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Marafie SK, Al-Mulla F, Abubaker J. mTOR: Its Critical Role in Metabolic Diseases, Cancer, and the Aging Process. Int J Mol Sci 2024; 25:6141. [PMID: 38892329 PMCID: PMC11173325 DOI: 10.3390/ijms25116141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2024] [Revised: 05/26/2024] [Accepted: 05/29/2024] [Indexed: 06/21/2024] Open
Abstract
The mammalian target of rapamycin (mTOR) is a pivotal regulator, integrating diverse environmental signals to control fundamental cellular functions, such as protein synthesis, cell growth, survival, and apoptosis. Embedded in a complex network of signaling pathways, mTOR dysregulation is implicated in the onset and progression of a range of human diseases, including metabolic disorders such as diabetes and cardiovascular diseases, as well as various cancers. mTOR also has a notable role in aging. Given its extensive biological impact, mTOR signaling is a prime therapeutic target for addressing these complex conditions. The development of mTOR inhibitors has proven advantageous in numerous research domains. This review delves into the significance of mTOR signaling, highlighting the critical components of this intricate network that contribute to disease. Additionally, it addresses the latest findings on mTOR inhibitors and their clinical implications. The review also emphasizes the importance of developing more effective next-generation mTOR inhibitors with dual functions to efficiently target the mTOR pathways. A comprehensive understanding of mTOR signaling will enable the development of effective therapeutic strategies for managing diseases associated with mTOR dysregulation.
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Affiliation(s)
- Sulaiman K. Marafie
- Biochemistry and Molecular Biology Department, Dasman Diabetes Institute, P.O. Box 1180, Dasman 15462, Kuwait
| | - Fahd Al-Mulla
- Department of Translational Research, Dasman Diabetes Institute, P.O. Box 1180, Dasman 15462, Kuwait;
| | - Jehad Abubaker
- Biochemistry and Molecular Biology Department, Dasman Diabetes Institute, P.O. Box 1180, Dasman 15462, Kuwait
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2
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Rahman M, Nguyen TM, Lee GJ, Kim B, Park MK, Lee CH. Unraveling the Role of Ras Homolog Enriched in Brain (Rheb1 and Rheb2): Bridging Neuronal Dynamics and Cancer Pathogenesis through Mechanistic Target of Rapamycin Signaling. Int J Mol Sci 2024; 25:1489. [PMID: 38338768 PMCID: PMC10855792 DOI: 10.3390/ijms25031489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/14/2024] [Accepted: 01/17/2024] [Indexed: 02/12/2024] Open
Abstract
Ras homolog enriched in brain (Rheb1 and Rheb2), small GTPases, play a crucial role in regulating neuronal activity and have gained attention for their implications in cancer development, particularly in breast cancer. This study delves into the intricate connection between the multifaceted functions of Rheb1 in neurons and cancer, with a specific focus on the mTOR pathway. It aims to elucidate Rheb1's involvement in pivotal cellular processes such as proliferation, apoptosis resistance, migration, invasion, metastasis, and inflammatory responses while acknowledging that Rheb2 has not been extensively studied. Despite the recognized associations, a comprehensive understanding of the intricate interplay between Rheb1 and Rheb2 and their roles in both nerve and cancer remains elusive. This review consolidates current knowledge regarding the impact of Rheb1 on cancer hallmarks and explores the potential of Rheb1 as a therapeutic target in cancer treatment. It emphasizes the necessity for a deeper comprehension of the molecular mechanisms underlying Rheb1-mediated oncogenic processes, underscoring the existing gaps in our understanding. Additionally, the review highlights the exploration of Rheb1 inhibitors as a promising avenue for cancer therapy. By shedding light on the complicated roles between Rheb1/Rheb2 and cancer, this study provides valuable insights to the scientific community. These insights are instrumental in guiding the identification of novel targets and advancing the development of effective therapeutic strategies for treating cancer.
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Affiliation(s)
- Mostafizur Rahman
- College of Pharmacy, Dongguk University, Seoul 04620, Republic of Korea; (M.R.); (G.J.L.)
| | - Tuan Minh Nguyen
- College of Pharmacy, Dongguk University, Seoul 04620, Republic of Korea; (M.R.); (G.J.L.)
| | - Gi Jeong Lee
- College of Pharmacy, Dongguk University, Seoul 04620, Republic of Korea; (M.R.); (G.J.L.)
| | - Boram Kim
- College of Pharmacy, Dongguk University, Seoul 04620, Republic of Korea; (M.R.); (G.J.L.)
| | - Mi Kyung Park
- Department of BioHealthcare, Hwasung Medi-Science University, Hwaseong-si 18274, Republic of Korea
| | - Chang Hoon Lee
- College of Pharmacy, Dongguk University, Seoul 04620, Republic of Korea; (M.R.); (G.J.L.)
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Wu H, Wei M, Li Y, Ma Q, Zhang H. Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma. Front Mol Neurosci 2022; 15. [DOI: https:/doi.org/10.3389/fnmol.2022.910543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023] Open
Abstract
As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.
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Wu H, Wei M, Li Y, Ma Q, Zhang H. Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma. Front Mol Neurosci 2022; 15:910543. [PMID: 35935338 PMCID: PMC9354928 DOI: 10.3389/fnmol.2022.910543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 05/30/2022] [Indexed: 11/17/2022] Open
Abstract
As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.
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Affiliation(s)
- Hao Wu
- Graduate School of Dalian Medical University, Dalian, China
- Department of Neurosurgery, The Yangzhou School of Clinical Medicine of Dalian Medical University, Dalian, China
| | - Min Wei
- Graduate School of Dalian Medical University, Dalian, China
- Department of Neurosurgery, The Yangzhou School of Clinical Medicine of Dalian Medical University, Dalian, China
| | - Yuping Li
- Department of Neurosurgery, The Yangzhou School of Clinical Medicine of Dalian Medical University, Dalian, China
| | - Qiang Ma
- Department of Neurosurgery, The Yangzhou School of Clinical Medicine of Dalian Medical University, Dalian, China
| | - Hengzhu Zhang
- Graduate School of Dalian Medical University, Dalian, China
- Department of Neurosurgery, The Yangzhou School of Clinical Medicine of Dalian Medical University, Dalian, China
- *Correspondence: Hengzhu Zhang,
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Vallée A, Lecarpentier Y, Vallée JN. The Key Role of the WNT/β-Catenin Pathway in Metabolic Reprogramming in Cancers under Normoxic Conditions. Cancers (Basel) 2021; 13:cancers13215557. [PMID: 34771718 PMCID: PMC8582658 DOI: 10.3390/cancers13215557] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 11/03/2021] [Accepted: 11/04/2021] [Indexed: 12/12/2022] Open
Abstract
Simple Summary The canonical WNT/β-catenin pathway is upregulated in cancers and plays a major role in proliferation, invasion, apoptosis and angiogenesis. Recent studies have shown that cancer processes are involved under normoxic conditions. These findings completely change the way of approaching the study of the cancer process. In this review, we focus on the fact that, under normoxic conditions, the overstimulation of the WNT/β-catenin pathway leads to modifications in the tumor micro-environment and the activation of the Warburg effect, i.e., aerobic glycolysis, autophagy and glutaminolysis, which in turn participate in tumor growth. Abstract The canonical WNT/β-catenin pathway is upregulated in cancers and plays a major role in proliferation, invasion, apoptosis and angiogenesis. Nuclear β-catenin accumulation is associated with cancer. Hypoxic mechanisms lead to the activation of the hypoxia-inducible factor (HIF)-1α, promoting glycolytic and energetic metabolism and angiogenesis. However, HIF-1α is degraded by the HIF prolyl hydroxylase under normoxia, conditions under which the WNT/β-catenin pathway can activate HIF-1α. This review is therefore focused on the interaction between the upregulated WNT/β-catenin pathway and the metabolic processes underlying cancer mechanisms under normoxic conditions. The WNT pathway stimulates the PI3K/Akt pathway, the STAT3 pathway and the transduction of WNT/β-catenin target genes (such as c-Myc) to activate HIF-1α activity in a hypoxia-independent manner. In cancers, stimulation of the WNT/β-catenin pathway induces many glycolytic enzymes, which in turn induce metabolic reprogramming, known as the Warburg effect or aerobic glycolysis, leading to lactate overproduction. The activation of the Wnt/β-catenin pathway induces gene transactivation via WNT target genes, c-Myc and cyclin D1, or via HIF-1α. This in turn encodes aerobic glycolysis enzymes, including glucose transporter, hexokinase 2, pyruvate kinase M2, pyruvate dehydrogenase kinase 1 and lactate dehydrogenase-A, leading to lactate production. The increase in lactate production is associated with modifications to the tumor microenvironment and tumor growth under normoxic conditions. Moreover, increased lactate production is associated with overexpression of VEGF, a key inducer of angiogenesis. Thus, under normoxic conditions, overstimulation of the WNT/β-catenin pathway leads to modifications of the tumor microenvironment and activation of the Warburg effect, autophagy and glutaminolysis, which in turn participate in tumor growth.
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Affiliation(s)
- Alexandre Vallée
- Department of Clinical Research and Innovation (DRCI), Foch Hospital, 92150 Suresnes, France
- Correspondence:
| | - Yves Lecarpentier
- Centre de Recherche Clinique, Grand Hôpital de l’Est Francilien (GHEF), 6-8 Rue Saint-Fiacre, 77100 Meaux, France;
| | - Jean-Noël Vallée
- Centre Hospitalier Universitaire (CHU) Amiens Picardie, Université Picardie Jules Verne (UPJV), 80054 Amiens, France;
- Laboratoire de Mathématiques et Applications (LMA), UMR, CNRS 7348, Université de Poitiers, 86000 Poitiers, France
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Xiao B, Zuo D, Hirukawa A, Cardiff RD, Lamb R, Sonenberg N, Muller WJ. Rheb1-Independent Activation of mTORC1 in Mammary Tumors Occurs through Activating Mutations in mTOR. Cell Rep 2021; 31:107571. [PMID: 32348753 DOI: 10.1016/j.celrep.2020.107571] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 12/06/2019] [Accepted: 04/02/2020] [Indexed: 11/25/2022] Open
Abstract
Mechanistic target of rapamycin complex 1 (mTORC1) is a master modulator of cellular growth, and its aberrant regulation is recurrently documented within breast cancer. While the small GTPase Rheb1 is the canonical activator of mTORC1, Rheb1-independent mechanisms of mTORC1 activation have also been reported but have not been fully understood. Employing multiple transgenic mouse models of breast cancer, we report that ablation of Rheb1 significantly impedes mammary tumorigenesis. In the absence of Rheb1, a block in tumor initiation can be overcome by multiple independent mutations in Mtor to allow Rheb1-independent reactivation of mTORC1. We further demonstrate that the mTOR kinase is indispensable for tumor initiation as the genetic ablation of mTOR abolishes mammary tumorigenesis. Collectively, our findings demonstrate that mTORC1 activation is indispensable for mammary tumor initiation and that tumors acquire alternative mechanisms of mTORC1 activation.
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Affiliation(s)
- Bin Xiao
- Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada; Rosalind & Morris Goodman Cancer Centre, McGill University, Montreal, QC H3A 1A3, Canada
| | - Dongmei Zuo
- Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada; Rosalind & Morris Goodman Cancer Centre, McGill University, Montreal, QC H3A 1A3, Canada
| | - Alison Hirukawa
- Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada; Rosalind & Morris Goodman Cancer Centre, McGill University, Montreal, QC H3A 1A3, Canada
| | - Robert D Cardiff
- Center for Comparative Medicine, University of California, Davis, Davis, CA 95616, USA
| | | | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada; Faculty of Medicine, McGill University, Montreal, QC H3A 1A3, Canada; Rosalind & Morris Goodman Cancer Centre, McGill University, Montreal, QC H3A 1A3, Canada
| | - William J Muller
- Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada; Faculty of Medicine, McGill University, Montreal, QC H3A 1A3, Canada; Rosalind & Morris Goodman Cancer Centre, McGill University, Montreal, QC H3A 1A3, Canada.
