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Tsuyama T, Sato Y, Yoshizawa T, Matsuoka T, Yamagata K. Hypoxia causes pancreatic β-cell dysfunction and impairs insulin secretion by activating the transcriptional repressor BHLHE40. EMBO Rep 2023; 24:e56227. [PMID: 37341148 PMCID: PMC10398664 DOI: 10.15252/embr.202256227] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 05/28/2023] [Accepted: 06/04/2023] [Indexed: 06/22/2023] Open
Abstract
Hypoxia can occur in pancreatic β-cells in type 2 diabetes. Although hypoxia exerts deleterious effects on β-cell function, the associated mechanisms are largely unknown. Here, we show that the transcriptional repressor basic helix-loop-helix family member e40 (BHLHE40) is highly induced in hypoxic mouse and human β-cells and suppresses insulin secretion. Conversely, BHLHE40 deficiency in hypoxic MIN6 cells or β-cells of ob/ob mice reverses defects in insulin secretion. Mechanistically, BHLHE40 represses the expression of Mafa, encoding the transcription factor musculoaponeurotic fibrosarcoma oncogene family A (MAFA), by attenuating the binding of pancreas/duodenum homeobox protein 1 (PDX1) to its enhancer region. Impaired insulin secretion in hypoxic β-cells was recovered by MAFA re-expression. Collectively, our work identifies BHLHE40 as a key hypoxia-induced transcriptional repressor in β-cells that inhibit insulin secretion by suppressing MAFA expression.
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Affiliation(s)
- Tomonori Tsuyama
- Center for Metabolic Regulation of Healthy Aging (CMHA), Faculty of Life SciencesKumamoto UniversityKumamotoJapan
| | - Yoshifumi Sato
- Department of Medical Biochemistry, Faculty of Life SciencesKumamoto UniversityKumamotoJapan
| | - Tatsuya Yoshizawa
- Department of Medical Biochemistry, Faculty of Life SciencesKumamoto UniversityKumamotoJapan
| | - Takaaki Matsuoka
- First Department of Internal MedicineWakayama Medical UniversityWakayamaJapan
| | - Kazuya Yamagata
- Center for Metabolic Regulation of Healthy Aging (CMHA), Faculty of Life SciencesKumamoto UniversityKumamotoJapan
- Department of Medical Biochemistry, Faculty of Life SciencesKumamoto UniversityKumamotoJapan
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2
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Rahman MM, Pathak A, Schueler KL, Alsharif H, Michl A, Alexander J, Kim JA, Bhatnagar S. Genetic ablation of synaptotagmin-9 alters tomosyn-1 function to increase insulin secretion from pancreatic β-cells improving glucose clearance. FASEB J 2023; 37:e23075. [PMID: 37432648 PMCID: PMC10348599 DOI: 10.1096/fj.202300291rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 06/19/2023] [Accepted: 06/22/2023] [Indexed: 07/12/2023]
Abstract
Stimulus-coupled insulin secretion from the pancreatic islet β-cells involves the fusion of insulin granules to the plasma membrane (PM) via SNARE complex formation-a cellular process key for maintaining whole-body glucose homeostasis. Less is known about the role of endogenous inhibitors of SNARE complexes in insulin secretion. We show that an insulin granule protein synaptotagmin-9 (Syt9) deletion in mice increased glucose clearance and plasma insulin levels without affecting insulin action compared to the control mice. Upon glucose stimulation, increased biphasic and static insulin secretion were observed from ex vivo islets due to Syt9 loss. Syt9 colocalizes and binds with tomosyn-1 and the PM syntaxin-1A (Stx1A); Stx1A is required for forming SNARE complexes. Syt9 knockdown reduced tomosyn-1 protein abundance via proteasomal degradation and binding of tomosyn-1 to Stx1A. Furthermore, Stx1A-SNARE complex formation was increased, implicating Syt9-tomosyn-1-Stx1A complex is inhibitory in insulin secretion. Rescuing tomosyn-1 blocked the Syt9-knockdown-mediated increases in insulin secretion. This shows that the inhibitory effects of Syt9 on insulin secretion are mediated by tomosyn-1. We report a molecular mechanism by which β-cells modulate their secretory capacity rendering insulin granules nonfusogenic by forming the Syt9-tomosyn-1-Stx1A complex. Altogether, Syt9 loss in β-cells decreases tomosyn-1 protein abundance, increasing the formation of Stx1A-SNARE complexes, insulin secretion, and glucose clearance. These outcomes differ from the previously published work that identified Syt9 has either a positive or no effect of Syt9 on insulin secretion. Future work using β-cell-specific deletion of Syt9 mice is key for establishing the role of Syt9 in insulin secretion.
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Affiliation(s)
- Md Mostafizur Rahman
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Asmita Pathak
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | | | - Haifa Alsharif
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Ava Michl
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Justin Alexander
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Jeong-A Kim
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
| | - Sushant Bhatnagar
- Heersink School of Medicine, Division of Endocrinology, Diabetes, & Metabolism, Comprehensive Diabetes Center, University of Alabama, Birmingham, AL, 35294
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3
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Ramanadham S, Turk J, Bhatnagar S. Noncanonical Regulation of cAMP-Dependent Insulin Secretion and Its Implications in Type 2 Diabetes. Compr Physiol 2023; 13:5023-5049. [PMID: 37358504 PMCID: PMC10809800 DOI: 10.1002/cphy.c220031] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
Abstract
Impaired glucose tolerance (IGT) and β-cell dysfunction in insulin resistance associated with obesity lead to type 2 diabetes (T2D). Glucose-stimulated insulin secretion (GSIS) from β-cells occurs via a canonical pathway that involves glucose metabolism, ATP generation, inactivation of K ATP channels, plasma membrane depolarization, and increases in cytosolic concentrations of [Ca 2+ ] c . However, optimal insulin secretion requires amplification of GSIS by increases in cyclic adenosine monophosphate (cAMP) signaling. The cAMP effectors protein kinase A (PKA) and exchange factor activated by cyclic-AMP (Epac) regulate membrane depolarization, gene expression, and trafficking and fusion of insulin granules to the plasma membrane for amplifying GSIS. The widely recognized lipid signaling generated within β-cells by the β-isoform of Ca 2+ -independent phospholipase A 2 enzyme (iPLA 2 β) participates in cAMP-stimulated insulin secretion (cSIS). Recent work has identified the role of a G-protein coupled receptor (GPCR) activated signaling by the complement 1q like-3 (C1ql3) secreted protein in inhibiting cSIS. In the IGT state, cSIS is attenuated, and the β-cell function is reduced. Interestingly, while β-cell-specific deletion of iPLA 2 β reduces cAMP-mediated amplification of GSIS, the loss of iPLA 2 β in macrophages (MØ) confers protection against the development of glucose intolerance associated with diet-induced obesity (DIO). In this article, we discuss canonical (glucose and cAMP) and novel noncanonical (iPLA 2 β and C1ql3) pathways and how they may affect β-cell (dys)function in the context of impaired glucose intolerance associated with obesity and T2D. In conclusion, we provide a perspective that in IGT states, targeting noncanonical pathways along with canonical pathways could be a more comprehensive approach for restoring β-cell function in T2D. © 2023 American Physiological Society. Compr Physiol 13:5023-5049, 2023.
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Affiliation(s)
- Sasanka Ramanadham
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Alabama, USA
- Comprehensive Diabetes Center, University of Alabama at Birmingham, Alabama, USA
| | - John Turk
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Sushant Bhatnagar
- Comprehensive Diabetes Center, University of Alabama at Birmingham, Alabama, USA
- Department of Medicine, University of Alabama at Birmingham, Alabama, USA
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4
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Ho KH, Jayathilake A, Yagan M, Nour A, Osipovich AB, Magnuson MA, Gu G, Kaverina I. CAMSAP2 localizes to the Golgi in islet β-cells and facilitates Golgi-ER trafficking. iScience 2023; 26:105938. [PMID: 36718359 PMCID: PMC9883185 DOI: 10.1016/j.isci.2023.105938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 12/07/2022] [Accepted: 01/04/2023] [Indexed: 01/09/2023] Open
Abstract
Glucose stimulation induces the remodeling of microtubules, which potentiates insulin secretion in pancreatic β-cells. CAMSAP2 binds to microtubule minus ends to stabilize microtubules in several cultured clonal cells. Here, we report that the knockdown of CAMSAP2 in primary β-cells reduces total insulin content and attenuates GSIS without affecting the releasability of insulin vesicles. Surprisingly, CAMSAP2 knockdown does not change microtubule stability. Unlike in cultured insulinoma cells, CAMSAP2 in primary β-cells predominantly localizes to the Golgi apparatus instead of microtubule minus ends. This novel localization is specific to primary β- but not α-cells and is independent of microtubule binding. Consistent with its specific localization at the Golgi, CAMSAP2 promotes efficient Golgi-ER trafficking in primary β-cells. Moreover, primary β-cells and insulinoma cells likely express different CAMSAP2 isoforms. We propose that a novel CAMSAP2 isoform in primary β-cells has a non-canonical function, which promotes Golgi-ER trafficking to support efficient production of insulin and secretion.
