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Quiroz VM, Wang Y, Rakoski AI, Kasinathan D, Neshat SY, Hollister-Lock J, Doloff JC. Hydrogel Alginate Considerations for Improved 3D Matrix Stability and Cell Graft Viability and Function in Studying Type 1 Diabetes In Vitro. Adv Biol (Weinh) 2024:e2300502. [PMID: 38243878 PMCID: PMC11259579 DOI: 10.1002/adbi.202300502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Indexed: 01/22/2024]
Abstract
Biomedical devices such as islet-encapsulating systems are used for treatment of type 1 diabetes (T1D). Despite recent strides in preventing biomaterial fibrosis, challenges remain for biomaterial scaffolds due to limitations on cells contained within. The study demonstrates that proliferation and function of insulinoma (INS-1) cells as well as pancreatic rat islets may be improved in alginate hydrogels with optimized gel%, crosslinking, and stiffness. Quantitative polymerase chain reaction (qPCR)-based graft phenotyping of encapsulated INS-1 cells and pancreatic islets identified a hydrogel stiffness range between 600 and 1000 Pa that improved insulin Ins and Pdx1 gene expression as well as glucose-sensitive insulin-secretion. Barium chloride (BaCl2 ) crosslinking time is also optimized due to toxicity of extended exposure. Despite possible benefits to cell viability, calcium chloride (CaCl2 )-crosslinked hydrogels exhibited a sharp storage modulus loss in vitro. Despite improved stability, BaCl2 -crosslinked hydrogels also exhibited stiffness losses over the same timeframe. It is believed that this is due to ion exchange with other species in culture media, as hydrogels incubated in dIH2 O exhibited significantly improved stability. To maintain cell viability and function while increasing 3D matrix stability, a range of useful media:dIH2 O dilution ratios for use are identified. Such findings have importance to carry out characterization and optimization of cell microphysiological systems with high fidelity in vitro.
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Affiliation(s)
- Victor M. Quiroz
- Department of Biomedical Engineering, Translational Tissue Engineering Center, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
- Institute for Nanobiotechnology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Yuanjia Wang
- Department of Biomedical Engineering, Translational Tissue Engineering Center, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Amanda I. Rakoski
- Department of Biomedical Engineering, Translational Tissue Engineering Center, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
- Institute for Nanobiotechnology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Devi Kasinathan
- Department of Physiology, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Sarah Y. Neshat
- Department of Biomedical Engineering, Translational Tissue Engineering Center, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
- Institute for Nanobiotechnology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Jennifer Hollister-Lock
- Section on Islet Cell and Regenerative Biology, Research Division, Joslin Diabetes Center, One Joslin Place, Boston, Massachusetts 02215, USA
| | - Joshua C. Doloff
- Department of Biomedical Engineering, Translational Tissue Engineering Center, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
- Institute for Nanobiotechnology, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Oncology, Sidney-Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
- Bloomberg-Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
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2
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Kumari D, Ray K. Phosphoregulation of Kinesins Involved in Long-Range Intracellular Transport. Front Cell Dev Biol 2022; 10:873164. [PMID: 35721476 PMCID: PMC9203973 DOI: 10.3389/fcell.2022.873164] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 04/29/2022] [Indexed: 12/28/2022] Open
Abstract
Kinesins, the microtubule-dependent mechanochemical enzymes, power a variety of intracellular movements. Regulation of Kinesin activity and Kinesin-Cargo interactions determine the direction, timing and flux of various intracellular transports. This review examines how phosphorylation of Kinesin subunits and adaptors influence the traffic driven by Kinesin-1, -2, and -3 family motors. Each family of Kinesins are phosphorylated by a partially overlapping set of serine/threonine kinases, and each event produces a unique outcome. For example, phosphorylation of the motor domain inhibits motility, and that of the stalk and tail domains induces cargo loading and unloading effects according to the residue and context. Also, the association of accessory subunits with cargo and adaptor proteins with the motor, respectively, is disrupted by phosphorylation. In some instances, phosphorylation by the same kinase on different Kinesins elicited opposite outcomes. We discuss how this diverse range of effects could manage the logistics of Kinesin-dependent, long-range intracellular transport.
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3
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Hunt JE, Holst JJ, Jepsen SL. Glucose- and Bile Acid-Stimulated Secretion of Gut Hormones in the Isolated Perfused Intestine Is Not Impaired in Diet-Induced Obese Mice. Front Endocrinol (Lausanne) 2022; 13:884501. [PMID: 35600607 PMCID: PMC9114496 DOI: 10.3389/fendo.2022.884501] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 03/31/2022] [Indexed: 11/22/2022] Open
Abstract
PURPOSE Decreased circulating levels of food-intake-regulating gut hormones have been observed in type 2 diabetes and obesity. However, it is still unknown if this is due to decreased secretion from the gut mucosal cells or due to extra-intestinal processing of hormones. METHODS We measured intestinal hormone content and assessed morphological differences in the intestinal mucosa by histology and immunohistochemistry. Secretion of hormones and absorption of glucose and bile acids (BA) were assessed in isolated perfused mouse intestine. RESULTS GIP (glucose-dependent insulinotropic polypeptide) and SS (somatostatin) contents were higher in the duodenum of control mice (p < 0.001, and <0.01). Duodenal GLP-1 (glucagon-like peptide-1) content (p < 0.01) and distal ileum PYY content were higher in DIO mice (p < 0.05). Villus height in the jejunum, crypt depth, and villus height in the ileum were increased in DIO mice (p < 0.05 and p = 0.001). In the distal ileum of DIO mice, more immunoreactive GLP-1 and PYY cells were observed (p = 0.01 and 0.007). There was no difference in the absorption of glucose and bile acids. Distal secretion of SS tended to be higher in DIO mice (p < 0.058), whereas no difference was observed for the other hormones in response to glucose or bile acids. CONCLUSION Our data suggest that differences regarding production and secretion are unlikely to be responsible for the altered circulating gut hormone levels in obesity, since enteroendocrine morphology and hormone secretion capacity were largely unaffected in DIO mice.
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Affiliation(s)
- Jenna E. Hunt
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens J. Holst
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sara L. Jepsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- *Correspondence: Sara L. Jepsen,
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4
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Wang X, Yi H, Gdor I, Hereld M, Scherer NF. Nanoscale Resolution 3D Snapshot Particle Tracking by Multifocal Microscopy. NANO LETTERS 2019; 19:6781-6787. [PMID: 31490694 DOI: 10.1021/acs.nanolett.9b01734] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Accurate, precise, and rapid particle tracking in three dimensions remains a challenge; yet, its achievement will significantly enhance our understanding of living systems. We developed a multifocal microscopy (MFM) that allows snapshot acquisition of the imaging data, and an associated image processing approach, that together allow simultaneous 3D tracking of many fluorescent particles with nanoscale resolution. The 3D tracking was validated by measuring a known trajectory of a fluorescent bead with an axial accuracy of 19 nm through an image depth (axial range) of 3 μm and 4 nm precision of axial localization through an image depth of 4 μm. A second test obtained a uniform axial probability distribution and Brownian dynamics of beads diffusing in solution. We also validated the MFM approach by imaging fluorescent beads immobilized in gels and comparing the 3D localizations to their "ground truth" positions obtained from a confocal microscopy z-stack of finely spaced images. Finally, we applied our MFM and image processing approach to obtain 3D trajectories of insulin granules in pseudoislets of MIN6 cells to demonstrate its compatibility with complex biological systems. Our study demonstrates that multifocal microscopy allows rapid (video rate) and simultaneous 3D tracking of many "particles" with nanoscale accuracy and precision in a wide range of systems, including over spatial scales relevant to whole live cells.