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7
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Afify SM, Oo AKK, Hassan G, Seno A, Seno M. How can we turn the PI3K/AKT/mTOR pathway down? Insights into inhibition and treatment of cancer. Expert Rev Anticancer Ther 2021; 21:605-619. [PMID: 33857392 DOI: 10.1080/14737140.2021.1918001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Introduction: The phosphatidylinositol 3-kinase/protein kinase-B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway is a fundamental regulator of cell proliferation and survival. Dysregulation in this pathway leads to the development of cancer. Accumulating evidence indicates that dysregulation in this pathway is involved in cancer initiation, progression, and recurrence. However, the pathway consists of various signal transducing factors related with cellular events, such as transformation, tumorigenesis, cancer progression, and drug resistance. Therefore, it is very important to determine the targets in this pathway for cancer therapy. Although many drugs inhibiting this signaling pathway are in clinical trials or have been approved for treating solid tumors and hematologic malignancies, further understanding of the signaling mechanism is required to achieve better therapeutic efficacy.Areas covered: In this review, we have describe the PI3K/AKT/mTOR pathway in detail, along with its critical role in cancer stem cells, for identifying potential therapeutic targets. We also summarize the recent developments in different types of signaling inhibitors.Expert opinion: Downregulation of the PI3K/AKT/mTOR pathway is very important for treating all types of cancers. Thus, further studies are required to establish novel prognostic factors to support the current progress in cancer treatment with emphasis on this pathway.
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Affiliation(s)
- Said M Afify
- Department of Biotechnology and Drug Discovery, Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama, Japan.,Division of Biochemistry, Chemistry Department, Faculty of Science, Menoufia University, Shebin, El Kom-Menoufia, Egypt
| | - Aung Ko Ko Oo
- Department of Biotechnology, Mandalay Technological University, Mandalay, Myanmar
| | - Ghmkin Hassan
- Department of Biotechnology and Drug Discovery, Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama, Japan.,Department of Microbiology and Biochemistry, Faculty of Pharmacy, Damascus University, Damascus, Syria
| | - Akimasa Seno
- Department of Biotechnology and Drug Discovery, Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama, Japan
| | - Masaharu Seno
- Department of Biotechnology and Drug Discovery, Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama, Japan
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8
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Transcriptomic Changes Associated with Loss of Cell Viability Induced by Oxysterol Treatment of a Retinal Photoreceptor-Derived Cell Line: An In Vitro Model of Smith-Lemli-Opitz Syndrome. Int J Mol Sci 2021; 22:ijms22052339. [PMID: 33652836 PMCID: PMC7956713 DOI: 10.3390/ijms22052339] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/19/2021] [Accepted: 02/21/2021] [Indexed: 11/17/2022] Open
Abstract
Smith–Lemli–Opitz Syndrome (SLOS) results from mutations in the gene encoding the enzyme DHCR7, which catalyzes conversion of 7-dehydrocholesterol (7DHC) to cholesterol (CHOL). Rats treated with a DHCR7 inhibitor serve as a SLOS animal model, and exhibit progressive photoreceptor-specific cell death, with accumulation of 7DHC and oxidized sterols. To understand the basis of this cell type specificity, we performed transcriptomic analyses on a photoreceptor-derived cell line (661W), treating cells with two 7DHC-derived oxysterols, which accumulate in tissues and bodily fluids of SLOS patients and in the rat SLOS model, as well as with CHOL (negative control), and evaluated differentially expressed genes (DEGs) for each treatment. Gene enrichment analysis and compilation of DEG sets indicated that endoplasmic reticulum stress, oxidative stress, DNA damage and repair, and autophagy were all highly up-regulated pathways in oxysterol-treated cells. Detailed analysis indicated that the two oxysterols exert their effects via different molecular mechanisms. Changes in expression of key genes in highlighted pathways (Hmox1, Ddit3, Trib3, and Herpud1) were validated by immunofluorescence confocal microscopy. The results extend our understanding of the pathobiology of retinal degeneration and SLOS, identifying potential new druggable targets for therapeutic intervention into these and other related orphan diseases.
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Sato T, Mukai S, Ikeda H, Mishiro-Sato E, Akao K, Kobayashi T, Hino O, Shimono W, Shibagaki Y, Hattori S, Sekido Y. Silencing of SmgGDS, a Novel mTORC1 Inducer That Binds to RHEBs, Inhibits Malignant Mesothelioma Cell Proliferation. Mol Cancer Res 2021; 19:921-931. [PMID: 33574130 DOI: 10.1158/1541-7786.mcr-20-0637] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 12/15/2020] [Accepted: 02/04/2021] [Indexed: 11/16/2022]
Abstract
Malignant mesothelioma (MM) is an aggressive tumor that typically develops after a long latency following asbestos exposure. Although mechanistic target of rapamycin complex 1 (mTORC1) activation enhances MM cell growth, the mTORC1 inhibitor everolimus has shown limited efficacy in clinical trials of MM patients. We explored the mechanism underlying mTORC1 activation in MM cells and its effects on cell proliferation and progression. Analysis of the expression profiles of 87 MMs from The Cancer Genome Atlas revealed that 40 samples (46%) displayed altered expression of RPTOR (mTORC1 component) and genes immediately upstream that activate mTORC1. Among them, we focused on RHEB and RHEBL1, which encode direct activators of mTORC1. Exogenous RHEBL1 expression enhanced MM cell growth, indicating that RHEB-mTORC1 signaling acts as a pro-oncogenic cascade. We investigated molecules that directly activate RHEBs, identifying SmgGDS as a novel RHEB-binding protein. SmgGDS knockdown reduced mTORC1 activation and inhibited the proliferation of MM cells with mTORC1 activation. Interestingly, SmgGDS displayed high binding affinity with inactive GDP-bound RHEBL1, and its knockdown reduced cytosolic RHEBL1 without affecting its activation. These findings suggest that SmgGDS retains GDP-bound RHEBs in the cytosol, whereas GTP-bound RHEBs are localized on intracellular membranes to promote mTORC1 activation. We revealed a novel role for SmgGDS in the RHEB-mTORC1 pathway and its potential as a therapeutic target in MM with aberrant mTORC1 activation. IMPLICATIONS: Our data showing that SmgGDS regulates RHEB localization to activate mTORC1 indicate that SmgGDS can be used as a new therapeutic target for MM exhibiting mTORC1 activation.
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Affiliation(s)
- Tatsuhiro Sato
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan
| | - Satomi Mukai
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan
| | - Haruna Ikeda
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan
| | - Emi Mishiro-Sato
- Division of Pathophysiology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan
| | - Ken Akao
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan.,Department of Respiratory Medicine, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
| | - Toshiyuki Kobayashi
- Department of Molecular Pathogenesis, Graduate School of Medicine, Juntendo University, Bunkyo-ku, Tokyo, Japan
| | - Okio Hino
- Department of Molecular Pathogenesis, Graduate School of Medicine, Juntendo University, Bunkyo-ku, Tokyo, Japan
| | - Wataru Shimono
- Division of Biochemistry, School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Yoshio Shibagaki
- Division of Biochemistry, School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Seisuke Hattori
- Division of Biochemistry, School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Yoshitaka Sekido
- Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi, Japan. .,Division of Molecular and Cellular Oncology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
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10
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Prakash P. A regulatory role of membrane by direct modulation of the catalytic kinase domain. Small GTPases 2020; 12:246-256. [PMID: 32663062 DOI: 10.1080/21541248.2020.1788886] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Cell membrane modulates the function and activity of specific proteins and acts more than just a non-specific scaffolding machinery. In this review, I focus on studies that highlight a direct membrane-mediated modulation of the catalytic kinase domain of a variety of kinases thereby regulating the kinase activity. It emerges that membrane provides a second level of regulation once kinase domain is relieved of its inactive auto-inhibitory state. For the first time a generalized regulatory role of membrane is proposed that governs the kinase activity by modulating the catalytic kinase domain. Striking similarities among a variety of multi-domain kinases as well as single-domain lipidated enzymes such as RAS proteins are presented.
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Affiliation(s)
- Priyanka Prakash
- Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA
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11
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Hansmann P, Brückner A, Kiontke S, Berkenfeld B, Seebohm G, Brouillard P, Vikkula M, Jansen FE, Nellist M, Oeckinghaus A, Kümmel D. Structure of the TSC2 GAP Domain: Mechanistic Insight into Catalysis and Pathogenic Mutations. Structure 2020; 28:933-942.e4. [PMID: 32502382 DOI: 10.1016/j.str.2020.05.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 02/06/2020] [Accepted: 05/15/2020] [Indexed: 12/17/2022]
Abstract
The TSC complex is the cognate GTPase-activating protein (GAP) for the small GTPase Rheb and a crucial regulator of the mechanistic target of rapamycin complex 1 (mTORC1). Mutations in the TSC1 and TSC2 subunits of the complex cause tuberous sclerosis complex (TSC). We present the crystal structure of the catalytic asparagine-thumb GAP domain of TSC2. A model of the TSC2-Rheb complex and molecular dynamics simulations suggest that TSC2 Asn1643 and Rheb Tyr35 are key active site residues, while Rheb Arg15 and Asp65, previously proposed as catalytic residues, contribute to the TSC2-Rheb interface and indirectly aid catalysis. The TSC2 GAP domain is further stabilized by interactions with other TSC2 domains. We characterize TSC2 variants that partially affect TSC2 functionality and are associated with atypical symptoms in patients, suggesting that mutations in TSC1 and TSC2 might predispose to neurological and vascular disorders without fulfilling the clinical criteria for TSC.
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Affiliation(s)
- Patrick Hansmann
- Westfälische Wilhelms-Universität, Institute of Biochemistry, Wilhelm Klemm-Str. 2, 48149 Münster, Germany
| | - Anne Brückner
- Westfälische Wilhelms-Universität, Institute of Biochemistry, Wilhelm Klemm-Str. 2, 48149 Münster, Germany; Westfälische Wilhelms-Universität, Institute of Molecular Tumor Biology, Robert-Koch-Str. 43, 48149 Münster, Germany
| | - Stephan Kiontke
- Philipps-Universität Marburg, Faculty of Biology, Department of Plant Physiology and Photobiology, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany
| | - Bianca Berkenfeld
- Westfälische Wilhelms-Universität, Institute of Biochemistry, Wilhelm Klemm-Str. 2, 48149 Münster, Germany
| | - Guiscard Seebohm
- University Hospital Münster, Institute for Genetics of Heart Diseases, Department of Cardiovascular Medicine, Robert-Koch-Str. 45, 48149 Münster, Germany
| | - Pascal Brouillard
- Université Catholique de Louvain, de Duve Institute, Human Molecular Genetics, Brussels, Belgium
| | - Miikka Vikkula
- Université Catholique de Louvain, de Duve Institute, Human Molecular Genetics, Brussels, Belgium; WELBIO (Walloon Excellence in Lifesciences and Biotechnology), de Duve Institute, Université Catholique de Louvain, Brussels, Belgium
| | - Floor E Jansen
- Department of Child Neurology, Brain Center UMC Utrecht, Utrecht, the Netherlands
| | - Mark Nellist
- Department of Clinical Genetics, Erasmus Medical Center, Wytemaweg 80, 3015 CN Rotterdam, the Netherlands
| | - Andrea Oeckinghaus
- Westfälische Wilhelms-Universität, Institute of Molecular Tumor Biology, Robert-Koch-Str. 43, 48149 Münster, Germany
| | - Daniel Kümmel
- Westfälische Wilhelms-Universität, Institute of Biochemistry, Wilhelm Klemm-Str. 2, 48149 Münster, Germany.
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12
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Yazar V, Kilic G, Bulut O, Canavar Yildirim T, Yagci FC, Aykut G, Klinman DM, Gursel M, Gursel I. A suppressive oligodeoxynucleotide expressing TTAGGG motifs modulates cellular energetics through the mTOR signaling pathway. Int Immunol 2020; 32:39-48. [PMID: 31633763 DOI: 10.1093/intimm/dxz059] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 09/20/2019] [Indexed: 02/04/2023] Open
Abstract
Immune-mediated inflammation must be down-regulated to facilitate tissue remodeling during homeostatic restoration of an inflammatory response. Uncontrolled or over-exuberant immune activation can cause autoimmune diseases, as well as tissue destruction. A151, the archetypal example of a chemically synthesized suppressive oligodeoxynucleotide (ODN) based on repetitive telomere-derived TTAGGG sequences, was shown to successfully down-regulate a variety of immune responses. However, the degree, duration and breadth of A151-induced transcriptome alterations remain elusive. Here, we performed a comprehensive microarray analysis in combination with Ingenuity Pathway Analysis (IPA) using murine splenocytes to investigate the underlying mechanism of A151-dependent immune suppression. Our results revealed that A151 significantly down-regulates critical mammalian target of rapamycin (mTOR) activators (Pi3kcd, Pdpk1 and Rheb), elements downstream of mTOR signaling (Rps6ka1, Myc, Stat3 and Slc2a1), an important component of the mTORC2 protein complex (Rictor) and Mtor itself. The effects of A151 on mTOR signaling were dose- and time-dependent. Moreover, flow cytometry and immunoblotting analyses demonstrated that A151 is able to reverse mTOR phosphorylation comparably to the well-known mTOR inhibitor rapamycin. Furthermore, Seahorse metabolic assays showed an A151 ODN-induced decrease in both oxygen consumption and glycolysis implying that a metabolically inert state in macrophages could be triggered by A151 treatment. Overall, our findings suggested novel insights into the mechanism by which the immune system is metabolically modulated by A151 ODN.
