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Jevon D, Cottle L, Hallahan N, Harwood R, Samra JS, Gill AJ, Loudovaris T, Thomas HE, Thorn P. Capillary contact points determine beta cell polarity, control secretion and are disrupted in the db/db mouse model of diabetes. Diabetologia 2024; 67:1683-1697. [PMID: 38814445 PMCID: PMC11343897 DOI: 10.1007/s00125-024-06180-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 03/26/2024] [Indexed: 05/31/2024]
Abstract
AIMS/HYPOTHESIS Almost all beta cells contact one capillary and insulin granule fusion is targeted to this region. However, there are reports of beta cells contacting more than one capillary. We therefore set out to determine the proportion of beta cells with multiple contacts and the impact of this on cell structure and function. METHODS We used pancreatic slices in mice and humans to better maintain cell and islet structure than in isolated islets. Cell structure was assayed using immunofluorescence and 3D confocal microscopy. Live-cell two-photon microscopy was used to map granule fusion events in response to glucose stimulation. RESULTS We found that 36% and 22% of beta cells in islets from mice and humans, respectively, have separate contact with two capillaries. These contacts establish a distinct form of cell polarity with multiple basal regions. Both capillary contact points are enriched in presynaptic scaffold proteins, and both are a target for insulin granule fusion. Cells with two capillary contact points have a greater capillary contact area and secrete more, with analysis showing that, independent of the number of contact points, increased contact area is correlated with increased granule fusion. Using db/db mice as a model for type 2 diabetes, we observed changes in islet capillary organisation that significantly reduced total islet capillary surface area, and reduced area of capillary contact in single beta cells. CONCLUSIONS/INTERPRETATION Beta cells that contact two capillaries are a significant subpopulation of beta cells within the islet. They have a distinct form of cell polarity and both contact points are specialised for secretion. The larger capillary contact area of cells with two contact points is correlated with increased secretion. In the db/db mouse, changes in capillary structure impact beta cell capillary contact, implying that this is a new factor contributing to disease progression.
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Affiliation(s)
- Dillon Jevon
- Charles Perkins Centre, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Louise Cottle
- Charles Perkins Centre, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Nicole Hallahan
- Charles Perkins Centre, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Richard Harwood
- Charles Perkins Centre, Sydney Microscopy and Microanalysis, University of Sydney, Camperdown, NSW, Australia
| | - Jaswinder S Samra
- The University of Sydney Northern Clinical School, Sydney, NSW, Australia
- Upper Gastrointestinal Surgical Unit, Royal North Shore Hospital, St Leonards, NSW, Australia
| | - Anthony J Gill
- The University of Sydney Northern Clinical School, Sydney, NSW, Australia
- Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards, NSW, Australia
- Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards, NSW, Australia
| | | | - Helen E Thomas
- St Vincent's Institute, Fitzroy, VIC, Australia
- Department of Medicine, St Vincent's Hospital, University of Melbourne, Fitzroy, VIC, Australia
| | - Peter Thorn
- Charles Perkins Centre, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia.
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Khin PP, Lee JH, Jun HS. Pancreatic Beta-cell Dysfunction in Type 2 Diabetes. EUR J INFLAMM 2023. [DOI: 10.1177/1721727x231154152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Pancreatic β-cells produce and secrete insulin to maintain blood glucose levels within a narrow range. Defects in the function and mass of β-cells play a significant role in the development and progression of diabetes. Increased β-cell deficiency and β-cell apoptosis are observed in the pancreatic islets of patients with type 2 diabetes. At an early stage, β-cells adapt to insulin resistance, and their insulin secretion increases, but they eventually become exhausted, and the β-cell mass decreases. Various causal factors, such as high glucose, free fatty acids, inflammatory cytokines, and islet amyloid polypeptides, contribute to the impairment of β-cell function. Therefore, the maintenance of β-cell function is a logical approach for the treatment and prevention of diabetes. In this review, we provide an overview of the role of these risk factors in pancreatic β-cell loss and the associated mechanisms. A better understanding of the molecular mechanisms underlying pancreatic β-cell loss will provide an opportunity to identify novel therapeutic targets for type 2 diabetes.
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Affiliation(s)
- Phyu Phyu Khin
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, 155, Gaetbeol-ro, Yeonsu-gu, Incheon 21999, Republic of Korea
| | - Jong Han Lee
- Department of Marine Bio-industry, Hanseo University, Seosan, Korea
| | - Hee-Sook Jun
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, 155, Gaetbeol-ro, Yeonsu-gu, Incheon 21999, Republic of Korea
- College of Pharmacy and Gachon Institute of Pharmaceutical Science, Gachon University, 191, Hambangmoe-ro, Yeonsu-gu, Incheon 21936, Republic of Korea
- Gachon Medical Research Institute, Gil Hospital, 21, Namdong-daero 774, beon-gil, Namdong-gu, Incheon, 21565, Republic of Korea
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3
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Fye MA, Kaverina I. Insulin secretion hot spots in pancreatic β cells as secreting adhesions. Front Cell Dev Biol 2023; 11:1211482. [PMID: 37305687 PMCID: PMC10250740 DOI: 10.3389/fcell.2023.1211482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 05/18/2023] [Indexed: 06/13/2023] Open
Abstract
Pancreatic β cell secretion of insulin is crucial to the maintenance of glucose homeostasis and prevention of diseases related to glucose regulation, including diabetes. Pancreatic β cells accomplish efficient insulin secretion by clustering secretion events at the cell membrane facing the vasculature. Regions at the cell periphery characterized by clustered secretion are currently termed insulin secretion hot spots. Several proteins, many associated with the microtubule and actin cytoskeletons, are known to localize to and serve specific functions at hot spots. Among these proteins are the scaffolding protein ELKS, the membrane-associated proteins LL5β and liprins, the focal adhesion-associated protein KANK1, and other factors typically associated with the presynaptic active zone in neurons. These hot spot proteins have been shown to contribute to insulin secretion, but many questions remain regarding their organization and dynamics at hot spots. Current studies suggest microtubule- and F-actin are involved in regulation of hot spot proteins and their function in secretion. The hot spot protein association with the cytoskeleton networks also suggests a potential role for mechanical regulation of these proteins and hot spots in general. This perspective summarizes the existing knowledge of known hot spot proteins, their cytoskeletal-mediated regulation, and discuss questions remaining regarding mechanical regulation of pancreatic beta cell hot spots.
