1
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Li C, Yi Y, Ouyang Y, Chen F, Lu C, Peng S, Wang Y, Chen X, Yan X, Xu H, Li S, Feng L, Xie X. TORSEL, a 4EBP1-based mTORC1 live-cell sensor, reveals nutrient-sensing targeting by histone deacetylase inhibitors. Cell Biosci 2024; 14:68. [PMID: 38824577 PMCID: PMC11143692 DOI: 10.1186/s13578-024-01250-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 05/21/2024] [Indexed: 06/03/2024] Open
Abstract
BACKGROUND Mammalian or mechanistic target of rapamycin complex 1 (mTORC1) is an effective therapeutic target for diseases such as cancer, diabetes, aging, and neurodegeneration. However, an efficient tool for monitoring mTORC1 inhibition in living cells or tissues is lacking. RESULTS We developed a genetically encoded mTORC1 sensor called TORSEL. This sensor changes its fluorescence pattern from diffuse to punctate when 4EBP1 dephosphorylation occurs and interacts with eIF4E. TORSEL can specifically sense the physiological, pharmacological, and genetic inhibition of mTORC1 signaling in living cells and tissues. Importantly, TORSEL is a valuable tool for imaging-based visual screening of mTORC1 inhibitors. Using TORSEL, we identified histone deacetylase inhibitors that selectively block nutrient-sensing signaling to inhibit mTORC1. CONCLUSIONS TORSEL is a unique living cell sensor that efficiently detects the inhibition of mTORC1 activity, and histone deacetylase inhibitors such as panobinostat target mTORC1 signaling through amino acid sensing.
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Affiliation(s)
- Canrong Li
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Yuguo Yi
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Yingyi Ouyang
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Fengzhi Chen
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Chuxin Lu
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Shujun Peng
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Yifan Wang
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Xinyu Chen
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Xiao Yan
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Haolun Xu
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China
| | - Shuiming Li
- College of Life Sciences and Oceanography, Shenzhen Key Laboratory of Microbial Genetic Engineering, Shenzhen University, Shenzhen, China
| | - Lin Feng
- Department of Experimental Research, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Xiaoduo Xie
- School of Medicine, Shenzhen Campus of Sun Yat-sen University, Sun Yat-sen University, Shenzhen, China.
- Department of Experimental Research, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China.
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2
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Wang Y, Lei J, Zhang S, Wang X, Jin J, Liu Y, Gan M, Yuan Y, Sun L, Li X, Han T, Wang JB. 4EBP1 senses extracellular glucose deprivation and initiates cell death signaling in lung cancer. Cell Death Dis 2022; 13:1075. [PMID: 36575176 PMCID: PMC9794714 DOI: 10.1038/s41419-022-05466-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 11/22/2022] [Accepted: 11/24/2022] [Indexed: 12/28/2022]
Abstract
Nutrient-limiting conditions are common during cancer development. The coordination of cellular glucose levels and cell survival is a fundamental question in cell biology and has not been completely understood. 4EBP1 is known as a translational repressor to regulate cell proliferation and survival by controlling translation initiation, however, whether 4EBP1 could participate in tumor survival by other mechanism except for translational repression function, especially under glucose starvation conditions remains unknown. Here, we found that protein levels of 4EBP1 was up-regulated in the central region of the tumor which always suffered nutrient deprivation compared with the peripheral region. We further discovered that 4EBP1 was dephosphorylated by PTPMT1 under glucose starvation conditions, which prevented 4EBP1 from being targeted for ubiquitin-mediated proteasomal degradation by HERC5. After that, 4EBP1 translocated to cytoplasm and interacted with STAT3 by competing with JAK and ERK, leading to the inactivation of STAT3 in the cytoplasm, resulting in apoptosis under glucose withdrawal conditions. Moreover, 4EBP1 knockdown increased the tumor volume and weight in xenograft models by inhibiting apoptosis in the central region of tumor. These findings highlight a novel mechanism for 4EBP1 as a new cellular glucose sensor in regulating cancer cell death under glucose deprivation conditions, which was different from its classical function as a translational repressor.
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Affiliation(s)
- Yanan Wang
- grid.412604.50000 0004 1758 4073Jiangxi Institute of Respiratory Disease, The First Affiliated Hospital of Nanchang University, Nanchang City, 330006 Jiangxi China ,Jiangxi Hospital of China-Japan Friendship Hospital, Nanchang City, 330052 Jiangxi China ,Jiangxi Clinical Research Center for Respiratory Diseases, Nanchang City, 330006 Jiangxi China
| | - Jiapeng Lei
- School of Basic Medical Sciences, Nanchang Medical College, Nanchang City, 330006 Jiangxi China
| | - Song Zhang
- grid.412465.0Department of Hepatobiliary and Pancreatic Surgery, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou City, 310009 Zhejiang China
| | - Xiaomei Wang
- grid.415912.a0000 0004 4903 149XDepartment of Pharmacy, Liaocheng People’s Hospital, Liaocheng City, 252000 Shandong China
| | - Jiangbo Jin
- grid.260463.50000 0001 2182 8825Department of Thoracic Surgery, The First Affifiliated Hospital of Nanchang University, Nanchang City, 330006 Jiangxi China
| | - Yufeng Liu
- grid.260463.50000 0001 2182 8825School of Basic Medical Sciences, Nanchang University, Nanchang City, 330031 Jiangxi China
| | - Mingxi Gan
- grid.260463.50000 0001 2182 8825School of Basic Medical Sciences, Nanchang University, Nanchang City, 330031 Jiangxi China
| | - Yi Yuan
- grid.260463.50000 0001 2182 8825Huankui Academy, Nanchang University, Nanchang City, 330031 Jiangxi China
| | - Longhua Sun
- grid.412604.50000 0004 1758 4073Departments of Pulmonary and Critical Care Medicine, The First Affiliated Hospital of Nanchang University, Nanchang City, 330006 Jiangxi China
| | - Xiaolei Li
- grid.412604.50000 0004 1758 4073Jiangxi Institute of Respiratory Disease, The First Affiliated Hospital of Nanchang University, Nanchang City, 330006 Jiangxi China
| | - Tianyu Han
- grid.412604.50000 0004 1758 4073Jiangxi Institute of Respiratory Disease, The First Affiliated Hospital of Nanchang University, Nanchang City, 330006 Jiangxi China ,Jiangxi Hospital of China-Japan Friendship Hospital, Nanchang City, 330052 Jiangxi China ,Jiangxi Clinical Research Center for Respiratory Diseases, Nanchang City, 330006 Jiangxi China
| | - Jian-Bin Wang
- grid.260463.50000 0001 2182 8825Department of Thoracic Surgery, The First Affifiliated Hospital of Nanchang University, Nanchang City, 330006 Jiangxi China ,grid.260463.50000 0001 2182 8825School of Basic Medical Sciences, Nanchang University, Nanchang City, 330031 Jiangxi China
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3
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Yu C, Zhang X, Wang J, Song H, Liu W, Luo B. Molecular mechanism of aquaporin 3 (AQP3) regulating by LMP2A and its crosstalk with 4E-BP1 via ERK signaling pathway in EBV-associated gastric cancer. Virus Res 2022; 322:198947. [PMID: 36181978 DOI: 10.1016/j.virusres.2022.198947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 09/26/2022] [Accepted: 09/26/2022] [Indexed: 12/24/2022]
Abstract
Aquaporin 3(AQP3) is involved in epithelial-mesenchymal transformation of tumor cells and is closely related to the occurrence and development of tumors. However, the regulatory mechanism and function of AQP3 in EBV-associated gastric cancer (EBVaGC) are still poorly understood. This study aims to explore the regulatory effect of EBV on AQP3 and the cross talk of AQP3 with EIF4E-binding proteins 1(4E-BP1) in EBVaGC. The effect of LMP2A on the expression of AQP3 and 4E-BP1 was analyzed using real-time PCR and western blotting. The biological functions of AQP3 and 4E-BP1 in gastric cancer cells were detected by cell biological experiments. In addition, we examined the role of mTOR and ERK signaling pathways in the LMP2A/AQP3/4E-BP1 regulatory axis. We found that LMP2A could down-regulate AQP3 expression by inhibiting the activation of mTOR signaling pathway, and further promote autophagy and migration of gastric cancer cells. AQP3 up-regulated the expression of 4E-BP1 and its phosphorylated protein by activating ERK signaling pathway, thus promoting the autophagy and proliferation of gastric cancer cells. In conclusion, EBV-encoded LMP2A inhibits AQP3 expression, and further participates in cell proliferation, migration and autophagy through the mTOR/AQP3/ERK/4E-BP1 axis.
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Affiliation(s)
- Caixia Yu
- Department of Pathogenic Biology, School of Basic Medicine, Qingdao University, No.308 Ningxia Road, Qingdao 266071, China
| | - Xing Zhang
- Department of Pathogenic Biology, School of Basic Medicine, Qingdao University, No.308 Ningxia Road, Qingdao 266071, China
| | - Jiayi Wang
- Department of Pathogenic Biology, School of Basic Medicine, Qingdao University, No.308 Ningxia Road, Qingdao 266071, China; Institute of Virology, Hannover Medical School, Hanover, Germany
| | - Hui Song
- Department of Pathogenic Biology, School of Basic Medicine, Qingdao University, No.308 Ningxia Road, Qingdao 266071, China; Department of Clinical Laboratory, Qingdao Women and Children's Hospital, Qingdao University, No. 6 Tongfu Road, Qingdao 266034, China
| | - Wen Liu
- Department of Pathogenic Biology, School of Basic Medicine, Qingdao University, No.308 Ningxia Road, Qingdao 266071, China.
| | - Bing Luo
- Department of Pathogenic Biology, School of Basic Medicine, Qingdao University, No.308 Ningxia Road, Qingdao 266071, China.
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4
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Vanzant E, Frayman R, Hensley S, Rosenthal M. Should Anabolic Agents be Used for Resolving Catabolism in Post-ICU Recovery? CURRENT SURGERY REPORTS 2022. [DOI: 10.1007/s40137-022-00336-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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5
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Wang X, Xu J, Zeng H, Han Z. Enhancement of BCAT2-Mediated Valine Catabolism Stimulates β-Casein Synthesis via the AMPK-mTOR Signaling Axis in Bovine Mammary Epithelial Cells. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2022; 70:9898-9907. [PMID: 35916279 DOI: 10.1021/acs.jafc.2c03629] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Valine, a kind of branched-chain amino acid, plays a regulatory role beyond that of a building block in milk protein synthesis. However, the underlying molecular mechanism through which valine stimulates β-casein synthesis has not been clarified. Therefore, our study aimed to evaluate the effect of valine on β-casein synthesis and shed light into the molecular mechanism using an in vitro model. Results showed that valine supplementation significantly increased β-casein synthesis in bovine mammary epithelial cells (BMECs). Meanwhile, the supplementation of valine resulted in high levels of branched-chain aminotransferase transaminase 2 (BCAT2), TCA-cycle intermediate metabolites, and ATP, AMP-activated protein kinase (AMPK) inhibition, and mammalian target of rapamycin (mTOR) activation. Furthermore, the inhibition of BCAT2 decreased the β-casein synthesis and downregulated the AMPK-mTOR pathway, with similar results observed for AMPK activation. Together, the present data indicate that valine promotes the synthesis of β-casein by affecting the AMPK-mTOR signaling axis and that BCAT2-mediated valine catabolism is the key target.
