1
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Farooq Z, Kusuma F, Burke P, Dufour CR, Lee D, Tabatabaei N, Toboz P, Radovani E, Greenblatt J, Rehman J, Class J, Khoutorsky A, Fonseca BD, Richner JM, Mercier E, Bourque G, Giguère V, Subramaniam AR, Han J, Tahmasebi S. The amino acid sensor GCN2 suppresses Terminal Oligopyrimidine (TOP) mRNA translation via La-related Protein 1 (LARP1). J Biol Chem 2022; 298:102277. [PMID: 35863436 PMCID: PMC9396407 DOI: 10.1016/j.jbc.2022.102277] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 07/10/2022] [Accepted: 07/11/2022] [Indexed: 11/16/2022] Open
Abstract
La-related protein 1 (LARP1) has been identified as a key translational inhibitor of terminal oligopyrimidine (TOP) mRNAs downstream of the nutrient sensing protein kinase complex, mTORC1. LARP1 exerts this inhibitory effect on TOP mRNA translation by binding to the mRNA cap and the adjacent 5′TOP motif, resulting in the displacement of the cap-binding protein eIF4E from TOP mRNAs. However, the involvement of additional signaling pathway in regulating LARP1-mediated inhibition of TOP mRNA translation is largely unexplored. In the present study, we identify a second nutrient sensing kinase GCN2 that converges on LARP1 to control TOP mRNA translation. Using chromatin-immunoprecipitation followed by massive parallel sequencing (ChIP-seq) analysis of activating transcription factor 4 (ATF4), an effector of GCN2 in nutrient stress conditions, in WT and GCN2 KO mouse embryonic fibroblasts, we determined that LARP1 is a GCN2-dependent transcriptional target of ATF4. Moreover, we identified GCN1, a GCN2 activator, participates in a complex with LARP1 on stalled ribosomes, suggesting a role for GCN1 in LARP1-mediated translation inhibition in response to ribosome stalling. Therefore, our data suggest that the GCN2 pathway controls LARP1 activity via two mechanisms: ATF4-dependent transcriptional induction of LARP1 mRNA and GCN1-mediated recruitment of LARP1 to stalled ribosomes.
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Affiliation(s)
- Zeenat Farooq
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA
| | - Fedho Kusuma
- Soonchunhyang Institute of Medi-bio Science (SIMS), Soonchunhyang University, Cheonan-si, Chungcheongnam-do 31151, Korea
| | - Phillip Burke
- Basic Sciences Division and Computational Biology Section of the Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Catherine R Dufour
- Goodman Cancer Research Centre, McGill University, Montréal, QC, H3A 1A3, Canada
| | - Duckgue Lee
- Soonchunhyang Institute of Medi-bio Science (SIMS), Soonchunhyang University, Cheonan-si, Chungcheongnam-do 31151, Korea
| | - Negar Tabatabaei
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA
| | - Phoenix Toboz
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA
| | - Ernest Radovani
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Jack Greenblatt
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Jalees Rehman
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA
| | - Jacob Class
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, IL, USA
| | - Arkady Khoutorsky
- Department of Anesthesia and Faculty of Dentistry, McGill University, Montreal, QC H3A 0G1, Canada
| | | | - Justin M Richner
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, IL, USA
| | - Eloi Mercier
- Canadian Centre for Computational Genomics, and McGill University and Genome Québec Innovation Center, Montréal, QC H3A 0G1, Canada
| | - Guillaume Bourque
- Canadian Centre for Computational Genomics, and McGill University and Genome Québec Innovation Center, Montréal, QC H3A 0G1, Canada
| | - Vincent Giguère
- Goodman Cancer Research Centre, McGill University, Montréal, QC, H3A 1A3, Canada
| | - Arvind R Subramaniam
- Basic Sciences Division and Computational Biology Section of the Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Jaeseok Han
- Soonchunhyang Institute of Medi-bio Science (SIMS), Soonchunhyang University, Cheonan-si, Chungcheongnam-do 31151, Korea.
| | - Soroush Tahmasebi
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA.
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2
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Jia JJ, Lahr RM, Solgaard MT, Moraes BJ, Pointet R, Yang AD, Celucci G, Graber TE, Hoang HD, Niklaus M, Pena IA, Hollensen AK, Smith EM, Chaker-Margot M, Anton L, Dajadian C, Livingstone M, Hearnden J, Wang XD, Yu Y, Maier T, Damgaard CK, Berman AJ, Alain T, Fonseca BD. mTORC1 promotes TOP mRNA translation through site-specific phosphorylation of LARP1. Nucleic Acids Res 2021; 49:3461-3489. [PMID: 33398329 PMCID: PMC8034618 DOI: 10.1093/nar/gkaa1239] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 11/29/2020] [Accepted: 12/15/2020] [Indexed: 02/06/2023] Open
Abstract
LARP1 is a key repressor of TOP mRNA translation. It binds the m7Gppp cap moiety and the adjacent 5'TOP motif of TOP mRNAs, thus impeding the assembly of the eIF4F complex on these transcripts. mTORC1 controls TOP mRNA translation via LARP1, but the details of the mechanism are unclear. Herein we elucidate the mechanism by which mTORC1 controls LARP1's translation repression activity. We demonstrate that mTORC1 phosphorylates LARP1 in vitro and in vivo, activities that are efficiently inhibited by rapamycin and torin1. We uncover 26 rapamycin-sensitive phospho-serine and -threonine residues on LARP1 that are distributed in 7 clusters. Our data show that phosphorylation of a cluster of residues located proximally to the m7Gppp cap-binding DM15 region is particularly sensitive to rapamycin and regulates both the RNA-binding and the translation inhibitory activities of LARP1. Our results unravel a new model of translation control in which the La module (LaMod) and DM15 region of LARP1, both of which can directly interact with TOP mRNA, are differentially regulated: the LaMod remains constitutively bound to PABP (irrespective of the activation status of mTORC1), while the C-terminal DM15 'pendular hook' engages the TOP mRNA 5'-end to repress translation, but only in conditions of mTORC1 inhibition.
