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McDougald DS, Papp TE, Zezulin AU, Zhou S, Bennett J. AKT3 Gene Transfer Promotes Anabolic Reprogramming and Photoreceptor Neuroprotection in a Pre-clinical Model of Retinitis Pigmentosa. Mol Ther 2019; 27:1313-1326. [PMID: 31043342 DOI: 10.1016/j.ymthe.2019.04.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 04/04/2019] [Accepted: 04/08/2019] [Indexed: 10/27/2022] Open
Abstract
Mutations within over 250 known genes are associated with inherited retinal degeneration. Clinical success following gene-replacement therapy for congenital blindness due to RPE65 mutations establishes a platform for the development of downstream treatments targeting other forms of inherited ocular disease. Unfortunately, several challenges relevant to complex disease pathology and limitations of current gene-transfer technologies impede the development of related strategies for each specific form of inherited retinal degeneration. Here, we describe a gene-augmentation strategy that delays retinal degeneration by stimulating features of anabolic metabolism necessary for survival and structural maintenance of photoreceptors. We targeted two critical points of regulation in the canonical insulin/AKT/mammalian target of rapamycin (mTOR) pathway with AAV-mediated gene augmentation in a mouse model of retinitis pigmentosa. AAV vectors expressing the serine/threonine kinase, AKT3, promote dramatic preservation of photoreceptor numbers, structure, and partial visual function. This protective effect was associated with successful reprogramming of photoreceptor metabolism toward pathways associated with cell growth and survival. Collectively, these findings underscore the importance of AKT activity and downstream pathways associated with anabolic metabolism in photoreceptor survival and maintenance.
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Affiliation(s)
- Devin S McDougald
- Center for Advanced Retinal and Ocular Therapeutics, F.M. Kirby Center for Molecular Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Tyler E Papp
- Center for Advanced Retinal and Ocular Therapeutics, F.M. Kirby Center for Molecular Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Alexandra U Zezulin
- Center for Advanced Retinal and Ocular Therapeutics, F.M. Kirby Center for Molecular Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Shangzhen Zhou
- Center for Advanced Retinal and Ocular Therapeutics, F.M. Kirby Center for Molecular Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jean Bennett
- Center for Advanced Retinal and Ocular Therapeutics, F.M. Kirby Center for Molecular Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Harraz MM, Tyagi R, Cortés P, Snyder SH. Antidepressant action of ketamine via mTOR is mediated by inhibition of nitrergic Rheb degradation. Mol Psychiatry 2016; 21:313-9. [PMID: 26782056 DOI: 10.1038/mp.2015.211] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 11/11/2015] [Accepted: 11/24/2015] [Indexed: 12/14/2022]
Abstract
As traditional antidepressants act only after weeks/months, the discovery that ketamine, an antagonist of glutamate/N-methyl-D-aspartate (NMDA) receptors, elicits antidepressant actions in hours has been transformative. Its mechanism of action has been elusive, though enhanced mammalian target of rapamycin (mTOR) signaling is a major feature. We report a novel signaling pathway wherein NMDA receptor activation stimulates generation of nitric oxide (NO), which S-nitrosylates glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Nitrosylated GAPDH complexes with the ubiquitin-E3-ligase Siah1 and Rheb, a small G protein that activates mTOR. Siah1 degrades Rheb leading to reduced mTOR signaling, while ketamine, conversely, stabilizes Rheb that enhances mTOR signaling. Drugs selectively targeting components of this pathway may offer novel approaches to the treatment of depression.
