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Woolley L, Burbidge A, Vermant J, Christakopoulos F. A microrheological examination of insulin-secreting β-cells in healthy and diabetic-like conditions. SOFT MATTER 2024; 20:3464-3472. [PMID: 38573072 DOI: 10.1039/d3sm01141k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
Pancreatic β-cells regulate glucose homeostasis through glucose-stimulated insulin secretion, which is hindered in type-2 diabetes. Transport of the insulin vesicles is expected to be affected by changes in the viscoelastic and transport properties of the cytoplasm. These are evaluated in situ through particle-tracking measurements using a rat insulinoma β-cell line. The use of inert probes assists in decoupling the material properties of the cytoplasm from the active transport through cellular processes. The effect of glucose-stimulated insulin secretion is examined, and the subsequent remodeling of the cytoskeleton, at constant effects of cell activity, is shown to result in reduced mobility of the tracer particles. Induction of diabetic-like conditions is identified to alter the mean-squared displacement of the passive particles in the cytoplasm and diminish its reaction to glucose stimulation.
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Affiliation(s)
- Lukas Woolley
- Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich, Switzerland.
| | - Adam Burbidge
- Nestlé Research, Route de Jorat 57, vers-chez-les Blanc, 1000 Lausanne, Switzerland
| | - Jan Vermant
- Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich, Switzerland.
| | - Fotis Christakopoulos
- Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich, Switzerland.
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2
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Sohn P, McLaughlin MR, Krishnan P, Wu W, Slak Rupnik M, Takasu A, Senda T, Lee CC, Kono T, Evans-Molina C. Stromal Interaction Molecule 1 Maintains β-Cell Identity and Function in Female Mice Through Preservation of G-Protein-Coupled Estrogen Receptor 1 Signaling. Diabetes 2023; 72:1433-1445. [PMID: 37478155 PMCID: PMC10545557 DOI: 10.2337/db22-0988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 07/07/2023] [Indexed: 07/23/2023]
Abstract
Altered endoplasmic reticulum (ER) Ca2+ signaling has been linked with β-cell dysfunction and diabetes development. Store-operated Ca2+ entry replenishes ER Ca2+ through reversible gating of plasma membrane Ca2+ channels by the ER Ca2+ sensor, stromal interaction molecule 1 (STIM1). For characterization of the in vivo impact of STIM1 loss, mice with β-cell-specific STIM1 deletion (STIM1Δβ mice) were generated and challenged with high-fat diet. Interestingly, β-cell dysfunction was observed in female, but not male, mice. Female STIM1Δβ mice displayed reductions in β-cell mass, a concomitant increase in α-cell mass, and reduced expression of markers of β-cell maturity, including MafA and UCN3. Consistent with these findings, STIM1 expression was inversely correlated with HbA1c levels in islets from female, but not male, human organ donors. Mechanistic assays demonstrated that the sexually dimorphic phenotype observed in STIM1Δβ mice was due, in part, to loss of signaling through the noncanonical 17-β estradiol receptor (GPER1), as GPER1 knockdown and inhibition led to a similar loss of expression of β-cell maturity genes in INS-1 cells. Together, these data suggest that STIM1 orchestrates pancreatic β-cell function and identity through GPER1-mediated estradiol signaling. ARTICLE HIGHLIGHTS Store-operated Ca2+ entry replenishes endoplasmic reticulum (ER) Ca2+ through reversible gating of plasma membrane Ca2+ channels by the ER Ca2+ sensor, stromal interaction molecule 1 (STIM1). β-Cell-specific deletion of STIM1 results in a sexually dimorphic phenotype, with β-cell dysfunction and loss of identity in female but not male mice. Expression of the noncanonical 17-β estradiol receptor (GPER1) is decreased in islets of female STIM1Δβ mice, and modulation of GPER1 levels leads to alterations in expression of β-cell maturity genes in INS-1 cells.
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Affiliation(s)
- Paul Sohn
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, IN
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, IN
- Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN
| | - Madeline R. McLaughlin
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN
| | - Preethi Krishnan
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, IN
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN
- Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, Canada
| | - Wenting Wu
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, IN
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN
| | - Marjan Slak Rupnik
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
- Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Akira Takasu
- Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Ibaraki, Japan
| | - Toshiya Senda
- Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Ibaraki, Japan
| | - Chih-Chun Lee
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, IN
- Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN
| | - Tatsuyoshi Kono
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, IN
- Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN
- Richard L. Roudebush Veterans' Administration Medical Center, Indianapolis, IN
| | - Carmella Evans-Molina
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, IN
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, IN
- Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN
- Richard L. Roudebush Veterans' Administration Medical Center, Indianapolis, IN
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN
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3
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Yadav GP, Wang H, Ouwendijk J, Cross S, Wang Q, Qin F, Verkade P, Zhu MX, Jiang QX. Chromogranin B (CHGB) is dimorphic and responsible for dominant anion channels delivered to cell surface via regulated secretion. Front Mol Neurosci 2023; 16:1205516. [PMID: 37435575 PMCID: PMC10330821 DOI: 10.3389/fnmol.2023.1205516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 05/26/2023] [Indexed: 07/13/2023] Open
Abstract
Regulated secretion is conserved in all eukaryotes. In vertebrates granin family proteins function in all key steps of regulated secretion. Phase separation and amyloid-based storage of proteins and small molecules in secretory granules require ion homeostasis to maintain their steady states, and thus need ion conductances in granule membranes. But granular ion channels are still elusive. Here we show that granule exocytosis in neuroendocrine cells delivers to cell surface dominant anion channels, to which chromogranin B (CHGB) is critical. Biochemical fractionation shows that native CHGB distributes nearly equally in soluble and membrane-bound forms, and both reconstitute highly selective anion channels in membrane. Confocal imaging resolves granular membrane components including proton pumps and CHGB in puncta on the cell surface after stimulated exocytosis. High pressure freezing immuno-EM reveals a major fraction of CHGB at granule membranes in rat pancreatic β-cells. A cryo-EM structure of bCHGB dimer of a nominal 3.5 Å resolution delineates a central pore with end openings, physically sufficient for membrane-spanning and large single channel conductance. Together our data support that CHGB-containing (CHGB+) channels are characteristic of regulated secretion, and function in granule ion homeostasis near the plasma membrane or possibly in other intracellular processes.
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Affiliation(s)
- Gaya P. Yadav
- Departments of Microbiology and Cell Science and of Medicinal Chemistry, University of Florida, Gainesville, FL, United States
- Departments of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, United States
- Laboratory of Molecular Physiology and Biophysics, Hauptman-Woodward Medical Research Institute, Buffalo, NY, United States
| | - Haiyuan Wang
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Joke Ouwendijk
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Stephen Cross
- Wolfson Bioimaging facility, University of Bristol, Bristol, United Kingdom
| | - Qiaochu Wang
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Feng Qin
- Departments of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, United States
| | - Paul Verkade
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Michael X. Zhu
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Qiu-Xing Jiang
- Departments of Microbiology and Cell Science and of Medicinal Chemistry, University of Florida, Gainesville, FL, United States
- Departments of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, United States
- Laboratory of Molecular Physiology and Biophysics, Hauptman-Woodward Medical Research Institute, Buffalo, NY, United States
- Cryo-EM Center, Laoshan Laboratory, Qingdao, Shandong, China
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4
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Quijano JC, Wedeken L, Ortiz JA, Zook HN, LeBon JM, Luo A, Rawson J, Tremblay JR, Mares JM, Lopez K, Chen MH, Jou K, Mendez-Dorantes C, Al-Abdullah IH, Thurmond DC, Kandeel F, Riggs AD, Ku HT. Methylcellulose colony assay and single-cell micro-manipulation reveal progenitor-like cells in adult human pancreatic ducts. Stem Cell Reports 2023; 18:618-635. [PMID: 36868230 PMCID: PMC10031308 DOI: 10.1016/j.stemcr.2023.02.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 01/31/2023] [Accepted: 02/01/2023] [Indexed: 03/05/2023] Open
Abstract
Progenitor cells capable of self-renewal and differentiation in the adult human pancreas are an under-explored resource for regenerative medicine. Using micro-manipulation and three-dimensional colony assays we identify cells within the adult human exocrine pancreas that resemble progenitor cells. Exocrine tissues were dissociated into single cells and plated into a colony assay containing methylcellulose and 5% Matrigel. A subpopulation of ductal cells formed colonies containing differentiated ductal, acinar, and endocrine lineage cells, and expanded up to 300-fold with a ROCK inhibitor. When transplanted into diabetic mice, colonies pre-treated with a NOTCH inhibitor gave rise to insulin-expressing cells. Both colonies and primary human ducts contained cells that simultaneously express progenitor transcription factors SOX9, NKX6.1, and PDX1. In addition, in silico analysis identified progenitor-like cells within ductal clusters in a single-cell RNA sequencing dataset. Therefore, progenitor-like cells capable of self-renewal and tri-lineage differentiation either pre-exist in the adult human exocrine pancreas, or readily adapt in culture.
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Affiliation(s)
- Janine C Quijano
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA.
| | - Lena Wedeken
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Jose A Ortiz
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA; Irell and Manella Graduate School of Biological Sciences, City of Hope, Duarte, CA 91010, USA
| | - Heather N Zook
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA; Irell and Manella Graduate School of Biological Sciences, City of Hope, Duarte, CA 91010, USA
| | - Jeanne M LeBon
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Angela Luo
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Jeffrey Rawson
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Jacob R Tremblay
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Jacob M Mares
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Kassandra Lopez
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Min-Hsuan Chen
- Integrative Genomics Core, City of Hope, Duarte, CA 91010, USA
| | - Kevin Jou
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Carlos Mendez-Dorantes
- Irell and Manella Graduate School of Biological Sciences, City of Hope, Duarte, CA 91010, USA
| | - Ismail H Al-Abdullah
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Debbie C Thurmond
- Department of Molecular & Cellular Endocrinology, City of Hope, Duarte, CA 91010, USA
| | - Fouad Kandeel
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA; Department of Clinical Diabetes, Endocrinology & Metabolism, City of Hope, Duarte, CA 91010, USA
| | - Arthur D Riggs
- Department of Diabetes & Drug Discovery, City of Hope, Duarte, CA 91010, USA
| | - Hsun Teresa Ku
- Department of Translational Research & Cellular Therapeutics, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA; Irell and Manella Graduate School of Biological Sciences, City of Hope, Duarte, CA 91010, USA
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5
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Loconte V, Chen J, Vanslembrouck B, Ekman AA, McDermott G, Le Gros MA, Larabell CA. Soft X-ray tomograms provide a structural basis for whole-cell modeling. FASEB J 2023; 37:e22681. [PMID: 36519968 PMCID: PMC10107707 DOI: 10.1096/fj.202200253r] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 11/13/2022] [Accepted: 11/21/2022] [Indexed: 12/23/2022]
Abstract
Developing in silico models that accurately reflect a whole, functional cell is an ongoing challenge in biology. Current efforts bring together mathematical models, probabilistic models, visual representations, and data to create a multi-scale description of cellular processes. A realistic whole-cell model requires imaging data since it provides spatial constraints and other critical cellular characteristics that are still impossible to obtain by calculation alone. This review introduces Soft X-ray Tomography (SXT) as a powerful imaging technique to visualize and quantify the mesoscopic (~25 nm spatial scale) organelle landscape in whole cells. SXT generates three-dimensional reconstructions of cellular ultrastructure and provides a measured structural framework for whole-cell modeling. Combining SXT with data from disparate technologies at varying spatial resolutions provides further biochemical details and constraints for modeling cellular mechanisms. We conclude, based on the results discussed here, that SXT provides a foundational dataset for a broad spectrum of whole-cell modeling experiments.