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Affiliation(s)
- Xiaolei Wang
- James Franck Institute , University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States
| | - Hannah Yi
- Department of Chemistry , University of Chicago , 5801 South Ellis Avenue , Chicago , Illinois 60637 , United States
| | - Itay Gdor
- James Franck Institute , University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States
| | - Mark Hereld
- Mathematics and Computer Science Division , Argonne National Laboratory , 9700 South Cass Avenue , Lemont , Illinois 60439 , United States
| | - Norbert F Scherer
- James Franck Institute , University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States
- Department of Chemistry , University of Chicago , 5801 South Ellis Avenue , Chicago , Illinois 60637 , United States
- Institute for Biophysical Dynamics , University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States
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5
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Zhang Q, Pan Y, Zeng B, Zheng X, Wang H, Shen X, Li H, Jiang Q, Zhao J, Meng ZX, Li P, Chen Z, Wei H, Liu Z. Intestinal lysozyme liberates Nod1 ligands from microbes to direct insulin trafficking in pancreatic beta cells. Cell Res 2019; 29:516-532. [PMID: 31201384 PMCID: PMC6796897 DOI: 10.1038/s41422-019-0190-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 05/21/2019] [Indexed: 02/06/2023] Open
Abstract
Long-range communication between intestinal symbiotic bacteria and extra-intestinal organs can occur through circulating bacterial signal molecules, through neural circuits, or through cytokines or hormones from host cells. Here we report that Nod1 ligands derived from intestinal bacteria act as signal molecules and directly modulate insulin trafficking in pancreatic beta cells. The cytosolic peptidoglycan receptor Nod1 and its downstream adapter Rip2 are required for insulin trafficking in beta cells in a cell-autonomous manner. Mechanistically, upon recognizing cognate ligands, Nod1 and Rip2 localize to insulin vesicles, recruiting Rab1a to direct insulin trafficking through the cytoplasm. Importantly, intestinal lysozyme liberates Nod1 ligands into the circulation, thus enabling long-range communication between intestinal microbes and islets. The intestine-islet crosstalk bridged by Nod1 ligands modulates host glucose tolerance. Our study defines a new type of inter-organ communication based on circulating bacterial signal molecules, which has broad implications for understanding the mutualistic relationship between microbes and host.
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Affiliation(s)
- Qin Zhang
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Ying Pan
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Benhua Zeng
- Department of Laboratory Animal Science, College of Basic Medical Sciences, Third Military Medical University, Chongqing, 400038, China
| | - Xiaojiao Zheng
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Haifang Wang
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Xueying Shen
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hui Li
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Qian Jiang
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100050, China
| | - Jiaxu Zhao
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, 320 Yueyang Rd, Shanghai, 200031, China.,Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, 320 Yueyang Rd, Shanghai, 200031, China
| | - Zhuo-Xian Meng
- Department of Pathology and Pathophysiology, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Pingping Li
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100050, China
| | - Zhengjun Chen
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, 320 Yueyang Rd, Shanghai, 200031, China.,Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, 320 Yueyang Rd, Shanghai, 200031, China.,ShanghaiTech Univ, Sch Life Sci & Technol, 100 Haike Rd, Shanghai, 201210, China
| | - Hong Wei
- Precision Medicine Institute, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, 510080, China.
| | - Zhihua Liu
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China. .,Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, Beijing, 100101, China.
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6
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Nasteska D, Hodson DJ. The role of beta cell heterogeneity in islet function and insulin release. J Mol Endocrinol 2018; 61:R43-R60. [PMID: 29661799 PMCID: PMC5976077 DOI: 10.1530/jme-18-0011] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 04/16/2018] [Indexed: 12/15/2022]
Abstract
It is becoming increasingly apparent that not all insulin-secreting beta cells are equal. Subtle differences exist at the transcriptomic and protein expression levels, with repercussions for beta cell survival/proliferation, calcium signalling and insulin release. Notably, beta cell heterogeneity displays plasticity during development, metabolic stress and type 2 diabetes mellitus (T2DM). Thus, heterogeneity or lack thereof may be an important contributor to beta cell failure during T2DM in both rodents and humans. The present review will discuss the molecular and cellular features of beta cell heterogeneity at both the single-cell and islet level, explore how this influences islet function and insulin release and look into the alterations that may occur during obesity and T2DM.
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Affiliation(s)
- Daniela Nasteska
- Institute of Metabolism and Systems Research (IMSR)University of Birmingham, Edgbaston, UK
- Centre for EndocrinologyDiabetes and Metabolism, Birmingham Health Partners, Birmingham, UK
- COMPARE University of Birmingham and University of Nottingham MidlandsBirmingham, UK
| | - David J Hodson
- Institute of Metabolism and Systems Research (IMSR)University of Birmingham, Edgbaston, UK
- Centre for EndocrinologyDiabetes and Metabolism, Birmingham Health Partners, Birmingham, UK
- COMPARE University of Birmingham and University of Nottingham MidlandsBirmingham, UK
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7
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No novel, high penetrant gene might remain to be found in Japanese patients with unknown MODY. J Hum Genet 2018; 63:821-829. [PMID: 29670293 DOI: 10.1038/s10038-018-0449-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 03/07/2018] [Accepted: 03/09/2018] [Indexed: 11/08/2022]
Abstract
MODY 5 and 6 have been shown to be low-penetrant MODYs. As the genetic background of unknown MODY is assumed to be similar, a new analytical strategy is applied here to elucidate genetic predispositions to unknown MODY. We examined to find whether there are major MODY gene loci remaining to be identified using SNP linkage analysis in Japanese. Whole-exome sequencing was performed with seven families with typical MODY. Candidates for novel MODY genes were examined combined with in silico network analysis. Some peaks were found only in either parametric or non-parametric analysis; however, none of these peaks showed a LOD score greater than 3.7, which is approved to be the significance threshold of evidence for linkage. Exome sequencing revealed that three mutated genes were common among 3 families and 42 mutated genes were common in two families. Only one of these genes, MYO5A, having rare amino acid mutations p.R849Q and p.V1601G, was involved in the biological network of known MODY genes through the intermediary of the INS. Although only one promising candidate gene, MYO5A, was identified, no novel, high penetrant MODY genes might remain to be found in Japanese MODY.