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Affiliation(s)
- Volkan Yazar
- Thorlab-Therapeutic Oligodeoxynucleotide Research Laboratory, Department of Molecular Biology and Genetics, Faculty of Science, Ihsan Dogramaci Bilkent University, Ankara, Turkey
| | - Gizem Kilic
- Thorlab-Therapeutic Oligodeoxynucleotide Research Laboratory, Department of Molecular Biology and Genetics, Faculty of Science, Ihsan Dogramaci Bilkent University, Ankara, Turkey
| | - Ozlem Bulut
- Thorlab-Therapeutic Oligodeoxynucleotide Research Laboratory, Department of Molecular Biology and Genetics, Faculty of Science, Ihsan Dogramaci Bilkent University, Ankara, Turkey
| | - Tugce Canavar Yildirim
- Thorlab-Therapeutic Oligodeoxynucleotide Research Laboratory, Department of Molecular Biology and Genetics, Faculty of Science, Ihsan Dogramaci Bilkent University, Ankara, Turkey
| | - Fuat C Yagci
- Thorlab-Therapeutic Oligodeoxynucleotide Research Laboratory, Department of Molecular Biology and Genetics, Faculty of Science, Ihsan Dogramaci Bilkent University, Ankara, Turkey
| | - Gamze Aykut
- Thorlab-Therapeutic Oligodeoxynucleotide Research Laboratory, Department of Molecular Biology and Genetics, Faculty of Science, Ihsan Dogramaci Bilkent University, Ankara, Turkey
| | - Dennis M Klinman
- Immune Modulation Section, Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Mayda Gursel
- Department of Biological Sciences, Middle East Technical University, Ankara, Turkey
| | - Ihsan Gursel
- Thorlab-Therapeutic Oligodeoxynucleotide Research Laboratory, Department of Molecular Biology and Genetics, Faculty of Science, Ihsan Dogramaci Bilkent University, Ankara, Turkey
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13
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Abstract
A complex molecular machinery converges on the surface of lysosomes to ensure that the growth-promoting signaling mediated by mechanistic target of rapamycin complex 1 (mTORC1) is tightly controlled by the availability of nutrients and growth factors. The final step in this activation process is dependent on Rheb, a small GTPase that binds to mTOR and allosterically activates its kinase activity. Here we review the mechanisms that determine the subcellular localization of Rheb (and the closely related RhebL1 protein) as well as the significance of these mechanisms for controlling mTORC1 activation. In particular, we explore how the relatively weak membrane interactions conferred by C-terminal farnesylation are critical for the ability of Rheb to activate mTORC1. In addition to supporting transient membrane interactions, Rheb C-terminal farnesylation also supports an interaction between Rheb and the δ subunit of phosphodiesterase 6 (PDEδ). This interaction provides a potential mechanism for targeting Rheb to membranes that contain Arl2, a small GTPase that triggers the release of prenylated proteins from PDEδ. The minimal membrane targeting conferred by C-terminal farnesylation of Rheb and RhebL1 distinguishes them from other members of the Ras superfamily that possess additional membrane interaction motifs that work with farnesylation for enrichment on the specific subcellular membranes where they engage key effectors. Finally, we highlight diversity in Rheb membrane targeting mechanisms as well as the potential for alternative mTORC1 activation mechanisms across species.
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Affiliation(s)
- Brittany Angarola
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Department of Neuroscience, Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Shawn M Ferguson
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, 06510, USA.,Department of Neuroscience, Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, 06510, USA
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14
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Mutvei AP, Nagiec MJ, Hamann JC, Kim SG, Vincent CT, Blenis J. Rap1-GTPases control mTORC1 activity by coordinating lysosome organization with amino acid availability. Nat Commun 2020; 11:1416. [PMID: 32184389 PMCID: PMC7078236 DOI: 10.1038/s41467-020-15156-5] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 02/17/2020] [Indexed: 02/08/2023] Open
Abstract
The kinase mTOR complex 1 (mTORC1) promotes cellular growth and is frequently dysregulated in cancers. In response to nutrients, mTORC1 is activated on lysosomes by Rag and Rheb guanosine triphosphatases (GTPases) and drives biosynthetic processes. How limitations in nutrients suppress mTORC1 activity remains poorly understood. We find that when amino acids are limited, the Rap1-GTPases confine lysosomes to the perinuclear region and reduce lysosome abundance, which suppresses mTORC1 signaling. Rap1 activation, which is independent of known amino acid signaling factors, limits the lysosomal surface available for mTORC1 activation. Conversely, Rap1 depletion expands the lysosome population, which markedly increases association between mTORC1 and its lysosome-borne activators, leading to mTORC1 hyperactivity. Taken together, we establish Rap1 as a critical coordinator of the lysosomal system, and propose that aberrant changes in lysosomal surface availability can impact mTORC1 signaling output.
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Affiliation(s)
- Anders P Mutvei
- Weill Cornell Medicine, Sandra and Edward Meyer Cancer Center, Belfer Research Building, 413 E. 69th St., New York, NY, 10021, USA.
- Karolinska Institutet, Department of Microbiology, Tumor and Cell biology, Nobels väg 16, KI Solna Campus Karolinska Institutet, Box 280, SE-171 77, Stockholm, Sweden.
- Department of Immunology, Genetics and Pathology, Uppsala University, Rudbeck Laboratory, 751 85, Uppsala, Sweden.
| | - Michal J Nagiec
- Weill Cornell Medicine, Sandra and Edward Meyer Cancer Center, Belfer Research Building, 413 E. 69th St., New York, NY, 10021, USA
| | - Jens C Hamann
- Weill Cornell Medicine, Sandra and Edward Meyer Cancer Center, Belfer Research Building, 413 E. 69th St., New York, NY, 10021, USA
| | - Sang Gyun Kim
- Weill Cornell Medicine, Sandra and Edward Meyer Cancer Center, Belfer Research Building, 413 E. 69th St., New York, NY, 10021, USA
| | - C Theresa Vincent
- Department of Immunology, Genetics and Pathology, Uppsala University, Rudbeck Laboratory, 751 85, Uppsala, Sweden
- Department of Microbiology, New York University School of Medicine, New York, NY, USA
| | - John Blenis
- Weill Cornell Medicine, Sandra and Edward Meyer Cancer Center, Belfer Research Building, 413 E. 69th St., New York, NY, 10021, USA.
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15
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Bertrams W, Griss K, Han M, Seidel K, Klemmer A, Sittka-Stark A, Hippenstiel S, Suttorp N, Finkernagel F, Wilhelm J, Greulich T, Vogelmeier CF, Vera J, Schmeck B. Transcriptional analysis identifies potential biomarkers and molecular regulators in pneumonia and COPD exacerbation. Sci Rep 2020; 10:241. [PMID: 31937830 PMCID: PMC6959367 DOI: 10.1038/s41598-019-57108-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 12/20/2019] [Indexed: 01/16/2023] Open
Abstract
Lower respiratory infections, such as community-acquired pneumonia (CAP), and chronic obstructive pulmonary disease (COPD) rank among the most frequent causes of death worldwide. Improved diagnostics and profound pathophysiological insights are urgent clinical needs. In our cohort, we analysed transcriptional networks of peripheral blood mononuclear cells (PBMCs) to identify central regulators and potential biomarkers. We investigated the mRNA- and miRNA-transcriptome of PBMCs of healthy subjects and patients suffering from CAP or AECOPD by microarray and Taqman Low Density Array. Genes that correlated with PBMC composition were eliminated, and remaining differentially expressed genes were grouped into modules. One selected module (120 genes) was particularly suitable to discriminate AECOPD and CAP and most notably contained a subset of five biologically relevant mRNAs that differentiated between CAP and AECOPD with an AUC of 86.1%. Likewise, we identified several microRNAs, e.g. miR-545-3p and miR-519c-3p, which separated AECOPD and CAP. We furthermore retrieved an integrated network of differentially regulated mRNAs and microRNAs and identified HNF4A, MCC and MUC1 as central network regulators or most important discriminatory markers. In summary, transcriptional analysis retrieved potential biomarkers and central molecular features of CAP and AECOPD.
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Affiliation(s)
- Wilhelm Bertrams
- Institute for Lung Research, Universities of Giessen and Marburg Lung Center, German Center for Lung Research (DZL), Marburg, Germany
| | - Kathrin Griss
- Department of Internal Medicine/Infectious Diseases and Respiratory Medicine, Charité - University Medicine Berlin, Berlin, Germany
| | - Maria Han
- Department of Internal Medicine/Infectious Diseases and Respiratory Medicine, Charité - University Medicine Berlin, Berlin, Germany
| | - Kerstin Seidel
- Institute for Lung Research, Universities of Giessen and Marburg Lung Center, German Center for Lung Research (DZL), Marburg, Germany
| | - Andreas Klemmer
- Pulmonary and Critical Care Medicine, University Medical Center Giessen and Marburg, German Center for Lung Research (DZL), Marburg, Germany
| | - Alexandra Sittka-Stark
- Institute for Lung Research, Universities of Giessen and Marburg Lung Center, German Center for Lung Research (DZL), Marburg, Germany
| | - Stefan Hippenstiel
- Department of Internal Medicine/Infectious Diseases and Respiratory Medicine, Charité - University Medicine Berlin, Berlin, Germany
| | - Norbert Suttorp
- Department of Internal Medicine/Infectious Diseases and Respiratory Medicine, Charité - University Medicine Berlin, Berlin, Germany
| | - Florian Finkernagel
- Institute of Molecular Biology and Tumor Research (IMT), Genomics Core Facility, Philipps-University of Marburg, Marburg, Germany
| | - Jochen Wilhelm
- Justus-Liebig-University, Universities Giessen & Marburg Lung Center, German Center for Lung Research (DZL), Giessen, Germany
| | - Timm Greulich
- Pulmonary and Critical Care Medicine, University Medical Center Giessen and Marburg, German Center for Lung Research (DZL), Marburg, Germany
| | - Claus F Vogelmeier
- Pulmonary and Critical Care Medicine, University Medical Center Giessen and Marburg, German Center for Lung Research (DZL), Marburg, Germany
| | - Julio Vera
- Laboratory of Systems Tumor Immunology, Department of Dermatology, Universitätsklinikum Erlangen and Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Bernd Schmeck
- Institute for Lung Research, Universities of Giessen and Marburg Lung Center, German Center for Lung Research (DZL), Marburg, Germany. .,Pulmonary and Critical Care Medicine, University Medical Center Giessen and Marburg, German Center for Lung Research (DZL), Marburg, Germany. .,Center for Synthetic Microbiology (SYNMIKRO), Philipps-University of Marburg, Marburg, Germany. .,German Center for Infection Research (DZIF), partner site Giessen-Marburg-Langen, Marburg, Germany.
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16
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Angarola B, Ferguson SM. Weak membrane interactions allow Rheb to activate mTORC1 signaling without major lysosome enrichment. Mol Biol Cell 2019; 30:2750-2760. [PMID: 31532697 PMCID: PMC6789162 DOI: 10.1091/mbc.e19-03-0146] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Stable localization of the Rheb GTPase to lysosomes is thought to be required for activation of mTOR complex 1 (mTORC1) signaling. However, the lysosome targeting mechanisms for Rheb remain unclear. We therefore investigated the relationship between Rheb subcellular localization and mTORC1 activation. Surprisingly, we found that Rheb was undetectable at lysosomes. Nonetheless, functional assays in knockout human cells revealed that farnesylation of the C-terminal CaaX motif on Rheb was essential for Rheb-dependent mTORC1 activation. Although farnesylated Rheb exhibited partial endoplasmic reticulum (ER) localization, constitutively targeting Rheb to ER membranes did not support mTORC1 activation. Further systematic analysis of Rheb lipidation revealed that weak, nonselective, membrane interactions support Rheb-dependent mTORC1 activation without the need for a specific lysosome targeting motif. Collectively, these results argue against stable interactions of Rheb with lysosomes and instead that transient membrane interactions optimally allow Rheb to activate mTORC1 signaling.