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Yadav RB, Burgos P, Parker AW, Iadevaia V, Proud CG, Allen RA, O'Connell JP, Jeshtadi A, Stubbs CD, Botchway SW. mTOR direct interactions with Rheb-GTPase and raptor: sub-cellular localization using fluorescence lifetime imaging. BMC Cell Biol 2013; 14:3. [PMID: 23311891 PMCID: PMC3549280 DOI: 10.1186/1471-2121-14-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 12/21/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The mammalian target of rapamycin (mTOR) signalling pathway has a key role in cellular regulation and several diseases. While it is thought that Rheb GTPase regulates mTOR, acting immediately upstream, while raptor is immediately downstream of mTOR, direct interactions have yet to be verified in living cells, furthermore the localisation of Rheb has been reported to have only a cytoplasmic cellular localization. RESULTS In this study a cytoplasmic as well as a significant sub-cellular nuclear mTOR localization was shown , utilizing green and red fluorescent protein (GFP and DsRed) fusion and highly sensitive single photon counting fluorescence lifetime imaging microscopy (FLIM) of live cells. The interaction of the mTORC1 components Rheb, mTOR and raptor, tagged with EGFP/DsRed was determined using fluorescence energy transfer-FLIM. The excited-state lifetime of EGFP-mTOR of ~2400 ps was reduced by energy transfer to ~2200 ps in the cytoplasm and to 2000 ps in the nucleus when co-expressed with DsRed-Rheb, similar results being obtained for co-expressed EGFP-mTOR and DsRed-raptor. The localization and distribution of mTOR was modified by amino acid withdrawal and re-addition but not by rapamycin. CONCLUSIONS The results illustrate the power of GFP-technology combined with FRET-FLIM imaging in the study of the interaction of signalling components in living cells, here providing evidence for a direct physical interaction between mTOR and Rheb and between mTOR and raptor in living cells for the first time.
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Affiliation(s)
- Rahul B Yadav
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
| | - Pierre Burgos
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
| | - Anthony W Parker
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
| | - Valentina Iadevaia
- School of Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Christopher G Proud
- School of Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | | | | | - Ananya Jeshtadi
- School of Life Sciences, Headington Campus, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Christopher D Stubbs
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
| | - Stanley W Botchway
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
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Karassek S, Berghaus C, Schwarten M, Goemans CG, Ohse N, Kock G, Jockers K, Neumann S, Gottfried S, Herrmann C, Heumann R, Stoll R. Ras homolog enriched in brain ( Rheb) enhances apoptotic signaling. J Biol Chem 2010; 285:33979-91. [PMID: 20685651 PMCID: PMC2962498 DOI: 10.1074/jbc.m109.095968] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2009] [Revised: 07/19/2010] [Indexed: 12/18/2022] Open
Abstract
Rheb is a homolog of Ras GTPase that regulates cell growth, proliferation, and regeneration via mammalian target of rapamycin (mTOR). Because of the well established potential of activated Ras to promote survival, we sought to investigate the ability of Rheb signaling to phenocopy Ras. We found that overexpression of lipid-anchored Rheb enhanced the apoptotic effects induced by UV light, TNFα, or tunicamycin in an mTOR complex 1 (mTORC1)-dependent manner. Knocking down endogenous Rheb or applying rapamycin led to partial protection, identifying Rheb as a mediator of cell death. Ras and c-Raf kinase opposed the apoptotic effects induced by UV light or TNFα but did not prevent Rheb-mediated apoptosis. To gain structural insight into the signaling mechanisms, we determined the structure of Rheb-GDP by NMR. The complex adopts the typical canonical fold of RasGTPases and displays the characteristic GDP-dependent picosecond to nanosecond backbone dynamics of the switch I and switch II regions. NMR revealed Ras effector-like binding of activated Rheb to the c-Raf-Ras-binding domain (RBD), but the affinity was 1000-fold lower than the Ras/RBD interaction, suggesting a lack of functional interaction. shRNA-mediated knockdown of apoptosis signal-regulating kinase 1 (ASK-1) strongly reduced UV or TNFα-induced apoptosis and suppressed enhancement by Rheb overexpression. In conclusion, Rheb-mTOR activation not only promotes normal cell growth but also enhances apoptosis in response to diverse toxic stimuli via an ASK-1-mediated mechanism. Pharmacological regulation of the Rheb/mTORC1 pathway using rapamycin should take the presence of cellular stress into consideration, as this may have clinical implications.
