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Quantitative, in situ visualization of intracellular insulin vesicles in pancreatic beta cells. Proc Natl Acad Sci U S A 2022; 119:e2202695119. [PMID: 35921440 PMCID: PMC9371705 DOI: 10.1073/pnas.2202695119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Characterizing relationships between Zn2+, insulin, and insulin vesicles is of vital importance to the study of pancreatic beta cells. However, the precise content of Zn2+ and the specific location of insulin inside insulin vesicles are not clear, which hinders a thorough understanding of the insulin secretion process and diseases caused by blood sugar dysregulation. Here, we demonstrated the colocalization of Zn2+ and insulin in both single extracellular insulin vesicles and pancreatic beta cells by using an X-ray scanning coherent diffraction imaging (ptychography) technique. We also analyzed the elemental Zn2+ and Ca2+ contents of insulin vesicles using electron microscopy and energy dispersive spectroscopy (EDS) mapping. We found that the presence of Zn2+ is an important characteristic that can be used to distinguish insulin vesicles from other types of vesicles in pancreatic beta cells and that the content of Zn2+ is proportional to the size of insulin vesicles. By using dual-energy contrast X-ray microscopy and scanning transmission X-ray microscopy (STXM) image stacks, we observed that insulin accumulates in the off-center position of extracellular insulin vesicles. Furthermore, the spatial distribution of insulin vesicles and their colocalization with other organelles inside pancreatic beta cells were demonstrated using three-dimensional (3D) imaging by combining X-ray ptychography and an equally sloped tomography (EST) algorithm. This study describes a powerful method to univocally describe the location and quantitative analysis of intracellular insulin, which will be of great significance to the study of diabetes and other blood sugar diseases.
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Kumar AV, Kang T, Thakurta TG, Ng C, Rogers AN, Larsen MR, Lapierre LR. Exportin 1 modulates life span by regulating nucleolar dynamics via the autophagy protein LGG-1/GABARAP. SCIENCE ADVANCES 2022; 8:eabj1604. [PMID: 35363528 PMCID: PMC10938577 DOI: 10.1126/sciadv.abj1604] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 02/08/2022] [Indexed: 06/14/2023]
Abstract
Altered nucleolar and ribosomal dynamics are key hallmarks of aging, but their regulation remains unclear. Building on the knowledge that the conserved nuclear export receptor Exportin 1 (XPO-1/XPO1) modulates proteostasis and life span, we systematically analyzed the impact of nuclear export on protein metabolism. Using transcriptomic and subcellular proteomic analyses in nematodes, we demonstrate that XPO-1 modulates the nucleocytoplasmic distribution of key proteins involved in nucleolar dynamics and ribosome function, including fibrillarin (FIB-1/FBL) and RPL-11 (RPL11). Silencing xpo-1 led to marked reduction in global translation, which was accompanied by decreased nucleolar size and lower fibrillarin levels. A targeted screen of known proteostatic mediators revealed that the autophagy protein LGG-1/GABARAP modulates nucleolar size by regulating RPL-11 levels, linking specific protein degradation to ribosome metabolism. Together, our study reveals that nucleolar size and life span are regulated by LGG-1/GABARAP via ribosome protein surveillance.
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Affiliation(s)
- Anita V. Kumar
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, 185 Meeting St., Providence, RI 02912, USA
| | - Taewook Kang
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Tara G. Thakurta
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, 185 Meeting St., Providence, RI 02912, USA
| | - Celeste Ng
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, 185 Meeting St., Providence, RI 02912, USA
| | - Aric N. Rogers
- MDI Biological Laboratory, 159 Old Bar Harbor Rd., Salisbury Cove, ME 04672, USA
| | - Martin R. Larsen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Louis R. Lapierre
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, 185 Meeting St., Providence, RI 02912, USA
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Divalent Metal Transporter 1 Knock-Down Modulates IL-1β Mediated Pancreatic Beta-Cell Pro-Apoptotic Signaling Pathways through the Autophagic Machinery. Int J Mol Sci 2021; 22:ijms22158013. [PMID: 34360779 PMCID: PMC8348373 DOI: 10.3390/ijms22158013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 07/23/2021] [Accepted: 07/24/2021] [Indexed: 12/21/2022] Open
Abstract
Pro-inflammatory cytokines promote cellular iron-import through enhanced divalent metal transporter-1 (DMT1) expression in pancreatic β-cells, consequently cell death. Inhibition of β-cell iron-import by DMT1 silencing protects against apoptosis in animal models of diabetes. However, how alterations of signaling networks contribute to the protective action of DMT1 knock-down is unknown. Here, we performed phosphoproteomics using our sequential enrichment strategy of mRNA, protein, and phosphopeptides, which enabled us to explore the concurrent molecular events in the same set of wildtype and DMT1-silenced β-cells during IL-1β exposure. Our findings reveal new phosphosites in the IL-1β-induced proteins that are clearly reverted by DMT1 silencing towards their steady-state levels. We validated the levels of five novel phosphosites of the potential protective proteins using parallel reaction monitoring. We also confirmed the inactivation of autophagic flux that may be relevant for cell survival induced by DMT1 silencing during IL-1β exposure. Additionally, the potential protective proteins induced by DMT1 silencing were related to insulin secretion that may lead to improving β-cell functions upon exposure to IL-1β. This global profiling has shed light on the signal transduction pathways driving the protection against inflammation-induced cell death in β-cells after DMT1 silencing.