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Affiliation(s)
- Brittany Angarola
- Departments of Cell Biology and Neuroscience, Yale University School of Medicine, New Haven, CT 06510
| | - Shawn M Ferguson
- Departments of Cell Biology and Neuroscience, Yale University School of Medicine, New Haven, CT 06510
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17
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Vallée A, Guillevin R, Vallée JN. Vasculogenesis and angiogenesis initiation under normoxic conditions through Wnt/β-catenin pathway in gliomas. Rev Neurosci 2018; 29:71-91. [PMID: 28822229 DOI: 10.1515/revneuro-2017-0032] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 06/25/2017] [Indexed: 12/11/2022]
Abstract
The canonical Wnt/β-catenin pathway is up-regulated in gliomas and involved in proliferation, invasion, apoptosis, vasculogenesis and angiogenesis. Nuclear β-catenin accumulation correlates with malignancy. Hypoxia activates hypoxia-inducible factor (HIF)-1α by inhibiting HIF-1α prolyl hydroxylation, which promotes glycolytic energy metabolism, vasculogenesis and angiogenesis, whereas HIF-1α is degraded by the HIF prolyl hydroxylase under normoxic conditions. We focus this review on the links between the activated Wnt/β-catenin pathway and the mechanisms underlying vasculogenesis and angiogenesis through HIF-1α under normoxic conditions in gliomas. Wnt-induced epidermal growth factor receptor/phosphatidylinositol 3-kinase (PI3K)/Akt signaling, Wnt-induced signal transducers and activators of transcription 3 (STAT3) signaling, and Wnt/β-catenin target gene transduction (c-Myc) can activate HIF-1α in a hypoxia-independent manner. The PI3K/Akt/mammalian target of rapamycin pathway activates HIF-1α through eukaryotic translation initiation factor 4E-binding protein 1 and STAT3. The β-catenin/T-cell factor 4 complex directly binds to STAT3 and activates HIF-1α, which up-regulates the Wnt/β-catenin target genes cyclin D1 and c-Myc in a positive feedback loop. Phosphorylated STAT3 by interleukin-6 or leukemia inhibitory factor activates HIF-1α even under normoxic conditions. The activation of the Wnt/β-catenin pathway induces, via the Wnt target genes c-Myc and cyclin D1 or via HIF-1α, gene transactivation encoding aerobic glycolysis enzymes, such as glucose transporter, hexokinase 2, pyruvate kinase M2, pyruvate dehydrogenase kinase 1 and lactate dehydrogenase-A, leading to lactate production, as the primary alternative of ATP, at all oxygen levels, even in normoxic conditions. Lactate released by glioma cells via the monocarboxylate lactate transporter-1 up-regulated by HIF-1α and lactate anion activates HIF-1α in normoxic endothelial cells by inhibiting HIF-1α prolyl hydroxylation and preventing HIF labeling by the von Hippel-Lindau protein. Increased lactate with acid environment and HIF-1α overexpression induce the vascular endothelial growth factor (VEGF) pathway of vasculogenesis and angiogenesis under normoxic conditions. Hypoxia and acidic pH have no synergistic effect on VEGF transcription.
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Affiliation(s)
- Alexandre Vallée
- Experimental and Clinical Neurosciences Laboratory, INSERM U1084, University of Poitiers, 11 Boulevard Marie et Pierre Curie, F-86000 Poitiers, France
| | - Rémy Guillevin
- DACTIM, UMR CNRS 7348, Université de Poitiers et CHU de Poitiers, F-86000 Poitiers, France
| | - Jean-Noël Vallée
- Laboratoire de Mathématiques et Applications (LMA), UMR CNRS 7348, University of Poitiers, F-86000 Poitiers, France
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18
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Wu X, Yu J, Yan J, Dai J, Si L, Chi Z, Sheng X, Cui C, Ma M, Tang H, Xu T, Yu H, Kong Y, Guo J. PI3K/AKT/mTOR pathway inhibitors inhibit the growth of melanoma cells with mTOR H2189Y mutations in vitro. Cancer Biol Ther 2018; 19:584-589. [PMID: 29708815 DOI: 10.1080/15384047.2018.1435221] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
mTOR is an important therapeutic target in many types of cancers. In melanoma, the mTOR nonsynonymous mutation rate is up to 10.4%. However, mTOR inhibitors have shown limited effects in clinical trials of melanoma. Because mTOR mutations are distributed, not selecting patients with specific mTOR mutations may be the main reason for therapeutic failures. Our previous research found that mutations in the mTOR P2213S and S2215Y kinase domains resulted in gain-of-function and were sensitive to specific inhibitors. The purpose of this study was to test the effect of heterozygous/homozygous H2189Y mutations on downstream pathways and sensitivity to inhibitors. mTOR kinase activity was analyzed by western blot and a K-LISA™ mTOR activity kit. The sensitivity of melanoma cells to inhibitors was tested by a proliferation assay. The expression of downstream pathway proteins was also analyzed by western blot. The results showed that heterozygous/homozygous H2189Y mutations were gain-of-function. The heterozygous H2189Y mutation was sensitive to the AKT inhibitor, AZD5363, and the phosphoinositide 3-kinase inhibitor, LY294002. The homozygous H2189Y mutation was sensitive to the mTOR inhibitor, everolimus, and the AKT inhibitors AZD5363 and MK-2206 2HCL,and the phosphoinositide 3-kinase inhibitor, LY294002. These results indicated that homozygous mutations in the kinase domain have a greater effect on protein function than heterozygous mutations. The mTOR kinase domain may play an important role in mTOR kinase activity and may be the target of selective inhibitors. Our study can facilitate the selection of appropriate inhibitors for patients in clinical trials.
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Affiliation(s)
- Xiaowen Wu
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Jiayi Yu
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Junya Yan
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Jie Dai
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Lu Si
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Zhihong Chi
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Xinan Sheng
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Chuanliang Cui
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Meng Ma
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Huan Tang
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Tianxiao Xu
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Huan Yu
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Yan Kong
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
| | - Jun Guo
- a Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Renal Cancer and Melanoma , Peking University Cancer Hospital & Institute , Beijing , China
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19
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De Cicco M, Kiss L, Dames SA. NMR analysis of the backbone dynamics of the small GTPase Rheb and its interaction with the regulatory protein FKBP38. FEBS Lett 2017; 592:130-146. [PMID: 29194576 DOI: 10.1002/1873-3468.12925] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 10/06/2017] [Accepted: 11/17/2017] [Indexed: 12/19/2022]
Abstract
Ras homolog enriched in brain (Rheb) is a small GTPase that regulates mammalian/mechanistic target of rapamycin complex 1 (mTORC1) and, thereby, cell growth and metabolism. Here we show that cycling between the inactive GDP- and the active GTP-bound state modulates the backbone dynamics of a C-terminal truncated form, RhebΔCT, which is suggested to influence its interactions. We further investigated the interactions between RhebΔCT and the proposed Rheb-binding domain of the regulatory protein FKBP38. The observed weak interactions with the GTP-analogue- (GppNHp-) but not the GDP-bound state, appear to accelerate the GDP to GTP exchange, but only very weakly compared to a genuine GEF. Thus, FKBP38 is most likely not a GEF but a Rheb effector that may function in membrane targeting of Rheb.
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Affiliation(s)
- Maristella De Cicco
- Technische Universität München, Department of Chemistry, Biomolecular NMR Spectroscopy, Garching, Germany
| | - Leo Kiss
- Technische Universität München, Department of Chemistry, Biomolecular NMR Spectroscopy, Garching, Germany
| | - Sonja A Dames
- Technische Universität München, Department of Chemistry, Biomolecular NMR Spectroscopy, Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg, Germany
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20
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Kim HJ, Byun HJ, Park MK, Kim EJ, Kang GJ, Lee CH. Novel involvement of RhebL1 in sphingosylphosphorylcholine-induced keratin phosphorylation and reorganization: Binding to and activation of AKT1. Oncotarget 2017; 8:20851-20864. [PMID: 28209923 PMCID: PMC5400551 DOI: 10.18632/oncotarget.15364] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 02/06/2017] [Indexed: 11/25/2022] Open
Abstract
Sphingosylphosphorylcholine induces keratin phosphorylation and reorganization, and increases viscoelasticity of metastatic cancer cells such as PANC-1 cells. However, the mechanism involved in sphingosylphosphorylcholine-induced keratin phosphorylation and reorganization is largely unknown. Sphingosylphosphorylcholine dose- and time-dependently induces the expression of RhebL1. The involvement of RhebL1 in sphingosylphosphorylcholine-induced events including keratin 8 (K8) phosphorylation, reorganization, migration and invasion was examined. Gene silencing of RhebL1 suppressed the sphingosylphosphorylcholine-induced events and overexpression of RhebL1 enhanced those events even without sphingosylphosphorylcholine treatment. We examined whether the G protein function of RhebL1 induces K8 phosphorylation using constitutively active RhebL1Q64L and dominant negative RhebL1D60K. G protein activity of RhebL1 is involved in sphingosylphosphorylcholine-induced K8 phosphorylation. We found that RhebL1 binds and activates AKT1. G protein activity of RhebL1 is involved in the binding and activation of AKT1. MK2206 (AKT inhibitor) and gene silencing of AKT1 inhibited the sphingosylphosphorylcholine-induced events, whereas overexpression of activated-AKT1 induced K8 phosphorylation, reorganization, migration and invasion even without sphingosylphosphorylcholine treatment. The collective results indicate that RhebL1 is involved in sphingosylphosphorylcholine-induced events in A549 lung cancer cells via binding to AKT1 leading to activation of it. These results suggest that suppression of RhebL1 or inhibition of RhebL1′s binding to AKT1 might be a novel way that prevents changes in the physical properties of metastatic cancer cells.
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Affiliation(s)
- Hyun Ji Kim
- College of Pharmacy, Dongguk University, Seoul 100-715, Republic of Korea
| | - Hyun Jung Byun
- College of Pharmacy, Dongguk University, Seoul 100-715, Republic of Korea
| | - Mi Kyung Park
- College of Pharmacy, Dongguk University, Seoul 100-715, Republic of Korea
| | - Eun Ji Kim
- College of Pharmacy, Dongguk University, Seoul 100-715, Republic of Korea
| | - Gyeoung Jin Kang
- College of Pharmacy, Dongguk University, Seoul 100-715, Republic of Korea
| | - Chang Hoon Lee
- College of Pharmacy, Dongguk University, Seoul 100-715, Republic of Korea
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21
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Potheraveedu VN, Schöpel M, Stoll R, Heumann R. Rheb in neuronal degeneration, regeneration, and connectivity. Biol Chem 2017; 398:589-606. [PMID: 28212107 DOI: 10.1515/hsz-2016-0312] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2016] [Accepted: 02/02/2017] [Indexed: 01/31/2023]
Abstract
The small GTPase Rheb was originally detected as an immediate early response protein whose expression was induced by NMDA-dependent synaptic activity in the brain. Rheb's activity is highly regulated by its GTPase activating protein (GAP), the tuberous sclerosis complex protein, which stimulates the conversion from the active, GTP-loaded into the inactive, GDP-loaded conformation. Rheb has been established as an evolutionarily conserved molecular switch protein regulating cellular growth, cell volume, cell cycle, autophagy, and amino acid uptake. The subcellular localization of Rheb and its interacting proteins critically regulate its activity and function. In stem cells, constitutive activation of Rheb enhances differentiation at the expense of self-renewal partially explaining the adverse effects of deregulated Rheb in the mammalian brain. In the context of various cellular stress conditions such as oxidative stress, ER-stress, death factor signaling, and cellular aging, Rheb activation surprisingly enhances rather than prevents cellular degeneration. This review addresses cell type- and cell state-specific function(s) of Rheb and mainly focuses on neurons and their surrounding glial cells. Mechanisms will be discussed in the context of therapy that interferes with Rheb's activity using the antibiotic rapamycin or low molecular weight compounds.
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Affiliation(s)
- Veena Nambiar Potheraveedu
- Molecular Neurobiochemistry, Faculty of Chemistry and Biochemistry, Ruhr University of Bochum, Universitätstr. 150, D-44780 Bochum
| | - Miriam Schöpel
- Biomolecular NMR, Ruhr University of Bochum, D-44780 Bochum
| | - Raphael Stoll
- Biomolecular NMR, Ruhr University of Bochum, D-44780 Bochum
| | - Rolf Heumann
- Molecular Neurobiochemistry, Faculty of Chemistry and Biochemistry, Ruhr University of Bochum, Universitätstr. 150, D-44780 Bochum
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22
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Schöpel M, Potheraveedu VN, Al-Harthy T, Abdel-Jalil R, Heumann R, Stoll R. The small GTPases Ras and Rheb studied by multidimensional NMR spectroscopy: structure and function. Biol Chem 2017; 398:577-588. [DOI: 10.1515/hsz-2016-0276] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 01/23/2017] [Indexed: 12/15/2022]
Abstract
Abstract
Ras GTPases are key players in cellular signalling because they act as binary switches. These states manifest through toggling between an active (GTP-loaded) and an inactive (GDP-loaded) form. The hydrolysis and replenishing of GTP is controlled by two additional protein classes: GAP (GTPase-activating)- and GEF (Guanine nucleotide exchange factors)-proteins. The complex interplay of the proteins is known as the GTPase-cycle. Several point mutations of the Ras protein deregulate this cycle. Mutations in Ras are associated with up to one-third of human cancers. The three isoforms of Ras (H, N, K) exhibit high sequence similarity and mainly differ in a region called HVR (hypervariable region). The HVR governs the differential action and cellular distribution of the three isoforms. Rheb is a Ras-like GTPase that is conserved from yeast to mammals. Rheb is mainly involved in activation of cell growth through stimulation of mTORC1 activity. In this review, we summarise multidimensional NMR studies on Rheb and Ras carried out to characterise their structure-function relationship and explain how the activity of these small GTPases can be modulated by low molecular weight compounds. These might help to design GTPase-selective antagonists for treatment of cancer and brain disease.