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Affiliation(s)
| | | | | | | | - Nadine Ohse
- Physical Chemistry I, Faculty of Chemistry and Biochemistry, Ruhr University of Bochum, 44780 Bochum, Germany
| | | | | | | | | | - Christian Herrmann
- Physical Chemistry I, Faculty of Chemistry and Biochemistry, Ruhr University of Bochum, 44780 Bochum, Germany
| | - Rolf Heumann
- From the Departments of Molecular Neurobiochemistry
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Lu ZH, Shvartsman MB, Lee AY, Shao JM, Murray MM, Kladney RD, Fan D, Krajewski S, Chiang GG, Mills GB, Arbeit JM. Mammalian target of rapamycin activator RHEB is frequently overexpressed in human carcinomas and is critical and sufficient for skin epithelial carcinogenesis. Cancer Res 2010; 70:3287-98. [PMID: 20388784 PMCID: PMC2855737 DOI: 10.1158/0008-5472.can-09-3467] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Small GTPase Ras homologue enriched in brain (RHEB) binds and activates the key metabolic regulator mTORC1, which has an important role in cancer cells, but the role of RHEB in cancer pathogenesis has not been shown. By performing a meta-analysis of published cancer cytogenetic and transcriptome databases, we defined a gain of chromosome 7q36.1-q36.3 containing the RHEB locus, an overexpression of RHEB mRNA in several different carcinoma histotypes, and an association between RHEB upregulation and poor prognosis in breast and head and neck cancers. To model gain of function in epithelial malignancy, we targeted Rheb expression to murine basal keratinocytes of transgenic mice at levels similar to those that occur in human squamous cancer cell lines. Juvenile transgenic epidermis displayed constitutive mTORC1 pathway activation, elevated cyclin D1 protein, and diffuse skin hyperplasia. Skin tumors subsequently developed with concomitant stromal angio-inflammatory foci, evidencing induction of an epidermal hypoxia-inducible factor-1 transcriptional program, and paracrine feed-forward activation of the interleukin-6-signal transducer and activator of transcription 3 pathway. Rheb-induced tumor persistence and neoplastic molecular alterations were mTORC1 dependent. Rheb markedly sensitized transgenic epidermis to squamous carcinoma induction following a single dose of Ras-activating carcinogen 7,12-dimethylbenz(a)anthracene. Our findings offer direct evidence that RHEB facilitates multistage carcinogenesis through induction of multiple oncogenic mechanisms, perhaps contributing to the poor prognosis of patients with cancers overexpressing RHEB.
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Affiliation(s)
- Zhi Hong Lu
- Division of Urologic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO 63011
| | - Mark B. Shvartsman
- Division of Urologic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO 63011
| | - Andrew Y. Lee
- Division of Urologic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO 63011
| | - Jenny M. Shao
- Division of Urologic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO 63011
| | - Mollianne M. Murray
- Department of Systems Biology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77054
| | - Raleigh D. Kladney
- Division of Urologic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO 63011
| | - Dong Fan
- Department of General Surgery, Hongqi Hospital, Mudanjiang Medical College, Mudanjiang, Heilongjiang, China, 157001
| | - Stan Krajewski
- Apoptosis and Cell Death Research Program, The Burnham Institute, La Jolla, CA 92037
| | - Gary G. Chiang
- Signal Transduction Program, The Burnham Institute, La Jolla, CA 92037
| | - Gordon B. Mills
- Department of Systems Biology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77054
| | - Jeffrey M. Arbeit
- Division of Urologic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO 63011, Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO 63011, Program in Cell Biology, Washington University School of Medicine, St. Louis, MO 63011,Correspondence: Jeffrey M. Arbeit, 660 South Euclid, Box 8242, St. Louis, MO, 63110.