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Affiliation(s)
- Kung-Hsien Ho
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Anissa Jayathilake
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Mahircan Yagan
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Aisha Nour
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Anna B. Osipovich
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Mark A. Magnuson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Guoqiang Gu
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
| | - Irina Kaverina
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN, USA
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5
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Yang X, Tu W, Gao X, Zhang Q, Guan J, Zhang J. Functional regulation of syntaxin-1: An underlying mechanism mediating exocytosis in neuroendocrine cells. Front Endocrinol (Lausanne) 2023; 14:1096365. [PMID: 36742381 PMCID: PMC9892835 DOI: 10.3389/fendo.2023.1096365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Accepted: 01/05/2023] [Indexed: 01/20/2023] Open
Abstract
The fusion of the secretory vesicle with the plasma membrane requires the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein complexes formed by synaptobrevin, syntaxin-1, and SNAP-25. Within the pathway leading to exocytosis, the transitions between the "open" and "closed" conformations of syntaxin-1 function as a switch for the fusion of vesicles with the plasma membranes; rapid assembly and disassembly of syntaxin-1 clusters on the plasma membrane provide docking and fusion sites for secretory vesicles in neuroendocrine cells; and the fully zippered trans-SNARE complex, which requires the orderly, rapid and accurate binding of syntaxin-1 to other SNARE proteins, play key roles in triggering fusion. All of these reactions that affect exocytosis under physiological conditions are tightly regulated by multiple factors. Here, we review the current evidence for the involvement of syntaxin-1 in the mechanism of neuroendocrine cell exocytosis, discuss the roles of multiple factors such as proteins, lipids, protein kinases, drugs, and toxins in SNARE complex-mediated membrane fusion, and present an overview of syntaxin-1 mutation-associated diseases with a view to developing novel mechanistic therapeutic targets for the treatment of neuroendocrine disorders.
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Affiliation(s)
- Xinquan Yang
- Anesthesia and Perioperative Medicine laboratory, the Affiliated Lianyungang Hospital of Jiangsu University, Lianyungang, China
| | - Weifeng Tu
- Faculty of Anesthesioloy, Suzhou Hospital Affiliated to Medical School of Nanjing University, Suzhou, China
| | - Xuzhu Gao
- Department of Central Laboratory, Lianyungang Hospital Affiliated to Jiangsu University, Lianyungang, China
| | - Qi Zhang
- Anesthesia and Perioperative Medicine laboratory, the Affiliated Lianyungang Hospital of Jiangsu University, Lianyungang, China
| | - Jinping Guan
- Anesthesia and Perioperative Medicine laboratory, the Affiliated Lianyungang Hospital of Jiangsu University, Lianyungang, China
| | - Junlong Zhang
- Anesthesia and Perioperative Medicine laboratory, the Affiliated Lianyungang Hospital of Jiangsu University, Lianyungang, China
- *Correspondence: Junlong Zhang,
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6
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Palfreyman MT, West SE, Jorgensen EM. SNARE Proteins in Synaptic Vesicle Fusion. ADVANCES IN NEUROBIOLOGY 2023; 33:63-118. [PMID: 37615864 DOI: 10.1007/978-3-031-34229-5_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Neurotransmitters are stored in small membrane-bound vesicles at synapses; a subset of synaptic vesicles is docked at release sites. Fusion of docked vesicles with the plasma membrane releases neurotransmitters. Membrane fusion at synapses, as well as all trafficking steps of the secretory pathway, is mediated by SNARE proteins. The SNAREs are the minimal fusion machinery. They zipper from N-termini to membrane-anchored C-termini to form a 4-helix bundle that forces the apposed membranes to fuse. At synapses, the SNAREs comprise a single helix from syntaxin and synaptobrevin; SNAP-25 contributes the other two helices to complete the bundle. Unc13 mediates synaptic vesicle docking and converts syntaxin into the permissive "open" configuration. The SM protein, Unc18, is required to initiate and proofread SNARE assembly. The SNAREs are then held in a half-zippered state by synaptotagmin and complexin. Calcium removes the synaptotagmin and complexin block, and the SNAREs drive vesicle fusion. After fusion, NSF and alpha-SNAP unwind the SNAREs and thereby recharge the system for further rounds of fusion. In this chapter, we will describe the discovery of the SNAREs, their relevant structural features, models for their function, and the central role of Unc18. In addition, we will touch upon the regulation of SNARE complex formation by Unc13, complexin, and synaptotagmin.
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Affiliation(s)
- Mark T Palfreyman
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Sam E West
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Erik M Jorgensen
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA.
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7
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Li A, Zhang X, Singla J, White K, Loconte V, Hu C, Zhang C, Li S, Li W, Francis JP, Wang C, Sali A, Sun L, He X, Stevens RC. Auto-segmentation and time-dependent systematic analysis of mesoscale cellular structure in β-cells during insulin secretion. PLoS One 2022; 17:e0265567. [PMID: 35324950 PMCID: PMC8947144 DOI: 10.1371/journal.pone.0265567] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 03/03/2022] [Indexed: 02/07/2023] Open
Abstract
The mesoscale description of the subcellular organization informs about cellular mechanisms in disease state. However, applications of soft X-ray tomography (SXT), an important approach for characterizing organelle organization, are limited by labor-intensive manual segmentation. Here we report a pipeline for automated segmentation and systematic analysis of SXT tomograms. Our approach combines semantic and first-applied instance segmentation to produce separate organelle masks with high Dice and Recall indexes, followed by analysis of organelle localization based on the radial distribution function. We demonstrated this technique by investigating the organization of INS-1E pancreatic β-cell organization under different treatments at multiple time points. Consistent with a previous analysis of a similar dataset, our results revealed the impact of glucose stimulation on the localization and molecular density of insulin vesicles and mitochondria. This pipeline can be extended to SXT tomograms of any cell type to shed light on the subcellular rearrangements under different drug treatments.
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Affiliation(s)
- Angdi Li
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xiangyi Zhang
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Jitin Singla
- Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA, United States of America
| | - Kate White
- Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA, United States of America
| | - Valentina Loconte
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Chuanyang Hu
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Chuyu Zhang
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Shuailin Li
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Weimin Li
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - John Paul Francis
- Department of Computer Science, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA, United States of America
| | - Chenxi Wang
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Andrej Sali
- California Institute for Quantitative Biosciences, Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, United States of America
| | - Liping Sun
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- * E-mail: (LS); (XH); (RCS)
| | - Xuming He
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
- Shanghai Engineering Research Center of Intelligent Vision and Imaging, Shanghai, China
- * E-mail: (LS); (XH); (RCS)
| | - Raymond C. Stevens
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA, United States of America
- * E-mail: (LS); (XH); (RCS)
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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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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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10
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Ferri G, Pesce L, Tesi M, Marchetti P, Cardarelli F. β-Cell Pathophysiology: A Review of Advanced Optical Microscopy Applications. Int J Mol Sci 2021; 22:ijms222312820. [PMID: 34884624 PMCID: PMC8657725 DOI: 10.3390/ijms222312820] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 11/24/2021] [Accepted: 11/24/2021] [Indexed: 11/30/2022] Open
Abstract
β-cells convert glucose (input) resulting in the controlled release of insulin (output), which in turn has the role to maintain glucose homeostasis. β-cell function is regulated by a complex interplay between the metabolic processing of the input, its transformation into second-messenger signals, and final mobilization of insulin-containing granules towards secretion of the output. Failure at any level in this process marks β-cell dysfunction in diabetes, thus making β-cells obvious potential targets for therapeutic purposes. Addressing quantitatively β-cell (dys)function at the molecular level in living samples requires probing simultaneously the spatial and temporal dimensions at the proper resolution. To this aim, an increasing amount of research efforts are exploiting the potentiality of biophysical techniques. In particular, using excitation light in the visible/infrared range, a number of optical-microscopy-based approaches have been tailored to the study of β-cell-(dys)function at the molecular level, either in label-free mode (i.e., exploiting intrinsic autofluorescence of cells) or by the use of organic/genetically-encoded fluorescent probes. Here, relevant examples from the literature are reviewed and discussed. Based on this, new potential lines of development in the field are drawn.