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Discrete signaling mechanisms of mTORC1 and mTORC2: Connected yet apart in cellular and molecular aspects. Adv Biol Regul 2017; 64:39-48. [PMID: 28189457 DOI: 10.1016/j.jbior.2016.12.001] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 12/23/2016] [Accepted: 12/23/2016] [Indexed: 12/19/2022]
Abstract
Activation of PI3K/Akt/mTOR (mechanistic target of rapamycin) signaling cascade has been shown in tumorigenesis of numerous malignancies including glioblastoma (GB). This signaling cascade is frequently upregulated due to loss of the tumor suppressor PTEN, a phosphatase that functions antagonistically to PI3K. mTOR regulates cell growth, motility, and metabolism by forming two multiprotein complexes, mTORC1 and mTORC2, which are composed of special binding partners. These complexes are sensitive to distinct stimuli. mTORC1 is sensitive to nutrients and mTORC2 is regulated via PI3K and growth factor signaling. mTORC1 regulates protein synthesis and cell growth through downstream molecules: 4E-BP1 (also called EIF4E-BP1) and S6K. Also, mTORC2 is responsive to growth factor signaling by phosphorylating the C-terminal hydrophobic motif of some AGC kinases like Akt and SGK. mTORC2 plays a crucial role in maintenance of normal and cancer cells through its association with ribosomes, and is involved in cellular metabolic regulation. Both complexes control each other as Akt regulates PRAS40 phosphorylation, which disinhibits mTORC1 activity, while S6K regulates Sin1 to modulate mTORC2 activity. Another significant component of mTORC2 is Sin1, which is crucial for mTORC2 complex formation and function. Allosteric inhibitors of mTOR, rapamycin and rapalogs, have essentially been ineffective in clinical trials of patients with GB due to their incomplete inhibition of mTORC1 or unexpected activation of mTOR via the loss of negative feedback loops. Novel ATP binding inhibitors of mTORC1 and mTORC2 suppress mTORC1 activity completely by total dephosphorylation of its downstream substrate pS6KSer235/236, while effectively suppressing mTORC2 activity, as demonstrated by complete dephosphorylation of pAKTSer473. Furthermore, proliferation and self-renewal of GB cancer stem cells are effectively targetable by these novel mTORC1 and mTORC2 inhibitors. Therefore, the effectiveness of inhibitors of mTOR complexes can be estimated by their ability to suppress both mTORC1 and 2 and their ability to impede both cell proliferation and migration.
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Wang X, Li GJ, Hu HX, Ma C, Ma DH, Liu XL, Jiang XM. Cerebral mTOR signal and pro-inflammatory cytokines in Alzheimer's disease rats. Transl Neurosci 2016; 7:151-157. [PMID: 28123835 PMCID: PMC5234524 DOI: 10.1515/tnsci-2016-0022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 11/17/2016] [Indexed: 01/05/2023] Open
Abstract
As a part of Alzheimer’s disease (AD) development the mammalian target of rapamycin
(mTOR) has been reported to play a crucial role in regulating cognition and can be used as a
neuronal marker. Neuro-inflammation is also a cause of the pathophysiological process in AD.
Thus, we examined the protein expression levels of mTOR and its downstream pathways as well as
pro-inflammatory cytokines (PICs) in the brain of AD rats. We further examined the effects of
blocking mTOR on PICs, namely IL-1β, IL-6 and TNF-α. Our results showed that the
protein expression of p-mTOR, mTOR-mediated phosphorylation of 4E-binding protein 4 (4E-BP1)
and p70 ribosomal S6 protein kinase 1 (S6K1) pathways were amplified in the hippocampus of AD
rats compared with controls. Blocking mTOR by using rapamycin selectively enhanced activities
of IL-6 and TNF-α signaling pathways, which was accompanied with an increase of
Caspase-3, indicating cellular apoptosis and worsened learning performance. In conclusion, our
data for the first time revealed specific signaling pathways engaged in the development of AD,
including a regulatory role by the activation of mTOR in PIC mechanisms. Stimulation of mTOR is
likely to play a beneficial role in modulating neurological deficits in AD.Targeting one or
more of these signaling molecules may present with new opportunities for treatment and clinical
management of AD
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Affiliation(s)
- Xu Wang
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University Changchun, Jilin 130021, PR. China
| | - Guang-Jian Li
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University Changchun, Jilin 130021, PR. China
| | - Hai-Xia Hu
- Department of Emergency Medicine, The First Hospital of Jilin University Changchun, Jilin 130021, PR. China
| | - Chi Ma
- Department of Brain Tumor Surgery, The First Hospital of Jilin University Changchun, Jilin 130021, P.R. China
| | - Di-Hui Ma
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University Changchun, Jilin 130021, PR. China
| | - Xiao-Liang Liu
- Department of Emergency Medicine, The First Hospital of Jilin University Changchun, Jilin 130021, PR. China
| | - Xiao-Ming Jiang
- Department of Emergency Medicine, The First Hospital of Jilin University Changchun, Jilin 130021, PR. China
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Taneike M, Nishida K, Omiya S, Zarrinpashneh E, Misaka T, Kitazume-Taneike R, Austin R, Takaoka M, Yamaguchi O, Gambello MJ, Shah AM, Otsu K. mTOR Hyperactivation by Ablation of Tuberous Sclerosis Complex 2 in the Mouse Heart Induces Cardiac Dysfunction with the Increased Number of Small Mitochondria Mediated through the Down-Regulation of Autophagy. PLoS One 2016; 11:e0152628. [PMID: 27023784 PMCID: PMC4811538 DOI: 10.1371/journal.pone.0152628] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 03/10/2016] [Indexed: 11/19/2022] Open
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) is a key regulator of cell growth, proliferation and metabolism. mTORC1 regulates protein synthesis positively and autophagy negatively. Autophagy is a major system to manage bulk degradation and recycling of cytoplasmic components and organelles. Tuberous sclerosis complex (TSC) 1 and 2 form a heterodimeric complex and inactivate Ras homolog enriched in brain, resulting in inhibition of mTORC1. Here, we investigated the effects of hyperactivation of mTORC1 on cardiac function and structure using cardiac-specific TSC2-deficient (TSC2-/-) mice. TSC2-/- mice were born normally at the expected Mendelian ratio. However, the median life span of TSC2-/- mice was approximately 10 months and significantly shorter than that of control mice. TSC2-/- mice showed cardiac dysfunction and cardiomyocyte hypertrophy without considerable fibrosis, cell infiltration or apoptotic cardiomyocyte death. Ultrastructural analysis of TSC2-/- hearts revealed misalignment, aggregation and a decrease in the size and an increase in the number of mitochondria, but the mitochondrial function was maintained. Autophagic flux was inhibited, while the phosphorylation level of S6 or eukaryotic initiation factor 4E -binding protein 1, downstream of mTORC1, was increased. The upregulation of autophagic flux by trehalose treatment attenuated the cardiac phenotypes such as cardiac dysfunction and structural abnormalities of mitochondria in TSC2-/- hearts. The results suggest that autophagy via the TSC2-mTORC1 signaling pathway plays an important role in maintenance of cardiac function and mitochondrial quantity and size in the heart and could be a therapeutic target to maintain mitochondrial homeostasis in failing hearts.
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Affiliation(s)
- Manabu Taneike
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | - Kazuhiko Nishida
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | - Shigemiki Omiya
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | - Elham Zarrinpashneh
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | - Tomofumi Misaka
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | - Rika Kitazume-Taneike
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | - Ruth Austin
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | - Minoru Takaoka
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | - Osamu Yamaguchi
- Department of Cardiovascular Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan
| | - Michael J. Gambello
- Division of Medical Genetics, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Ajay M. Shah
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
| | - Kinya Otsu
- Cardiovascular Division, King’s College London British Heart Foundation Centre of Excellence, London, United Kingdom
- * E-mail:
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De Cicco M, Rahim MSA, Dames SA. Regulation of the Target of Rapamycin and Other Phosphatidylinositol 3-Kinase-Related Kinases by Membrane Targeting. MEMBRANES 2015; 5:553-75. [PMID: 26426064 PMCID: PMC4703999 DOI: 10.3390/membranes5040553] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 09/24/2015] [Indexed: 01/05/2023]
Abstract
Phosphatidylinositol 3-kinase-related kinases (PIKKs) play vital roles in the regulation of cell growth, proliferation, survival, and consequently metabolism, as well as in the cellular response to stresses such as ionizing radiation or redox changes. In humans six family members are known to date, namely mammalian/mechanistic target of rapamycin (mTOR), ataxia-telangiectasia mutated (ATM), ataxia- and Rad3-related (ATR), DNA-dependent protein kinase catalytic subunit (DNA-PKcs), suppressor of morphogenesis in genitalia-1 (SMG-1), and transformation/transcription domain-associated protein (TRRAP). All fulfill rather diverse functions and most of them have been detected in different cellular compartments including various cellular membranes. It has been suggested that the regulation of the localization of signaling proteins allows for generating a locally specific output. Moreover, spatial partitioning is expected to improve the reliability of biochemical signaling. Since these assumptions may also be true for the regulation of PIKK function, the current knowledge about the regulation of the localization of PIKKs at different cellular (membrane) compartments by a network of interactions is reviewed. Membrane targeting can involve direct lipid-/membrane interactions as well as interactions with membrane-anchored regulatory proteins, such as, for example, small GTPases, or a combination of both.
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Affiliation(s)
- Maristella De Cicco
- Department of Chemistry, Biomolecular NMR Spectroscopy, Technische Universität München, Lichtenbergstr. 4, Garching 85747, Germany.
| | - Munirah S Abd Rahim
- Department of Chemistry, Biomolecular NMR Spectroscopy, Technische Universität München, Lichtenbergstr. 4, Garching 85747, Germany.
| | - Sonja A Dames
- Department of Chemistry, Biomolecular NMR Spectroscopy, Technische Universität München, Lichtenbergstr. 4, Garching 85747, Germany.
- Institute of Structural Biology, Helmholtz Zentrum München, Ingolstädter Landstr. 1, Neuherberg 85764, Germany.
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Altman MK, Alshamrani AA, Jia W, Nguyen HT, Fambrough JM, Tran SK, Patel MB, Hoseinzadeh P, Beedle AM, Murph MM. Suppression of the GTPase-activating protein RGS10 increases Rheb-GTP and mTOR signaling in ovarian cancer cells. Cancer Lett 2015; 369:175-83. [PMID: 26319900 DOI: 10.1016/j.canlet.2015.08.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 08/14/2015] [Accepted: 08/17/2015] [Indexed: 12/15/2022]
Abstract
The regulator of G protein signaling 10 (RGS10) protein is a GTPase activating protein that accelerates the hydrolysis of GTP and therefore canonically inactivates G proteins, ultimately terminating signaling. Rheb is a small GTPase protein that shuttles between its GDP- and GTP-bound forms to activate mTOR. Since RGS10 suppression augments ovarian cancer cell viability, we sought to elucidate the molecular mechanism. Following RGS10 suppression in serum-free conditions, phosphorylation of mTOR, the eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), p70S6K and S6 Ribosomal Protein appear. Furthermore, suppressing RGS10 increases activated Rheb, suggesting RGS10 antagonizes mTOR signaling via the small G-protein. The effects of RGS10 suppression are enhanced after stimulating cells with the growth factor, lysophosphatidic acid, and reduced with mTOR inhibitors, temsirolimus and INK-128. Suppression of RGS10 leads to an increase in cell proliferation, even in the presence of etoposide. In summary, the RGS10 suppression increases Rheb-GTP and mTOR signaling in ovarian cancer cells. Our results suggest that RGS10 could serve in a novel, and previously unknown, role by accelerating the hydrolysis of GTP from Rheb in ovarian cancer cells.