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Affiliation(s)
| | - Irina Kaverina
- Kaverina Lab, Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, United States
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Aoyagi K, Yamashita SI, Akimoto Y, Nishiwaki C, Nakamichi Y, Udagawa H, Abe M, Sakimura K, Kanki T, Ohara-Imaizumi M. A new beta cell-specific mitophagy reporter mouse shows that metabolic stress leads to accumulation of dysfunctional mitochondria despite increased mitophagy. Diabetologia 2023; 66:147-162. [PMID: 36181536 DOI: 10.1007/s00125-022-05800-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 08/11/2022] [Indexed: 12/13/2022]
Abstract
AIMS/HYPOTHESIS Mitophagy, the selective autophagy of mitochondria, is essential for maintenance of mitochondrial function. Recent studies suggested that defective mitophagy in beta cells caused diabetes. However, because of technical difficulties, the development of a convenient and reliable method to evaluate mitophagy in beta cells in vivo is needed. The aim of this study was to establish beta cell-specific mitophagy reporter mice and elucidate the role of mitophagy in beta cell function under metabolically stressed conditions induced by a high-fat diet (HFD). METHODS Mitophagy was assessed using newly generated conditional mitochondrial matrix targeting mitophagy reporter (CMMR) mice, in which mitophagy can be visualised specifically in beta cells in vivo using a fluorescent probe sensitive to lysosomal pH and degradation. Metabolic stress was induced in mice by exposure to the HFD for 20 weeks. The accumulation of dysfunctional mitochondria was examined by staining for functional/total mitochondria and reactive oxygen species (ROS) using specific fluorescent dyes and antibodies. To investigate the molecular mechanism underlying mitophagy in beta cells, overexpression and knockdown experiments were performed. HFD-fed mice were examined to determine whether chronic insulin treatment for 6 weeks could ameliorate mitophagy, mitochondrial function and impaired insulin secretion. RESULTS Exposure to the HFD increased the number of enlarged (HFD-G) islets with markedly elevated mitophagy. Mechanistically, HFD feeding induced severe hypoxia in HFD-G islets, which upregulated mitophagy through the hypoxia-inducible factor 1-ɑ (Hif-1ɑ)/BCL2 interacting protein 3 (BNIP3) axis in beta cells. However, HFD-G islets unexpectedly showed the accumulation of dysfunctional mitochondria due to excessive ROS production, suggesting an insufficient capacity of mitophagy for the degradation of dysfunctional mitochondria. Chronic administration of insulin ameliorated hypoxia and reduced ROS production and dysfunctional mitochondria, leading to decreased mitophagy and restored insulin secretion. CONCLUSIONS/INTERPRETATION We demonstrated that CMMR mice enabled the evaluation of mitophagy in beta cells. Our results suggested that metabolic stress induced by the HFD caused the aberrant accumulation of dysfunctional mitochondria, which overwhelmed the mitophagic capacity and was associated with defective maintenance of mitochondrial function and impaired insulin secretion.
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Affiliation(s)
- Kyota Aoyagi
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Shun-Ichi Yamashita
- Department of Cellular Physiology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Yoshihiro Akimoto
- Department of Microscopic Anatomy, Kyorin University School of Medicine, Tokyo, Japan
| | - Chiyono Nishiwaki
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Yoko Nakamichi
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Haruhide Udagawa
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Manabu Abe
- Department of Animal Model Development, Brain Research Institute, Niigata University, Niigata, Japan
| | - Kenji Sakimura
- Department of Animal Model Development, Brain Research Institute, Niigata University, Niigata, Japan
| | - Tomotake Kanki
- Department of Cellular Physiology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Mica Ohara-Imaizumi
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo, Japan.
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Barillaro M, Schuurman M, Wang R. β1-Integrin-A Key Player in Controlling Pancreatic Beta-Cell Insulin Secretion via Interplay With SNARE Proteins. Endocrinology 2022; 164:6772824. [PMID: 36282882 DOI: 10.1210/endocr/bqac179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Indexed: 01/16/2023]
Abstract
Shortcomings in cell-based therapies for patients with diabetes have been revealed to be, in part, a result of an improper extracellular matrix (ECM) environment. In vivo, pancreatic islets are emersed in a diverse ECM that provides physical support and is crucial for healthy function. β1-Integrin receptors have been determined to be responsible for modulation of beneficial interactions with ECM proteins influencing beta-cell development, proliferation, maturation, and function. β1-Integrin signaling has been demonstrated to augment insulin secretion by impacting the actin cytoskeleton via activation of focal adhesion kinase and downstream signaling pathways. In other secretory cells, evidence of a bidirectional relationship between integrins and exocytotic machinery has been demonstrated, and, thus, this relationship could be present in pancreatic beta cells. In this review, we will discuss the role of ECM-β1-integrin interplay with exocytotic proteins in controlling pancreatic beta-cell insulin secretion through their dynamic and unique signaling pathway.
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Affiliation(s)
- Malina Barillaro
- Children's Health Research Institute, University of Western Ontario, London, ON N6C 2V5, Canada
- Department of Physiology & Pharmacology, University of Western Ontario, London, ON N6C 2V5, Canada
| | - Meg Schuurman
- Children's Health Research Institute, University of Western Ontario, London, ON N6C 2V5, Canada
- Department of Physiology & Pharmacology, University of Western Ontario, London, ON N6C 2V5, Canada
| | - Rennian Wang
- Children's Health Research Institute, University of Western Ontario, London, ON N6C 2V5, Canada
- Department of Physiology & Pharmacology, University of Western Ontario, London, ON N6C 2V5, Canada
- Department of Medicine, University of Western Ontario, London, ON N6C 2V5, Canada
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Yang L, Fye MA, Yang B, Tang Z, Zhang Y, Haigh S, Covington BA, Bracey K, Taraska JW, Kaverina I, Qu S, Chen W. Genome-wide CRISPR screen identified a role for commander complex mediated ITGB1 recycling in basal insulin secretion. Mol Metab 2022; 63:101541. [PMID: 35835371 PMCID: PMC9304790 DOI: 10.1016/j.molmet.2022.101541] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 06/30/2022] [Accepted: 07/01/2022] [Indexed: 01/28/2023] Open
Abstract
OBJECTIVES Pancreatic beta cells secrete insulin postprandially and during fasting to maintain glucose homeostasis. Although glucose-stimulated insulin secretion (GSIS) has been extensively studied, much less is known about basal insulin secretion. Here, we performed a genome-wide CRISPR/Cas9 knockout screen to identify novel regulators of insulin secretion. METHODS To identify genes that cell autonomously regulate insulin secretion, we engineered a Cas9-expressing MIN6 subclone that permits irreversible fluorescence labeling of exocytic insulin granules. Using a fluorescence-activated cell sorting assay of exocytosis in low glucose and high glucose conditions in individual cells, we performed a genome-wide CRISPR/Cas9 knockout screen. RESULTS We identified several members of the COMMD family, a conserved family of proteins with central roles in intracellular membrane trafficking, as positive regulators of basal insulin secretion, but not GSIS. Mechanistically, we show that the Commander complex promotes insulin granules docking in basal state. This is mediated, at least in part, by its function in ITGB1 recycling. Defective ITGB1 recycling reduces its membrane distribution, the number of focal adhesions and cortical ELKS-containing complexes. CONCLUSIONS We demonstrated a previously unknown function of the Commander complex in basal insulin secretion. We showed that by ITGB1 recycling, Commander complex increases cortical adhesions, which enhances the assembly of the ELKS-containing complexes. The resulting increase in the number of insulin granules near the plasma membrane strengthens basal insulin secretion.
