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Ibrahim YH, Pantelios S, Mutvei AP. An affinity tool for the isolation of endogenous active mTORC1 from various cellular sources. J Biol Chem 2023; 299:104644. [PMID: 36965617 PMCID: PMC10164890 DOI: 10.1016/j.jbc.2023.104644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 03/02/2023] [Accepted: 03/13/2023] [Indexed: 03/27/2023] Open
Abstract
The mechanistic target of rapamycin complex 1 (mTORC1) is a central regulator of mammalian cell growth that is dysregulated in a number of human diseases, including metabolic syndromes, aging and cancer. Structural, biochemical and pharmacological studies that have increased our understanding of how mTORC1 executes growth control often relied upon purified mTORC1 protein. However, current immunoaffinity-based purification methods are expensive, inefficient, and do not necessarily isolate endogenous mTORC1, hampering their overall utility in research. Here we present a simple tool to isolate endogenous mTORC1 from various cellular sources. By recombinantly expressing and isolating mTORC1-binding Rag GTPases from E. Coli and using them as affinity probes, we demonstrate that mTORC1 can be isolated from mouse, bovine and human sources. Our results indicate that mTORC1 isolated by this relatively inexpensive method is catalytically active and amenable to scaling. Collectively, this tool may be utilized to isolate mTORC1 from various cellular sources, organs, and disease contexts, aiding mTORC1-related research.
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Affiliation(s)
| | - Spyridon Pantelios
- Department of Immunology, Pathology and Genetics, Uppsala University, Uppsala, Sweden
| | - Anders P Mutvei
- Department of Immunology, Pathology and Genetics, Uppsala University, Uppsala, Sweden.
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2
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Senoo H, Murata D, Wai M, Arai K, Iwata W, Sesaki H, Iijima M. KARATE: PKA-induced KRAS4B-RHOA-mTORC2 supercomplex phosphorylates AKT in insulin signaling and glucose homeostasis. Mol Cell 2021; 81:4622-4634.e8. [PMID: 34551282 DOI: 10.1016/j.molcel.2021.09.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 06/06/2021] [Accepted: 08/30/2021] [Indexed: 01/22/2023]
Abstract
AKT is a serine/threonine kinase that plays an important role in metabolism, cell growth, and cytoskeletal dynamics. AKT is activated by two kinases, PDK1 and mTORC2. Although the regulation of PDK1 is well understood, the mechanism that controls mTORC2 is unknown. Here, by investigating insulin receptor signaling in human cells and biochemical reconstitution, we found that insulin induces the activation of mTORC2 toward AKT by assembling a supercomplex with KRAS4B and RHOA GTPases, termed KARATE (KRAS4B-RHOA-mTORC2 Ensemble). Insulin-induced KARATE assembly is controlled via phosphorylation of GTP-bound KRAS4B at S181 and GDP-bound RHOA at S188 by protein kinase A. By developing a KARATE inhibitor, we demonstrate that KRAS4B-RHOA interaction drives KARATE formation. In adipocytes, KARATE controls insulin-dependent translocation of the glucose transporter GLUT4 to the plasma membrane for glucose uptake. Thus, our work reveals a fundamental mechanism that activates mTORC2 toward AKT in insulin-regulated glucose homeostasis.
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Affiliation(s)
- Hiroshi Senoo
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Daisuke Murata
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - May Wai
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Kenta Arai
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Wakiko Iwata
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Hiromi Sesaki
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Miho Iijima
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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3
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Castel P, Dharmaiah S, Sale MJ, Messing S, Rizzuto G, Cuevas-Navarro A, Cheng A, Trnka MJ, Urisman A, Esposito D, Simanshu DK, McCormick F. RAS interaction with Sin1 is dispensable for mTORC2 assembly and activity. Proc Natl Acad Sci U S A 2021; 118:e2103261118. [PMID: 34380736 PMCID: PMC8379911 DOI: 10.1073/pnas.2103261118] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
RAS proteins are molecular switches that interact with effector proteins when bound to guanosine triphosphate, stimulating downstream signaling in response to multiple stimuli. Although several canonical downstream effectors have been extensively studied and tested as potential targets for RAS-driven cancers, many of these remain poorly characterized. In this study, we undertook a biochemical and structural approach to further study the role of Sin1 as a RAS effector. Sin1 interacted predominantly with KRAS isoform 4A in cells through an atypical RAS-binding domain that we have characterized by X-ray crystallography. Despite the essential role of Sin1 in the assembly and activity of mTORC2, we find that the interaction with RAS is not required for these functions. Cells and mice expressing a mutant of Sin1 that is unable to bind RAS are proficient for activation and assembly of mTORC2. Our results suggest that Sin1 is a bona fide RAS effector that regulates downstream signaling in an mTORC2-independent manner.