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Affiliation(s)
- Xinling Wang
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
| | - Jie Xu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
| | - Hanfang Zeng
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
| | - Zhaoyu Han
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
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6
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Kliche J, Ivarsson Y. Orchestrating serine/threonine phosphorylation and elucidating downstream effects by short linear motifs. Biochem J 2022; 479:1-22. [PMID: 34989786 PMCID: PMC8786283 DOI: 10.1042/bcj20200714] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 12/16/2021] [Accepted: 12/20/2021] [Indexed: 12/13/2022]
Abstract
Cellular function is based on protein-protein interactions. A large proportion of these interactions involves the binding of short linear motifs (SLiMs) by folded globular domains. These interactions are regulated by post-translational modifications, such as phosphorylation, that create and break motif binding sites or tune the affinity of the interactions. In addition, motif-based interactions are involved in targeting serine/threonine kinases and phosphatases to their substrate and contribute to the specificity of the enzymatic actions regulating which sites are phosphorylated. Here, we review how SLiM-based interactions assist in determining the specificity of serine/threonine kinases and phosphatases, and how phosphorylation, in turn, affects motif-based interactions. We provide examples of SLiM-based interactions that are turned on/off, or are tuned by serine/threonine phosphorylation and exemplify how this affects SLiM-based protein complex formation.
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Affiliation(s)
- Johanna Kliche
- Department of Chemistry – BMC, Uppsala University, Husargatan 3, Box 576 751 23 Uppsala, Sweden
| | - Ylva Ivarsson
- Department of Chemistry – BMC, Uppsala University, Husargatan 3, Box 576 751 23 Uppsala, Sweden
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7
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Li C, Li K, Li K, Ai K, Zhang Y, Zhang J, Li J, Wei X, Yang J. Essential role of 4E-BP1 for lymphocyte activation and proliferation in the adaptive immune response of Nile tilapia. FISH AND SHELLFISH IMMUNOLOGY REPORTS 2021; 2:100006. [DOI: 10.1016/j.fsirep.2021.100006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 02/04/2021] [Accepted: 02/11/2021] [Indexed: 12/14/2022] Open
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8
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Control of the eIF4E activity: structural insights and pharmacological implications. Cell Mol Life Sci 2021; 78:6869-6885. [PMID: 34541613 PMCID: PMC8558276 DOI: 10.1007/s00018-021-03938-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 08/28/2021] [Accepted: 09/08/2021] [Indexed: 12/17/2022]
Abstract
The central role of eukaryotic translation initiation factor 4E (eIF4E) in controlling mRNA translation has been clearly assessed in the last decades. eIF4E function is essential for numerous physiological processes, such as protein synthesis, cellular growth and differentiation; dysregulation of its activity has been linked to ageing, cancer onset and progression and neurodevelopmental disorders, such as autism spectrum disorder (ASD) and Fragile X Syndrome (FXS). The interaction between eIF4E and the eukaryotic initiation factor 4G (eIF4G) is crucial for the assembly of the translational machinery, the initial step of mRNA translation. A well-characterized group of proteins, named 4E-binding proteins (4E-BPs), inhibits the eIF4E–eIF4G interaction by competing for the same binding site on the eIF4E surface. 4E-BPs and eIF4G share a single canonical motif for the interaction with a conserved hydrophobic patch of eIF4E. However, a second non-canonical and not conserved binding motif was recently detected for eIF4G and several 4E-BPs. Here, we review the structural features of the interaction between eIF4E and its molecular partners eIF4G and 4E-BPs, focusing on the implications of the recent structural and biochemical evidence for the development of new therapeutic strategies. The design of novel eIF4E-targeting molecules that inhibit translation might provide new avenues for the treatment of several conditions.
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9
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Heimhalt M, Berndt A, Wagstaff J, Anandapadamanaban M, Perisic O, Maslen S, McLaughlin S, Yu CWH, Masson GR, Boland A, Ni X, Yamashita K, Murshudov GN, Skehel M, Freund SM, Williams RL. Bipartite binding and partial inhibition links DEPTOR and mTOR in a mutually antagonistic embrace. eLife 2021; 10:e68799. [PMID: 34519269 PMCID: PMC8439657 DOI: 10.7554/elife.68799] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 07/31/2021] [Indexed: 12/16/2022] Open
Abstract
The mTORC1 kinase complex regulates cell growth, proliferation, and survival. Because mis-regulation of DEPTOR, an endogenous mTORC1 inhibitor, is associated with some cancers, we reconstituted mTORC1 with DEPTOR to understand its function. We find that DEPTOR is a unique partial mTORC1 inhibitor that may have evolved to preserve feedback inhibition of PI3K. Counterintuitively, mTORC1 activated by RHEB or oncogenic mutation is much more potently inhibited by DEPTOR. Although DEPTOR partially inhibits mTORC1, mTORC1 prevents this inhibition by phosphorylating DEPTOR, a mutual antagonism that requires no exogenous factors. Structural analyses of the mTORC1/DEPTOR complex showed DEPTOR's PDZ domain interacting with the mTOR FAT region, and the unstructured linker preceding the PDZ binding to the mTOR FRB domain. The linker and PDZ form the minimal inhibitory unit, but the N-terminal tandem DEP domains also significantly contribute to inhibition.
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Affiliation(s)
- Maren Heimhalt
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Alex Berndt
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Jane Wagstaff
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | | | - Olga Perisic
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Sarah Maslen
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | | | | | - Glenn R Masson
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Andreas Boland
- Department of Molecular Biology, University of GenevaGenevaSwitzerland
| | - Xiaodan Ni
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | | | | | - Mark Skehel
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
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10
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Böhm R, Imseng S, Jakob RP, Hall MN, Maier T, Hiller S. The dynamic mechanism of 4E-BP1 recognition and phosphorylation by mTORC1. Mol Cell 2021; 81:2403-2416.e5. [PMID: 33852892 DOI: 10.1016/j.molcel.2021.03.031] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 02/22/2021] [Accepted: 03/18/2021] [Indexed: 10/21/2022]
Abstract
The activation of cap-dependent translation in eukaryotes requires multisite, hierarchical phosphorylation of 4E-BP by the 1 MDa kinase mammalian target of rapamycin complex 1 (mTORC1). To resolve the mechanism of this hierarchical phosphorylation at the atomic level, we monitored by NMR spectroscopy the interaction of intrinsically disordered 4E binding protein isoform 1 (4E-BP1) with the mTORC1 subunit regulatory-associated protein of mTOR (Raptor). The N-terminal RAIP motif and the C-terminal TOR signaling (TOS) motif of 4E-BP1 bind separate sites in Raptor, resulting in avidity-based tethering of 4E-BP1. This tethering orients the flexible central region of 4E-BP1 toward the mTORC1 kinase site for phosphorylation. The structural constraints imposed by the two tethering interactions, combined with phosphorylation-induced conformational switching of 4E-BP1, explain the hierarchy of 4E-BP1 phosphorylation by mTORC1. Furthermore, we demonstrate that mTORC1 recognizes both free and eIF4E-bound 4E-BP1, allowing rapid phosphorylation of the entire 4E-BP1 pool and efficient activation of translation. Finally, our findings provide a mechanistic explanation for the differential rapamycin sensitivity of the 4E-BP1 phosphorylation sites.
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Affiliation(s)
- Raphael Böhm
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Stefan Imseng
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Roman P Jakob
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Michael N Hall
- Biozentrum, University of Basel, 4056 Basel, Switzerland.
| | - Timm Maier
- Biozentrum, University of Basel, 4056 Basel, Switzerland.
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11
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Yeo HS, Lim JY, Ahn NY. Effects of Aging on Angiogenic and Muscle Growth-Related Factors in Naturally Aged Rat Skeletal Muscles. Ann Geriatr Med Res 2020; 24:305-312. [PMID: 33389976 PMCID: PMC7781957 DOI: 10.4235/agmr.20.0077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 12/11/2020] [Indexed: 01/07/2023] Open
Abstract
Background This study explored the effects of aging on the expression of angiogenic and muscle protein synthesis factors, as well as the number of satellite cells affecting sarcopenia in naturally aged rat skeletal muscles. Methods We divided 16 Sprague-Dawley rats into young (12 weeks old, n=8) and old (24 months old, n=8) groups and compared muscle and body weight (BW) between them. We also analyzed the expression levels of angiogenic and muscle growth proteins in soleus (slow-twitch) and extensor digitorum longus (EDL; fast-twitch) muscles by western blotting and assessed the number of skeletal muscle satellite cells and myonuclei and mean fiber cross-sectional area (CSA) using by immunofluorescence staining. Results EDL/BW was significantly lower in old rats than in young rats (p=0.002). The vascular endothelial growth factor level in soleus muscles was significantly lower in old rats than in young rats (p=0.001). Hypoxia-inducible factor 1-alpha and fetal liver kinase 1 levels in EDL muscles were lower in old rats than in young rats (p=0.001). The mammalian target of rapamycin (mTOR), p70S6K, and 4E-BP1 levels were significantly lower in the soleus muscles of old rats than in those of young rats (p<0.01). Similarly, insulin growth factor-1, Akt, mTOR, and p70S6K levels were significantly lower in EDL muscles of old rats than in those of young rats (p<0.01). Additionally, myonuclei/fiber, Pax7/fiber, and mean fiber CSAs in both muscle types were significantly lower in old rats than in young rats (p<0.01). Conclusion These data suggest different regulation of indices of angiogenic and muscle growth with aging in different muscle types.
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Affiliation(s)
- Hyo-Seong Yeo
- Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Jae-Young Lim
- Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Na-Young Ahn
- Department of Physical Education, College of Physical Education, Keimyung University, Daegu, Korea
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12
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Xin Y, Min P, Xu H, Zhang Z, Zhang Y, Zhang Y. CD26 upregulates proliferation and invasion in keloid fibroblasts through an IGF-1-induced PI3K/AKT/mTOR pathway. BURNS & TRAUMA 2020; 8:tkaa025. [PMID: 33150188 PMCID: PMC7596300 DOI: 10.1093/burnst/tkaa025] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 04/07/2020] [Indexed: 01/21/2023]
Abstract
Background Keloid is a fibrotic dermal disease characterized by an abnormal increase in fibroblast proliferation and invasion. These pathological behaviours may be related to the heterogeneity of keloid fibroblasts (KFs); however, because of a lack of effective biomarkers for KFs it is difficult to study the underlying mechanism. Our previous studies revealed that the expansion of CD26+ KFs was responsible for increased keloid proliferation and invasion capabilities; the intrinsic relationship and mechanism between CD26 and keloid is therefore worthy of further investigation. The aim of this study was to explore molecular mechanisms in the process of CD26 upregulated KFs proliferation and invasion abilities, and provide more evidence for CD26 as an effective biomarker of keloid and a new clinical therapeutic target. Methods Flow cytometry was performed to isolate CD26+/CD26− fibroblasts from KFs and normal fibroblasts. To generate stably silenced KFs for CD26 and insulin-like growth factor-1 receptor (IGF-1R), lentiviral particles encoding shRNA targeting CD26 and IGF-1R were used for transfection. Cell proliferations were analysed by cell counting kit-8 assay and 5-ethynyl-2′-deoxyuridine (EdU) incorporation assay. Scratching assay and transwell assay were used to assess cell migration and invasion abilities. To further quantify the regulatory role of CD26 expression in the relevant signalling pathway, RT-qPCR, western blot, ELISA, PI3K activity assay and immunofluorescence were used. Results Aberrant expression of CD26 in KFs was proven to be associated with increased proliferation and invasion of KFs. Furthermore, the role of the IGF-1/IGF-1 receptor axis was also studied in CD26 and was found to upregulate KF proliferation and invasion. The PI3K/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway was shown to affect CD26-regulated KF proliferation and invasion by increasing phosphorylation levels of S6 kinase and 4E-binding protein. Conclusions CD26 can be the effective biomarker for KFs, and its expression is closely related to proliferation and invasion in keloids through the IGF-1-induced PI3K/AKT/mTOR pathway. This work provides a novel perspective on the pathological mechanisms affecting KFs and therapeutic strategies against keloids.