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Affiliation(s)
- Valentina Loconte
- Department of AnatomyUniversity of California San FranciscoSan FranciscoCaliforniaUSA
- Molecular Biophysics and Integrated Bioimaging DivisionLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
- National Center for X‐ray TomographyAdvanced Light SourceBerkeleyCaliforniaUSA
| | - Jian‐Hua Chen
- Department of AnatomyUniversity of California San FranciscoSan FranciscoCaliforniaUSA
- Molecular Biophysics and Integrated Bioimaging DivisionLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
- National Center for X‐ray TomographyAdvanced Light SourceBerkeleyCaliforniaUSA
| | - Bieke Vanslembrouck
- Department of AnatomyUniversity of California San FranciscoSan FranciscoCaliforniaUSA
- Molecular Biophysics and Integrated Bioimaging DivisionLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
- National Center for X‐ray TomographyAdvanced Light SourceBerkeleyCaliforniaUSA
| | - Axel A. Ekman
- National Center for X‐ray TomographyAdvanced Light SourceBerkeleyCaliforniaUSA
| | - Gerry McDermott
- Department of AnatomyUniversity of California San FranciscoSan FranciscoCaliforniaUSA
- Molecular Biophysics and Integrated Bioimaging DivisionLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
- National Center for X‐ray TomographyAdvanced Light SourceBerkeleyCaliforniaUSA
| | - Mark A. Le Gros
- Department of AnatomyUniversity of California San FranciscoSan FranciscoCaliforniaUSA
- Molecular Biophysics and Integrated Bioimaging DivisionLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
- National Center for X‐ray TomographyAdvanced Light SourceBerkeleyCaliforniaUSA
| | - Carolyn A. Larabell
- Department of AnatomyUniversity of California San FranciscoSan FranciscoCaliforniaUSA
- Molecular Biophysics and Integrated Bioimaging DivisionLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
- National Center for X‐ray TomographyAdvanced Light SourceBerkeleyCaliforniaUSA
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6
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Loconte V, Singla J, Li A, Chen JH, Ekman A, McDermott G, Sali A, Le Gros M, White KL, Larabell CA. Soft X-ray tomography to map and quantify organelle interactions at the mesoscale. Structure 2022; 30:510-521.e3. [PMID: 35148829 PMCID: PMC9013509 DOI: 10.1016/j.str.2022.01.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 12/04/2021] [Accepted: 01/17/2022] [Indexed: 12/11/2022]
Abstract
Inter-organelle interactions are a vital part of normal cellular function; however, these have proven difficult to quantify due to the range of scales encountered in cell biology and the throughput limitations of traditional imaging approaches. Here, we demonstrate that soft X-ray tomography (SXT) can be used to rapidly map ultrastructural reorganization and inter-organelle interactions in intact cells. SXT takes advantage of the naturally occurring, differential X-ray absorption of the carbon-rich compounds in each organelle. Specifically, we use SXT to map the spatiotemporal evolution of insulin vesicles and their co-localization and interaction with mitochondria in pancreatic β cells during insulin secretion and in response to different stimuli. We quantify changes in the morphology, biochemical composition, and relative position of mitochondria and insulin vesicles. These findings highlight the importance of a comprehensive and unbiased mapping at the mesoscale to characterize cell reorganization that would be difficult to detect with other existing methodologies.
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Affiliation(s)
- Valentina Loconte
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Jitin Singla
- Department of Chemistry, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA
| | - Angdi Li
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Jian-Hua Chen
- Department of Anatomy, University of California San Francisco, San Francisco, CA 94143, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Axel Ekman
- Department of Anatomy, University of California San Francisco, San Francisco, CA 94143, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Gerry McDermott
- Department of Anatomy, University of California San Francisco, San Francisco, CA 94143, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Science, Department of Pharmaceutical Chemistry, California Institute of Quantitative Bioscience, University of California San Francisco, San Francisco, CA 94158, USA
| | - Mark Le Gros
- Department of Anatomy, University of California San Francisco, San Francisco, CA 94143, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Kate L White
- Department of Chemistry, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA.
| | - Carolyn A Larabell
- Department of Anatomy, University of California San Francisco, San Francisco, CA 94143, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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7
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Ferri G, Pesce L, Tesi M, Marchetti P, Cardarelli F. β-Cell Pathophysiology: A Review of Advanced Optical Microscopy Applications. Int J Mol Sci 2021; 22:ijms222312820. [PMID: 34884624 PMCID: PMC8657725 DOI: 10.3390/ijms222312820] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 11/24/2021] [Accepted: 11/24/2021] [Indexed: 11/30/2022] Open
Abstract
β-cells convert glucose (input) resulting in the controlled release of insulin (output), which in turn has the role to maintain glucose homeostasis. β-cell function is regulated by a complex interplay between the metabolic processing of the input, its transformation into second-messenger signals, and final mobilization of insulin-containing granules towards secretion of the output. Failure at any level in this process marks β-cell dysfunction in diabetes, thus making β-cells obvious potential targets for therapeutic purposes. Addressing quantitatively β-cell (dys)function at the molecular level in living samples requires probing simultaneously the spatial and temporal dimensions at the proper resolution. To this aim, an increasing amount of research efforts are exploiting the potentiality of biophysical techniques. In particular, using excitation light in the visible/infrared range, a number of optical-microscopy-based approaches have been tailored to the study of β-cell-(dys)function at the molecular level, either in label-free mode (i.e., exploiting intrinsic autofluorescence of cells) or by the use of organic/genetically-encoded fluorescent probes. Here, relevant examples from the literature are reviewed and discussed. Based on this, new potential lines of development in the field are drawn.
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Affiliation(s)
- Gianmarco Ferri
- NEST Laboratory, Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; (G.F.); (L.P.)
| | - Luca Pesce
- NEST Laboratory, Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; (G.F.); (L.P.)
| | - Marta Tesi
- Islet Cell Laboratory, Department of Clinical and Experimental Medicine, University of Pisa, 56127 Pisa, Italy; (M.T.); (P.M.)
| | - Piero Marchetti
- Islet Cell Laboratory, Department of Clinical and Experimental Medicine, University of Pisa, 56127 Pisa, Italy; (M.T.); (P.M.)
| | - Francesco Cardarelli
- NEST Laboratory, Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; (G.F.); (L.P.)
- Correspondence:
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8
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Abstract
β-Cells in the islet of Langerhans have a central role in maintaining energy homeostasis. Understanding the physiology of β-cells and other islet cells requires a deep understanding of their structural and functional organization, their interaction with vessels and nerves, the layout of paracrine interactions, and the relationship between subcellular compartments and protein complexes inside each cell. These elements are not static; they are dynamic and exert their biological actions at different scales of time. Therefore, scientists must be able to investigate (and visualize) short- and long-lived events within the pancreas and β-cells. Current technological advances in microscopy are able to bridge multiple spatiotemporal scales in biology to reveal the complexity and heterogeneity of β-cell biology. Here, I briefly discuss the historical discoveries that leveraged microscopes to establish the basis of β-cell anatomy and structure, the current imaging platforms that allow the study of islet and β-cell biology at multiple scales of resolution, and their challenges and implications. Lastly, I outline how the remarkable longevity of structural elements at different scales in biology, from molecules to cells to multicellular structures, could represent a previously unrecognized organizational pattern in developing and adult β-cells and pancreas biology.
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Affiliation(s)
- Rafael Arrojo E Drigo
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
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9
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Kemter E, Müller A, Neukam M, Ivanova A, Klymiuk N, Renner S, Yang K, Broichhagen J, Kurome M, Zakhartchenko V, Kessler B, Knoch KP, Bickle M, Ludwig B, Johnsson K, Lickert H, Kurth T, Wolf E, Solimena M. Sequential in vivo labeling of insulin secretory granule pools in INS- SNAP transgenic pigs. Proc Natl Acad Sci U S A 2021; 118:e2107665118. [PMID: 34508004 PMCID: PMC8449372 DOI: 10.1073/pnas.2107665118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2021] [Indexed: 12/16/2022] Open
Abstract
β cells produce, store, and secrete insulin upon elevated blood glucose levels. Insulin secretion is a highly regulated process. The probability for insulin secretory granules to undergo fusion with the plasma membrane or being degraded is correlated with their age. However, the molecular features and stimuli connected to this behavior have not yet been fully understood. Furthermore, our understanding of β cell function is mostly derived from studies of ex vivo isolated islets in rodent models. To overcome this translational gap and study insulin secretory granule turnover in vivo, we have generated a transgenic pig model with the SNAP-tag fused to insulin. We demonstrate the correct targeting and processing of the tagged insulin and normal glycemic control of the pig model. Furthermore, we show specific single- and dual-color granular labeling of in vivo-labeled pig pancreas. This model may provide unprecedented insights into the in vivo insulin secretory granule behavior in an animal close to humans.
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Affiliation(s)
- Elisabeth Kemter
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- German Center for Diabetes Research, 85764 Neuherberg, Germany
| | - Andreas Müller
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Martin Neukam
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Anna Ivanova
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Nikolai Klymiuk
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
| | - Simone Renner
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- German Center for Diabetes Research, 85764 Neuherberg, Germany
| | - Kaiyuan Yang
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Institute of Diabetes and Regeneration Research, Helmholtz Diabetes Center, Helmholtz Center Munich, 85764 Neuherberg, Germany
| | - Johannes Broichhagen
- Department of Chemical Biology, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
- Chemical Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, 13125 Berlin, Germany
| | - Mayuko Kurome
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
| | - Valeri Zakhartchenko
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
| | - Barbara Kessler
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
| | - Klaus-Peter Knoch
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Marc Bickle
- Technology Development Studio (TDS), Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Barbara Ludwig
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Department of Medicine III, University Hospital Carl Gustav Carus, 01307 Dresden, Germany
| | - Kai Johnsson
- Department of Chemical Biology, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Heiko Lickert
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Institute of Diabetes and Regeneration Research, Helmholtz Diabetes Center, Helmholtz Center Munich, 85764 Neuherberg, Germany
| | - Thomas Kurth
- Center for Molecular and Cellular Bioengineering Technology Platform, Technische Universität Dresden, 01307 Dresden, Germany
| | - Eckhard Wolf
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany;
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- German Center for Diabetes Research, 85764 Neuherberg, Germany
| | - Michele Solimena
- German Center for Diabetes Research, 85764 Neuherberg, Germany;
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
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10
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Ferri G, Tesi M, Pesce L, Bugliani M, Grano F, Occhipinti M, Suleiman M, De Luca C, Marselli L, Marchetti P, Cardarelli F. Spatiotemporal Correlation Spectroscopy Reveals a Protective Effect of Peptide-Based GLP-1 Receptor Agonism against Lipotoxicity on Insulin Granule Dynamics in Primary Human β-Cells. Pharmaceutics 2021; 13:pharmaceutics13091403. [PMID: 34575477 PMCID: PMC8464798 DOI: 10.3390/pharmaceutics13091403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 08/18/2021] [Accepted: 09/02/2021] [Indexed: 12/25/2022] Open
Abstract
Glucagon-like peptide-1 receptor (GLP-1R) agonists are being used for the treatment of type 2 diabetes (T2D) and may have beneficial effects on the pancreatic β-cells. Here, we evaluated the effects of GLP-1R agonism on insulin secretory granule (ISG) dynamics in primary β-cells isolated from human islets exposed to palmitate-induced lipotoxic stress. Islets cells were exposed for 48 h to 0.5 mM palmitate (hereafter, ‘Palm’) with or without the addition of a GLP-1 agonist, namely 10 nM exendin-4 (hereafter, ‘Ex-4’). Dissociated cells were first transfected with syncollin-EGFP in order to fluorescently mark the ISGs. Then, by applying a recently established spatiotemporal correlation spectroscopy technique, the average structural (i.e., size) and dynamic (i.e., the local diffusivity and mode of motion) properties of ISGs are extracted from a calculated imaging-derived Mean Square Displacement (iMSD) trace. Besides defining the structural/dynamic fingerprint of ISGs in human cells for the first time, iMSD analysis allowed to probe fingerprint variations under selected conditions: namely, it was shown that Palm affects ISGs dynamics in response to acute glucose stimulation by abolishing the ISGs mobilization typically imparted by glucose and, concomitantly, by reducing the extent of ISGs active/directed intracellular movement. By contrast, co-treatment with Ex-4 normalizes ISG dynamics, i.e., re-establish ISG mobilization and ability to perform active transport in response to glucose stimulation. These observations were correlated with standard glucose-stimulated insulin secretion (GSIS), which resulted in being reduced in cells exposed to Palm but preserved in cells concomitantly exposed to 10 nM Ex-4. Our data support the idea that GLP-1R agonism may exert its beneficial effect on human β-cells under metabolic stress by maintaining ISGs’ proper intracellular dynamics.
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Affiliation(s)
- Gianmarco Ferri
- Laboratorio NEST-Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; (G.F.); (L.P.)
| | - Marta Tesi
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56127 Pisa, Italy; (M.T.); (M.B.); (F.G.); (M.O.); (M.S.); (C.D.L.); (L.M.); (P.M.)
| | - Luca Pesce
- Laboratorio NEST-Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; (G.F.); (L.P.)
| | - Marco Bugliani
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56127 Pisa, Italy; (M.T.); (M.B.); (F.G.); (M.O.); (M.S.); (C.D.L.); (L.M.); (P.M.)
| | - Francesca Grano
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56127 Pisa, Italy; (M.T.); (M.B.); (F.G.); (M.O.); (M.S.); (C.D.L.); (L.M.); (P.M.)
| | - Margherita Occhipinti
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56127 Pisa, Italy; (M.T.); (M.B.); (F.G.); (M.O.); (M.S.); (C.D.L.); (L.M.); (P.M.)
| | - Mara Suleiman
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56127 Pisa, Italy; (M.T.); (M.B.); (F.G.); (M.O.); (M.S.); (C.D.L.); (L.M.); (P.M.)
| | - Carmela De Luca
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56127 Pisa, Italy; (M.T.); (M.B.); (F.G.); (M.O.); (M.S.); (C.D.L.); (L.M.); (P.M.)
| | - Lorella Marselli
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56127 Pisa, Italy; (M.T.); (M.B.); (F.G.); (M.O.); (M.S.); (C.D.L.); (L.M.); (P.M.)
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56127 Pisa, Italy; (M.T.); (M.B.); (F.G.); (M.O.); (M.S.); (C.D.L.); (L.M.); (P.M.)
| | - Francesco Cardarelli
- Laboratorio NEST-Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; (G.F.); (L.P.)