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Affiliation(s)
- Pau Castel
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94158
| | - Srisathiyanarayanan Dharmaiah
- National Cancer Institute (NCI) RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, MD 21702
| | - Matthew J Sale
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94158
| | - Simon Messing
- National Cancer Institute (NCI) RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, MD 21702
| | - Gabrielle Rizzuto
- Department of Anatomic Pathology, University of California, San Francisco, CA 94158
| | - Antonio Cuevas-Navarro
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94158
| | - Alice Cheng
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94158
| | - Michael J Trnka
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158
| | - Anatoly Urisman
- Department of Anatomic Pathology, University of California, San Francisco, CA 94158
| | - Dominic Esposito
- National Cancer Institute (NCI) RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, MD 21702
| | - Dhirendra K Simanshu
- National Cancer Institute (NCI) RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, MD 21702;
| | - Frank McCormick
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94158;
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4
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Senoo H, Wai M, Matsubayashi HT, Sesaki H, Iijima M. Hetero-oligomerization of Rho and Ras GTPases Connects GPCR Activation to mTORC2-AKT Signaling. Cell Rep 2020; 33:108427. [PMID: 33238110 DOI: 10.1016/j.celrep.2020.108427] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 09/14/2020] [Accepted: 11/02/2020] [Indexed: 12/19/2022] Open
Abstract
The activation of G-protein-coupled receptors (GPCRs) leads to the activation of mTORC2 in cell migration and metabolism. However, the mechanism that links GPCRs to mTORC2 remains unknown. Here, using Dictyostelium cells, we show that GPCR-mediated chemotactic stimulation induces hetero-oligomerization of phosphorylated GDP-bound Rho GTPase and GTP-bound Ras GTPase in directed cell migration. The Rho-Ras hetero-oligomers directly and specifically stimulate mTORC2 activity toward AKT in cells and after biochemical reconstitution using purified proteins in vitro. The Rho-Ras hetero-oligomers do not activate ERK/MAPK, another kinase that functions downstream of GPCRs and Ras. Human KRas4B functionally replace Dictyostelium Ras in mTORC2 activation. In contrast to GDP-Rho, GTP-Rho antagonizes mTORC2-AKT signaling by inhibiting the oligomerization of GDP-Rho with GTP-Ras. These data reveal that GPCR-stimulated hetero-oligomerization of Rho and Ras provides a critical regulatory step that controls mTORC2-AKT signaling.
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Affiliation(s)
- Hiroshi Senoo
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - May Wai
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Hideaki T Matsubayashi
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Hiromi Sesaki
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Miho Iijima
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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5
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Chadha R, Meador-Woodruff JH. Downregulated AKT-mTOR signaling pathway proteins in dorsolateral prefrontal cortex in Schizophrenia. Neuropsychopharmacology 2020; 45:1059-1067. [PMID: 31952070 PMCID: PMC7162985 DOI: 10.1038/s41386-020-0614-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 01/07/2020] [Accepted: 01/09/2020] [Indexed: 11/09/2022]
Abstract
Abnormal neurotransmission is central to schizophrenia (SZ). Alterations across multiple neurotransmitter systems in SZ suggest that this illness may be associated with dysregulation of core intracellular processes such as signaling pathways that underlie the regulation and integration of these systems. The AKT-mTOR signaling cascade has been implicated in SZ by gene association, postmortem brain and animal studies. AKT and mTOR are serine/threonine kinases which play important roles in cell growth, proliferation, survival, and differentiation. Both AKT and mTOR require phosphorylation at specific sites for their complete activation. mTOR forms two functionally distinct multiprotein complexes, mTOR Complex 1 (mTORC1) and Complex 2 (mTORC2). mTORC1 mediates ribosome biogenesis, protein translation, and autophagy, whereas mTORC2 contributes to actin dynamics. Altered protein synthesis and actin dynamics can lead to an abnormal neuronal morphology resulting in deficits in learning and memory. Currently, there is a lack of direct evidence to support the hypothesis of disrupted mTOR signaling in SZ, and we have addressed this by characterizing this signaling pathway in SZ brain. We found a reduction in AKT and mTOR protein expression and/or phosphorylation state in dorsolateral prefrontal cortex (DLPFC) from 22 pairs of SZ and matched comparison subjects. We also found reduced protein expression of GβL, a subunit protein common to both mTOR complexes. We further investigated mTOR complex-specific subunit composition and phosphorylation state, and found abnormal mTOR expression in both complexes in SZ DLPFC. These findings provide evidence that proteins associated with the AKT-mTOR signaling cascade are downregulated in SZ DLPFC.