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Affiliation(s)
- Yu Xin
- Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhi Zao Ju Road, Shanghai, 200011, China
| | - Peiru Min
- Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhi Zao Ju Road, Shanghai, 200011, China
| | - Heng Xu
- Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhi Zao Ju Road, Shanghai, 200011, China
| | - Zheng Zhang
- Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhi Zao Ju Road, Shanghai, 200011, China
| | - Yan Zhang
- Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhi Zao Ju Road, Shanghai, 200011, China
| | - Yixin Zhang
- Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhi Zao Ju Road, Shanghai, 200011, China
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13
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Holditch SJ, Brown CN, Atwood DJ, Pokhrel D, Brown SE, Lombardi AM, Nguyen KN, Hill RC, Lanaspa M, Hopp K, Weiser-Evans MCM, Edelstein CL. The consequences of increased 4E-BP1 in polycystic kidney disease. Hum Mol Genet 2020; 28:4132-4147. [PMID: 31646342 DOI: 10.1093/hmg/ddz244] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 08/28/2019] [Accepted: 09/25/2019] [Indexed: 01/02/2023] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease, characterized by cyst formation and growth. Hyperproliferation is a major contributor to cyst growth. At the nexus of regulating proliferation, is 4E-BP1. We demonstrate that ADPKD mouse and rat models, ADPKD patient renal biopsies and PKD1-/- cells exhibited hyperphosphorylated 4E-BP1, a biomarker of increased translation and proliferation. We hypothesized that expression of constitutively active 4E-BP1 constructs (4E-BP1F113A and 4E-BP1R13AF113A) would decrease proliferation and reduce cyst expansion. Utilizing the Pkd1RC/RC mouse, we determined the effect of 4E-BP1F113A on PKD. Unexpectedly, 4E-BP1F113A resulted in increased cyst burden and suppressed apoptosis markers, increased anti-apoptotic Bcl-2 protein and increased mitochondrial proteins. Exogenous 4E-BP1 enhanced proliferation, decreased apoptosis, increased anti-apoptotic Bcl-2 protein, impaired NADPH oxidoreductase activity, increased mitochondrial proteins and increased superoxide production in PKD patient-derived renal epithelial cells. Reduced 4E-BP1 expression suppressed proliferation, restored apoptosis and improved cellular metabolism. These findings provide insight into how cyst-lining cells respond to 4E-BP1.
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Affiliation(s)
- Sara J Holditch
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Carolyn N Brown
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Daniel J Atwood
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Deepak Pokhrel
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Sara E Brown
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Andrew M Lombardi
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Khoa N Nguyen
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Ryan C Hill
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Miguel Lanaspa
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Katharina Hopp
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Mary C M Weiser-Evans
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
| | - Charles L Edelstein
- Division of Renal Diseases and Hypertension, University of Colorado at Denver, Denver, CO, USA
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14
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Sun J, Feng D, Xi H, Luo J, Zhou Z, Liu Q, Chen Y, Shao Q. CD24 blunts the sensitivity of retinoblastoma to vincristine by modulating autophagy. Mol Oncol 2020; 14:1740-1759. [PMID: 32394616 PMCID: PMC7400807 DOI: 10.1002/1878-0261.12708] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 04/25/2020] [Accepted: 05/05/2020] [Indexed: 12/14/2022] Open
Abstract
Retinoblastoma (RB) is the most common childhood malignant intraocular tumor. The clinical efficacy of vincristine (VCR) in the treatment of RB is severely limited by drug resistance. Here, we found that CD24, a GPI-anchored protein, was overexpressed in human RB tissues and RB cell lines, and was associated with the sensitivity of RB cells in response to VCR therapy. We demonstrated that CD24 plays a critical role in impairing RB sensitivity to VCR via regulating autophagy. Mechanistically, CD24 recruits PTEN to the lipid raft domain and regulates the PTEN/AKT/mTORC1 pathway to activate autophagy. Lipid raft localization was essential for CD24 recruitment function. Collectively, our findings revealed a novel role of CD24 in regulating RB sensitivity to VCR and showed that CD24 is a potential target for improving chemotherapeutic sensitivity and RB patient outcomes.
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Affiliation(s)
- Jie Sun
- Department of Ophthalmology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Dongju Feng
- Department of Immunology, Key Laboratory of Immune Microenvironment and Disease, Nanjing Medical University, Nanjing, China
| | - Huiyu Xi
- Department of Ophthalmology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China.,Department of Ophthalmology, Xuzhou First People's Hospital of Xuzhou Medical University, Xuzhou Eye Research Institute, Xuzhou, China
| | - Jiajing Luo
- Department of Immunology, Key Laboratory of Immune Microenvironment and Disease, Nanjing Medical University, Nanjing, China
| | - Zewei Zhou
- Department of Immunology, Key Laboratory of Immune Microenvironment and Disease, Nanjing Medical University, Nanjing, China
| | - Qinghuai Liu
- Department of Ophthalmology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Yun Chen
- Department of Immunology, Key Laboratory of Immune Microenvironment and Disease, Nanjing Medical University, Nanjing, China.,Jiangsu Key Lab of Cancer Biomarkers, Prevention and Treatment, Collaborative Innovation Center for Cancer Personalized Medicine, Nanjing Medical University, Nanjing, China
| | - Qing Shao
- Department of Ophthalmology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
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15
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Sun R, Cheng E, Velásquez C, Chang Y, Moore PS. Mitosis-related phosphorylation of the eukaryotic translation suppressor 4E-BP1 and its interaction with eukaryotic translation initiation factor 4E (eIF4E). J Biol Chem 2019; 294:11840-11852. [PMID: 31201269 PMCID: PMC6682726 DOI: 10.1074/jbc.ra119.008512] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 06/10/2019] [Indexed: 11/22/2022] Open
Abstract
Eukaryotic translation initiation factor 4E (eIF4E)–binding protein 1 (4E-BP1) inhibits cap-dependent translation in eukaryotes by competing with eIF4G for an interaction with eIF4E. Phosphorylation at Ser-83 of 4E-BP1 occurs during mitosis through the activity of cyclin-dependent kinase 1 (CDK1)/cyclin B rather than through canonical mTOR kinase activity. Here, we investigated the interaction of eIF4E with 4E-BP1 or eIF4G during interphase and mitosis. We observed that 4E-BP1 and eIF4G bind eIF4E at similar levels during interphase and mitosis. The most highly phosphorylated mitotic 4E-BP1 isoform (δ) did not interact with eIF4E, whereas a distinct 4E-BP1 phospho-isoform, EB-γ, phosphorylated at Thr-70, Ser-83, and Ser-101, bound to eIF4E during mitosis. Two-dimensional gel electrophoretic analysis corroborated the identity of the phosphorylation marks on the eIF4E-bound 4E-BP1 isoforms and uncovered a population of phosphorylated 4E-BP1 molecules lacking Thr-37/Thr-46–priming phosphorylation. Moreover, proximity ligation assays for phospho-4E-BP1 and eIF4E revealed different in situ interactions during interphase and mitosis. The eIF4E:eIF4G interaction was not inhibited but rather increased in mitotic cells, consistent with active translation initiation during mitosis. Phosphodefective substitution of 4E-BP1 at Ser-83 did not change global translation or individual mRNA translation profiles as measured by single-cell nascent protein synthesis and eIF4G RNA immunoprecipitation sequencing. Mitotic 5′-terminal oligopyrimidine RNA translation was active and, unlike interphase translation, resistant to mTOR inhibition. Our findings reveal the phosphorylation profiles of 4E-BP1 isoforms and their interactions with eIF4E throughout the cell cycle and indicate that 4E-BP1 does not specifically inhibit translation initiation during mitosis.
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Affiliation(s)
- Rui Sun
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.,Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213
| | - Erdong Cheng
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.,Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213
| | - Celestino Velásquez
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.,Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213
| | - Yuan Chang
- Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213 .,Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
| | - Patrick S Moore
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15213 .,Cancer Virology Program, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15213
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16
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Rutkovsky AC, Yeh ES, Guest ST, Findlay VJ, Muise-Helmericks RC, Armeson K, Ethier SP. Eukaryotic initiation factor 4E-binding protein as an oncogene in breast cancer. BMC Cancer 2019; 19:491. [PMID: 31122207 PMCID: PMC6533768 DOI: 10.1186/s12885-019-5667-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 05/01/2019] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Eukaryotic Initiation Factor 4E-Binding Protein (EIF4EBP1, 4EBP1) is overexpressed in many human cancers including breast cancer, yet the role of 4EBP1 in breast cancer remains understudied. Despite the known role of 4EBP1 as a negative regulator of cap-dependent protein translation, 4EBP1 is predicted to be an essential driving oncogene in many cancer cell lines in vitro, and can act as a driver of cancer cell proliferation. EIF4EBP1 is located within the 8p11-p12 genomic locus, which is frequently amplified in breast cancer and is known to predict poor prognosis and resistance to endocrine therapy. METHODS Here we evaluated the effect of 4EBP1 targeting using shRNA knock-down of expression of 4EBP1, as well as response to the mTORC targeted drug everolimus in cell lines representing different breast cancer subtypes, including breast cancer cells with the 8p11-p12 amplicon, to better define a context and mechanism for oncogenic 4EBP1. RESULTS Using a genome-scale shRNA screen on the SUM panel of breast cancer cell lines, we found 4EBP1 to be a strong hit in the 8p11 amplified SUM-44 cells, which have amplification and overexpression of 4EBP1. We then found that knock-down of 4EBP1 resulted in dramatic reductions in cell proliferation in 8p11 amplified breast cancer cells as well as in other luminal breast cancer cell lines, but had little or no effect on the proliferation of immortalized but non-tumorigenic human mammary epithelial cells. Kaplan-Meier analysis of EIF4EBP1 expression in breast cancer patients demonstrated that overexpression of this gene was associated with reduced relapse free patient survival across all breast tumor subtypes. CONCLUSIONS These results are consistent with an oncogenic role of 4EBP1 in luminal breast cancer and suggests a role for this protein in cell proliferation distinct from its more well-known role as a regulator of cap-dependent translation.