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Affiliation(s)
- Molly K Altman
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA
| | - Ali A Alshamrani
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA
| | - Wei Jia
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA
| | - Ha T Nguyen
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA
| | - Jada M Fambrough
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA
| | - Sterling K Tran
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA
| | - Mihir B Patel
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA
| | - Pooya Hoseinzadeh
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA
| | - Aaron M Beedle
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA
| | - Mandi M Murph
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, 240 W. Green Street, Athens, GA 30602, USA.
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Dibble CC, Cantley LC. Regulation of mTORC1 by PI3K signaling. Trends Cell Biol 2015; 25:545-55. [PMID: 26159692 DOI: 10.1016/j.tcb.2015.06.002] [Citation(s) in RCA: 559] [Impact Index Per Article: 62.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 06/08/2015] [Accepted: 06/08/2015] [Indexed: 11/29/2022]
Abstract
The class I phosphoinositide 3-kinase (PI3K)-mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) signaling network directs cellular metabolism and growth. Activation of mTORC1 [composed of mTOR, regulatory-associated protein of mTOR (Raptor), mammalian lethal with SEC13 protein 8(mLST8), 40-kDa proline-rich Akt substrate (PRAS40), and DEP domain-containing mTOR-interacting protein (DEPTOR)] depends on the Ras-related GTPases (Rags) and Ras homolog enriched in brain (Rheb) GTPase and requires signals from amino acids, glucose, oxygen, energy (ATP), and growth factors (including cytokines and hormones such as insulin). Here we discuss the signal transduction mechanisms through which growth factor-responsive PI3K signaling activates mTORC1. We focus on how PI3K-dependent activation of Akt and spatial regulation of the tuberous sclerosis complex (TSC) complex (TSC complex) [composed of TSC1, TSC2, and Tre2-Bub2-Cdc16-1 domain family member 7 (TBC1D7)] switches on Rheb at the lysosome, where mTORC1 is activated. Integration of PI3K- and amino acid-dependent signals upstream of mTORC1 at the lysosome is detailed in a working model. A coherent understanding of the PI3K-mTORC1 network is imperative as its dysregulation has been implicated in diverse pathologies including cancer, diabetes, autism, and aging.
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Affiliation(s)
- Christian C Dibble
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Lewis C Cantley
- Meyer Cancer Center, Department of Medicine, Weill Cornell Medical College, New York, NY 10065, USA.
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Ho JCS, Nadeem A, Rydström A, Puthia M, Svanborg C. Targeting of nucleotide-binding proteins by HAMLET--a conserved tumor cell death mechanism. Oncogene 2015; 35:897-907. [PMID: 26028028 DOI: 10.1038/onc.2015.144] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/24/2015] [Accepted: 03/29/2015] [Indexed: 12/20/2022]
Abstract
HAMLET (Human Alpha-lactalbumin Made LEthal to Tumor cells) kills tumor cells broadly suggesting that conserved survival pathways are perturbed. We now identify nucleotide-binding proteins as HAMLET binding partners, accounting for about 35% of all HAMLET targets in a protein microarray comprising 8000 human proteins. Target kinases were present in all branches of the Kinome tree, including 26 tyrosine kinases, 10 tyrosine kinase-like kinases, 13 homologs of yeast sterile kinases, 4 casein kinase 1 kinases, 15 containing PKA, PKG, PKC family kinases, 15 calcium/calmodulin-dependent protein kinase kinases and 13 kinases from CDK, MAPK, GSK3, CLK families. HAMLET acted as a broad kinase inhibitor in vitro, as defined in a screen of 347 wild-type, 93 mutant, 19 atypical and 17 lipid kinases. Inhibition of phosphorylation was also detected in extracts from HAMLET-treated lung carcinoma cells. In addition, HAMLET recognized 24 Ras family proteins and bound to Ras, RasL11B and Rap1B on the cytoplasmic face of the plasma membrane. Direct cellular interactions between HAMLET and activated Ras family members including Braf were confirmed by co-immunoprecipitation. As a consequence, oncogenic Ras and Braf activity was inhibited and HAMLET and Braf inhibitors synergistically increased tumor cell death in response to HAMLET. Unlike most small molecule kinase inhibitors, HAMLET showed selectivity for tumor cells in vitro and in vivo. The results identify nucleotide-binding proteins as HAMLET targets and suggest that dysregulation of the ATPase/kinase/GTPase machinery contributes to cell death, following the initial, selective recognition of HAMLET by tumor cells. The findings thus provide a molecular basis for the conserved tumoricidal effect of HAMLET, through dysregulation of kinases and oncogenic GTPases, to which tumor cells are addicted.
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Affiliation(s)
- J C S Ho
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - A Nadeem
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - A Rydström
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - M Puthia
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
| | - C Svanborg
- Department of Microbiology, Immunology and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Lund, Sweden
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Goorden SMI, Abs E, Bruinsma CF, Riemslagh FW, van Woerden GM, Elgersma Y. Intact neuronal function in Rheb1 mutant mice: implications for TORC1-based treatments. Hum Mol Genet 2015; 24:3390-8. [PMID: 25759467 DOI: 10.1093/hmg/ddv087] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2004] [Accepted: 03/04/2015] [Indexed: 12/16/2022] Open
Abstract
Target of rapamycin complex 1 (TORC1) is an important regulator of neuronal function. However, whereas a modest activation of the TORC1 signaling pathway has been shown to affect synaptic plasticity, learning and memory, the effect of TORC1 hypo-activation is less clear. This knowledge is particularly important since TORC1 inhibitors may hold great promise for treating a variety of disorders, including developmental disorders, aging-related disorders, epilepsy and cancer. Such treatments are likely to be long lasting and could involve treating young children. Hence, it is pivotal that the effects of sustained TORC1 inhibition on brain development and cognitive function are determined. Here, we made use of constitutive and conditional Rheb1 mutant mice to study the effect of prolonged and specific reduction in the TORC1 pathway. We show that Rheb1 mutant mice show up to 75% reduction in TORC1 signaling, but develop normally and show intact synaptic plasticity and hippocampus-dependent learning and memory. We discuss our findings in light of current literature in which the effect of pharmacological inhibition of TORC1 is studied in the context of synaptic plasticity and learning. We conclude that in contrast to TORC1 hyper-activity, cognitive function is not very sensitive to sustained and specific down-regulation of TORC1 activity.
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Affiliation(s)
- Susanna M I Goorden
- Department of Neuroscience and ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus University Medical Center, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Elisabeth Abs
- Department of Neuroscience and ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus University Medical Center, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Caroline F Bruinsma
- Department of Neuroscience and ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus University Medical Center, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Fréderike W Riemslagh
- Department of Neuroscience and ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus University Medical Center, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Geeske M van Woerden
- Department of Neuroscience and ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus University Medical Center, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Ype Elgersma
- Department of Neuroscience and ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus University Medical Center, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
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DHH-RHEBL1 fusion transcript: a novel recurrent feature in the new landscape of pediatric CBFA2T3-GLIS2-positive acute myeloid leukemia. Oncotarget 2014; 4:1712-20. [PMID: 24127550 PMCID: PMC3858557 DOI: 10.18632/oncotarget.1280] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Childhood Acute Myeloid Leukemia (AML) is a clinically and genetically heterogeneous malignant disease. Despite improvements in outcome over the past decades, the current survival rate still is approximately 60-70%. Cytogenetic, recurrent genetic abnormalities and early response to induction treatment are the main factors predicting clinical outcome. While the majority of children carry recurrent chromosomal translocations, 20% of patients do not show any recognizable cytogenetic alteration and are defined to have cytogenetically normal AML (CN-AML). This subset of patients is characterized by a significant heterogeneity in clinical outcome, which is influenced by factors only recently started to be identified. In this respect, genome-wide analyses have been used with the aim of defining the full array of genetic lesions in CN-AML. Recently, through whole-transcriptome massively parallel sequencing of seven cases of pediatric CN-AML, we identified a novel recurrent CBFA2T3-GLIS2 fusion, predicting poorer outcome. However, since the expression of CBFA2T3-GLIS2 fusion in mice is not sufficient for leukemogenesis, we speculated that further unknown abnormalities could contribute to both cancer transformation and response to treatment. Thus, we analyzed, by whole-transcriptome sequencing, 4 CBFA2T3-GLIS2-positive patients, as well as 4 CN-AML patients. We identified a new fusion transcript in the CBFA2T3-GLIS2 -positive patients, involving Desert Hedgehog (DHH), a member of Hedgehog family, and Ras Homologue Enrich in Brain Like 1 (RHEBL1), a gene coding for a small GTPase of the Ras family. Through the screening of a validation cohort of 55 additional pediatric AML patients, we globally detected DHH-RHEBL1 fusion in 8 out of 20 (40%) CBFA2T3-GLIS2- rearranged patients. Gene expression analysis performed on RNA-seq data revealed that DHH-RHEBL1 –positive patients exhibited a specific signature. These 8 patients had an 8-year overall survival worse than that of the remaining 12 CBFA2T3-GLIS2- rearranged patients not harboring DHH-RHEBL1 fusion (25% vs 55%, respectively, P =0.1). Taken together, these findings are unprecedented and indicate that the DHH-RHEBL1 fusion transcript is a novel recurrent feature in the changing landscape of CBFA2T3-GLIS2 -positive childhood AML. Moreover, it could be instrumental in the identification of a subgroup of CBFA2T3-GLIS2 -positive patients with a very poor outcome.
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Baker MD, Ezzati M, Aloisio GM, Tarnawa ED, Cuevas I, Nakada Y, Castrillon DH. The small GTPase Rheb is required for spermatogenesis but not oogenesis. Reproduction 2014; 147:615-25. [PMID: 24713393 DOI: 10.1530/rep-13-0304] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The process of germ cell development is under the tight control of various signaling pathways, among which the PI3K-Akt-mTOR pathway is of critical importance. Previous studies have demonstrated sex-specific roles for several components of this pathway. In the current study, we aimed to evaluate the role of Rheb, a member of the small GTPase superfamily and a critical component for mTORC1 activation, in male and female gametogenesis. The function of Rheb in development and the nervous system has been extensively studied, but little is known about its role in the germ line. We have exploited genetic approaches in the mouse to study the role of Rheb in the germ line and have identified an essential role in spermatogenesis. Conditional knockout (cKO) of Rheb in the male germ line resulted in severe oligoasthenoteratozoospermia and male sterility. More detailed phenotypic analyses uncovered an age-dependent meiotic progression defect combined with subsequent abnormalities in spermiogenesis as evidenced by abnormal sperm morphology. In the female, however, germ-cell specific inactivation of Rheb was not associated with any discernible abnormality; these cKO mice were fertile with morphologically unremarkable ovaries, normal primordial follicle formation, and subsequent follicle maturation. The absence of an abnormal ovarian phenotype is striking given previous studies demonstrating a critical role for the mTORC1 pathway in the maintenance of primordial follicle pool. In conclusion, our findings demonstrate an essential role of Rheb in diverse aspects of spermatogenesis but suggest the existence of functionally redundant factors that can compensate for Rheb deficiency within oocytes.
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Guan P, Wang N. Mammalian target of rapamycin coordinates iron metabolism with iron-sulfur cluster assembly enzyme and tristetraprolin. Nutrition 2014; 30:968-74. [PMID: 24976419 DOI: 10.1016/j.nut.2013.12.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 12/13/2013] [Accepted: 12/15/2013] [Indexed: 01/07/2023]
Abstract
Both iron deficiency and excess are relatively common health concerns. Maintaining the body's levels of iron within precise boundaries is critical for cell functions. However, the difference between iron deficiency and overload is often a question of a scant few milligrams of iron. The mammalian target of rapamycin (mTOR), an atypical Ser/Thr protein kinase, is attracting significant amounts of interest due to its recently described role in iron homeostasis. Despite extensive study, a complete understanding of mTOR function has remained elusive. mTOR can form two multiprotein complexes that consist of mTOR complex 1 (mTORC1) and mTOR complex 2. Recent advances clearly demonstrate that mTORC1 can phosphorylate iron-sulfur cluster assembly enzyme ISCU and affect iron-sulfur clusters assembly. Moreover, mTOR is reported to control iron metabolism through modulation of tristetraprolin expression. It is now well appreciated that the hormonal hepcidin-ferroportin system and the cellular iron-responsive element/iron-regulatory protein regulatory network play important regulatory roles for systemic iron metabolism. Sustained ISCU protein levels enhanced by mTORC1 can inhibit iron-responsive element and iron-regulatory protein binding activities. In this study, hepcidin gene and protein expression in the livers of tristetraprolin knockout mice were dramatically reduced. Here, we highlight and summarize the current understanding of how mTOR pathways serve to modulate iron metabolism and homeostasis as the third iron-regulatory system.
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Affiliation(s)
- Peng Guan
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, Hebei Normal University, Hebei Province, China
| | - Na Wang
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, Hebei Normal University, Hebei Province, China; School of Basic Medical Sciences, Hebei University of Traditional Chinese Medicine, Hebei Province, China.