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Affiliation(s)
- Radhika Chadha
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, 1719 6th Avenue South, Birmingham, AL, 35294-0021, USA.
| | - James H Meador-Woodruff
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, 1719 6th Avenue South, Birmingham, AL, 35294-0021, USA
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Senoo H, Kamimura Y, Kimura R, Nakajima A, Sawai S, Sesaki H, Iijima M. Phosphorylated Rho-GDP directly activates mTORC2 kinase towards AKT through dimerization with Ras-GTP to regulate cell migration. Nat Cell Biol 2019; 21:867-878. [PMID: 31263268 PMCID: PMC6650273 DOI: 10.1038/s41556-019-0348-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 05/29/2019] [Indexed: 11/19/2022]
Abstract
mTORC2 plays critical roles in metabolism, cell survival and actin cytoskeletal dynamics through the phosphorylation of AKT. Despite its importance to biology and medicine, it is unclear how mTORC2-mediated AKT phosphorylation is controlled. Here, we identify an unforeseen principle by which a GDP-bound form of the conserved small G protein Rho GTPase directly activates mTORC2 in AKT phosphorylation in social amoebae (Dictyostelium discoideum) cells. Using biochemical reconstitution with purified proteins, we demonstrate that Rho-GDP promotes AKT phosphorylation by assembling a supercomplex with Ras-GTP and mTORC2. This supercomplex formation is controlled by the chemoattractant-induced phosphorylation of Rho-GDP at S192 by GSK-3. Furthermore, Rho-GDP rescues defects in both mTORC2-mediated AKT phosphorylation and directed cell migration in Rho-null cells in a manner dependent on phosphorylation of S192. Thus, in contrast to the prevailing view that the GDP-bound forms of G proteins are inactive, our study reveals that mTORC2-AKT signalling is activated by Rho-GDP.
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Affiliation(s)
- Hiroshi Senoo
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Yoichiro Kamimura
- Laboratory for Cell Signaling Dynamics, Quantitative Biology Center, RIKEN, Suita, Japan
| | - Reona Kimura
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Akihiko Nakajima
- Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan
| | - Satoshi Sawai
- Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan
| | - Hiromi Sesaki
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Miho Iijima
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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7
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Caldana C, Martins MCM, Mubeen U, Urrea-Castellanos R. The magic 'hammer' of TOR: the multiple faces of a single pathway in the metabolic regulation of plant growth and development. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:2217-2225. [PMID: 30722050 DOI: 10.1093/jxb/ery459] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 12/11/2018] [Indexed: 06/09/2023]
Abstract
The target of rapamycin (TOR) pathway has emerged as a central hub synchronizing plant growth according to the nutrient/energy status and environmental inputs. Molecular mechanisms through which TOR promotes plant growth involve the positive regulation of transcription of cell proliferation-associated genes, mRNA translation initiation and ribosome biogenesis, to cite a few examples. Phytohormones, light, sugars, and sulfur have been found to broadly regulate TOR activity. TOR operates as a metabolic homeostat to fine-tune anabolic processes and efficiently enable plant growth under different circumstances. However, little is known about the multiple effectors that act up- and downstream of TOR. Here, we mainly discuss recent findings related to the TOR pathway in the context of plant metabolism and highlight areas of interest that need to be addressed to keep unravelling the intricate networks governing the regulation of TOR and its function in controlling biosynthetic growth.
