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Domma AJ, Henderson LA, Goodrum FD, Moorman NJ, Kamil JP. Human cytomegalovirus attenuates AKT activity by destabilizing insulin receptor substrate proteins. J Virol 2023; 97:e0056323. [PMID: 37754763 PMCID: PMC10617551 DOI: 10.1128/jvi.00563-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Accepted: 08/09/2023] [Indexed: 09/28/2023] Open
Abstract
IMPORTANCE Human cytomegalovirus (HCMV) requires inactivation of AKT to efficiently replicate, yet how AKT is shut off during HCMV infection has remained unclear. We show that UL38, an HCMV protein that activates mTORC1, is necessary and sufficient to destabilize insulin receptor substrate 1 (IRS1), a model insulin receptor substrate (IRS) protein. Degradation of IRS proteins in settings of excessive mTORC1 activity is an important mechanism for insulin resistance. When IRS proteins are destabilized, PI3K cannot be recruited to growth factor receptor complexes, and hence, AKT membrane recruitment, a rate limiting step in its activation, fails to occur. Despite its penchant for remodeling host cell signaling pathways, our results reveal that HCMV relies upon a cell-intrinsic negative regulatory feedback loop to inactivate AKT. Given that pharmacological inhibition of PI3K/AKT potently induces HCMV reactivation from latency, our findings also imply that the expression of UL38 activity must be tightly regulated within latently infected cells to avoid spontaneous reactivation.
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Affiliation(s)
- Anthony J. Domma
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center Shreveport, Shreveport, Louisiana, USA
| | - Lauren A. Henderson
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center Shreveport, Shreveport, Louisiana, USA
| | - Felicia D. Goodrum
- Department of Immunobiology, University of Arizona, Tucson, Arizona, USA
- Bio5 Institute, University of Arizona, Tucson, Arizona, USA
| | - Nathaniel J. Moorman
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Jeremy P. Kamil
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center Shreveport, Shreveport, Louisiana, USA
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Blandino-Rosano M, Louzada RA, Werneck-De-Castro JP, Lubaczeuski C, Almaça J, Rüegg MA, Hall MN, Leibowitz G, Bernal-Mizrachi E. Raptor levels are critical for β-cell adaptation to a high-fat diet in male mice. Mol Metab 2023; 75:101769. [PMID: 37423392 PMCID: PMC10391668 DOI: 10.1016/j.molmet.2023.101769] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 06/19/2023] [Accepted: 06/29/2023] [Indexed: 07/11/2023] Open
Abstract
OBJECTIVE The essential role of raptor/mTORC1 signaling in β-cell survival and insulin processing has been recently demonstrated using raptor knock-out models. Our aim was to evaluate the role of mTORC1 function in adaptation of β-cells to insulin resistant state. METHOD Here, we use mice with heterozygous deletion of raptor in β-cells (βraHet) to assess whether reduced mTORC1 function is critical for β-cell function in normal conditions or during β-cell adaptation to high-fat diet (HFD). RESULTS Deletion of a raptor allele in β-cells showed no differences at the metabolic level, islets morphology, or β-cell function in mice fed regular chow. Surprisingly, deletion of only one allele of raptor increases apoptosis without altering proliferation rate and is sufficient to impair insulin secretion when fed a HFD. This is accompanied by reduced levels of critical β-cell genes like Ins1, MafA, Ucn3, Glut2, Glp1r, and specially PDX1 suggesting an improper β-cell adaptation to HFD. CONCLUSION This study identifies that raptor levels play a key role in maintaining PDX1 levels and β-cell function during the adaptation of β-cell to HFD. Finally, we identified that Raptor levels regulate PDX1 levels and β-cell function during β-cell adaptation to HFD by reduction of the mTORC1-mediated negative feedback and activation of the AKT/FOXA2/PDX1 axis. We suggest that Raptor levels are critical to maintaining PDX1 levels and β-cell function in conditions of insulin resistance in male mice.
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Affiliation(s)
- Manuel Blandino-Rosano
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA; Miami VA Health Care System, Miami, FL, USA.
| | - Ruy Andrade Louzada
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Joao Pedro Werneck-De-Castro
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA; Miami VA Health Care System, Miami, FL, USA
| | - Camila Lubaczeuski
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Joana Almaça
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Markus A Rüegg
- Biozentrum, University of Basel, CH-4056, Basel, Switzerland
| | - Michael N Hall
- Biozentrum, University of Basel, CH-4056, Basel, Switzerland
| | - Gil Leibowitz
- Diabetes Unit and Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Ernesto Bernal-Mizrachi
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA; Miami VA Health Care System, Miami, FL, USA.
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Shin S, Han MJ, Jedrychowski MP, Zhang Z, Shokat KM, Plas DR, Dephoure N, Yoon SO. mTOR inhibition reprograms cellular proteostasis by regulating eIF3D-mediated selective mRNA translation and promotes cell phenotype switching. Cell Rep 2023; 42:112868. [PMID: 37494188 PMCID: PMC10528759 DOI: 10.1016/j.celrep.2023.112868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 05/31/2023] [Accepted: 07/11/2023] [Indexed: 07/28/2023] Open
Abstract
Cells maintain and dynamically change their proteomes according to the environment and their needs. Mechanistic target of rapamycin (mTOR) is a key regulator of proteostasis, homeostasis of the proteome. Thus, dysregulation of mTOR leads to changes in proteostasis and the consequent progression of diseases, including cancer. Based on the physiological and clinical importance of mTOR signaling, we investigated mTOR feedback signaling, proteostasis, and cell fate. Here, we reveal that mTOR targeting inhibits eIF4E-mediated cap-dependent translation, but feedback signaling activates a translation initiation factor, eukaryotic translation initiation factor 3D (eIF3D), to sustain alternative non-canonical translation mechanisms. Importantly, eIF3D-mediated protein synthesis enables cell phenotype switching from proliferative to more migratory. eIF3D cooperates with mRNA-binding proteins such as heterogeneous nuclear ribonucleoprotein F (hnRNPF), heterogeneous nuclear ribonucleoprotein K (hnRNPK), and Sjogren syndrome antigen B (SSB) to support selective mRNA translation following mTOR inhibition, which upregulates and activates proteins involved in insulin receptor (INSR)/insulin-like growth factor 1 receptor (IGF1R)/insulin receptor substrate (IRS) and interleukin 6 signal transducer (IL-6ST)/Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling. Our study highlights the mechanisms by which cells establish the dynamic change of proteostasis and the resulting phenotype switch.
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Affiliation(s)
- Sejeong Shin
- Department of Physiology and Biophysics, University of Illinois College of Medicine at Chicago, Chicago, IL 60612, USA
| | - Min-Joon Han
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | | | - Ziyang Zhang
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA
| | - Kevan M Shokat
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA
| | - David R Plas
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
| | - Noah Dephoure
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10021, USA
| | - Sang-Oh Yoon
- Department of Physiology and Biophysics, University of Illinois College of Medicine at Chicago, Chicago, IL 60612, USA.
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Domma AJ, Goodrum FD, Moorman NJ, Kamil JP. Human cytomegalovirus attenuates AKT activity by destabilizing insulin receptor substrate proteins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.17.537203. [PMID: 37131605 PMCID: PMC10153195 DOI: 10.1101/2023.04.17.537203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The phosphoinositide 3-kinase (PI3K)/AKT pathway plays crucial roles in cell viability and protein synthesis and is frequently co-opted by viruses to support their replication. Although many viruses maintain high levels of AKT activity during infection, other viruses, such as vesicular stomatitis virus and human cytomegalovirus (HCMV), cause AKT to accumulate in an inactive state. To efficiently replicate, HCMV requires FoxO transcription factors to localize to the infected cell nucleus (Zhang et. al. mBio 2022), a process directly antagonized by AKT. Therefore, we sought to investigate how HCMV inactivates AKT to achieve this. Subcellular fractionation and live cell imaging studies indicated that AKT failed to recruit to membranes upon serum-stimulation of infected cells. However, UV-inactivated virions were unable to render AKT non-responsive to serum, indicating a requirement for de novo viral gene expression. Interestingly, we were able to identify that UL38 (pUL38), a viral activator of mTORC1, is required to diminish AKT responsiveness to serum. mTORC1 contributes to insulin resistance by causing proteasomal degradation of insulin receptor substrate (IRS) proteins, such as IRS1, which are necessary for the recruitment of PI3K to growth factor receptors. In cells infected with a recombinant HCMV disrupted for UL38 , AKT responsiveness to serum is retained and IRS1 is not degraded. Furthermore, ectopic expression of UL38 in uninfected cells induces IRS1 degradation, inactivating AKT. These effects of UL38 were reversed by the mTORC1 inhibitor, rapamycin. Collectively, our results demonstrate that HCMV relies upon a cell-intrinsic negative feedback loop to render AKT inactive during productive infection.
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Affiliation(s)
- Anthony J. Domma
- Department of Microbiology and Immunology, LSU Health Sciences Center Shreveport, Shreveport Louisiana, USA
| | - Felicia D. Goodrum
- Department of Immunobiology, University of Arizona, Tucson, AZ, USA
- Bio5 Institute, University of Arizona, Tucson, AZ, USA
| | - Nathaniel J. Moorman
- Department of Microbiology and Immunology, UNC Chapel Hill, Chapel Hill, NC, USA
| | - Jeremy P. Kamil
- Department of Microbiology and Immunology, LSU Health Sciences Center Shreveport, Shreveport Louisiana, USA
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5
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Biomedical importance of the ubiquitin-proteasome system in diabetes and metabolic transdifferentiation of pancreatic duct epithelial cells into β-cells. Gene 2023; 858:147191. [PMID: 36632913 DOI: 10.1016/j.gene.2023.147191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 01/05/2023] [Accepted: 01/06/2023] [Indexed: 01/09/2023]
Abstract
The ubiquitin-proteasome system (UPS) is a major pathway for cellular protein degradation. The molecular function of the UPS is the removal of damaged proteins, and this function is applied in many biological processes, including inflammation, proliferation, and apoptosis. Accumulating evidence also suggests that the UPS also has a key role in pancreatic β-cell transdifferentiation in diabetes and can be targeted for treatment of diabetic diseases. In this review, we summarized the mechanistic roles of the UPS in the biochemical activities of pancreatic β-cells, including the role of the UPS in insulin synthesis and secretion, as well as β-cell degradation. Also, we discuss how the UPS mediates the transdifferentiation of pancreatic duct epithelial cells into β-cells as the experimental basis for the development of new strategies for the treatment of diabetes in regenerative medicine.
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A mixed blessing for liver transplantation patients - Rapamycin. Hepatobiliary Pancreat Dis Int 2023; 22:14-21. [PMID: 36328894 DOI: 10.1016/j.hbpd.2022.10.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 10/14/2022] [Indexed: 11/04/2022]
Abstract
BACKGROUND Liver transplantation (LT) is an effective treatment option for end-stage liver disease. Mammalian target of rapamycin (mTOR) inhibitors, such as rapamycin, are widely used post LT. DATA SOURCES In this review, we focused on the anti-cancer activities and metabolic side effects of rapamycin after LT. The literature available on PubMed for the period of January 1999-September 2022 was reviewed. The key words were rapamycin, sirolimus, liver transplantation, hepatocellular carcinoma, diabetes, and lipid metabolism disorder. RESULTS Rapamycin has shown excellent effects and is safer than other immunosuppressive regimens. It has exhibited excellent anti-cancer activity and has the potential in preventing hepatocellular carcinoma (HCC) recurrence post LT. Rapamycin is closely related to two long-term complications after LT, diabetes and lipid metabolism disorders. CONCLUSIONS Rapamycin prevents HCC recurrence post LT in some patients, but it also induces metabolic disorders. Reasonable use of rapamycin benefits the liver recipients.
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Sanz‐Castillo B, Hurtado B, Vara‐Ciruelos D, El Bakkali A, Hermida D, Salvador‐Barbero B, Martínez‐Alonso D, González‐Martínez J, Santiveri C, Campos‐Olivas R, Ximénez‐Embún P, Muñoz J, Álvarez‐Fernández M, Malumbres M. The MASTL/PP2A cell cycle kinase-phosphatase module restrains PI3K-Akt activity in an mTORC1-dependent manner. EMBO J 2023; 42:e110833. [PMID: 36354735 PMCID: PMC9841333 DOI: 10.15252/embj.2022110833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 10/24/2022] [Accepted: 10/24/2022] [Indexed: 11/11/2022] Open
Abstract
The AKT-mTOR pathway is a central regulator of cell growth and metabolism. Upon sustained mTOR activity, AKT activity is attenuated by a feedback loop that restrains upstream signaling. However, how cells control the signals that limit AKT activity is not fully understood. Here, we show that MASTL/Greatwall, a cell cycle kinase that supports mitosis by phosphorylating the PP2A/B55 inhibitors ENSA/ARPP19, inhibits PI3K-AKT activity by sustaining mTORC1- and S6K1-dependent phosphorylation of IRS1 and GRB10. Genetic depletion of MASTL results in an inefficient feedback loop and AKT hyperactivity. These defects are rescued by the expression of phosphomimetic ENSA/ARPP19 or inhibition of PP2A/B55 phosphatases. MASTL is directly phosphorylated by mTORC1, thereby limiting the PP2A/B55-dependent dephosphorylation of IRS1 and GRB10 downstream of mTORC1. Downregulation of MASTL results in increased glucose uptake in vitro and increased glucose tolerance in adult mice, suggesting the relevance of the MASTL-PP2A/B55 kinase-phosphatase module in controlling AKT and maintaining metabolic homeostasis.
