressed the phosphorylation of S6K1 and 4E-BP1 at their rapamycin-sensitive phosphorylation sites, and reciprocally, overexpression of S6K1 or 4E-BP1 suppressed phosphorylation of PRAS40 (Ser(183)) and its binding to raptor. RNA interference-induced depletion of PRAS40 enhanced the amino acid-stimulated phosphorylation of both S6K1 and 4E-BP1. These results establish PRAS40 as a physiological mTORC1 substrate that contains a variant TOS motif. Moreover, they indicate that the ability of raptor to bind endogenous substrates is limiting for the activity of mTORC1 in vivo and is therefore a potential locus of regulation.
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Ohji G, Hidayat S, Nakashima A, Tokunaga C, Oshiro N, Yoshino KI, Yokono K, Kikkawa U, Yonezawa K. Suppression of the mTOR-raptor signaling pathway by the inhibitor of heat shock protein 90 geldanamycin. J Biochem 2007; 139:129-35. [PMID: 16428328 DOI: 10.1093/jb/mvj008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Heat shock protein 90 (Hsp90) was co-immunoprecipitated with raptor, the binding partner of the mammalian target of rapamycin (mTOR) from HEK293 cells. Hsp90 was detected in the anti-raptor antibody immunoprecipitates prepared from the cell extract by immunoblot analysis using the anti-Hsp90 antibody, and the association of these two proteins was confirmed by immunoprecipitation from the cells co-expressing Hsp90 and raptor as epitope-tagged molecules. Geldanamycin, a potent inhibitor of Hsp90, disrupted the in vivo binding of Hsp90 to raptor without affecting the association of raptor and mTOR, and suppressed the phosphorylation by mTOR of the downstream translational regulators p70 S6 kinase (S6K) and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1). The protein kinase activity of S6K as well as the phosphorylation of the substrate, 40S ribosomal protein S6, were lowered in the geldanamycin-treated cells. These results indicate that Hsp90 is involved in the regulation of protein translation by facilitating the phosphorylation reaction of 4E-BP1 and S6K catalyzed by the mTOR/raptor complex through the association with raptor, and that the mTOR signaling pathway is a novel target of geldanamycin.
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Avruch J, Hara K, Lin Y, Liu M, Long X, Ortiz-Vega S, Yonezawa K. Insulin and amino-acid regulation of mTOR signaling and kinase activity through the Rheb GTPase. Oncogene 2006; 25:6361-72. [PMID: 17041622 DOI: 10.1038/sj.onc.1209882] [Citation(s) in RCA: 241] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Target of Rapamycin (TOR), a giant protein kinase expressed by all eucaryotic cells, controls cell size in response to nutrient signals. In metazoans, cell and organismal growth is controlled by nutrients and the insulin/insulin-like growth factor (IGF) system, and the understanding of how these inputs coordinately regulate TOR signaling has advanced greatly in the past 5 years. In single-cell eucaryotes and Caenorhabditis elegans, TOR is a dominant regulator of overall mRNA translation, whereas in higher metazoans, TOR controls the expression of a smaller fraction of mRNAs that is especially important to cell growth. TOR signals through two physically distinct multiprotein complexes, and the control of cell growth is mediated primarily by TOR complex 1 (TORC1), which contains the polypeptides raptor and LST8. Raptor is the substrate binding element of TORC1, and the ability of raptor to properly present substrates, such as the translational regulators 4E-BP and p70 S6 kinase, to the TOR catalytic domain is essential for their TOR-catalysed phosphorylation, and is inhibited by the Rapamycin/FKBP-12 complex. The dominant proximal regulator of TORC1 signaling and kinase activity is the ras-like small GTPase Rheb. Rheb binds directly to the mTOR catalytic domain, and Rheb-GTP enables TORC1 to attain an active configuration. Insulin/IGF enhances Rheb GTP charging through the ability of activated Akt to inhibit the Rheb-GTPase-activating function of the tuberous sclerosis heterodimer (TSC1/TSC2). Conversely, energy depletion reduces Rheb-GTP charging through the ability of the adenosine monophosphate-activated protein kinase to phosphorylate TSC2 and stimulate its Rheb-GTPase activating function, as well as by HIFalpha-mediated transcriptional responses that act upstream of the TSC1/2 complex. Amino-acid depletion inhibits TORC1 acting predominantly downstream of the TSC complex, by interfering with the ability of Rheb to bind to mTOR. The components of the insulin/IGF pathway to TORC1 are now well established, whereas the elements mediating the more ancient and functionally dominant input of amino acids remain largely unknown.
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Yamaguchi Y, Shirai Y, Matsubara T, Sanse K, Kuriyama M, Oshiro N, Yoshino KI, Yonezawa K, Ono Y, Saito N. Phosphorylation and Up-regulation of Diacylglycerol Kinase γ via Its Interaction with Protein Kinase Cγ. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84076-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Takahara T, Hara K, Yonezawa K, Sorimachi H, Maeda T. Nutrient-dependent Multimerization of the Mammalian Target of Rapamycin through the N-terminal HEAT Repeat Region. J Biol Chem 2006; 281:28605-14. [PMID: 16870609 DOI: 10.1074/jbc.m606087200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The mammalian target of rapamycin (mTOR) plays a pivotal role in the regulation of cell growth in response to a variety of signals such as nutrients and growth factors. mTOR forms two distinct complexes in vivo. mTORC1 (mTOR complex 1) is rapamycin-sensitive and regulates the rate of protein synthesis in part by phosphorylating two well established effectors, S6K1 (p70 ribosomal S6 kinase 1) and 4E-BP1 (eukaryotic initiation factor 4E-binding protein 1). mTORC2 is rapamycin-insensitive and likely regulates actin organization and activates Akt/protein kinase B. Here, we show that mTOR forms a multimer via its N-terminal HEAT repeat region in mammalian cells. mTOR multimerization is promoted by amino acid sufficiency, although the state of multimerization does not directly correlate with the phosphorylation state of S6K1. mTOR multimerization was insensitive to rapamycin treatment but hindered by butanol treatment, which inhibits phosphatidic acid production by phospholipase D. We also found that mTOR forms a multimer in both mTORC1 and mTORC2. In addition, Saccharomyces cerevisiae TOR proteins Tor1p and Tor2p also exist as homomultimers. These results suggest that TOR multimerization is a conserved mechanism for TOR functioning.