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8
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Duvoor C, Dendi VS, Marco A, Shekhawat NS, Chada A, Ravilla R, Musham CK, Mirza W, Chaudhury A. Commentary: ATP: The crucial component of secretory vesicles: Accelerated ATP/insulin exocytosis and prediabetes. Front Physiol 2017; 8:53. [PMID: 28210227 PMCID: PMC5288386 DOI: 10.3389/fphys.2017.00053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 01/19/2017] [Indexed: 02/03/2023] Open
Affiliation(s)
- Chitharanjan Duvoor
- Department of Endocrinology and Internal Medicine, University of Arkansas for Medical SciencesLittle Rock, AR, USA; GIM FoundationLittle Rock, AR, USA
| | - Vijaya S Dendi
- GIM FoundationLittle Rock, AR, USA; Department of Internal Medicine and Hospital Medicine, Christus Trinity Mother Frances HospitalTyler, TX, USA
| | - Asween Marco
- GIM FoundationLittle Rock, AR, USA; Department of Policy, University of Arkansas for Little RockLittle Rock, AR, USA
| | - Nawal S Shekhawat
- GIM FoundationLittle Rock, AR, USA; Tutwiler ClinicTutwiler, MS, USA
| | - Aditya Chada
- GIM FoundationLittle Rock, AR, USA; Department of Pulmonary and Critical Care Medicine, University of Arkansas for Medical SciencesLittle Rock, AR, USA
| | - Rahul Ravilla
- GIM FoundationLittle Rock, AR, USA; Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical SciencesLittle Rock, AR, USA
| | - Chaitanya K Musham
- GIM FoundationLittle Rock, AR, USA; St. Vincent Infirmary (Catholic Health Initiative)Little Rock, AR, USA
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9
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Li WH. Probes for monitoring regulated exocytosis. Cell Calcium 2017; 64:65-71. [PMID: 28089267 DOI: 10.1016/j.ceca.2017.01.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 01/07/2017] [Indexed: 12/12/2022]
Abstract
Regulated secretion is a fundamental cellular process that serves diverse functions in neurobiology, endocrinology, immunology, and numerous other aspects of animal physiology. In response to environmental or biological cues, cells release contents of secretory granules into an extracellular medium to communicate with or impact neighboring or distant cells through paracrine or endocrine signaling. To investigate mechanisms governing stimulus-secretion coupling, to better understand how cells maintain or regulate their secretory activity, and to characterize secretion defects in human diseases, probes for tracking various exocytotic events at the cellular or sub-cellular level have been developed over the years. This review summarizes different strategies and recent progress in developing optical probes for monitoring regulated secretion in mammalian cells.
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Affiliation(s)
- Wen-Hong Li
- Departments of Cell Biology and of Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9039, United States.
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10
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Arous C, Halban PA. The skeleton in the closet: actin cytoskeletal remodeling in β-cell function. Am J Physiol Endocrinol Metab 2015; 309:E611-20. [PMID: 26286869 DOI: 10.1152/ajpendo.00268.2015] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 08/11/2015] [Indexed: 01/13/2023]
Abstract
Over the last few decades, biomedical research has considered not only the function of single cells but also the importance of the physical environment within a whole tissue, including cell-cell and cell-extracellular matrix interactions. Cytoskeleton organization and focal adhesions are crucial sensors for cells that enable them to rapidly communicate with the physical extracellular environment in response to extracellular stimuli, ensuring proper function and adaptation. The involvement of the microtubular-microfilamentous cytoskeleton in secretion mechanisms was proposed almost 50 years ago, since when the evolution of ever more sensitive and sophisticated methods in microscopy and in cell and molecular biology have led us to become aware of the importance of cytoskeleton remodeling for cell shape regulation and its crucial link with signaling pathways leading to β-cell function. Emerging evidence suggests that dysfunction of cytoskeletal components or extracellular matrix modification influences a number of disorders through potential actin cytoskeleton disruption that could be involved in the initiation of multiple cellular functions. Perturbation of β-cell actin cytoskeleton remodeling could arise secondarily to islet inflammation and fibrosis, possibly accounting in part for impaired β-cell function in type 2 diabetes. This review focuses on the role of actin remodeling in insulin secretion mechanisms and its close relationship with focal adhesions and myosin II.
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Affiliation(s)
- Caroline Arous
- Department of Genetic Medicine and Development, University of Geneva Medical Center, Geneva, Switzerland
| | - Philippe A Halban
- Department of Genetic Medicine and Development, University of Geneva Medical Center, Geneva, Switzerland
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11
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Di Cairano ES, Moretti S, Marciani P, Sacchi VF, Castagna M, Davalli A, Folli F, Perego C. Neurotransmitters and Neuropeptides: New Players in the Control of Islet of Langerhans' Cell Mass and Function. J Cell Physiol 2015; 231:756-67. [PMID: 26332080 DOI: 10.1002/jcp.25176] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/27/2015] [Indexed: 12/19/2022]
Abstract
Islets of Langerhans control whole body glucose homeostasis, as they respond, releasing hormones, to changes in nutrient concentrations in the blood stream. The regulation of hormone secretion has been the focus of attention for a long time because it is related to many metabolic disorders, including diabetes mellitus. Endocrine cells of the islet use a sophisticate system of endocrine, paracrine and autocrine signals to synchronize their activities. These signals provide a fast and accurate control not only for hormone release but also for cell differentiation and survival, key aspects in islet physiology and pathology. Among the different categories of paracrine/autocrine signals, this review highlights the role of neurotransmitters and neuropeptides. In a manner similar to neurons, endocrine cells synthesize, accumulate, release neurotransmitters in the islet milieu, and possess receptors able to decode these signals. In this review, we provide a comprehensive description of neurotransmitter/neuropetide signaling pathways present within the islet. Then, we focus on evidence supporting the concept that neurotransmitters/neuropeptides and their receptors are interesting new targets to preserve β-cell function and mass. A greater understanding of how this network of signals works in physiological and pathological conditions would advance our knowledge of islet biology and physiology and uncover potentially new areas of pharmacological intervention. J. Cell. Physiol. 231: 756-767, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Eliana S Di Cairano
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Stefania Moretti
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Paola Marciani
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Vellea Franca Sacchi
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Michela Castagna
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
| | - Alberto Davalli
- Department of Internal Medicine, Diabetes and Endocrinology Unit, San Raffaele Scientific Institute, Milan, Italy
| | - Franco Folli
- Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, Texas.,Department of Internal Medicine, Obesity and Comorbidities Research Center (OCRC), University of Campinas, UNICAMP, Campinas, Sao Paulo State, Brazil
| | - Carla Perego
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Laboratory of Molecular and Cellular Physiology, Universit, à, degli Studi di Milano, Milan, Italy
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12
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HAP1 helps to regulate actin-based transport of insulin-containing granules in pancreatic β cells. Histochem Cell Biol 2015; 144:39-48. [PMID: 25744490 DOI: 10.1007/s00418-015-1311-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/14/2015] [Indexed: 10/23/2022]
Abstract
Huntingtin-associated protein 1 (HAP1) is enriched in neurons and binds to polyglutamine-expanded huntingtin. It consists of two alternatively spliced isoforms, HAP1A and HAP1B, which differ only in their short C-terminal sequences. Both HAP1A and HAP1B have been also detected in pancreatic β cells, where the loss of HAP1 impairs glucose-stimulated insulin secretion. Here, we use time-lapse laser scanning confocal microscopy to provide direct evidence that HAP1A, but not HAP1B, co-localizes and co-migrates with insulin-containing vesicles and actin-based myosin Va motor protein in the INS-1 pancreatic β cell line. Knocking down HAP1 expression using small interfering RNA significantly inhibited actin-based transport of insulin vesicles following glucose stimulation. Co-immunoprecipitation experiments demonstrated interaction between HAP1A, myosin Va, and phogrin, a transmembrane protein in insulin-containing vesicles. Stimulating INS-1 cells with glucose increased the association of HAP1A with myosin Va, while silencing HAP1 expression reduced the association of myosin Va with phogrin after glucose stimulation, without affecting levels of myosin Va or actin. Our results provide real-time evidence in living cells that HAP1 may help regulate transport of insulin-containing secretory granules along cortical actin filaments. This also raises the possibility that HAP1 may play an important role in actin-based secretory vesicle trafficking in neurons.