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Groenewoud MJ, Goorden SMI, Kassies J, Pellis-van Berkel W, Lamb RF, Elgersma Y, Zwartkruis FJT. Mammalian target of rapamycin complex I (mTORC1) activity in ras homologue enriched in brain (Rheb)-deficient mouse embryonic fibroblasts. PLoS One 2013; 8:e81649. [PMID: 24303063 PMCID: PMC3841147 DOI: 10.1371/journal.pone.0081649] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 10/15/2013] [Indexed: 11/19/2022] Open
Abstract
The Ras-like GTPase Rheb has been identified as a crucial activator of mTORC1. Activation most likely requires a direct interaction between Rheb and mTOR, but the exact mechanism remains unclear. Using a panel of Rheb-deficient mouse embryonic fibroblasts (MEFs), we show that Rheb is indeed essential for the rapid increase of mTORC1 activity following stimulation with insulin or amino acids. However, mTORC1 activity is less severely reduced in Rheb-deficient MEFs in the continuous presence of serum or upon stimulation with serum. This remaining mTORC1 activity is blocked by depleting the cells for amino acids or imposing energy stress. In addition, MEK inhibitors and the RSK-inhibitor BI-D1870 interfere in mTORC1 activity, suggesting that RSK acts as a bypass for Rheb in activating mTORC1. Finally, we show that this rapamycin-sensitive, Rheb-independent mTORC1 activity is important for cell cycle progression. In conclusion, whereas rapid adaptation in mTORC1 activity requires Rheb, a second Rheb-independent activation mechanism exists that contributes to cell cycle progression.
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Affiliation(s)
- Marlous J. Groenewoud
- Molecular Cancer Research, Centre for Biomedical Genetics and Cancer Genomics Centre, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Susan M. I. Goorden
- Department of Neuroscience, ENCORE expertise center for neuro-developmental disorders, Erasmus MC University Medical Center, Rotterdam, The Netherlands
| | - Jorien Kassies
- Molecular Cancer Research, Centre for Biomedical Genetics and Cancer Genomics Centre, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Wendy Pellis-van Berkel
- Molecular Cancer Research, Centre for Biomedical Genetics and Cancer Genomics Centre, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Richard F. Lamb
- Department of Molecular and Clinical Cancer Medicine, University of Liverpool, Cancer Research UK Centre, Liverpool, United Kingdom
| | - Ype Elgersma
- Department of Neuroscience, ENCORE expertise center for neuro-developmental disorders, Erasmus MC University Medical Center, Rotterdam, The Netherlands
| | - Fried J. T. Zwartkruis
- Molecular Cancer Research, Centre for Biomedical Genetics and Cancer Genomics Centre, University Medical Center Utrecht, Utrecht, The Netherlands
- * E-mail:
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35
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Jhanwar-Uniyal M, Jeevan D, Neil J, Shannon C, Albert L, Murali R. Deconstructing mTOR complexes in regulation of Glioblastoma Multiforme and its stem cells. Adv Biol Regul 2013; 53:202-210. [PMID: 23231881 DOI: 10.1016/j.jbior.2012.10.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 10/03/2012] [Indexed: 06/01/2023]
Abstract
Atypical serine-threonine kinase, mTOR (mechanistic target of Rapamycin; originally coined "mammalian TOR"), exists in two distinct multi-protein complexes termed mTOR complex 1 (mTORC1) and 2 (mTORC2), that senses and integrates a variety of environmental signals to control organism growth and homeostasis via non-overlapping signaling pathways. mTOR belongs to the phosphoinositide 3-kinase (PI3-K)-related kinase family, and an aberrant activation of mTORC1 is a potential contributing factor in uncontrolled cell growth, proliferation, and survival of tumor cells via specific effects on cap-dependent translation initiation, as well as in a more sustained manner via advancing ribosome biogenesis. It is thereby shown to be deregulated in numerous pathological conditions including cancer, obesity, type 2 diabetes, and neurodegeneration. Notably, mTOR itself, or through its substrates, regulates stem cell differentiation and maintenance of plueropotency. mTORC2 has been linked to cytoskeletal reorganization and cell survival through Akt, and is crucial to many divergent physiological functions, which may include stem cell regulation.
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36
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Palaniappan M, Menon B, Menon KMJ. Stimulatory effect of insulin on theca-interstitial cell proliferation and cell cycle regulatory proteins through MTORC1 dependent pathway. Mol Cell Endocrinol 2013; 366:81-9. [PMID: 23261705 PMCID: PMC3552006 DOI: 10.1016/j.mce.2012.12.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Revised: 11/22/2012] [Accepted: 12/05/2012] [Indexed: 11/25/2022]
Abstract
The present study examined the effect of insulin-mediated activation of the mammalian target of rapamycin complex 1 (MTORC1) signaling network on the proliferation of primary culture of theca-interstitial (T-I) cells. Our results show that insulin treatment increased proliferation of the T-I cells through the MTORC1-dependent signaling pathway by increasing cell cycle regulatory proteins. Inhibition of ERK1/2 signaling caused partial reduction of insulin-induced phosphorylation of RPS6KB1 and RPS6 whereas inhibition of PI3-kinase signaling completely blocked the insulin response. Pharmacological inhibition of MTORC1 with rapamycin abrogated the insulin-induced phosphorylation of EIF4EBP1, RPS6KB1 and its downstream effector, RPS6. These results were further confirmed by demonstrating that knockdown of Mtor using siRNA reduced the insulin-stimulated MTORC1 signaling. Furthermore, insulin-stimulated T-I cell proliferation and the expression of cell cycle regulatory proteins CDK4, CCND3 and PCNA were also blocked by rapamycin. Taken together, the present studies show that insulin stimulates cell proliferation and cell cycle regulatory proteins in T-I cells via activation of the MTORC1 signaling pathway.
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Affiliation(s)
- Murugesan Palaniappan
- Department of Obstetrics and Gynecology, University of Michigan Medical School, Ann Arbor, MI 48109, United States
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37
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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] [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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Lee MN, Koh A, Park D, Jang JH, Kwak D, Jeon H, Kim J, Choi EJ, Jeong H, Suh PG, Ryu SH. Deacetylated αβ-tubulin acts as a positive regulator of Rheb GTPase through increasing its GTP-loading. Cell Signal 2012. [PMID: 23178303 DOI: 10.1016/j.cellsig.2012.11.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Ras homolog enriched in brain (Rheb) regulates diverse cellular functions by modulating its nucleotide-bound status. Although Rheb contains a high basal GTP level, the regulatory mechanism of Rheb is not well understood. In this study, we propose soluble αβ-tubulin acts as a constitutively active Rheb activator, which may explain the reason why Rheb has a high basal GTP levels. We found that soluble αβ-tubulin is a direct Rheb-binding protein and that its deacetylated form has a high binding affinity for Rheb. Modulation of both soluble and acetylated αβ-tubulin levels affects the level of GTP-bound Rheb. This occurs in the mitotic phase in which the level of acetylated αβ-tubulin is increased but that of GTP-bound Rheb is decreased. Constitutively active Rheb-overexpressing cells showed an abnormal mitotic progression, suggesting the deacetylated αβ-tubulin-mediated regulation of Rheb status may be important for proper mitotic progression. Taken together, we propose that deacetylated soluble αβ-tubulin is a novel type of positive regulator of Rheb and may play a role as a temporal regulator for Rheb during the cell cycle.
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Affiliation(s)
- Mi Nam Lee
- Division of Molecular and Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea
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The Mechanism of Autophagy Regulation and The Role of Autophagy in Alzheimer′s Disease*. PROG BIOCHEM BIOPHYS 2012. [DOI: 10.3724/sp.j.1206.2012.00363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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40
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Wang CY, Stapleton DS, Schueler KL, Rabaglia ME, Oler AT, Keller MP, Kendziorski CM, Broman KW, Yandell BS, Schadt EE, Attie AD. Tsc2, a positional candidate gene underlying a quantitative trait locus for hepatic steatosis. J Lipid Res 2012; 53:1493-501. [PMID: 22628617 DOI: 10.1194/jlr.m025239] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Nonalchoholic fatty liver disease (NAFLD) is the most common cause of liver dysfunction and is associated with metabolic diseases, including obesity, insulin resistance, and type 2 diabetes. We mapped a quantitative trait locus (QTL) for NAFLD to chromosome 17 in a cross between C57BL/6 (B6) and BTBR mouse strains made genetically obese with the Lep(ob/ob) mutation. We identified Tsc2 as a gene underlying the chromosome 17 NAFLD QTL. Tsc2 functions as an inhibitor of mammalian target of rapamycin, which is involved in many physiological processes, including cell growth, proliferation, and metabolism. We found that Tsc2(+/-) mice have increased lipogenic gene expression in the liver in an insulin-dependent manner. The coding single nucleotide polymorphism between the B6 and BTBR strains leads to a change in the ability to inhibit the expression of lipogenic genes and de novo lipogenesis in AML12 cells and to promote the proliferation of Ins1 cells. This difference is due to a different affinity of binding to Tsc1, which affects the stability of Tsc2.
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Affiliation(s)
- Chen-Yu Wang
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
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41
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Abstract
MSK1 (mitogen- and stress-activated kinase 1) and MSK2 are nuclear protein kinases that regulate transcription downstream of the ERK1/2 (extracellular-signal-regulated kinase 1/2) and p38α MAPKs (mitogen-activated protein kinases) via the phosphorylation of CREB (cAMP-response-element-binding protein) and histone H3. Previous studies on the function of MSKs have used two inhibitors, H89 and Ro 31-8220, both of which have multiple off-target effects. In the present study, we report the characterization of the in vitro and cellular properties of an improved MSK1 inhibitor, SB-747651A. In vitro, SB-747651A inhibits MSK1 with an IC50 value of 11 nM. Screening of an in vitro panel of 117 protein kinases revealed that, at 1 μM, SB-747651A inhibited four other kinases, PRK2 (double-stranded-RNA-dependent protein kinase 2), RSK1 (ribosomal S6 kinase 1), p70S6K (S6K is S6 kinase) (p70RSK) and ROCK-II (Rho-associated protein kinase 2), with a similar potency to MSK1. In cells, SB-747651A fully inhibited MSK activity at 5-10 μM. SB-747651A was found to inhibit the production of the anti-inflammatory cytokine IL-10 (interleukin-10) in wild-type, but not MSK1/2-knockout, macrophages following LPS (lipopolysaccharide) stimulation. Both SB-747651A and MSK1/2 knockout resulted in elevated pro-inflammatory cytokine production by macrophages in response to LPS. Comparison of the effects of SB-747651A, both in vitro and in cells, demonstrated that SB-747651A exhibited improved selectivity over H89 and Ro 31-8220 and therefore represents a useful tool to study MSK function in cells.
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42
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Selfridge JE, E L, Lu J, Swerdlow RH. Role of mitochondrial homeostasis and dynamics in Alzheimer's disease. Neurobiol Dis 2012; 51:3-12. [PMID: 22266017 DOI: 10.1016/j.nbd.2011.12.057] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 12/27/2011] [Accepted: 12/31/2011] [Indexed: 12/20/2022] Open
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disease that affects a staggering percentage of the aging population and causes memory loss and cognitive decline. Mitochondrial abnormalities can be observed systemically and in brains of patients suffering from AD, and may account for part of the disease phenotype. In this review, we summarize some of the key findings that indicate mitochondrial dysfunction is present in AD-affected subjects, including cytochrome oxidase deficiency, endophenotype data, and altered mitochondrial morphology. Special attention is given to recently described perturbations in mitochondrial autophagy, fission-fusion dynamics, and biogenesis. We also briefly discuss how mitochondrial dysfunction may influence amyloidosis in Alzheimer's disease, why mitochondria are a valid therapeutic target, and strategies for addressing AD-specific mitochondrial dysfunction.