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Affiliation(s)
- Belén Sanz‐Castillo
- Cell Division and Cancer GroupSpanish National Cancer Research Centre (CNIO)MadridSpain
| | - Begoña Hurtado
- Cell Division and Cancer GroupSpanish National Cancer Research Centre (CNIO)MadridSpain
| | - Diana Vara‐Ciruelos
- Cell Division and Cancer GroupSpanish National Cancer Research Centre (CNIO)MadridSpain
| | - Aicha El Bakkali
- Cell Division and Cancer GroupSpanish National Cancer Research Centre (CNIO)MadridSpain
| | - Dario Hermida
- Cell Division and Cancer GroupSpanish National Cancer Research Centre (CNIO)MadridSpain
| | | | - Diego Martínez‐Alonso
- Cell Division and Cancer GroupSpanish National Cancer Research Centre (CNIO)MadridSpain
| | | | - Clara Santiveri
- Spectroscopy and Nuclear Magnetic Resonance UnitSpanish National Cancer Research Centre (CNIO)MadridSpain
| | - Ramón Campos‐Olivas
- Spectroscopy and Nuclear Magnetic Resonance UnitSpanish National Cancer Research Centre (CNIO)MadridSpain
| | | | - Javier Muñoz
- Proteomics UnitSpanish National Cancer Research Centre (CNIO)MadridSpain
| | - Mónica Álvarez‐Fernández
- Cell Division and Cancer GroupSpanish National Cancer Research Centre (CNIO)MadridSpain
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA)Instituto Universitario de Oncología del Principado de Asturias (IUOPA)OviedoSpain
| | - Marcos Malumbres
- Cell Division and Cancer GroupSpanish National Cancer Research Centre (CNIO)MadridSpain
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Scalia P, Williams SJ, Fujita-Yamaguchi Y, Giordano A. Cell cycle control by the insulin-like growth factor signal: at the crossroad between cell growth and mitotic regulation. Cell Cycle 2023; 22:1-37. [PMID: 36005738 PMCID: PMC9769454 DOI: 10.1080/15384101.2022.2108117] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
In proliferating cells and tissues a number of checkpoints (G1/S and G2/M) preceding cell division (M-phase) require the signal provided by growth factors present in serum. IGFs (I and II) have been demonstrated to constitute key intrinsic components of the peptidic active fraction of mammalian serum. In vivo genetic ablation studies have shown that the cellular signal triggered by the IGFs through their cellular receptors represents a non-replaceable requirement for cell growth and cell cycle progression. Retroactive and current evaluation of published literature sheds light on the intracellular circuitry activated by these factors providing us with a better picture of the pleiotropic mechanistic actions by which IGFs regulate both cell size and mitogenesis under developmental growth as well as in malignant proliferation. The present work aims to summarize the cumulative knowledge learned from the IGF ligands/receptors and their intracellular signaling transducers towards control of cell size and cell-cycle with particular focus to their actionable circuits in human cancer. Furthermore, we bring novel perspectives on key functional discriminants of the IGF growth-mitogenic pathway allowing re-evaluation on some of its signal components based upon established evidences.
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Affiliation(s)
- Pierluigi Scalia
- ISOPROG-Somatolink EPFP Research Network, Philadelphia, PA, USA, Caltanissetta, Italy,CST, Biology, Sbarro Institute for Cancer Research and Molecular Medicine, Temple University, Philadelphia, PA, United states,CONTACT Pierluigi Scalia ISOPROG-Somatolink EPFP Research Network, Philadelphia, PA9102, USA
| | - Stephen J Williams
- ISOPROG-Somatolink EPFP Research Network, Philadelphia, PA, USA, Caltanissetta, Italy,CST, Biology, Sbarro Institute for Cancer Research and Molecular Medicine, Temple University, Philadelphia, PA, United states
| | - Yoko Fujita-Yamaguchi
- Arthur Riggs Diabetes & Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, CA, USA
| | - Antonio Giordano
- ISOPROG-Somatolink EPFP Research Network, Philadelphia, PA, USA, Caltanissetta, Italy,School of Medical Biotechnology, University of Siena, Italy
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Chen T, Dalton G, Oh SH, Maeso-Diaz R, Du K, Meyers RA, Guy C, Abdelmalek MF, Henao R, Guarnieri P, Pullen SS, Gregory S, Locker J, Brown JM, Diehl AM. Hepatocyte Smoothened Activity Controls Susceptibility to Insulin Resistance and Nonalcoholic Fatty Liver Disease. Cell Mol Gastroenterol Hepatol 2022; 15:949-970. [PMID: 36535507 PMCID: PMC9957752 DOI: 10.1016/j.jcmgh.2022.12.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 12/09/2022] [Accepted: 12/09/2022] [Indexed: 01/07/2023]
Abstract
BACKGROUND & AIMS Nonalcoholic steatohepatitis (NASH), a leading cause of cirrhosis, strongly associates with the metabolic syndrome, an insulin-resistant proinflammatory state that disrupts energy balance and promotes progressive liver degeneration. We aimed to define the role of Smoothened (Smo), an obligatory component of the Hedgehog signaling pathway, in controlling hepatocyte metabolic homeostasis and, thereby, susceptibility to NASH. METHODS We conditionally deleted Smo in hepatocytes of healthy chow-fed mice and performed metabolic phenotyping, coupled with single-cell RNA sequencing (RNA-seq), to characterize the role of hepatocyte Smo in regulating basal hepatic and systemic metabolic homeostasis. Liver RNA-seq datasets from 2 large human cohorts were also analyzed to define the relationship between Smo and NASH susceptibility in people. RESULTS Hepatocyte Smo deletion inhibited the Hedgehog pathway and promoted fatty liver, hyperinsulinemia, and insulin resistance. We identified a plausible mechanism whereby inactivation of Smo stimulated the mTORC1-SREBP1c signaling axis, which promoted lipogenesis while inhibiting the hepatic insulin cascade. Transcriptomics of bulk and single Smo-deficient hepatocytes supported suppression of insulin signaling and also revealed molecular abnormalities associated with oxidative stress and mitochondrial dysfunction. Analysis of human bulk RNA-seq data revealed that Smo expression was (1) highest in healthy livers, (2) lower in livers with NASH than in those with simple steatosis, (3) negatively correlated with markers of insulin resistance and liver injury, and (4) declined progressively as fibrosis severity worsened. CONCLUSIONS The Hedgehog pathway controls insulin sensitivity and energy homeostasis in adult livers. Loss of hepatocyte Hedgehog activity induces hepatic and systemic metabolic stress and enhances susceptibility to NASH by promoting hepatic lipoxicity and insulin resistance.
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Affiliation(s)
- Tianyi Chen
- Department of Medicine, Duke University, Durham, North Carolina
| | - George Dalton
- Department of Medicine, Duke University, Durham, North Carolina
| | - Seh-Hoon Oh
- Department of Medicine, Duke University, Durham, North Carolina
| | | | - Kuo Du
- Department of Medicine, Duke University, Durham, North Carolina
| | - Rachel A Meyers
- Department of Medicine, Duke University, Durham, North Carolina
| | - Cynthia Guy
- Department of Medicine, Duke University, Durham, North Carolina
| | | | - Ricardo Henao
- Department of Medicine, Duke University, Durham, North Carolina
| | - Paolo Guarnieri
- Boehringer Ingelheim Pharmaceuticals Inc, Ridgefield, Connecticut
| | - Steven S Pullen
- Boehringer Ingelheim Pharmaceuticals Inc, Ridgefield, Connecticut
| | - Simon Gregory
- Department of Medicine, Duke University, Durham, North Carolina
| | - Joseph Locker
- Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - J Mark Brown
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio
| | - Anna Mae Diehl
- Department of Medicine, Duke University, Durham, North Carolina.
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Ciminera AK, Shuck SC, Termini J. Elevated glucose increases genomic instability by inhibiting nucleotide excision repair. Life Sci Alliance 2021; 4:4/10/e202101159. [PMID: 34426491 PMCID: PMC8385305 DOI: 10.26508/lsa.202101159] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 08/09/2021] [Accepted: 08/10/2021] [Indexed: 12/23/2022] Open
Abstract
Exposure to chronic, elevated glucose inhibits nucleotide excision repair, which leads to accumulation of DNA glycation adducts, increased DNA strand breaks, and activation of the DNA damage response. We investigated potential mechanisms by which elevated glucose may promote genomic instability. Gene expression studies, protein measurements, mass spectroscopic analyses, and functional assays revealed that elevated glucose inhibited the nucleotide excision repair (NER) pathway, promoted DNA strand breaks, and increased levels of the DNA glycation adduct N2-(1-carboxyethyl)-2ʹ-deoxyguanosine (CEdG). Glycation stress in NER-competent cells yielded single-strand breaks accompanied by ATR activation, γH2AX induction, and enhanced non-homologous end-joining and homology-directed repair. In NER-deficient cells, glycation stress activated ATM/ATR/H2AX, consistent with double-strand break formation. Elevated glucose inhibited DNA repair by attenuating hypoxia-inducible factor-1α–mediated transcription of NER genes via enhanced 2-ketoglutarate–dependent prolyl hydroxylase (PHD) activity. PHD inhibition enhanced transcription of NER genes and facilitated CEdG repair. These results are consistent with a role for hyperglycemia in promoting genomic instability as a potential mechanism for increasing cancer risk in metabolic disease. Because of the pleiotropic functions of many NER genes beyond DNA repair, these results may have broader implications for cellular pathophysiology.
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Affiliation(s)
- Alexandra K Ciminera
- Department of Molecular Medicine, Beckman Research Institute at City of Hope, Duarte, CA, USA.,Irell and Manella Graduate School of Biomedical Sciences, City of Hope, Duarte, CA, USA
| | - Sarah C Shuck
- Department of Molecular Medicine, Beckman Research Institute at City of Hope, Duarte, CA, USA
| | - John Termini
- Department of Molecular Medicine, Beckman Research Institute at City of Hope, Duarte, CA, USA
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Stanciu GD, Rusu RN, Bild V, Filipiuc LE, Tamba BI, Ababei DC. Systemic Actions of SGLT2 Inhibition on Chronic mTOR Activation as a Shared Pathogenic Mechanism between Alzheimer's Disease and Diabetes. Biomedicines 2021; 9:biomedicines9050576. [PMID: 34069618 PMCID: PMC8160780 DOI: 10.3390/biomedicines9050576] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 05/15/2021] [Accepted: 05/17/2021] [Indexed: 02/07/2023] Open
Abstract
Alzheimer's disease (AD) affects tens of millions of people worldwide. Despite the advances in understanding the disease, there is an increased urgency for pharmacological approaches able of impacting its onset and progression. With a multifactorial nature, high incidence and prevalence in later years of life, there is growing evidence highlighting a relationship between metabolic dysfunction related to diabetes and subject's susceptibility to develop AD. The link seems so solid that sometimes AD and type 3 diabetes are used interchangeably. A candidate for a shared pathogenic mechanism linking these conditions is chronically-activated mechanistic target of rapamycin (mTOR). Chronic activation of unrestrained mTOR could be responsible for sustaining metabolic dysfunction that causes the breakdown of the blood-brain barrier, tau hyperphosphorylation and senile plaques formation in AD. It has been suggested that inhibition of sodium glucose cotransporter 2 (SGLT2) mediated by constant glucose loss, may restore mTOR cycle via nutrient-driven, preventing or even decreasing the AD progression. Currently, there is an unmet need for further research insight into molecular mechanisms that drive the onset and AD advancement as well as an increase in efforts to expand the testing of potential therapeutic strategies aimed to counteract disease progression in order to structure effective therapies.
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Affiliation(s)
- Gabriela Dumitrita Stanciu
- Center for Advanced Research and Development in Experimental Medicine (CEMEX), Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (G.D.S.); (V.B.); (L.E.F.)
| | - Razvan Nicolae Rusu
- Pharmacodynamics and Clinical Pharmacy Department, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (R.N.R.); (D.C.A.)
| | - Veronica Bild
- Center for Advanced Research and Development in Experimental Medicine (CEMEX), Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (G.D.S.); (V.B.); (L.E.F.)
- Pharmacodynamics and Clinical Pharmacy Department, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (R.N.R.); (D.C.A.)
| | - Leontina Elena Filipiuc
- Center for Advanced Research and Development in Experimental Medicine (CEMEX), Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (G.D.S.); (V.B.); (L.E.F.)
- Department of Pharmacology, Clinical Pharmacology and Algesiology, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania
| | - Bogdan-Ionel Tamba
- Center for Advanced Research and Development in Experimental Medicine (CEMEX), Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (G.D.S.); (V.B.); (L.E.F.)