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13
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Beznoussenko GV, Parashuraman S, Rizzo R, Polishchuk R, Martella O, Di Giandomenico D, Fusella A, Spaar A, Sallese M, Capestrano MG, Pavelka M, Vos MR, Rikers YGM, Helms V, Mironov AA, Luini A. Transport of soluble proteins through the Golgi occurs by diffusion via continuities across cisternae. eLife 2014; 3:e02009. [PMID: 24867214 PMCID: PMC4070021 DOI: 10.7554/elife.02009] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 05/25/2014] [Indexed: 12/18/2022] Open
Abstract
The mechanism of transport through the Golgi complex is not completely understood, insofar as no single transport mechanism appears to account for all of the observations. Here, we compare the transport of soluble secretory proteins (albumin and α1-antitrypsin) with that of supramolecular cargoes (e.g., procollagen) that are proposed to traverse the Golgi by compartment progression-maturation. We show that these soluble proteins traverse the Golgi much faster than procollagen while moving through the same stack. Moreover, we present kinetic and morphological observations that indicate that albumin transport occurs by diffusion via intercisternal continuities. These data provide evidence for a transport mechanism that applies to a major class of secretory proteins and indicate the co-existence of multiple intra-Golgi trafficking modes.
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Affiliation(s)
- Galina V Beznoussenko
- Fondazione IFOM, Istituto FIRC di Oncologia Molecolare (IFOM-IEO Campus), Milan, Italy
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Seetharaman Parashuraman
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
- Institute of Protein Biochemistry, Consiglio Nazionale Delle Ricerche (CNR-IBP), Naples, Italy
| | - Riccardo Rizzo
- Institute of Protein Biochemistry, Consiglio Nazionale Delle Ricerche (CNR-IBP), Naples, Italy
| | - Roman Polishchuk
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
- Telethon Institute for Genetics and Medicine (TIGEM), Naples, Italy
| | - Oliviano Martella
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Daniele Di Giandomenico
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Aurora Fusella
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Alexander Spaar
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Michele Sallese
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Maria Grazia Capestrano
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
| | - Margit Pavelka
- Department of Cell Biology and Ultrastructure Research, Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
| | | | | | - Volkhard Helms
- Center for Bioinformatics, Saarland University, Saarbruecken, Germany
| | - Alexandre A Mironov
- Fondazione IFOM, Istituto FIRC di Oncologia Molecolare (IFOM-IEO Campus), Milan, Italy
| | - Alberto Luini
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy
- Institute of Protein Biochemistry, Consiglio Nazionale Delle Ricerche (CNR-IBP), Naples, Italy
- Telethon Institute for Genetics and Medicine (TIGEM), Naples, Italy
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14
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Hilderink J, Otto C, Slump C, Lenferink A, Engelse M, van Blitterswijk C, de Koning E, Karperien M, van Apeldoorn A. Label-free detection of insulin and glucagon within human islets of Langerhans using Raman spectroscopy. PLoS One 2013; 8:e78148. [PMID: 24167603 PMCID: PMC3805587 DOI: 10.1371/journal.pone.0078148] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 09/09/2013] [Indexed: 01/25/2023] Open
Abstract
Intrahepatic transplantation of donor islets of Langerhans is a promising therapy for patients with type 1 diabetes. It is of critical importance to accurately monitor islet quality before transplantation, which is currently done by standard histological methods that are performed off-line and require extensive sample preparation. As an alternative, we propose Raman spectroscopy which is a non-destructive and label-free technique that allows continuous real-time monitoring of the tissue to study biological changes as they occur. By performing Raman spectroscopic measurements on purified insulin and glucagon, we showed that the 520 cm(-1) band assigned to disulfide bridges in insulin, and the 1552 cm(-1) band assigned to tryptophan in glucagon are mutually exclusive and could therefore be used as indirect markers for the label-free distinction between both hormones. High-resolution hyperspectral Raman imaging for these bands showed the distribution of disulfide bridges and tryptophan at sub-micrometer scale, which correlated with the location of insulin and glucagon as revealed by conventional immunohistochemistry. As a measure for this correlation, quantitative analysis was performed comparing the Raman images with the fluorescence images, resulting in Dice coefficients (ranging between 0 and 1) of 0.36 for insulin and 0.19 for glucagon. Although the use of separate microscope systems with different spatial resolution and the use of indirect Raman markers cause some image mismatch, our findings indicate that Raman bands for disulfide bridges and tryptophan can be used as distinctive markers for the label-free detection of insulin and glucagon in human islets of Langerhans.
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Affiliation(s)
- Janneke Hilderink
- Department of Developmental BioEngineering, University of Twente, Enschede, The Netherlands
| | - Cees Otto
- Department of Medical Cell Biophysics, University of Twente, Enschede, The Netherlands
| | - Cees Slump
- Department of Systems and Signals, University of Twente, Enschede, The Netherlands
| | - Aufried Lenferink
- Department of Medical Cell Biophysics, University of Twente, Enschede, The Netherlands
| | - Marten Engelse
- Department of Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Eelco de Koning
- Department of Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | - Marcel Karperien
- Department of Developmental BioEngineering, University of Twente, Enschede, The Netherlands
| | - Aart van Apeldoorn
- Department of Developmental BioEngineering, University of Twente, Enschede, The Netherlands
- * E-mail:
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15
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Gao J, Gu X, Mahuran DJ, Wang Z, Zhang H. Impaired glucose tolerance in a mouse model of sidt2 deficiency. PLoS One 2013; 8:e66139. [PMID: 23776622 PMCID: PMC3679015 DOI: 10.1371/journal.pone.0066139] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 05/02/2013] [Indexed: 11/18/2022] Open
Abstract
Sidt2 was identified as a novel integral lysosomal membrane protein recently. We generated global Sidt2 knockout mice by gene targeting. These mice have a comparatively higher random and fasting glucose concentration. Intraperitoneal and oral glucose tolerance tests in Sidt2 knockout mice indicated glucose intolerance and decreased serum insulin level. Notably, the Sidt2(-/-) mice had hypertrophic islets compared with control mice. By Western blot and immunofluorescence, Sidt2(-/-) mouse islets were shown to have increased insulin protein, which actually contained more insulin secretory granules than their controls, demonstrated by electromicroscopy. Consistent with the in vivo study, isolated islet culture from the Sidt2(-/-) mice produced less insulin when stimulated by a high concentration of glucose or a depolarizing concentration of KCl. Under electromicroscope less empty vesicles and more mature ones in Sidt2(-/-) mice islets were observed, supporting impaired insulin secretory granule release. In conclusion, Sidt2 may play a critical role in the regulation of mouse insulin secretory granule secretion.
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Affiliation(s)
- Jialin Gao
- Department of Pediatric Endocrinology and Genetic Metabolism, Xinhua Hospital, Shanghai Institute for Pediatric Research, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xuefan Gu
- Department of Pediatric Endocrinology and Genetic Metabolism, Xinhua Hospital, Shanghai Institute for Pediatric Research, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- * E-mail: (XG); (HZ)
| | - Don J. Mahuran
- Department of Laboratory Medicine & Pathobiology, Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Canada
| | - Zhugang Wang
- Shanghai Research Centre for Model Organisms, Shanghai, China
| | - Huiwen Zhang
- Department of Pediatric Endocrinology and Genetic Metabolism, Xinhua Hospital, Shanghai Institute for Pediatric Research, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- * E-mail: (XG); (HZ)
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16
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Hartman TR, Strochlic TI, Ji Y, Zinshteyn D, O'Reilly AM. Diet controls Drosophila follicle stem cell proliferation via Hedgehog sequestration and release. ACTA ACUST UNITED AC 2013; 201:741-57. [PMID: 23690177 PMCID: PMC3664720 DOI: 10.1083/jcb.201212094] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Dietary cholesterol levels control follicle stem cell proliferation in the Drosophila ovary via regulation of Hedgehog protein localization. A healthy diet improves adult stem cell function and delays diseases such as cancer, heart disease, and neurodegeneration. Defining molecular mechanisms by which nutrients dictate stem cell behavior is a key step toward understanding the role of diet in tissue homeostasis. In this paper, we elucidate the mechanism by which dietary cholesterol controls epithelial follicle stem cell (FSC) proliferation in the fly ovary. In nutrient-restricted flies, the transmembrane protein Boi sequesters Hedgehog (Hh) ligand at the surface of Hh-producing cells within the ovary, limiting FSC proliferation. Upon feeding, dietary cholesterol stimulates S6 kinase–mediated phosphorylation of the Boi cytoplasmic domain, triggering Hh release and FSC proliferation. This mechanism enables a rapid, tissue-specific response to nutritional changes, tailoring stem cell divisions and egg production to environmental conditions sufficient for progeny survival. If conserved in other systems, this mechanism will likely have important implications for studies on molecular control of stem cell function, in which the benefits of low calorie and low cholesterol diets are beginning to emerge.