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Affiliation(s)
- Jian-Jun Jia
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Roni M Lahr
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Michael T Solgaard
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Bruno J Moraes
- GABBA PhD Program, Abel Salazar Biomedical Sciences Institute, University of Porto, Porto, Portugal
- PrimerGen Ltd, Viseu, Portugal
| | - Roberta Pointet
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - An-Dao Yang
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Giovanna Celucci
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Tyson E Graber
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Huy-Dung Hoang
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Marius R Niklaus
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Izabella A Pena
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Anne K Hollensen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Ewan M Smith
- Cancer Research UK Beatson Institute, Glasgow, UK
| | | | - Leonie Anton
- Biozentrum, University of Basel, Basel, Switzerland
| | - Christopher Dajadian
- Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montréal, Canada
| | - Mark Livingstone
- Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montréal, Canada
| | - Jaclyn Hearnden
- Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montréal, Canada
| | - Xu-Dong Wang
- Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Yonghao Yu
- Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Timm Maier
- Biozentrum, University of Basel, Basel, Switzerland
| | - Christian K Damgaard
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Andrea J Berman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Tommy Alain
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
| | - Bruno D Fonseca
- Children's Hospital of Eastern Ontario (CHEO) Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Canada
- PrimerGen Ltd, Viseu, Portugal
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3
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Mattijssen S, Kozlov G, Fonseca BD, Gehring K, Maraia RJ. LARP1 and LARP4: up close with PABP for mRNA 3' poly(A) protection and stabilization. RNA Biol 2021; 18:259-274. [PMID: 33522422 PMCID: PMC7928012 DOI: 10.1080/15476286.2020.1868753] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 12/06/2020] [Accepted: 12/17/2020] [Indexed: 02/06/2023] Open
Abstract
La-related proteins (LARPs) share a La motif (LaM) followed by an RNA recognition motif (RRM). Together these are termed the La-module that, in the prototypical nuclear La protein and LARP7, mediates binding to the UUU-3'OH termination motif of nascent RNA polymerase III transcripts. We briefly review La and LARP7 activities for RNA 3' end binding and protection from exonucleases before moving to the more recently uncovered poly(A)-related activities of LARP1 and LARP4. Two features shared by LARP1 and LARP4 are direct binding to poly(A) and to the cytoplasmic poly(A)-binding protein (PABP, also known as PABPC1). LARP1, LARP4 and other proteins involved in mRNA translation, deadenylation, and decay, contain PAM2 motifs with variable affinities for the MLLE domain of PABP. We discuss a model in which these PABP-interacting activities contribute to poly(A) pruning of active mRNPs. Evidence that the SARS-CoV-2 RNA virus targets PABP, LARP1, LARP 4 and LARP 4B to control mRNP activity is also briefly reviewed. Recent data suggests that LARP4 opposes deadenylation by stabilizing PABP on mRNA poly(A) tails. Other data suggest that LARP1 can protect mRNA from deadenylation. This is dependent on a PAM2 motif with unique characteristics present in its La-module. Thus, while nuclear La and LARP7 stabilize small RNAs with 3' oligo(U) from decay, LARP1 and LARP4 bind and protect mRNA 3' poly(A) tails from deadenylases through close contact with PABP.Abbreviations: 5'TOP: 5' terminal oligopyrimidine, LaM: La motif, LARP: La-related protein, LARP1: La-related protein 1, MLLE: mademoiselle, NTR: N-terminal region, PABP: cytoplasmic poly(A)-binding protein (PABPC1), Pol III: RNA polymerase III, PAM2: PABP-interacting motif 2, PB: processing body, RRM: RNA recognition motif, SG: stress granule.
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Affiliation(s)
- Sandy Mattijssen
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | - Guennadi Kozlov
- Department of Biochemistry & Centre for Structural Biology, McGill University, Montreal, Canada
| | | | - Kalle Gehring
- Department of Biochemistry & Centre for Structural Biology, McGill University, Montreal, Canada
| | - Richard J. Maraia
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
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4
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Mattijssen S, Kozlov G, Gaidamakov S, Ranjan A, Fonseca BD, Gehring K, Maraia RJ. The isolated La-module of LARP1 mediates 3' poly(A) protection and mRNA stabilization, dependent on its intrinsic PAM2 binding to PABPC1. RNA Biol 2021; 18:275-289. [PMID: 33292040 PMCID: PMC7928023 DOI: 10.1080/15476286.2020.1860376] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 11/25/2020] [Accepted: 12/01/2020] [Indexed: 12/18/2022] Open
Abstract
The protein domain arrangement known as the La-module, comprised of a La motif (LaM) followed by a linker and RNA recognition motif (RRM), is found in seven La-related proteins: LARP1, LARP1B, LARP3 (La protein), LARP4, LARP4B, LARP6, and LARP7 in humans. Several LARPs have been characterized for their distinct activity in a specific aspect of RNA metabolism. The La-modules vary among the LARPs in linker length and RRM subtype. The La-modules of La protein and LARP7 bind and protect nuclear RNAs with UUU-3' tails from degradation by 3' exonucleases. LARP4 is an mRNA poly(A) stabilization factor that binds poly(A) and the cytoplasmic poly(A)-binding protein PABPC1 (also known as PABP). LARP1 exhibits poly(A) length protection and mRNA stabilization similar to LARP4. Here, we show that these LARP1 activities are mediated by its La-module and dependent on a PAM2 motif that binds PABP. The isolated La-module of LARP1 is sufficient for PABP-dependent poly(A) length protection and mRNA stabilization in HEK293 cells. A point mutation in the PAM2 motif in the La-module impairs mRNA stabilization and PABP binding in vivo but does not impair oligo(A) RNA binding by the purified recombinant La-module in vitro. We characterize the unusual PAM2 sequence of LARP1 and show it may differentially affect stable and unstable mRNAs. The unique LARP1 La-module can function as an autonomous factor to confer poly(A) protection and stabilization to heterologous mRNAs.
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Affiliation(s)
- Sandy Mattijssen
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | - Guennadi Kozlov
- Department of Biochemistry & Centre for Structural Biology, McGill University, Montreal, Canada
| | - Sergei Gaidamakov
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | - Amitabh Ranjan
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | | | - Kalle Gehring
- Department of Biochemistry & Centre for Structural Biology, McGill University, Montreal, Canada
| | - Richard J. Maraia
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
- Commissioned Corps, U.S. Public Health Service, Rockville, MD, USA
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5
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Cassidy KC, Lahr RM, Kaminsky JC, Mack S, Fonseca BD, Das SR, Berman AJ, Durrant JD. Capturing the Mechanism Underlying TOP mRNA Binding to LARP1. Structure 2019; 27:1771-1781.e5. [PMID: 31676287 PMCID: PMC7269035 DOI: 10.1016/j.str.2019.10.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 08/06/2019] [Accepted: 10/10/2019] [Indexed: 12/20/2022]
Abstract
The RNA-binding protein La-related protein 1 (LARP1) plays a central role in ribosome biosynthesis. Its C-terminal DM15 region binds the 7-methylguanosine (m7G) cap and 5' terminal oligopyrimidine (TOP) motif characteristic of transcripts encoding ribosomal proteins and translation factors. Under the control of mammalian target of rapamycin complex 1 (mTORC1), LARP1 regulates translation of these transcripts. Characterizing the dynamics of DM15-TOP recognition is essential to understanding this fundamental biological process. We use molecular dynamics simulations, biophysical assays, and X-ray crystallography to reveal the mechanism of DM15 binding to TOP transcripts. Residues C-terminal to the m7G-binding site play important roles in cap recognition. Furthermore, we show that the unusually static pocket that recognizes the +1 cytosine characteristic of TOP transcripts drives binding specificity. Finally, we demonstrate that the DM15 pockets involved in TOP-specific m7GpppC-motif recognition are likely druggable. Collectively, these studies suggest unique opportunities for further pharmacological development.