- Department of Pharmacology, Clinical Pharmacology and Algesiology, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania
- Correspondence:
| | - Daniela Carmen Ababei
- Pharmacodynamics and Clinical Pharmacy Department, Grigore T. Popa University of Medicine and Pharmacy, 16 Universitatii Street, 700115 Iasi, Romania; (R.N.R.); (D.C.A.)
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12
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Jara MA, Werneck-De-Castro JP, Lubaczeuski C, Johnson JD, Bernal-Mizrachi E. Pancreatic and duodenal homeobox-1 (PDX1) contributes to β-cell mass expansion and proliferation induced by Akt/PKB pathway. Islets 2020; 12:32-40. [PMID: 32876522 PMCID: PMC7527019 DOI: 10.1080/19382014.2020.1762471] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Maintenance of pancreatic β-cell mass and function is fundamental to glucose homeostasis and to prevent diabetes. The PI3 K-Akt-mTORC1 pathway is critical for β-cells mass and function, while PDX1 has been implicated in β-cell development, maturation, and function. Here we tested whether Akt signaling requires PDX1 expression to regulate β-cell mass, proliferation, and glucose homeostasis. In order to address that, we crossed a mouse model overexpressing constitutively active Akt mutant in β-cells (β-caAkt) with mice lacking one allele of PDX1gene (β-caAkt/pdx1+/-). While the β-caAkt mice exhibit higher plasma insulin levels, greater β-cell mass and improved glucose tolerance compared to control mice, the β-caAkt/pdx1+/- mice are hyperglycemic and intolerant to glucose. The changes in glucose homeostasis in β-caAkt/pdx1+/- were associated with a 60% reduction in β-cell mass compared to β-caAkt mice. The impaired β-cell mass in the β-caAkt/pdx1+/- mice can be explained by a lesser β-cell proliferation measured by the number of Ki67 positive β-cells. We did not observe any differences in apoptosis between β-caAkt/pdx1+/- and β-caAkt mice. In conclusion, PDX1 contributes to β-cell mass expansion and glucose metabolism induced by activation of Akt signaling.
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Affiliation(s)
- Mark Anthony Jara
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Joao Pedro Werneck-De-Castro
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
- Miami VA Health Care System, Miami, FL, USA
| | - Camila Lubaczeuski
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - James D. Johnson
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada
| | - Ernesto Bernal-Mizrachi
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
- Miami VA Health Care System, Miami, FL, USA
- CONTACT Ernesto Bernal-Mizrachi Department Of Internal Medicine, Division Of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine, Miami, FL33136, USA
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13
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Paczkowska-Abdulsalam M, Niemira M, Bielska A, Szałkowska A, Raczkowska BA, Junttila S, Gyenesei A, Adamska-Patruno E, Maliszewska K, Citko A, Szczerbiński Ł, Krętowski A. Evaluation of Transcriptomic Regulations behind Metabolic Syndrome in Obese and Lean Subjects. Int J Mol Sci 2020; 21:ijms21041455. [PMID: 32093387 PMCID: PMC7073064 DOI: 10.3390/ijms21041455] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 02/17/2020] [Accepted: 02/19/2020] [Indexed: 01/03/2023] Open
Abstract
Multiple mechanisms have been suggested to confer to the pathophysiology of metabolic syndrome (MetS), however despite great interest from the scientific community, the exact contribution of each of MetS risk factors still remains unclear. The present study aimed to investigate molecular signatures in peripheral blood of individuals affected by MetS and different degrees of obesity. Metabolic health of 1204 individuals from 1000PLUS cohort was assessed, and 32 subjects were recruited to four study groups: MetS lean, MetS obese, “healthy obese”, and healthy lean. Whole-blood transcriptome next generation sequencing with functional data analysis were carried out. MetS obese and MetS lean study participants showed the upregulation of genes involved in inflammation and coagulation processes: granulocyte adhesion and diapedesis (p < 0.0001, p = 0.0063), prothrombin activation pathway (p = 0.0032, p = 0.0091), coagulation system (p = 0.0010, p = 0.0155). The results for “healthy obese” indicate enrichment in molecules associated with protein synthesis (p < 0.0001), mitochondrial dysfunction (p < 0.0001), and oxidative phosphorylation (p < 0.0001). Our results suggest that MetS is related to the state of inflammation and vascular system changes independent of excess body weight. Furthermore, “healthy obese”, despite not fulfilling the criteria for MetS diagnosis, seems to display an intermediate state with a lower degree of metabolic abnormalities, before they proceed to a full blown MetS.
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Affiliation(s)
- Magdalena Paczkowska-Abdulsalam
- Clinical Research Centre, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
- Correspondence: ; Tel.: +48-85-831-81-59
| | - Magdalena Niemira
- Clinical Research Centre, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
| | - Agnieszka Bielska
- Clinical Research Centre, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
| | - Anna Szałkowska
- Clinical Research Centre, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
| | - Beata Anna Raczkowska
- Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
| | - Sini Junttila
- Vienna Biocenter Core Facilities, Dr.-Bohr-Gasse 3, 1030 Vienna, Austria
| | - Attila Gyenesei
- Vienna Biocenter Core Facilities, Dr.-Bohr-Gasse 3, 1030 Vienna, Austria
| | - Edyta Adamska-Patruno
- Clinical Research Centre, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
| | - Katarzyna Maliszewska
- Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
| | - Anna Citko
- Clinical Research Centre, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
| | - Łukasz Szczerbiński
- Clinical Research Centre, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
| | - Adam Krętowski
- Clinical Research Centre, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
- Department of Endocrinology, Diabetology and Internal Medicine, Medical University of Białystok, M. Skłodowskiej-Curie 24A, 15-276 Białystok, Poland
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14
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Lu M, Ma L, Shan P, Liu A, Yu X, Jiang W, Wang X, Zhao X, Ye X, Wang T. DYRK1A aggravates β cell dysfunction and apoptosis by promoting the phosphorylation and degradation of IRS2. Exp Gerontol 2019; 125:110659. [PMID: 31306739 DOI: 10.1016/j.exger.2019.110659] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 07/12/2019] [Accepted: 07/12/2019] [Indexed: 01/21/2023]
Abstract
In this study, we aimed to investigate the role of dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A (DYRK1A), which is one of the most important regulators of Alzheimer's disease development, in islet β cell dysfunction and apoptosis. We found significantly increased expression of DYRK1A in both the hippocampus and pancreatic islets of APPswe/PS1ΔE9 transgenic mice than in wild-type littermates. Furthermore, we observed that the overexpression of DYRK1A greatly aggravated β cell apoptosis. Most importantly, we found that DYRK1A directly interacted with insulin receptor substrate-2 (IRS2) and promoted IRS2 phosphorylation, leading to the proteasomal degradation of IRS2 and promotion of β cell dysfunction and apoptosis. These findings suggested that DYRK1A is a potential drug target in diabetes mellitus.
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Affiliation(s)
- Mei Lu
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China; Shandong Provincial Key laboratory of Cardiovascular Proteomics, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Lin Ma
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China; Shandong Provincial Key laboratory of Cardiovascular Proteomics, Qilu Hospital of Shandong University, Jinan, Shandong, China.
| | - Peiyan Shan
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China; Shandong Provincial Key laboratory of Cardiovascular Proteomics, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Aifen Liu
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Xiaolin Yu
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Wenjing Jiang
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Xinbang Wang
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Xinjing Zhao
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Xiang Ye
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China
| | - Tan Wang
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China
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15
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Orexin-A Stimulates Insulin Secretion Through the Activation of the OX1 Receptor and Mammalian Target of Rapamycin in Rat Insulinoma Cells. Pancreas 2019; 48:568-573. [PMID: 30946236 DOI: 10.1097/mpa.0000000000001280] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVES The study aimed to investigate the involvement of the mammalian target of rapamycin (mTOR) signaling pathway in orexin-A/OX1 receptor-induced insulin secretion in rat insulinoma INS-1 cells. METHODS Rat insulinoma INS-1 cells were grown and treated with various concentrations of orexin-A, with or without OX1 receptor-selective antagonist SB674042 or the phosphatidylinositol 3-kinase/mTOR antagonist PF-04691502. Insulin release experiments, Western blot analysis, and statistical analysis were conducted using INS-1 cells. RESULTS Our results showed that treating cells with orexin-A increased the expression of the OX1 receptor and the phosphorylation of mTOR in a concentration-dependent manner. An increase in insulin secretion was also observed for cells treated with orexin-A. We further demonstrated that the increase in insulin secretion was dependent on the activation of the OX1 receptor and mTOR signaling pathway by using the OX1 receptor-selective antagonist SB674042 or the phosphatidylinositol 3-kinase/mTOR antagonist PF-04691502, which abolished the effects of orexin-A treatment. CONCLUSIONS Our results concluded that orexin-A/OX1 receptor stimulates insulin secretion by activating AKT and its downstream target, mTOR. Therefore, orexins may regulate the energy balance for cell survival with the involvement of mTOR in this process.
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16
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Chiarini F, Evangelisti C, Lattanzi G, McCubrey JA, Martelli AM. Advances in understanding the mechanisms of evasive and innate resistance to mTOR inhibition in cancer cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:1322-1337. [PMID: 30928610 DOI: 10.1016/j.bbamcr.2019.03.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 03/22/2019] [Accepted: 03/26/2019] [Indexed: 12/12/2022]
Abstract
The development of drug-resistance by neoplastic cells is recognized as a major cause of targeted therapy failure and disease progression. The mechanistic (previously mammalian) target of rapamycin (mTOR) is a highly conserved Ser/Thr kinase that acts as the catalytic subunit of two structurally and functionally distinct large multiprotein complexes, referred to as mTOR complex 1 (mTORC1) and mTORC2. Both mTORC1 and mTORC2 play key roles in a variety of healthy cell types/tissues by regulating physiological anabolic and catabolic processes in response to external cues. However, a body of evidence identified aberrant activation of mTOR signaling as a common event in many human tumors. Therefore, mTOR is an attractive target for therapeutic targeting in cancer and this fact has driven the development of numerous mTOR inhibitors, several of which have progressed to clinical trials. Nevertheless, mTOR inhibitors have met with a very limited success as anticancer therapeutics. Among other reasons, this failure was initially ascribed to the activation of several compensatory signaling pathways that dampen the efficacy of mTOR inhibitors. The discovery of these regulatory feedback mechanisms greatly contributed to a better understanding of cancer cell resistance to mTOR targeting agents. However, over the last few years, other mechanisms of resistance have emerged, including epigenetic alterations, compensatory metabolism rewiring and the occurrence of mTOR mutations. In this article, we provide the reader with an updated overview of the mechanisms that could explain resistance of cancer cells to the various classes of mTOR inhibitors.
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Affiliation(s)
- Francesca Chiarini
- CNR Institute of Molecular Genetics, 40136 Bologna, BO, Italy; IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, BO, Italy
| | - Camilla Evangelisti
- CNR Institute of Molecular Genetics, 40136 Bologna, BO, Italy; IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, BO, Italy
| | - Giovanna Lattanzi
- CNR Institute of Molecular Genetics, 40136 Bologna, BO, Italy; IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, BO, Italy
| | - James A McCubrey
- Department of Microbiology & Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA.
| | - Alberto M Martelli
- Department of Biomedical and Neuromotor Sciences, University of Bologna, 40126 Bologna, BO, Italy.
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17
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Waise TMZ, Rasti M, Duca FA, Zhang SY, Bauer PV, Rhodes CJ, Lam TKT. Inhibition of upper small intestinal mTOR lowers plasma glucose levels by inhibiting glucose production. Nat Commun 2019; 10:714. [PMID: 30755615 PMCID: PMC6372624 DOI: 10.1038/s41467-019-08582-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 01/16/2019] [Indexed: 12/11/2022] Open
Abstract
Glucose homeostasis is partly controlled by the energy sensor mechanistic target of rapamycin (mTOR) in the muscle and liver. However, whether mTOR in the small intestine affects glucose homeostasis in vivo remains unknown. Here, we first report that delivery of rapamycin or an adenovirus encoding the dominant negative acting mTOR-mutated protein into the upper small intestine is sufficient to inhibit small intestinal mTOR signaling and lower glucose production in rodents with high fat diet-induced insulin resistance. Second, we found that molecular activation of small intestinal mTOR blunts the glucose-lowering effect of the oral anti-diabetic agent metformin, while inhibiting small intestinal mTOR alone lowers plasma glucose levels by inhibiting glucose production in rodents with diabetes as well. Thus, these findings illustrate that inhibiting upper small intestinal mTOR is sufficient and necessary to lower glucose production and enhance glucose homeostasis, and thereby unveil a previously unappreciated glucose-lowering effect of small intestinal mTOR. The mechanistic target of rapamycin (TOR) functions as an energy sensor and contributes to the control of glucose homeostasis. Here, the authors show that mTOR in the upper small intestine regulates hepatic glucose production and is required for the glucose lowering effect of metformin.