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Affiliation(s)
- Tiffiney R Hartman
- Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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17
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Patil H, Cho KI, Lee J, Yang Y, Orry A, Ferreira PA. Kinesin-1 and mitochondrial motility control by discrimination of structurally equivalent but distinct subdomains in Ran-GTP-binding domains of Ran-binding protein 2. Open Biol 2013; 3:120183. [PMID: 23536549 PMCID: PMC3718338 DOI: 10.1098/rsob.120183] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The pleckstrin homology (PH) domain is a versatile fold that mediates a variety of protein–protein and protein–phosphatidylinositol lipid interactions. The Ran-binding protein 2 (RanBP2) contains four interspersed Ran GTPase-binding domains (RBDn= 1–4) with close structural homology to the PH domain of Bruton's tyrosine kinase. The RBD2, kinesin-binding domain (KBD) and RBD3 comprise a tripartite domain (R2KR3) of RanBP2 that causes the unfolding, microtubule binding and biphasic activation of kinesin-1, a crucial anterograde motor of mitochondrial motility. However, the interplay between Ran GTPase and R2KR3 of RanBP2 in kinesin-1 activation and mitochondrial motility is elusive. We use structure–function, biochemical, kinetic and cell-based assays with time-lapse live-cell microscopy of over 260 000 mitochondrial-motility-related events to find mutually exclusive subdomains in RBD2 and RBD3 towards Ran GTPase binding, kinesin-1 activation and mitochondrial motility regulation. The RBD2 and RBD3 exhibit Ran-GTP-independent, subdomain and stereochemical-dependent discrimination on the biphasic kinetics of kinesin-1 activation or regulation of mitochondrial motility. Further, KBD alone and R2KR3 stimulate and suppress, respectively, multiple biophysical parameters of mitochondrial motility. The regulation of the bidirectional transport of mitochondria by either KBD or R2KR3 is highly coordinated, because their kinetic effects are accompanied always by changes in mitochondrial motile events of either transport polarity. These studies uncover novel roles in Ran GTPase-independent subdomains of RBD2 and RBD3, and KBD of RanBP2, that confer antagonizing and multi-modal mechanisms of kinesin-1 activation and regulation of mitochondrial motility. These findings open new venues towards the pharmacological harnessing of cooperative and competitive mechanisms regulating kinesins, RanBP2 or mitochondrial motility in disparate human disorders.
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Affiliation(s)
- Hemangi Patil
- Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
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18
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Thorn P. New insights into the control of secretion. Commun Integr Biol 2013; 2:315-7. [PMID: 19721876 DOI: 10.4161/cib.2.4.8262] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 02/21/2009] [Indexed: 11/19/2022] Open
Abstract
Vesicular secretion is a fundamental process in the body with vesicle fusion releasing vesicle contents to the outside. This process called exocytosis is usually thought of as leading to an all-or-none release of content; regulation of secretory output dependent on regulating the numbers of fused vesicles. However, it is well established that the fusion pore that forms when the vesicle membrane fuses with the cell membrane is dynamic. More recent evidence indicates the dynamic opening and closing, and the size of the fusion pore, are limiting factors to the release of vesicle content. What remains unclear is whether these fusion pore behaviors are under cellular control and therefore relevant to cell physiology.Accumulating evidence over the last two years points to myosin 2 as one regulator of fusion pore behavior. This is interesting since myosin 2 activity is in turn controlled by kinases and phosphatases, well known to be under cellular control. We conclude that fusion pore behavior is likely a genuine control point for vesicle content release. This leads to a model for secretion with secretory output controlled not only by the numbers of vesicles fused but also by the regulation of the behavior of individual vesicles.
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Affiliation(s)
- Peter Thorn
- School of Biomedical Sciences; University of Queensland; St. Lucia, Queensland Australia
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19
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Exome array analysis identifies new loci and low-frequency variants influencing insulin processing and secretion. Nat Genet 2012; 45:197-201. [PMID: 23263489 DOI: 10.1038/ng.2507] [Citation(s) in RCA: 216] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 11/26/2012] [Indexed: 12/15/2022]
Abstract
Insulin secretion has a crucial role in glucose homeostasis, and failure to secrete sufficient insulin is a hallmark of type 2 diabetes. Genome-wide association studies (GWAS) have identified loci contributing to insulin processing and secretion; however, a substantial fraction of the genetic contribution remains undefined. To examine low-frequency (minor allele frequency (MAF) 0.5-5%) and rare (MAF < 0.5%) nonsynonymous variants, we analyzed exome array data in 8,229 nondiabetic Finnish males using the Illumina HumanExome Beadchip. We identified low-frequency coding variants associated with fasting proinsulin concentrations at the SGSM2 and MADD GWAS loci and three new genes with low-frequency variants associated with fasting proinsulin or insulinogenic index: TBC1D30, KANK1 and PAM. We also show that the interpretation of single-variant and gene-based tests needs to consider the effects of noncoding SNPs both nearby and megabases away. This study demonstrates that exome array genotyping is a valuable approach to identify low-frequency variants that contribute to complex traits.
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20
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Dai XQ, Manning Fox JE, Chikvashvili D, Casimir M, Plummer G, Hajmrle C, Spigelman AF, Kin T, Singer-Lahat D, Kang Y, Shapiro AMJ, Gaisano HY, Lotan I, Macdonald PE. The voltage-dependent potassium channel subunit Kv2.1 regulates insulin secretion from rodent and human islets independently of its electrical function. Diabetologia 2012; 55:1709-20. [PMID: 22411134 DOI: 10.1007/s00125-012-2512-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Accepted: 01/24/2012] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS It is thought that the voltage-dependent potassium channel subunit Kv2.1 (Kv2.1) regulates insulin secretion by controlling beta cell electrical excitability. However, this role of Kv2.1 in human insulin secretion has been questioned. Interestingly, Kv2.1 can also regulate exocytosis through direct interaction of its C-terminus with the soluble NSF attachment receptor (SNARE) protein, syntaxin 1A. We hypothesised that this interaction mediates insulin secretion independently of Kv2.1 electrical function. METHODS Wild-type Kv2.1 or mutants lacking electrical function and syntaxin 1A binding were studied in rodent and human beta cells, and in INS-1 cells. Small intracellular fragments of the channel were used to disrupt native Kv2.1-syntaxin 1A complexes. Single-cell exocytosis and ion channel currents were monitored by patch-clamp electrophysiology. Interaction between Kv2.1, syntaxin 1A and other SNARE proteins was probed by immunoprecipitation. Whole-islet Ca(2+)-responses were monitored by ratiometric Fura red fluorescence and insulin secretion was measured. RESULTS Upregulation of Kv2.1 directly augmented beta cell exocytosis. This happened independently of channel electrical function, but was dependent on the Kv2.1 C-terminal syntaxin 1A-binding domain. Intracellular fragments of the Kv2.1 C-terminus disrupted native Kv2.1-syntaxin 1A interaction and impaired glucose-stimulated insulin secretion. This was not due to altered ion channel activity or impaired Ca(2+)-responses to glucose, but to reduced SNARE complex formation and Ca(2+)-dependent exocytosis. CONCLUSIONS/INTERPRETATION Direct interaction between syntaxin 1A and the Kv2.1 C-terminus is required for efficient insulin exocytosis and glucose-stimulated insulin secretion. This demonstrates that native Kv2.1-syntaxin 1A interaction plays a key role in human insulin secretion, which is separate from the channel's electrical function.