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Honma Y, Kitamura A, Shioda R, Maruyama H, Ozaki K, Oda Y, Mini T, Jenö P, Maki Y, Yonezawa K, Hurt E, Ueno M, Uritani M, Hall MN, Ushimaru T. TOR regulates late steps of ribosome maturation in the nucleoplasm via Nog1 in response to nutrients. EMBO J 2006; 25:3832-42. [PMID: 16888624 PMCID: PMC1553199 DOI: 10.1038/sj.emboj.7601262] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Accepted: 05/06/2006] [Indexed: 01/07/2023] Open
Abstract
The protein kinase TOR (target of rapamycin) controls several steps of ribosome biogenesis, including gene expression of rRNA and ribosomal proteins, and processing of the 35S rRNA precursor, in the budding yeast Saccharomyces cerevisiae. Here we show that TOR also regulates late stages of ribosome maturation in the nucleoplasm via the nuclear GTP-binding protein Nog1. Nog1 formed a complex that included 60S ribosomal proteins and pre-ribosomal proteins Nop7 and Rlp24. The Nog1 complex shuttled between the nucleolus and the nucleoplasm for ribosome biogenesis, but it was tethered to the nucleolus by both nutrient depletion and TOR inactivation, causing cessation of the late stages of ribosome biogenesis. Furthermore, after this, Nog1 and Nop7 proteins were lost, leading to complete cessation of ribosome maturation. Thus, the Nog1 complex is a critical regulator of ribosome biogenesis mediated by TOR. This is the first description of a physiological regulation of nucleolus-to-nucleoplasm translocation of pre-ribosome complexes.
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Yamaguchi Y, Shirai Y, Matsubara T, Sanse K, Kuriyama M, Oshiro N, Yoshino KI, Yonezawa K, Ono Y, Saito N. Phosphorylation and Up-regulation of Diacylglycerol Kinase γ via Its Interaction with Protein Kinase Cγ. J Biol Chem 2006; 281:31627-37. [PMID: 16905533 DOI: 10.1074/jbc.m606992200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Diacylglycerol (DAG) acts as an allosteric activator of protein kinase C (PKC) and is converted to phosphatidic acid by DAG kinase (DGK). Therefore, DGK is thought to be a negative regulator of PKC activation. Here we show molecular mechanisms of functional coupling of the two kinases. gammaPKC directly associated with DGKgamma through its accessory domain (AD), depending on Ca2+ as well as phosphatidylserine/diolein in vitro. Mass spectrometric analysis and mutation studies revealed that gammaPKC phosphorylated Ser-776 and Ser-779 in the AD of DGKgamma. The phosphorylation by gammaPKC resulted in activation of DGKgamma because a DGKgamma mutant in which Ser-776 and Ser-779 were substituted with glutamic acid to mimic phosphorylation exhibited significantly higher activity compared with wild type DGKgamma and an unphosphorylatable DGKgamma mutant. Importantly, the interaction of the two kinases and the phosphorylation of DGKgamma by gammaPKC could be confirmed in vivo, and overexpression of the AD of DGKgamma inhibited re-translocation of gammaPKC. These results demonstrate that localization and activation of the functionally correlated kinases, gammaPKC and DGKgamma, are spatio-temporally orchestrated by their direct association and phosphorylation, contributing to subtype-specific regulation of DGKgamma and DAG signaling.
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Eguchi S, Tokunaga C, Hidayat S, Oshiro N, Yoshino KI, Kikkawa U, Yonezawa K. Different roles for the TOS and RAIP motifs of the translational regulator protein 4E-BP1 in the association with raptor and phosphorylation by mTOR in the regulation of cell size. Genes Cells 2006; 11:757-66. [PMID: 16824195 DOI: 10.1111/j.1365-2443.2006.00977.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The translational regulator protein 4E-BP1, that binds to eukaryotic initiation factor-4E (eIF4E) to prevent the formation of the active translation complex, dissociates from eIF4E by phosphorylation through the mammalian target of rapamycin (mTOR) in the cells stimulated by amino acids. 4E-BP1 has been shown to associate with the scaffold protein raptor through its TOS and RAIP motifs to be recognized by mTOR. We revealed that the TOS motif mutant was phosphorylated by mTOR only at the priming sites of Thr37/46 but the RAIP motif mutant was phosphorylated not only at the priming sites but also at the subsequent site of Thr70 in vitro and in response to amino acid treatment in HEK293 cells. Analysis using the phosphorylation site mutants indicated that phosphorylation of the priming and subsequent sites of 4E-BP1 was required for dissociation from raptor as well as for the release of eIF4E. The expression of the 4E-BP1 mutants replacing the TOS motif and phosphorylation sites, that are poor substrates for mTOR and have no or little dissociation ability from raptor and eIF4E, respectively, significantly reduced the size of K562 cells. These results indicate that the the TOS motif has an essential function whereas the RAIP motif has an accessory role in the association with raptor and mTOR-mediated phosphorylation of 4E-BP1 to dissociate it from raptor and release eIF4E in response to amino acid stimulation leading to the control of cell size.
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