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Affiliation(s)
- T M Zaved Waise
- Toronto General Hospital Research Institute, UHN, Toronto, ON, M5G 1L7, Canada
| | - Mozhgan Rasti
- Toronto General Hospital Research Institute, UHN, Toronto, ON, M5G 1L7, Canada
| | - Frank A Duca
- Toronto General Hospital Research Institute, UHN, Toronto, ON, M5G 1L7, Canada.,School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, 85721, USA
| | - Song-Yang Zhang
- Toronto General Hospital Research Institute, UHN, Toronto, ON, M5G 1L7, Canada
| | - Paige V Bauer
- Toronto General Hospital Research Institute, UHN, Toronto, ON, M5G 1L7, Canada.,Department of Physiology, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Christopher J Rhodes
- Kovler Diabetes Center, Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, University of Chicago, Chicago, IL, 60637, USA.,MedImmune LLC, Gaithersburg, MD, 20878, USA
| | - Tony K T Lam
- Toronto General Hospital Research Institute, UHN, Toronto, ON, M5G 1L7, Canada. .,Department of Physiology, University of Toronto, Toronto, ON, M5S 1A8, Canada. .,Department of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada. .,Banting and Best Diabetes Centre, University of Toronto, Toronto, ON, M5G 2C4, Canada.
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18
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mTOR Inhibitor Therapy and Metabolic Consequences: Where Do We Stand? OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:2640342. [PMID: 30034573 PMCID: PMC6035806 DOI: 10.1155/2018/2640342] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 05/26/2018] [Indexed: 12/16/2022]
Abstract
mTOR (mechanistic target of rapamycin) protein kinase acts as a central integrator of nutrient signaling pathways. Besides the immunosuppressive role after solid organ transplantations or in the treatment of some cancers, another promising role of mTOR inhibitor as an antiaging therapeutic has emerged in the recent years. Acute or intermittent rapamycin treatment has some resemblance to calorie restriction in metabolic effects such as an increased insulin sensitivity. However, the chronic inhibition of mTOR by macrolide rapamycin or other rapalogs has been associated with glucose intolerance and insulin resistance and may even provoke type II diabetes. These metabolic adverse effects limit the use of mTOR inhibitors. Metformin is a widely used drug for the treatment of type 2 diabetes which activates AMP-activated protein kinase (AMPK), acting as calorie restriction mimetic. In addition to the glucose-lowering effect resulting from the decreased hepatic glucose production and increased glucose utilization, metformin induces fatty acid oxidations. Here, we review the recent advances in our understanding of the metabolic consequences regarding glucose metabolism induced by mTOR inhibitors and compare them to the metabolic profile provoked by metformin use. We further suggest metformin use concurrent with rapalogs in order to pharmacologically address the impaired glucose metabolism and prevent the development of new-onset diabetes mellitus after solid organ transplantations induced by the chronic rapalog treatment.
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19
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Tuo Y, Xiang M. mTOR: A double‐edged sword for diabetes. J Leukoc Biol 2018; 106:385-395. [DOI: 10.1002/jlb.3mr0317-095rr] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 09/05/2017] [Accepted: 09/14/2017] [Indexed: 12/14/2022] Open
Affiliation(s)
- Yali Tuo
- Department of PharmacologySchool of PharmacyTongji Medical CollegeHuazhong University of Science and Technology Wuhan China
| | - Ming Xiang
- Department of PharmacologySchool of PharmacyTongji Medical CollegeHuazhong University of Science and Technology Wuhan China
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20
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Torii S, Kubota C, Saito N, Kawano A, Hou N, Kobayashi M, Torii R, Hosaka M, Kitamura T, Takeuchi T, Gomi H. The pseudophosphatase phogrin enables glucose-stimulated insulin signaling in pancreatic β cells. J Biol Chem 2018; 293:5920-5933. [PMID: 29483197 DOI: 10.1074/jbc.ra117.000301] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 02/14/2018] [Indexed: 12/18/2022] Open
Abstract
Autocrine insulin signaling is critical for pancreatic β-cell growth and activity and is at least partially controlled by protein-tyrosine phosphatases (PTPs) that act on insulin receptors (IRs). The receptor-type PTP phogrin primarily localizes on insulin secretory granules in pancreatic β cells. We recently reported that phogrin knockdown decreases the protein levels of insulin receptor substrate 2 (IRS2), whereas high-glucose stimulation promotes formation of a phogrin-IR complex that stabilizes IRS2. However, the underlying molecular mechanisms by which phogrin affects IRS2 levels are unclear. Here, we found that relative to wildtype mice, IRS2 levels in phogrin-knockout mice islets decreased by 44%. When phogrin was silenced by shRNA in pancreatic β-cell lines, glucose-induced insulin signaling led to proteasomal degradation of IRS2 via a negative feedback mechanism. Phogrin overexpression in a murine hepatocyte cell line consistently prevented chronic insulin treatment-induced IRS2 degradation. In vitro, phogrin directly bound the IR without the assistance of other proteins and protected recombinant PTP1B from oxidation to potentiate its activity toward the IR. Furthermore, phogrin expression suppressed insulin-induced local generation of hydrogen peroxide and subsequent PTP1B oxidation, which allowed progression of IR dephosphorylation. Together, these results suggest that a transient interaction of phogrin with the IR enables glucose-stimulated autocrine insulin signaling through the regulation of PTP1B activity, which is essential for suppressing feedback-mediated IRS2 degradation in pancreatic β cells.
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Affiliation(s)
| | | | | | | | - Ni Hou
- From the Biosignal Research Center and
| | - Masaki Kobayashi
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | | | - Masahiro Hosaka
- the Department of Biotechnology, Akita Prefectural University, Akita 010-0195, Japan
| | - Tadahiro Kitamura
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Toshiyuki Takeuchi
- From the Biosignal Research Center and.,the Administration Office, Gunma University, Maebashi, Gunma 371-8512, Japan, and
| | - Hiroshi Gomi
- the Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Kanagawa 252-8510, Japan
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21
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Ye R, Gordillo R, Shao M, Onodera T, Chen Z, Chen S, Lin X, SoRelle JA, Li X, Tang M, Keller MP, Kuliawat R, Attie AD, Gupta RK, Holland WL, Beutler B, Herz J, Scherer PE. Intracellular lipid metabolism impairs β cell compensation during diet-induced obesity. J Clin Invest 2018; 128:1178-1189. [PMID: 29457786 DOI: 10.1172/jci97702] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 01/09/2018] [Indexed: 12/16/2022] Open
Abstract
The compensatory proliferation of insulin-producing β cells is critical to maintaining glucose homeostasis at the early stage of type 2 diabetes. Failure of β cells to proliferate results in hyperglycemia and insulin dependence in patients. To understand the effect of the interplay between β cell compensation and lipid metabolism upon obesity and peripheral insulin resistance, we eliminated LDL receptor-related protein 1 (LRP1), a pleiotropic mediator of cholesterol, insulin, energy metabolism, and other cellular processes, in β cells. Upon high-fat diet exposure, LRP1 ablation significantly impaired insulin secretion and proliferation of β cells. The diminished insulin signaling was partly contributed to by the hypersensitivity to glucose-induced, Ca2+-dependent activation of Erk and the mTORC1 effector p85 S6K1. Surprisingly, in LRP1-deficient islets, lipotoxic sphingolipids were mitigated by improved lipid metabolism, mediated at least in part by the master transcriptional regulator PPARγ2. Acute overexpression of PPARγ2 in β cells impaired insulin signaling and insulin secretion. Elimination of Apbb2, a functional regulator of LRP1 cytoplasmic domain, also impaired β cell function in a similar fashion. In summary, our results uncover the double-edged effects of intracellular lipid metabolism on β cell function and viability in obesity and type 2 diabetes and highlight LRP1 as an essential regulator of these processes.
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Affiliation(s)
- Risheng Ye
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA.,Department of Medical Education, Texas Tech University Health Sciences Center Paul L. Foster School of Medicine, El Paso, Texas, USA
| | - Ruth Gordillo
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Mengle Shao
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Toshiharu Onodera
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Zhe Chen
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA.,Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Shiuhwei Chen
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Xiaoli Lin
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Jeffrey A SoRelle
- Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Xiaohong Li
- Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Miao Tang
- Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, USA
| | - Regina Kuliawat
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, USA
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, USA
| | - Rana K Gupta
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - William L Holland
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
| | - Bruce Beutler
- Center for the Genetics of Host Defense, UTSW Medical Center, Dallas, Texas, USA
| | - Joachim Herz
- Departments of Molecular Genetics, Neuroscience, Neurology and Neurotherapeutics, and Center for Translational Neurodegeneration Research, UTSW Medical Center, Dallas, Texas, USA.,Center for Neuroscience, Department of Neuroanatomy, Albert Ludwig University, Freiburg, Germany
| | - Philipp E Scherer
- Touchstone Diabetes Center, Department of Internal Medicine, University of Texas Southwestern (UTSW) Medical Center, Dallas, Texas, USA
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22
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Ardestani A, Lupse B, Kido Y, Leibowitz G, Maedler K. mTORC1 Signaling: A Double-Edged Sword in Diabetic β Cells. Cell Metab 2018; 27:314-331. [PMID: 29275961 DOI: 10.1016/j.cmet.2017.11.004] [Citation(s) in RCA: 124] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 10/11/2017] [Accepted: 11/15/2017] [Indexed: 12/21/2022]
Abstract
The mechanistic target of rapamycin complex 1 (mTORC1) is a central regulator of metabolic and nutrient cues that integrates environmental inputs into downstream signaling pathways to control cellular metabolism, growth, and survival. While numerous in vitro and in vivo studies reported the positive functions of mTORC1 in the regulation of β cell survival and proliferation under physiological conditions, more recent work demonstrates the opposite in the long term; this is exemplified by the constitutive inappropriate hyper-activation of mTORC1 in diabetic islets or β cells under conditions of increased β cell stress and metabolic demands. These recent findings uncover mTORC1's importance as an emerging significant player in the development and progression of β cell failure in type 2 diabetes and suggest that mTORC1 may act as a "double edge sword" in the regulation of β cell mass and function in response to metabolic stress such as nutrient overload and insulin resistance.
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Affiliation(s)
- Amin Ardestani
- University of Bremen, Centre for Biomolecular Interactions Bremen, Bremen 28359, Germany.
| | - Blaz Lupse
- University of Bremen, Centre for Biomolecular Interactions Bremen, Bremen 28359, Germany
| | - Yoshiaki Kido
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan; Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe 654-0142, Japan
| | - Gil Leibowitz
- Endocrinology and Metabolism Service and the Hadassah Diabetes Unit, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Kathrin Maedler
- University of Bremen, Centre for Biomolecular Interactions Bremen, Bremen 28359, Germany.
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Yuan T, Rafizadeh S, Gorrepati KDD, Lupse B, Oberholzer J, Maedler K, Ardestani A. Reciprocal regulation of mTOR complexes in pancreatic islets from humans with type 2 diabetes. Diabetologia 2017; 60:668-678. [PMID: 28004151 DOI: 10.1007/s00125-016-4188-9] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 12/02/2016] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of nutritional status at the cellular and organismic level. While mTORC1 mediates beta cell growth and expansion, its hyperactivation has been observed in pancreatic islets from animal models of type 2 diabetes and leads to beta cell loss. We sought to determine whether such mTORC1 activation occurs in humans with type 2 diabetes or in metabolically stressed human islets and whether mTORC1 blockade can restore beta cell function of diabetic islets. METHODS Human islets isolated from non-diabetic controls and individuals with type 2 diabetes, as well as human islets and INS-1E cells exposed to increased glucose (22.2 mmol/l), were examined for mTORC1/2 activity by western blotting analysis of phosphorylation of mTORC1 downstream targets ribosomal protein S6 kinase 1 (S6K1), S6 and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1) and mTORC2 downstream targets Akt and N-myc downstream regulated 1 (NDRG1). mTORC1/2 complexes' integrity was assessed by immunoprecipitation and subsequent western blot analysis. Cell-type specific expression of activated mTORC1 in human islets was examined by immunostaining of pS6 (Ser 235/236) in human islet sections. Beta cell function was measured by glucose-stimulated insulin secretion (GSIS). RESULTS While mTORC2 signalling was diminished, mTORC1 activity was markedly increased in islets from patients with type 2 diabetes and in islets and beta cells exposed to increased glucose concentrations. Under high-glucose conditions in metabolically stressed human islets, we identified a reciprocal regulation of different mTOR complexes, with functional upregulation of mTORC1 and downregulation of mTORC2. pS6 immunostaining showed beta cell-specific upregulation of mTORC1 in islets isolated from patients with type 2 diabetes. Inhibition of mTORC1-S6K1 signalling improved GSIS and restored mTORC2 activity in islets from patients with type 2 diabetes as well as in islets isolated from diabetic db/db mice and mice fed a high-fat/high-sucrose diet. CONCLUSIONS/INTERPRETATION Our data show the aberrant mTORC1 activity in islets from patients with type 2 diabetes, in human islets cultured under diabetes-associated increased glucose conditions and in diabetic mouse islets. This suggests that elevated mTORC1 activation is a striking pathogenic hallmark of islets in type 2 diabetes, contributing to impaired beta cell function and survival in the presence of metabolic stress.
