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Klingelhuber F, Frendo-Cumbo S, Omar-Hmeadi M, Massier L, Kakimoto P, Taylor AJ, Couchet M, Ribicic S, Wabitsch M, Messias AC, Iuso A, Müller TD, Rydén M, Mejhert N, Krahmer N. A spatiotemporal proteomic map of human adipogenesis. Nat Metab 2024:10.1038/s42255-024-01025-8. [PMID: 38565923 DOI: 10.1038/s42255-024-01025-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 03/07/2024] [Indexed: 04/04/2024]
Abstract
White adipocytes function as major energy reservoirs in humans by storing substantial amounts of triglycerides, and their dysfunction is associated with metabolic disorders; however, the mechanisms underlying cellular specialization during adipogenesis remain unknown. Here, we generate a spatiotemporal proteomic atlas of human adipogenesis, which elucidates cellular remodelling as well as the spatial reorganization of metabolic pathways to optimize cells for lipid accumulation and highlights the coordinated regulation of protein localization and abundance during adipocyte formation. We identify compartment-specific regulation of protein levels and localization changes of metabolic enzymes to reprogramme branched-chain amino acids and one-carbon metabolism to provide building blocks and reduction equivalents. Additionally, we identify C19orf12 as a differentiation-induced adipocyte lipid droplet protein that interacts with the translocase of the outer membrane complex of lipid droplet-associated mitochondria and regulates adipocyte lipid storage by determining the capacity of mitochondria to metabolize fatty acids. Overall, our study provides a comprehensive resource for understanding human adipogenesis and for future discoveries in the field.
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Affiliation(s)
- Felix Klingelhuber
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Scott Frendo-Cumbo
- Department of Medicine (H7), Karolinska Institutet, Huddinge, Stockholm, Sweden
| | - Muhmmad Omar-Hmeadi
- Department of Medicine (H7), Karolinska Institutet, Huddinge, Stockholm, Sweden
| | - Lucas Massier
- Department of Medicine (H7), Karolinska Institutet, Huddinge, Stockholm, Sweden
| | - Pamela Kakimoto
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Austin J Taylor
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Morgane Couchet
- Department of Medicine (H7), Karolinska Institutet, Huddinge, Stockholm, Sweden
| | - Sara Ribicic
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Martin Wabitsch
- Center for Rare Endocrine Diseases, Division of Paediatric Endocrinology and Diabetes, Department of Paediatrics and Adolescent Medicine, Ulm University Medical Centre, Ulm, Germany
| | - Ana C Messias
- Institute of Structural Biology, Molecular Targets and Therapeutics Center, Helmholtz Zentrum München, Neuherberg, Germany
- Bavarian NMR Centre, Department of Bioscience, School of Natural Sciences, Technical University of Munich, Garching, Germany
| | - Arcangela Iuso
- Institute of Neurogenomics, Helmholtz Zentrum München, Neuherberg, Germany
- Institute of Human Genetics, Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany
| | - Timo D Müller
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Walther-Straub Institute for Pharmacology and Toxicology, Ludwig-Maximilians-University Munich (LMU), Munich, Germany
| | - Mikael Rydén
- Department of Medicine (H7), Karolinska Institutet, Huddinge, Stockholm, Sweden
- Endocrinology unit, Karolinska University Hospital, Huddinge, Stockholm, Sweden
| | - Niklas Mejhert
- Department of Medicine (H7), Karolinska Institutet, Huddinge, Stockholm, Sweden
| | - Natalie Krahmer
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Neuherberg, Germany.
- German Center for Diabetes Research (DZD), Neuherberg, Germany.