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Kang T, Boland BB, Jensen P, Alarcon C, Nawrocki A, Grimsby JS, Rhodes CJ, Larsen MR. Characterization of Signaling Pathways Associated with Pancreatic β-cell Adaptive Flexibility in Compensation of Obesity-linked Diabetes in db/db Mice. Mol Cell Proteomics 2020; 19:971-993. [PMID: 32265294 PMCID: PMC7261816 DOI: 10.1074/mcp.ra119.001882] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 03/03/2020] [Indexed: 12/20/2022] Open
Abstract
The onset of obesity-linked type 2 diabetes (T2D) is marked by an eventual failure in pancreatic β-cell function and mass that is no longer able to compensate for the inherent insulin resistance and increased metabolic load intrinsic to obesity. However, in a commonly used model of T2D, the db/db mouse, β-cells have an inbuilt adaptive flexibility enabling them to effectively adjust insulin production rates relative to the metabolic demand. Pancreatic β-cells from these animals have markedly reduced intracellular insulin stores, yet high rates of (pro)insulin secretion, together with a substantial increase in proinsulin biosynthesis highlighted by expanded rough endoplasmic reticulum and Golgi apparatus. However, when the metabolic overload and/or hyperglycemia is normalized, β-cells from db/db mice quickly restore their insulin stores and normalize secretory function. This demonstrates the β-cell's adaptive flexibility and indicates that therapeutic approaches applied to encourage β-cell rest are capable of restoring endogenous β-cell function. However, mechanisms that regulate β-cell adaptive flexibility are essentially unknown. To gain deeper mechanistic insight into the molecular events underlying β-cell adaptive flexibility in db/db β-cells, we conducted a combined proteomic and post-translational modification specific proteomic (PTMomics) approach on islets from db/db mice and wild-type controls (WT) with or without prior exposure to normal glucose levels. We identified differential modifications of proteins involved in redox homeostasis, protein refolding, K48-linked deubiquitination, mRNA/protein export, focal adhesion, ERK1/2 signaling, and renin-angiotensin-aldosterone signaling, as well as sialyltransferase activity, associated with β-cell adaptive flexibility. These proteins are all related to proinsulin biosynthesis and processing, maturation of insulin secretory granules, and vesicular trafficking-core pathways involved in the adaptation of insulin production to meet metabolic demand. Collectively, this study outlines a novel and comprehensive global PTMome signaling map that highlights important molecular mechanisms related to the adaptive flexibility of β-cell function, providing improved insight into disease pathogenesis of T2D.