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Affiliation(s)
- Liu Yang
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai 200072, China; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Margret A Fye
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Bingyuan Yang
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Zihan Tang
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Yue Zhang
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Sander Haigh
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Brittney A Covington
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Kai Bracey
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Justin W Taraska
- Biochemistry and Biophysics Center, NHLBI, NIH, Bethesda, MD 20892, USA
| | - Irina Kaverina
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Shen Qu
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai 200072, China.
| | - Wenbiao Chen
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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7
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Jevon D, Deng K, Hallahan N, Kumar K, Tong J, Gan WJ, Tran C, Bilek MM, Thorn P. Local activation of focal adhesion kinase orchestrates the positioning of presynaptic scaffold proteins and Ca 2+ signalling to control glucose dependent insulin secretion. eLife 2022; 11:76262. [PMID: 35559734 PMCID: PMC9126582 DOI: 10.7554/elife.76262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 05/12/2022] [Indexed: 11/13/2022] Open
Abstract
A developing understanding suggests that spatial compartmentalisation in pancreatic β cells is critical in controlling insulin secretion. To investigate the mechanisms, we have developed live-cell sub-cellular imaging methods using the mouse organotypic pancreatic slice. We demonstrate that the organotypic pancreatic slice, when compared with isolated islets, preserves intact β cell structure, and enhances glucose dependent Ca2+ responses and insulin secretion. Using the slice technique, we have discovered the essential role of local activation of integrins and the downstream component, focal adhesion kinase, in regulating β cells. Integrins and focal adhesion kinase are exclusively activated at the β cell capillary interface and using in situ and in vitro models we show their activation both positions presynaptic scaffold proteins, like ELKS and liprin, and regulates glucose dependent Ca2+ responses and insulin secretion. We conclude that focal adhesion kinase orchestrates the final steps of glucose dependent insulin secretion within the restricted domain where β cells contact the islet capillaries.
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Affiliation(s)
- Dillon Jevon
- School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Kylie Deng
- School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Nicole Hallahan
- School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Krish Kumar
- School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Jason Tong
- School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Wan Jun Gan
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Clara Tran
- School of Physics, University of Sydney, Sydney, Australia
| | | | - Peter Thorn
- School of Medical Sciences, University of Sydney, Sydney, Australia
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8
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Deng K, Thorn P. Presynaptic-like mechanisms and the control of insulin secretion in pancreatic β-cells. Cell Calcium 2022; 104:102585. [DOI: 10.1016/j.ceca.2022.102585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 03/24/2022] [Accepted: 03/26/2022] [Indexed: 12/18/2022]
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9
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Improving effect of cordycepin on insulin synthesis and secretion in normal and oxidative-damaged INS-1 cells. Eur J Pharmacol 2022; 920:174843. [DOI: 10.1016/j.ejphar.2022.174843] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 02/05/2022] [Accepted: 02/16/2022] [Indexed: 01/18/2023]
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10
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Takikawa K, Nishimune H. Similarity and Diversity of Presynaptic Molecules at Neuromuscular Junctions and Central Synapses. Biomolecules 2022; 12:biom12020179. [PMID: 35204679 PMCID: PMC8961632 DOI: 10.3390/biom12020179] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 01/17/2022] [Accepted: 01/19/2022] [Indexed: 12/04/2022] Open
Abstract
Synaptic transmission is essential for controlling motor functions and maintaining brain functions such as walking, breathing, cognition, learning, and memory. Neurotransmitter release is regulated by presynaptic molecules assembled in active zones of presynaptic terminals. The size of presynaptic terminals varies, but the size of a single active zone and the types of presynaptic molecules are highly conserved among neuromuscular junctions (NMJs) and central synapses. Three parameters play an important role in the determination of neurotransmitter release properties at NMJs and central excitatory/inhibitory synapses: the number of presynaptic molecular clusters, the protein families of the presynaptic molecules, and the distance between presynaptic molecules and voltage-gated calcium channels. In addition, dysfunction of presynaptic molecules causes clinical symptoms such as motor and cognitive decline in patients with various neurological disorders and during aging. This review focuses on the molecular mechanisms responsible for the functional similarities and differences between excitatory and inhibitory synapses in the peripheral and central nervous systems, and summarizes recent findings regarding presynaptic molecules assembled in the active zone. Furthermore, we discuss the relationship between functional alterations of presynaptic molecules and dysfunction of NMJs or central synapses in diseases and during aging.
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Affiliation(s)
- Kenji Takikawa
- Laboratory of Neurobiology of Aging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashi-ku, Tokyo 173-0015, Japan;
| | - Hiroshi Nishimune
- Laboratory of Neurobiology of Aging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashi-ku, Tokyo 173-0015, Japan;
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology, 3-8-1 Harumi-cho, Fuchu-shi, Tokyo 183-8538, Japan
- Correspondence: ; Tel.: +81-3-3964-3241
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11
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Noordstra I, van den Berg CM, Boot FWJ, Katrukha EA, Yu KL, Tas RP, Portegies S, Viergever BJ, de Graaff E, Hoogenraad CC, de Koning EJP, Carlotti F, Kapitein LC, Akhmanova A. Organization and dynamics of the cortical complexes controlling insulin secretion in β-cells. J Cell Sci 2022; 135:274234. [PMID: 35006275 PMCID: PMC8918791 DOI: 10.1242/jcs.259430] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 12/21/2021] [Indexed: 11/20/2022] Open
Abstract
Insulin secretion in pancreatic β-cells is regulated by cortical complexes that are enriched at the sites of adhesion to extracellular matrix facing the vasculature. Many components of these complexes, including bassoon, RIM, ELKS and liprins, are shared with neuronal synapses. Here, we show that insulin secretion sites also contain the non-neuronal proteins LL5β (also known as PHLDB2) and KANK1, which, in migrating cells, organize exocytotic machinery in the vicinity of integrin-based adhesions. Depletion of LL5β or focal adhesion disassembly triggered by myosin II inhibition perturbed the clustering of secretory complexes and attenuated the first wave of insulin release. Although previous analyses in vitro and in neurons have suggested that secretory machinery might assemble through liquid–liquid phase separation, analysis of endogenously labeled ELKS in pancreatic islets indicated that its dynamics is inconsistent with such a scenario. Instead, fluorescence recovery after photobleaching and single-molecule imaging showed that ELKS turnover is driven by binding and unbinding to low-mobility scaffolds. Both the scaffold movements and ELKS exchange were stimulated by glucose treatment. Our findings help to explain how integrin-based adhesions control spatial organization of glucose-stimulated insulin release. Summary: Characterization of the composition of cortical complexes controlling insulin secretion, showing that their dynamics is inconsistent with assembly through liquid–liquid phase separation.