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Affiliation(s)
- Camila Caldana
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg, Potsdam-Golm, Germany
| | | | - Umarah Mubeen
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg, Potsdam-Golm, Germany
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8
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Nacarelli T, Azar A, Sell C. Mitochondrial stress induces cellular senescence in an mTORC1-dependent manner. Free Radic Biol Med 2016; 95:133-54. [PMID: 27016071 DOI: 10.1016/j.freeradbiomed.2016.03.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 03/07/2016] [Accepted: 03/12/2016] [Indexed: 11/25/2022]
Abstract
Although mitochondrial stress is a key determinant of cellular homeostasis, the intracellular mechanisms by which this stress is communicated to the nucleus and its impact on cell fate decisions are not well defined. In this study, we report that activation of mTORC1 signaling triggered by mitochondrial-generated reactive oxygen species (ROS) results in activation of the senescence program. We show that exposure of human fibroblasts to nucleoside analogs commonly used in antiretroviral therapies, and known to induce mitochondrial dysfunction, increases mitochondrial ROS and leads to a rise in intracellular ROS concomitant with activation of mTORC1. In this setting, it appears that mTORC1 activates senescence through HDM2 phosphorylation, facilitating a p53-mediated response. Inhibition of mTORC1 by rapamycin decreases HDM2 phosphorylation and blocks activation of the senescence program in human cells. In addition, decreasing mitochondrial ROS directly blocks mTORC1 signaling and prevents the onset of senescence. Consistent with these results, both total and mitochondrial-specific ROS increased in cells undergoing replicative senescence along with ribosomal p70 phosphorylation. The results reveal a novel link between mitochondrial dysfunction, mTORC1 signaling, and the senescence program.
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Affiliation(s)
- Timothy Nacarelli
- Drexel University College of Medicine, 245 N 15th Street, Philadelphia, PA 19102, United States
| | - Ashley Azar
- Drexel University College of Medicine, 245 N 15th Street, Philadelphia, PA 19102, United States
| | - Christian Sell
- Drexel University College of Medicine, 245 N 15th Street, Philadelphia, PA 19102, United States.
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9
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Chen CH, Kiyan V, Zhylkibayev AA, Kazyken D, Bulgakova O, Page KE, Bersimbaev RI, Spooner E, Sarbassov DD. Autoregulation of the mechanistic target of rapamycin (mTOR) complex 2 integrity is controlled by an ATP-dependent mechanism. J Biol Chem 2013; 288:27019-27030. [PMID: 23928304 DOI: 10.1074/jbc.m113.498055] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nutrients are essential for living organisms because they fuel biological processes in cells. Cells monitor nutrient abundance and coordinate a ratio of anabolic and catabolic reactions. Mechanistic target of rapamycin (mTOR) signaling is the essential nutrient-sensing pathway that controls anabolic processes in cells. The central component of this pathway is mTOR, a highly conserved and essential protein kinase that exists in two distinct functional complexes. The nutrient-sensitive mTOR complex 1 (mTORC1) controls cell growth and cell size by phosphorylation of the regulators of protein synthesis S6K1 and 4EBP1, whereas its second complex, mTORC2, regulates cell proliferation by functioning as the regulatory kinase of Akt and other members of the AGC kinase family. The regulation of mTORC2 remains poorly characterized. Our study shows that the cellular ATP balance controls a basal kinase activity of mTORC2 that maintains the integrity of mTORC2 and phosphorylation of Akt on the turn motif Thr-450 site. We found that mTOR stabilizes SIN1 by phosphorylation of its hydrophobic and conserved Ser-260 site to maintain the integrity of mTORC2. The optimal kinase activity of mTORC2 requires a concentration of ATP above 1.2 mM and makes this kinase complex highly sensitive to ATP depletion. We found that not amino acid but glucose deprivation of cells or acute ATP depletion prevented the mTOR-dependent phosphorylation of SIN1 on Ser-260 and Akt on Thr-450. In a low glucose medium, the cells carrying a substitution of SIN1 with its phosphomimetic mutant show an increased rate of cell proliferation related to a higher abundance of mTORC2 and phosphorylation of Akt. Thus, the homeostatic ATP sensor mTOR controls the integrity of mTORC2 and phosphorylation of Akt on the turn motif site.
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Affiliation(s)
- Chien-Hung Chen
- Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77030
| | - Vladimir Kiyan
- Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan
| | - Assylbek A Zhylkibayev
- Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan
| | - Dubek Kazyken
- Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan
| | - Olga Bulgakova
- Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan
| | - Kent E Page
- Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Biomedical Engineering, University of Houston, Houston, Texas 77004
| | - Rakhmet I Bersimbaev
- Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan
| | - Eric Spooner
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142
| | - Dos D Sarbassov
- Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77030.
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