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2
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Ludzki AC, Hansen M, Zareifi D, Jalkanen J, Huang Z, Omar-Hmeadi M, Renzi G, Klingelhuber F, Boland S, Ambaw YA, Wang N, Damdimopoulos A, Liu J, Jernberg T, Petrus P, Arner P, Krahmer N, Fan R, Treuter E, Gao H, Rydén M, Mejhert N. Transcriptional determinants of lipid mobilization in human adipocytes. Sci Adv 2024; 10:eadi2689. [PMID: 38170777 PMCID: PMC10776019 DOI: 10.1126/sciadv.adi2689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 12/01/2023] [Indexed: 01/05/2024]
Abstract
Defects in adipocyte lipolysis drive multiple aspects of cardiometabolic disease, but the transcriptional framework controlling this process has not been established. To address this, we performed a targeted perturbation screen in primary human adipocytes. Our analyses identified 37 transcriptional regulators of lipid mobilization, which we classified as (i) transcription factors, (ii) histone chaperones, and (iii) mRNA processing proteins. On the basis of its strong relationship with multiple readouts of lipolysis in patient samples, we performed mechanistic studies on one hit, ZNF189, which encodes the zinc finger protein 189. Using mass spectrometry and chromatin profiling techniques, we show that ZNF189 interacts with the tripartite motif family member TRIM28 and represses the transcription of an adipocyte-specific isoform of phosphodiesterase 1B (PDE1B2). The regulation of lipid mobilization by ZNF189 requires PDE1B2, and the overexpression of PDE1B2 is sufficient to attenuate hormone-stimulated lipolysis. Thus, our work identifies the ZNF189-PDE1B2 axis as a determinant of human adipocyte lipolysis and highlights a link between chromatin architecture and lipid mobilization.
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Affiliation(s)
- Alison C. Ludzki
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Mattias Hansen
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Danae Zareifi
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Jutta Jalkanen
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Zhiqiang Huang
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, SE-141 83 Stockholm, Sweden
| | - Muhmmad Omar-Hmeadi
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Gianluca Renzi
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Felix Klingelhuber
- Institute for Diabetes and Obesity, Helmholtz Center Munich, Neuherberg, Germany
- Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Sebastian Boland
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public Health, Boston, MA, USA
| | - Yohannes A. Ambaw
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public Health, Boston, MA, USA
- Department of Cell Biology, Memorial Sloan Kettering Cancer Center (MSKCC), New York, NY, USA
| | - Na Wang
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Anastasios Damdimopoulos
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, SE-141 83 Stockholm, Sweden
| | - Jianping Liu
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Tomas Jernberg
- Department of Clinical Sciences, Karolinska Institutet, Danderyd Hospital, SE-182 88 Stockholm, Sweden
| | - Paul Petrus
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Peter Arner
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Natalie Krahmer
- Institute for Diabetes and Obesity, Helmholtz Center Munich, Neuherberg, Germany
- Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Rongrong Fan
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, SE-141 83 Stockholm, Sweden
| | - Eckardt Treuter
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, SE-141 83 Stockholm, Sweden
| | - Hui Gao
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, SE-141 83 Stockholm, Sweden
| | - Mikael Rydén
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
| | - Niklas Mejhert
- Department of Medicine Huddinge, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-141 86 Stockholm, Sweden
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3
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Couchet M, Gao H, Klingelhuber F, Jalkanen J, De Castro Barbosa T, Omar-Hmeadi M, Massier L, Krahmer N, Mejhert N, Rydén M. Adipogenic characterization of immortalized CD55 + progenitor cells from human white adipose tissue. Adipocyte 2023:2283213. [PMID: 37982546 DOI: 10.1080/21623945.2023.2283213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 11/08/2023] [Indexed: 11/21/2023] Open
Abstract
BACKGROUND Mature adipocytes are notoriously difficult to study ex vivo and alternative cell culture systems have therefore been developed. One of the most common models are human adipose progenitor cells (hAPCs). Unfortunately, these display replicative senescence after prolonged culture conditions, which limits their use in mechanistic studies. METHODS Herein, we knocked in human telomerase reverse transcriptase (TERT) into the AAVS1 locus of CD55+ hAPCs derived from abdominal subcutaneous adipose tissue and characterized the cells before and after differentiation into adipocytes. RESULTS Immortalized TERT-hAPCs retained proliferative and adipogenic capacities comparable to those of early-passage wild type hAPCs for > 80 passages. In line with this, our integrative transcriptomic and proteomic analyses revealed that TERT-hAPCs displayed robust adipocyte expression profiles in comparison to wild type hAPCs. This was confirmed by functional analyses of lipid turnover where TERT-hAPCs exhibited pronounced responses to insulin and pro-lipolytic stimuli such as isoprenaline, dibutyrul cAMP and tumour necrosis factor alpha. In addition, TERT-hAPCs could be readily cultured in both standard 2D and 3D-cultures and proteomic analyses revealed that the spheroid culture conditions improved adipogenesis. CONCLUSION Through descriptive and functional studies, we demonstrate that immortalization of human CD55+ hAPCs is feasible and results in cells with stable proliferative and adipogenic capacities over multiple passages. As these cells are cryopreservable, they provide the additional advantage over primary cells of allowing repeated studies in both 2D and 3D model systems with the same genetic background. (234/250).