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Abstract
FKBP38 is a member of the family of FK506-binding proteins that acts as an inhibitor of the mammalian target of rapamycin (mTOR). The inhibitory action of FKBP38 is antagonized by Rheb, an oncogenic small GTPase, which interacts with FKBP38 and prevents its association with mTOR. In addition to the role in mTOR regulation, FKBP38 is also involved in binding and recruiting Bcl-2 and Bcl-X(L), two anti-apoptotic proteins, to mitochondria. In this study, we investigated the possibility that Rheb controls apoptosis by regulating the interaction of FKBP38 with Bcl-2 and Bcl-X(L). We demonstrate in vitro that the interaction of FKBP38 with Bcl-2 is regulated by Rheb in a GTP-dependent manner. In cultured cells, the interaction is controlled by Rheb in response to changes in amino acid and growth factor conditions. Importantly, we found that the Rheb-dependent release of Bcl-X(L) from FKBP38 facilitates the association of this anti-apoptotic protein with the pro-apoptotic protein Bak. Consequently, when Rheb activity increases, cells become more resistant to apoptotic inducers. Our findings reveal a novel mechanism through which growth factors and amino acids control apoptosis.
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Affiliation(s)
- Dongzhu Ma
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213 and
| | - Xiaochun Bai
- the Department of Cell Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, China
| | - Huafei Zou
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213 and
| | - Yumei Lai
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213 and
| | - Yu Jiang
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213 and
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Abstract
TOR complex 1 (TORC1), an oligomer of the mTOR (mammalian target of rapamycin) protein kinase, its substrate binding subunit raptor, and the polypeptide Lst8/GbetaL, controls cell growth in all eukaryotes in response to nutrient availability and in metazoans to insulin and growth factors, energy status, and stress conditions. This review focuses on the biochemical mechanisms that regulate mTORC1 kinase activity, with special emphasis on mTORC1 regulation by amino acids. The dominant positive regulator of mTORC1 is the GTP-charged form of the ras-like GTPase Rheb. Insulin, growth factors, and a variety of cellular stressors regulate mTORC1 by controlling Rheb GTP charging through modulating the activity of the tuberous sclerosis complex, the Rheb GTPase activating protein. In contrast, amino acids, especially leucine, regulate mTORC1 by controlling the ability of Rheb-GTP to activate mTORC1. Rheb binds directly to mTOR, an interaction that appears to be essential for mTORC1 activation. In addition, Rheb-GTP stimulates phospholipase D1 to generate phosphatidic acid, a positive effector of mTORC1 activation, and binds to the mTOR inhibitor FKBP38, to displace it from mTOR. The contribution of Rheb's regulation of PL-D1 and FKBP38 to mTORC1 activation, relative to Rheb's direct binding to mTOR, remains to be fully defined. The rag GTPases, functioning as obligatory heterodimers, are also required for amino acid regulation of mTORC1. As with amino acid deficiency, however, the inhibitory effect of rag depletion on mTORC1 can be overcome by Rheb overexpression, whereas Rheb depletion obviates rag's ability to activate mTORC1. The rag heterodimer interacts directly with mTORC1 and may direct mTORC1 to the Rheb-containing vesicular compartment in response to amino acid sufficiency, enabling Rheb-GTP activation of mTORC1. The type III phosphatidylinositol kinase also participates in amino acid-dependent mTORC1 activation, although the site of action of its product, 3'OH-phosphatidylinositol, in this process is unclear.
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Affiliation(s)
- Joseph Avruch
- Department of Molecular Biology and Diabetes Research Unit, Medical Service, Massachusetts General Hospital, and Department of Medicine, Harvard Medical School, Simches Research Center, Boston, MA 02114, USA.
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Abstract
Tuberous sclerosis complex (TSC) is a genetic disease caused by mutation in either TSC1 or TSC2. The TSC1 and TSC2 gene products form a functional complex and inhibit phosphorylation of S6K and 4EBP1. These functions of TSC1/TSC2 are likely mediated by mTOR. Here we report that TSC2 is a GTPase-activating protein (GAP) toward Rheb, a Ras family GTPase. Rheb stimulates phosphorylation of S6K and 4EBP1. This function of Rheb is blocked by rapamycin and dominant-negative mTOR. Rheb stimulates the phosphorylation of mTOR and plays an essential role in regulation of S6K and 4EBP1 in response to nutrients and cellular energy status. Our data demonstrate that Rheb acts downstream of TSC1/TSC2 and upstream of mTOR to regulate cell growth.
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Affiliation(s)
- Ken Inoki
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
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