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Affiliation(s)
- Gianmarco Ferri
- NEST Laboratory, Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; (G.F.); (L.P.)
| | - Luca Pesce
- NEST Laboratory, Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; (G.F.); (L.P.)
| | - Marta Tesi
- Islet Cell Laboratory, Department of Clinical and Experimental Medicine, University of Pisa, 56127 Pisa, Italy; (M.T.); (P.M.)
| | - Piero Marchetti
- Islet Cell Laboratory, Department of Clinical and Experimental Medicine, University of Pisa, 56127 Pisa, Italy; (M.T.); (P.M.)
| | - Francesco Cardarelli
- NEST Laboratory, Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; (G.F.); (L.P.)
- Correspondence:
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11
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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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12
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Yau B, Hocking S, Andrikopoulos S, Kebede MA. Targeting the insulin granule for modulation of insulin exocytosis. Biochem Pharmacol 2021; 194:114821. [PMID: 34748819 DOI: 10.1016/j.bcp.2021.114821] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/29/2021] [Accepted: 11/02/2021] [Indexed: 02/08/2023]
Abstract
The pancreatic β-cells control insulin secretion in the body to regulate glucose homeostasis, and β-cell stress and dysfunction is characteristic of Type 2 Diabetes. Pharmacological targeting of the β-cell to increase insulin secretion is typically utilised, however, extended use of common drugs such as sulfonylureas are known to result in secondary failure. Moreover, there is evidence they may induce β-cell failure in the long term. Within β-cells, insulin secretory granules (ISG) serve as compartments to store, process and traffic insulin for exocytosis. There is now growing evidence that ISG exist in multiple populations, distinct in their protein composition, motility, age, and capacity for secretion. In this review, we discuss the implications of a heterogenous ISG population in β-cells and highlight the need for more understanding into how unique ISG populations may be targeted in anti-diabetic therapies.
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Affiliation(s)
- Belinda Yau
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, Australia; Charles Perkins Centre, The University of Sydney, Camperdown, NSW, Australia.
| | - Samantha Hocking
- Charles Perkins Centre, The University of Sydney, Camperdown, NSW, Australia; Central Clinical School, Faculty of Medicine and Health and Department of Endocrinology Royal Prince Alfred Hospital, NSW, Australia
| | | | - Melkam A Kebede
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, Australia; Charles Perkins Centre, The University of Sydney, Camperdown, NSW, Australia
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13
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Gaus B, Brüning D, Hatlapatka K, Rustenbeck I. Changes in granule mobility and age contribute to changes in insulin secretion after desensitization or rest. BMJ Open Diabetes Res Care 2021; 9:9/1/e002394. [PMID: 34620619 PMCID: PMC8499263 DOI: 10.1136/bmjdrc-2021-002394] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 09/14/2021] [Indexed: 12/17/2022] Open
Abstract
INTRODUCTION Functional impairment of the stimulus secretion coupling in pancreatic beta cells is an essential component of type 2 diabetes. It is known that prolonged stimulation desensitizes the secretion of insulin and thus contributes to beta cell dysfunction. Beta cell rest, in contrast, was shown to enhance the secretory response. Here, the underlying mechanisms were investigated. RESEARCH DESIGN AND METHODS To characterize the consequences of desensitization or rest for the number and mobility of submembrane granules, insulin-secreting MIN6 cells were desensitized by 18-hour culture with 500 µM tolbutamide or rested by 18-hour culture with 1 µM clonidine. The granules were labeled by hIns-EGFP or hIns-DsRed E5, imaged by TIRF microscopy of the cell footprint area and analyzed with an observer-independent program. Additionally, the insulin content and secretion were measured. RESULTS Concurrent with the insulin content, submembrane granules were only slightly reduced after desensitization but markedly increased after rest. Both types of pretreatment diminished arrivals and departures of granules in the submembrane space and increased the proportion of immobile long-term resident granules, but desensitization lowered and rest increased the number of exocytoses, in parallel with the effect on insulin secretion. Labeling with hIns-DsRed E5 ('timer') showed that desensitization did not affect the proportion of aged granules, whereas rest increased it. Aged granules showed a high mobility and made up only a minority of long-term residents. Long-term resident granules were more numerous after rest and had a lower lateral mobility, suggesting a firmer attachment to the membrane. CONCLUSION The number, mobility and age of submembrane granules reflect the preceding functional states of insulin-secreting cells. Representing the pool of releasable granules, their quantity and quality may thus form part of the beta cell memory on renewed stimulation.
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Affiliation(s)
- Bastian Gaus
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Dennis Brüning
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
| | - Kathrin Hatlapatka
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
- DHD-Consulting GmbH, Hildesheim, Germany
| | - Ingo Rustenbeck
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Technische Universität Braunschweig, Braunschweig, Germany
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14
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Kemter E, Müller A, Neukam M, Ivanova A, Klymiuk N, Renner S, Yang K, Broichhagen J, Kurome M, Zakhartchenko V, Kessler B, Knoch KP, Bickle M, Ludwig B, Johnsson K, Lickert H, Kurth T, Wolf E, Solimena M. Sequential in vivo labeling of insulin secretory granule pools in INS- SNAP transgenic pigs. Proc Natl Acad Sci U S A 2021; 118:e2107665118. [PMID: 34508004 PMCID: PMC8449372 DOI: 10.1073/pnas.2107665118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2021] [Indexed: 12/16/2022] Open
Abstract
β cells produce, store, and secrete insulin upon elevated blood glucose levels. Insulin secretion is a highly regulated process. The probability for insulin secretory granules to undergo fusion with the plasma membrane or being degraded is correlated with their age. However, the molecular features and stimuli connected to this behavior have not yet been fully understood. Furthermore, our understanding of β cell function is mostly derived from studies of ex vivo isolated islets in rodent models. To overcome this translational gap and study insulin secretory granule turnover in vivo, we have generated a transgenic pig model with the SNAP-tag fused to insulin. We demonstrate the correct targeting and processing of the tagged insulin and normal glycemic control of the pig model. Furthermore, we show specific single- and dual-color granular labeling of in vivo-labeled pig pancreas. This model may provide unprecedented insights into the in vivo insulin secretory granule behavior in an animal close to humans.