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Affiliation(s)
- Ting Yuan
- Islet Biology Laboratory, Centre for Biomolecular Interactions Bremen, University of Bremen, Leobener Straße NW2, Room B2080, 28359, Bremen, Germany
| | - Sahar Rafizadeh
- Islet Biology Laboratory, Centre for Biomolecular Interactions Bremen, University of Bremen, Leobener Straße NW2, Room B2080, 28359, Bremen, Germany
| | - Kanaka Durga Devi Gorrepati
- Islet Biology Laboratory, Centre for Biomolecular Interactions Bremen, University of Bremen, Leobener Straße NW2, Room B2080, 28359, Bremen, Germany
| | - Blaz Lupse
- Islet Biology Laboratory, Centre for Biomolecular Interactions Bremen, University of Bremen, Leobener Straße NW2, Room B2080, 28359, Bremen, Germany
| | - Jose Oberholzer
- Division of Transplantation, University of Illinois at Chicago, Chicago, IL, USA
| | - Kathrin Maedler
- Islet Biology Laboratory, Centre for Biomolecular Interactions Bremen, University of Bremen, Leobener Straße NW2, Room B2080, 28359, Bremen, Germany.
- German Center for Diabetes Research (DZD) project partner, University of Bremen, Bremen, Germany.
| | - Amin Ardestani
- Islet Biology Laboratory, Centre for Biomolecular Interactions Bremen, University of Bremen, Leobener Straße NW2, Room B2080, 28359, Bremen, Germany.
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24
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A systems study reveals concurrent activation of AMPK and mTOR by amino acids. Nat Commun 2016; 7:13254. [PMID: 27869123 PMCID: PMC5121333 DOI: 10.1038/ncomms13254] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 09/13/2016] [Indexed: 12/17/2022] Open
Abstract
Amino acids (aa) are not only building blocks for proteins, but also signalling molecules, with the mammalian target of rapamycin complex 1 (mTORC1) acting as a key mediator. However, little is known about whether aa, independently of mTORC1, activate other kinases of the mTOR signalling network. To delineate aa-stimulated mTOR network dynamics, we here combine a computational–experimental approach with text mining-enhanced quantitative proteomics. We report that AMP-activated protein kinase (AMPK), phosphatidylinositide 3-kinase (PI3K) and mTOR complex 2 (mTORC2) are acutely activated by aa-readdition in an mTORC1-independent manner. AMPK activation by aa is mediated by Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ). In response, AMPK impinges on the autophagy regulators Unc-51-like kinase-1 (ULK1) and c-Jun. AMPK is widely recognized as an mTORC1 antagonist that is activated by starvation. We find that aa acutely activate AMPK concurrently with mTOR. We show that AMPK under aa sufficiency acts to sustain autophagy. This may be required to maintain protein homoeostasis and deliver metabolite intermediates for biosynthetic processes. mTORC1 is known to mediate the signalling activity of amino acids. Here, the authors combine modelling with experiments and find that amino acids acutely stimulate mTORC2, IRS/PI3K and AMPK, independently of mTORC1. AMPK activation through CaMKKβ sustains autophagy under non-starvation conditions.
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25
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Ong PS, Wang LZ, Dai X, Tseng SH, Loo SJ, Sethi G. Judicious Toggling of mTOR Activity to Combat Insulin Resistance and Cancer: Current Evidence and Perspectives. Front Pharmacol 2016; 7:395. [PMID: 27826244 PMCID: PMC5079084 DOI: 10.3389/fphar.2016.00395] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/07/2016] [Indexed: 12/16/2022] Open
Abstract
The mechanistic target of rapamycin (mTOR), via its two distinct multiprotein complexes, mTORC1, and mTORC2, plays a central role in the regulation of cellular growth, metabolism, and migration. A dysregulation of the mTOR pathway has in turn been implicated in several pathological conditions including insulin resistance and cancer. Overactivation of mTORC1 and disruption of mTORC2 function have been reported to induce insulin resistance. On the other hand, aberrant mTORC1 and mTORC2 signaling via either genetic alterations or increased expression of proteins regulating mTOR and its downstream targets have contributed to cancer development. These underlined the attractiveness of mTOR as a therapeutic target to overcome both insulin resistance and cancer. This review summarizes the evidence supporting the notion of intermittent, low dose rapamycin for treating insulin resistance. It further highlights recent data on the continuous use of high dose rapamycin analogs and related second generation mTOR inhibitors for cancer eradication, for overcoming chemoresistance and for tumor stem cell suppression. Within these contexts, the potential challenges associated with the use of mTOR inhibitors are also discussed.
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Affiliation(s)
- Pei Shi Ong
- Department of Pharmacy, Faculty of Science, National University of Singapore Singapore, Singapore
| | - Louis Z Wang
- Department of Pharmacy, Faculty of Science, National University of SingaporeSingapore, Singapore; Department of Pharmacology, Yong Loo Lin School of Medicine, National University of SingaporeSingapore, Singapore
| | - Xiaoyun Dai
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore Singapore, Singapore
| | - Sheng Hsuan Tseng
- Department of Pharmacy, Faculty of Science, National University of Singapore Singapore, Singapore
| | - Shang Jun Loo
- Department of Pharmacy, Faculty of Science, National University of Singapore Singapore, Singapore
| | - Gautam Sethi
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore Singapore, Singapore
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26
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Bucris E, Beck A, Boura-Halfon S, Isaac R, Vinik Y, Rosenzweig T, Sampson SR, Zick Y. Prolonged insulin treatment sensitizes apoptosis pathways in pancreatic β cells. J Endocrinol 2016; 230:291-307. [PMID: 27411561 DOI: 10.1530/joe-15-0505] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 06/27/2016] [Indexed: 12/11/2022]
Abstract
Insulin resistance results from impaired insulin signaling in target tissues that leads to increased levels of insulin required to control plasma glucose levels. The cycle of hyperglycemia and hyperinsulinemia eventually leads to pancreatic cell deterioration and death by a mechanism that is yet unclear. Insulin induces ROS formation in several cell types. Furthermore, death of pancreatic cells induced by oxidative stress could be potentiated by insulin. Here, we investigated the mechanism underlying this phenomenon. Experiments were done on pancreatic cell lines (Min-6, RINm, INS-1), isolated mouse and human islets, and on cell lines derived from nonpancreatic sources. Insulin (100nM) for 24h selectively increased the production of ROS in pancreatic cells and isolated pancreatic islets, but only slightly affected the expression of antioxidant enzymes. This was accompanied by a time- and dose-dependent decrease in cellular reducing power of pancreatic cells induced by insulin and altered expression of several ER stress response elements including a significant increase in Trb3 and a slight increase in iNos The effect on iNos did not increase NO levels. Insulin also potentiated the decrease in cellular reducing power induced by H2O2 but not cytokines. Insulin decreased the expression of MCL-1, an antiapoptotic protein of the BCL family, and induced a modest yet significant increase in caspase 3/7 activity. In accord with these findings, inhibition of caspase activity eliminated the ability of insulin to increase cell death. We conclude that prolonged elevated levels of insulin may prime apoptosis and cell death-inducing mechanisms as a result of oxidative stress in pancreatic cells.
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Affiliation(s)
- E Bucris
- Department of Molecular Cell BiologyWeizmann Institute of Science, Rehovot, Israel Mina and Everard Goodman Faculty of Life SciencesBar-Ilan University, Ramat-Gan, Israel
| | - A Beck
- Department of Molecular Cell BiologyWeizmann Institute of Science, Rehovot, Israel
| | - S Boura-Halfon
- Department of Molecular Cell BiologyWeizmann Institute of Science, Rehovot, Israel
| | - R Isaac
- Department of Molecular Cell BiologyWeizmann Institute of Science, Rehovot, Israel
| | - Y Vinik
- Department of Molecular Cell BiologyWeizmann Institute of Science, Rehovot, Israel
| | - T Rosenzweig
- Department of Molecular Biology and Nutritional StudiesAriel University, Ariel, Israel
| | - S R Sampson
- Department of Molecular Cell BiologyWeizmann Institute of Science, Rehovot, Israel Mina and Everard Goodman Faculty of Life SciencesBar-Ilan University, Ramat-Gan, Israel
| | - Y Zick
- Department of Molecular Cell BiologyWeizmann Institute of Science, Rehovot, Israel
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Blandino-Rosano M, Scheys JO, Jimenez-Palomares M, Barbaresso R, Bender AS, Yanagiya A, Liu M, Rui L, Sonenberg N, Bernal-Mizrachi E. 4E-BP2/SH2B1/IRS2 Are Part of a Novel Feedback Loop That Controls β-Cell Mass. Diabetes 2016; 65:2235-48. [PMID: 27217487 PMCID: PMC4955981 DOI: 10.2337/db15-1443] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 05/09/2016] [Indexed: 01/08/2023]
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) regulates several biological processes, although the key downstream mechanisms responsible for these effects are poorly defined. Using mice with deletion of eukaryotic translation initiation factor 4E-binding protein 2 (4E-BP2), we determine that this downstream target is a major regulator of glucose homeostasis and β-cell mass, proliferation, and survival by increasing insulin receptor substrate 2 (IRS2) levels and identify a novel feedback mechanism by which mTORC1 signaling increases IRS2 levels. In this feedback loop, we show that 4E-BP2 deletion induces translation of the adaptor protein SH2B1 and promotes the formation of a complex with IRS2 and Janus kinase 2, preventing IRS2 ubiquitination. The changes in IRS2 levels result in increases in cell cycle progression, cell survival, and β-cell mass by increasing Akt signaling and reducing p27 levels. Importantly, 4E-BP2 deletion confers resistance to cytokine treatment in vitro. Our data identify SH2B1 as a major regulator of IRS2 stability, demonstrate a novel feedback mechanism linking mTORC1 signaling with IRS2, and identify 4E-BP2 as a major regulator of proliferation and survival of β-cells.
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Affiliation(s)
- Manuel Blandino-Rosano
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Joshua O Scheys
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Margarita Jimenez-Palomares
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Rebecca Barbaresso
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Aaron S Bender
- Diabetes, Obesity and Metabolism Institute, The Icahn School of Medicine at Mount Sinai, New York, NY
| | - Akiko Yanagiya
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Liangyou Rui
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Ernesto Bernal-Mizrachi
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI VA Ann Arbor Healthcare System, Ann Arbor, MI
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Stamateris RE, Sharma RB, Kong Y, Ebrahimpour P, Panday D, Ranganath P, Zou B, Levitt H, Parambil NA, O'Donnell CP, García-Ocaña A, Alonso LC. Glucose Induces Mouse β-Cell Proliferation via IRS2, MTOR, and Cyclin D2 but Not the Insulin Receptor. Diabetes 2016; 65:981-95. [PMID: 26740601 PMCID: PMC5314707 DOI: 10.2337/db15-0529] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Accepted: 12/29/2015] [Indexed: 12/21/2022]
Abstract
An important goal in diabetes research is to understand the processes that trigger endogenous β-cell proliferation. Hyperglycemia induces β-cell replication, but the mechanism remains debated. A prime candidate is insulin, which acts locally through the insulin receptor. Having previously developed an in vivo mouse hyperglycemia model, we tested whether glucose induces β-cell proliferation through insulin signaling. By using mice lacking insulin signaling intermediate insulin receptor substrate 2 (IRS2), we confirmed that hyperglycemia-induced β-cell proliferation requires IRS2 both in vivo and ex vivo. Of note, insulin receptor activation was not required for glucose-induced proliferation, and insulin itself was not sufficient to drive replication. Glucose and insulin caused similar acute signaling in mouse islets, but chronic signaling differed markedly, with mammalian target of rapamycin (MTOR) and extracellular signal-related kinase (ERK) activation by glucose and AKT activation by insulin. MTOR but not ERK activation was required for glucose-induced proliferation. Cyclin D2 was necessary for glucose-induced β-cell proliferation. Cyclin D2 expression was reduced when either IRS2 or MTOR signaling was lost, and restoring cyclin D2 expression rescued the proliferation defect. Human islets shared many of these regulatory pathways. Taken together, these results support a model in which IRS2, MTOR, and cyclin D2, but not the insulin receptor, mediate glucose-induced proliferation.