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Affiliation(s)
- Morgane Couchet
- Department of Medicine (H7), Karolinska Institutet, Stockholm, Sweden
| | - Hui Gao
- Department of Biosciences and Nutrition, Karolinska Institutet, Stockholm, Sweden
| | - Felix Klingelhuber
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Neuherberg, Germany
- German Center forDiabetes Research, Neuherberg, Germany
| | - Jutta Jalkanen
- Department of Medicine (H7), Karolinska Institutet, Stockholm, Sweden
| | | | | | - Lucas Massier
- Department of Medicine (H7), Karolinska Institutet, Stockholm, Sweden
| | - Natalie Krahmer
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, Neuherberg, Germany
- German Center forDiabetes Research, Neuherberg, Germany
| | - Niklas Mejhert
- Department of Medicine (H7), Karolinska Institutet, Stockholm, Sweden
| | - Mikael Rydén
- Department of Medicine (H7), Karolinska Institutet, Stockholm, Sweden
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4
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Omar-Hmeadi M, Guček A, Barg S. Local PI(4,5)P 2 signaling inhibits fusion pore expansion during exocytosis. Cell Rep 2023; 42:112036. [PMID: 36701234 DOI: 10.1016/j.celrep.2023.112036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 11/04/2022] [Accepted: 01/11/2023] [Indexed: 01/26/2023] Open
Abstract
Phosphatidylinositol(4,5)bisphosphate (PI(4,5)P2) is an important signaling phospholipid that is required for regulated exocytosis and some forms of endocytosis. The two processes share a topologically similar pore structure that connects the vesicle lumen with the outside. Widening of the fusion pore during exocytosis leads to cargo release, while its closure initiates kiss&run or cavicapture endocytosis. We show here, using live-cell total internal reflection fluorescence (TIRF) microscopy of insulin granule exocytosis, that transient accumulation of PI(4,5)P2 at the release site recruits components of the endocytic fission machinery and stalls the late fusion pore expansion that is required for peptide release. The absence of clathrin differentiates this mechanism from clathrin-mediated endocytosis. Knockdown of phosphatidylinositol-phosphate-5-kinase-1c or optogenetic recruitment of 5-phosphatase reduces PI(4,5)P2 transients and accelerates fusion pore expansion, suggesting that acute PI(4,5)P2 synthesis is involved. Thus, local phospholipid signaling inhibits fusion pore expansion and peptide release through an unconventional endocytic mechanism.
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Affiliation(s)
- Muhmmad Omar-Hmeadi
- Department of Medical Cell Biology, Uppsala University, BMC Box 571, 751 23 Uppsala, Sweden
| | - Alenka Guček
- Department of Medical Cell Biology, Uppsala University, BMC Box 571, 751 23 Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, BMC Box 571, 751 23 Uppsala, Sweden.