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Affiliation(s)
- Kevin C Cassidy
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Roni M Lahr
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jesse C Kaminsky
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Stephanie Mack
- Department of Chemistry and Center for Nucleic Acids Science & Technology, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - Bruno D Fonseca
- Children's Hospital of Eastern Ontario Research Institute, 401 Smyth Road, Ottawa, K1H 8L1 ON, Canada
| | - Subha R Das
- Department of Chemistry and Center for Nucleic Acids Science & Technology, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - Andrea J Berman
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA.
| | - Jacob D Durrant
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA.
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6
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Fonseca BD, Lahr RM, Damgaard CK, Alain T, Berman AJ. LARP1 on TOP of ribosome production. Wiley Interdiscip Rev RNA 2018; 9:e1480. [PMID: 29722158 DOI: 10.1002/wrna.1480] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 03/06/2018] [Accepted: 03/07/2018] [Indexed: 12/27/2022]
Abstract
The ribosome is an essential unit of all living organisms that commands protein synthesis, ultimately fuelling cell growth (accumulation of cell mass) and cell proliferation (increase in cell number). The eukaryotic ribosome consists of 4 ribosomal RNAs (rRNAs) and 80 ribosomal proteins (RPs). Despite its fundamental role in every living organism, our present understanding of how higher eukaryotes produce the various ribosome components is incomplete. Uncovering the mechanisms utilized by human cells to generate functional ribosomes will likely have far-reaching implications in human disease. Recent biochemical and structural studies revealed La-related protein 1 (LARP1) as a key new player in RP production. LARP1 is an RNA-binding protein that belongs to the LARP superfamily; it controls the translation and stability of the mRNAs that encode RPs and translation factors, which are characterized by a 5' terminal oligopyrimidine (5'TOP) motif and are thus known as TOP mRNAs. The activity of LARP1 is regulated by the mammalian target of rapamycin complex 1 (mTORC1): a eukaryotic protein kinase complex that integrates nutrient sensing with mRNA translation, particularly that of TOP mRNAs. In this review, we provide an overview of the role of LARP1 in the control of ribosome production in multicellular eukaryotes. This article is categorized under: Translation > Translation Regulation RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA Processing > Capping and 5' End Modifications.
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Affiliation(s)
- Bruno D Fonseca
- Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | - Roni M Lahr
- University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | | | - Tommy Alain
- Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | - Andrea J Berman
- University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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7
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Lahr RM, Fonseca BD, Ciotti GE, Al-Ashtal HA, Jia JJ, Niklaus MR, Blagden SP, Alain T, Berman AJ. La-related protein 1 (LARP1) binds the mRNA cap, blocking eIF4F assembly on TOP mRNAs. eLife 2017. [PMID: 28379136 DOI: 10.7554/elife.24146.] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The 5'terminal oligopyrimidine (5'TOP) motif is a cis-regulatory RNA element located immediately downstream of the 7-methylguanosine [m7G] cap of TOP mRNAs, which encode ribosomal proteins and translation factors. In eukaryotes, this motif coordinates the synchronous and stoichiometric expression of the protein components of the translation machinery. La-related protein 1 (LARP1) binds TOP mRNAs, regulating their stability and translation. We present crystal structures of the human LARP1 DM15 region in complex with a 5'TOP motif, a cap analog (m7GTP), and a capped cytidine (m7GpppC), resolved to 2.6, 1.8 and 1.7 Å, respectively. Our binding, competition, and immunoprecipitation data corroborate and elaborate on the mechanism of 5'TOP motif binding by LARP1. We show that LARP1 directly binds the cap and adjacent 5'TOP motif of TOP mRNAs, effectively impeding access of eIF4E to the cap and preventing eIF4F assembly. Thus, LARP1 is a specialized TOP mRNA cap-binding protein that controls ribosome biogenesis.
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Affiliation(s)
- Roni M Lahr
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, United States
| | - Bruno D Fonseca
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Gabrielle E Ciotti
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, United States
| | - Hiba A Al-Ashtal
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, United States
| | - Jian-Jun Jia
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Marius R Niklaus
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Sarah P Blagden
- Department of Oncology, University of Oxford, Oxford, United Kingdom
| | - Tommy Alain
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Andrea J Berman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, United States
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8
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Lahr RM, Fonseca BD, Ciotti GE, Al-Ashtal HA, Jia JJ, Niklaus MR, Blagden SP, Alain T, Berman AJ. La-related protein 1 (LARP1) binds the mRNA cap, blocking eIF4F assembly on TOP mRNAs. eLife 2017; 6:e24146. [PMID: 28379136 PMCID: PMC5419741 DOI: 10.7554/elife.24146] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Accepted: 04/04/2017] [Indexed: 01/07/2023] Open
Abstract
The 5'terminal oligopyrimidine (5'TOP) motif is a cis-regulatory RNA element located immediately downstream of the 7-methylguanosine [m7G] cap of TOP mRNAs, which encode ribosomal proteins and translation factors. In eukaryotes, this motif coordinates the synchronous and stoichiometric expression of the protein components of the translation machinery. La-related protein 1 (LARP1) binds TOP mRNAs, regulating their stability and translation. We present crystal structures of the human LARP1 DM15 region in complex with a 5'TOP motif, a cap analog (m7GTP), and a capped cytidine (m7GpppC), resolved to 2.6, 1.8 and 1.7 Å, respectively. Our binding, competition, and immunoprecipitation data corroborate and elaborate on the mechanism of 5'TOP motif binding by LARP1. We show that LARP1 directly binds the cap and adjacent 5'TOP motif of TOP mRNAs, effectively impeding access of eIF4E to the cap and preventing eIF4F assembly. Thus, LARP1 is a specialized TOP mRNA cap-binding protein that controls ribosome biogenesis.