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Affiliation(s)
- X Q Dai
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada T6G 2E1
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21
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DeSUMOylation Controls Insulin Exocytosis in Response to Metabolic Signals. Biomolecules 2012; 2:269-81. [PMID: 24970137 PMCID: PMC4030845 DOI: 10.3390/biom2020269] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Revised: 05/14/2012] [Accepted: 05/16/2012] [Indexed: 12/25/2022] Open
Abstract
The secretion of insulin by pancreatic islet β-cells plays a pivotal role in glucose homeostasis and diabetes. Recent work suggests an important role for SUMOylation in the control of insulin secretion from β-cells. In this paper we discuss mechanisms whereby (de)SUMOylation may control insulin release by modulating β-cell function at one or more key points; and particularly through the acute and reversible regulation of the exocytotic machinery. Furthermore, we postulate that the SUMO-specific protease SENP1 is an important mediator of insulin exocytosis in response to NADPH, a metabolic secretory signal and major determinant of β-cell redox state. Dialysis of mouse β-cells with NADPH efficiently amplifies β-cell exocytosis even when extracellular glucose is low; an effect that is lost upon knockdown of SENP1. Conversely, over-expression of SENP1 itself augments β-cell exocytosis in a redox-dependent manner. Taken together, we suggest that (de)SUMOylation represents an important mechanism that acutely regulates insulin secretion and that SENP1 can act as an amplifier of insulin exocytosis.
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22
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Manning Fox JE, Hajmrle C, Macdonald PE. Novel roles of SUMO in pancreatic β-cells: thinking outside the nucleus. Can J Physiol Pharmacol 2012; 90:765-70. [PMID: 22486776 DOI: 10.1139/y11-134] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The endocrine pancreas is critically important in the regulation of energy metabolism, with defective insulin secretion from pancreatic islet β-cells a major contributing factor to the development of type 2 diabetes. Small ubiquitin-like modifier (SUMO) proteins have been demonstrated to covalently modify a wide range of target proteins, mediating a broad range of cellular processes. While the effects of SUMOylation on β-cell gene transcription have been previously reviewed, recent reports indicate roles for SUMO outside of the nucleus. In this review we shall focus on the reported non-nuclear roles of SUMOylation in the regulation of β-cells, including SUMOylation as a novel signaling pathway in the acute regulation of insulin secretion.
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Affiliation(s)
- Jocelyn E Manning Fox
- Department of Pharmacology and Alberta Diabetes Institute, Li Ka Shing Centre, University of Alberta, Edmonton, AB T6G 2E1, Canada.
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23
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Misler S, Gillis KD. Modes of exocytosis and electrogenesis underlying canine biphasic insulin secretion. Front Biosci (Elite Ed) 2012. [PMID: 22201903 DOI: 10.2741/408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Biphasic insulin secretion in response to glucose consists of a transient first phase followed by a progressive second phase. It is a well described feature of whole perfused pancreases as well as isolated pancreatic islets of Langerhans. Applying to single cell assays of exocytosis (capacitance monitoring and amperometry) to single canine Beta-cells we have examined the time courses of granule exocytosis in response to voltage-clamp depolarizations that mimic two modes of glucose-induced electrical activity, and then compared these to biphasic insulin secretion. Action potentials evoked in short trains at frequencies similar those recorded during first phase insulin secretion trigger phasic exocytosis from a small pool of insulin granules that are likely docked near voltage-activated Ca²⁺ channels. In contrast, prolonged voltage-clamp pulses mimicking plateau depolarizations occur during second phase insulin secretion and trigger tonic or continuous exocytosis. Comparing the latter results with ones obtained using photorelease of caged Ca²⁺ in other insulin-secreting cells, we suggest that tonic exocytosis likely results from granule release from a highly Ca²⁺-sensitive pool of insulin granules, likely located further from Ca²⁺ channels. Both phasic and tonic modes of exocytosis are enhanced by glucose, via its metabolism. Hence, in canine Beta-cells we propose that two distinct modes of exocytosis, tuned to two types of electrical activity, may underlay biphasic insulin secretion.
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Affiliation(s)
- Stanley Misler
- Department of Medicine, Washington University School of Medicine, St. Louis MO 63110, USA.
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24
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MacDonald PE. Signal integration at the level of ion channel and exocytotic function in pancreatic β-cells. Am J Physiol Endocrinol Metab 2011; 301:E1065-9. [PMID: 21934040 DOI: 10.1152/ajpendo.00426.2011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Whole body energy balance is ensured by the exquisite control of insulin secretion, the dysregulation of which has serious consequences. Although a great deal has been learned about the control of insulin secretion from pancreatic β-cells in the past 30 years, there remains much to be understood about the molecular mechanisms and interactions that underlie the precise control of this process. Numerous molecular interactions at the plasma membrane mediate the excitatory and amplifying events involved in insulin secretion; this includes interactions between ion channels, signal transduction machinery, and exocytotic proteins. The present Perspectives article considers evidence that key membrane and membrane-associated proteins essential to insulin secretion are regulated in concert as a functional unit, ensuring an integrated excitatory and exocytotic response to the signals that control insulin secretion.
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Affiliation(s)
- Patrick E MacDonald
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada.
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25
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Fu ZY, Wang YP, Chen Y. Observation of insulin exocytosis by a pancreatic β cell line with total internal reflection fluorescence microscopy. ACTA ACUST UNITED AC 2011; 26:60-3. [PMID: 21496425 DOI: 10.1016/s1001-9294(11)60021-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Zhao-ying Fu
- College of Medicine, Yanan University, Yanan 716000, China.