- Correspondence:
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11
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Hu R, Zhu X, Yuan M, Ho KH, Kaverina I, Gu G. Microtubules and Gαo-signaling modulate the preferential secretion of young insulin secretory granules in islet β cells via independent pathways. PLoS One 2021; 16:e0241939. [PMID: 34292976 PMCID: PMC8297875 DOI: 10.1371/journal.pone.0241939] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 06/15/2021] [Indexed: 12/24/2022] Open
Abstract
For sustainable function, each pancreatic islet β cell maintains thousands of insulin secretory granules (SGs) at all times. Glucose stimulation induces the secretion of a small portion of these SGs and simultaneously boosts SG biosynthesis to sustain this stock. The failure of these processes, often induced by sustained high-insulin output, results in type 2 diabetes. Intriguingly, young insulin SGs are more likely secreted during glucose-stimulated insulin secretion (GSIS) for unknown reasons, while older SGs tend to lose releasability and be degraded. Here, we examine the roles of microtubule (MT) and Gαo-signaling in regulating the preferential secretion of young versus old SGs. We show that both MT-destabilization and Gαo inactivation results in more SGs localization near plasma membrane (PM) despite higher levels of GSIS and reduced SG biosynthesis. Intriguingly, MT-destabilization or Gαo-inactivation results in higher secretion probabilities of older SGs, while combining both having additive effects on boosting GSIS. Lastly, Gαo inactivation does not detectably destabilize the β-cell MT network. These findings suggest that Gαo and MT can modulate the preferential release of younger insulin SGs via largely parallel pathways.
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Affiliation(s)
- Ruiying Hu
- Department of Cell and Developmental Biology, The Program of Developmental Biology and the Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, United States of America
| | - Xiaodong Zhu
- Department of Cell and Developmental Biology, The Program of Developmental Biology and the Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, United States of America
| | - Mingyang Yuan
- Department of Cell and Developmental Biology, The Program of Developmental Biology and the Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, United States of America
| | - Kung-Hsien Ho
- Department of Cell and Developmental Biology, The Program of Developmental Biology and the Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, United States of America
| | - Irina Kaverina
- Department of Cell and Developmental Biology, The Program of Developmental Biology and the Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, United States of America
- * E-mail: (GG); (IK)
| | - Guoqiang Gu
- Department of Cell and Developmental Biology, The Program of Developmental Biology and the Center for Stem Cell Biology, Vanderbilt University, Nashville, TN, United States of America
- * E-mail: (GG); (IK)
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12
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de Boer P, Giepmans BN. State-of-the-art microscopy to understand islets of Langerhans: what to expect next? Immunol Cell Biol 2021; 99:509-520. [PMID: 33667022 PMCID: PMC8252556 DOI: 10.1111/imcb.12450] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 03/03/2021] [Accepted: 03/04/2021] [Indexed: 12/12/2022]
Abstract
The discovery of Langerhans and microscopic description of islets in the pancreas were crucial steps in the discovery of insulin. Over the past 150 years, many discoveries in islet biology and type 1 diabetes have been made using powerful microscopic techniques. In the past decade, combination of new probes, animal and tissue models, application of new biosensors and automation of light and electron microscopic methods and other (sub)cellular imaging modalities have proven their potential in understanding the beta cell under (patho)physiological conditions. The imaging evolution, from fluorescent jellyfish to real‐time intravital functional imaging, the revolution in automation and data handling and the increased resolving power of analytical imaging techniques are now converging. Here, we review innovative approaches that address islet biology from new angles by studying cells and molecules at high spatiotemporal resolution and in live models. Broad implementation of these cellular imaging techniques will shed new light on cause/consequence of (mal)function in islets of Langerhans in the years to come.
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Affiliation(s)
- Pascal de Boer
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Ben Ng Giepmans
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
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13
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Ghazvini Zadeh EH, Huang Z, Xia J, Li D, Davidson HW, Li WH. ZIGIR, a Granule-Specific Zn 2+ Indicator, Reveals Human Islet α Cell Heterogeneity. Cell Rep 2021; 32:107904. [PMID: 32668245 DOI: 10.1016/j.celrep.2020.107904] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 05/04/2020] [Accepted: 06/23/2020] [Indexed: 02/07/2023] Open
Abstract
Numerous mammalian cells contain abundant Zn2+ in their secretory granules, yet available Zn2+ sensors lack the desired specificity and sensitivity for imaging granular Zn2+. We developed a fluorescent zinc granule indicator, ZIGIR, that possesses numerous desired properties for live cell imaging, including >100-fold fluorescence enhancement, membrane permeability, and selective enrichment to acidic granules. The combined advantages endow ZIGIR with superior sensitivity and specificity for imaging granular Zn2+. ZIGIR enables separation of heterogenous β cells based on their insulin content and sorting of mouse islets into pure α cells and β cells. In human islets, ZIGIR facilitates sorting of endocrine cells into highly enriched α cells and β cells, reveals unexpectedly high Zn2+ activity in the somatostatin granule of some δ cells, and uncovers variation in the glucagon content among human α cells. We expect broad applications of ZIGIR for studying Zn2+ biology and Zn2+-rich secretory granules and for engineering β cells with high insulin content for treating diabetes.
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Affiliation(s)
- Ebrahim H Ghazvini Zadeh
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA
| | - ZhiJiang Huang
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA
| | - Jing Xia
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA; Department of Biological Sciences, The University of Texas at Dallas, Richardson, TX, USA
| | - Daliang Li
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA
| | - Howard W Davidson
- Barbara Davis Center for Diabetes, University of Colorado Denver Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Wen-Hong Li
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, USA.
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14
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Müller A, Schmidt D, Xu CS, Pang S, D’Costa JV, Kretschmar S, Münster C, Kurth T, Jug F, Weigert M, Hess HF, Solimena M. 3D FIB-SEM reconstruction of microtubule-organelle interaction in whole primary mouse β cells. J Cell Biol 2021; 220:e202010039. [PMID: 33326005 PMCID: PMC7748794 DOI: 10.1083/jcb.202010039] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 11/14/2020] [Accepted: 11/18/2020] [Indexed: 11/22/2022] Open
Abstract
Microtubules play a major role in intracellular trafficking of vesicles in endocrine cells. Detailed knowledge of microtubule organization and their relation to other cell constituents is crucial for understanding cell function. However, their role in insulin transport and secretion is under debate. Here, we use FIB-SEM to image islet β cells in their entirety with unprecedented resolution. We reconstruct mitochondria, Golgi apparati, centrioles, insulin secretory granules, and microtubules of seven β cells, and generate a comprehensive spatial map of microtubule-organelle interactions. We find that microtubules form nonradial networks that are predominantly not connected to either centrioles or endomembranes. Microtubule number and length, but not microtubule polymer density, vary with glucose stimulation. Furthermore, insulin secretory granules are enriched near the plasma membrane, where they associate with microtubules. In summary, we provide the first 3D reconstructions of complete microtubule networks in primary mammalian cells together with evidence regarding their importance for insulin secretory granule positioning and thus their supportive role in insulin secretion.
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Affiliation(s)
- Andreas Müller
- Molecular Diabetology, University Hospital and Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Deborah Schmidt
- Center for Systems Biology Dresden, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - C. Shan Xu
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Song Pang
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Joyson Verner D’Costa
- Molecular Diabetology, University Hospital and Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Susanne Kretschmar
- Center for Molecular and Cellular Bioengineering, Technology Platform, Technische Universität Dresden, Dresden, Germany
| | - Carla Münster
- Molecular Diabetology, University Hospital and Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Thomas Kurth
- Center for Molecular and Cellular Bioengineering, Technology Platform, Technische Universität Dresden, Dresden, Germany
| | - Florian Jug
- Center for Systems Biology Dresden, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Fondazione Human Technopole, Milano, Italy
| | - Martin Weigert
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Harald F. Hess
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Michele Solimena
- Molecular Diabetology, University Hospital and Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the University Hospital and Faculty of Medicine, Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
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15
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White KL, Singla J, Loconte V, Chen JH, Ekman A, Sun L, Zhang X, Francis JP, Li A, Lin W, Tseng K, McDermott G, Alber F, Sali A, Larabell C, Stevens RC. Visualizing subcellular rearrangements in intact β cells using soft x-ray tomography. SCIENCE ADVANCES 2020; 6:eabc8262. [PMID: 33298443 PMCID: PMC7725475 DOI: 10.1126/sciadv.abc8262] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 10/21/2020] [Indexed: 05/21/2023]
Abstract
Characterizing relationships between cell structures and functions requires mesoscale mapping of intact cells showing subcellular rearrangements following stimulation; however, current approaches are limited in this regard. Here, we report a unique application of soft x-ray tomography to generate three-dimensional reconstructions of whole pancreatic β cells at different time points following glucose-stimulated insulin secretion. Reconstructions following stimulation showed distinct insulin vesicle distribution patterns reflective of altered vesicle pool sizes as they travel through the secretory pathway. Our results show that glucose stimulation caused rapid changes in biochemical composition and/or density of insulin packing, increased mitochondrial volume, and closer proximity of insulin vesicles to mitochondria. Costimulation with exendin-4 (a glucagon-like peptide-1 receptor agonist) prolonged these effects and increased insulin packaging efficiency and vesicle maturation. This study provides unique perspectives on the coordinated structural reorganization and interactions of organelles that dictate cell responses.
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Affiliation(s)
- Kate L White
- Department of Biological Sciences, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA.
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Jitin Singla
- Department of Biological Sciences, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA
- Institute for Quantitative and Computational Biosciences, Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Valentina Loconte
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Jian-Hua Chen
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Axel Ekman
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Liping Sun
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Xianjun Zhang
- Department of Biological Sciences, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA
| | - John Paul Francis
- Department of Computer Science, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA
| | - Angdi Li
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Wen Lin
- Department of Chemistry, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA
| | - Kaylee Tseng
- Department of Biological Sciences, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA
| | - Gerry McDermott
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Frank Alber
- Department of Biological Sciences, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA
- Institute for Quantitative and Computational Biosciences, Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Andrej Sali
- California Institute for Quantitative Biosciences, Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94158, USA.
| | - Carolyn Larabell
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Raymond C Stevens
- Department of Biological Sciences, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA.
- iHuman Institute, School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
- Department of Chemistry, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA 90089, USA
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16
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Bednarska J, Novak P, Korchev Y, Rorsman P, Tarasov AI, Shevchuk A. Release of insulin granules by simultaneous, high-speed correlative SICM-FCM. J Microsc 2020; 282:21-29. [PMID: 33089519 DOI: 10.1111/jmi.12972] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 10/19/2020] [Indexed: 11/27/2022]
Abstract
Exocytosis of peptides and steroids stored in a dense core vesicular (DCV) form is the final step of every secretory pathway, indispensable for the function of nervous, endocrine and immune systems. The lack of live imaging techniques capable of direct, label-free visualisation of DCV release makes many aspects of the exocytotic process inaccessible to investigation. We describe the application of correlative scanning ion conductance and fluorescence confocal microscopy (SICM-FCM) to study the exocytosis of individual granules of insulin from the top, nonadherent, surface of pancreatic β-cells. Using SICM-FCM, we were first to directly follow the topographical changes associated with physiologically induced release of insulin DCVs. This allowed us to report the kinetics of the full fusion of the insulin vesicle as well as the subsequent solubilisation of the released insulin crystal.
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Affiliation(s)
- J Bednarska
- Department of Medicine, Imperial College London, London, U.K
| | - P Novak
- Department of Medicine, Imperial College London, London, U.K.,National University of Science and Technology 'MISIS', Moscow, Russian Federation
| | - Y Korchev
- Department of Medicine, Imperial College London, London, U.K.,Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa, Japan
| | - P Rorsman
- OCDEM, Radcliffe Department of Medicine, University of Oxford, Oxford, U.K
| | - A I Tarasov
- OCDEM, Radcliffe Department of Medicine, University of Oxford, Oxford, U.K.,School of Biomedical Sciences, Ulster University, Coleraine, U.K
| | - Andrew Shevchuk
- Department of Medicine, Imperial College London, London, U.K
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17
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Dzianová P, Asai S, Chrudinová M, Kosinová L, Potalitsyn P, Šácha P, Hadravová R, Selicharová I, Kříž J, Turkenburg JP, Brzozowski AM, Jiráček J, Žáková L. The efficiency of insulin production and its content in insulin-expressing model β-cells correlate with their Zn 2+ levels. Open Biol 2020; 10:200137. [PMID: 33081637 PMCID: PMC7653362 DOI: 10.1098/rsob.200137] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 09/24/2020] [Indexed: 12/29/2022] Open
Abstract
Insulin is produced and stored inside the pancreatic β-cell secretory granules, where it is assumed to form Zn2+-stabilized oligomers. However, the actual storage forms of this hormone and the impact of zinc ions on insulin production in vivo are not known. Our initial X-ray fluorescence experiment on granules from native Langerhans islets and insulinoma-derived INS-1E cells revealed a considerable difference in the zinc content. This led our further investigation to evaluate the impact of the intra-granular Zn2+ levels on the production and storage of insulin in different model β-cells. Here, we systematically compared zinc and insulin contents in the permanent INS-1E and BRIN-BD11 β-cells and in the native rat pancreatic islets by flow cytometry, confocal microscopy, immunoblotting, specific messenger RNA (mRNA) and total insulin analysis. These studies revealed an impaired insulin production in the permanent β-cell lines with the diminished intracellular zinc content. The drop in insulin and Zn2+ levels was paralleled by a lower expression of ZnT8 zinc transporter mRNA and hampered proinsulin processing/folding in both permanent cell lines. To summarize, we showed that the disruption of zinc homeostasis in the model β-cells correlated with their impaired insulin and ZnT8 production. This indicates a need for in-depth fundamental research about the role of zinc in insulin production and storage.