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5
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Omar-Hmeadi M, Liu L, Echeverry S, Barg S. Quantification of Secretory Granule Exocytosis by TIRF Imaging and Capacitance Measurements. Methods Mol Biol 2023; 2565:179-186. [PMID: 36205894 DOI: 10.1007/978-1-0716-2671-9_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Hormones and neurotransmitters are released from (neuro)endocrine cells by regulated exocytosis of secretory granules. During exocytosis, the granule membrane fuses with the plasma membrane, which allows release of the stored content into the bloodstream or the surrounding tissue. Here, we give a detailed description of two complementary methods to observe and quantify exocytosis in single cells: high-resolution TIRF microscopy and patch-clamp capacitance recordings. Precise stimulation of exocytosis is achieved by local pressure application or voltage-clamp depolarizations. While the chapter is focused on insulin-secreting cells as an accessible and disease-relevant model system, the methodology is applicable to a wide variety of secretory cells including chromaffin and PC12 cells.
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Affiliation(s)
| | - Liangwen Liu
- Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | | | - Sebastian Barg
- Medical Cell Biology, Uppsala University, Uppsala, Sweden.
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6
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Balboa D, Barsby T, Lithovius V, Saarimäki-Vire J, Omar-Hmeadi M, Dyachok O, Montaser H, Lund PE, Yang M, Ibrahim H, Näätänen A, Chandra V, Vihinen H, Jokitalo E, Kvist J, Ustinov J, Nieminen AI, Kuuluvainen E, Hietakangas V, Katajisto P, Lau J, Carlsson PO, Barg S, Tengholm A, Otonkoski T. Functional, metabolic and transcriptional maturation of human pancreatic islets derived from stem cells. Nat Biotechnol 2022; 40:1042-1055. [PMID: 35241836 PMCID: PMC9287162 DOI: 10.1038/s41587-022-01219-z] [Citation(s) in RCA: 102] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 01/11/2022] [Indexed: 12/19/2022]
Abstract
Transplantation of pancreatic islet cells derived from human pluripotent stem cells is a promising treatment for diabetes. Despite progress in the generation of stem-cell-derived islets (SC-islets), no detailed characterization of their functional properties has been conducted. Here, we generated functionally mature SC-islets using an optimized protocol and benchmarked them comprehensively against primary adult islets. Biphasic glucose-stimulated insulin secretion developed during in vitro maturation, associated with cytoarchitectural reorganization and the increasing presence of alpha cells. Electrophysiology, signaling and exocytosis of SC-islets were similar to those of adult islets. Glucose-responsive insulin secretion was achieved despite differences in glycolytic and mitochondrial glucose metabolism. Single-cell transcriptomics of SC-islets in vitro and throughout 6 months of engraftment in mice revealed a continuous maturation trajectory culminating in a transcriptional landscape closely resembling that of primary islets. Our thorough evaluation of SC-islet maturation highlights their advanced degree of functionality and supports their use in further efforts to understand and combat diabetes. Pancreatic islets derived from stem cells are benchmarked against primary cells.
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Affiliation(s)
- Diego Balboa
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Bioinformatics and Genomics Program, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Barcelona, Spain
| | - Tom Barsby
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Väinö Lithovius
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Jonna Saarimäki-Vire
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | | | - Oleg Dyachok
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Hossam Montaser
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Per-Eric Lund
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Mingyu Yang
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Hazem Ibrahim
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Anna Näätänen
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Vikash Chandra
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Helena Vihinen
- Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Jouni Kvist
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Jarkko Ustinov
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Anni I Nieminen
- Metabolomics Unit, Institute for Molecular Medicine Finland, Helsinki, Finland
| | - Emilia Kuuluvainen
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Ville Hietakangas
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.,Molecular and Integrative Bioscience Research Program, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Pekka Katajisto
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.,Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
| | - Joey Lau
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Per-Ola Carlsson
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Timo Otonkoski
- Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland. .,Children's Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland.