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Affiliation(s)
- Ivar Noordstra
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.,Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Cyntha M van den Berg
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Fransje W J Boot
- Department of Internal Medicine, Nephrology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands
| | - Eugene A Katrukha
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Ka Lou Yu
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Roderick P Tas
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Sybren Portegies
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Bastiaan J Viergever
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Esther de Graaff
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Casper C Hoogenraad
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Eelco J P de Koning
- Department of Internal Medicine, Nephrology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands
| | - Françoise Carlotti
- Department of Internal Medicine, Nephrology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands
| | - Lukas C Kapitein
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Anna Akhmanova
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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12
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Wang X, Gao M, Wang Y, Zhang Y. The progress of pluripotent stem cell-derived pancreatic β-cells regeneration for diabetic therapy. Front Endocrinol (Lausanne) 2022; 13:927324. [PMID: 35966093 PMCID: PMC9365963 DOI: 10.3389/fendo.2022.927324] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Accepted: 06/27/2022] [Indexed: 11/13/2022] Open
Abstract
Diabetes is a complex metabolic disorder of carbohydrate metabolism, characterized by high blood glucose levels either due to an absolute deficiency of insulin secretion or an ineffective response of cells to insulin, a hormone synthetized by β-cells in the pancreas. Despite the current substantial progress of new drugs and strategies to prevent and treat diabetes, we do not understand precisely the exact cause of the failure and impairment of β-cells. Therefore, there is an urgent need to find new methods to restore β-cells. In recent years, pluripotent stem cells (PSCs) such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSC) can serve as an ideal alternative source for the pancreatic β-cells. In this review, we systematically summarize the current progress and protocols of generating pancreatic β-cells from human PSCs. Meanwhile, we also discuss some challenges and future perspectives of human PSCs treatments for diabetes.
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Affiliation(s)
- Xin Wang
- China-Japan Union Hospital of Jilin University, Changchun, China
- The Third Norman Bethune Clinical College of Jilin University, Changchun, China
| | - Mengxi Gao
- China-Japan Union Hospital of Jilin University, Changchun, China
- The Third Norman Bethune Clinical College of Jilin University, Changchun, China
| | - Yali Wang
- Department of Blood Transfusion, China–Japan Union Hospital of Jilin University, Changchun, China
- *Correspondence: Yucheng Zhang, ; Yali Wang,
| | - Yucheng Zhang
- Scientific Research Center, China–Japan Union Hospital of Jilin University, Changchun, China
- *Correspondence: Yucheng Zhang, ; Yali Wang,
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13
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Gaus B, Brüning D, Groß S, Müller M, Rustenbeck I. The changing view of insulin granule mobility: From conveyor belt to signaling hub. Front Endocrinol (Lausanne) 2022; 13:983152. [PMID: 36120467 PMCID: PMC9478610 DOI: 10.3389/fendo.2022.983152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 08/11/2022] [Indexed: 11/28/2022] Open
Abstract
Before the advent of TIRF microscopy the fate of the insulin granule prior to secretion was deduced from biochemical investigations, electron microscopy and electrophysiological measurements. Since Calcium-triggered granule fusion is indisputably necessary to release insulin into the extracellular space, much effort was directed to the measure this event at the single granule level. This has also been the major application of the TIRF microscopy of the pancreatic beta cell when it became available about 20 years ago. To better understand the metabolic modulation of secretion, we were interested to characterize the entirety of the insulin granules which are localized in the vicinity of the plasma membrane to identify the characteristics which predispose to fusion. In this review we concentrate on how the description of granule mobility in the submembrane space has evolved as a result of progress in methodology. The granules are in a state of constant turnover with widely different periods of residence in this space. While granule fusion is associated +with prolonged residence and decreased lateral mobility, these characteristics may not only result from binding to the plasma membrane but also from binding to the cortical actin web, which is present in the immediate submembrane space. While granule age as such affects granule mobility and fusion probability, the preceding functional states of the beta cell leave their mark on these parameters, too. In summary, the submembrane granules form a highly dynamic heterogeneous population and contribute to the metabolic memory of the beta cells.
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Affiliation(s)
- Bastian Gaus
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Dennis Brüning
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Sofie Groß
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Michael Müller
- Institute of Dynamics and Vibrations, Technische Universität Braunschweig, Braunschweig, Germany
| | - Ingo Rustenbeck
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
- *Correspondence: Ingo Rustenbeck,
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14
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Trogden KP, Lee J, Bracey KM, Ho KH, McKinney H, Zhu X, Arpag G, Folland TG, Osipovich AB, Magnuson MA, Zanic M, Gu G, Holmes WR, Kaverina I. Microtubules regulate pancreatic β-cell heterogeneity via spatiotemporal control of insulin secretion hot spots. eLife 2021; 10:59912. [PMID: 34783306 PMCID: PMC8635970 DOI: 10.7554/elife.59912] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 11/08/2021] [Indexed: 12/25/2022] Open
Abstract
Heterogeneity of glucose-stimulated insulin secretion (GSIS) in pancreatic islets is physiologically important but poorly understood. Here, we utilize mouse islets to determine how microtubules (MTs) affect secretion toward the vascular extracellular matrix at single cell and subcellular levels. Our data indicate that MT stability in the β-cell population is heterogenous, and that GSIS is suppressed in cells with highly stable MTs. Consistently, MT hyper-stabilization prevents, and MT depolymerization promotes the capacity of single β-cell for GSIS. Analysis of spatiotemporal patterns of secretion events shows that MT depolymerization activates otherwise dormant β-cells via initiation of secretion clusters (hot spots). MT depolymerization also enhances secretion from individual cells, introducing both additional clusters and scattered events. Interestingly, without MTs, the timing of clustered secretion is dysregulated, extending the first phase of GSIS and causing oversecretion. In contrast, glucose-induced Ca2+ influx was not affected by MT depolymerization yet required for secretion under these conditions, indicating that MT-dependent regulation of secretion hot spots acts in parallel with Ca2+ signaling. Our findings uncover a novel MT function in tuning insulin secretion hot spots, which leads to accurately measured and timed response to glucose stimuli and promotes functional β-cell heterogeneity.