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Affiliation(s)
- Elisabeth Kemter
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- German Center for Diabetes Research, 85764 Neuherberg, Germany
| | - Andreas Müller
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Martin Neukam
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Anna Ivanova
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Nikolai Klymiuk
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
| | - Simone Renner
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- German Center for Diabetes Research, 85764 Neuherberg, Germany
| | - Kaiyuan Yang
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Institute of Diabetes and Regeneration Research, Helmholtz Diabetes Center, Helmholtz Center Munich, 85764 Neuherberg, Germany
| | - Johannes Broichhagen
- Department of Chemical Biology, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
- Chemical Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, 13125 Berlin, Germany
| | - Mayuko Kurome
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
| | - Valeri Zakhartchenko
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
| | - Barbara Kessler
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
| | - Klaus-Peter Knoch
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
| | - Marc Bickle
- Technology Development Studio (TDS), Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Barbara Ludwig
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Department of Medicine III, University Hospital Carl Gustav Carus, 01307 Dresden, Germany
| | - Kai Johnsson
- Department of Chemical Biology, Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Heiko Lickert
- German Center for Diabetes Research, 85764 Neuherberg, Germany
- Institute of Diabetes and Regeneration Research, Helmholtz Diabetes Center, Helmholtz Center Munich, 85764 Neuherberg, Germany
| | - Thomas Kurth
- Center for Molecular and Cellular Bioengineering Technology Platform, Technische Universität Dresden, 01307 Dresden, Germany
| | - Eckhard Wolf
- Chair for Molecular Animal Breeding and Biotechnology Gene Center, Ludwig Maximilian University of Munich, 81377 Munich, Germany;
- Center for Innovative Medical Models, Ludwig Maximilian University of Munich, 81377 Munich, Germany
- German Center for Diabetes Research, 85764 Neuherberg, Germany
| | - Michele Solimena
- German Center for Diabetes Research, 85764 Neuherberg, Germany;
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
- Paul Langerhans Institute Dresden of the Helmholtz Center Munich, University Hospital Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01307 Dresden, Germany
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15
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Fan F, Wu Y, Hara M, Rizk A, Ji C, Nerad D, Tamarina N, Lou X. Dynamin deficiency causes insulin secretion failure and hyperglycemia. Proc Natl Acad Sci U S A 2021; 118:e2021764118. [PMID: 34362840 PMCID: PMC8364113 DOI: 10.1073/pnas.2021764118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β cells operate with a high rate of membrane recycling for insulin secretion, yet endocytosis in these cells is not fully understood. We investigate this process in mature mouse β cells by genetically deleting dynamin GTPase, the membrane fission machinery essential for clathrin-mediated endocytosis. Unexpectedly, the mice lacking all three dynamin genes (DNM1, DNM2, DNM3) in their β cells are viable, and their β cells still contain numerous insulin granules. Endocytosis in these β cells is severely impaired, resulting in abnormal endocytic intermediates on the plasma membrane. Although insulin granules are abundant, their release upon glucose stimulation is blunted in both the first and second phases, leading to hyperglycemia and glucose intolerance in mice. Dynamin triple deletion impairs insulin granule exocytosis and decreases intracellular Ca2+ responses and granule docking. The docking defect is correlated with reduced expression of Munc13-1 and RIM1 and reorganization of cortical F-actin in β cells. Collectively, these findings uncover the role of dynamin in dense-core vesicle endocytosis and secretory capacity. Insulin secretion deficiency in the absence of dynamin-mediated endocytosis highlights the risk of impaired membrane trafficking in endocrine failure and diabetes pathogenesis.
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Affiliation(s)
- Fan Fan
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226
| | - Yumei Wu
- HHMI, Yale University School of Medicine, New Haven, CT 06510
- Departments of Neuroscience and Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06510
| | - Manami Hara
- Section of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Chicago, Chicago, IL 60637
| | - Adam Rizk
- Section of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Chicago, Chicago, IL 60637
| | - Chen Ji
- Synapses and Circuits section, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892
| | - Dan Nerad
- Emergency Medicine, Carl R. Darnall Army Medical Center, Fort Hood, TX 76544
| | - Natalia Tamarina
- Department of Medicine, The Kovler Diabetes Center, University of Chicago, Chicago, IL 60637
| | - Xuelin Lou
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226;
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16
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Ghasemi A, Afzali H, Jeddi S. Effect of oral nitrite administration on gene expression of SNARE proteins involved in insulin secretion from pancreatic islets of male type 2 diabetic rats. Biomed J 2021; 45:387-395. [PMID: 34326021 PMCID: PMC9250122 DOI: 10.1016/j.bj.2021.04.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 03/30/2021] [Accepted: 04/15/2021] [Indexed: 02/06/2023] Open
Abstract
Background Nitrite stimulates insulin secretion from pancreatic β-cells; however, the underlying mechanisms have not been completely addressed. The aim of this study is to determine effect of nitrite on gene expression of SNARE proteins involved in insulin secretion from isolated pancreatic islets in Type 2 diabetic Wistar rats. Methods Three groups of rats were studied (n = 10/group): Control, diabetes, and diabetes + nitrite, which treated with sodium nitrite (50 mg/L) for 8 weeks. Type 2 diabetes was induced using a low-dose of streptozotocin (25 mg/kg) combined with high-fat diet. At the end of the study, pancreatic islets were isolated and mRNA expressions of interested genes were measured; in addition, protein expression of proinsulin and C-peptide in pancreatic tissue was assessed using immunofluorescence staining. Results Compared with controls, in the isolated pancreatic islets of Type 2 diabetic rats, mRNA expression of glucokinase (59%), syntaxin1A (49%), SNAP25 (70%), Munc18b (48%), insulin1 (56%), and insulin2 (52%) as well as protein expression of proinsulin and C-peptide were lower. In diabetic rats, nitrite administration significantly increased gene expression of glucokinase, synaptotagmin III, syntaxin1A, SNAP25, Munc18b, and insulin genes as well as increased protein expression of proinsulin and C-peptide. Conclusion Stimulatory effect of nitrite on insulin secretion in Type 2 diabetic rats is at least in part due to increased gene expression of molecules involved in glucose sensing (glucokinase), calcium sensing (synaptotagmin III), and exocytosis of insulin vesicles (syntaxin1A, SNAP25, and Munc18b) as well as increased expression of insulin genes.
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Affiliation(s)
- Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Hamideh Afzali
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Sajad Jeddi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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17
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Ježek P, Holendová B, Jabůrek M, Tauber J, Dlasková A, Plecitá-Hlavatá L. The Pancreatic β-Cell: The Perfect Redox System. Antioxidants (Basel) 2021; 10:antiox10020197. [PMID: 33572903 PMCID: PMC7912581 DOI: 10.3390/antiox10020197] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/20/2021] [Accepted: 01/25/2021] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β-cell insulin secretion, which responds to various secretagogues and hormonal regulations, is reviewed here, emphasizing the fundamental redox signaling by NADPH oxidase 4- (NOX4-) mediated H2O2 production for glucose-stimulated insulin secretion (GSIS). There is a logical summation that integrates both metabolic plus redox homeostasis because the ATP-sensitive K+ channel (KATP) can only be closed when both ATP and H2O2 are elevated. Otherwise ATP would block KATP, while H2O2 would activate any of the redox-sensitive nonspecific calcium channels (NSCCs), such as TRPM2. Notably, a 100%-closed KATP ensemble is insufficient to reach the -50 mV threshold plasma membrane depolarization required for the activation of voltage-dependent Ca2+ channels. Open synergic NSCCs or Cl- channels have to act simultaneously to reach this threshold. The resulting intermittent cytosolic Ca2+-increases lead to the pulsatile exocytosis of insulin granule vesicles (IGVs). The incretin (e.g., GLP-1) amplification of GSIS stems from receptor signaling leading to activating the phosphorylation of TRPM channels and effects on other channels to intensify integral Ca2+-influx (fortified by endoplasmic reticulum Ca2+). ATP plus H2O2 are also required for branched-chain ketoacids (BCKAs); and partly for fatty acids (FAs) to secrete insulin, while BCKA or FA β-oxidation provide redox signaling from mitochondria, which proceeds by H2O2 diffusion or hypothetical SH relay via peroxiredoxin "redox kiss" to target proteins.
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18
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Insulin granule biogenesis and exocytosis. Cell Mol Life Sci 2020; 78:1957-1970. [PMID: 33146746 PMCID: PMC7966131 DOI: 10.1007/s00018-020-03688-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/11/2020] [Accepted: 10/19/2020] [Indexed: 02/06/2023]
Abstract
Insulin is produced by pancreatic β-cells, and once released to the blood, the hormone stimulates glucose uptake and suppresses glucose production. Defects in both the availability and action of insulin lead to elevated plasma glucose levels and are major hallmarks of type-2 diabetes. Insulin is stored in secretory granules that form at the trans-Golgi network. The granules undergo extensive modifications en route to their release sites at the plasma membrane, including changes in both protein and lipid composition of the granule membrane and lumen. In parallel, the insulin molecules also undergo extensive modifications that render the hormone biologically active. In this review, we summarize current understanding of insulin secretory granule biogenesis, maturation, transport, docking, priming and eventual fusion with the plasma membrane. We discuss how different pools of granules form and how these pools contribute to insulin secretion under different conditions. We also highlight the role of the β-cell in the development of type-2 diabetes and discuss how dysregulation of one or several steps in the insulin granule life cycle may contribute to disease development or progression.