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Affiliation(s)
- Rachel E Stamateris
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Rohit B Sharma
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Yahui Kong
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Pantea Ebrahimpour
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Deepika Panday
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Pavana Ranganath
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Baobo Zou
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Helena Levitt
- Division of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | | | - Christopher P O'Donnell
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Adolfo García-Ocaña
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Disease, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Laura C Alonso
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
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29
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Kuznetsova A, Yu Y, Hollister-Lock J, Opare-Addo L, Rozzo A, Sadagurski M, Norquay L, Reed JE, El Khattabi I, Bonner-Weir S, Weir GC, Sharma A, White MF. Trimeprazine increases IRS2 in human islets and promotes pancreatic β cell growth and function in mice. JCI Insight 2016; 1. [PMID: 27152363 PMCID: PMC4854304 DOI: 10.1172/jci.insight.80749] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The capacity of pancreatic β cells to maintain glucose homeostasis during chronic physiologic and immunologic stress is important for cellular and metabolic homeostasis. Insulin receptor substrate 2 (IRS2) is a regulated adapter protein that links the insulin and IGF1 receptors to downstream signaling cascades. Since strategies to maintain or increase IRS2 expression can promote β cell growth, function, and survival, we conducted a screen to find small molecules that can increase IRS2 mRNA in isolated human pancreatic islets. We identified 77 compounds, including 15 that contained a tricyclic core. To establish the efficacy of our approach, one of the tricyclic compounds, trimeprazine tartrate, was investigated in isolated human islets and in mouse models. Trimeprazine is a first-generation antihistamine that acts as a partial agonist against the histamine H1 receptor (H1R) and other GPCRs, some of which are expressed on human islets. Trimeprazine promoted CREB phosphorylation and increased the concentration of IRS2 in islets. IRS2 was required for trimeprazine to increase nuclear Pdx1, islet mass, β cell replication and function, and glucose tolerance in mice. Moreover, trimeprazine synergized with anti-CD3 Abs to reduce the progression of diabetes in NOD mice. Finally, it increased the function of human islet transplants in streptozotocin-induced (STZ-induced) diabetic mice. Thus, trimeprazine, its analogs, or possibly other compounds that increase IRS2 in islets and β cells without adverse systemic effects might provide mechanism-based strategies to prevent the progression of diabetes.
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Affiliation(s)
- Alexandra Kuznetsova
- Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Yue Yu
- Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Jennifer Hollister-Lock
- Section of Islet Cell and Regenerative Biology, Department of Medicine, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Lynn Opare-Addo
- Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Aldo Rozzo
- Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Marianna Sadagurski
- Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Lisa Norquay
- Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Jessica E Reed
- Housey Pharmaceutical Research Laboratories, Southfield, Michigan, USA
| | - Ilham El Khattabi
- Section of Islet Cell and Regenerative Biology, Department of Medicine, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Susan Bonner-Weir
- Section of Islet Cell and Regenerative Biology, Department of Medicine, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Gordon C Weir
- Section of Islet Cell and Regenerative Biology, Department of Medicine, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Arun Sharma
- Section of Islet Cell and Regenerative Biology, Department of Medicine, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Morris F White
- Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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mTOR Inhibition: Reduced Insulin Secretion and Sensitivity in a Rat Model of Metabolic Syndrome. Transplant Direct 2016; 2:e65. [PMID: 27500257 PMCID: PMC4946492 DOI: 10.1097/txd.0000000000000576] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 12/22/2015] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Sirolimus (SRL) has been associated with new-onset diabetes mellitus after transplantation. The aim was to determine the effect of SRL on development of insulin resistance and β -cell toxicity. METHODS Lean Zucker rat (LZR) and obese Zucker rat (OZR) were distributed into groups: vehicle and SRL (0.25, 0.5, or 1.0 mg/kg) during 12 or 28 days. Intraperitoneal glucose tolerance test (IPGTT) was evaluated at days 0, 12, 28, and 45. Islet morphometry, β-cell proliferation, and apoptosis were analyzed at 12 days. Islets were isolated to analyze insulin content, insulin secretion, and gene expression. RESULTS After 12 days, SRL treatment only impaired IPGTT in a dose-dependent manner in OZR. Treatment prolongation induced increase of area under the curve of IPGTT in LZR and OZR; however, in contrast to OZR, LZR normalized glucose levels after 2 hours. The SRL reduced pancreas weight and islet proliferation in LZR and OZR as well as insulin content. Insulin secretion was only affected in OZR. Islets from OZR + SRL rats presented a downregulation of Neurod1, Pax4, and Ins2 gene. Genes related with insulin secretion remained unchanged or upregulated. CONCLUSIONS In conditions that require adaptive β -cell proliferation, SRL might reveal harmful effects by blocking β -cell proliferation, insulin production and secretion. These effects disappeared when removing the therapy.
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31
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Coffey RT, Shi Y, Long MJC, Marr MT, Hedstrom L. Ubiquilin-mediated Small Molecule Inhibition of Mammalian Target of Rapamycin Complex 1 (mTORC1) Signaling. J Biol Chem 2016; 291:5221-33. [PMID: 26740621 DOI: 10.1074/jbc.m115.691584] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Indexed: 12/14/2022] Open
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) is a master regulator of cellular metabolism, growth, and proliferation. mTORC1 has been implicated in many diseases such as cancer, diabetes, and neurodegeneration, and is a target to prolong lifespan. Here we report a small molecule inhibitor (Cbz-B3A) of mTORC1 signaling. Cbz-B3A inhibits the phosphorylation of eIF4E-binding protein 1 (4EBP1) and blocks 68% of translation. In contrast, rapamycin preferentially inhibits the phosphorylation of p70(S6k) and blocks 35% of translation. Cbz-B3A does not appear to bind directly to mTORC1, but instead binds to ubiquilins 1, 2, and 4. Knockdown of ubiquilin 2, but not ubiquilins 1 and 4, decreases the phosphorylation of 4EBP1, suggesting that ubiquilin 2 activates mTORC1. The knockdown of ubiquilins 2 and 4 decreases the effect of Cbz-B3A on 4EBP1 phosphorylation. Cbz-B3A slows cellular growth of some human leukemia cell lines, but is not cytotoxic. Thus Cbz-B3A exemplifies a novel strategy to inhibit mTORC1 signaling that might be exploited for treating many human diseases. We propose that Cbz-B3A reveals a previously unappreciated regulatory pathway coordinating cytosolic protein quality control and mTORC1 signaling.
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Affiliation(s)
- Rory T Coffey
- From the Graduate Program in Molecular and Cellular Biology, MS008
| | - Yuntao Shi
- the Graduate Program in Chemistry, MS015
| | | | - Michael T Marr
- the Department of Biology, MS009 and Rosenstiel Basic Medical Sciences Research Center, MS029, and
| | - Lizbeth Hedstrom
- the Department of Biology, MS009 and the Department of Chemistry, Brandeis University, Waltham, Massachusetts 02453-9110
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Inflammasome, mTORC1 activation, and metabolic derangement contribute to the susceptibility of diabetics to infections. Med Hypotheses 2015; 85:997-1001. [DOI: 10.1016/j.mehy.2015.08.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 08/30/2015] [Indexed: 12/12/2022]
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Yin Y, Hua H, Li M, Liu S, Kong Q, Shao T, Wang J, Luo Y, Wang Q, Luo T, Jiang Y. mTORC2 promotes type I insulin-like growth factor receptor and insulin receptor activation through the tyrosine kinase activity of mTOR. Cell Res 2015; 26:46-65. [PMID: 26584640 DOI: 10.1038/cr.2015.133] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 09/15/2015] [Accepted: 10/08/2015] [Indexed: 02/05/2023] Open
Abstract
Mammalian target of rapamycin (mTOR) is a core component of raptor-mTOR (mTORC1) and rictor-mTOR (mTORC2) complexes that control diverse cellular processes. Both mTORC1 and mTORC2 regulate several elements downstream of type I insulin-like growth factor receptor (IGF-IR) and insulin receptor (InsR). However, it is unknown whether and how mTOR regulates IGF-IR and InsR themselves. Here we show that mTOR possesses unexpected tyrosine kinase activity and activates IGF-IR/InsR. Rapamycin induces the tyrosine phosphorylation and activation of IGF-IR/InsR, which is largely dependent on rictor and mTOR. Moreover, mTORC2 promotes ligand-induced activation of IGF-IR/InsR. IGF- and insulin-induced IGF-IR/InsR phosphorylation is significantly compromised in rictor-null cells. Insulin receptor substrate (IRS) directly interacts with SIN1 thereby recruiting mTORC2 to IGF-IR/InsR and promoting rapamycin- or ligand-induced phosphorylation of IGF-IR/InsR. mTOR exhibits tyrosine kinase activity towards the general tyrosine kinase substrate poly(Glu-Tyr) and IGF-IR/InsR. Both recombinant mTOR and immunoprecipitated mTORC2 phosphorylate IGF-IR and InsR on Tyr1131/1136 and Tyr1146/1151, respectively. These effects are independent of the intrinsic kinase activity of IGF-IR/InsR, as determined by assays on kinase-dead IGF-IR/InsR mutants. While both rictor and mTOR immunoprecitates from rictor(+/+) MCF-10A cells exhibit tyrosine kinase activity towards IGF-IR and InsR, mTOR immunoprecipitates from rictor(-/-) MCF-10A cells do not induce IGF-IR and InsR phosphorylation. Phosphorylation-deficient mutation of residue Tyr1131 in IGF-IR or Tyr1146 in InsR abrogates the activation of IGF-IR/InsR by mTOR. Finally, overexpression of rictor promotes IGF-induced cell proliferation. Our work identifies mTOR as a dual-specificity kinase and clarifies how mTORC2 promotes IGF-IR/InsR activation.
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Affiliation(s)
- Yancun Yin
- State Key Laboratory of Biotherapy, Section of Oncogene, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Hui Hua
- Laboratory of Stem Cell Biology, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Minjing Li
- Medicine and Pharmacy Research Center, Binzhou Medical University, Yantai, Shandong 264003, China
| | - Shu Liu
- State Key Laboratory of Biotherapy, Section of Oncogene, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Qingbin Kong
- State Key Laboratory of Biotherapy, Section of Oncogene, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Ting Shao
- State Key Laboratory of Biotherapy, Section of Oncogene, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Jiao Wang
- School of Basic Medicine, Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan 610075, China
| | - Yuanming Luo
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Qian Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
| | - Ting Luo
- Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Yangfu Jiang
- State Key Laboratory of Biotherapy, Section of Oncogene, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
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Bermudez-Silva FJ, Romero-Zerbo SY, Haissaguerre M, Ruz-Maldonado I, Lhamyani S, El Bekay R, Tabarin A, Marsicano G, Cota D. The cannabinoid CB1 receptor and mTORC1 signalling pathways interact to modulate glucose homeostasis in mice. Dis Model Mech 2015; 9:51-61. [PMID: 26563389 PMCID: PMC4728331 DOI: 10.1242/dmm.020750] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 11/02/2015] [Indexed: 12/31/2022] Open
Abstract
The endocannabinoid system (ECS) is an intercellular signalling mechanism that is present in the islets of Langerhans and plays a role in the modulation of insulin secretion and expansion of the β-cell mass. The downstream signalling pathways mediating these effects are poorly understood. Mammalian target of rapamycin complex 1 (mTORC1) signalling is a key intracellular pathway involved in energy homeostasis and is known to importantly affect the physiology of pancreatic islets. We investigated the possible relationship between cannabinoid type 1 (CB1) receptor signalling and the mTORC1 pathway in the endocrine pancreas of mice by using pharmacological analysis as well as mice genetically lacking the CB1 receptor or the downstream target of mTORC1, the kinase p70S6K1. In vitro static secretion experiments on islets, western blotting, and in vivo glucose and insulin tolerance tests were performed. The CB1 receptor antagonist rimonabant decreased glucose-stimulated insulin secretion (GSIS) at 0.1 µM while increasing phosphorylation of p70S6K1 and ribosomal protein S6 (rpS6) within the islets. Specific pharmacological blockade of mTORC1 by 3 nM rapamycin, as well as genetic deletion of p70S6K1, impaired the CB1-antagonist-mediated decrease in GSIS. In vivo experiments showed that 3 mg/kg body weight rimonabant decreased insulin levels and induced glucose intolerance in lean mice without altering peripheral insulin sensitivity; this effect was prevented by peripheral administration of low doses of rapamycin (0.1 mg/kg body weight), which increased insulin sensitivity. These findings suggest a functional interaction between the ECS and the mTORC1 pathway within the endocrine pancreas and at the whole-organism level, which could have implications for the development of new therapeutic approaches for pancreatic β-cell diseases. Summary: Evidence supporting a functional interaction between the endocannabinoid system and the mTORC1 pathway within the endocrine pancreas, which could have implications for the development of new therapeutic approaches for diabetes.