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Affiliation(s)
- Alexandria C. Rutkovsky
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, 171 Ashley Avenue, MSC 908, Charleston, SC 29425 USA
- Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Charleston, SC 29425 USA
| | - Elizabeth S. Yeh
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, 173 Ashley Avenue, BSB 358, MSC 509, Charleston, SC 29425 USA
- Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Charleston, SC 29425 USA
| | - Stephen T. Guest
- Department of Computational Medicine and Bioinformatics, University of Michigan, 500 S. State Street, Ann Arbor, MI 48109 USA
| | - Victoria J. Findlay
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, 171 Ashley Avenue, MSC 908, Charleston, SC 29425 USA
| | - Robin C. Muise-Helmericks
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, BSB 601, MSC 508, Charleston, SC 29425 USA
| | - Kent Armeson
- Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Charleston, SC 29425 USA
- Department of Public Health Sciences, Medical University of South Carolina, 135 Cannon Street Suite 303 MSC 835, Charleston, USA
| | - Stephen P. Ethier
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, 171 Ashley Avenue, MSC 908, Charleston, SC 29425 USA
- Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Charleston, SC 29425 USA
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17
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Mitchell DC, Menon A, Garner AL. Chemoproteomic Profiling Uncovers CDK4-Mediated Phosphorylation of the Translational Suppressor 4E-BP1. Cell Chem Biol 2019; 26:980-990.e8. [PMID: 31056462 DOI: 10.1016/j.chembiol.2019.03.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 02/04/2019] [Accepted: 03/25/2019] [Indexed: 01/03/2023]
Abstract
Recent estimates of the human proteome suggest there are ∼20,000 protein-coding genes, the protein products of which contain >145,000 phosphosites. Unfortunately, in-depth examination of the human phosphoproteome has outpaced the ability to annotate the kinases that mediate these post-translational modifications. To obtain actionable information about phosphorylation-driven signaling cascades, it is essential to identify the kinases responsible for phosphorylating sites that differ across disease states. To fill in these gaps we have developed an unbiased, chemoproteomic approach for identifying high-confidence kinase-substrate interactions with phosphosite specificity. Using this assay, we uncovered the role of cyclin-dependent kinase 4 (CDK4), a clinically validated kinase important for cell-cycle progression, in regulating cap-dependent translation via phosphorylation of the tumor suppressor 4E-BP1. The discovery of this signaling axis sheds light on the mechanisms by which CDK4/6 inhibitors control cell proliferation and constitutes a successful example of kinase discovery using an activity-based, kinase-directed probe.
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Affiliation(s)
- Dylan C Mitchell
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Arya Menon
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109, USA
| | - Amanda L Garner
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109, USA.
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18
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Ahmed AR, Owens RJ, Stubbs CD, Parker AW, Hitchman R, Yadav RB, Dumoux M, Hawes C, Botchway SW. Direct imaging of the recruitment and phosphorylation of S6K1 in the mTORC1 pathway in living cells. Sci Rep 2019; 9:3408. [PMID: 30833605 PMCID: PMC6399282 DOI: 10.1038/s41598-019-39410-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 01/23/2019] [Indexed: 01/11/2023] Open
Abstract
Knowledge of protein signalling pathways in the working cell is seen as a primary route to identifying and developing targeted medicines. In recent years there has been a growing awareness of the importance of the mTOR pathway, making it an attractive target for therapeutic intervention in several diseases. Within this pathway we have focused on S6 kinase 1 (S6K1), the downstream phosphorylation substrate of mTORC1, and specifically identify its juxtaposition with mTORC1. When S6K1 is co-expressed with raptor we show that S6K1 is translocated from the nucleus to the cytoplasm. By developing a novel biosensor we demonstrate in real-time, that phosphorylation and de-phosphorylation of S6K1 occurs mainly in the cytoplasm of living cells. Furthermore, we show that the scaffold protein raptor, that typically recruits mTOR substrates, is not always involved in S6K1 phosphorylation. Overall, we demonstrate how FRET-FLIM imaging technology can be used to show localisation of S6K1 phosphorylation in living cells and hence a key site of action of inhibitors targeting mTOR phosphorylation.
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Affiliation(s)
- Abdullah R Ahmed
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0FA, UK
| | - Raymond J Owens
- Protein Production UK, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0FA, UK.,The Wellcome Centre for Human Genetics, Roosevelt Drive, Oxford, OX3 7BN, UK
| | - Christopher D Stubbs
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0FA, UK
| | - Anthony W Parker
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0FA, UK
| | - Richard Hitchman
- Evotec (UK) Ltd, 114 Innovation Drive, Milton Park, Abingdon, Oxfordshire, OX14 4RZ, UK
| | - Rahul B Yadav
- Evotec (UK) Ltd, 114 Innovation Drive, Milton Park, Abingdon, Oxfordshire, OX14 4RZ, UK
| | - Maud Dumoux
- Protein Production UK, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0FA, UK.,Diamond Light Source, Harwell Campus, Didcot, OX11 0DE, UK
| | - Chris Hawes
- Oxford Brookes University, Headington Campus, Oxford, OX3 0BP, UK
| | - Stanley W Botchway
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0FA, UK.
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19
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Chao LH, Avruch J. Cryo-EM insight into the structure of MTOR complex 1 and its interactions with Rheb and substrates. F1000Res 2019; 8. [PMID: 30647914 PMCID: PMC6325617 DOI: 10.12688/f1000research.16109.1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/18/2018] [Indexed: 12/31/2022] Open
Abstract
The mechanistic target of rapamycin (MTOR) is a giant protein kinase that, together with the accessory proteins Raptor and mLst8, forms a complex of over 1 MDa known as MTOR complex 1 (MTORC1). MTORC1, through its protein kinase activity, controls the accretion of cell mass through the regulation of gene transcription, mRNA translation, and protein turnover. MTORC1 is activated in an interdependent manner by insulin/growth factors and nutrients, especially amino acids, and is inhibited by stressors such as hypoxia and by the drug rapamycin. The action of insulin/growth factors converges on the small GTPase Rheb, which binds directly to the MTOR polypeptide in MTORC1 and, in its GTP-bound state, initiates kinase activation. Biochemical studies established that MTORC1 exists as a dimer of the MTOR/Raptor/mLst8 trimer, and progressive refinements in cryo-electron microscopy (cryo-EM) have enabled an increasingly clear picture of the architecture of MTORC1, culminating in a deep understanding of how MTORC1 interacts with and phosphorylates its best-known substrates-the eIF-4E binding protein/4E-BP, the p70 S6 kinase/S6K1B, and PRAS40/AKT1S1-and how this is inhibited by rapamycin. Most recently, Rheb-GTP has been shown to bind to MTORC1 in a cooperative manner at an allosteric site remote from the kinase domain that twists the latter into a catalytically competent configuration. Herein, we review the recent cryo-EM and associated biochemical studies of MTORC1 and seek to integrate these new results with the known physiology of MTORC1 regulation and signaling.
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Affiliation(s)
- Luke H Chao
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Joseph Avruch
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
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20
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Reappraisal to the study of 4E-BP1 as an mTOR substrate – A normative critique. Eur J Cell Biol 2017; 96:325-336. [DOI: 10.1016/j.ejcb.2017.03.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/31/2017] [Accepted: 03/31/2017] [Indexed: 12/20/2022] Open
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21
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Stuttfeld E, Imseng S, Maier T. A central role for a region in the middle. eLife 2017; 6. [PMID: 28266914 PMCID: PMC5340523 DOI: 10.7554/elife.25700] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 03/03/2017] [Indexed: 11/26/2022] Open
Abstract
A domain called the 'Conserved region in the middle' is responsible for target recognition in the TORC2 complex in fission yeast and the mTORC2 complex in mammals.
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Affiliation(s)
| | | | - Timm Maier
- Biozentrum, University of Basel, Basel, Switzerland
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22
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Ji S, Lin W, Wang L, Ni Z, Jin F, Zha X, Fei G. Combined Targeting of mTOR and Akt Using Rapamycin and MK-2206 in The Treatment of Tuberous Sclerosis Complex. J Cancer 2017; 8:555-562. [PMID: 28367235 PMCID: PMC5370499 DOI: 10.7150/jca.17205] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 10/29/2016] [Indexed: 12/11/2022] Open
Abstract
Tuberous sclerosis complex (TSC), caused by loss-of-function mutations in the TSC1 or TSC2 genes, is an autosomal dominant disease characterized by benign tumor formation in multiple organs. Hyperactivation of mammalian target of rapamycin (mTOR) is the primary alteration underlying TSC tumor. Thus, rapamycin, as an mTOR specific inhibitor, has been assumed as a potential drug for the treatment of TSC. However, its application in TSC patients has been limited due to side effects. By analyzing Tsc1- or Tsc2-null mouse embryonic fibroblasts (MEFs), we found that loss of TSC1 or TSC2 led to a decreased sensitivity to MK-2206, a novel allosteric Akt inhibitor. Ectopic expression of a constitutively activated Akt (myristoylated Akt-1, myrAkt-1) sensitized Tsc2-null and Tsc1-null MEFs to MK-2206. Furthermore, MK-2206 increased the cytotoxicity of rapamycin in Tsc1-/- or Tsc2-/- MEFs. Moreover, the benefit of the combinatorial treatment was also demonstrated in a TSC xenograft mouse model. We conclude that the combination of rapamycin and MK-2206 may be utilized as a new therapeutic regimen for TSC.
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Affiliation(s)
- Shuang Ji
- Pulmonary Department, First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China;; Department of Biochemistry & Molecular Biology, School of Basic Medical Sciences, Anhui Medical University, Hefei, Anhui, China
| | - Wei Lin
- Department of Stomatology, First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China;; Department of Prosthodontics, Hospital of Stomatology, Wuhan University, Wuhan, Hubei, China
| | - Li Wang
- Department of Biochemistry & Molecular Biology, School of Basic Medical Sciences, Anhui Medical University, Hefei, Anhui, China
| | - Zhaofei Ni
- Department of Biochemistry & Molecular Biology, School of Basic Medical Sciences, Anhui Medical University, Hefei, Anhui, China
| | - Fuquan Jin
- Department of Biochemistry & Molecular Biology, School of Basic Medical Sciences, Anhui Medical University, Hefei, Anhui, China
| | - Xiaojun Zha
- Department of Biochemistry & Molecular Biology, School of Basic Medical Sciences, Anhui Medical University, Hefei, Anhui, China
| | - Guanghe Fei
- Pulmonary Department, First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China
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23
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Rosenthal MD, Brakenridge S, Rosenthal CM, Moore FA. Nutritional Support in the Setting of Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS). CURRENT SURGERY REPORTS 2016. [DOI: 10.1007/s40137-016-0152-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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24
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Mitotic protein kinase CDK1 phosphorylation of mRNA translation regulator 4E-BP1 Ser83 may contribute to cell transformation. Proc Natl Acad Sci U S A 2016; 113:8466-71. [PMID: 27402756 DOI: 10.1073/pnas.1607768113] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Mammalian target of rapamycin (mTOR)-directed eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) phosphorylation promotes cap-dependent translation and tumorigenesis. During mitosis, cyclin-dependent kinase 1 (CDK1) substitutes for mTOR and fully phosphorylates 4E-BP1 at canonical sites (T37, T46, S65, and T70) and the noncanonical S83 site, resulting in a mitosis-specific hyperphosphorylated δ isoform. Colocalization studies with a phospho-S83 specific antibody indicate that 4E-BP1 S83 phosphorylation accumulates at centrosomes during prophase, peaks at metaphase, and decreases through telophase. Although S83 phosphorylation of 4E-BP1 does not affect general cap-dependent translation, expression of an alanine substitution mutant 4E-BP1.S83A partially reverses rodent cell transformation induced by Merkel cell polyomavirus small T antigen viral oncoprotein. In contrast to inhibitory mTOR 4E-BP1 phosphorylation, these findings suggest that mitotic CDK1-directed phosphorylation of δ-4E-BP1 may yield a gain of function, distinct from translation regulation, that may be important in tumorigenesis and mitotic centrosome function.