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Affiliation(s)
- Kathryn P Trogden
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
| | - Justin Lee
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
| | - Kai M Bracey
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
| | - Kung-Hsien Ho
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
| | - Hudson McKinney
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
| | - Xiaodong Zhu
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States.,Department of Medicine, Vanderbilt University, Nashville, United States
| | - Goker Arpag
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
| | - Thomas G Folland
- Department of Mechanical Engineering, Vanderbilt University, Nashville, United States
| | - Anna B Osipovich
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, United States.,Center for Stem Cell Biology, Vanderbilt University, Nashville, United States
| | - Mark A Magnuson
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States.,Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, United States.,Center for Stem Cell Biology, Vanderbilt University, Nashville, United States
| | - Marija Zanic
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States.,Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, United States.,Department of Biochemistry, Vanderbilt University, Nashville, United States
| | - Guoqiang Gu
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
| | - William R Holmes
- Department of Physics and Astronomy, Vanderbilt University, Nashville, United States.,Department of Mathematics, Vanderbilt University, Nashville, United States.,Quantitative Systems Biology Center, Vanderbilt University, Nashville, United States
| | - Irina Kaverina
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
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15
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Tuluc P, Theiner T, Jacobo-Piqueras N, Geisler SM. Role of High Voltage-Gated Ca 2+ Channel Subunits in Pancreatic β-Cell Insulin Release. From Structure to Function. Cells 2021; 10:2004. [PMID: 34440773 PMCID: PMC8393260 DOI: 10.3390/cells10082004] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/27/2021] [Accepted: 08/03/2021] [Indexed: 02/07/2023] Open
Abstract
The pancreatic islets of Langerhans secrete several hormones critical for glucose homeostasis. The β-cells, the major cellular component of the pancreatic islets, secrete insulin, the only hormone capable of lowering the plasma glucose concentration. The counter-regulatory hormone glucagon is secreted by the α-cells while δ-cells secrete somatostatin that via paracrine mechanisms regulates the α- and β-cell activity. These three peptide hormones are packed into secretory granules that are released through exocytosis following a local increase in intracellular Ca2+ concentration. The high voltage-gated Ca2+ channels (HVCCs) occupy a central role in pancreatic hormone release both as a source of Ca2+ required for excitation-secretion coupling as well as a scaffold for the release machinery. HVCCs are multi-protein complexes composed of the main pore-forming transmembrane α1 and the auxiliary intracellular β, extracellular α2δ, and transmembrane γ subunits. Here, we review the current understanding regarding the role of all HVCC subunits expressed in pancreatic β-cell on electrical activity, excitation-secretion coupling, and β-cell mass. The evidence we review was obtained from many seminal studies employing pharmacological approaches as well as genetically modified mouse models. The significance for diabetes in humans is discussed in the context of genetic variations in the genes encoding for the HVCC subunits.
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Affiliation(s)
- Petronel Tuluc
- Centre for Molecular Biosciences, Department of Pharmacology and Toxicology, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria; (T.T.); (N.J.-P.); (S.M.G.)
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16
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Cottle L, Gan WJ, Gilroy I, Samra JS, Gill AJ, Loudovaris T, Thomas HE, Hawthorne WJ, Kebede MA, Thorn P. Structural and functional polarisation of human pancreatic beta cells in islets from organ donors with and without type 2 diabetes. Diabetologia 2021; 64:618-629. [PMID: 33399909 PMCID: PMC7864831 DOI: 10.1007/s00125-020-05345-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 10/09/2020] [Indexed: 12/05/2022]
Abstract
AIMS/HYPOTHESIS We hypothesised that human beta cells are structurally and functional polarised with respect to the islet capillaries. We set out to test this using confocal microscopy to map the 3D spatial arrangement of key proteins and live-cell imaging to determine the distribution of insulin granule fusion around the cells. METHODS Human pancreas samples were rapidly fixed and processed using the pancreatic slice technique, which maintains islet structure and architecture. Slices were stained using immunofluorescence for polarity markers (scribble, discs large [Dlg] and partitioning defective 3 homologue [Par3]) and presynaptic markers (liprin, Rab3-interacting protein [RIM2] and piccolo) and imaged using 3D confocal microscopy. Isolated human islets were dispersed and cultured on laminin-511-coated coverslips. Live 3D two-photon microscopy was used on cultured cells to image exocytic granule fusion events upon glucose stimulation. RESULTS Assessment of the distribution of endocrine cells across human islets found that, despite distinct islet-to-islet complexity and variability, including multi-lobular islets, and intermixing of alpha and beta cells, there is still a striking enrichment of alpha cells at the islet mantle. Measures of cell position demonstrate that most beta cells contact islet capillaries. Subcellularly, beta cells consistently position polar determinants, such as Par3, Dlg and scribble, with a basal domain towards the capillaries and apical domain at the opposite face. The capillary interface/vascular face is enriched in presynaptic scaffold proteins, such as liprin, RIM2 and piccolo. Interestingly, enrichment of presynaptic scaffold proteins also occurs where the beta cells contact peri-islet capillaries, suggesting functional interactions. We also observed the same polarisation of synaptic scaffold proteins in islets from type 2 diabetic patients. Consistent with polarised function, isolated beta cells cultured onto laminin-coated coverslips target insulin granule fusion to the coverslip. CONCLUSIONS/INTERPRETATION Structural and functional polarisation is a defining feature of human pancreatic beta cells and plays an important role in the control of insulin secretion.
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Affiliation(s)
- Louise Cottle
- Charles Perkins Centre, Discipline of Physiology, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Wan Jun Gan
- Charles Perkins Centre, Discipline of Physiology, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
- Temasek Life-Science Laboratory, Singapore, Republic of Singapore
| | - Ian Gilroy
- Charles Perkins Centre, Discipline of Physiology, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Jaswinder S Samra
- The University of Sydney Northern Clinical School, Sydney, NSW, Australia
- Upper Gastrointestinal Surgical Unit, Royal North Shore Hospital, St Leonards, NSW, Australia
| | - Anthony J Gill
- The University of Sydney Northern Clinical School, Sydney, NSW, Australia
- Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards, NSW, Australia
- Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards, NSW, Australia
| | | | - Helen E Thomas
- St Vincent's Institute, Fitzroy, VIC, Australia
- The University of Melbourne, Department of Medicine, St Vincent's Hospital, Fitzroy, VIC, Australia
| | - Wayne J Hawthorne
- Centre for Transplant and Renal Research, Westmead Hospital, Sydney, NSW, Australia
- Westmead Clinical School, Faculty of Health and Medicine, University of Sydney, Sydney, Australia
| | - Melkam A Kebede
- Charles Perkins Centre, Discipline of Physiology, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Peter Thorn
- Charles Perkins Centre, Discipline of Physiology, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia.