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19
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Yau B, Hays L, Liang C, Laybutt DR, Thomas HE, Gunton JE, Williams L, Hawthorne WJ, Thorn P, Rhodes CJ, Kebede MA. A fluorescent timer reporter enables sorting of insulin secretory granules by age. J Biol Chem 2020; 295:8901-8911. [PMID: 32341128 PMCID: PMC7335792 DOI: 10.1074/jbc.ra120.012432] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Revised: 03/21/2020] [Indexed: 01/03/2023] Open
Abstract
Within the pancreatic β-cells, insulin secretory granules (SGs) exist in functionally distinct pools, displaying variations in motility as well as docking and fusion capability. Current therapies that increase insulin secretion do not consider the existence of these distinct SG pools. Accordingly, these approaches are effective only for a short period, with a worsening of glycemia associated with continued decline in β-cell function. Insulin granule age is underappreciated as a determinant for why an insulin granule is selected for secretion and may explain why newly synthesized insulin is preferentially secreted from β-cells. Here, using a novel fluorescent timer protein, we aimed to investigate the preferential secretion model of insulin secretion and identify how granule aging is affected by variation in the β-cell environment, such as hyperglycemia. We demonstrate the use of a fluorescent timer construct, syncollin-dsRedE5TIMER, which changes its fluorescence from green to red over 18 h, in both microscopy and fluorescence-assisted organelle-sorting techniques. We confirm that the SG-targeting construct localizes to insulin granules in β-cells and does not interfere with normal insulin SG behavior. We visualize insulin SG aging behavior in MIN6 and INS1 β-cell lines and in primary C57BL/6J mouse and nondiabetic human islet cells. Finally, we separated young and old insulin SGs, revealing that preferential secretion of younger granules occurs in glucose-stimulated insulin secretion. We also show that SG population age is modulated by the β-cell environment in vivo in the db/db mouse islets and ex vivo in C57BL/6J islets exposed to different glucose environments.
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Affiliation(s)
- Belinda Yau
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; School of Life and Environmental Sciences, Faculty of Science, University of Sydney, Sydney, New South Wales, Australia
| | - Lori Hays
- STEM-Department of Biology, Edmonds Community College, Lynnwood, Washington, USA
| | - Cassandra Liang
- Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - D Ross Laybutt
- Garvan Institute of Medical Research, Sydney, New South Wales, Australia; St. Vincent's Clinical School, University of New South Wales Sydney, Sydney, New South Wales, Australia
| | - Helen E Thomas
- St. Vincent's Institute, Fitzroy, Victoria, Australia; Department of Medicine, St. Vincent's Hospital, University of Melbourne, Fitzroy, Victoria, Australia
| | - Jenny E Gunton
- Faculty of Medicine and Health, the University of Sydney, Sydney, New South Wales, Australia; The Westmead Institute for Medical Research, University of Sydney, Westmead, New South Wales, Australia
| | - Lindy Williams
- Faculty of Medicine and Health, the University of Sydney, Sydney, New South Wales, Australia; National Pancreas and Islet Transplant Unit (NPITU), Westmead Hospital, Sydney, New South Wales, Australia
| | - Wayne J Hawthorne
- Faculty of Medicine and Health, the University of Sydney, Sydney, New South Wales, Australia; National Pancreas and Islet Transplant Unit (NPITU), Westmead Hospital, Sydney, New South Wales, Australia
| | - Peter Thorn
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; Discipline of Physiology, School of Medical Sciences, Faculty of Medicine and Health, Charles Perkins Centre, University of Sydney, Camperdown, New South Wales, Australia
| | - Christopher J Rhodes
- Research and Early Development, Cardiovascular, Renal and Metabolic Diseases, BioPharmaceuticals R&D, AstraZeneca Ltd, Gaithersburg, Maryland, USA; Pacific Northwest Research Institute, Seattle, Washington, USA
| | - Melkam A Kebede
- Charles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia; School of Life and Environmental Sciences, Faculty of Science, University of Sydney, Sydney, New South Wales, Australia.
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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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Liu S, Promes JA, Harata M, Mishra A, Stephens SB, Taylor EB, Burand AJ, Sivitz WI, Fink BD, Ankrum JA, Imai Y. Adipose Triglyceride Lipase Is a Key Lipase for the Mobilization of Lipid Droplets in Human β-Cells and Critical for the Maintenance of Syntaxin 1a Levels in β-Cells. Diabetes 2020; 69:1178-1192. [PMID: 32312867 PMCID: PMC7243295 DOI: 10.2337/db19-0951] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 02/28/2020] [Indexed: 12/11/2022]
Abstract
Lipid droplets (LDs) are frequently increased when excessive lipid accumulation leads to cellular dysfunction. Distinct from mouse β-cells, LDs are prominent in human β-cells. However, the regulation of LD mobilization (lipolysis) in human β-cells remains unclear. We found that glucose increases lipolysis in nondiabetic human islets but not in islets in patients with type 2 diabetes (T2D), indicating dysregulation of lipolysis in T2D islets. Silencing adipose triglyceride lipase (ATGL) in human pseudoislets with shRNA targeting ATGL (shATGL) increased triglycerides (TGs) and the number and size of LDs, indicating that ATGL is the principal lipase in human β-cells. In shATGL pseudoislets, biphasic glucose-stimulated insulin secretion (GSIS), and insulin secretion to 3-isobutyl-1-methylxanthine and KCl were all reduced without altering oxygen consumption rate compared with scramble control. Like human islets, INS1 cells showed visible LDs, glucose-responsive lipolysis, and impairment of GSIS after ATGL silencing. ATGL-deficient INS1 cells and human pseudoislets showed reduced SNARE protein syntaxin 1a (STX1A), a key SNARE component. Proteasomal degradation of Stx1a was accelerated likely through reduced palmitoylation in ATGL-deficient INS1 cells. Therefore, ATGL is responsible for LD mobilization in human β-cells and supports insulin secretion by stabilizing STX1A. The dysregulated lipolysis may contribute to LD accumulation and β-cell dysfunction in T2D islets.
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Affiliation(s)
- Siming Liu
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Joseph A Promes
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Mikako Harata
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Akansha Mishra
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Samuel B Stephens
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Eric B Taylor
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Anthony J Burand
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA
| | - William I Sivitz
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Brian D Fink
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - James A Ankrum
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA
| | - Yumi Imai
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
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22
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CHL1 promotes insulin secretion and negatively regulates the proliferation of pancreatic β cells. Biochem Biophys Res Commun 2020; 525:1095-1102. [PMID: 32184019 DOI: 10.1016/j.bbrc.2020.03.040] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Accepted: 03/09/2020] [Indexed: 12/28/2022]
Abstract
Cell adhesion molecule L1-like protein (CHL1) is a member of neural recognition molecules of immunoglobulin superfamily primarily expressing in the nervous system. CHL1 regulates neuronal migration, axonal growth, and dendritic projection. Downregulation of CHL1 has been reported in β cells of patients with type 2 diabetes (T2DM). However, the detailed role of CHL1 in β cells has not been characterized. In this study, Real-Time PCR and Western blot were applied to investigate the tissue/cell distribution and expression of CHL1. Gain- or loss-of function studies were conducted in MIN6 cells to determine the effects of CHL1 on cell proliferation, apoptosis, cell cycle, and insulin secretion. Following silencing of CHL1 in MIN6 cells (si-CHL1), insulin secretion and the number of insulin secretary granules <50 nm from the cell membrane decreased in response to 20 mM glucose. Besides, silencing of CHL1 induced cell proliferation, reduced apoptosis, and prolonged S phase and shortened G1 phase of the cell cycle, contrary to overexpressing of CHL1. The inhibitor of ERK1/2MAPK eliminated the effect of CHL1 deficiency on the proliferation of MIN6 cells. In addition, high-fat diet could result in increased islet volume and β cell proliferation, decreased CHL1 expression and activation of ERK pathway in mice islets. Consequently, CHL1 expression was decreased in islets of high-fat induced mice, which resulted in cell proliferation via ERK pathway and regulation of the cell cycle through p53 pathway. These mechanisms may contribute to pancreatic β cell compensatory hyperplasia in obesity-induced pre-diabetes.