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25
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Chong ZZ. Targeting PRAS40 for multiple diseases. Drug Discov Today 2016; 21:1222-31. [PMID: 27086010 DOI: 10.1016/j.drudis.2016.04.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/18/2016] [Accepted: 04/07/2016] [Indexed: 12/19/2022]
Abstract
Proline-rich Akt substrate 40kDa (PRAS40) bridges cell signaling between protein kinase B (Akt) and the mammalian target of rapamycin complex 1 (mTORC1). Both Akt and mTORC1 can phosphorylate PRAS40. As a negative regulator of mTORC1, PRAS40 prevents the binding of mTOR to its substrates. The phosphorylation of PRAS40 results in its dissociation from mTORC1 and enhanced mTOR activation. PRAS40 in conjunction with mTORC1 has been closely associated with programmed cell death and is implicated in diabetes mellitus (DM), cardiovascular diseases, cancer, and neurological diseases. Thus, targeting PRAS40 might hold great promise for innovative therapeutic strategies for these diseases.
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Affiliation(s)
- Zhao Zhong Chong
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, USA; Institute of Materia Medica, Shandong Academy of Medical Sciences, Jinan, China.
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26
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Moberg M, Apró W, Ekblom B, van Hall G, Holmberg HC, Blomstrand E. Activation of mTORC1 by leucine is potentiated by branched-chain amino acids and even more so by essential amino acids following resistance exercise. Am J Physiol Cell Physiol 2016; 310:C874-84. [PMID: 27053525 DOI: 10.1152/ajpcell.00374.2015] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 03/31/2016] [Indexed: 12/31/2022]
Abstract
Protein synthesis is stimulated by resistance exercise and intake of amino acids, in particular leucine. Moreover, activation of mammalian target of rapamycin complex 1 (mTORC1) signaling by leucine is potentiated by the presence of other essential amino acids (EAA). However, the contribution of the branched-chain amino acids (BCAA) to this effect is yet unknown. Here we compare the stimulatory role of leucine, BCAA, and EAA ingestion on anabolic signaling following exercise. Accordingly, eight trained volunteers completed four sessions of resistance exercise during which they ingested either placebo, leucine, BCAA, or EAA (including the BCAA) in random order. Muscle biopsies were taken at rest, immediately after exercise, and following 90 and 180 min of recovery. Following 90 min of recovery the activity of S6 kinase 1 (S6K1) was greater than at rest in all four trials (Placebo<Leucine<BCAA<EAA; P < 0.05 time × supplement), with a ninefold increase in the EAA trial. At this same time point, phosphorylation of eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1) at Thr(37/46) was unaffected by supplementation, while that of Thr(46) alone exhibited a pattern similar to that of S6K1, being 18% higher with EAA than BCAA. However, after 180 min of recovery this difference between EAA and BCAA had disappeared, although with both these supplements the increases were still higher than with leucine (40%, P < 0.05) and placebo (100%, P < 0.05). In summary, EAA ingestion appears to stimulate translation initiation more effectively than the other supplements, although the results also suggest that this effect is primarily attributable to the BCAA.
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Affiliation(s)
- Marcus Moberg
- Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden;
| | - William Apró
- Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Björn Ekblom
- Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Gerrit van Hall
- Clinical Metabolomics Core Facility, Rigshopitalet and Department of Biomedical Sciences, Rigshospitalet, University of Copenhagen, Copenhagen Denmark
| | - Hans-Christer Holmberg
- Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden; and
| | - Eva Blomstrand
- Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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Genome-Wide Analysis of the TORC1 and Osmotic Stress Signaling Network in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2015; 6:463-74. [PMID: 26681516 PMCID: PMC4751564 DOI: 10.1534/g3.115.025882] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The Target of Rapamycin kinase Complex I (TORC1) is a master regulator of cell growth and metabolism in eukaryotes. Studies in yeast and human cells have shown that nitrogen/amino acid starvation signals act through Npr2/Npr3 and the small GTPases Gtr1/Gtr2 (Rags in humans) to inhibit TORC1. However, it is unclear how other stress and starvation stimuli inhibit TORC1, and/or act in parallel with the TORC1 pathway, to control cell growth. To help answer these questions, we developed a novel automated pipeline and used it to measure the expression of a TORC1-dependent ribosome biogenesis gene (NSR1) during osmotic stress in 4700 Saccharomyces cerevisiae strains from the yeast knock-out collection. This led to the identification of 440 strains with significant and reproducible defects in NSR1 repression. The cell growth control and stress response proteins deleted in these strains form a highly connected network, including 56 proteins involved in vesicle trafficking and vacuolar function; 53 proteins that act downstream of TORC1 according to a rapamycin assay—including components of the HDAC Rpd3L, Elongator, and the INO80, CAF-1 and SWI/SNF chromatin remodeling complexes; over 100 proteins involved in signaling and metabolism; and 17 proteins that directly interact with TORC1. These data provide an important resource for labs studying cell growth control and stress signaling, and demonstrate the utility of our new, and easily adaptable, method for mapping gene regulatory networks.
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Chen XL, Serrano D, Mayhue M, Hoebe K, Ilangumaran S, Ramanathan S. GIMAP5 Deficiency Is Associated with Increased AKT Activity in T Lymphocytes. PLoS One 2015; 10:e0139019. [PMID: 26440416 PMCID: PMC4595448 DOI: 10.1371/journal.pone.0139019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 09/07/2015] [Indexed: 01/05/2023] Open
Abstract
Long-term survival of T lymphocytes in quiescent state is essential to maintain their cell numbers in secondary lymphoid organs. In mice and in rats, the loss of functional GTPase of the immune associated nucleotide binding protein 5 (GIMAP5) causes peripheral T lymphopenia due to spontaneous death of T cells. The underlying mechanism responsible for the disruption of quiescence in Gimap5 deficient T cells remains largely unknown. In this study, we show that loss of functional Gimap5 results in increased basal activation of mammalian target of rapamycin (mTOR), independent of protein phosphatase 2A (PP2A) or AMP-activated protein kinase (AMPK). Our results suggest that the constitutive activation of the phosphoinositide 3-kinase (PI3K) pathway may be one of the consequences of the absence of functional GIMAP5.
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Affiliation(s)
- Xi-Lin Chen
- Immunology Division, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, J1H 5N4, Québec, Canada
| | - Daniel Serrano
- Immunology Division, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, J1H 5N4, Québec, Canada
| | - Marian Mayhue
- Immunology Division, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, J1H 5N4, Québec, Canada
| | - Kasper Hoebe
- Department of Pediatrics, Division of Cellular and Molecular Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States of America
| | - Subburaj Ilangumaran
- Immunology Division, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, J1H 5N4, Québec, Canada
- Centre de Recherche Clinique, Université de Sherbrooke, Sherbrooke, J1H 5N4, Québec, Canada
| | - Sheela Ramanathan
- Immunology Division, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, J1H 5N4, Québec, Canada
- Centre de Recherche Clinique, Université de Sherbrooke, Sherbrooke, J1H 5N4, Québec, Canada
- * E-mail:
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29
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Dissociation of eIF4E-binding protein 2 (4E-BP2) from eIF4E independent of Thr37/Thr46 phosphorylation in the ischemic stress response. PLoS One 2015; 10:e0121958. [PMID: 25822952 PMCID: PMC4379021 DOI: 10.1371/journal.pone.0121958] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 02/10/2015] [Indexed: 12/22/2022] Open
Abstract
Eukaryotic initiation factor (eIF) 4E-binding proteins (4E-BPs) are translational repressors that bind specifically to eIF4E and are critical in the control of protein translation. 4E-BP2 is the predominant 4E-BP expressed in the brain, but their role is not well known. Here, we characterized four forms of 4E-BP2 detected by two-dimensional gel electrophoresis (2-DGE) in brain. The form with highest electrophoretic mobility was the main form susceptible to phosphorylation at Thr37/Thr46 sites, phosphorylation that was detected in acidic spots. Cerebral ischemia and subsequent reperfusion induced dephosphorylation and phosphorylation of 4E-BP2 at Thr37/Thr46, respectively. The induced phosphorylation was in parallel with the release of 4E-BP2 from eIF4E, although two of the phosphorylated 4E-BP2 forms were bound to eIF4E. Upon long-term reperfusion, there was a decrease in the binding of 4E-BP2 to eIF4E in cerebral cortex, demonstrated by cap binding assays and 4E-BP2-immunoprecipitation experiments. The release of 4E-BP2 from eIF4E was without changes in 4E-BP2 phosphorylation or other post-translational modification recognized by 2-DGE. These findings demonstrated specific changes in 4E-BP2/eIF4E association dependent and independent of 4E-BP2 phosphorylation. The last result supports the notion that phosphorylation may not be the uniquely regulation for the binding of 4E-BP2 to eIF4E under ischemic stress.
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Szymańska P, Martin KR, MacKeigan JP, Hlavacek WS, Lipniacki T. Computational analysis of an autophagy/translation switch based on mutual inhibition of MTORC1 and ULK1. PLoS One 2015; 10:e0116550. [PMID: 25761126 PMCID: PMC4356596 DOI: 10.1371/journal.pone.0116550] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 12/09/2014] [Indexed: 12/25/2022] Open
Abstract
We constructed a mechanistic, computational model for regulation of (macro)autophagy and protein synthesis (at the level of translation). The model was formulated to study the system-level consequences of interactions among the following proteins: two key components of MTOR complex 1 (MTORC1), namely the protein kinase MTOR (mechanistic target of rapamycin) and the scaffold protein RPTOR; the autophagy-initiating protein kinase ULK1; and the multimeric energy-sensing AMP-activated protein kinase (AMPK). Inputs of the model include intrinsic AMPK kinase activity, which is taken as an adjustable surrogate parameter for cellular energy level or AMP:ATP ratio, and rapamycin dose, which controls MTORC1 activity. Outputs of the model include the phosphorylation level of the translational repressor EIF4EBP1, a substrate of MTORC1, and the phosphorylation level of AMBRA1 (activating molecule in BECN1-regulated autophagy), a substrate of ULK1 critical for autophagosome formation. The model incorporates reciprocal regulation of mTORC1 and ULK1 by AMPK, mutual inhibition of MTORC1 and ULK1, and ULK1-mediated negative feedback regulation of AMPK. Through analysis of the model, we find that these processes may be responsible, depending on conditions, for graded responses to stress inputs, for bistable switching between autophagy and protein synthesis, or relaxation oscillations, comprising alternating periods of autophagy and protein synthesis. A sensitivity analysis indicates that the prediction of oscillatory behavior is robust to changes of the parameter values of the model. The model provides testable predictions about the behavior of the AMPK-MTORC1-ULK1 network, which plays a central role in maintaining cellular energy and nutrient homeostasis.