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7
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Omar-Hmeadi M, Lund PE, Gandasi NR, Tengholm A, Barg S. Paracrine control of α-cell glucagon exocytosis is compromised in human type-2 diabetes. Nat Commun 2020; 11:1896. [PMID: 32312960 PMCID: PMC7171169 DOI: 10.1038/s41467-020-15717-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 03/23/2020] [Indexed: 01/05/2023] Open
Abstract
Glucagon is released from pancreatic α-cells to activate pathways that raise blood glucose. Its secretion is regulated by α-cell-intrinsic glucose sensing and paracrine control through insulin and somatostatin. To understand the inadequately high glucagon levels that contribute to hyperglycemia in type-2 diabetes (T2D), we analyzed granule behavior, exocytosis and membrane excitability in α-cells of 68 non-diabetic and 21 T2D human donors. We report that exocytosis is moderately reduced in α-cells of T2D donors, without changes in voltage-dependent ion currents or granule trafficking. Dispersed α-cells have a non-physiological V-shaped dose response to glucose, with maximal exocytosis at hyperglycemia. Within intact islets, hyperglycemia instead inhibits α-cell exocytosis, but not in T2D or when paracrine inhibition by insulin or somatostatin is blocked. Surface expression of somatostatin-receptor-2 is reduced in T2D, suggesting a mechanism for the observed somatostatin resistance. Thus, elevated glucagon in human T2D may reflect α-cell insensitivity to paracrine inhibition at hyperglycemia. Glucagon is elevated Type-2 diabetes, which contributes to poor glucose control in patients with the disease. Here the authors report that secretion of the hormone is controlled by paracrine inhibition, and that resistance of α-cells to somatostatin can explain hyperglucagonemia in type-2 diabetes.
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Affiliation(s)
- Muhmmad Omar-Hmeadi
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden
| | - Per-Eric Lund
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden
| | - Nikhil R Gandasi
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden
| | - Anders Tengholm
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden
| | - Sebastian Barg
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden.
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8
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Guček A, Gandasi NR, Omar-Hmeadi M, Bakke M, Døskeland SO, Tengholm A, Barg S. Fusion pore regulation by cAMP/Epac2 controls cargo release during insulin exocytosis. eLife 2019; 8:41711. [PMID: 31099751 PMCID: PMC6557626 DOI: 10.7554/elife.41711] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 04/28/2019] [Indexed: 12/20/2022] Open
Abstract
Regulated exocytosis establishes a narrow fusion pore as initial aqueous connection to the extracellular space, through which small transmitter molecules such as ATP can exit. Co-release of polypeptides and hormones like insulin requires further expansion of the pore. There is evidence that pore expansion is regulated and can fail in diabetes and neurodegenerative disease. Here, we report that the cAMP-sensor Epac2 (Rap-GEF4) controls fusion pore behavior by acutely recruiting two pore-restricting proteins, amisyn and dynamin-1, to the exocytosis site in insulin-secreting beta-cells. cAMP elevation restricts and slows fusion pore expansion and peptide release, but not when Epac2 is inactivated pharmacologically or in Epac2-/- (Rapgef4-/-) mice. Consistently, overexpression of Epac2 impedes pore expansion. Widely used antidiabetic drugs (GLP-1 receptor agonists and sulfonylureas) activate this pathway and thereby paradoxically restrict hormone release. We conclude that Epac2/cAMP controls fusion pore expansion and thus the balance of hormone and transmitter release during insulin granule exocytosis. Insulin is the hormone that signals to the body to take up sugar from the blood. Specialized cells in the pancreas – known as β-cells – release insulin after a meal. Before that, insulin molecules are stored in tiny granules inside the β-cells; these granules must fuse with the cells’ surface membranes to release their contents. The first step in this process creates a narrow pore that allows small molecules, but not the larger insulin molecules, to seep out. The pore then widens to release the insulin. Since the small molecules are known to act locally in the pancreas, it is possible that this “molecular sieve” is biologically important. Yet it is not clear how the pore widens. One of the problems for people with type 2 diabetes is that they release less insulin into the bloodstream. Two kinds of drugs used to treat these patients work by stimulating β-cells to release their insulin. One way to achieve this is by raising the levels of a small molecule called cAMP, which is well known to help prepare insulin granules for release. The cAMP molecule also seems to slow the widening of the pore, and Gucek et al. have now investigated how this happens at a molecular level. By observing individual granules of human β-cells using a special microscope, Gucek et al. could watch how different drugs affect pore widening and content release. They also saw that cAMP activated a protein called Epac2, which then recruited two other proteins – amisyn and dynamin – to the small pores. These two proteins together then closed the pore, rather than expanding it to let insulin out. Type 2 diabetes patients sometimes have high levels of amisyn in their β-cells, which could explain why they do not release enough insulin. The microscopy experiments also revealed that two common anti-diabetic drugs activate Epac2 and prevent the pores from widening, thereby counteracting their positive effect on insulin release. The combined effect is likely a shift in the balance between insulin and the locally acting small molecules. These findings suggest that two common anti-diabetic drugs activate a common mechanism that may lead to unexpected outcomes, possibly even reducing how much insulin the β-cells can release. Future studies in mice and humans will have to investigate these effects in whole organisms.