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17
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Singh R, Cottle L, Loudovaris T, Xiao D, Yang P, Thomas HE, Kebede MA, Thorn P. Enhanced structure and function of human pluripotent stem cell-derived beta-cells cultured on extracellular matrix. Stem Cells Transl Med 2020; 10:492-505. [PMID: 33145960 PMCID: PMC7900592 DOI: 10.1002/sctm.20-0224] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 10/07/2020] [Accepted: 10/09/2020] [Indexed: 12/14/2022] Open
Abstract
The differentiation of human stem cells into insulin secreting beta‐like cells holds great promise to treat diabetes. Current protocols drive stem cells through stages of directed differentiation and maturation and produce cells that secrete insulin in response to glucose. Further refinements are now needed to faithfully phenocopy the responses of normal beta cells. A critical factor in normal beta cell behavior is the islet microenvironment which plays a central role in beta cell survival, proliferation, gene expression and secretion. One important influence on native cell responses is the capillary basement membrane. In adult islets, each beta cell makes a point of contact with basement membrane protein secreted by vascular endothelial cells resulting in structural and functional polarization. Interaction with basement membrane proteins triggers local activation of focal adhesions, cell orientation, and targeting of insulin secretion. This study aims to identifying the role of basement membrane proteins on the structure and function of human embryonic stem cell and induced pluripotent stem cell‐derived beta cells. Here, we show that differentiated human stem cells‐derived spheroids do contain basement membrane proteins as a diffuse web‐like structure. However, the beta‐like cells within the spheroid do not polarize in response to this basement membrane. We demonstrate that 2D culture of the differentiated beta cells on to basement membrane proteins enforces cell polarity and favorably alters glucose dependent insulin secretion.
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Affiliation(s)
- Reena Singh
- Charles Perkins Centre, Discipline of Physiology, School of Medical Sciences, University of Sydney, Camperdown, New South Wales, Australia
| | - Louise Cottle
- Charles Perkins Centre, Discipline of Physiology, School of Medical Sciences, University of Sydney, Camperdown, New South Wales, Australia
| | | | - Di Xiao
- Computational Systems Biology Group, Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, Australia
| | - Pengyi Yang
- Computational Systems Biology Group, Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, Australia.,Charles Perkins Centre, School of Mathematics and Statistics, University of Sydney, Sydney, New South Wales, Australia
| | - Helen E Thomas
- St Vincent's Institute, Fitzroy, Victoria, Australia.,Department of Medicine, St Vincent's Hospital, The University of Melbourne, Fitzroy, Victoria, Australia
| | - Melkam A Kebede
- Charles Perkins Centre, Discipline of Physiology, School of Medical Sciences, University of Sydney, Camperdown, New South Wales, Australia
| | - Peter Thorn
- Charles Perkins Centre, Discipline of Physiology, School of Medical Sciences, University of Sydney, Camperdown, New South Wales, Australia
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18
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Montenegro-Venegas C, Fienko S, Anni D, Pina-Fernández E, Frischknecht R, Fejtova A. Bassoon inhibits proteasome activity via interaction with PSMB4. Cell Mol Life Sci 2020; 78:1545-1563. [PMID: 32651614 PMCID: PMC7904567 DOI: 10.1007/s00018-020-03590-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 06/19/2020] [Accepted: 07/01/2020] [Indexed: 01/06/2023]
Abstract
Abstract Proteasomes are protein complexes that mediate controlled degradation of damaged or unneeded cellular proteins. In neurons, proteasome regulates synaptic function and its dysfunction has been linked to neurodegeneration and neuronal cell death. However, endogenous mechanisms controlling proteasomal activity are insufficiently understood. Here, we describe a novel interaction between presynaptic scaffolding protein bassoon and PSMB4, a β subunit of the 20S core proteasome. Expression of bassoon fragments that interact with PSMB4 in cell lines or in primary neurons attenuates all endopeptidase activities of cellular proteasome and induces accumulation of several classes of ubiquitinated and non-ubiquitinated substrates of the proteasome. Importantly, these effects are distinct from the previously reported impact of bassoon on ubiquitination and autophagy and might rely on a steric interference with the assembly of the 20S proteasome core. In line with a negative regulatory role of bassoon on endogenous proteasome we found increased proteasomal activity in the synaptic fractions prepared from brains of bassoon knock-out mice. Finally, increased activity of proteasome and lower expression levels of synaptic substrates of proteasome could be largely normalized upon expression of PSMB4-interacting fragments of bassoon in neurons derived from bassoon deficient mice. Collectively, we propose that bassoon interacts directly with proteasome to control its activity at presynapse and thereby it contributes to a compartment-specific regulation of neuronal protein homeostasis. These findings provide a mechanistic explanation for the recently described link of bassoon to human diseases associated with pathological protein aggregation. Graphic Abstract Presynaptic cytomatrix protein bassoon (Bsn) interacts with PSMB4, the β7 subunit of 20S core proteasome, via three independent interaction interfaces. Bsn inhibits proteasomal proteolytic activity and degradation of different classes of proteasomal substrates presumably due to steric interference with the assembly of 20S core of proteasome. Upon Bsn deletion in neurons, presynaptic substrates of the proteasome are depleted, which can be reversed upon expression of PSMB4-interacting interfaces of Bsn. Taken together, bsn controls the degree of proteasome degradation within the presynaptic compartment and thus, contributes to the regulation of synaptic proteome![]() Electronic supplementary material The online version of this article (10.1007/s00018-020-03590-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Carolina Montenegro-Venegas
- Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, Germany
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University and Center for Behavior Brain Sciences (CBBS), Magdeburg, Germany
| | - Sandra Fienko
- Molecular Psychiatry, Department of Psychiatry and Psychotherapy, University Hospital, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
- RG Presynaptic Plasticity, Leibniz Institute for Neurobiology, Magdeburg, Germany
- Huntington's Disease Centre, Department of Neurodegenerative Disease, UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Daniela Anni
- Molecular Psychiatry, Department of Psychiatry and Psychotherapy, University Hospital, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Eneko Pina-Fernández
- RG Presynaptic Plasticity, Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Renato Frischknecht
- Department of Biology, Animal Physiology, Friedrich-Alexander University of Erlangen- Nürnberg, Erlangen, Germany
| | - Anna Fejtova
- Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, Germany.
- Molecular Psychiatry, Department of Psychiatry and Psychotherapy, University Hospital, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
- RG Presynaptic Plasticity, Leibniz Institute for Neurobiology, Magdeburg, Germany.