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Affiliation(s)
- Paulina Szymańska
- College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, University of Warsaw, Warsaw, Poland
| | - Katie R. Martin
- Van Andel Institute, Grand Rapids, Michigan, United States of America
| | | | - William S. Hlavacek
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
- * E-mail: (WSH); (TL)
| | - Tomasz Lipniacki
- Institute of Fundamental Technological Research, Warsaw, Poland
- * E-mail: (WSH); (TL)
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31
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mTOR Signaling in Protein Translation Regulation: Implications in Cancer Genesis and Therapeutic Interventions. Mol Biol Int 2014; 2014:686984. [PMID: 25505994 PMCID: PMC4258317 DOI: 10.1155/2014/686984] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 10/06/2014] [Indexed: 12/29/2022] Open
Abstract
mTOR is a central nutrient sensor that signals a cell to grow and proliferate. Through distinct protein complexes it regulates different levels of available cellular energy substrates required for cell growth. One of the important functions of the complex is to maintain available amino acid pool by regulating protein translation. Dysregulation of mTOR pathway leads to aberrant protein translation which manifests into various pathological states. Our review focuses on the role mTOR signaling plays in protein translation and its physiological role. It also throws some light on available data that show translation dysregulation as a cause of pathological complexities like cancer and the available drugs that target the pathway for cancer treatment.
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32
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Leprivier G, Rotblat B, Khan D, Jan E, Sorensen PH. Stress-mediated translational control in cancer cells. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:845-60. [PMID: 25464034 DOI: 10.1016/j.bbagrm.2014.11.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 10/31/2014] [Accepted: 11/04/2014] [Indexed: 12/22/2022]
Abstract
Tumor cells are continually subjected to diverse stress conditions of the tumor microenvironment, including hypoxia, nutrient deprivation, and oxidative or genotoxic stress. Tumor cells must evolve adaptive mechanisms to survive these conditions to ultimately drive tumor progression. Tight control of mRNA translation is critical for this response and the adaptation of tumor cells to such stress forms. This proceeds though a translational reprogramming process which restrains overall translation activity to preserve energy and nutrients, but which also stimulates the selective synthesis of major stress adaptor proteins. Here we present the different regulatory signaling pathways which coordinate mRNA translation in the response to different stress forms, including those regulating eIF2α, mTORC1 and eEF2K, and we explain how tumor cells hijack these pathways for survival under stress. Finally, mechanisms for selective mRNA translation under stress, including the utilization of upstream open reading frames (uORFs) and internal ribosome entry sites (IRESes) are discussed in the context of cell stress. This article is part of a Special Issue entitled: Translation and Cancer.
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Affiliation(s)
- Gabriel Leprivier
- Department of Molecular Oncology, British Columbia Cancer Research Centre, Vancouver, British Columbia V5Z 1L4, Canada; Department of Pathology, University of British Columbia, Vancouver, British Columbia V6T 2B5, Canada
| | - Barak Rotblat
- Department of Life Science, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Debjit Khan
- Department of Molecular Oncology, British Columbia Cancer Research Centre, Vancouver, British Columbia V5Z 1L4, Canada; Department of Pathology, University of British Columbia, Vancouver, British Columbia V6T 2B5, Canada
| | - Eric Jan
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T1Z3, Canada
| | - Poul H Sorensen
- Department of Molecular Oncology, British Columbia Cancer Research Centre, Vancouver, British Columbia V5Z 1L4, Canada; Department of Pathology, University of British Columbia, Vancouver, British Columbia V6T 2B5, Canada.
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Phosphorylation dynamics of eukaryotic initiation factor 4E binding protein 1 (4E-BP1) is discordant with its potential to interact with eukaryotic initiation factor 4E (eIF4E). Cell Signal 2014; 26:2117-21. [DOI: 10.1016/j.cellsig.2014.06.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 06/19/2014] [Indexed: 11/21/2022]
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Zhang D, Xiang J, Gu Y, Xu W, Xu H, Zu M, Pei D, Zheng J. Inhibition of mammalian target of rapamycin by rapamycin increases the radiosensitivity of esophageal carcinoma Eca109 cells. Oncol Lett 2014; 8:575-581. [PMID: 25009644 PMCID: PMC4081413 DOI: 10.3892/ol.2014.2186] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Accepted: 04/24/2014] [Indexed: 01/18/2023] Open
Abstract
The aim of the present study was to investigate whether radiation induces the mammalian target of rapamycin (Rap) (mTOR) signaling pathway in esophageal carcinoma Eca109 cells, and whether mTOR inhibition by rapamycin increases Eca109 cell radiosensitivity. Changes in the levels of mTOR signaling pathway and DNA damage-repair proteins in Eca109 cells prior to and following radiation were determined. The Eca109 cells were treated with Rap (0, 100, 200 and 400 nmol/l) in combination with radiation (0, 2, 4 and 6 Gy). The cell proliferation inhibition rate was determined by MTT assay. The optimum Rap concentration and radiation dose, which appropriately inhibited cell proliferation, were then selected for further study. An appropriate combination of Rap and radiation for the Eca109 cells was also selected and changes in the mTOR signaling pathway, apoptosis and DNA damage-repair proteins, as well as in cell clone formation, survival curves, the apoptosis rate and radiation-induced DNA damage were determined. The expression of the mTOR signaling pathway and DNA damage-repair proteins were found to increase following the irradiation of the Eca109 cells. In addition, Rap was found to inhibit the mTOR signaling pathway and the expression of the DNA damage-repair proteins. At the same radiation dose, with increasing Rap concentration, the proliferation inhibition rates of the Eca109 cells were found to improve. The clone formation and survival curves of the experimental group were less than those of the control groups. Furthermore, the cell apoptosis rate and expression of cleaved caspase-3 and bax in the experimental group were higher than those of the control groups, whereas the expression of bcl-2 was less than that of the control groups. The radiation-induced DNA damage of the experimental group was greater than that of the control group. The inhibition of mTOR by Rap was found to effectively inhibit the proliferation, survival and radiation-induced DNA damage repair of the Eca109 cells following irradiation, as well as promoting radiation-induced apoptosis, thereby increasing the radiosensitivity of the esophageal carcinoma Eca109 cells.
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Affiliation(s)
- Dejun Zhang
- Department of Interventional Radiology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China
| | - Jie Xiang
- Department of Rehabilitation Medicine, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China
| | - Yuming Gu
- Department of Interventional Radiology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China
| | - Wei Xu
- Department of Interventional Radiology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China
| | - Hao Xu
- Department of Interventional Radiology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China
| | - Maoheng Zu
- Department of Interventional Radiology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China
| | - Dongsheng Pei
- Jiangsu Key Laboratory of Biological Cancer Therapy, Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China
| | - Junnian Zheng
- Jiangsu Key Laboratory of Biological Cancer Therapy, Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China
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Dysregulation of the IGF-I/PI3K/AKT/mTOR signaling pathway in autism spectrum disorders. Int J Dev Neurosci 2014; 35:35-41. [PMID: 24662006 DOI: 10.1016/j.ijdevneu.2014.03.006] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 03/13/2014] [Accepted: 03/13/2014] [Indexed: 11/20/2022] Open
Abstract
The IGF-I/PI3K/AKT/mTOR signaling pathway plays an important role in the regulation of cell growth, proliferation, differentiation, motility, survival, metabolism and protein synthesis. Insulin-like growth factor-I (IGF-I) is synthesized in the liver and fibroblasts, and its biological actions are mediated by the IGF-I receptor (IGF-IR). The binding of IGF-I to IGF-IR leads to the activation of phosphatidylinositol 3-kinase (PI3K). Activated PI3K stimulates the production of phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] and phosphatidylinositol (3,4,5)-trisphosphate [PI(3,4,5)P3]. The PH domain of AKT (protein kinase B, PKB) (v-AKT murine thymoma viral oncogene homolog) binds to PI(4,5)P2 and PI(3,4,5)P3, followed by phosphorylation of the Thr308 and Ser473 regulatory sites. Tuberous sclerosis complex 1 (TSC1) and TSC2 are upstream regulators of mammalian target of rapamycin (mTOR) and downstream effectors of the PI3K/AKT signaling pathway. The activation of AKT suppresses the TSC1/TSC2 heterodimer, which is an upstream regulator of mTOR. Dysregulated IGF-I/PI3K/AKT/mTOR signaling has been shown to be associated with autism spectrum disorders (ASDs). In this review, we discuss the emerging evidence for a functional relationship between the IGF-I/PI3K/AKT/mTOR pathway and ASDs, as well as a possible role of this signaling pathway in the diagnosis and treatment of ASDs.
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36
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Mayer S, Wrenzycki C, Tomek W. Inactivation of mTor arrests bovine oocytes in the metaphase-I stage, despite reversible inhibition of 4E-BP1 phosphorylation. Mol Reprod Dev 2014; 81:363-75. [DOI: 10.1002/mrd.22305] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 01/20/2014] [Indexed: 11/08/2022]
Affiliation(s)
| | - Christine Wrenzycki
- Faculty of Veterinary Medicine; Justus-Liebig-University Giessen, Clinic for Obstetrics, Gynecology and Andrology of Large and Small Animals; Giessen Germany
| | - Wolfgang Tomek
- Faculty of Veterinary Medicine; Justus-Liebig-University Giessen, Clinic for Obstetrics, Gynecology and Andrology of Large and Small Animals; Giessen Germany
- Leibniz-Institute for Farm Animal Biology; Institute for Reproductive Biology; Dummerstorf Germany
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37
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Moolthiya P, Tohtong R, Keeratichamroen S, Leelawat K. Role of mTOR inhibitor in cholangiocarcinoma cell progression. Oncol Lett 2014; 7:854-860. [PMID: 24527093 PMCID: PMC3919862 DOI: 10.3892/ol.2014.1799] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 11/29/2013] [Indexed: 12/29/2022] Open
Abstract
Cholangiocarcinoma (CCA) is a lethal malignancy of the biliary epithelium. CCA is resistant to currently available chemotherapy; therefore, new drugs as well as new molecular targets must be identified for the development of an effective treatment for CCA. The present study showed that RAD001 (everolimus), a derivative of rapamycin and an orally bioavailable mammalian target of rapamycin (mTOR) inhibitor, exhibits cytotoxic and antimetastatic effects in a CCA cell line, RMCCA-1. Treatment with low concentrations of RAD001 resulted in a significant reduction of in vitro invasion and migration of RMCCA-1, concomitant with a reduction of filopodia and alteration of the actin cytoskeleton. Although, matrix metalloproteinase-9 and -14 activities were unaltered. However, at high concentrations, RAD001 exhibited cytotoxic effects, reducing cell proliferation and inducing apoptotic cell death. Overall, RAD001 exhibits multiple effects mediated by the inhibition of the mTOR, which may serve as a promising agent for the treatment of CCA.