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Affiliation(s)
- Alenka Guček
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | | | - Marit Bakke
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | | | - Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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9
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Ghiasi SM, Dahlby T, Hede Andersen C, Haataja L, Petersen S, Omar-Hmeadi M, Yang M, Pihl C, Bresson SE, Khilji MS, Klindt K, Cheta O, Perone MJ, Tyrberg B, Prats C, Barg S, Tengholm A, Arvan P, Mandrup-Poulsen T, Marzec MT. Endoplasmic Reticulum Chaperone Glucose-Regulated Protein 94 Is Essential for Proinsulin Handling. Diabetes 2019; 68:747-760. [PMID: 30670477 PMCID: PMC6425875 DOI: 10.2337/db18-0671] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 12/26/2018] [Indexed: 12/18/2022]
Abstract
Although endoplasmic reticulum (ER) chaperone binding to mutant proinsulin has been reported, the role of protein chaperones in the handling of wild-type proinsulin is underinvestigated. Here, we have explored the importance of glucose-regulated protein 94 (GRP94), a prominent ER chaperone known to fold insulin-like growth factors, in proinsulin handling within β-cells. We found that GRP94 coimmunoprecipitated with proinsulin and that inhibition of GRP94 function and/or expression reduced glucose-dependent insulin secretion, shortened proinsulin half-life, and lowered intracellular proinsulin and insulin levels. This phenotype was accompanied by post-ER proinsulin misprocessing and higher numbers of enlarged insulin granules that contained amorphic material with reduced immunogold staining for mature insulin. Insulin granule exocytosis was accelerated twofold, but the secreted insulin had diminished bioactivity. Moreover, GRP94 knockdown or knockout in β-cells selectively activated protein kinase R-like endoplasmic reticulum kinase (PERK), without increasing apoptosis levels. Finally, GRP94 mRNA was overexpressed in islets from patients with type 2 diabetes. We conclude that GRP94 is a chaperone crucial for proinsulin handling and insulin secretion.
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Affiliation(s)
- Seyed Mojtaba Ghiasi
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Tina Dahlby
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Leena Haataja
- Division of Metabolism, Endocrinology, & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
| | - Sólrun Petersen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Mingyu Yang
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Celina Pihl
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Muhammad Saad Khilji
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kristian Klindt
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Oana Cheta
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Marcelo J Perone
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET-Partner Institute of the Max Planck Society, Polo Científico Tecnológico, Buenos Aires, Argentina
| | - Björn Tyrberg
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Clara Prats
- Center for Healthy Ageing, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Peter Arvan
- Division of Metabolism, Endocrinology, & Diabetes, University of Michigan Medical Center, Ann Arbor, MI
| | | | - Michal Tomasz Marzec
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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10
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Gucek A, Gandasi NR, Omar-Hmeadi M, Bakke M, Doskeland S, Tengholm A, Barg S. Fusion Pore Regulation by EPAC2/cAMP Controls Cargo Release during Insulin Exocytosis. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.1702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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11
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Abstract
Syntaxin (stx)-1 is an integral plasma membrane protein that is crucial for two distinct steps of regulated exocytosis, docking of secretory granules at the plasma membrane and membrane fusion. During docking, stx1 clusters at the granule docking site, together with the S/M protein munc18. Here we determined features of stx1 that contribute to its clustering at granules. In live insulin-secreting cells, stx1 and stx3 (but not stx4 or stx11) accumulated at docked granules, and stx1 (but not stx4) rescued docking in cells expressing botulinum neurotoxin-C. Using a series of stx1 deletion mutants and stx1/4 chimeras, we found that all four helical domains (Ha, Hb, Hc, SNARE) and the short N-terminal peptide contribute to recruitment to granules. However, only the Hc domain confers specificity, and it must be derived from stx1 for recruitment to occur. Point mutations in the Hc or the N-terminal peptide designed to interfere with binding to munc18-1 prevent stx1 from clustering at granules, and a mutant munc18 deficient in binding to stx1 does not cluster at granules. We conclude that stx1 is recruited to the docking site in a munc18-1–bound conformation, providing a rationale for the requirement for both proteins for granule docking.