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Affiliation(s)
- Petra Dzianová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 116 10 Prague 6, Czech Republic
| | - Seiya Asai
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 116 10 Prague 6, Czech Republic
- Department of Biochemistry, Faculty of Science, Charles University, 12840 Prague 2, Czech Republic
| | - Martina Chrudinová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 116 10 Prague 6, Czech Republic
| | - Lucie Kosinová
- Laboratory of Pancreatic Islets, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague, Czech Republic
| | - Pavlo Potalitsyn
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 116 10 Prague 6, Czech Republic
- Department of Biochemistry, Faculty of Science, Charles University, 12840 Prague 2, Czech Republic
| | - Pavel Šácha
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 116 10 Prague 6, Czech Republic
| | - Romana Hadravová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 116 10 Prague 6, Czech Republic
| | - Irena Selicharová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 116 10 Prague 6, Czech Republic
| | - Jan Kříž
- Laboratory of Pancreatic Islets, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague, Czech Republic
| | - Johan P. Turkenburg
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Andrzej Marek Brzozowski
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Jiří Jiráček
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 116 10 Prague 6, Czech Republic
| | - Lenka Žáková
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 116 10 Prague 6, Czech Republic
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18
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Yau B, Hays L, Liang C, Laybutt DR, Thomas HE, Gunton JE, Williams L, Hawthorne WJ, Thorn P, Rhodes CJ, Kebede MA. A fluorescent timer reporter enables sorting of insulin secretory granules by age. J Biol Chem 2020; 295:8901-8911. [PMID: 32341128 PMCID: PMC7335792 DOI: 10.1074/jbc.ra120.012432] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Revised: 03/21/2020] [Indexed: 01/03/2023] Open
Abstract
Within the pancreatic β-cells, insulin secretory granules (SGs) exist in functionally distinct pools, displaying variations in motility as well as docking and fusion capability. Current therapies that increase insulin secretion do not consider the existence of these distinct SG pools. Accordingly, these approaches are effective only for a short period, with a worsening of glycemia associated with continued decline in β-cell function. Insulin granule age is underappreciated as a determinant for why an insulin granule is selected for secretion and may explain why newly synthesized insulin is preferentially secreted from β-cells. Here, using a novel fluorescent timer protein, we aimed to investigate the preferential secretion model of insulin secretion and identify how granule aging is affected by variation in the β-cell environment, such as hyperglycemia. We demonstrate the use of a fluorescent timer construct, syncollin-dsRedE5TIMER, which changes its fluorescence from green to red over 18 h, in both microscopy and fluorescence-assisted organelle-sorting techniques. We confirm that the SG-targeting construct localizes to insulin granules in β-cells and does not interfere with normal insulin SG behavior. We visualize insulin SG aging behavior in MIN6 and INS1 β-cell lines and in primary C57BL/6J mouse and nondiabetic human islet cells. Finally, we separated young and old insulin SGs, revealing that preferential secretion of younger granules occurs in glucose-stimulated insulin secretion. We also show that SG population age is modulated by the β-cell environment in vivo in the db/db mouse islets and ex vivo in C57BL/6J islets exposed to different glucose environments.
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Affiliation(s)
- Belinda Yau
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; School of Life and Environmental Sciences, Faculty of Science, University of Sydney, Sydney, New South Wales, Australia
| | - Lori Hays
- STEM-Department of Biology, Edmonds Community College, Lynnwood, Washington, USA
| | - Cassandra Liang
- Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - D Ross Laybutt
- Garvan Institute of Medical Research, Sydney, New South Wales, Australia; St. Vincent's Clinical School, University of New South Wales Sydney, Sydney, New South Wales, Australia
| | - Helen E Thomas
- St. Vincent's Institute, Fitzroy, Victoria, Australia; Department of Medicine, St. Vincent's Hospital, University of Melbourne, Fitzroy, Victoria, Australia
| | - Jenny E Gunton
- Faculty of Medicine and Health, the University of Sydney, Sydney, New South Wales, Australia; The Westmead Institute for Medical Research, University of Sydney, Westmead, New South Wales, Australia
| | - Lindy Williams
- Faculty of Medicine and Health, the University of Sydney, Sydney, New South Wales, Australia; National Pancreas and Islet Transplant Unit (NPITU), Westmead Hospital, Sydney, New South Wales, Australia
| | - Wayne J Hawthorne
- Faculty of Medicine and Health, the University of Sydney, Sydney, New South Wales, Australia; National Pancreas and Islet Transplant Unit (NPITU), Westmead Hospital, Sydney, New South Wales, Australia
| | - Peter Thorn
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; Discipline of Physiology, School of Medical Sciences, Faculty of Medicine and Health, Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Christopher J Rhodes
- Research and Early Development, Cardiovascular, Renal and Metabolic Diseases, BioPharmaceuticals R&D, AstraZeneca Ltd, Gaithersburg, Maryland, USA; Pacific Northwest Research Institute, Seattle, Washington, USA
| | - Melkam A Kebede
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; School of Life and Environmental Sciences, Faculty of Science, University of Sydney, Sydney, New South Wales, Australia.
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19
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Aghaei M, Khodadadian A, Elham KN, Nazari M, Babakhanzadeh E. Major miRNA Involved in Insulin Secretion and Production in Beta-Cells. Int J Gen Med 2020; 13:89-97. [PMID: 32210605 PMCID: PMC7071856 DOI: 10.2147/ijgm.s249011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Accepted: 03/03/2020] [Indexed: 12/17/2022] Open
Abstract
Insulin is implicated as a leading factor in glucose homeostasis and an important theme in diabetes mellitus (DM). Numerous proteins are involved in insulin signaling pathway and their dysregulation contributes to DM. microRNAs (miRNAs) as single-strand molecules have a critical effect on gene expression at post-transcriptional levels. Intensive investigation done by DM researchers disclosed that miRNAs have a significant role in insulin secretion by direct targeting numerous proteins engaged in insulin signaling pathway; so, their dysregulation contributes to DM. In this review, we presented some major miRNAs engaged in the insulin production and secretion.
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Affiliation(s)
- Mohsen Aghaei
- Department of Medical Genetics, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Ali Khodadadian
- Department of Medical Genetics, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Karimi-Nazari Elham
- Nutrition and Food Security Research Center, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Majid Nazari
- Department of Medical Genetics, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Emad Babakhanzadeh
- Department of Medical Genetics, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
- Medical Genetics Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
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20
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Atp6ap2 deletion causes extensive vacuolation that consumes the insulin content of pancreatic β cells. Proc Natl Acad Sci U S A 2019; 116:19983-19988. [PMID: 31527264 DOI: 10.1073/pnas.1903678116] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Pancreatic β cells store insulin within secretory granules which undergo exocytosis upon elevation of blood glucose levels. Crinophagy and autophagy are instead responsible to deliver damaged or old granules to acidic lysosomes for intracellular degradation. However, excessive consumption of insulin granules can impair β cell function and cause diabetes. Atp6ap2 is an essential accessory component of the vacuolar ATPase required for lysosomal degradative functions and autophagy. Here, we show that Cre recombinase-mediated conditional deletion of Atp6ap2 in mouse β cells causes a dramatic accumulation of large, multigranular vacuoles in the cytoplasm, with reduction of insulin content and compromised glucose homeostasis. Loss of insulin stores and gigantic vacuoles were also observed in cultured insulinoma INS-1 cells upon CRISPR/Cas9-mediated removal of Atp6ap2. Remarkably, these phenotypic alterations could not be attributed to a deficiency in autophagy or acidification of lysosomes. Together, these data indicate that Atp6ap2 is critical for regulating the stored insulin pool and that a balanced regulation of granule turnover is key to maintaining β cell function and diabetes prevention.
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21
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Sarkar S, Munshi C, Chatterjee S, Mukherjee S, Bhattacharya S. Vector-free in vivo trans-determination of adult hepatic stem cells to insulin-producing cells. Mol Biol Rep 2019; 46:5501-5509. [PMID: 31102150 DOI: 10.1007/s11033-019-04870-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Accepted: 05/10/2019] [Indexed: 01/14/2023]
Abstract
A reduction in the number of functional β-cells is the central pathological event in diabetes. Liver and ventral pancreas differentiates simultaneously in the same general domain of cells within embryonic endoderm. In addition, the precursor cell population being bi-potential may be targeted for either pancreas or liver development. Hepatic stem cells were redirected in vivo to functional insulin producing cells in a acetylaminofluorene-partial hepatectomy (AAF/PH) adult male rat model with/without GLP-1 treatment. In routine H&E histology and immunohistochemistry, stem cells resembled β cells in GLP-1 injected rats. Immunoblots revealed involvement of adenylate cyclase, TLR4 and PDX1 in insulin synthesis. Expression of genes (GLP-1R, MAFA, PDX1, INS1 and INS2) augmented in the GLP-1 treated regenerated liver. Results strongly indicated the key role of GLP-1 in the induction of insulin secretion in trans-determined reprogrammed cell in vivo. The present method being vector free poses no risk of vector spillover in the host and holds promise.
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Affiliation(s)
- Shuvasree Sarkar
- Environmental Toxicology Laboratory, Department of Zoology, Centre for Advanced Studies, Visva-Bharati University, Santiniketan, West Bengal, 731235, India
| | - Chayan Munshi
- Environmental Toxicology Laboratory, Department of Zoology, Centre for Advanced Studies, Visva-Bharati University, Santiniketan, West Bengal, 731235, India.,School of Environment and Life Sciences, University of Salford, Salford, UK
| | - Sarmishtha Chatterjee
- Environmental Toxicology Laboratory, Department of Zoology, Centre for Advanced Studies, Visva-Bharati University, Santiniketan, West Bengal, 731235, India.,, Kolkata, India
| | - Sandip Mukherjee
- Molecular Endocrinology Laboratory, Department of Zoology, Centre for Advanced Studies, Visva-Bharati University, Santiniketan, West Bengal, 731235, India
| | - Shelley Bhattacharya
- Environmental Toxicology Laboratory, Department of Zoology, Centre for Advanced Studies, Visva-Bharati University, Santiniketan, West Bengal, 731235, India.
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22
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Ferri G, Digiacomo L, Lavagnino Z, Occhipinti M, Bugliani M, Cappello V, Caracciolo G, Marchetti P, Piston DW, Cardarelli F. Insulin secretory granules labelled with phogrin-fluorescent proteins show alterations in size, mobility and responsiveness to glucose stimulation in living β-cells. Sci Rep 2019; 9:2890. [PMID: 30814595 PMCID: PMC6393586 DOI: 10.1038/s41598-019-39329-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 01/15/2019] [Indexed: 11/13/2022] Open
Abstract
The intracellular life of insulin secretory granules (ISGs) from biogenesis to secretion depends on their structural (e.g. size) and dynamic (e.g. diffusivity, mode of motion) properties. Thus, it would be useful to have rapid and robust measurements of such parameters in living β-cells. To provide such measurements, we have developed a fast spatiotemporal fluctuation spectroscopy. We calculate an imaging-derived Mean Squared Displacement (iMSD), which simultaneously provides the size, average diffusivity, and anomalous coefficient of ISGs, without the need to extract individual trajectories. Clustering of structural and dynamic quantities in a multidimensional parametric space defines the ISGs' properties for different conditions. First, we create a reference using INS-1E cells expressing proinsulin fused to a fluorescent protein (FP) under basal culture conditions and validate our analysis by testing well-established stimuli, such as glucose intake, cytoskeleton disruption, or cholesterol overload. After, we investigate the effect of FP-tagged ISG protein markers on the structural and dynamic properties of the granule. While iMSD analysis produces similar results for most of the lumenal markers, the transmembrane marker phogrin-FP shows a clearly altered result. Phogrin overexpression induces a substantial granule enlargement and higher mobility, together with a partial de-polymerization of the actin cytoskeleton, and reduced cell responsiveness to glucose stimulation. Our data suggest a more careful interpretation of many previous ISG-based reports in living β-cells. The presented data pave the way to high-throughput cell-based screening of ISG structure and dynamics under various physiological and pathological conditions.