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Affiliation(s)
- Roni M Lahr
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, United States
| | - Bruno D Fonseca
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Gabrielle E Ciotti
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, United States
| | - Hiba A Al-Ashtal
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, United States
| | - Jian-Jun Jia
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Marius R Niklaus
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Sarah P Blagden
- Department of Oncology, University of Oxford, Oxford, United Kingdom
| | - Tommy Alain
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, Canada
| | - Andrea J Berman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, United States
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9
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Tsukumo Y, Alain T, Fonseca BD, Nadon R, Sonenberg N. Translation control during prolonged mTORC1 inhibition mediated by 4E-BP3. Nat Commun 2016; 7:11776. [PMID: 27319316 PMCID: PMC4915159 DOI: 10.1038/ncomms11776] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 04/27/2016] [Indexed: 12/22/2022] Open
Abstract
Targeting mTORC1 is a highly promising strategy in cancer therapy. Suppression of mTORC1 activity leads to rapid dephosphorylation of eIF4E-binding proteins (4E-BP1–3) and subsequent inhibition of mRNA translation. However, how the different 4E-BPs affect translation during prolonged use of mTOR inhibitors is not known. Here we show that the expression of 4E-BP3, but not that of 4E-BP1 or 4E-BP2, is transcriptionally induced during prolonged mTORC1 inhibition in vitro and in vivo. Mechanistically, our data reveal that 4E-BP3 expression is controlled by the transcription factor TFE3 through a cis-regulatory element in the EIF4EBP3 gene promoter. CRISPR/Cas9-mediated EIF4EBP3 gene disruption in human cancer cells mitigated the inhibition of translation and proliferation caused by prolonged treatment with mTOR inhibitors. Our findings show that 4E-BP3 is an important effector of mTORC1 and a robust predictive biomarker of therapeutic response to prolonged treatment with mTOR-targeting drugs in cancer. The eIF4E-binding proteins (4E-BPs) are critical repressors of cap-dependent translation via mTOR, a pathway frequently hyperactivated in cancer. Here the authors show that 4E-BP3 specifically mediates the cap-dependent translation repression and antiproliferative effects of prolonged pharmacological mTOR inhibition.
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Affiliation(s)
- Yoshinori Tsukumo
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Cancer Pavilion 1160 Pine Avenue West, Montreal, Quebec, Canada H3A 1A3
| | - Tommy Alain
- Department of Biochemistry, Microbiology and Immunology, Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, Canada K1H 8L1
| | - Bruno D Fonseca
- Department of Biochemistry, Microbiology and Immunology, Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, Canada K1H 8L1
| | - Robert Nadon
- McGill University and Genome Quebec Innovation Centre, Department of Human Genetics, McGill University, Montreal, Quebec, Canada H3A 1A5
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Cancer Pavilion 1160 Pine Avenue West, Montreal, Quebec, Canada H3A 1A3
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10
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Wang F, Alain T, Szretter KJ, Stephenson K, Pol JG, Atherton MJ, Hoang HD, Fonseca BD, Zakaria C, Chen L, Rangwala Z, Hesch A, Chan ESY, Tuinman C, Suthar MS, Jiang Z, Ashkar AA, Thomas G, Kozma SC, Gale M, Fitzgerald KA, Diamond MS, Mossman K, Sonenberg N, Wan Y, Lichty BD. S6K-STING interaction regulates cytosolic DNA-mediated activation of the transcription factor IRF3. Nat Immunol 2016; 17:514-522. [PMID: 27043414 PMCID: PMC4917298 DOI: 10.1038/ni.3433] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 03/08/2016] [Indexed: 12/17/2022]
Abstract
Cytosolic DNA-mediated activation of the transcription factor IRF3 is a key event in host antiviral responses. Here we found that infection with DNA viruses induced interaction of the metabolic checkpoint kinase mTOR downstream effector and kinase S6K1 and the signaling adaptor STING in a manner dependent on the DNA sensor cGAS. We further demonstrated that the kinase domain, but not the kinase function, of S6K1 was required for the S6K1-STING interaction and that the TBK1 critically promoted this process. The formation of a tripartite S6K1-STING-TBK1 complex was necessary for the activation of IRF3, and disruption of this signaling axis impaired the early-phase expression of IRF3 target genes and the induction of T cell responses and mucosal antiviral immunity. Thus, our results have uncovered a fundamental regulatory mechanism for the activation of IRF3 in the cytosolic DNA pathway.
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Affiliation(s)
- Fuan Wang
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Tommy Alain
- Children’s Hospital of Eastern Ontario Research Institute and Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON K1H 8L1, Canada
| | - Kristy J. Szretter
- Department of Medicine, Molecular Microbiology, Pathology & Immunology, Washington, University School of Medicine, St Louis, MO 63110, United States of America
| | - Kyle Stephenson
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Jonathan G. Pol
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Matthew J. Atherton
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Huy-Dung Hoang
- Children’s Hospital of Eastern Ontario Research Institute and Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON K1H 8L1, Canada
| | - Bruno D. Fonseca
- Children’s Hospital of Eastern Ontario Research Institute and Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON K1H 8L1, Canada
| | - Chadi Zakaria
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
| | - Lan Chen
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Zainab Rangwala
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Adam Hesch
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Eva Sin Yan Chan
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Carly Tuinman
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Mehul S. Suthar
- Department of Pediatrics, Emory Vaccine Center, Emory University, Atlanta, GA 30329, United States of America
| | - Zhaozhao Jiang
- Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, United States of America
| | - Ali A. Ashkar
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - George Thomas
- Department of of Internal Medicine, Division of Hematology/Oncology, University of Cincinnati Medical School, Cincinnati, 45267-0508 OH, United States of America
- Laboratory of Metabolism and Cancer, Catalan Institute of Oncology, ICO, Bellvitge Biomedical Research Institute, IDIBELL, 08908 Barcelona, Spain
- Departament Ciències Fisiològiques II, Facultat de Medicina, Universitat de Barcelona, 08908, Barcelona, Spain
| | - Sara C. Kozma
- Department of of Internal Medicine, Division of Hematology/Oncology, University of Cincinnati Medical School, Cincinnati, 45267-0508 OH, United States of America
- Laboratory of Metabolism and Cancer, Catalan Institute of Oncology, ICO, Bellvitge Biomedical Research Institute, IDIBELL, 08908 Barcelona, Spain
| | - Michael Gale
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, WA98195, United States of America
| | - Katherine A. Fitzgerald
- Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, United States of America
| | - Michael S. Diamond
- Department of Medicine, Molecular Microbiology, Pathology & Immunology, Washington, University School of Medicine, St Louis, MO 63110, United States of America