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Affiliation(s)
- J Eva Selfridge
- Department of Molecular and Integrative Physiology, University of Kansas School of Medicine, Kansas City, KS 66160, USA
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43
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Yang Z, Zhang L, Ma A, Liu L, Li J, Gu J, Liu Y. Transient mTOR inhibition facilitates continuous growth of liver tumors by modulating the maintenance of CD133+ cell populations. PLoS One 2011; 6:e28405. [PMID: 22145042 PMCID: PMC3228748 DOI: 10.1371/journal.pone.0028405] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Accepted: 11/07/2011] [Indexed: 01/22/2023] Open
Abstract
The mammalian target of the rapamycin (mTOR) pathway, which drives cell proliferation, is frequently hyperactivated in a variety of malignancies. Therefore, the inhibition of the mTOR pathway has been considered as an appropriate approach for cancer therapy. In this study, we examined the roles of mTOR in the maintenance and differentiation of cancer stem-like cells (CSCs), the conversion of conventional cancer cells to CSCs and continuous tumor growth in vivo. In H-Ras-transformed mouse liver tumor cells, we found that pharmacological inhibition of mTOR with rapamycin greatly increased not only the CD133+ populations both in vitro and in vivo but also the expression of stem cell-like genes. Enhancing mTOR activity by over-expressing Rheb significantly decreased CD133 expression, whereas knockdown of the mTOR yielded an opposite effect. In addition, mTOR inhibition severely blocked the differentiation of CD133+ to CD133- liver tumor cells. Strikingly, single-cell culture experiments revealed that CD133- liver tumor cells were capable of converting to CD133+ cells and the inhibition of mTOR signaling substantially promoted this conversion. In serial implantation of tumor xenografts in nude BALB/c mice, the residual tumor cells that were exposed to rapamycin in vivo displayed higher CD133 expression and had increased secondary tumorigenicity compared with the control group. Moreover, rapamycin treatment also enhanced the level of stem cell-associated genes and CD133 expression in certain human liver tumor cell lines, such as Huh7, PLC/PRC/7 and Hep3B. The mTOR pathway is significantly involved in the generation and the differentiation of tumorigenic liver CSCs. These results may be valuable for the design of more rational strategies to control clinical malignant HCC using mTOR inhibitors.
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MESH Headings
- AC133 Antigen
- Animals
- Antibiotics, Antineoplastic/pharmacology
- Antigens, CD/genetics
- Antigens, CD/metabolism
- Apoptosis/drug effects
- Blotting, Western
- Carcinoma, Hepatocellular/genetics
- Carcinoma, Hepatocellular/metabolism
- Carcinoma, Hepatocellular/pathology
- Cell Differentiation/drug effects
- Cell Line, Tumor
- Cell Proliferation
- Glycoproteins/genetics
- Glycoproteins/metabolism
- Humans
- Liver/cytology
- Liver/drug effects
- Liver/metabolism
- Liver Neoplasms/genetics
- Liver Neoplasms/metabolism
- Liver Neoplasms/pathology
- Male
- Mice
- Mice, Inbred BALB C
- Mice, Knockout
- Mice, Nude
- Neoplastic Stem Cells/metabolism
- Neoplastic Stem Cells/pathology
- Peptides/genetics
- Peptides/metabolism
- RNA, Messenger/genetics
- Real-Time Polymerase Chain Reaction
- Reverse Transcriptase Polymerase Chain Reaction
- Sirolimus/pharmacology
- TOR Serine-Threonine Kinases/antagonists & inhibitors
- TOR Serine-Threonine Kinases/metabolism
- Tumor Suppressor Protein p53/physiology
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Affiliation(s)
- Zhaojuan Yang
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Renji Hospital, Shanghai Cancer Institute, Shanghai, China
| | - Li Zhang
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Renji Hospital, Shanghai Cancer Institute, Shanghai, China
| | - Aihui Ma
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Renji Hospital, Shanghai Cancer Institute, Shanghai, China
| | - Lanlan Liu
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Renji Hospital, Shanghai Cancer Institute, Shanghai, China
- Institute of Reproductive Immunology, Jinan University, Guangzhou, China
| | - Jinjun Li
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Renji Hospital, Shanghai Cancer Institute, Shanghai, China
| | - Jianren Gu
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Renji Hospital, Shanghai Cancer Institute, Shanghai, China
| | - Yongzhong Liu
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Renji Hospital, Shanghai Cancer Institute, Shanghai, China
- * E-mail:
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Ex vivo rapamycin treatment of human cord blood CD34+ cells enhances their engraftment of NSG mice. Blood Cells Mol Dis 2011; 46:318-20. [PMID: 21411351 DOI: 10.1016/j.bcmd.2011.02.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Accepted: 02/16/2011] [Indexed: 02/07/2023]
Abstract
Since cord blood (CB) has become a commonly used source of transplantable hematopoietic stem (HSC) and hematopoietic progenitor cells (HPC), there has been a need to overcome the limited HSC and HPC numbers available to transplant from a single CB, especially for adult recipients. Our laboratory previously demonstrated that Rheb2 overexpression significantly impaired the repopulating ability of HSC. Since overexpression of Rheb2 leads to increased signaling through mTOR, we examined the effect of the mTOR inhibitor rapamycin ex vivo on cytokine expanded CD34(+) CB cells for the engraftment of these cells in non-obese diabetic, severe combined immunodeficient, IL-2 receptor γ chain null (NSG) mice. We observed significant enhancement in engraftment of the CB treated ex vivo with cytokines in the presence of rapamycin prior to transplant, effects seen in primary as well as secondary transplants. These pre-clinical results suggest a positive role for rapamycin during ex vivo culture of CB SCID repopulating cells/HSC.
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45
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Effects of RhebL1 silencing on the mTOR pathway. Mol Biol Rep 2011; 39:2129-37. [PMID: 21655954 DOI: 10.1007/s11033-011-0960-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 05/26/2011] [Indexed: 12/13/2022]
Abstract
The insulin/Ras Homolog Enriched in Brain (Rheb)/Mammalian Target of Rapamycin (mTOR) pathway has been implicated in a variety of cancers. The activation of mTOR is regulated by a small G-protein, Rheb1. In mammalian systems there are two Rheb genes--Rheb1 and RhebL1 (Rheb2). The two genes show high sequence homology, however it has yet to be determined whether they are redundant in function. In this study the contribution of RhebL1 toward the mTOR pathway was investigated by transient gene silencing in three cell lines-HEK293, HeLa, and NIH3T3. Both Rheb1 and RhebL1 genes were silenced individually as well as in combination using eleven commercially synthesized siRNAs. Results from cross reactivity experiments showed the silencing of Rheb1 and RhebL1 to be highly specific for their target gene. This is the first report of its kind to examine the function of the endogenous Rheb genes using single and dual silencing. Phosphorylation of the mTOR effector S6 was not affected by RhebL1 silencing as it was by Rheb1 silencing, suggesting for the first time that RhebL1 may be impacting the mTOR pathway in a different manner than Rheb1.
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46
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Sepsis-induced alterations in protein-protein interactions within mTOR complex 1 and the modulating effect of leucine on muscle protein synthesis. Shock 2011; 35:117-25. [PMID: 20577146 DOI: 10.1097/shk.0b013e3181ecb57c] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Sepsis-induced muscle atrophy is produced in part by decreased protein synthesis mediated by inhibition of mTOR (mammalian target of rapamycin). The present study tests the hypothesis that alteration of specific protein-protein interactions within the mTORC1 (mTOR complex 1) contributes to the decreased mTOR activity observed after cecal ligation and puncture in rats. Sepsis decreased in vivo translational efficiency in gastrocnemius and reduced the phosphorylation of eukaryotic initiation factor (eIF) 4E-binding protein (BP) 1, S6 kinase (S6K) 1, and mTOR, compared with time-matched pair-fed controls. Sepsis decreased T246-phosphorylated PRAS40 (proline-rich Akt substrate 40) and reciprocally increased S792-phosphorylated raptor (regulatory associated protein of mTOR). Despite these phosphorylation changes, sepsis did not alter PRAS40 binding to raptor. The amount of the mTOR-raptor complex did not differ between groups. In contrast, the binding and retention of both 4E-BP1 and S6K1 to raptor were increased, and, conversely, the binding of raptor with eIF3 was decreased in sepsis. These changes in mTORC1 in the basal state were associated with enhanced 5'-AMP activated kinase activity. Acute in vivo leucine stimulation increased muscle protein synthesis in control, but not septic rats. This muscle leucine resistance was associated with coordinated changes in raptor-eIF3 binding and 4E-BP1 phosphorylation. Overall, our data suggest the sepsis-induced decrease in muscle protein synthesis may be mediated by the inability of 4E-BP1 and S6K1 to be phosphorylated and released from mTORC1 as well as the decreased recruitment of eIF3 necessary for a functional 48S complex. These data provide additional mechanistic insight into the molecular mechanisms by which sepsis impairs both basal protein synthesis and the anabolic response to the nutrient signal leucine in skeletal muscle.
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47
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Neuman NA, Henske EP. Non-canonical functions of the tuberous sclerosis complex-Rheb signalling axis. EMBO Mol Med 2011; 3:189-200. [PMID: 21412983 PMCID: PMC3377068 DOI: 10.1002/emmm.201100131] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 02/11/2011] [Accepted: 02/16/2011] [Indexed: 01/10/2023] Open
Abstract
The protein products of the tuberous sclerosis complex (TSC) genes, TSC1 and TSC2, form a complex, which inhibits the small G-protein, Ras homolog enriched in brain (Rheb). The vast majority of research regarding these proteins has focused on mammalian Target of Rapamycin (mTOR), a target of Rheb. Here, we propose that there are clinically relevant functions and targets of TSC1, TSC2 and Rheb, which are independent of mTOR. We present evidence that such non-canonical functions of the TSC-Rheb signalling network exist, propose a standard of evidence for these non-canonical functions, and discuss their potential clinical and therapeutic implications for patients with TSC and lymphangioleiomyomatosis (LAM).
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Affiliation(s)
- Nicole A Neuman
- Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
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48
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Abstract
Ras homolog enriched in brain (Rheb) couples growth factor signaling to activation of the target of rapamycin complex 1 (TORC1). To study its role in mammals, we generated a Rheb knockout mouse. In contrast to mTOR or regulatory-associated protein of mTOR (Raptor) mutants, the inner cell mass of Rheb(-/-) embryos differentiated normally. Nevertheless, Rheb(-/-) embryos died around midgestation, most likely due to impaired development of the cardiovascular system. Rheb(-/-) embryonic fibroblasts showed decreased TORC1 activity, were smaller, and showed impaired proliferation. Rheb heterozygosity extended the life span of tuberous sclerosis complex 1-deficient (Tsc1(-/-)) embryos, indicating that there is a genetic interaction between the Tsc1 and Rheb genes in mouse.
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49
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Lin Y, Henderson P, Pettersson S, Satsangi J, Hupp T, Stevens C. Tuberous sclerosis-2 (TSC2) regulates the stability of death-associated protein kinase-1 (DAPK) through a lysosome-dependent degradation pathway. FEBS J 2010; 278:354-70. [PMID: 21134130 DOI: 10.1111/j.1742-4658.2010.07959.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Yao Lin
- University of Edinburgh, Institute of Genetics and Molecular Medicine, Edinburgh, UK
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50
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Palaniappan M, Menon KMJ. Human chorionic gonadotropin stimulates theca-interstitial cell proliferation and cell cycle regulatory proteins by a cAMP-dependent activation of AKT/mTORC1 signaling pathway. Mol Endocrinol 2010; 24:1782-93. [PMID: 20660299 DOI: 10.1210/me.2010-0044] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In addition to playing a cardinal role in androgen production, LH also regulates growth and proliferation of theca-interstitial (T-I) cells. Here, we show for the first time that LH/human chorionic gonadotropin (hCG) regulates T-I cell proliferation via the mammalian target of rapamycin complex 1 (mTORC1) signaling network. LH/hCG treatment showed a time-dependent stimulation of T-I cell proliferation and phosphorylation of protein kinase B (AKT), ERK1/2, and ribosomal protein (rp)S6 kinase 1 (S6K1), and its downstream effector, rpS6. Pharmacological inhibition of ERK1/2 signaling did not block the hCG-induced phosphorylation of tuberin, the upstream regulator of mTORC1 or S6K1, the downstream target of mTORC1. However, inhibition of AKT signaling completely blocked the hCG response. Furthermore, the AKT-specific inhibitor abolished forskolin (FSK)-stimulated phosphorylation of AKT, tuberin, S6K1, and rpS6. Human CG and FSK-mediated phosphorylation of AKT and downstream targets of mTORC1 were attenuated by inhibition of adenylyl cyclase. Pharmacologic targeting of mTORC1 with rapamycin also abrogated hCG or FSK-induced phosphorylation of S6K1, rpS6, and eukaryotic initiation factor 4E binding protein 1. In addition, hCG or FSK-mediated up-regulation of the cell cycle regulatory proteins cyclin-dependent kinase 4, cyclin D3, and proliferating cell nuclear antigen was blocked by rapamycin. These results were further confirmed by demonstrating that knockdown of mTORC1 using small interfering RNA abolished hCG-mediated increases in cell proliferation and the expression of cyclin D3 and proliferating cell nuclear antigen. Taken together, the present studies show a novel intracellular signaling pathway for T-I cell proliferation involving LH/hCG-mediated activation of the AKT/mTORC1 signaling cascade.
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Affiliation(s)
- Murugesan Palaniappan
- Department of Obstetrics, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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