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Affiliation(s)
- Gianmarco Ferri
- NEST - Scuola Normale Superiore, Istituto Nanoscienze - CNR (CNR-NANO), Pisa, Italy
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
| | - Luca Digiacomo
- Department of Molecular Medicine, "La Sapienza" University of Rome, Rome, Italy
| | - Zeno Lavagnino
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Margherita Occhipinti
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, Pisa, Italy
| | - Marco Bugliani
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, Pisa, Italy
| | | | - Giulio Caracciolo
- Department of Molecular Medicine, "La Sapienza" University of Rome, Rome, Italy
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, Pisa, Italy
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Francesco Cardarelli
- NEST - Scuola Normale Superiore, Istituto Nanoscienze - CNR (CNR-NANO), Pisa, Italy.
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23
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Firlar E, Ouy M, Covnot L, Xing Y, Lee D, Chan A, He Y, Song B, Afelik S, Wang Y, Shahbazian-Yassar R, Oberholzer J, Shokuhfar T. In situ graphene liquid cell-transmission electron microscopy study of insulin secretion in pancreatic islet cells. Int J Nanomedicine 2019; 14:371-382. [PMID: 30662261 PMCID: PMC6327893 DOI: 10.2147/ijn.s169506] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Islet cell transplantation is one of the key treatments for type 1 diabetes. Understanding the mechanisms of insulin fusion and exocytosis are of utmost importance for the improvement of the current islet cell transplantation and treatment of diabetes. These phenomena have not been fully evaluated due either to the lack of proper dynamic imaging, or the lack of proper cell preservation during imaging at nanoscales. METHODS By maintaining the native environment of pancreatic β-cells between two graphene monolayer sheets, we were able to monitor the subcellular events using in situ graphene liquid cell (GLC)-transmission electron microscopy (TEM) with both high temporal and high spatial resolution. RESULTS For the first time, the nucleation and growth of insulin particles until the later stages of fusion were imaged at nanometer scales. The release of insulin from plasma membrane involves the degradation of plasma membrane and drastic reductions in the shorter axis of the insulin particles. Sequential exocytosis results indicated the nucleation, growth and attachment of the new insulin particles to the already anchored ones, which is thermodynamically favorable due to the reduction in total surface, further reducing the Gibbs free energy. The retraction of the already anchored insulin toward the cell is also monitored for the first time live at nanoscale resolution. CONCLUSION Investigation of insulin granule dynamics in β-cells can be investigated via GLC-TEM. Our findings with this technology open new realms for the development of novel drugs on pathological pancreatic β-cells, because this approach facilitates observing the effects of the stimuli on the live cells and insulin granules.
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Affiliation(s)
- Emre Firlar
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA,
- University of Illinois at Chicago, Department of Mechanical and Industrial Engineering, Chicago, IL, USA,
| | - Meagan Ouy
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA,
| | - Leigha Covnot
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA,
| | - Yuan Xing
- University of Virginia, Department of Surgery, Charlottesville, VA, USA
| | - Daniel Lee
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA,
- University of Illinois at Chicago, Department of Surgery, Chicago, IL, USA
| | - Alessandro Chan
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA,
- University of Illinois at Chicago, Department of Surgery, Chicago, IL, USA
| | - Yi He
- University of Virginia, Department of Surgery, Charlottesville, VA, USA
| | - Boao Song
- University of Illinois at Chicago, Department of Mechanical and Industrial Engineering, Chicago, IL, USA,
| | - Solomon Afelik
- University of Illinois at Chicago, Department of Surgery, Chicago, IL, USA
| | - Yong Wang
- University of Virginia, Department of Surgery, Charlottesville, VA, USA
| | - Reza Shahbazian-Yassar
- University of Illinois at Chicago, Department of Mechanical and Industrial Engineering, Chicago, IL, USA,
| | - Jose Oberholzer
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA,
- University of Virginia, Department of Surgery, Charlottesville, VA, USA
| | - Tolou Shokuhfar
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA,
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24
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Ferri G, Bugliani M, Marchetti P, Cardarelli F. Probing the light scattering properties of insulin secretory granules in single live cells. Biochem Biophys Res Commun 2018; 503:2710-2714. [PMID: 30119894 DOI: 10.1016/j.bbrc.2018.08.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 08/03/2018] [Indexed: 11/22/2022]
Abstract
Light scattering was recently demonstrated to serve as an intrinsic indicator for pancreatic islet cell mass and secretion. The insulin secretory granule (ISG), in particular, was proposed to be a reasonable candidate as the main intracellular source of scattered light due to the densely-packed insulin semi-crystal in the granule lumen. This scenario, if confirmed, would in principle open new perspectives for label-free single-granule imaging, tracking, and analysis. Contrary to such expectations, here we demonstrate that ISGs are not a primary source of scattering in primary human β-cells, as well as in immortalized β-like cells, quantitatively not superior to other intracellular organelles/structures, such as lysosomes and internal membranes. This result is achieved through multi-channel imaging of scattered light along with fluorescence arising from selectively-labelled ISGs. Co-localization and spatiotemporal cross-correlation analysis is performed on these signals, and compared among different cell lines. Obtained results suggest a careful re-thinking of the possibility to exploit intrinsic optical properties originating from ISGs for single-granule imaging purposes.
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Affiliation(s)
- Gianmarco Ferri
- NEST - Scuola Normale Superiore, Istituto Nanoscienze - CNR (CNR NANO), Pisa, Italy; Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, Genova, 16163 Italy
| | - Marco Bugliani
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, Pisa, Italy
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, Pisa, Italy
| | - Francesco Cardarelli
- NEST - Scuola Normale Superiore, Istituto Nanoscienze - CNR (CNR NANO), Pisa, Italy.
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25
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Hospodiuk M, Dey M, Ayan B, Sosnoski D, Moncal KK, Wu Y, Ozbolat IT. Sprouting angiogenesis in engineered pseudo islets. Biofabrication 2018; 10:035003. [PMID: 29451122 DOI: 10.1088/1758-5090/aab002] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Despite the recent achievements in cell-based therapies for curing type-1 diabetes (T1D), capillarization in beta (β)-cell clusters is still a major roadblock as it is essential for long-term viability and function of β-cells in vivo. In this research, we report sprouting angiogenesis in engineered pseudo islets (EPIs) made of mouse insulinoma βTC3 cells and rat heart microvascular endothelial cells (RHMVECs). Upon culturing in three-dimensional (3D) constructs under angiogenic conditions, EPIs sprouted extensive capillaries into the surrounding matrix. Ultra-morphological analysis through histological sections also revealed presence of capillarization within EPIs. EPIs cultured in 3D constructs maintained their viability and functionality over time while non-vascularized EPIs, without the presence of RHMVECs, could not retain their viability nor functionality. Here we demonstrate angiogenesis in engineered islets, where patient specific stem cell-derived human beta cells can be combined with microvascular endothelial cells in the near future for long-term graft survival in T1D patients.
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Affiliation(s)
- Monika Hospodiuk
- The Huck Institutes of the Life Sciences, Penn State University, State College, PA 16801, United States of America. Department of Agriculture and Biological Engineering, Penn State University, State College, PA 16801, United States of America
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26
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Hastoy B, Clark A, Rorsman P, Lang J. Fusion pore in exocytosis: More than an exit gate? A β-cell perspective. Cell Calcium 2017; 68:45-61. [PMID: 29129207 DOI: 10.1016/j.ceca.2017.10.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 10/17/2017] [Accepted: 10/24/2017] [Indexed: 12/14/2022]
Abstract
Secretory vesicle exocytosis is a fundamental biological event and the process by which hormones (like insulin) are released into the blood. Considerable progress has been made in understanding this precisely orchestrated sequence of events from secretory vesicle docked at the cell membrane, hemifusion, to the opening of a membrane fusion pore. The exact biophysical and physiological regulation of these events implies a close interaction between membrane proteins and lipids in a confined space and constrained geometry to ensure appropriate delivery of cargo. We consider some of the still open questions such as the nature of the initiation of the fusion pore, the structure and the role of the Soluble N-ethylmaleimide-sensitive-factor Attachment protein REceptor (SNARE) transmembrane domains and their influence on the dynamics and regulation of exocytosis. We discuss how the membrane composition and protein-lipid interactions influence the likelihood of the nascent fusion pore forming. We relate these factors to the hypothesis that fusion pore expansion could be affected in type-2 diabetes via changes in disease-related gene transcription and alterations in the circulating lipid profile. Detailed characterisation of the dynamics of the fusion pore in vitro will contribute to understanding the larger issue of insulin secretory defects in diabetes.
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Affiliation(s)
- Benoit Hastoy
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK.
| | - Anne Clark
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK; Metabolic Research, Institute of Neuroscience and Physiology, University of Goteborg, Medicinaregatan 11, S-41309 Göteborg, Sweden
| | - Jochen Lang
- Laboratoire de Chimie et Biologie des Membranes et Nano-objets (CBMN), CNRS UMR 5248, Université de Bordeaux, Allée de Geoffrey St Hilaire, 33600 Pessac, France.
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27
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Müller A, Mziaut H, Neukam M, Knoch KP, Solimena M. A 4D view on insulin secretory granule turnover in the β-cell. Diabetes Obes Metab 2017; 19 Suppl 1:107-114. [PMID: 28880479 DOI: 10.1111/dom.13015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 05/16/2017] [Accepted: 05/17/2017] [Indexed: 01/31/2023]
Abstract
Insulin secretory granule (SG) turnover consists of several highly regulated processes allowing for proper β-cell function and insulin secretion. Besides the spatial distribution of insulin SGs, their age has great impact on the likelihood of their secretion and their behaviour within the β-cell. While quantitative measurements performed decades ago demonstrated the preferential secretion of young insulin, new experimental approaches aim to investigate insulin ageing at the granular level. Live-cell imaging, automated image analysis and correlative light and electron microscopy have fostered knowledge of age-defined insulin SG dynamics, their interaction with the cytoskeleton and ultrastructural features. Here, we review our recent work in regards to the connection between insulin SG age, SG dynamics, intracellular location and interaction with other proteins.
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Affiliation(s)
- Andreas Müller
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Hassan Mziaut
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Martin Neukam
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Klaus-Peter Knoch
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Michele Solimena
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany
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28
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Palivec V, Viola CM, Kozak M, Ganderton TR, Křížková K, Turkenburg JP, Haluŝková P, Žáková L, Jiráĉek J, Jungwirth P, Brzozowski AM. Computational and structural evidence for neurotransmitter-mediated modulation of the oligomeric states of human insulin in storage granules. J Biol Chem 2017; 292:8342-8355. [PMID: 28348075 PMCID: PMC5437240 DOI: 10.1074/jbc.m117.775924] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 03/23/2017] [Indexed: 11/23/2022] Open
Abstract
Human insulin is a pivotal protein hormone controlling metabolism, growth, and aging and whose malfunctioning underlies diabetes, some cancers, and neurodegeneration. Despite its central position in human physiology, the in vivo oligomeric state and conformation of insulin in its storage granules in the pancreas are not known. In contrast, many in vitro structures of hexamers of this hormone are available and fall into three conformational states: T6, T3Rf3, and R6 As there is strong evidence for accumulation of neurotransmitters, such as serotonin and dopamine, in insulin storage granules in pancreatic β-cells, we probed by molecular dynamics (MD) and protein crystallography (PC) if these endogenous ligands affect and stabilize insulin oligomers. Parallel studies independently converged on the observation that serotonin binds well within the insulin hexamer (site I), stabilizing it in the T3R3 conformation. Both methods indicated serotonin binding on the hexamer surface (site III) as well. MD, but not PC, indicated that dopamine was also a good site III ligand. Some of the PC studies also included arginine, which may be abundant in insulin granules upon processing of pro-insulin, and stable T3R3 hexamers loaded with both serotonin and arginine were obtained. The MD and PC results were supported further by in solution spectroscopic studies with R-state-specific chromophore. Our results indicate that the T3R3 oligomer is a plausible insulin pancreatic storage form, resulting from its complex interplay with neurotransmitters, and pro-insulin processing products. These findings may have implications for clinical insulin formulations.
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Affiliation(s)
- Vladimír Palivec
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic
| | - Cristina M Viola
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Mateusz Kozak
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Timothy R Ganderton
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Květoslava Křížková
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic
| | - Johan P Turkenburg
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Petra Haluŝková
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic
| | - Lenka Žáková
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic
| | - Jiří Jiráĉek
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic.
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic.
| | - Andrzej M Brzozowski
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
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29
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Müller A, Neukam M, Ivanova A, Sönmez A, Münster C, Kretschmar S, Kalaidzidis Y, Kurth T, Verbavatz JM, Solimena M. A Global Approach for Quantitative Super Resolution and Electron Microscopy on Cryo and Epoxy Sections Using Self-labeling Protein Tags. Sci Rep 2017; 7:23. [PMID: 28154417 PMCID: PMC5428382 DOI: 10.1038/s41598-017-00033-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 12/20/2016] [Indexed: 01/19/2023] Open
Abstract
Correlative light and electron microscopy (CLEM) is a powerful approach to investigate the molecular ultrastructure of labeled cell compartments. However, quantitative CLEM studies are rare, mainly due to small sample sizes and the sensitivity of fluorescent proteins to strong fixatives and contrasting reagents for EM. Here, we show that fusion of a self-labeling protein to insulin allows for the quantification of age-distinct insulin granule pools in pancreatic beta cells by a combination of super resolution and transmission electron microscopy on Tokuyasu cryosections. In contrast to fluorescent proteins like GFP organic dyes covalently bound to self-labeling proteins retain their fluorescence also in epoxy resin following high pressure freezing and freeze substitution, or remarkably even after strong chemical fixation. This enables for the assessment of age-defined granule morphology and degradation. Finally, we demonstrate that this CLEM protocol is highly versatile, being suitable for single and dual fluorescent labeling and detection of different proteins with optimal ultrastructure preservation and contrast.