| | - Karen Mossman
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
| | - Yonghong Wan
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Brian D. Lichty
- McMaster Immunology Research Centre, Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- MG DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
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11
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Fonseca BD, Zakaria C, Jia JJ, Graber TE, Svitkin Y, Tahmasebi S, Healy D, Hoang HD, Jensen JM, Diao IT, Lussier A, Dajadian C, Padmanabhan N, Wang W, Matta-Camacho E, Hearnden J, Smith EM, Tsukumo Y, Yanagiya A, Morita M, Petroulakis E, González JL, Hernández G, Alain T, Damgaard CK. La-related Protein 1 (LARP1) Represses Terminal Oligopyrimidine (TOP) mRNA Translation Downstream of mTOR Complex 1 (mTORC1). J Biol Chem 2015; 290:15996-6020. [PMID: 25940091 PMCID: PMC4481205 DOI: 10.1074/jbc.m114.621730] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 04/27/2015] [Indexed: 12/11/2022] Open
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) is a critical regulator of protein synthesis. The best studied targets of mTORC1 in translation are the eukaryotic initiation factor-binding protein 1 (4E-BP1) and ribosomal protein S6 kinase 1 (S6K1). In this study, we identify the La-related protein 1 (LARP1) as a key novel target of mTORC1 with a fundamental role in terminal oligopyrimidine (TOP) mRNA translation. Recent genome-wide studies indicate that TOP and TOP-like mRNAs compose a large portion of the mTORC1 translatome, but the mechanism by which mTORC1 controls TOP mRNA translation is incompletely understood. Here, we report that LARP1 functions as a key repressor of TOP mRNA translation downstream of mTORC1. Our data show the following: (i) LARP1 associates with mTORC1 via RAPTOR; (ii) LARP1 interacts with TOP mRNAs in an mTORC1-dependent manner; (iii) LARP1 binds the 5'TOP motif to repress TOP mRNA translation; and (iv) LARP1 competes with the eukaryotic initiation factor (eIF) 4G for TOP mRNA binding. Importantly, from a drug resistance standpoint, our data also show that reducing LARP1 protein levels by RNA interference attenuates the inhibitory effect of rapamycin, Torin1, and amino acid deprivation on TOP mRNA translation. Collectively, our findings demonstrate that LARP1 functions as an important repressor of TOP mRNA translation downstream of mTORC1.
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Affiliation(s)
- Bruno D Fonseca
- From the Children's Hospital of Eastern Ontario Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario K1H 8L1, Canada,
| | - Chadi Zakaria
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Jian-Jun Jia
- From the Children's Hospital of Eastern Ontario Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario K1H 8L1, Canada
| | - Tyson E Graber
- From the Children's Hospital of Eastern Ontario Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario K1H 8L1, Canada, the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Yuri Svitkin
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Soroush Tahmasebi
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Danielle Healy
- From the Children's Hospital of Eastern Ontario Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario K1H 8L1, Canada
| | - Huy-Dung Hoang
- From the Children's Hospital of Eastern Ontario Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario K1H 8L1, Canada
| | - Jacob M Jensen
- the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Ilo T Diao
- the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Alexandre Lussier
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Christopher Dajadian
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Niranjan Padmanabhan
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Walter Wang
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Edna Matta-Camacho
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Jaclyn Hearnden
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Ewan M Smith
- the Medical Research Council Toxicology Unit, Hodgkin Building, Lancaster Road, Leicester LE1 9HN, United Kingdom
| | - Yoshinori Tsukumo
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Akiko Yanagiya
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Masahiro Morita
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Emmanuel Petroulakis
- the Department of Biochemistry, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada, Pfizer Canada Inc., Kirkland, Quebec H9J 2M5, Canada, and
| | - Jose L González
- the Division of Basic Science, National Institute of Cancer, 22 San Fernando Ave., Tlalpan, Mexico City 14080, Mexico
| | - Greco Hernández
- the Division of Basic Science, National Institute of Cancer, 22 San Fernando Ave., Tlalpan, Mexico City 14080, Mexico
| | - Tommy Alain
- From the Children's Hospital of Eastern Ontario Research Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario K1H 8L1, Canada,
| | - Christian K Damgaard
- the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark,
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12
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Fonseca BD, Smith EM, Yelle N, Alain T, Bushell M, Pause A. The ever-evolving role of mTOR in translation. Semin Cell Dev Biol 2014; 36:102-12. [PMID: 25263010 DOI: 10.1016/j.semcdb.2014.09.014] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 09/12/2014] [Accepted: 09/15/2014] [Indexed: 02/06/2023]
Abstract
Control of translation allows for the production of stoichiometric levels of each protein in the cell. Attaining such a level of fine-tuned regulation of protein production requires the coordinated temporal and spatial control of numerous cellular signalling cascades impinging on the various components of the translational machinery. Foremost among these is the mTOR signalling pathway. The mTOR pathway regulates both the initiation and elongation steps of protein synthesis through the phosphorylation of numerous translation factors, while simultaneously ensuring adequate folding of nascent polypeptides through co-translational degradation of misfolded proteins. Perhaps most remarkably, mTOR is also a key regulator of the synthesis of ribosomal proteins and translation factors themselves. Two seminal studies have recently shown in translatome analysis that the mTOR pathway preferentially regulates the translation of mRNAs encoding ribosomal proteins and translation factors. Therefore, the role of the mTOR pathway in the control of protein synthesis extends far beyond immediate translational control. By controlling ribosome production (and ultimately ribosome availability), mTOR is a master long-term controller of protein synthesis. Herein, we review the literature spanning the early discoveries of mTOR on translation to the latest advances in our understanding of how the mTOR pathway controls the synthesis of ribosomal proteins.
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Affiliation(s)
- Bruno D Fonseca
- Children's Hospital of Eastern Ontario Research Institute, 401 Smyth Road, Ottawa, ON K1H 8L1, Canada.
| | - Ewan M Smith
- MRC Toxicology Unit, Hodgkin Building, Lancaster Road, Leicester LE1 9HN, UK
| | - Nicolas Yelle
- Children's Hospital of Eastern Ontario Research Institute, 401 Smyth Road, Ottawa, ON K1H 8L1, Canada
| | - Tommy Alain
- Children's Hospital of Eastern Ontario Research Institute, 401 Smyth Road, Ottawa, ON K1H 8L1, Canada
| | - Martin Bushell
- MRC Toxicology Unit, Hodgkin Building, Lancaster Road, Leicester LE1 9HN, UK
| | - Arnim Pause
- Goodman Cancer Research Centre, Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada.