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Affiliation(s)
- Penpak Moolthiya
- Department of Biochemistry, Faculty of Science, Mahidol University, Rajathevi, Bangkok 10400, Thailand
| | - Rutaiwan Tohtong
- Department of Biochemistry, Faculty of Science, Mahidol University, Rajathevi, Bangkok 10400, Thailand
| | - Siriporn Keeratichamroen
- Department of Molecular Medicine, Faculty of Science, Mahidol University, Rajathevi, Bangkok 10400, Thailand
| | - Kawin Leelawat
- Department of Surgery, Rajavithi Hospital, Rajathevi, Bangkok 10400, Thailand
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38
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Liu Y, Vertommen D, Rider MH, Lai YC. Mammalian target of rapamycin-independent S6K1 and 4E-BP1 phosphorylation during contraction in rat skeletal muscle. Cell Signal 2013; 25:1877-86. [PMID: 23707523 DOI: 10.1016/j.cellsig.2013.05.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 05/07/2013] [Indexed: 11/18/2022]
Abstract
Muscle protein synthesis rates decrease during contraction/exercise, but rapidly increase post-exercise. Previous studies mainly focused on signaling pathways that control protein synthesis during post-exercise recovery, such as mTOR and its downstream targets S6K1 and 4E-BP1. In this study, we investigated the effect of high-frequency electrical stimulation on the phosphorylation state of signaling components controlling protein synthesis in rat skeletal muscle. Electrical stimulation increased S6K1 Thr389 phosphorylation, which was unaffected by Torin1, a selective mTOR inhibitor, suggesting that S6K1 phosphorylation by contraction was mTOR-independent. Phosphorylation of eIF4B Ser422 was also increased during electrical stimulation, which was abrogated by inhibition of MEK/ERK/RSK1 activation. Moreover, although phosphorylation of conventional mTOR sites in 4E-BP1 decreased during contraction, mTOR-independent phosphorylation was also apparent, which was associated with the release of 4E-BP1 from eIF4E. The results indicate mTOR-independent phosphorylation of S6K1 and 4E-BP1 and suggest MEK/ERK/RSK1-dependent phosphorylation of eIF4B during skeletal muscle contraction. These phosphorylation events would keep the translation initiation machinery "primed" in an active state so that protein synthesis could quickly resume post-exercise.
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Affiliation(s)
- Yang Liu
- Université catholique de Louvain and de Duve Institute, Avenue Hippocrate 75, B-1200 Brussels, Belgium
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39
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Lee J, Roh KB, Kim SC, Lee J, Park D. Soy peptide-induced stem cell proliferation: involvement of ERK and TGF-β1. J Nutr Biochem 2012; 23:1341-51. [DOI: 10.1016/j.jnutbio.2011.08.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 07/11/2011] [Accepted: 08/15/2011] [Indexed: 01/05/2023]
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40
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Shang ZF, Yu L, Li B, Tu WZ, Wang Y, Liu XD, Guan H, Huang B, Rang WQ, Zhou PK. 4E-BP1 participates in maintaining spindle integrity and genomic stability via interacting with PLK1. Cell Cycle 2012; 11:3463-71. [PMID: 22918237 PMCID: PMC3466556 DOI: 10.4161/cc.21770] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The essential function of eIF4E-binding protein 1 (4E-BP1) in translation initiation has been well established; however, the role of 4E-BP1 in normal cell cycle progression is coming to attention. Here, we revealed the role of 4E-BP1 on mitotic regulation and chromosomal DNA dynamics during mitosis. First, we have observed the co-localization of the phosphorylated 4E-BP1 at T37/46 with Polo-like kinase 1 (PLK1) at the centrosomes during. Depression of 4E-BP1 by small interfering RNA in HepG2 or HeLa cells resulted in an increased outcome of polyploidy and aberrant mitosis, including chromosomal DNA misaligned and multi-polar spindles or multiple centrosomes. We observed that 4E-BP1 interacted with PLK1 directly in vitro and in vivo in mitotic cells, and the C-terminal aa 77-118 of 4E-BP1 mediates its interaction with PLK1. PLK1 can phosphorylate 4E-BP1 in vitro. Furthermore, the depletion of 4E-BP1 sensitized HepG2 and HeLa cells to the microtubule disruption agent paclitaxel. These results demonstrate that 4E-BP1, beyond its role in translation regulation, can function as a regulator of mitosis via interacting with PLK1, and possibly plays a role in genomic stability maintaining.
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Affiliation(s)
- Zeng-Fu Shang
- Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine; Beijing, PR China
| | - Lan Yu
- Division of Molecular Radiation Biology; Department of Radiation Oncology; University of Texas Southwestern Medical Center at Dallas; Dallas, TX USA
| | - Bing Li
- Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine; Beijing, PR China
| | - Wen-Zhi Tu
- Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine; Beijing, PR China
- Institute for Environmental Medicine and Radiation Hygiene; The College of Public Health; University of South China; Hengyang, PR China
| | - Yu Wang
- Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine; Beijing, PR China
| | - Xiao-Dan Liu
- Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine; Beijing, PR China
| | - Hua Guan
- Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine; Beijing, PR China
| | - Bo Huang
- Institute for Environmental Medicine and Radiation Hygiene; The College of Public Health; University of South China; Hengyang, PR China
| | - Wei-Qing Rang
- Institute for Environmental Medicine and Radiation Hygiene; The College of Public Health; University of South China; Hengyang, PR China
| | - Ping-Kun Zhou
- Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine; Beijing, PR China
- Institute for Environmental Medicine and Radiation Hygiene; The College of Public Health; University of South China; Hengyang, PR China
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41
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Wollenhaupt K, Brüssow KP, Albrecht D, Tomek W. The eIF4E repressor protein 4E-BP2 is merely truncated, despite 4E-BP1 degradation in the porcine uterine tissue during implantation. Mol Reprod Dev 2012; 79:767-76. [DOI: 10.1002/mrd.22108] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 08/27/2012] [Indexed: 11/08/2022]
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Loganathan S, Kandala PK, Gupta P, Srivastava SK. Inhibition of EGFR-AKT axis results in the suppression of ovarian tumors in vitro and in preclinical mouse model. PLoS One 2012; 7:e43577. [PMID: 22952709 PMCID: PMC3428303 DOI: 10.1371/journal.pone.0043577] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 07/26/2012] [Indexed: 12/22/2022] Open
Abstract
Ovarian cancer is the leading cause of cancer related deaths in women. Genetic alterations including overexpression of EGFR play a crucial role in ovarian carcinogenesis. Here we evaluated the effect of phenethyl isothiocyanate (PEITC) in ovarian tumor cells in vitro and in vivo. Oral administration of 12 µmol PEITC resulted in drastically suppressing ovarian tumor growth in a preclinical mouse model. Our in vitro studies demonstrated that PEITC suppress the growth of SKOV-3, OVCAR-3 and TOV-21G human ovarian cancer cells by inducing apoptosis in a concentration-dependent manner. Growth inhibitory effects of PEITC were mediated by inhibition of EGFR and AKT, which are known to be overexpressed in ovarian tumors. PEITC treatment caused significant down regulation of constitutive protein levels as well as phosphorylation of EGFR at Tyr1068 in various ovarian cancer cells. In addition, PEITC treatment drastically reduced the phosphorylation of AKT which is downstream to EGFR and disrupted mTOR signaling. PEITC treatment also inhibited the kinase activity of AKT as observed by the down regulation of p-GSK in OVCAR-3 and TOV-21G cells. AKT overexpression or TGF treatment blocked PEITC induced apoptosis in ovarian cancer cells. These results suggest that PEITC targets EGFR/AKT pathway in our model. In conclusion, our study suggests that PEITC could be used alone or in combination with other therapeutic agents to treat ovarian cancer.
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Affiliation(s)
- Sivakumar Loganathan
- Department of Pharmacology and University of Pittsburgh Cancer Institute, University of Pittsburgh, Pennsylvania, United States of America
| | - Prabodh K. Kandala
- Department of Biomedical Sciences and Cancer Biology Center, Texas Tech University Health Sciences Center, Amarillo, Texas, United States of America
| | - Parul Gupta
- Department of Biomedical Sciences and Cancer Biology Center, Texas Tech University Health Sciences Center, Amarillo, Texas, United States of America
| | - Sanjay K. Srivastava
- Department of Pharmacology and University of Pittsburgh Cancer Institute, University of Pittsburgh, Pennsylvania, United States of America
- Department of Biomedical Sciences and Cancer Biology Center, Texas Tech University Health Sciences Center, Amarillo, Texas, United States of America
- * E-mail:
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43
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Abstract
The recent development of mammalian target of rapamycin (mTOR) kinase domain inhibitors and genetic dissection of rapamycin-sensitive and -insensitive mTOR protein complexes (mTORC1 and mTORC2) have revealed that phosphorylation of the mTOR substrate 4E-BP1 on amino acids Thr37 and/or Thr46 represents a rapamycin-insensitive activity of mTORC1. Despite numerous previous reports utilizing serine (Ser)-to-alanine (Ala) and threonine (Thr)-to-Ala phosphorylation site mutants of 4E-BP1 to assess which post-translational modification(s) directly regulate binding to eIF4E, an ambiguous understanding persists. This manuscript demonstrates that the initial, rapamycin-insensitive phosphorylation event at Thr46 is sufficient to prevent eIF4E:4E-BP1 binding. This finding is relevant, particularly as mTOR kinase domain inhibitors continue to be assessed for clinical efficacy, since it clarifies a difference between the action of these second-generation mTOR inhibitors and those of rapamycin analogues.
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Affiliation(s)
- Mark Livingstone
- Biochemistry and McGill Cancer Centre, McGill University, Montreal, Canada ; Cytokine Signalling Unit, Institut Pasteur, Paris, France
| | - Michael Bidinosti
- Biochemistry and McGill Cancer Centre, McGill University, Montreal, Canada
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44
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Roczniak-Ferguson A, Petit CS, Froehlich F, Qian S, Ky J, Angarola B, Walther TC, Ferguson SM. The transcription factor TFEB links mTORC1 signaling to transcriptional control of lysosome homeostasis. Sci Signal 2012; 5:ra42. [PMID: 22692423 DOI: 10.1126/scisignal.2002790] [Citation(s) in RCA: 918] [Impact Index Per Article: 76.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Lysosomes are the major cellular site for clearance of defective organelles and digestion of internalized material. Demand on lysosomal capacity can vary greatly, and lysosomal function must be adjusted to maintain cellular homeostasis. Here, we identified an interaction between the lysosome-localized mechanistic target of rapamycin complex 1 (mTORC1) and the transcription factor TFEB (transcription factor EB), which promotes lysosome biogenesis. When lysosomal activity was adequate, mTOR-dependent phosphorylation of TFEB on Ser(211) triggered the binding of 14-3-3 proteins to TFEB, resulting in retention of the transcription factor in the cytoplasm. Inhibition of lysosomal function reduced the mTOR-dependent phosphorylation of TFEB, resulting in diminished interactions between TFEB and 14-3-3 proteins and the translocation of TFEB into the nucleus, where it could stimulate genes involved in lysosomal biogenesis. These results identify TFEB as a target of mTOR and suggest a mechanism for matching the transcriptional regulation of genes encoding proteins of autophagosomes and lysosomes to cellular need. The closely related transcription factors MITF (microphthalmia transcription factor) and TFE3 (transcription factor E3) also localized to lysosomes and accumulated in the nucleus when lysosome function was inhibited, thus broadening the range of physiological contexts under which this regulatory mechanism may prove important.