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Affiliation(s)
- Andreas Müller
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Martin Neukam
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Anna Ivanova
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Anke Sönmez
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Carla Münster
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany.,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
| | - Susanne Kretschmar
- Center for Regenerative Therapies Dresden (CRTD), TU Dresden, Dresden, Germany.,Biotechnology Center of the TU Dresden (BIOTEC), Dresden, Germany
| | - Yannis Kalaidzidis
- Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany.,Faculty of Bioengineering and Bioinformatics, Moscow State University, Moscow, Russia
| | - Thomas Kurth
- Center for Regenerative Therapies Dresden (CRTD), TU Dresden, Dresden, Germany.,Biotechnology Center of the TU Dresden (BIOTEC), Dresden, Germany
| | - Jean-Marc Verbavatz
- Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany.,Institut Jacques Monod, Université Paris Diderot, Paris, France
| | - Michele Solimena
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany. .,Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany. .,Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany.
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30
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Dhara M, Yarzagaray A, Makke M, Schindeldecker B, Schwarz Y, Shaaban A, Sharma S, Böckmann RA, Lindau M, Mohrmann R, Bruns D. v-SNARE transmembrane domains function as catalysts for vesicle fusion. eLife 2016; 5:e17571. [PMID: 27343350 PMCID: PMC4972536 DOI: 10.7554/elife.17571] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 06/24/2016] [Indexed: 12/22/2022] Open
Abstract
Vesicle fusion is mediated by an assembly of SNARE proteins between opposing membranes, but it is unknown whether transmembrane domains (TMDs) of SNARE proteins serve mechanistic functions that go beyond passive anchoring of the force-generating SNAREpin to the fusing membranes. Here, we show that conformational flexibility of synaptobrevin-2 TMD is essential for efficient Ca(2+)-triggered exocytosis and actively promotes membrane fusion as well as fusion pore expansion. Specifically, the introduction of helix-stabilizing leucine residues within the TMD region spanning the vesicle's outer leaflet strongly impairs exocytosis and decelerates fusion pore dilation. In contrast, increasing the number of helix-destabilizing, ß-branched valine or isoleucine residues within the TMD restores normal secretion but accelerates fusion pore expansion beyond the rate found for the wildtype protein. These observations provide evidence that the synaptobrevin-2 TMD catalyzes the fusion process by its structural flexibility, actively setting the pace of fusion pore expansion.
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Affiliation(s)
- Madhurima Dhara
- Institute for Physiology, Saarland University, Homburg, Germany
| | | | - Mazen Makke
- Institute for Physiology, Saarland University, Homburg, Germany
| | | | - Yvonne Schwarz
- Institute for Physiology, Saarland University, Homburg, Germany
| | - Ahmed Shaaban
- Zentrum für Human- und Molekularbiologie, Saarland University, Homburg, Germany
| | - Satyan Sharma
- Group Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander University, Erlangen, Germany
| | - Manfred Lindau
- Group Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Ralf Mohrmann
- Zentrum für Human- und Molekularbiologie, Saarland University, Homburg, Germany
| | - Dieter Bruns
- Institute for Physiology, Saarland University, Homburg, Germany
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31
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Mziaut H, Mulligan B, Hoboth P, Otto O, Ivanova A, Herbig M, Schumann D, Hildebrandt T, Dehghany J, Sönmez A, Münster C, Meyer-Hermann M, Guck J, Kalaidzidis Y, Solimena M. The F-actin modifier villin regulates insulin granule dynamics and exocytosis downstream of islet cell autoantigen 512. Mol Metab 2016; 5:656-668. [PMID: 27656403 PMCID: PMC5021679 DOI: 10.1016/j.molmet.2016.05.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 05/20/2016] [Accepted: 05/24/2016] [Indexed: 01/02/2023] Open
Abstract
Objective Insulin release from pancreatic islet β cells should be tightly controlled to avoid hypoglycemia and insulin resistance. The cortical actin cytoskeleton is a gate for regulated exocytosis of insulin secretory granules (SGs) by restricting their mobility and access to the plasma membrane. Prior studies suggest that SGs interact with F-actin through their transmembrane cargo islet cell autoantigen 512 (Ica512) (also known as islet antigen 2/Ptprn). Here we investigated how Ica512 modulates SG trafficking and exocytosis. Methods Transcriptomic changes in Ica512−/− mouse islets were analyzed. Imaging as well as biophysical and biochemical methods were used to validate if and how the Ica512-regulated gene villin modulates insulin secretion in mouse islets and insulinoma cells. Results The F-actin modifier villin was consistently downregulated in Ica512−/− mouse islets and in Ica512-depleted insulinoma cells. Villin was enriched at the cell cortex of β cells and dispersed villin−/− islet cells were less round and less deformable. Basal mobility of SGs in villin-depleted cells was enhanced. Moreover, in cells depleted either of villin or Ica512 F-actin cages restraining cortical SGs were enlarged, basal secretion was increased while glucose-stimulated insulin release was blunted. The latter changes were reverted by overexpressing villin in Ica512-depleted cells, but not vice versa. Conclusion Our findings show that villin controls the size of the F-actin cages restricting SGs and, thus, regulates their dynamics and availability for exocytosis. Evidence that villin acts downstream of Ica512 also indicates that SGs directly influence the remodeling properties of the cortical actin cytoskeleton for tight control of insulin secretion. Ica512-depletion reduces the genetic expression of the F-actin modifier villin. Villin-depletion enhances basal insulin granule mobility and exocytosis. Villin regulates the size of actin cages restraining insulin granules. Villin acts downstream of insulin granule cargo Ica512. The Ica512-villin genetic link enables granules to control cytoskeleton plasticity.
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Key Words
- D, diffusion coefficient
- EGFP, enhanced green fluorescent protein
- F-actin
- Granules
- IPGTT, intraperitoneal glucose tolerance test
- IVGTT, intravenous glucose tolerance test
- Ica512
- Ica512, islet cell autoantigen
- Insulin
- OGTT, oral glucose tolerance test
- RT-DC, real-time deformability cytometry
- SE, standard error
- SG, secretory granules
- Secretion
- TIRFM, total internal reflection fluorescence microscopy
- Villin
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Affiliation(s)
- Hassan Mziaut
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Bernard Mulligan
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Peter Hoboth
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Oliver Otto
- Biotechnology Center Dresden, 01307 Dresden, Germany
| | - Anna Ivanova
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Maik Herbig
- Biotechnology Center Dresden, 01307 Dresden, Germany
| | - Desiree Schumann
- Boehringer Ingelheim Pharma GmbH & Co. KG. Cardiometabolic Research, 88397 Biberach, Germany
| | - Tobias Hildebrandt
- Boehringer Ingelheim Pharma GmbH & Co. KG. Cardiometabolic Research, 88397 Biberach, Germany
| | - Jaber Dehghany
- Helmholtz Centre for Infection Research (HZI), Braunschweig Integrated Centre for Systems Biology (BRICS), 38124 Braunschweig, Germany
| | - Anke Sönmez
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Carla Münster
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany
| | - Michael Meyer-Hermann
- Helmholtz Centre for Infection Research (HZI), Braunschweig Integrated Centre for Systems Biology (BRICS), 38124 Braunschweig, Germany
| | - Jochen Guck
- Biotechnology Center Dresden, 01307 Dresden, Germany
| | - Yannis Kalaidzidis
- Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Michele Solimena
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich at the Univ. Hospital, Faculty of Medicine Carl Gustav Carus, Technische Univ. Dresden, 01307 Dresden, Germany; German Center for Diabetes Research (DZD e.V.), 85674 Neuherberg, Germany; Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
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32
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Otter S, Lammert E. Exciting Times for Pancreatic Islets: Glutamate Signaling in Endocrine Cells. Trends Endocrinol Metab 2016; 27:177-188. [PMID: 26740469 DOI: 10.1016/j.tem.2015.12.004] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 12/11/2015] [Accepted: 12/14/2015] [Indexed: 01/14/2023]
Abstract
Glutamate represents a key excitatory neurotransmitter in the central nervous system, and also modulates the function and viability of endocrine cells in pancreatic islets. In insulin-secreting beta cells, glutamate acts as an intracellular messenger, and its transport into secretory granules promotes glucose- and incretin-stimulated insulin secretion. Mitochondrial degradation of glutamate also contributes to insulin release when glutamate dehydrogenase is allosterically activated. It also signals extracellularly via glutamate receptors (AMPA and NMDA receptors) to modulate glucagon, insulin and somatostatin secretion, and islet cell survival. Its degradation products, GABA and γ-hydroxybutyrate, are released and also influence islet cell behavior. Thus, islet glutamate receptors, such as the NMDA receptors, might serve as possible drug targets to develop new medications for adjunct treatment of diabetes.
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Affiliation(s)
- Silke Otter
- Institute of Metabolic Physiology, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany; Institute for Beta Cell Biology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, and German Center for Diabetes Research (DZD e.V.), Düsseldorf, Germany
| | - Eckhard Lammert
- Institute of Metabolic Physiology, Heinrich-Heine-University Düsseldorf, 40225 Düsseldorf, Germany; Institute for Beta Cell Biology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, and German Center for Diabetes Research (DZD e.V.), Düsseldorf, Germany.
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33
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Hodik M, Skog O, Lukinius A, Isaza-Correa JM, Kuipers J, Giepmans BNG, Frisk G. Enterovirus infection of human islets of Langerhans affects β-cell function resulting in disintegrated islets, decreased glucose stimulated insulin secretion and loss of Golgi structure. BMJ Open Diabetes Res Care 2016; 4:e000179. [PMID: 27547409 PMCID: PMC4985798 DOI: 10.1136/bmjdrc-2015-000179] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 04/27/2016] [Accepted: 05/02/2016] [Indexed: 12/16/2022] Open
Abstract
AIMS/HYPOTHESIS In type 1 diabetes (T1D), most insulin-producing β cells are destroyed, but the trigger is unknown. One of the possible triggers is a virus infection and the aim of this study was to test if enterovirus infection affects glucose stimulated insulin secretion and the effect of virus replication on cellular macromolecules and organelles involved in insulin secretion. METHODS Isolated human islets were infected with different strains of coxsackievirus B (CVB) virus and the glucose-stimulated insulin release (GSIS) was measured in a dynamic perifusion system. Classical morphological electron microscopy, large-scale electron microscopy, so-called nanotomy, and immunohistochemistry were used to study to what extent virus-infected β cells contained insulin, and real-time PCR was used to analyze virus induced changes of islet specific genes. RESULTS In islets infected with CVB, GSIS was reduced in correlation with the degree of virus-induced islet disintegration. The expression of the gene encoding insulin was decreased in infected islets, whereas the expression of glucagon was not affected. Also, in islets that were somewhat disintegrated, there were uninfected β cells. Ultrastructural analysis revealed that virus particles and virus replication complexes were only present in β cells. There was a significant number of insulin granules remaining in the virus-infected β cells, despite decreased expression of insulin mRNA. In addition, no typical Golgi apparatus was detected in these cells. Exposure of islets to synthetic dsRNA potentiated glucose-stimulated insulin secretion. CONCLUSIONS/INTERPRETATION Glucose-stimulated insulin secretion; organelles involved in insulin secretion and gene expression were all affected by CVB replication in β cells.