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Affiliation(s)
- Francisco J Bermudez-Silva
- Unidad de Gestion Clínica Intercentros de Endocrinología y Nutrición, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga/Universidad de Málaga, Málaga 29009, Spain Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Málaga 29009, Spain INSERM, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France Université de Bordeaux, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France
| | - Silvana Y Romero-Zerbo
- Unidad de Gestion Clínica Intercentros de Endocrinología y Nutrición, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga/Universidad de Málaga, Málaga 29009, Spain Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Málaga 29009, Spain
| | - Magalie Haissaguerre
- INSERM, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France Université de Bordeaux, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France
| | - Inmaculada Ruz-Maldonado
- Unidad de Gestion Clínica Intercentros de Endocrinología y Nutrición, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga/Universidad de Málaga, Málaga 29009, Spain Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Málaga 29009, Spain
| | - Said Lhamyani
- Unidad de Gestion Clínica Intercentros de Endocrinología y Nutrición, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga/Universidad de Málaga, Málaga 29009, Spain
| | - Rajaa El Bekay
- Unidad de Gestion Clínica Intercentros de Endocrinología y Nutrición, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga/Universidad de Málaga, Málaga 29009, Spain
| | - Antoine Tabarin
- INSERM, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France Université de Bordeaux, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France Service d'endocrinologie, diabétologie, maladies métaboliques et nutrition, Hôpital Haut-Lévêque, Pessac F-33604, France
| | - Giovanni Marsicano
- INSERM, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France Université de Bordeaux, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France
| | - Daniela Cota
- INSERM, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France Université de Bordeaux, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U862, Bordeaux F-33000, France
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Das R, Xu S, Nguyen TT, Quan X, Choi SK, Kim SJ, Lee EY, Cha SK, Park KS. Transforming Growth Factor β1-induced Apoptosis in Podocytes via the Extracellular Signal-regulated Kinase-Mammalian Target of Rapamycin Complex 1-NADPH Oxidase 4 Axis. J Biol Chem 2015; 290:30830-42. [PMID: 26565025 DOI: 10.1074/jbc.m115.703116] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Indexed: 02/04/2023] Open
Abstract
TGF-β is a pleiotropic cytokine that accumulates during kidney injuries, resulting in various renal diseases. We have reported previously that TGF-β1 induces the selective up-regulation of mitochondrial Nox4, playing critical roles in podocyte apoptosis. Here we investigated the regulatory mechanism of Nox4 up-regulation by mTORC1 activation on TGF-β1-induced apoptosis in immortalized podocytes. TGF-β1 treatment markedly increased the phosphorylation of mammalian target of rapamycin (mTOR) and its downstream targets p70S6K and 4EBP1. Blocking TGF-β receptor I with SB431542 completely blunted the phosphorylation of mTOR, p70S6K, and 4EBP1. Transient adenoviral overexpression of mTOR-WT and constitutively active mTORΔ augmented TGF-β1-treated Nox4 expression, reactive oxygen species (ROS) generation, and apoptosis, whereas mTOR kinase-dead suppressed the above changes. In addition, knockdown of mTOR mimicked the effect of mTOR-KD. Inhibition of mTORC1 by low-dose rapamycin or knockdown of p70S6K protected podocytes through attenuation of Nox4 expression and subsequent oxidative stress-induced apoptosis by TGF-β1. Pharmacological inhibition of the MEK-ERK cascade, but not the PI3K-Akt-TSC2 pathway, abolished TGF-β1-induced mTOR activation. Inhibition of either ERK1/2 or mTORC1 did not reduce the TGF-β1-stimulated increase in Nox4 mRNA level but significantly inhibited total Nox4 expression, ROS generation, and apoptosis induced by TGF-β1. Moreover, double knockdown of Smad2 and 3 or only Smad4 completely suppressed TGF-β1-induced ERK1/2-mTORactivation. Our data suggest that TGF-β1 increases translation of Nox4 through the Smad-ERK1/2-mTORC1 axis, which is independent of transcriptional regulation. Activation of this pathway plays a crucial role in ROS generation and mitochondrial dysfunction, leading to podocyte apoptosis. Therefore, inhibition of the ERK1/2-mTORC1 pathway could be a potential therapeutic and preventive target in proteinuric and chronic kidney diseases.
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Affiliation(s)
- Ranjan Das
- From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and
| | - Shanhua Xu
- From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and
| | - Tuyet Thi Nguyen
- From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and
| | - Xianglan Quan
- From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and
| | - Seong-Kyung Choi
- From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and
| | - Soo-Jin Kim
- From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and
| | - Eun Young Lee
- the Department of Internal Medicine, Soonchunhyang University Cheonan Hospital, Cheonan 330-721, Republic of Korea
| | - Seung-Kuy Cha
- From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and
| | - Kyu-Sang Park
- From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and
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Abstract
The mammalian target of rapamycin (mTOR) inhibitors are drugs, primarily used as immunosuppressors that are now frequently used as antineoplastic therapies in various cancers (such as advanced renal cell carcinoma, advanced breast cancer, progressive pancreatic neuroendocrine tumors). They act on mTOR signaling pathway which plays a key role in regulating cell growth as well as lipid and glucose metabolism. Treatment with mTOR inhibitors is associated with a high incidence of hyperglycemia and new-onset diabetes, ranging from 13% to 50% in the clinical trials in which they have been used as anticancer therapies. The rate of severe hyperglycemia is also increased, ranging from 4 to 12% in the main phase III clinical trials. Due to limited human studies, the pathophysiology of mTOR inhibitor-induced hyperglycemia has not yet been totally clarified. However, data from animal studies suggest that the mechanisms responsible for hyperglycemia with mTOR inhibitors are likely due to the combination of impaired insulin secretion and insulin resistance. Due to the high rate of hyperglycemia associated with the use of mTOR inhibitors, a close and personalized follow-up of blood glucose is recommended in all patients.
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Affiliation(s)
- Bruno Vergès
- Endocrinology-Diabetology Department, University-Hospital, and, Medicine University, Dijon, France; INSERM CRI 866, Medicine University, Dijon, France; Faculté de Médecine, Université de Nantes, Nantes, France.
| | - Bertrand Cariou
- INSERM CRI 866, Medicine University, Dijon, France; Clinique d'Endocrinologie, l'institut du thorax, CHU de Nantes, Nantes, France; INSERM, UMR1087, l'institut du thorax, Nantes, France; Faculté de Médecine, Université de Nantes, Nantes, France
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Arous C, Halban PA. The skeleton in the closet: actin cytoskeletal remodeling in β-cell function. Am J Physiol Endocrinol Metab 2015; 309:E611-20. [PMID: 26286869 DOI: 10.1152/ajpendo.00268.2015] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 08/11/2015] [Indexed: 01/13/2023]
Abstract
Over the last few decades, biomedical research has considered not only the function of single cells but also the importance of the physical environment within a whole tissue, including cell-cell and cell-extracellular matrix interactions. Cytoskeleton organization and focal adhesions are crucial sensors for cells that enable them to rapidly communicate with the physical extracellular environment in response to extracellular stimuli, ensuring proper function and adaptation. The involvement of the microtubular-microfilamentous cytoskeleton in secretion mechanisms was proposed almost 50 years ago, since when the evolution of ever more sensitive and sophisticated methods in microscopy and in cell and molecular biology have led us to become aware of the importance of cytoskeleton remodeling for cell shape regulation and its crucial link with signaling pathways leading to β-cell function. Emerging evidence suggests that dysfunction of cytoskeletal components or extracellular matrix modification influences a number of disorders through potential actin cytoskeleton disruption that could be involved in the initiation of multiple cellular functions. Perturbation of β-cell actin cytoskeleton remodeling could arise secondarily to islet inflammation and fibrosis, possibly accounting in part for impaired β-cell function in type 2 diabetes. This review focuses on the role of actin remodeling in insulin secretion mechanisms and its close relationship with focal adhesions and myosin II.
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Affiliation(s)
- Caroline Arous
- Department of Genetic Medicine and Development, University of Geneva Medical Center, Geneva, Switzerland
| | - Philippe A Halban
- Department of Genetic Medicine and Development, University of Geneva Medical Center, Geneva, Switzerland
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Potts MB, McMillan EA, Rosales TI, Kim HS, Ou YH, Toombs JE, Brekken RA, Minden MD, MacMillan JB, White MA. Mode of action and pharmacogenomic biomarkers for exceptional responders to didemnin B. Nat Chem Biol 2015; 11:401-8. [PMID: 25867045 PMCID: PMC4433765 DOI: 10.1038/nchembio.1797] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 03/20/2015] [Indexed: 12/11/2022]
Abstract
Modern cancer treatment employs many effective chemotherapeutic agents originally discovered from natural sources. The cyclic depsipeptide didemnin B has demonstrated impressive anticancer activity in preclinical models. Clinical use has been approved but is limited by sparse patient responses combined with toxicity risk and an unclear mechanism of action. From a broad-scale effort to match antineoplastic natural products to their cellular activities, we found that didemnin B selectively induces rapid and wholesale apoptosis through dual inhibition of PPT1 and EEF1A1. Furthermore, empirical discovery of a small panel of exceptional responders to didemnin B allowed the generation of a regularized regression model to extract a sparse-feature genetic biomarker capable of predicting sensitivity to didemnin B. This may facilitate patient selection in a fashion that could enhance and expand the therapeutic application of didemnin B against neoplastic disease.
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Affiliation(s)
- Malia B. Potts
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Elizabeth A. McMillan
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Tracy I. Rosales
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Hyun Seok Kim
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Yi-Hung Ou
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Jason E. Toombs
- Division of Surgical Oncology, Department of Surgery, Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Rolf A. Brekken
- Division of Surgical Oncology, Department of Surgery, Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Mark D. Minden
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5S 1A8, Canada. Ontario Cancer Institute and Princess Margaret Hospital, University Health Network, Toronto, Ontario M5T 2M9, Canada
| | - John B. MacMillan
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Michael A. White
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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39
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miR-106a* inhibits the proliferation of renal carcinoma cells by targeting IRS-2. Tumour Biol 2015; 36:8389-98. [DOI: 10.1007/s13277-015-3605-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2015] [Accepted: 05/22/2015] [Indexed: 01/31/2023] Open
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Chen L, Li Z, Ahmad N, Liu X. Plk1 phosphorylation of IRS2 prevents premature mitotic exit via AKT inactivation. Biochemistry 2015; 54:2473-80. [PMID: 25830382 PMCID: PMC4950874 DOI: 10.1021/acs.biochem.5b00016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Insulin receptor substrate (IRS) proteins play important roles by acting as a platform in transducing signals from transmembrane receptors upon growth factor stimulation. Although tyrosine phosphorylation on IRS proteins plays critical roles in signal transduction, phosphorylation of IRS proteins on serine/threonine residues is believed to play various regulatory roles in IRS protein function. However, studies of serine/threonine phosphorylation of IRS proteins are very limited, especially for insulin receptor substrate 2 (IRS2), one member of the IRS protein family. In this study, we identify Polo-like kinase 1 (Plk1) as the responsible kinase for phosphorylation of IRS2 on two serine residues, Ser 556 and Ser 1098. Phosphorylation of IRS2 at these two serine residues by Plk1 prevents the activation of the PI3K pathway upon growth factor stimulation by inhibiting the binding between IRS2 and the PI3K pathway components and increasing the level of IRS2 protein degradation. Significantly, we show that IRS2 phosphorylation is cell cycle-regulated and that Plk1 phosphorylation of IRS2 prevents premature mitotic exit via AKT inactivation.
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Affiliation(s)
- Long Chen
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Zhiguo Li
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
| | - Nihal Ahmad
- Department of Dermatology, University of Wisconsin, Madison, WI 53706, USA
| | - Xiaoqi Liu
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
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42
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Oliveira JM, Rebuffat SA, Gasa R, Gomis R. Targeting type 2 diabetes: lessons from a knockout model of insulin receptor substrate 2. Can J Physiol Pharmacol 2014; 92:613-20. [DOI: 10.1139/cjpp-2014-0114] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Insulin receptor substrate 2 (IRS2) is a widely expressed protein that regulates crucial biological processes including glucose metabolism, protein synthesis, and cell survival. IRS2 is part of the insulin – insulin-like growth factor (IGF) signaling pathway and mediates the activation of the phosphotidylinositol 3-kinase (PI3K)–Akt and the Ras–mitogen-activated protein kinase (MAPK) cascades in insulin target tissues and in the pancreas. The best evidence of this is that systemic elimination of the Irs2 in mice (Irs2−/−) recapitulates the pathogenesis of type 2 diabetes (T2D), in that diabetes arises as a consequence of combined insulin resistance and beta-cell failure. Indeed, work using this knockout mouse has confirmed the importance of IRS2 in the control of glucose homeostasis and especially in the survival and function of pancreatic beta-cells. These studies have shown that IRS2 is critically required for beta-cell compensation in conditions of increased insulin demand. Importantly, islets isolated from T2D patients exhibit reduced IRS2 expression, which supports the likely contribution of altered IRS2-dependent signaling to beta-cell failure in human T2D. For all these reasons, the Irs2−/− mouse has been and will be essential for elucidating the inter-relationship between beta-cell function and insulin resistance, as well as to delineate therapeutic strategies to protect beta-cells during T2D progression.
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Affiliation(s)
- Joana Moitinho Oliveira
- Diabetes and Obesity Research Laboratory, Institut d’Investigations Biomediques August Pi i Sunyer, Centre Esther Koplowitz, C/Rosselló, 149-153 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Sandra A. Rebuffat
- Diabetes and Obesity Research Laboratory, Institut d’Investigations Biomediques August Pi i Sunyer, Centre Esther Koplowitz, C/Rosselló, 149-153 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Rosa Gasa
- Diabetes and Obesity Research Laboratory, Institut d’Investigations Biomediques August Pi i Sunyer, Centre Esther Koplowitz, C/Rosselló, 149-153 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Ramon Gomis
- Diabetes and Obesity Research Laboratory, Institut d’Investigations Biomediques August Pi i Sunyer, Centre Esther Koplowitz, C/Rosselló, 149-153 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- University of Barcelona, Hospital Clínic, Barcelona, Spain
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43
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Huang Y, Chang Y. Regulation of pancreatic islet beta-cell mass by growth factor and hormone signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 121:321-49. [PMID: 24373242 DOI: 10.1016/b978-0-12-800101-1.00010-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Dysfunction and destruction of pancreatic islet beta cells is a hallmark of diabetes. Better understanding of cellular signals in beta cells will allow development of therapeutic strategies for diabetes, such as preservation and expansion of beta-cell mass and improvement of beta-cell function. During the past several decades, the number of studies analyzing the molecular mechanisms, including growth factor/hormone signaling pathways that impact islet beta-cell mass and function, has increased exponentially. Notably, somatolactogenic hormones including growth hormone (GH), prolactin (PRL), and insulin-like growth factor-1 (IGF-1) and their receptors (GHR, PRLR, and IGF-1R) are critically involved in beta-cell growth, survival, differentiation, and insulin secretion. In this chapter, we focus more narrowly on GH, PRL, and IGF-1 signaling, and GH-IGF-1 cross talk. We also discuss how these signaling aspects contribute to the regulation of beta-cell proliferation and apoptosis. In particular, our novel findings of GH-induced formation of GHR-JAK2-IGF-1R protein complex and synergistic effects of GH and IGF-1 on beta-cell signaling, proliferation, and antiapoptosis lead to a new concept that IGF-1R may serve as a proximal component of GH/GHR signaling.