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23
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ELKS/Voltage-Dependent Ca 2+ Channel-β Subunit Module Regulates Polarized Ca 2+ Influx in Pancreatic β Cells. Cell Rep 2020; 26:1213-1226.e7. [PMID: 30699350 DOI: 10.1016/j.celrep.2018.12.106] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 10/29/2018] [Accepted: 12/27/2018] [Indexed: 12/14/2022] Open
Abstract
Pancreatic β cells secrete insulin by Ca2+-triggered exocytosis. However, there is no apparent secretory site similar to the neuronal active zones, and the cellular and molecular localization mechanism underlying polarized exocytosis remains elusive. Here, we report that ELKS, a vertebrate active zone protein, is used in β cells to regulate Ca2+ influx for insulin secretion. β cell-specific ELKS-knockout (KO) mice showed impaired glucose-stimulated first-phase insulin secretion and reduced L-type voltage-dependent Ca2+ channel (VDCC) current density. In situ Ca2+ imaging of β cells within islets expressing a membrane-bound G-CaMP8b Ca2+ sensor demonstrated initial local Ca2+ signals at the ELKS-localized vascular side of the β cell plasma membrane, which were markedly decreased in ELKS-KO β cells. Mechanistically, ELKS directly interacted with the VDCC-β subunit via the GK domain. These findings suggest that ELKS and VDCCs form a potent insulin secretion complex at the vascular side of the β cell plasma membrane for polarized Ca2+ influx and first-phase insulin secretion from pancreatic islets.
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24
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Thurmond DC, Gaisano HY. Recent Insights into Beta-cell Exocytosis in Type 2 Diabetes. J Mol Biol 2020; 432:1310-1325. [PMID: 31863749 PMCID: PMC8061716 DOI: 10.1016/j.jmb.2019.12.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 11/26/2019] [Accepted: 12/05/2019] [Indexed: 01/26/2023]
Abstract
As one of the leading causes of morbidity and mortality worldwide, diabetes affects an estimated 422 million adults, and it is expected to continue expanding such that by 2050, 30% of the U.S. population will become diabetic within their lifetime. Out of the estimated 422 million people currently afflicted with diabetes worldwide, about 5% have type 1 diabetes (T1D), while the remaining ~95% of diabetics have type 2 diabetes (T2D). Type 1 diabetes results from the autoimmune-mediated destruction of functional β-cell mass, whereas T2D results from combinatorial defects in functional β-cell mass plus peripheral glucose uptake. Both types of diabetes are now believed to be preceded by β-cell dysfunction. T2D is increasingly associated with numerous reports of deficiencies in the exocytosis proteins that regulate insulin release from β-cells, specifically the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. SNARE protein's functionality is further regulated by a variety of accessory factors such as Sec1/Munc18 (SM), double C2-domain proteins (DOC2), and additional interacting proteins at the cell surface that influence the fidelity of insulin release. As new evidence emerges about the detailed mechanisms of exocytosis, new questions and controversies have come to light. This emerging information is also contributing to dialogue in the islet biology field focused on how to correct the defects in insulin exocytosis. Herein we present a balanced review of the role of exocytosis proteins in T2D, with thoughts on novel strategies to protect functional β-cell mass.
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Affiliation(s)
- Debbie C Thurmond
- Department of Molecular and Cellular Endocrinology, Beckman Research Institute of City of Hope, CA, USA.
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25
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Fujihira H, Masahara-Negishi Y, Akimoto Y, Hirayama H, Lee HC, Story BA, Mueller WF, Jakob P, Clauder-Münster S, Steinmetz LM, Radhakrishnan SK, Kawakami H, Kamada Y, Miyoshi E, Yokomizo T, Suzuki T. Liver-specific deletion of Ngly1 causes abnormal nuclear morphology and lipid metabolism under food stress. Biochim Biophys Acta Mol Basis Dis 2020; 1866:165588. [DOI: 10.1016/j.bbadis.2019.165588] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 09/09/2019] [Accepted: 10/09/2019] [Indexed: 12/14/2022]
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26
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Liang T, Qin T, Kang F, Kang Y, Xie L, Zhu D, Dolai S, Greitzer-Antes D, Baker RK, Feng D, Tuduri E, Ostenson CG, Kieffer TJ, Banks K, Pessin JE, Gaisano HY. SNAP23 depletion enables more SNAP25/calcium channel excitosome formation to increase insulin exocytosis in type 2 diabetes. JCI Insight 2020; 5:129694. [PMID: 32051343 PMCID: PMC7098801 DOI: 10.1172/jci.insight.129694] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 01/15/2020] [Indexed: 01/05/2023] Open
Abstract
SNAP23 is the ubiquitous SNAP25 isoform that mediates secretion in non-neuronal cells, similar to SNAP25 in neurons. However, some secretory cells like pancreatic islet β cells contain an abundance of both SNAP25 and SNAP23, where SNAP23 is believed to play a redundant role to SNAP25. We show that SNAP23, when depleted in mouse β cells in vivo and human β cells (normal and type 2 diabetes [T2D] patients) in vitro, paradoxically increased biphasic glucose-stimulated insulin secretion corresponding to increased exocytosis of predocked and newcomer insulin granules. Such effects on T2D Goto-Kakizaki rats improved glucose homeostasis that was superior to conventional treatment with sulfonylurea glybenclamide. SNAP23, although fusion competent in slower secretory cells, in the context of β cells acts as a weak partial fusion agonist or inhibitory SNARE. Here, SNAP23 depletion promotes SNAP25 to bind calcium channels more quickly and longer where granule fusion occurs to increase exocytosis efficiency. β Cell SNAP23 antagonism is a strategy to treat diabetes.
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Affiliation(s)
- Tao Liang
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Tairan Qin
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Fei Kang
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Youhou Kang
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Li Xie
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Dan Zhu
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Subhankar Dolai
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Dafna Greitzer-Antes
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Robert K. Baker
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Daorong Feng
- Michael F. Price Center for Genetic and Translational Medicine, Department of Medicine and Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Eva Tuduri
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Claes-Goran Ostenson
- Department of Molecular Medicine and,Department of Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Timothy J. Kieffer
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kate Banks
- Division of Comparative Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Jeffrey E. Pessin
- Michael F. Price Center for Genetic and Translational Medicine, Department of Medicine and Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Herbert Y. Gaisano
- Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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27
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Oakie A, Zhou L, Rivers S, Cheung C, Li J, Wang R. Postnatal knockout of beta cell insulin receptor impaired insulin secretion in male mice exposed to high-fat diet stress. Mol Cell Endocrinol 2020; 499:110588. [PMID: 31541682 DOI: 10.1016/j.mce.2019.110588] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/28/2019] [Accepted: 09/16/2019] [Indexed: 01/19/2023]
Abstract
The presence of insulin receptor (IR) on insulin-secreting beta cells suggests an autocrine regulatory role for insulin in its own signalling. Congenital beta cell-specific IR knockout (βIRKO) mouse studies have demonstrated the development of age-dependent glucose intolerance. We investigated the role of beta cell IR signalling specifically during postnatal life following undisturbed prenatal pancreatic development and maturation. We utilized a tamoxifen-inducible mouse insulin 1 promoter (MIP) driven Cre recombinase IR knockout mouse model (MIP-βIRKO) to achieve partial knockout of IR in islets and determine the functional role of beta cell IR in adult mice fed a control normal diet (ND) or 60% high-fat diet (HFD). At 24 weeks of age, MIP-βIRKO ND mice maintained glucose tolerance, insulin release, and unchanged beta cell mass when compared to control ND mice. In contrast, 24-week-old MIP-βIRKO mice demonstrated significant glucose intolerance and lower insulin release after 18 weeks of HFD feeding. A reduction in beta cell soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein expression, phosphorylated AktS473 and P70S6K1T389, and glucose transporter 2 (GLUT2) expression were also identified in MIP-βIRKO HFD islets. Overall, the postnatal knockout of beta cell IR in HFD-fed mice resulted in decreased expression of beta cell glucose-sensing and exocytotic proteins and a reduction in intracellular signalling. These findings highlight that IR expression in the adult islet is required to maintain beta cell function under hyperglycemic stress.