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13
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Alain T, Morita M, Fonseca BD, Yanagiya A, Siddiqui N, Bhat M, Zammit D, Marcus V, Metrakos P, Voyer LA, Gandin V, Liu Y, Topisirovic I, Sonenberg N. eIF4E/4E-BP ratio predicts the efficacy of mTOR targeted therapies. Cancer Res 2012; 72:6468-76. [PMID: 23100465 DOI: 10.1158/0008-5472.can-12-2395] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Active-site mTOR inhibitors (asTORi) hold great promise for targeting dysregulated mTOR signaling in cancer. Because of the multifaceted nature of mTORC1 signaling, identification of reliable biomarkers for the sensitivity of tumors to asTORi is imperative for their clinical implementation. Here, we show that cancer cells acquire resistance to asTORi by downregulating eukaryotic translation initiation factor (eIF4E)-binding proteins (4E-BPs-EIF4EBP1, EIF4EBP2). Loss of 4E-BPs or overexpression of eIF4E renders neoplastic growth and translation of tumor-promoting mRNAs refractory to mTOR inhibition. Conversely, moderate depletion of eIF4E augments the anti-neoplastic effects of asTORi. The anti-proliferative effect of asTORi in vitro and in vivo is therefore significantly influenced by perturbations in eIF4E/4E-BP stoichiometry, whereby an increase in the eIF4E/4E-BP ratio dramatically limits the sensitivity of cancer cells to asTORi. We propose that the eIF4E/4E-BP ratio, rather than their individual protein levels or solely their phosphorylation status, should be considered as a paramount predictive marker for forecasting the clinical therapeutic response to mTOR inhibitors.
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Affiliation(s)
- Tommy Alain
- Department of Biochemistry, SMBD-Jewish General Hospital, Montreal, Quebec, Canada
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14
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Fonseca BD, Diering GH, Bidinosti MA, Dalal K, Alain T, Balgi AD, Forestieri R, Nodwell M, Rajadurai CV, Gunaratnam C, Tee AR, Duong F, Andersen RJ, Orlowski J, Numata M, Sonenberg N, Roberge M. Structure-activity analysis of niclosamide reveals potential role for cytoplasmic pH in control of mammalian target of rapamycin complex 1 (mTORC1) signaling. J Biol Chem 2012; 287:17530-17545. [PMID: 22474287 DOI: 10.1074/jbc.m112.359638] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) signaling is frequently dysregulated in cancer. Inhibition of mTORC1 is thus regarded as a promising strategy in the treatment of tumors with elevated mTORC1 activity. We have recently identified niclosamide (a Food and Drug Administration-approved antihelminthic drug) as an inhibitor of mTORC1 signaling. In the present study, we explored possible mechanisms by which niclosamide may inhibit mTORC1 signaling. We tested whether niclosamide interferes with signaling cascades upstream of mTORC1, the catalytic activity of mTOR, or mTORC1 assembly. We found that niclosamide does not impair PI3K/Akt signaling, nor does it inhibit mTORC1 kinase activity. We also found that niclosamide does not interfere with mTORC1 assembly. Previous studies in helminths suggest that niclosamide disrupts pH homeostasis of the parasite. This prompted us to investigate whether niclosamide affects the pH balance of cancer cells. Experiments in both breast cancer cells and cell-free systems demonstrated that niclosamide possesses protonophoric activity in cells and in vitro. In cells, niclosamide dissipated protons (down their concentration gradient) from lysosomes to the cytosol, effectively lowering cytoplasmic pH. Notably, analysis of five niclosamide analogs revealed that the structural features of niclosamide required for protonophoric activity are also essential for mTORC1 inhibition. Furthermore, lowering cytoplasmic pH by means other than niclosamide treatment (e.g. incubation with propionic acid or bicarbonate withdrawal) recapitulated the inhibitory effects of niclosamide on mTORC1 signaling, lending support to a possible role for cytoplasmic pH in the control of mTORC1. Our data illustrate a potential mechanism for chemical inhibition of mTORC1 signaling involving modulation of cytoplasmic pH.
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Affiliation(s)
- Bruno D Fonseca
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada.
| | - Graham H Diering
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Michael A Bidinosti
- Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Kush Dalal
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Tommy Alain
- Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Aruna D Balgi
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Roberto Forestieri
- Departments of Chemistry and Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Matt Nodwell
- Departments of Chemistry and Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Charles V Rajadurai
- Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Cynthia Gunaratnam
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Andrew R Tee
- Institute of Medical Genetics, Wales College of Medicine, Cardiff University, Heath Park Way, Cardiff CF14 4XN, United Kingdom
| | - Franck Duong
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Raymond J Andersen
- Departments of Chemistry and Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - John Orlowski
- Department of Physiology, 3655 Promenade Sir William Osler, Bellini Building, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Masayuki Numata
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Michel Roberge
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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15
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Balgi AD, Diering GH, Donohue E, Lam KKY, Fonseca BD, Zimmerman C, Numata M, Roberge M. Regulation of mTORC1 signaling by pH. PLoS One 2011; 6:e21549. [PMID: 21738705 PMCID: PMC3126813 DOI: 10.1371/journal.pone.0021549] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 06/01/2011] [Indexed: 11/18/2022] Open
Abstract
Background Acidification of the cytoplasm and the extracellular environment is associated with many physiological and pathological conditions, such as intense exercise, hypoxia and tumourigenesis. Acidification affects important cellular functions including protein synthesis, growth, and proliferation. Many of these vital functions are controlled by mTORC1, a master regulator protein kinase that is activated by various growth-stimulating signals and inactivated by starvation conditions. Whether mTORC1 can also respond to changes in extracellular or cytoplasmic pH and play a role in limiting anabolic processes in acidic conditions is not known. Methodology/Findings We examined the effects of acidifying the extracellular medium from pH 7.4 to 6.4 on human breast carcinoma MCF-7 cells and immortalized mouse embryo fibroblasts. Decreasing the extracellular pH caused intracellular acidification and rapid, graded and reversible inhibition of mTORC1, assessed by measuring the phosphorylation of the mTORC1 substrate S6K. Fibroblasts deleted of the tuberous sclerosis complex TSC2 gene, a major negative regulator of mTORC1, were unable to inhibit mTORC1 in acidic extracellular conditions, showing that the TSC1–TSC2 complex is required for this response. Examination of the major upstream pathways converging on the TSC1–TSC2 complex showed that Akt signaling was unaffected by pH but that the Raf/MEK/ERK pathway was inhibited. Inhibition of MEK with drugs caused only modest mTORC1 inhibition, implying that other unidentified pathways also play major roles. Conclusions This study reveals a novel role for the TSC1/TSC2 complex and mTORC1 in sensing variations in ambient pH. As a common feature of low tissue perfusion, low glucose availability and high energy expenditure, acidic pH may serve as a signal for mTORC1 to downregulate energy-consuming anabolic processes such as protein synthesis as an adaptive response to metabolically stressful conditions.