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26
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Dai XQ, Plummer G, Casimir M, Kang Y, Hajmrle C, Gaisano HY, Manning Fox JE, MacDonald PE. SUMOylation regulates insulin exocytosis downstream of secretory granule docking in rodents and humans. Diabetes 2011; 60:838-47. [PMID: 21266332 PMCID: PMC3046844 DOI: 10.2337/db10-0440] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
OBJECTIVE The reversible attachment of small ubiquitin-like modifier (SUMO) proteins controls target localization and function. We examined an acute role for the SUMOylation pathway in downstream events mediating insulin secretion. RESEARCH DESIGN AND METHODS We studied islets and β-cells from mice and human donors, as well as INS-1 832/13 cells. Insulin secretion, intracellular Ca(2+), and β-cell exocytosis were monitored after manipulation of the SUMOylation machinery. Granule localization was imaged by total internal reflection fluorescence and electron microscopy; immunoprecipitation and Western blotting were used to examine the soluble NSF attachment receptor (SNARE) complex formation and SUMO1 interaction with synaptotagmin VII. RESULTS SUMO1 impairs glucose-stimulated insulin secretion by blunting the β-cell exocytotic response to Ca(2+). The effect of SUMO1 to impair insulin secretion and β-cell exocytosis is rapid and does not require altered gene expression or insulin content, is downstream of granule docking at the plasma membrane, and is dependent on SUMO-conjugation because the deSUMOylating enzyme, sentrin/SUMO-specific protease (SENP)-1, rescues exocytosis. SUMO1 coimmunoprecipitates with the Ca(2+) sensor synaptotagmin VII, and this is transiently lost upon glucose stimulation. SENP1 overexpression also disrupts the association of SUMO1 with synaptotagmin VII and mimics the effect of glucose to enhance exocytosis. Conversely, SENP1 knockdown impairs exocytosis at stimulatory glucose levels and blunts glucose-dependent insulin secretion from mouse and human islets. CONCLUSIONS SUMOylation acutely regulates insulin secretion by the direct and reversible inhibition of β-cell exocytosis in response to intracellular Ca(2+) elevation. The SUMO protease, SENP1, is required for glucose-dependent insulin secretion.
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Affiliation(s)
- Xiao-Qing Dai
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Greg Plummer
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Marina Casimir
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Youhou Kang
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Catherine Hajmrle
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | | | - Jocelyn E. Manning Fox
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Patrick E. MacDonald
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
- Corresponding author: Patrick E. MacDonald,
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27
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Cell-wide analysis of secretory granule dynamics in three dimensions in living pancreatic beta-cells: evidence against a role for AMPK-dependent phosphorylation of KLC1 at Ser517/Ser520 in glucose-stimulated insulin granule movement. Biochem Soc Trans 2010; 38:205-8. [PMID: 20074060 DOI: 10.1042/bst0380205] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glucose-stimulated insulin secretion from pancreatic beta-cells requires the kinesin-1/Kif5B-mediated transport of insulin granules along microtubules. 5'-AMPK (5'-AMP-activated protein kinase) is a heterotrimeric serine/threonine kinase which is activated in beta-cells at low glucose concentrations, but inhibited as glucose levels increase. Active AMPK blocks glucose-stimulated insulin secretion and the recruitment of insulin granules to the cell surface, suggesting motor proteins may be targets for this kinase. While both kinesin-1/Kif5B and KLC1 (kinesin light chain-1) contain consensus AMPK phosphorylation sites (Thr(693) and Ser(520), respectively) only recombinant GST (glutathione transferase)-KLC1 was phosphorylated by purified AMPK in vitro. To test the hypothesis that phosphorylation at this site may modulate kinesin-1-mediated granule movement, we developed an approach to study the dynamics of all the resolvable granules within a cell in three dimensions. This cell-wide approach revealed that the number of longer excursions (>10 mum) increased significantly in response to elevated glucose concentration (30 versus 3 mM) in control MIN6 beta-cells. However, similar changes were seen in cells overexpressing wild-type KLC1, phosphomimetic (S517D/S520D) or non-phosphorylatable (S517A/S520A) mutants of KLC1. Thus, changes in the phosphorylation state of KLC1 at Ser(517)/Ser(520) seem unlikely to affect motor function.
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28
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Ram S, Prabhat P, Chao J, Ward ES, Ober RJ. 3D single molecule tracking of quantum-dot labeled antibody molecules using multifocal plane microscopy. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2010; 7575:75750J. [PMID: 22916318 PMCID: PMC3423200 DOI: 10.1117/12.848940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Single molecule tracking in three dimensions (3D) in a live cell environment promises to reveal important new insights into cell biological mechanisms. However, classical microscopy techniques suffer from poor depth discrimination which severely limits single molecule tracking in 3D with high temporal and spatial resolution. We introduced a novel imaging modality, multifocal plane microscopy (MUM) for the study of subcellular dynamics in 3D. We have shown that MUM provides a powerful approach with which single molecules can be tracked in 3D in live cells. MUM allows for the simultaneous imaging at different focal planes, thereby ensuring that trajectories can be imaged continuously at high temporal resolution. A critical requirement for 3D single molecule tracking as well as localization based 3D super-resolution imaging is high 3D localization accuracy. MUM overcomes the depth discrimination problem of classical microscopy based approaches and supports high accuracy 3D localization of singe molecule/particles. In this way, MUM opens the way for high precision 3D single molecule tracking and 3D super-resolution imaging within a live cell environment. We have used MUM to reveal complex intracellular pathways that could not be imaged with classical approaches. In particular we have tracked quantum dot labeled antibody molecules in the exo/endocytic pathway from the cell interior to the plasma membrane at the single molecule level. Here, we present a brief review of these results.
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Affiliation(s)
- Sripad Ram
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX, 75390
| | - Prashant Prabhat
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX, 75390
- Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX, 75083
| | - Jerry Chao
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX, 75390
- Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX, 75083
| | - E. Sally Ward
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX, 75390
| | - Raimund J. Ober
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX, 75390
- Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX, 75083
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Piquer S, Casas S, Quesada I, Nadal A, Julià M, Novials A, Gomis R. Role of iduronate-2-sulfatase in glucose-stimulated insulin secretion by activation of exocytosis. Am J Physiol Endocrinol Metab 2009; 297:E793-801. [PMID: 19602578 DOI: 10.1152/ajpendo.90878.2008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Iduronate-2-sulfatase (IDS) is a lysosomal enzyme expressed in pancreatic islets responsible for the degradation of proteoglycans such as perlecan and dermatan sulfate. Previous findings of our group demonstrated the involvement of IDS in the normal pathway of lysosomal degradation of secretory peptides, suggesting a role of this enzyme in beta-cell secretory functionality. The present study was undertaken to characterize the effect of IDS overexpression on insulin release. INS1E cells were transiently transfected with a construct encoding human IDS (hIDS). hIDS overexpression was associated with a gain of function detected by a reduction in heparan sulfate content. hIDS potentiated the glucose-stimulated insulin secretory response compared with controls (61%) with no changes in insulin mRNA levels or insulin peptide content. Results on quantification of the exocytotic process showed a significant increase in hIDS-transfected cells compared with controls. Furthermore, ultramorphological analysis demonstrated an increase in the number of granules in the immediate vicinity of the plasma membrane in hIDS-transfected cells and a decrease in total vesicles per square micrometer. hIDS overexpression induced phosphorylation of protein kinase C (PKC) alpha and its newly myristoylated alanine-rich C kinase substrate, MARCKS. We conclude that IDS has a role in glucose-stimulated insulin secretion via a mechanism that involves the activation of exocytosis through phosphorylation of PKCalpha and MARCKS.