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Affiliation(s)
- Yao Huang
- Department of Obstetrics and Gynecology, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Yongchang Chang
- Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
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TOR-centric view on insulin resistance and diabetic complications: perspective for endocrinologists and gerontologists. Cell Death Dis 2013; 4:e964. [PMID: 24336084 PMCID: PMC3877573 DOI: 10.1038/cddis.2013.506] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 11/11/2013] [Accepted: 11/13/2013] [Indexed: 01/06/2023]
Abstract
This article is addressed to endocrinologists treating patients with diabetic complications as well as to basic scientists studying an elusive link between diseases and aging. It answers some challenging questions. What is the link between insulin resistance (IR), cellular aging and diseases? Why complications such as retinopathy may paradoxically precede the onset of type II diabetes. Why intensive insulin therapy may initially worsen retinopathy. How nutrient- and insulin-sensing mammalian target of rapamycin (mTOR) pathway can drive insulin resistance and diabetic complications. And how rapamycin, at rational doses and schedules, may prevent IR, retinopathy, nephropathy and beta-cell failure, without causing side effects.
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Abstract
Recent discoveries suggest that aging is neither driven by accumulation of molecular damage of any cause, nor by random damage of any kind. Some predictions of a new theory, quasi-programmed hyperfunction, have already been confirmed and a clinically-available drug slows aging and delays diseases in animals. The relationship between diseases and aging becomes easily apparent. Yet, the essence of aging turns out to be so startling that the theory cannot be instantly accepted and any possible arguments are raised for its disposal. I discuss that these arguments actually support a new theory. Are any questions remaining? And might accumulation of molecular damage still play a peculiar role in aging?
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Affiliation(s)
- Mikhail V Blagosklonny
- Department of Cell Stress Biology, Roswell Park Cancer Institute, BLSC, L3-312, Elm and Carlton Streets, Buffalo, NY 14263, USA.
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46
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Abstract
In recent years there has been a growing interest in the possibility of a direct autocrine effect of insulin on the pancreatic β-cell. Indeed, there have been numerous intriguing articles and several eloquent reviews written on the subject (1-3); however, the concept is still controversial. Although many in vitro experiments, a few transgenic mouse studies, and some human investigations would be supportive of the notion, there exist different insights, other studies, and circumstantial evidence that question the concept. Therefore, the idea of autocrine action of insulin remains a conundrum. Here we outline a series of thoughts, insights, and alternative interpretations of the available experimental evidence. We ask, how convincing are these, and what are the confusing issues? We agree that there is a clear contribution of certain downstream elements in the insulin signaling pathway for β-cell function and survival, but the question of whether insulin itself is actually the physiologically relevant ligand that triggers this signal transduction remains unsettled.
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Affiliation(s)
- Christopher J Rhodes
- Kovler Diabetes Center, Department of Medicine, University of Chicago, Chicago, Illinois, USA.
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Aly H, Rohatgi N, Marshall CA, Grossenheider TC, Miyoshi H, Stappenbeck TS, Matkovich SJ, McDaniel ML. A novel strategy to increase the proliferative potential of adult human β-cells while maintaining their differentiated phenotype. PLoS One 2013; 8:e66131. [PMID: 23776620 PMCID: PMC3680388 DOI: 10.1371/journal.pone.0066131] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 05/01/2013] [Indexed: 12/13/2022] Open
Abstract
Our previous studies demonstrated that Wnt/GSK-3/β-catenin and mTOR signaling are necessary to stimulate proliferative processes in adult human β-cells. Direct inhibition of GSK-3, that engages Wnt signaling downstream of the Wnt receptor, increases β-catenin nuclear translocation and β-cell proliferation but results in lower insulin content. Our current goal was to engage canonical and non-canonical Wnt signaling at the receptor level to significantly increase human β-cell proliferation while maintaining a β-cell phenotype in intact islets. We adopted a system that utilized conditioned medium from L cells that expressed Wnt3a, R-spondin-3 and Noggin (L-WRN conditioned medium). In addition we used a ROCK inhibitor (Y-27632) and SB-431542 (that results in RhoA inhibition) in these cultures. Treatment of intact human islets with L-WRN conditioned medium plus inhibitors significantly increased DNA synthesis ∼6 fold in a rapamycin-sensitive manner. Moreover, this treatment strikingly increased human β-cell proliferation ∼20 fold above glucose alone. Only the combination of L-WRN conditioned medium with RhoA/ROCK inhibitors resulted in substantial proliferation. Transcriptome-wide gene expression profiling demonstrated that L-WRN medium provoked robust changes in several signaling families, including enhanced β-catenin-mediated and β-cell-specific gene expression. This treatment also increased expression of Nr4a2 and Irs2 and resulted in phosphorylation of Akt. Importantly, glucose-stimulated insulin secretion and content were not downregulated by L-WRN medium treatment. Our data demonstrate that engaging Wnt signaling at the receptor level by this method leads to necessary crosstalk between multiple signaling pathways including activation of Akt, mTOR, Wnt/β-catenin, PKA/CREB, and inhibition of RhoA/ROCK that substantially increase human β-cell proliferation while maintaining the β-cell phenotype.
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Affiliation(s)
- Haytham Aly
- Department of Pathology and Immunology Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Nidhi Rohatgi
- Department of Pathology and Immunology Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Connie A. Marshall
- Department of Pathology and Immunology Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Tiffani C. Grossenheider
- Center for Pharmacogenomics, Department of Medicine, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Hiroyuki Miyoshi
- Department of Pathology and Immunology Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Thaddeus S. Stappenbeck
- Department of Pathology and Immunology Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Scot J. Matkovich
- Center for Pharmacogenomics, Department of Medicine, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Michael L. McDaniel
- Department of Pathology and Immunology Washington University in St. Louis, St. Louis, Missouri, United States of America
- * E-mail:
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Rohatgi N, Aly H, Marshall CA, McDonald WG, Kletzien RF, Colca JR, McDaniel ML. Novel insulin sensitizer modulates nutrient sensing pathways and maintains β-cell phenotype in human islets. PLoS One 2013; 8:e62012. [PMID: 23650507 PMCID: PMC3641131 DOI: 10.1371/journal.pone.0062012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 03/17/2013] [Indexed: 02/04/2023] Open
Abstract
Major bottlenecks in the expansion of human β-cell mass are limited proliferation, loss of β-cell phenotype, and increased apoptosis. In our previous studies, activation of Wnt and mTOR signaling significantly enhanced human β-cell proliferation. However, isolated human islets displayed insulin signaling pathway resistance, due in part to chronic activation of mTOR/S6K1 signaling that results in negative feedback of the insulin signaling pathway and a loss of Akt phosphorylation and insulin content. We evaluated the effects of a new generation insulin sensitizer, MSDC-0160, on restoring insulin/IGF-1 sensitivity and insulin content in human β-cells. This novel TZD has low affinity for binding and activation of PPARγ and has insulin-sensitizing effects in mouse models of diabetes and ability to lower glucose in Phase 2 clinical trials. MSDC-0160 treatment of human islets increased AMPK activity and reduced mTOR activity. This was associated with the restoration of IGF-1-induced phosphorylation of Akt, GSK-3, and increased protein expression of Pdx1. Furthermore, MSDC-0160 in combination with IGF-1 and 8 mM glucose increased β-cell specific gene expression of insulin, pdx1, nkx6.1, and nkx2.2, and maintained insulin content without altering glucose-stimulated insulin secretion. Human islets were unable to simultaneously promote DNA synthesis and maintain the β-cell phenotype. Lithium-induced GSK-3 inhibition that promotes DNA synthesis blocked the ability of MSDC-0160 to maintain the β-cell phenotype. Conversely, MSDC-0160 prevented an increase in DNA synthesis by blocking β-catenin nuclear translocation. Due to the counteracting pathways involved in these processes, we employed a sequential ex vivo strategy to first induce human islet DNA synthesis, followed by MSDC-0160 to promote the β-cell phenotype and insulin content. This new generation PPARγ sparing insulin sensitizer may provide an initial tool for relieving inherent human islet insulin signaling pathway resistance that is necessary to preserve the β-cell phenotype during β-cell expansion for the treatment of diabetes.
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Affiliation(s)
- Nidhi Rohatgi
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Haytham Aly
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Connie A. Marshall
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - William G. McDonald
- Metabolic Solutions Development Company, Kalamazoo, Michigan, United States of America
| | - Rolf F. Kletzien
- Metabolic Solutions Development Company, Kalamazoo, Michigan, United States of America
| | - Jerry R. Colca
- Metabolic Solutions Development Company, Kalamazoo, Michigan, United States of America
| | - Michael L. McDaniel
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, Missouri, United States of America
- * E-mail:
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Bachar-Wikstrom E, Wikstrom JD, Ariav Y, Tirosh B, Kaiser N, Cerasi E, Leibowitz G. Stimulation of autophagy improves endoplasmic reticulum stress-induced diabetes. Diabetes 2013; 62:1227-37. [PMID: 23274896 PMCID: PMC3609555 DOI: 10.2337/db12-1474] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Accumulation of misfolded proinsulin in the β-cell leads to dysfunction induced by endoplasmic reticulum (ER) stress, with diabetes as a consequence. Autophagy helps cellular adaptation to stress via clearance of misfolded proteins and damaged organelles. We studied the effects of proinsulin misfolding on autophagy and the impact of stimulating autophagy on diabetes progression in Akita mice, which carry a mutation in proinsulin, leading to its severe misfolding. Treatment of female diabetic Akita mice with rapamycin improved diabetes, increased pancreatic insulin content, and prevented β-cell apoptosis. In vitro, autophagic flux was increased in Akita β-cells. Treatment with rapamycin further stimulated autophagy, evidenced by increased autophagosome formation and enhancement of autophagosome-lysosome fusion. This was associated with attenuation of cellular stress and apoptosis. The mammalian target of rapamycin (mTOR) kinase inhibitor Torin1 mimicked the rapamycin effects on autophagy and stress, indicating that the beneficial effects of rapamycin are indeed mediated via inhibition of mTOR. Finally, inhibition of autophagy exacerbated stress and abolished the anti-ER stress effects of rapamycin. In conclusion, rapamycin reduces ER stress induced by accumulation of misfolded proinsulin, thereby improving diabetes and preventing β-cell apoptosis. The beneficial effects of rapamycin in this context strictly depend on autophagy; therefore, stimulating autophagy may become a therapeutic approach for diabetes.
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Affiliation(s)
- Etty Bachar-Wikstrom
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Jakob D. Wikstrom
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Yafa Ariav
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Boaz Tirosh
- School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nurit Kaiser
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Erol Cerasi
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Gil Leibowitz
- Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
- Corresponding author: Gil Leibowitz,
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The role of the cullin-5 e3 ubiquitin ligase in the regulation of insulin receptor substrate-1. Biochem Res Int 2013; 2012:282648. [PMID: 23304509 PMCID: PMC3523409 DOI: 10.1155/2012/282648] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 11/02/2012] [Accepted: 11/11/2012] [Indexed: 11/17/2022] Open
Abstract
Background. SOCS proteins are known to negatively regulate insulin signaling by inhibiting insulin receptor substrate-1 (IRS1). IRS1 has been reported to be a substrate for ubiquitin-dependent proteasomal degradation. Given that SOCS proteins can function as substrate receptor subunits of Cullin-5 E3 ubiquitin ligases, we examined whether Cullin-5 dependent ubiquitination is involved in the regulation of basal IRS1 protein stability and signal-induced IRS1 degradation. Findings. Our results indicate that basal IRS1 stability varies between cell types. However, the Cullin-5 E3 ligase does not play a major role in mediating IRS1 ubiquitination under basal conditions. Protein kinase C activation triggered pronounced IRS1 destabilization. However, this effect was also independent of the function of Cullin-5 E3 ubiquitin ligases. Conclusions. In conclusion, SOCS proteins do not exert a negative regulatory effect on IRS1 by functioning as substrate receptors for Cullin-5-based E3 ubiquitin ligases both under basal conditions and when IRS1 degradation is induced by protein kinase C activation.
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