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Affiliation(s)
- M Hodik
- Department of Immunology, Genetics and Pathology, The Rudbeck Laboratory, Uppsala University, Uppsala, Sweden
| | - O Skog
- Department of Immunology, Genetics and Pathology, The Rudbeck Laboratory, Uppsala University, Uppsala, Sweden
| | - A Lukinius
- Department of Immunology, Genetics and Pathology, The Rudbeck Laboratory, Uppsala University, Uppsala, Sweden
| | - J M Isaza-Correa
- Department of Cell Biology, University Medical Center Groningen, University Groningen, Groningen, The Netherlands
| | - J Kuipers
- Department of Cell Biology, University Medical Center Groningen, University Groningen, Groningen, The Netherlands
| | - B N G Giepmans
- Department of Cell Biology, University Medical Center Groningen, University Groningen, Groningen, The Netherlands
| | - G Frisk
- Department of Immunology, Genetics and Pathology, The Rudbeck Laboratory, Uppsala University, Uppsala, Sweden
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Shomorony A, Pfeifer CR, Aronova MA, Zhang G, Cai T, Xu H, Notkins AL, Leapman RD. Combining quantitative 2D and 3D image analysis in the serial block face SEM: application to secretory organelles of pancreatic islet cells. J Microsc 2015; 259:155-164. [PMID: 26139222 PMCID: PMC4515433 DOI: 10.1111/jmi.12276] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 05/19/2015] [Indexed: 01/08/2023]
Abstract
A combination of two-dimensional (2D) and three-dimensional (3D) analyses of tissue volume ultrastructure acquired by serial block face scanning electron microscopy can greatly shorten the time required to obtain quantitative information from big data sets that contain many billions of voxels. Thus, to analyse the number of organelles of a specific type, or the total volume enclosed by a population of organelles within a cell, it is possible to estimate the number density or volume fraction of that organelle using a stereological approach to analyse randomly selected 2D block face views through the cells, and to combine such estimates with precise measurement of 3D cell volumes by delineating the plasma membrane in successive block face images. The validity of such an approach can be easily tested since the entire 3D tissue volume is available in the serial block face scanning electron microscopy data set. We have applied this hybrid 3D/2D technique to determine the number of secretory granules in the endocrine α and β cells of mouse pancreatic islets of Langerhans, and have been able to estimate the total insulin content of a β cell.
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Affiliation(s)
- A Shomorony
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - C R Pfeifer
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - M A Aronova
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - G Zhang
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - T Cai
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - H Xu
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - A L Notkins
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - R D Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, U.S.A
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35
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Ilegems E, van Krieken PP, Edlund PK, Dicker A, Alanentalo T, Eriksson M, Mandic S, Ahlgren U, Berggren PO. Light scattering as an intrinsic indicator for pancreatic islet cell mass and secretion. Sci Rep 2015; 5:10740. [PMID: 26030284 PMCID: PMC5377231 DOI: 10.1038/srep10740] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 04/27/2015] [Indexed: 12/23/2022] Open
Abstract
The pancreatic islet of Langerhans is composed of endocrine cells producing and releasing hormones from secretory granules in response to various stimuli for maintenance of blood glucose homeostasis. In order to adapt to a variation in functional demands, these islets are capable of modulating their hormone secretion by increasing the number of endocrine cells as well as the functional response of individual cells. A failure in adaptive mechanisms will lead to inadequate blood glucose regulation and thereby to the development of diabetes. It is therefore necessary to develop tools for the assessment of both pancreatic islet mass and function, with the aim of understanding cellular regulatory mechanisms and factors guiding islet plasticity. Although most of the existing techniques rely on the use of artificial indicators, we present an imaging methodology based on intrinsic optical properties originating from mature insulin secretory granules within endocrine cells that reveals both pancreatic islet mass and function. We demonstrate the advantage of using this imaging strategy by monitoring in vivo scattering signal from pancreatic islets engrafted into the anterior chamber of the mouse eye, and how this versatile and noninvasive methodology permits the characterization of islet morphology and plasticity as well as hormone secretory status.
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Affiliation(s)
- E Ilegems
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, Stockholm SE-171 76, Sweden
| | - P P van Krieken
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, Stockholm SE-171 76, Sweden
| | - P K Edlund
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, Stockholm SE-171 76, Sweden
| | - A Dicker
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, Stockholm SE-171 76, Sweden
| | - T Alanentalo
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, Stockholm SE-171 76, Sweden
| | - M Eriksson
- Umeå Centre for Molecular Medicine, Umeå University, Umeå, Sweden
| | - S Mandic
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, Stockholm SE-171 76, Sweden
| | - U Ahlgren
- Umeå Centre for Molecular Medicine, Umeå University, Umeå, Sweden
| | - P-O Berggren
- 1] The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, Stockholm SE-171 76, Sweden [2] Diabetes Research Institute, Miller School of Medicine, University of Miami, FL 33136, Miami [3] Lee Kong Chian School of Medicine, Nanyang Technological University, Imperial College London, Novena Campus, Singapore
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36
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Dehghany J, Hoboth P, Ivanova A, Mziaut H, Müller A, Kalaidzidis Y, Solimena M, Meyer-Hermann M. A Spatial Model of Insulin-Granule Dynamics in Pancreatic β-Cells. Traffic 2015; 16:797-813. [DOI: 10.1111/tra.12286] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 03/18/2015] [Accepted: 03/20/2015] [Indexed: 01/19/2023]
Affiliation(s)
- Jaber Dehghany
- Department of Systems Immunology and Braunschweig Integrated Centre of Systems Biology; Helmholtz Centre for Infection Research; Braunschweig Germany
| | - Peter Hoboth
- Paul Langerhans Institute Dresden of Helmholtz Centre Munich at University Clinic Carl Gustav Carus of TU Dresden and Faculty of Medicine; Technische Universität Dresden; Dresden Germany
- German Center for Diabetes Research (DZD e.V.); Neuherberg Germany
| | - Anna Ivanova
- Paul Langerhans Institute Dresden of Helmholtz Centre Munich at University Clinic Carl Gustav Carus of TU Dresden and Faculty of Medicine; Technische Universität Dresden; Dresden Germany
- German Center for Diabetes Research (DZD e.V.); Neuherberg Germany
| | - Hassan Mziaut
- Paul Langerhans Institute Dresden of Helmholtz Centre Munich at University Clinic Carl Gustav Carus of TU Dresden and Faculty of Medicine; Technische Universität Dresden; Dresden Germany
- German Center for Diabetes Research (DZD e.V.); Neuherberg Germany
| | - Andreas Müller
- Paul Langerhans Institute Dresden of Helmholtz Centre Munich at University Clinic Carl Gustav Carus of TU Dresden and Faculty of Medicine; Technische Universität Dresden; Dresden Germany
- German Center for Diabetes Research (DZD e.V.); Neuherberg Germany
| | - Yannis Kalaidzidis
- Max Planck Institute of Molecular Cell Biology and Genetics; Dresden Germany
- Faculty of Bioengineering and Bioinformatics; Moscow State University; Moscow Russia
| | - Michele Solimena
- Paul Langerhans Institute Dresden of Helmholtz Centre Munich at University Clinic Carl Gustav Carus of TU Dresden and Faculty of Medicine; Technische Universität Dresden; Dresden Germany
- German Center for Diabetes Research (DZD e.V.); Neuherberg Germany
- Max Planck Institute of Molecular Cell Biology and Genetics; Dresden Germany
| | - Michael Meyer-Hermann
- Department of Systems Immunology and Braunschweig Integrated Centre of Systems Biology; Helmholtz Centre for Infection Research; Braunschweig Germany
- Institute for Biochemistry, Biotechnology and Bioinformatics; Technische Universität Braunschweig; Braunschweig Germany
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37
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Pancreatic β-cell identity, glucose sensing and the control of insulin secretion. Biochem J 2015; 466:203-18. [PMID: 25697093 DOI: 10.1042/bj20141384] [Citation(s) in RCA: 251] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Insulin release from pancreatic β-cells is required to maintain normal glucose homoeostasis in man and many other animals. Defective insulin secretion underlies all forms of diabetes mellitus, a disease currently reaching epidemic proportions worldwide. Although the destruction of β-cells is responsible for Type 1 diabetes (T1D), both lowered β-cell mass and loss of secretory function are implicated in Type 2 diabetes (T2D). Emerging results suggest that a functional deficiency, involving de-differentiation of the mature β-cell towards a more progenitor-like state, may be an important driver for impaired secretion in T2D. Conversely, at least in rodents, reprogramming of islet non-β to β-cells appears to occur spontaneously in models of T1D, and may occur in man. In the present paper, we summarize the biochemical properties which define the 'identity' of the mature β-cell as a glucose sensor par excellence. In particular, we discuss the importance of suppressing a group of 11 'disallowed' housekeeping genes, including Ldha and the monocarboxylate transporter Mct1 (Slc16a1), for normal nutrient sensing. We then survey the changes in the expression and/or activity of β-cell-enriched transcription factors, including FOXO1, PDX1, NKX6.1, MAFA and RFX6, as well as non-coding RNAs, which may contribute to β-cell de-differentiation and functional impairment in T2D. The relevance of these observations for the development of new approaches to treat T1D and T2D is considered.
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Aged insulin granules display reduced microtubule-dependent mobility and are disposed within actin-positive multigranular bodies. Proc Natl Acad Sci U S A 2015; 112:E667-76. [PMID: 25646459 DOI: 10.1073/pnas.1409542112] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Insulin secretion is key for glucose homeostasis. Insulin secretory granules (SGs) exist in different functional pools, with young SGs being more mobile and preferentially secreted. However, the principles governing the mobility of age-distinct SGs remain undefined. Using the time-reporter insulin-SNAP to track age-distinct SGs we now show that their dynamics can be classified into three components: highly dynamic, restricted, and nearly immobile. Young SGs display all three components, whereas old SGs are either restricted or nearly immobile. Both glucose stimulation and F-actin depolymerization recruit a fraction of nearly immobile young, but not old, SGs for highly dynamic, microtubule-dependent transport. Moreover, F-actin marks multigranular bodies/lysosomes containing aged SGs. These data demonstrate that SGs lose their responsiveness to glucose stimulation and competence for microtubule-mediated transport over time while changing their relationship with F-actin.
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Distribution Profile of Inositol 1,4,5-Trisphosphate Receptor/Ca2+ Channels in α and β Cells of Pancreas: Dominant Localization in Secretory Granules and Common Error in Identification of Secretory Granule Membranes. Pancreas 2015; 44:158-65. [PMID: 25222134 DOI: 10.1097/mpa.0000000000000224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES The α and β cells of pancreatic islet release important hormones in response to intracellular Ca increases that result from Ca releases through the inositol 1,4,5-trisphoshate receptor (IP3R)/Ca channels. Yet no systematic studies on distribution of IP3R/Ca channels have been done, prompting us to investigate the distribution of all 3 IP3R isoforms. METHODS Immunogold electron microscopy was performed to determine the presence and the relative concentrations of all 3 IP3R isoforms in 2 major organelles secretory granules (SGs) and the endoplasmic reticulum of α and β cells of rat pancreas. RESULTS All 3 IP3R isoforms were present in SG membranes of both cells, and the IP3R concentrations in SGs were ∼2-fold higher than those in the endoplasmic reticulum. Moreover, large halos shown in the electron microscope images of insulin-containing SGs of β cells were gap spaces that resulted from separation of granule membranes from the surrounding cytoplasm. CONCLUSIONS These results strongly suggest the important roles of SGs in IP3-induced, Ca-dependent regulatory secretory pathway in pancreas. Moreover, the accurate location of SG membranes of β cells was further confirmed by the location of another integral membrane protein synaptotagmin V and of membrane phospholipid PI(4,5)P2.
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Pfeifer CR, Shomorony A, Aronova MA, Zhang G, Cai T, Xu H, Notkins AL, Leapman RD. Quantitative analysis of mouse pancreatic islet architecture by serial block-face SEM. J Struct Biol 2015; 189:44-52. [PMID: 25448885 PMCID: PMC4305430 DOI: 10.1016/j.jsb.2014.10.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 10/24/2014] [Accepted: 10/30/2014] [Indexed: 11/24/2022]
Abstract
We have applied serial block-face scanning electron microscopy (SBF-SEM) to measure parameters that describe the architecture of pancreatic islets of Langerhans, microscopic endocrine organs that secrete insulin and glucagon for control of blood glucose. By analyzing entire mouse islets, we show that it is possible to determine (1) the distributions of alpha and beta cells, (2) the organization of blood vessels and pericapillary spaces, and (3) the ultrastructure of the individual secretory cells. Our results show that the average volume of a beta cell is nearly twice that of an alpha cell, and the total mitochondrial volume is about four times larger. In contrast, nuclear volumes in the two cell types are found to be approximately equal. Although the cores of alpha and beta secretory granules have similar diameters, the beta granules have prominent halos resulting in overall diameters that are twice those of alpha granules. Visualization of the blood vessels revealed that every secretory cell in the islet is in contact with the pericapillary space, with an average contact area of 9±5% of the cell surface area. Our data show that consistent results can be obtained by analyzing small numbers of islets. Due to the complicated architecture of pancreatic islets, such precision cannot easily be achieved by using TEM of thin sections.