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Affiliation(s)
- Peng Yin
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Nikhil R Gandasi
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Swati Arora
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Muhmmad Omar-Hmeadi
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Jan Saras
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Sebastian Barg
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
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12
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Abstract
Phosphoinositides (PtdIns) play important roles in exocytosis and are thought to regulate secretory granule docking by co-clustering with the SNARE protein syntaxin to form a docking receptor in the plasma membrane. Here we tested this idea by high-resolution total internal reflection imaging of EGFP-labeled PtdIns markers or syntaxin-1 at secretory granule release sites in live insulin-secreting cells. In intact cells, PtdIns markers distributed evenly across the plasma membrane with no preference for granule docking sites. In contrast, syntaxin-1 was found clustered in the plasma membrane, mostly beneath docked granules. We also observed rapid accumulation of syntaxin-1 at sites where granules arrived to dock. Acute depletion of plasma membrane phosphatidylinositol (4,5) bisphosphate (PtdIns(4,5)P2 ) by recruitment of a 5'-phosphatase strongly inhibited Ca2+ -dependent exocytosis, but had no effect on docked granules or the distribution and clustering of syntaxin-1. Cell permeabilization by α-toxin or formaldehyde-fixation caused PtdIns marker to slowly cluster, in part near docked granules. In summary, our data indicate that PtdIns(4,5)P2 accelerates granule priming, but challenge a role of PtdIns in secretory granule docking or clustering of syntaxin-1 at the release site.
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Affiliation(s)
| | - Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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13
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Gandasi NR, Yin P, Omar-Hmeadi M, Ottosson Laakso E, Vikman P, Barg S. Glucose-Dependent Granule Docking Limits Insulin Secretion and Is Decreased in Human Type 2 Diabetes. Cell Metab 2018; 27:470-478.e4. [PMID: 29414688 DOI: 10.1016/j.cmet.2017.12.017] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/26/2017] [Accepted: 12/23/2017] [Indexed: 01/19/2023]
Abstract
Glucose-stimulated insulin secretion is biphasic, with a rapid first phase and a slowly developing sustained second phase; both are disturbed in type 2 diabetes (T2D). Biphasic secretion results from vastly different release probabilities of individual insulin granules, but the morphological and molecular basis for this is unclear. Here, we show that human insulin secretion and exocytosis critically depend on the availability of membrane-docked granules and that T2D is associated with a strong reduction in granule docking. Glucose accelerated granule docking, and this effect was absent in T2D. Newly docked granules only slowly acquired release competence; this was regulated by major signaling pathways, but not glucose. Gene expression analysis indicated that key proteins involved in granule docking are downregulated in T2D, and overexpression of these proteins increased granule docking. The findings establish granule docking as an important glucose-dependent step in human insulin secretion that is dysregulated in T2D.
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Affiliation(s)
- Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Peng Yin
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Muhmmad Omar-Hmeadi
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Emilia Ottosson Laakso
- Diabetes and Endocrinology Unit, Department of Clinical Sciences, Lund University Diabetes Centre, 20502 Malmö, Sweden
| | - Petter Vikman
- Diabetes and Endocrinology Unit, Department of Clinical Sciences, Lund University Diabetes Centre, 20502 Malmö, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden.
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