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45
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Licursi M, Komatsu Y, Pongnopparat T, Hirasawa K. Promotion of viral internal ribosomal entry site-mediated translation under amino acid starvation. J Gen Virol 2012; 93:951-962. [DOI: 10.1099/vir.0.040386-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cap-dependent and internal ribosomal entry site (IRES)-mediated translation are regulated differently within cells. Viral IRES-mediated translation often remains active when cellular cap-dependent translation is severely impaired under cellular stresses induced by virus infection. To investigate how cellular stresses influence the efficiency of viral IRES-mediated translation, we used a bicistronic luciferase reporter construct harbouring IRES elements from the following viruses: encephalomyocarditis virus (EMCV), foot-and-mouth disease virus (FMDV), hepatitis C virus (HCV) or human rhinovirus (HRV). NIH3T3 cells transfected with these bicistronic reporter constructs were subjected to different cellular stresses. Increased translation initiation was only observed under amino acid starvation when EMCV or FMDV IRES elements were present. To identify cellular mechanisms that promoted viral IRES-mediated translation, we tested the involvement of eukaryotic initiation factor 4E-binding protein (4E-BP), general control non-depressed 2 (GCN2) and eukaryotic initiation factor 2B (eIF2B), as these are known to be modulated under amino acid starvation. Knockdown of 4E-BP1 impaired the promotion of EMCV and FMDV IRES-mediated translation under amino acid starvation, whereas GCN2 and eIF2B were not involved. To further investigate how 4E-BP1 regulates translation initiated by EMCV and FMDV IRES elements, we used a phosphoinositide kinase-3 inhibitor (LY294002), an mTOR inhibitor (Torin1) or leucine starvation to mimic 4E-BP1 dephosphorylation induced by amino acid starvation. 4E-BP1 dephosphorylation induced by the treatments was not sufficient to promote viral IRES-mediated translation. These results suggest that 4E-BP1 regulates EMCV and FMDV IRES-mediated translation under amino acid starvation, but not via its dephosphorylation.
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Affiliation(s)
- Maria Licursi
- Division of Biomedical Science, Faculty of Medicine, Memorial University of Newfoundland, 300 Prince Philip Drive, St John’s, NL A1B 3V6, Canada
| | - Yumiko Komatsu
- Division of Biomedical Science, Faculty of Medicine, Memorial University of Newfoundland, 300 Prince Philip Drive, St John’s, NL A1B 3V6, Canada
| | - Theerawat Pongnopparat
- Division of Biomedical Science, Faculty of Medicine, Memorial University of Newfoundland, 300 Prince Philip Drive, St John’s, NL A1B 3V6, Canada
| | - Kensuke Hirasawa
- Division of Biomedical Science, Faculty of Medicine, Memorial University of Newfoundland, 300 Prince Philip Drive, St John’s, NL A1B 3V6, Canada
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46
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Martineau Y, Azar R, Bousquet C, Pyronnet S. Anti-oncogenic potential of the eIF4E-binding proteins. Oncogene 2012; 32:671-7. [DOI: 10.1038/onc.2012.116] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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47
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Wang H, Cheng H, Wang K, Wen T. Different effects of histone deacetylase inhibitors nicotinamide and trichostatin A (TSA) in C17.2 neural stem cells. J Neural Transm (Vienna) 2012; 119:1307-15. [PMID: 22407380 DOI: 10.1007/s00702-012-0786-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 02/26/2012] [Indexed: 12/29/2022]
Abstract
Histone deacetylase inhibitors are involved in proliferation, apoptosis, cell cycle, mRNA transcription, and protein expression in various cells. However, the molecular mechanism underlying such functions is still not fully clear. In this study, we used C17.2 neural stem cell (NSC) line as a model to evaluate the effects of nicotinamide and trichostatin A (TSA) on cell characteristics. Results show that nicotinamide and TSA greatly inhibit cell growth, lead to cell morphology changes, and effectively induce cell apoptosis in a dose-dependent manner. Western blot analyses confirmed that nicotinamide significantly decreases the expression of bcl-2 and p38. Further insight into the molecular mechanisms shows the suppression of phosphorylation in eukaryotic initiation factor 4E-binding protein 1 (4EBP1) by nicotinamide, whereas, an increased expression of bcl-2 and p38 and phosphorylation of 4EBP1 by TSA. However, both nicotinamide and TSA significantly increase the expression of cytochrome c (cyt c). These results strongly suggest that bcl-2, p38, cyt c, and p-4EBP1 could suppress proliferation and induce apoptosis of C17.2 NSCs mediated by histone deacetylase inhibitors, nicotinamide and TSA, involving different molecular mechanisms.
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Affiliation(s)
- Haifeng Wang
- Laboratory of Molecular Neurobiology, School of Life Sciences, Institute of Systems Biology, Shanghai University, No. 99 Shangda Rd, Shanghai 200444, People's Republic of China.
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48
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Rapley J, Oshiro N, Ortiz-Vega S, Avruch J. The mechanism of insulin-stimulated 4E-BP protein binding to mammalian target of rapamycin (mTOR) complex 1 and its contribution to mTOR complex 1 signaling. J Biol Chem 2011; 286:38043-38053. [PMID: 21914810 DOI: 10.1074/jbc.m111.245449] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Insulin activation of mTOR complex 1 is accompanied by enhanced binding of substrates. We examined the mechanism and contribution of this enhancement to insulin activation of mTORC1 signaling in 293E and HeLa cells. In 293E, insulin increased the amount of mTORC1 retrieved by the transiently expressed nonphosphorylatable 4E-BP[5A] to an extent that varied inversely with the amount of PRAS40 bound to mTORC1. RNAi depletion of PRAS40 enhanced 4E-BP[5A] binding to ∼70% the extent of maximal insulin, and PRAS40 RNAi and insulin together did not increase 4E-BP[5A] binding beyond insulin alone, suggesting that removal of PRAS40 from mTORC1 is the predominant mechanism of an insulin-induced increase in substrate access. As regards the role of increased substrate access in mTORC1 signaling, RNAi depletion of PRAS40, although increasing 4E-BP[5A] binding, did not stimulate phosphorylation of endogenous mTORC1 substrates S6K1(Thr(389)) or 4E-BP (Thr(37)/Thr(46)), the latter already ∼70% of maximal in amino acid replete, serum-deprived 293E cells. In HeLa cells, insulin and PRAS40 RNAi also both enhanced the binding of 4E-BP[5A] to raptor but only insulin stimulated S6K1 and 4E-BP phosphorylation. Furthermore, Rheb overexpression in 293E activated mTORC1 signaling completely without causing PRAS40 release. In the presence of Rheb and insulin, PRAS40 release is abolished by Akt inhibition without diminishing mTORC1 signaling. In conclusion, dissociation of PRAS40 from mTORC1 and enhanced mTORC1 substrate binding results from Akt and mTORC1 activation and makes little or no contribution to mTORC1 signaling, which rather is determined by Rheb activation of mTOR catalytic activity, through mechanisms that remain to be fully elucidated.
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Affiliation(s)
- Joseph Rapley
- Department of Molecular Biology and Diabetes Unit of the Medical Services, Massachusetts General Hospital and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114
| | - Noriko Oshiro
- Department of Molecular Biology and Diabetes Unit of the Medical Services, Massachusetts General Hospital and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114
| | - Sara Ortiz-Vega
- Department of Molecular Biology and Diabetes Unit of the Medical Services, Massachusetts General Hospital and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114
| | - Joseph Avruch
- Department of Molecular Biology and Diabetes Unit of the Medical Services, Massachusetts General Hospital and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114.
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49
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Cohen JD, Gard JMC, Nagle RB, Dietrich JD, Monks TJ, Lau SS. ERK crosstalks with 4EBP1 to activate cyclin D1 translation during quinol-thioether-induced tuberous sclerosis renal cell carcinoma. Toxicol Sci 2011; 124:75-87. [PMID: 21813464 DOI: 10.1093/toxsci/kfr203] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase signaling cascades have been implicated in a number of human cancers. The tumor suppressor gene tuberous sclerosis-2 (Tsc-2) functions as a negative regulator of mTOR. Critical proteins in both pathways are activated following treatment of Eker rats (Tsc-2(EK/+)) with the nephrocarcinogen 2,3,5-tris-(glutathion-S-yl)hydroquinone (TGHQ), which also results in loss of the wild-type allele of Tsc-2 in renal preneoplastic lesions and tumors. Western blot analysis of kidney tumors formed following treatment of Tsc-2(EK/+) rats with TGHQ for 8 months revealed increases in B-Raf, Raf-1, pERK, cyclin D1, 4EBP1, and p-4EBP1-Ser65, -Thr70, and -Thr37/46 expression. Similar changes are observed following TGHQ-mediated transformation of primary renal epithelial cells derived from Tsc-2(EK/+) rats (quinol-thioether rat renal epithelial [QTRRE] cells) that are also null for tuberin. These cells exhibit high ERK, B-Raf, and Raf-1 kinase activity and increased expression of all p-4EBP1s and cyclin D1. Treatment of the QTRRE cells with the Raf kinase inhibitor, sorafenib, or the MEK1/2 kinase inhibitor, PD 98059, produced a significant decrease in the protein expression of all p-4EBP1s and cyclin D1. Following siRNA knockdown of Raf-1, Western blot analysis revealed a significant decrease in Raf-1, cyclin D1, and all p-4EBP1 forms noted above. In contrast, siRNA knockdown of B-Raf resulted in a nominal change in these proteins. The data indicate that Raf-1/MEK/ERK participates in crosstalk with 4EBP1, which represents a novel pathway interaction leading to increased protein synthesis, cell growth, and kidney tumor formation.
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Affiliation(s)
- Jennifer D Cohen
- Southwest Environmental Health Sciences Center, Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ 85721, USA
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50
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Gosselin P, Oulhen N, Jam M, Ronzca J, Cormier P, Czjzek M, Cosson B. The translational repressor 4E-BP called to order by eIF4E: new structural insights by SAXS. Nucleic Acids Res 2010; 39:3496-503. [PMID: 21183464 PMCID: PMC3082885 DOI: 10.1093/nar/gkq1306] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
eIF4E binding protein (4E-BP) inhibits translation of capped mRNA by binding to the initiation factor eIF4E and is known to be mostly or completely unstructured in both free and bound states. Using small angle X-ray scattering (SAXS), we report here the analysis of 4E-BP structure in solution, which reveals that while 4E-BP is intrinsically disordered in the free state, it undergoes a dramatic compaction in the bound state. Our results demonstrate that 4E-BP and eIF4E form a ‘fuzzy complex’, challenging current visions of eIF4E/4E-BP complex regulation.
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Affiliation(s)
- Pauline Gosselin
- UPMC Univ Paris 06, UMR 7150, Mer et Santé, Equipe Traduction Cycle Cellulaire et Développement, Station Biologique de Roscoff, 29680 Roscoff, France.
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