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19
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Lam HY, Arumugam S, Bae HG, Wang CC, Jung S, St John AL, Hong W, Han W, Tergaonkar V. ELKS1 controls mast cell degranulation by regulating the transcription of Stxbp2 and Syntaxin 4 via Kdm2b stabilization. SCIENCE ADVANCES 2020; 6:6/31/eabb2497. [PMID: 32937583 PMCID: PMC7531903 DOI: 10.1126/sciadv.abb2497] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 06/09/2020] [Indexed: 05/06/2023]
Abstract
ELKS1 is a protein with proposed roles in regulated exocytosis in neurons and nuclear factor κB (NF-κB) signaling in cancer cells. However, how these two potential roles come together under physiological settings remain unknown. Since both regulated exocytosis and NF-κB signaling are determinants of mast cell (MC) functions, we generated mice lacking ELKS1 in connective tissue MCs (Elks1f/f Mcpt5-Cre) and found that while ELKS1 is dispensable for NF-κB-mediated cytokine production, it is essential for MC degranulation both in vivo and in vitro. Impaired degranulation was caused by reduced transcription of Syntaxin 4 (STX4) and Syntaxin binding protein 2 (Stxpb2), resulting from a lack of ELKS1-mediated stabilization of lysine-specific demethylase 2B (Kdm2b), which is an essential regulator of STX4 and Stxbp2 transcription. These results suggest a transcriptional role for active-zone proteins like ELKS1 and suggest that they may regulate exocytosis through a novel mechanism involving transcription of key exocytosis proteins.
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Affiliation(s)
- Hiu Yan Lam
- Laboratory of NF-κB Signaling, Institute of Molecular and Cell Biology (IMCB), 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore 117596, Singapore
| | - Surendar Arumugam
- Laboratory of NF-κB Signaling, Institute of Molecular and Cell Biology (IMCB), 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
| | - Han Gyu Bae
- Singapore Bioimaging Consortium, Agency for Science, Technology and Research, #02-02 Helios, 11 Biopolis Way, Singapore 138667, Singapore
| | - Cheng Chun Wang
- Institute of Molecular and Cell Biology (IMCB), 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
| | - Sangyong Jung
- Singapore Bioimaging Consortium, Agency for Science, Technology and Research, #02-02 Helios, 11 Biopolis Way, Singapore 138667, Singapore
| | - Ashley Lauren St John
- Program in Emerging Infectious Diseases, Duke-NUS, Singapore 169857, Singapore
- Department of Microbiology and Immunology, NUS, Singapore 119077, Singapore
- Department of Pathology, Duke University Medical Center, Durham, NC, USA
| | - Wanjin Hong
- Institute of Molecular and Cell Biology (IMCB), 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
| | - Weiping Han
- Singapore Bioimaging Consortium, Agency for Science, Technology and Research, #02-02 Helios, 11 Biopolis Way, Singapore 138667, Singapore
| | - Vinay Tergaonkar
- Laboratory of NF-κB Signaling, Institute of Molecular and Cell Biology (IMCB), 61 Biopolis Drive, Proteos, Singapore 138673, Singapore.
- Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore 119074, Singapore
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20
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Ohara-Imaizumi M, Aoyagi K, Ohtsuka T. Role of the active zone protein, ELKS, in insulin secretion from pancreatic β-cells. Mol Metab 2020; 27S:S81-S91. [PMID: 31500835 PMCID: PMC6768504 DOI: 10.1016/j.molmet.2019.06.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Background Insulin is stored within large dense-core granules in pancreatic beta (β)-cells and is released by Ca2+-triggered exocytosis with increasing blood glucose levels. Polarized and targeted secretion of insulin from β-cells in pancreatic islets into the vasculature has been proposed; however, the mechanisms related to cellular and molecular localization remain largely unknown. Within nerve terminals, the Ca2+-dependent release of a polarized transmitter is limited to the active zone, a highly specialized area of the presynaptic membrane. Several active zone-specific proteins have been characterized; among them, the CAST/ELKS protein family members have the ability to form large protein complexes with other active zone proteins to control the structure and function of the active zone for tight regulation of neurotransmitter release. Notably, ELKS but not CAST is also expressed in β-cells, implying that ELKS may be involved in polarized insulin secretion from β-cells. Scope of review This review provides an overview of the current findings regarding the role(s) of ELKS and other active zone proteins in β-cells and focuses on the molecular mechanism underlying ELKS regulation within polarized insulin secretion from islets. Major conclusions ELKS localizes at the vascular-facing plasma membrane of β-cells in mouse pancreatic islets. ELKS forms a potent insulin secretion complex with L-type voltage-dependent Ca2+ channels on the vascular-facing plasma membrane of β-cells, enabling polarized Ca2+ influx and first-phase insulin secretion from islets. This model provides novel insights into the functional polarity observed during insulin secretion from β-cells within islets at the molecular level. This active zone-like region formed by ELKS at the vascular side of the plasma membrane is essential for coordinating physiological insulin secretion and may be disrupted in diabetes.
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Affiliation(s)
- Mica Ohara-Imaizumi
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan.
| | - Kyota Aoyagi
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Graduate School of Medicine, University of Yamanashi, Yamanashi 409-3898, Japan
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21
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Yokoyama T, Yamamoto Y, Hirakawa M, Kato K, Saino T. Vesicular nucleotide transporter-immunoreactive type I cells associated with P2X3-immunoreactive nerve endings in the rat carotid body. J Comp Neurol 2019; 528:1486-1501. [PMID: 31808543 DOI: 10.1002/cne.24837] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 11/21/2019] [Accepted: 12/02/2019] [Indexed: 12/23/2022]
Abstract
ATP is the major excitatory transmitter from chemoreceptor type I cells to sensory nerve endings in the carotid body, and has been suggested to be released by exocytosis from these cells. We investigated the mRNA expression and immunohistochemical localization of vesicular nucleotide transporter (VNUT) in the rat carotid body. RT-PCR detected mRNA expression of VNUT in extracts of the tissue. Immunoreactivity for VNUT was localized in a part of type I cells immunoreactive for synaptophysin (SYN), but not in glial-like type II cells immunoreactive for S100 and S100B. Among SYN-immunoreactive type I cells, VNUT immunoreactivity was selectively localized in the sub-population of tyrosine hydroxylase (TH)-immunorective type I cells associated with nerve endings immunoreactive for the P2X3 purinoceptor; however, it was not detected in the sub-population of type I cells immunoreactive for dopamine beta-hydroxylase. Multi-immunolabeling for VNUT, P2X3, and Bassoon revealed that Bassoon-immunoreactive products were localized in type I cells with VNUT immunoreactivity, and accumulated on the contact side of P2X3-immunoreactive nerve endings. These results revealed the selective localization of VNUT in the subpopulation of TH-immunoreactive type I cells attached to sensory nerve endings and suggested that these cells release ATP by exocytosis for chemosensory transmission in the carotid body.