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Affiliation(s)
- S Piquer
- Endocrinology and Diabetes Unit, Laboratory of Diabetes and Obesity, Institut d' Investigacions Biomediques August Pi iSunyer-Fundació Clínic, Hospital Clínic, Barcelona, Spain
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Pigeau GM, Kolic J, Ball BJ, Hoppa MB, Wang YW, Rückle T, Woo M, Manning Fox JE, MacDonald PE. Insulin granule recruitment and exocytosis is dependent on p110gamma in insulinoma and human beta-cells. Diabetes 2009; 58:2084-92. [PMID: 19549714 PMCID: PMC2731529 DOI: 10.2337/db08-1371] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
OBJECTIVE Phosphatidylinositol 3-OH kinase (PI3K) has a long-recognized role in beta-cell mass regulation and gene transcription and is implicated in the modulation of insulin secretion. The role of nontyrosine kinase receptor-activated PI3K isoforms is largely unexplored. We therefore investigated the role of the G-protein-coupled PI3Kgamma and its catalytic subunit p110gamma in the regulation of insulin granule recruitment and exocytosis. RESEARCH DESIGN AND METHODS The expression of p110gamma was knocked down by small-interfering RNA, and p110gamma activity was selectively inhibited with AS605240 (40 nmol/l). Exocytosis and granule recruitment was monitored by islet perifusion, whole-cell capacitance, total internal reflection fluorescence microscopy, and electron microscopy in INS-1 and human beta-cells. Cortical F-actin was examined in INS-1 cells and human islets and in mouse beta-cells lacking the phosphatase and tensin homolog (PTEN). RESULTS Knockdown or inhibition of p110gamma markedly blunted depolarization-induced insulin secretion and exocytosis and ablated the exocytotic response to direct Ca(2+) infusion. This resulted from reduced granule localization to the plasma membrane and was associated with increased cortical F-actin. Inhibition of p110gamma had no effect on F-actin in beta-cells lacking PTEN. Finally, the effect of p110gamma inhibition on granule localization and exocytosis could be rapidly reversed by agents that promote actin depolymerization. CONCLUSIONS The G-protein-coupled PI3Kgamma is an important determinant of secretory granule trafficking to the plasma membrane, at least in part through the negative regulation of cortical F-actin. Thus, p110gamma activity plays an important role in maintaining a membrane-docked, readily releasable pool of secretory granules in insulinoma and human beta-cells.
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Affiliation(s)
- Gary M. Pigeau
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Jelena Kolic
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Brandon J. Ball
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Michael B. Hoppa
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Headington, Oxford, U.K
| | - Ying W. Wang
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Thomas Rückle
- Geneva Research Center, Merck Serono, Geneva, Switzerland
| | - Minna Woo
- Department of Medicine, Medical Biophysics, Institute of Medical Science, Ontario Cancer Institute, University of Toronto, Toronto, Ontario, Canada
| | - Jocelyn E. Manning Fox
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Patrick E. MacDonald
- Department of Pharmacology and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
- Corresponding author: Patrick E. MacDonald,
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31
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Pedersen MG, Corradin A, Toffolo GM, Cobelli C. A subcellular model of glucose-stimulated pancreatic insulin secretion. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2008; 366:3525-3543. [PMID: 18653438 DOI: 10.1098/rsta.2008.0120] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
When glucose is raised from a basal to stimulating level, the pancreatic islets respond with a typical biphasic insulin secretion pattern. Moreover, the pancreas is able to recognize the rate of change of the glucose concentration. We present a relatively simple model of insulin secretion from pancreatic beta-cells, yet founded on solid physiological grounds and capable of reproducing a series of secretion patterns from perfused pancreases as well as from stimulated islets. The model includes the notion of distinct pools of granules as well as mechanisms such as mobilization, priming, exocytosis and kiss-and-run. Based on experimental data, we suggest that the individual beta-cells activate at different glucose concentrations. The model reproduces most of the data it was tested against very well, and can therefore serve as a general model of glucose-stimulated insulin secretion. Simulations predict that the effect of an increased frequency of kiss-and-run exocytotic events is a reduction in insulin secretion without modification of the qualitative pattern. Our model also appears to be the first physiology-based one to reproduce the staircase experiment, which underlies 'derivative control', i.e. the pancreatic capacity of measuring the rate of change of the glucose concentration.
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Affiliation(s)
- Morten Gram Pedersen
- Department of Information Engineering, University of Padova, Via Gradenigo 6/A, 35131 Padova, Italy
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32
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High accuracy 3D quantum dot tracking with multifocal plane microscopy for the study of fast intracellular dynamics in live cells. Biophys J 2008; 95:6025-43. [PMID: 18835896 DOI: 10.1529/biophysj.108.140392] [Citation(s) in RCA: 215] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Single particle tracking in three dimensions in a live cell environment holds the promise of revealing important new biological insights. However, conventional microscopy-based imaging techniques are not well suited for fast three-dimensional (3D) tracking of single particles in cells. Previously we developed an imaging modality multifocal plane microscopy (MUM) to image fast intracellular dynamics in three dimensions in live cells. Here, we introduce an algorithm, the MUM localization algorithm (MUMLA), to determine the 3D position of a point source that is imaged using MUM. We validate MUMLA through simulated and experimental data and show that the 3D position of quantum dots can be determined over a wide spatial range. We demonstrate that MUMLA indeed provides the best possible accuracy with which the 3D position can be determined. Our analysis shows that MUM overcomes the poor depth discrimination of the conventional microscope, and thereby paves the way for high accuracy tracking of nanoparticles in a live cell environment. Here, using MUM and MUMLA we report for the first time the full 3D trajectories of QD-labeled antibody molecules undergoing endocytosis in live cells from the plasma membrane to the sorting endosome deep inside the cell.
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MacDonald PE, Rorsman P. The Ins and Outs of Secretion from Pancreatic β-Cells: Control of Single-Vesicle Exo- and Endocytosis. Physiology (Bethesda) 2007; 22:113-21. [PMID: 17420302 DOI: 10.1152/physiol.00047.2006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exocytosis of insulin-containing secretory vesicles in pancreatic β-cells is crucial to maintenance of plasma glucose levels. They fuse with the plasma membrane in a regulated manner to release their contents and are subsequently recaptured either intact or through conventional clathrin-mediated endocytosis. Here, we discuss these mechanisms in β-cells at the single-vesicle level.
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Affiliation(s)
- Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada.
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34
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Prabhat P, Gan Z, Chao J, Ram S, Vaccaro C, Gibbons S, Ober RJ, Ward ES. Elucidation of intracellular recycling pathways leading to exocytosis of the Fc receptor, FcRn, by using multifocal plane microscopy. Proc Natl Acad Sci U S A 2007; 104:5889-94. [PMID: 17384151 PMCID: PMC1851587 DOI: 10.1073/pnas.0700337104] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The intracellular events on the recycling pathway that lead from sorting endosomes to exocytosis at the plasma membrane are central to cellular function. However, despite intensive study, these processes are poorly characterized in spatial and dynamic terms. The primary reason for this is that, to date, it has not been possible to visualize rapidly moving intracellular compartments in three dimensions in cells. Here, we use a recently developed imaging setup in which multiple planes can be simultaneously imaged within the cell in conjunction with visualization of the plasma membrane plane by using total internal reflection fluorescence microscopy. This has allowed us to track and characterize intracellular events on the recycling pathway that lead to exocytosis of the MHC Class I-related receptor, FcRn. We observe both direct delivery of tubular and vesicular transport containers (TCs) from sorting endosomes to exocytic sites at the plasma membrane, and indirect pathways in which TCs that are not in proximity to sorting endosomes undergo exocytosis. TCs can also interact with different sorting endosomes before exocytosis. Our data provide insight into the intracellular events that precede exocytic fusion.
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Affiliation(s)
- Prashant Prabhat
- *Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
- Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75080
| | - Zhuo Gan
- *Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
| | - Jerry Chao
- *Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
- Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75080
| | - Sripad Ram
- *Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
| | - Carlos Vaccaro
- *Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
| | - Steven Gibbons
- *Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
| | - Raimund J. Ober
- *Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
- Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75080
- To whom correspondence may be addressed. E-mail: or
| | - E. Sally Ward
- *Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and
- To whom correspondence may be addressed. E-mail: or
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