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Affiliation(s)
- Amanda Oakie
- Children's Health Research Institute, University of Western Ontario, London, ON, N6C 2V5, Canada; Department of Pathology and Laboratory Medicine, University of Western Ontario, London, ON, N6C 2V5, Canada
| | - Liangyi Zhou
- Children's Health Research Institute, University of Western Ontario, London, ON, N6C 2V5, Canada; Department of Pathology and Laboratory Medicine, University of Western Ontario, London, ON, N6C 2V5, Canada
| | - Sydney Rivers
- Children's Health Research Institute, University of Western Ontario, London, ON, N6C 2V5, Canada; Department of Physiology and Pharmacology, and University of Western Ontario, London, ON, N6C 2V5, Canada
| | - Christy Cheung
- Children's Health Research Institute, University of Western Ontario, London, ON, N6C 2V5, Canada; Department of Physiology and Pharmacology, and University of Western Ontario, London, ON, N6C 2V5, Canada
| | - Jinming Li
- Children's Health Research Institute, University of Western Ontario, London, ON, N6C 2V5, Canada; Department of Physiology and Pharmacology, and 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 and Pharmacology, and 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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28
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Araki K, Araki A, Honda D, Izumoto T, Hashizume A, Hijikata Y, Yamada S, Iguchi Y, Hara A, Ikumi K, Kawai K, Ishigaki S, Nakamichi Y, Tsunekawa S, Seino Y, Yamamoto A, Takayama Y, Hidaka S, Tominaga M, Ohara-Imaizumi M, Suzuki A, Ishiguro H, Enomoto A, Yoshida M, Arima H, Muramatsu SI, Sobue G, Katsuno M. TDP-43 regulates early-phase insulin secretion via CaV1.2-mediated exocytosis in islets. J Clin Invest 2019; 129:3578-3593. [PMID: 31355778 DOI: 10.1172/jci124481] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 06/04/2019] [Indexed: 12/13/2022] Open
Abstract
TAR DNA-binding protein 43 kDa (TDP-43), encoded by TARDBP, is an RNA-binding protein, the nuclear depletion of which is the histopathological hallmark of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disorder affecting both upper and lower motor neurons. Besides motor symptoms, patients with ALS often develop nonneuronal signs including glucose intolerance, but the underlying pathomechanism is still controversial, i.e., whether it is impaired insulin secretion and/or insulin resistance. Here, we showed that ALS subjects reduced early-phase insulin secretion and that the nuclear localization of TDP-43 was lost in the islets of autopsied ALS pancreas. Loss of TDP-43 inhibited exocytosis by downregulating CaV1.2 calcium channels, thereby reducing early-phase insulin secretion in a cultured β cell line (MIN6) and β cell-specific Tardbp knockout mice. Overexpression of CaV1.2 restored early-phase insulin secretion in Tardbp knocked-down MIN6 cells. Our findings suggest that TDP-43 regulates cellular exocytosis mediated by L-type voltage-dependent calcium channels and thus plays an important role in the early phase of insulin secretion by pancreatic islets. Thus, nuclear loss of TDP-43 is implicated in not only the selective loss of motor neurons but also in glucose intolerance due to impaired insulin secretion at an early stage of ALS.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Akitoshi Hara
- Department of Pathology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
| | | | | | | | - Yoko Nakamichi
- Department of Biochemistry, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | | | - Yusuke Seino
- Department of Endocrinology and Metabolism, Fujita Health University, Toyoake, Aichi, Japan
| | - Akiko Yamamoto
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
| | - Yasunori Takayama
- Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Shihomi Hidaka
- Department of Endocrinology and Metabolism, Fujita Health University, Toyoake, Aichi, Japan
| | - Makoto Tominaga
- Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Mica Ohara-Imaizumi
- Department of Biochemistry, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Atsushi Suzuki
- Department of Endocrinology and Metabolism, Fujita Health University, Toyoake, Aichi, Japan
| | - Hiroshi Ishiguro
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
| | - Atsushi Enomoto
- Department of Pathology, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
| | - Mari Yoshida
- Department of Neuropathology, Institute for Medical Science of Aging, Aichi Medical University, Nagakute, Aichi, Japan
| | | | - Shin-Ichi Muramatsu
- Division of Neurological Gene Therapy, Jichi Medical University, Shimotsuke, Tochigi, Japan.,Center for Gene & Cell Therapy, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Gen Sobue
- Brain and Mind Research Center, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
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29
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Marin BK, Lima Reis SR, Fátima Silva Ramalho A, Lemes SF, Marin L, Vanzela EC, Boschero AC, Carneiro EM, Latorraca MQ, Arantes VC, Barros Reis MA. Protein restriction in early life increases intracellular calcium and insulin secretion, but does not alter expression of SNARE proteins during pregnancy. Exp Physiol 2019; 104:1029-1037. [DOI: 10.1113/ep087045] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 04/24/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Bianca Karine Marin
- Mestrado em Biociências, Faculdade de NutriçãoUniversidade Federal de Mato Grosso Cuiabá MT Brazil
| | - Silvia Regina Lima Reis
- Departamento de Alimentos Nutrição, Faculdade de NutriçãoUniversidade Federal de Mato Grosso Cuiabá MT Brazil
| | | | - Simone Ferreira Lemes
- Mestrado em Biociências, Faculdade de NutriçãoUniversidade Federal de Mato Grosso Cuiabá MT Brazil
| | - Leonardo Marin
- Mestrado em Biociências, Faculdade de NutriçãoUniversidade Federal de Mato Grosso Cuiabá MT Brazil
| | - Emerielle Cristine Vanzela
- Departamento de Anatomia, Biologia Celular, Fisiologia e BiofísicaInstituto de Biologia, Universidade Estadual de Campinas, Avenida Bertrand Russel, s/n, Cidade Universitária Zeferino Vaz Campinas SP Brazil
| | - Antonio Carlos Boschero
- Departamento de Anatomia, Biologia Celular, Fisiologia e BiofísicaInstituto de Biologia, Universidade Estadual de Campinas, Avenida Bertrand Russel, s/n, Cidade Universitária Zeferino Vaz Campinas SP Brazil
| | - Everardo Magalhães Carneiro
- Departamento de Anatomia, Biologia Celular, Fisiologia e BiofísicaInstituto de Biologia, Universidade Estadual de Campinas, Avenida Bertrand Russel, s/n, Cidade Universitária Zeferino Vaz Campinas SP Brazil
| | - Márcia Queiroz Latorraca
- Departamento de Alimentos Nutrição, Faculdade de NutriçãoUniversidade Federal de Mato Grosso Cuiabá MT Brazil
| | - Vanessa Cristina Arantes
- Departamento de Alimentos Nutrição, Faculdade de NutriçãoUniversidade Federal de Mato Grosso Cuiabá MT Brazil
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30
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Yin P, Gandasi NR, Arora S, Omar-Hmeadi M, Saras J, Barg S. Syntaxin clusters at secretory granules in a munc18-bound conformation. Mol Biol Cell 2018; 29:2700-2708. [PMID: 30156474 PMCID: PMC6249827 DOI: 10.1091/mbc.e17-09-0541] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Syntaxin (stx)-1 is an integral plasma membrane protein that is crucial for two distinct steps of regulated exocytosis, docking of secretory granules at the plasma membrane and membrane fusion. During docking, stx1 clusters at the granule docking site, together with the S/M protein munc18. Here we determined features of stx1 that contribute to its clustering at granules. In live insulin-secreting cells, stx1 and stx3 (but not stx4 or stx11) accumulated at docked granules, and stx1 (but not stx4) rescued docking in cells expressing botulinum neurotoxin-C. Using a series of stx1 deletion mutants and stx1/4 chimeras, we found that all four helical domains (Ha, Hb, Hc, SNARE) and the short N-terminal peptide contribute to recruitment to granules. However, only the Hc domain confers specificity, and it must be derived from stx1 for recruitment to occur. Point mutations in the Hc or the N-terminal peptide designed to interfere with binding to munc18-1 prevent stx1 from clustering at granules, and a mutant munc18 deficient in binding to stx1 does not cluster at granules. We conclude that stx1 is recruited to the docking site in a munc18-1–bound conformation, providing a rationale for the requirement for both proteins for granule docking.