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Affiliation(s)
- C R Pfeifer
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
| | - A Shomorony
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
| | - M A Aronova
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
| | - G Zhang
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
| | - T Cai
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20854, USA
| | - H Xu
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20854, USA
| | - A L Notkins
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20854, USA
| | - R D Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20854, USA
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Nam D, Mantell J, Bull D, Verkade P, Achim A. A novel framework for segmentation of secretory granules in electron micrographs. Med Image Anal 2014; 18:411-24. [PMID: 24444668 DOI: 10.1016/j.media.2013.12.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Revised: 12/18/2013] [Accepted: 12/18/2013] [Indexed: 10/25/2022]
Abstract
It is still a standard practice for biologists to manually analyze transmission electron microscopy images. This is not only time consuming but also not reproducible and prone to induce subjective bias. For large-scale studies of insulin granules inside beta cells of the islet of Langerhans, an automated method for analysis is essential. Due to the complex structure of the images, standard microscopy segmentation techniques cannot be applied. We present a new approach to segment and measure transmission electron microscopy images of insulin granule cores and membranes from beta cells of rat islets of Langerhans. The algorithm is separated into two broad components, core segmentation and membrane segmentation. Core segmentation proceeds through three steps: pre-segmentation using a novel level-set active contour, morphological cleaning and a refining segmentation on each granule using a novel dual level-set active contour. Membrane segmentation is achieved in four steps: morphological cleaning, membrane sampling and scaling, vector field convolution for gap filling and membrane verification using a novel convergence filter. We show results from our algorithm alongside popular microscopy segmentation methods; the advantages of our method are demonstrated. Our algorithm is validated by comparing automated results to a manually defined ground truth. When the number of granules detected is compared to the number of granules in the ground truth a precision of 91% and recall of 87% is observed. The average granule areas differ by 13.35% and 6.08% for core and membranes respectively, when compared to the average areas of the ground truth. These results compare favorably to previously published data.
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Affiliation(s)
- David Nam
- Visual Information Laboratory, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
| | - Judith Mantell
- Wolfson Bioimaging Facility, University of Bristol, Medical Sciences, University Walk, Bristol BS8 1TD, UK; School of Biochemistry, University of Bristol, Medical Sciences, University Walk, Bristol BS8 1TD, UK.
| | - David Bull
- Visual Information Laboratory, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
| | - Paul Verkade
- Wolfson Bioimaging Facility, University of Bristol, Medical Sciences, University Walk, Bristol BS8 1TD, UK; School of Biochemistry, University of Bristol, Medical Sciences, University Walk, Bristol BS8 1TD, UK; School of Physiology and Pharmacology, University of Bristol, Medical Sciences, University Walk, Bristol BS8 1TD, UK.
| | - Alin Achim
- Visual Information Laboratory, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
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Liu M, Wright J, Guo H, Xiong Y, Arvan P. Proinsulin entry and transit through the endoplasmic reticulum in pancreatic beta cells. VITAMINS AND HORMONES 2014; 95:35-62. [PMID: 24559913 DOI: 10.1016/b978-0-12-800174-5.00002-8] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Insulin is an essential hormone for maintaining metabolic homeostasis in the body. To make fully bioactive insulin, pancreatic beta cells initiate synthesis of the insulin precursor, preproinsulin, at the cytosolic side of the endoplasmic reticulum (ER), whereupon it undergoes co- and post-translational translocation across the ER membrane. Preproinsulin is cleaved by signal peptidase to form proinsulin that folds on the luminal side of the ER, forming three evolutionarily conserved disulfide bonds. Properly folded proinsulin forms dimers and exits from the ER, trafficking through Golgi complex into immature secretory granules wherein C-peptide is endoproteolytically excised, allowing fully bioactive two-chain insulin to ultimately be stored in mature granules for insulin secretion. Although insulin biosynthesis has been intensely studied in recent decades, the earliest events, including proinsulin entry and exit from the ER, have been relatively understudied. However, over the past 5 years, more than 20 new insulin gene mutations have been reported to cause a new syndrome termed Mutant INS-gene-induced Diabetes of Youth (MIDY). Although these mutants have not been completely characterized, most of them affect proinsulin entry and exit from the ER. Here, we summarize our current knowledge about the early events of insulin biosynthesis and review recent advances in understanding how defects in these events may lead to pancreatic beta cell failure.
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Affiliation(s)
- Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA; Department of Metabolism, Tianjin Medical University General Hospital, Tianjin, PR China.
| | - Jordan Wright
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Huan Guo
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Yi Xiong
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, The University of Michigan Medical School, Ann Arbor, Michigan, USA.
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Zhou Y, Waanders LF, Holmseth S, Guo C, Berger UV, Li Y, Lehre AC, Lehre KP, Danbolt NC. Proteome analysis and conditional deletion of the EAAT2 glutamate transporter provide evidence against a role of EAAT2 in pancreatic insulin secretion in mice. J Biol Chem 2013; 289:1329-44. [PMID: 24280215 DOI: 10.1074/jbc.m113.529065] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Islet function is incompletely understood in part because key steps in glutamate handling remain undetermined. The glutamate (excitatory amino acid) transporter 2 (EAAT2; Slc1a2) has been hypothesized to (a) provide islet cells with glutamate, (b) protect islet cells against high extracellular glutamate concentrations, (c) mediate glutamate release, or (d) control the pH inside insulin secretory granules. Here we floxed the EAAT2 gene to produce the first conditional EAAT2 knock-out mice. Crossing with Nestin-cyclization recombinase (Cre) eliminated EAAT2 from the brain, resulting in epilepsy and premature death, confirming the importance of EAAT2 for brain function and validating the genetic construction. Crossing with insulin-Cre lines (RIP-Cre and IPF1-Cre) to obtain pancreas-selective deletion did not appear to affect survival, growth, glucose tolerance, or β-cell number. We found (using TaqMan RT-PCR, immunoblotting, immunocytochemistry, and proteome analysis) that the EAAT2 levels were too low to support any of the four hypothesized functions. The proteome analysis detected more than 7,000 islet proteins of which more than 100 were transporters. Although mitochondrial glutamate transporters and transporters for neutral amino acids were present at high levels, all other transporters with known ability to transport glutamate were strikingly absent. Glutamate-metabolizing enzymes were abundant. The level of glutamine synthetase was 2 orders of magnitude higher than that of glutaminase. Taken together this suggests that the uptake of glutamate by islets from the extracellular fluid is insignificant and that glutamate is intracellularly produced. Glutamine synthetase may be more important for islets than assumed previously.
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Affiliation(s)
- Yun Zhou
- From The Neurotransporter Group, Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway
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Regulation of β-cell function by RNA-binding proteins. Mol Metab 2013; 2:348-55. [PMID: 24327951 DOI: 10.1016/j.molmet.2013.09.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 09/15/2013] [Accepted: 09/16/2013] [Indexed: 02/05/2023] Open
Abstract
β-cells of the pancreatic islets are highly specialized and high-throughput units for the production of insulin, the key hormone for maintenance of glucose homeostasis. Elevation of extracellular glucose and/or GLP-1 levels triggers a rapid upregulation of insulin biosynthesis through the activation of post-transcriptional mechanisms. RNA-binding proteins are emerging as key factors in the regulation of these mechanisms as well as in other aspects of β-cell function and glucose homeostasis at large, and thus may be implicated in the pathogenesis of diabetes. Here we review current research in the field, with a major emphasis on RNA-binding proteins that control biosynthesis of insulin and other components of the insulin secretory granules by modulating the stability and translation of their mRNAs.
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Abstract
Secretory granule biogenesis is a pivotal process for regulated release of hormones and neurotransmitters. A prominent example is the pancreatic β cell that secretes insulin, a major anabolic hormone controlling cellular metabolism upon nutrient availability. We recently described a checkpoint mechanism that halts scission of nascent secretory granules at the trans-Golgi network (TGN) until complete loading of insulin is achieved. We demonstrated that the Bin/Amphiphysin/Rvs (BAR) domain-containing protein Arfaptin-1 prevents granule scission until it is phosphorylated by Protein Kinase D (PKD). Arfaptin-1 phosphorylation releases its binding to ADP-rybosylation factor (ARF) allowing scission to occur. Lack of this control mechanism in β cells resulted in premature scission, generation of dysfunctional insulin granules and impaired regulated insulin secretion without affecting constitutive release of other transport carriers. Here we discuss two important questions related to this work: How might completion of granule loading be sensed by PKD, and how does Arfaptin-1 specifically regulate insulin granule formation in beta cells?
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Affiliation(s)
- Helmuth Gehart
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire); INSERM; CNRS; Université de Strasbourg; Illkirch, France ; Institute of Cell Biology; ETH Zurich; Zurich, Switzerland
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Lipovšek S, Janžekovič F, Leitinger G, Rupnik MS. Rab3a ablation related changes in morphology of secretory vesicles in major endocrine pancreatic cells, pituitary melanotroph cells and adrenal gland chromaffin cells in mice. Gen Comp Endocrinol 2013; 185:67-79. [PMID: 23399968 DOI: 10.1016/j.ygcen.2013.01.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 01/02/2013] [Accepted: 01/09/2013] [Indexed: 01/21/2023]
Abstract
In this work we have compared the ultrastructural characteristics of major pancreatic endocrine cells, pituitary melanotrophs and adrenal chromaffin cells in the normal mouse strain (wild type, WT) and mice with a known secretory deficit, the Rab3a knockout strain (Rab3a KO). For this purpose, pancreata, pituitary glands and adrenal glands from the Rab3a KO and from the WT mice were analysed, using conventional transmission electron microscopy (TEM). In order to assess the significance of the presence of Rab3a proteins in the relevant cells, we focused primarily on their secretory vesicle morphology and distribution. Our results showed a comparable general morphology in Rab3a KO and WT in all assessed endocrine cell types. In all studied cell types, the distribution of secretory granules along the plasma membrane (number of docked and almost-docked vesicles) was comparable between Rab3a KO and WT mice. Specific differences were found in the diameters of their secretory vesicles, diameters of their electron-dense cores and the presence of autophagic structures in the cells of Rab3A KO mice only. Occasionally, individual electron-dense round vesicles were present inside autophagosome-like structures; these were possibly secretory vesicles or their remnants. The differences found in the diameters of the secretory vesicles confirm the key role of Rab3a proteins in controlling the balance between secretory vesicle biogenesis and degradation, and suggest that the ablation of this protein probably changes the nature of the reservoir of secretory vesicles available for regulated exocytosis.
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Affiliation(s)
- Saška Lipovšek
- Institute of Physiology, Faculty of Medicine, University of Maribor, Slomškov trg 15, SI-2000 Maribor, Slovenia.
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Nam D, Mantell J, Bull D, Verkade P, Achim A. Active contour based segmentation for insulin granule cores in electron micrographs of beta islet cells. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2012:5339-42. [PMID: 23367135 DOI: 10.1109/embc.2012.6347200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Transmission electron microscopy images of beta islet cells contain many complex structures, making it difficult to accurately segment insulin granule cores. Quantification of sub cellular structures will allow biologists to better understand cellular mechanics. Two novel, level set active contour models are presented in this paper. The first utilizes a shape regularizer to reduce oversegmentation. The second contribution is a dual active contour, which achieves accurate core segmentations. The segmentation algorithm proceeds through three stages: an initial rough segmentation using the first contribution, cleaning using morphological techniques and a refining step using the proposed dual active contour. Our method is validated on a set of manually defined ground truths.
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Affiliation(s)
- David Nam
- Visual Information Laboratory, University of Bristol, Bristol, UK
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Masini M, Marselli L, Bugliani M, Martino L, Masiello P, Marchetti P, De Tata V. Ultrastructural morphometric analysis of insulin secretory granules in human type 2 diabetes. Acta Diabetol 2012. [PMID: 23184237 DOI: 10.1007/s00592-012-0446-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We performed an ultrastructural morphometric analysis of insulin secretory granules in pancreatic beta cells from control and type 2 diabetic multiorgan donors. The volume density of insulin granules significantly (p < 0.05) reduced in beta cells from type 2 diabetic patients with respect to non-diabetic subjects, and this reduction was mainly attributable to a decrease in mature granules. On the contrary, no significant difference was observed in the volume density of docked granules between controls and type 2 diabetic patients. In addition, there was a significant positive correlation between the density volume of total insulin granules and stimulated insulin secretion in non-diabetic islets. In conclusion, we detected significant changes in the intracellular distribution of insulin secretory granules within the beta cell that might be related with the alterations in insulin secretion observed in type 2 diabetes patients.
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Affiliation(s)
- Matilde Masini
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Via Roma 55, Scuola Medica, 56126 Pisa, Italy
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Rajagopal C, Mains RE, Eipper BA. Signaling from the secretory granule to the nucleus. Crit Rev Biochem Mol Biol 2012; 47:391-406. [PMID: 22681236 DOI: 10.3109/10409238.2012.694845] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Neurons and endocrine cells use a complex array of signaling molecules to communicate with each other and with various targets. The majority of these signaling molecules are stored in specialized organelles awaiting release on demand: 40-60 nm vesicles carry conventional or small molecule neurotransmitters, and 200-400 nm granules contain bioactive peptides. The supply of small molecule neurotransmitters is tightly regulated by local feedback of synthetic rates and transport processes at sites of release. The larger granules that contain bioactive peptides present the secretory cell with special challenges, as the peptide precursors are inserted into the lumen of the secretory pathway in the cell soma and undergo biosynthetic processing while being transported to distant sites for eventual secretion. One solution to this dilemma in information handling has been to employ proteolytic cleavage of secretory granule membrane proteins to produce cytosolic fragments that can signal to the nucleus, affecting gene expression. The use of regulated intramembrane proteolysis to signal from secretory granules to the nucleus is compared to its much better understood role in relaying information from the endoplasmic reticulum by SREBP and ATF6 and from the plasma membrane by cadherins, Notch and ErbB4.
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Affiliation(s)
- Chitra Rajagopal
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT, USA
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