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Affiliation(s)
- Aruna D. Balgi
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Graham H. Diering
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Elizabeth Donohue
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Karen K. Y. Lam
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Bruno D. Fonseca
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Carla Zimmerman
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Masayuki Numata
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michel Roberge
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
- The Centre for Drug Research and Development, Vancouver, British Columbia, Canada
- * E-mail:
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16
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Fonseca BD, Alain T, Finestone LK, Huang BPH, Rolfe M, Jiang T, Yao Z, Hernandez G, Bennett CF, Proud CG. Pharmacological and genetic evaluation of proposed roles of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK), extracellular signal-regulated kinase (ERK), and p90(RSK) in the control of mTORC1 protein signaling by phorbol esters. J Biol Chem 2011; 286:27111-22. [PMID: 21659537 DOI: 10.1074/jbc.m111.260794] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) links the control of mRNA translation, cell growth, and metabolism to diverse stimuli. Inappropriate activation of mTORC1 can lead to cancer. Phorbol esters are naturally occurring products that act as potent tumor promoters. They activate isoforms of protein kinase C (PKCs) and stimulate the oncogenic MEK/ERK signaling cascade. They also activate mTORC1 signaling. Previous work indicated that mTORC1 activation by the phorbol ester PMA (phorbol 12-myristate 13-acetate) depends upon PKCs and may involve MEK. However, the precise mechanism(s) through which they activate mTORC1 remains unclear. Recent studies have implicated both the ERKs and the ERK-activated 90-kDa ribosomal S6 kinases (p90(RSK)) in activating mTORC1 signaling via phosphorylation of TSC2 (a regulator of mTORC1) and/or the mTORC1 component raptor. However, the relative importance of each of these kinases and phosphorylation events for the activation of mTORC1 signaling is unknown. The recent availability of MEK (PD184352) and p90(RSK) (BI-D1870) inhibitors of improved specificity allowed us to address the roles of these protein kinases in controlling mTORC1 in a variety of human and rodent cell types. In parallel, we used specific shRNAs against p90(RSK1) and p90(RSK2) to further test their roles in regulating mTORC1 signaling. Our data indicate that p90(RSKs) are dispensable for the activation of mTORC1 signaling by phorbol esters in all cell types tested. Our data also reveal striking diversity in the requirements for MEK/ERK in the control of mTORC1 between different cell types, pointing to additional signaling connections between phorbol esters and mTORC1, which do not involve MEK/ERK. This study provides important information for the design of efficient strategies to combat the hyperactivation of mTORC1 signaling by oncogenic pathways.
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Affiliation(s)
- Bruno D Fonseca
- Division of Molecular Physiology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
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Dowling RJO, Topisirovic I, Alain T, Bidinosti M, Fonseca BD, Petroulakis E, Wang X, Larsson O, Selvaraj A, Liu Y, Kozma SC, Thomas G, Sonenberg N. mTORC1-mediated cell proliferation, but not cell growth, controlled by the 4E-BPs. Science 2010; 328:1172-6. [PMID: 20508131 DOI: 10.1126/science.1187532] [Citation(s) in RCA: 547] [Impact Index Per Article: 39.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) integrates mitogen and nutrient signals to control cell proliferation and cell size. Hence, mTORC1 is implicated in a large number of human diseases--including diabetes, obesity, heart disease, and cancer--that are characterized by aberrant cell growth and proliferation. Although eukaryotic translation initiation factor 4E-binding proteins (4E-BPs) are critical mediators of mTORC1 function, their precise contribution to mTORC1 signaling and the mechanisms by which they mediate mTORC1 function have remained unclear. We inhibited the mTORC1 pathway in cells lacking 4E-BPs and analyzed the effects on cell size, cell proliferation, and cell cycle progression. Although the 4E-BPs had no effect on cell size, they inhibited cell proliferation by selectively inhibiting the translation of messenger RNAs that encode proliferation-promoting proteins and proteins involved in cell cycle progression. Thus, control of cell size and cell cycle progression appear to be independent in mammalian cells, whereas in lower eukaryotes, 4E-BPs influence both cell growth and proliferation.
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Affiliation(s)
- Ryan J O Dowling
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
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Dowling RJ, Topisirovic I, Fonseca BD, Sonenberg N. Dissecting the role of mTOR: Lessons from mTOR inhibitors. Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics 2010; 1804:433-9. [DOI: 10.1016/j.bbapap.2009.12.001] [Citation(s) in RCA: 351] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 11/27/2009] [Accepted: 12/01/2009] [Indexed: 12/14/2022]
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Wang X, Fonseca BD, Tang H, Liu R, Elia A, Clemens MJ, Bommer UA, Proud CG. Re-evaluating the roles of proposed modulators of mammalian target of rapamycin complex 1 (mTORC1) signaling. J Biol Chem 2008; 283:30482-92. [PMID: 18676370 DOI: 10.1074/jbc.m803348200] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Signaling through mammalian target of rapamycin complex 1 (mTORC1) is stimulated by amino acids and insulin. Insulin inactivates TSC1/2, the GTPase-activator complex for Rheb, and Rheb.GTP activates mTORC1. It is not clear how amino acids regulate mTORC1. FKBP38 (immunophilin FK506-binding protein, 38 kDa), was recently reported to exert a negative effect on mTORC1 function that is relieved by its binding to Rheb.GTP. We confirm that Rheb binds wild type FKBP38, but inactive Rheb mutants showed contrasting abilities to bind FKBP38. We were unable to observe any regulation of FKBP38/mTOR binding by amino acids or insulin. Furthermore, FKBP38 did not inhibit mTORC1 signaling. The translationally controlled tumor protein (TCTP) in Drosophila was recently reported to act as the guanine nucleotide-exchange factor for Rheb. We have studied the role of TCTP in mammalian TORC1 signaling and its control by amino acids. Reducing TCTP levels did not reproducibly affect mTORC1 signaling in amino acid-replete/insulin-stimulated cells. Moreover, overexpressing TCTP did not rescue mTORC1 signaling in amino acid-starved cells. In addition, we were unable to see any stable interaction between TCTP and Rheb or mTORC1. Accumulation of uncharged tRNA has been previously proposed to be involved in the inhibition of mTORC1 signaling during amino acid starvation. To test this hypothesis, we used a Chinese hamster ovary cell line containing a temperature-sensitive mutation in leucyl-tRNA synthetase. Leucine deprivation markedly inhibited mTORC1 signaling in these cells, but shifting the cells to the nonpermissive temperature for the synthetase did not. These data indicate that uncharged tRNA(Leu) does not switch off mTORC1 signaling and suggest that mTORC1 is controlled by a distinct pathway that senses the availability of amino acids. Our data also indicate that, in the mammalian cell lines tested here, neither TCTP nor FKBP38 regulates mTORC1 signaling.