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Affiliation(s)
- Taewook Kang
- Protein research group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark; The Danish Diabetes Academy, Odense, Denmark
| | - Brandon B Boland
- The Kovler Diabetes Center, Department of Medicine Section of Endocrinology, Diabetes & Metabolism, University of Chicago, Chicago, Illinois 60637; Cardiovascular, Renal and Metabolic Disease, BioPharmaceuticals Research and Development, AstraZeneca Gaithersburg, Maryland 20878
| | - Pia Jensen
- Protein research group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Cristina Alarcon
- The Kovler Diabetes Center, Department of Medicine Section of Endocrinology, Diabetes & Metabolism, University of Chicago, Chicago, Illinois 60637
| | - Arkadiusz Nawrocki
- Protein research group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Joseph S Grimsby
- Cardiovascular, Renal and Metabolic Disease, BioPharmaceuticals Research and Development, AstraZeneca Gaithersburg, Maryland 20878
| | - Christopher J Rhodes
- The Kovler Diabetes Center, Department of Medicine Section of Endocrinology, Diabetes & Metabolism, University of Chicago, Chicago, Illinois 60637; Cardiovascular, Renal and Metabolic Disease, BioPharmaceuticals Research and Development, AstraZeneca Gaithersburg, Maryland 20878
| | - Martin R Larsen
- Protein research group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
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Santo-Domingo J, Galindo AN, Cominetti O, De Marchi U, Cutillas P, Dayon L, Wiederkehr A. Glucose-dependent phosphorylation signaling pathways and crosstalk to mitochondrial respiration in insulin secreting cells. Cell Commun Signal 2019; 17:14. [PMID: 30786936 PMCID: PMC6381748 DOI: 10.1186/s12964-019-0326-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 02/08/2019] [Indexed: 01/13/2023] Open
Abstract
Background Glucose is the main secretagogue of pancreatic beta-cells. Uptake and metabolism of the nutrient stimulates the beta-cell to release the blood glucose lowering hormone insulin. This metabolic activation is associated with a pronounced increase in mitochondrial respiration. Glucose stimulation also initiates a number of signal transduction pathways for the coordinated regulation of multiple biological processes required for insulin secretion. Methods Shotgun proteomics including TiO2 enrichment of phosphorylated peptides followed by liquid chromatography tandem mass spectrometry on lysates from glucose-stimulated INS-1E cells was used to identify glucose regulated phosphorylated proteins and signal transduction pathways. Kinase substrate enrichment analysis (KSEA) was applied to identify key regulated kinases and phosphatases. Glucose-induced oxygen consumption was measured using a XF96 Seahorse instrument to reveal cross talk between glucose-regulated kinases and mitochondrial activation. Results Our kinetic analysis of substrate phosphorylation reveal the molecular mechanism leading to rapid activation of insulin biogenesis, vesicle trafficking, insulin granule exocytosis and cytoskeleton remodeling. Kinase-substrate enrichment identified upstream kinases and phosphatases and time-dependent activity changes during glucose stimulation. Activity trajectories of well-known glucose-regulated kinases and phosphatases are described. In addition, we predict activity changes in a number of kinases including NUAK1, not or only poorly studied in the context of the pancreatic beta-cell. Furthermore, we pharmacologically tested whether signaling pathways predicted by kinase-substrate enrichment analysis affected glucose-dependent acceleration of mitochondrial respiration. We find that phosphoinositide 3-kinase, Ca2+/calmodulin dependent protein kinase and protein kinase C contribute to short-term regulation of energy metabolism. Conclusions Our results provide a global view into the regulation of kinases and phosphatases in insulin secreting cells and suggest cross talk between glucose-induced signal transduction and mitochondrial activation. Electronic supplementary material The online version of this article (10.1186/s12964-019-0326-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jaime Santo-Domingo
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland.
| | - Antonio Núñez Galindo
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Ornella Cominetti
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Umberto De Marchi
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Pedro Cutillas
- Analytical Signalling Group, Centre for Cell Signalling, Queen Mary University of London, London, UK
| | - Loïc Dayon
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Andreas Wiederkehr
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
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Vakhrushev IV, Novikova SE, Tsvetkova AV, Pyatnitskiy MA, Yarygin KN. [Comparative proteomic profiling of nuclear and cytosolic fractions from cell lines of different origin]. BIOMEDIT︠S︡INSKAI︠A︡ KHIMII︠A︡ 2018; 64:233-240. [PMID: 29964258 DOI: 10.18097/pbmc20186403233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Proteomic analysis of the nuclear fraction is of great importance, since many cellular processes are initiated in the nucleus. Refinement and choice of experimental procedures for cell lysate fractionation and parameters for mass spectrometric detection and data processing continue to be of current interest. The mass spectrometry analysis presented here was tested on human cell lines derived from different tissues: HL-60 (peripheral blood); HepG2 (liver); EA.hy926 (vascular endothelium). High reproducibility of results and their consistency with biological properties of the objects under study were demonstrated. The use of cells of different types made it possible to reveal a set of 16 proteins whose LFQ-values allow for the discrimination between proteome fractions regardless of cell origin. Also, a set of 16 proteins is suggested which are associated with individual characteristics of cell lines regardless of cell fraction. These protein panels can serve as parameters to verify the proteomic analysis done was of sufficient quality, in particular as indicators of successful fractionation of cell or tissue lysate.
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Affiliation(s)
| | - S E Novikova
- Institute of Biomedical Chemistry, Moscow, Russia
| | | | - M A Pyatnitskiy
- Institute of Biomedical Chemistry, Moscow, Russia; National Research University Higher School of Economics, Moscow, Russia
| | - K N Yarygin
- Institute of Biomedical Chemistry, Moscow, Russia
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