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Affiliation(s)
- Takuya Yokoyama
- Department of Anatomy (Cell Biology), Iwate Medical University, Yahaba, Japan
| | - Yoshio Yamamoto
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Japan
| | - Masato Hirakawa
- Department of Anatomy (Cell Biology), Iwate Medical University, Yahaba, Japan
| | - Kouki Kato
- Center for Laboratory Animal Science, National Defense Medical College, Tokorozawa, Japan
| | - Tomoyuki Saino
- Department of Anatomy (Cell Biology), Iwate Medical University, Yahaba, Japan
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22
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Lammert E, Thorn P. The Role of the Islet Niche on Beta Cell Structure and Function. J Mol Biol 2019; 432:1407-1418. [PMID: 31711959 DOI: 10.1016/j.jmb.2019.10.032] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/25/2019] [Accepted: 10/29/2019] [Indexed: 01/15/2023]
Abstract
The islets of Langerhans or pancreatic islets are pivotal in the control of blood glucose and are complex microorgans embedded within the larger volume of the exocrine pancreas. Humans can have ~3.2 million islets [1] which, to our current knowledge, function in a similar manner to sense circulating blood glucose levels and respond with the secretion of a mix of different hormones that act to maintain glucose concentrations around a specific set point [2]. At a cellular level, the control of hormone secretion by glucose and other secretagogues is well-understood [3]. The key signal cascades have been identified and many details of the secretory process are known. However, if we shift focus from single cells and consider cells within intact islets, we do not have a comprehensive model as to how the islet environment influences cell function and how the islets work as a whole. This is important because there is overwhelming evidence that the structure and function of the individual endocrine cells are dramatically affected by the islet environment [4,5]. Uncovering the influence of this islet niche might drive future progress in treatments for Type 2 diabetes [6] and cell replacement therapies for Type 1 diabetes [7]. In this review, we focus on the insulin secreting beta cells and their interactions with the immediate environment that surrounds them including endocrine-endocrine interactions and contacts with capillaries.
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Affiliation(s)
- Eckhard Lammert
- Institute of Metabolic Physiology, Heinrich Heine University, Düsseldorf, Germany; Institute for Vascular and Islet Cell Biology, German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Düsseldorf, Germany; German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Peter Thorn
- Charles Perkins Centre, School of Medical Sciences, University of Sydney, Camperdown, NSW 2006, Australia.
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23
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Sawatani T, Kaneko YK, Ishikawa T. Dual effect of reduced type I diacylglycerol kinase activity on insulin secretion from MIN6 β-cells. J Pharmacol Sci 2019; 140:178-186. [PMID: 31279581 DOI: 10.1016/j.jphs.2019.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 05/03/2019] [Accepted: 06/11/2019] [Indexed: 02/07/2023] Open
Abstract
The role of type I diacylglycerol kinases (DGKs) in the regulation of insulin secretion was investigated in MIN6 β-cells. In intracellular Ca2+ concentration ([Ca2+]i) measurement experiments, 1 μM R59949, a type I DGK inhibitor, and 10 μM DiC8, a diacylglycerol (DAG) analog, amplified 22.2 mM glucose-induced [Ca2+]i oscillations in a protein kinase C (PKC)-dependent manner, whereas 10 μM R59949 and 100 μM DiC8 decreased [Ca2+]i independent of PKC. High concentrations of R59949 and DiC8 attenuated voltage-dependent Ca2+ channel currents. According to these results, 22.2 mM glucose-stimulated insulin secretion (GSIS) was potentiated by 1 μM R59949 but suppressed by 10 μM of the same. The DGKα inhibitor R59022 showed a similar dual effect. Conversely, DiC8 at 10 and 100 μM potentiated GSIS, although 100 μM DiC8 decreased [Ca2+]i. These results suggest that DAG accumulated through declined type I DGK activity shows a dual effect on insulin secretion depending on the degree of accumulation; a mild DAG accumulation induces a PKC-dependent stimulatory effect on insulin secretion, whereas an excessive DAG accumulation suppresses it in a PKC-independent manner, possibly via attenuation of VDCC activity.
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Affiliation(s)
- Toshiaki Sawatani
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan
| | - Yukiko K Kaneko
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan.
| | - Tomohisa Ishikawa
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan
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24
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Fu J, Githaka JM, Dai X, Plummer G, Suzuki K, Spigelman AF, Bautista A, Kim R, Greitzer-Antes D, Fox JEM, Gaisano HY, MacDonald PE. A glucose-dependent spatial patterning of exocytosis in human β-cells is disrupted in type 2 diabetes. JCI Insight 2019; 5:127896. [PMID: 31085831 DOI: 10.1172/jci.insight.127896] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Impaired insulin secretion in type 2 diabetes (T2D) is linked to reduced insulin granule docking, disorganization of the exocytotic site, and an impaired glucose-dependent facilitation of insulin exocytosis. We show in β-cells from 80 human donors that the glucose-dependent amplification of exocytosis is disrupted in T2D. Spatial analyses of granule fusion, visualized by total internal reflection fluorescence (TIRF) microscopy in 24 of these donors, demonstrate that these are non-random across the surface of β-cells from donors with no diabetes (ND). The compartmentalization of events occurs within regions defined by concurrent or recent membrane-resident secretory granules. This organization, and the number of membrane-associated granules, is glucose-dependent and notably impaired in T2D β-cells. Mechanistically, multi-channel Kv2.1 clusters contribute to maintaining the density of membrane-resident granules and the number of fusion 'hotspots', while SUMOylation sites at the channel N- (K145) and C-terminus (K470) determine the relative proportion of fusion events occurring within these regions. Thus, a glucose-dependent compartmentalization of fusion, regulated in part by a structural role for Kv2.1, is disrupted in β-cells from donors with type 2 diabetes.
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Affiliation(s)
- Jianyang Fu
- Alberta Diabetes Institute and Department of Pharmacology and
| | | | - Xiaoqing Dai
- Alberta Diabetes Institute and Department of Pharmacology and
| | - Gregory Plummer
- Alberta Diabetes Institute and Department of Pharmacology and
| | - Kunimasa Suzuki
- Alberta Diabetes Institute and Department of Pharmacology and
| | | | - Austin Bautista
- Alberta Diabetes Institute and Department of Pharmacology and
| | - Ryekjang Kim
- Alberta Diabetes Institute and Department of Pharmacology and
| | - Dafna Greitzer-Antes
- Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario, Canada
| | | | - Herbert Y Gaisano
- Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario, Canada
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