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Affiliation(s)
- Xuemin Wang
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver V6T 1Z3, Canada
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Lee VHY, Healy T, Fonseca BD, Hayashi A, Proud CG. Analysis of the regulatory motifs in eukaryotic initiation factor 4E-binding protein 1. FEBS J 2008; 275:2185-99. [PMID: 18384376 DOI: 10.1111/j.1742-4658.2008.06372.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) phosphorylates proteins such as eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) and the S6 kinases. These substrates contain short sequences, termed TOR signalling (TOS) motifs, which interact with the mTORC1 component raptor. Phosphorylation of 4E-BP1 requires an additional feature, termed the RAIP motif (Arg-Ala-Ile-Pro). We have analysed the interaction of 4E-BP1 with raptor and the amino acid residues required for functional RAIP and TOS motifs, as assessed by raptor binding and the phosphorylation of 4E-BP1 in human cells. Binding of 4E-BP1 to raptor strongly depends on an intact TOS motif, but the RAIP motif and additional C-terminal features of 4E-BP1 also contribute to this interaction. Mutational analysis of 4E-BP1 reveals that isoleucine is a key feature of the RAIP motif, that proline is also very important and that there is greater tolerance for substitution of the first two residues. Within the TOS motif, the first position (phenylalanine in the known motifs) is most critical, whereas a wider range of residues function in other positions (although an uncharged aliphatic residue is preferred at position three). These data provide important information on the structural requirements for efficient signalling downstream of mTORC1.
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Affiliation(s)
- Vivian H Y Lee
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
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Abstract
There is currently substantial interest in the regulation of cell function by mammalian target of rapamycin (mTOR), especially effects linked to the rapamycin-sensitive mTOR complex 1 (mTORC1). Rapamycin induces G(1) arrest and blocks proliferation of many tumor cells, suggesting that the inhibition of mTORC1 signaling may be useful in cancer therapy. In MCF7 breast adenocarcinoma cells, rapamycin decreases levels of cyclin D1, without affecting cytoplasmic levels of its mRNA. In some cell-types, rapamycin does not affect cyclin D1 levels, whereas the starvation for leucine (which impairs mTORC1 signaling more profoundly than rapamycin) does. This pattern correlates with the behavior of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1, an mTORC1 target that regulates translation initiation). siRNA-mediated knock-down of 4E-BP1 abrogates the effect of rapamycin on cyclin D1 expression and increases the polysomal association of the cyclin D1 mRNA. Our data identify 4E-BP1 as a key regulator of cyclin D1 expression, indicate that this effect is not mediated through the changes in cytoplasmic levels of cyclin D1 mRNA and suggest that, in some cell types, interfering with the amino acid input to mTORC1, rather than using rapamycin, may inhibit proliferation.
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Affiliation(s)
- J Averous
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
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Fonseca BD, Smith EM, Lee VHY, MacKintosh C, Proud CG. PRAS40 is a target for mammalian target of rapamycin complex 1 and is required for signaling downstream of this complex. J Biol Chem 2007; 282:24514-24. [PMID: 17604271 DOI: 10.1074/jbc.m704406200] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signaling through the mammalian target of rapamycin complex 1 (mTORC1) is positively regulated by amino acids and insulin. PRAS40 associates with mTORC1 (which contains raptor) but not mTORC2. PRAS40 interacts with raptor, and this requires an intact TOR-signaling (TOS) motif in PRAS40. Like TOS motif-containing proteins such as eIF4E-binding protein 1 (4E-BP1), PRAS40 is a substrate for phosphorylation by mTORC1. Consistent with this, starvation of cells of amino acids or treatment with rapamycin alters the phosphorylation of PRAS40. PRAS40 binds 14-3-3 proteins, and this requires both amino acids and insulin. Binding of PRAS40 to 14-3-3 proteins is inhibited by TSC1/2 (negative regulators of mTORC1) and stimulated by Rheb in a rapamycin-sensitive manner. This confirms that PRAS40 is a target for regulation by mTORC1. Small interfering RNA-mediated knockdown of PRAS40 impairs both the amino acid- and insulin-stimulated phosphorylation of 4E-BP1 and the phosphorylation of S6. However, this has no effect on the phosphorylation of Akt or TSC2 (an Akt substrate). These data place PRAS40 downstream of mTORC1 but upstream of its effectors, such as S6K1 and 4E-BP1.
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Affiliation(s)
- Bruno D Fonseca
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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Abstract
Several oncogene and tumor-suppressor gene products are known substrates for the calpain family of cysteine proteases, and calpain is required for transformation by v-src and tumor invasion. Thus, we have now addressed whether calpain is generally associated with transformation and how calpain contributes to oncogene function. Our results demonstrate that calpain activity is enhanced upon transformation induced by the v-Src, v-Jun, v-Myc, k-Ras, and v-Fos oncoproteins. Furthermore, elevated calpain activity commonly promotes focal adhesion remodelling, disruption of actin cytoskeleton, morphological transformation, and cell migration, although proteolysis of target substrates (such as focal adhesion kinase, talin, and spectrin) is differently specified by individual oncoproteins. Interestingly, v-Fos differs from other common oncoproteins in not requiring calpain activity for actin/adhesion remodelling or migration of v-Fos transformed cells. However, anchorage-independent growth of all transformed cells is sensitive to calpain inhibition. In addition, elevated calpain activity contributes to oncogene-induced apoptosis associated with transformation by v-Myc. Taken together, these studies demonstrate that calpain activity is necessary for full cellular transformation induced by common oncoproteins, but has distinct roles in oncogenic events induced by individual transforming proteins. Thus, targeting calpain activity may represent a useful general strategy for interfering with activated proto-oncogenes in cancer cells.
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Affiliation(s)
- N O Carragher
- The Beatson Institute for Cancer Research, Cancer Research UK Beatson Laboratories, Glasgow G61 1BD, Scotland, UK.
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