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Affiliation(s)
- Peng Yin
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Nikhil R Gandasi
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Swati Arora
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Muhmmad Omar-Hmeadi
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Jan Saras
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
| | - Sebastian Barg
- Institute of Medical Cell Biology, Uppsala University, 75123 Uppsala, Sweden
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31
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Aslamy A, Oh E, Olson EM, Zhang J, Ahn M, Moin ASM, Tunduguru R, Salunkhe VA, Veluthakal R, Thurmond DC. Doc2b Protects β-Cells Against Inflammatory Damage and Enhances Function. Diabetes 2018; 67:1332-1344. [PMID: 29661782 PMCID: PMC6014558 DOI: 10.2337/db17-1352] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 04/09/2018] [Indexed: 12/12/2022]
Abstract
Loss of functional β-cell mass is an early feature of type 1 diabetes. To release insulin, β-cells require soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes, as well as SNARE complex regulatory proteins like double C2 domain-containing protein β (Doc2b). We hypothesized that Doc2b deficiency or overabundance may confer susceptibility or protection, respectively, to the functional β-cell mass. Indeed, Doc2b+/- knockout mice show an unusually severe response to multiple-low-dose streptozotocin (MLD-STZ), resulting in more apoptotic β-cells and a smaller β-cell mass. In addition, inducible β-cell-specific Doc2b-overexpressing transgenic (βDoc2b-dTg) mice show improved glucose tolerance and resist MLD-STZ-induced disruption of glucose tolerance, fasting hyperglycemia, β-cell apoptosis, and loss of β-cell mass. Mechanistically, Doc2b enrichment enhances glucose-stimulated insulin secretion (GSIS) and SNARE activation and prevents the appearance of apoptotic markers in response to cytokine stress and thapsigargin. Furthermore, expression of a peptide containing the Doc2b tandem C2A and C2B domains is sufficient to confer the beneficial effects of Doc2b enrichment on GSIS, SNARE activation, and apoptosis. These studies demonstrate that Doc2b enrichment in the β-cell protects against diabetogenic and proapoptotic stress. Furthermore, they identify a Doc2b peptide that confers the beneficial effects of Doc2b and may be a therapeutic candidate for protecting functional β-cell mass.
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Affiliation(s)
- Arianne Aslamy
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN
| | - Eunjin Oh
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Erika M Olson
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Jing Zhang
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Miwon Ahn
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Abu Saleh Md Moin
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Ragadeepthi Tunduguru
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
- Department of Diabetes Complications and Metabolism, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Vishal A Salunkhe
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Rajakrishnan Veluthakal
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Debbie C Thurmond
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN
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32
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Salunkhe VA, Ofori JK, Gandasi NR, Salö SA, Hansson S, Andersson ME, Wendt A, Barg S, Esguerra JLS, Eliasson L. MiR-335 overexpression impairs insulin secretion through defective priming of insulin vesicles. Physiol Rep 2018; 5:5/21/e13493. [PMID: 29122960 PMCID: PMC5688784 DOI: 10.14814/phy2.13493] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 10/11/2017] [Accepted: 10/13/2017] [Indexed: 01/01/2023] Open
Abstract
MicroRNAs contribute to the maintenance of optimal cellular functions by fine‐tuning protein expression levels. In the pancreatic β‐cells, imbalances in the exocytotic machinery components lead to impaired insulin secretion and type 2 diabetes (T2D). We hypothesize that dysregulated miRNA expression exacerbates β‐cell dysfunction, and have earlier shown that islets from the diabetic GK‐rat model have increased expression of miRNAs, including miR‐335‐5p (miR‐335). Here, we aim to determine the specific role of miR‐335 during development of T2D, and the influence of this miRNA on glucose‐stimulated insulin secretion and Ca2+‐dependent exocytosis. We found that the expression of miR‐335 negatively correlated with secretion index in human islets of individuals with prediabetes. Overexpression of miR‐335 in human EndoC‐βH1 and in rat INS‐1 832/13 cells (OE335) resulted in decreased glucose‐stimulated insulin secretion, and OE335 cells showed concomitant reduction in three exocytotic proteins: SNAP25, Syntaxin‐binding protein 1 (STXBP1), and synaptotagmin 11 (SYT11). Single‐cell capacitance measurements, complemented with TIRF microscopy of the granule marker NPY‐mEGFP demonstrated a significant reduction in exocytosis in OE335 cells. The reduction was not associated with defective docking or decreased Ca2+ current. More likely, it is a direct consequence of impaired priming of already docked granules. Earlier reports have proposed reduced granular priming as the cause of reduced first‐phase insulin secretion during prediabetes. Here, we show a specific role of miR‐335 in regulating insulin secretion during this transition period. Moreover, we can conclude that miR‐335 has the capacity to modulate insulin secretion and Ca2+‐dependent exocytosis through effects on granular priming.
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Affiliation(s)
- Vishal A Salunkhe
- Department of Clinical Sciences Malmö, Islet Cell Exocytosis Lund University Diabetes Centre Lund University, Malmö, Sweden
| | - Jones K Ofori
- Department of Clinical Sciences Malmö, Islet Cell Exocytosis Lund University Diabetes Centre Lund University, Malmö, Sweden
| | - Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sofia A Salö
- Department of Clinical Sciences Malmö, Islet Cell Exocytosis Lund University Diabetes Centre Lund University, Malmö, Sweden
| | - Sofia Hansson
- Department of Clinical Sciences Malmö, Islet Cell Exocytosis Lund University Diabetes Centre Lund University, Malmö, Sweden
| | - Markus E Andersson
- Department of Clinical Sciences Malmö, Islet Cell Exocytosis Lund University Diabetes Centre Lund University, Malmö, Sweden
| | - Anna Wendt
- Department of Clinical Sciences Malmö, Islet Cell Exocytosis Lund University Diabetes Centre Lund University, Malmö, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Jonathan L S Esguerra
- Department of Clinical Sciences Malmö, Islet Cell Exocytosis Lund University Diabetes Centre Lund University, Malmö, Sweden
| | - Lena Eliasson
- Department of Clinical Sciences Malmö, Islet Cell Exocytosis Lund University Diabetes Centre Lund University, Malmö, Sweden
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Stermann T, Menzel F, Weidlich C, Jeruschke K, Weiss J, Altenhofen D, Benninghoff T, Pujol A, Bosch F, Rustenbeck I, Ouwens DM, Thoresen GH, de Wendt C, Lebek S, Schallschmidt T, Kragl M, Lammert E, Chadt A, Al-Hasani H. Deletion of the RabGAP TBC1D1 Leads to Enhanced Insulin Secretion and Fatty Acid Oxidation in Islets From Male Mice. Endocrinology 2018; 159:1748-1761. [PMID: 29481597 DOI: 10.1210/en.2018-00087] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 01/26/2018] [Indexed: 01/24/2023]
Abstract
The Rab guanosine triphosphatase-activating protein (RabGAP) TBC1D1 has been shown to be a key regulator of glucose and lipid metabolism in skeletal muscle. Its function in pancreatic islets, however, is not yet fully understood. Here, we aimed to clarify the specific impact of TBC1D1 on insulin secretion and substrate use in pancreatic islets. We analyzed the dynamics of glucose-stimulated insulin secretion (GSIS) and lipid metabolism in isolated islets from Tbc1d1-deficient (D1KO) mice. To further investigate the underlying cellular mechanisms, we conducted pharmacological studies in these islets. In addition, we determined morphology and number of both pancreatic islets and insulin vesicles in β-cells using light and transmission electron microscopy. Isolated pancreatic islets from D1KO mice exhibited substantially increased GSIS compared with wild-type (WT) controls. This was attributed to both enhanced first and second phase of insulin secretion, and this enhanced secretion persisted during repetitive glucose stimuli. Studies with sulfonylureas or KCl in isolated islets demonstrated that TBC1D1 exerts its function via a signaling pathway at the level of membrane depolarization. In line, ultrastructural analysis of isolated pancreatic islets revealed both higher insulin-granule density and number of docked granules in β-cells from D1KO mice compared with WT controls. Like in skeletal muscle, lipid use in isolated islets was enhanced upon D1KO, presumably as a result of a higher mitochondrial fission rate and/or higher mitochondrial activity. Our results clearly demonstrate a dual role of TBC1D1 in controlling substrate metabolism of the pancreatic islet.
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Affiliation(s)
- Torben Stermann
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
| | - Franziska Menzel
- German Institute for Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Carmen Weidlich
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
| | - Kay Jeruschke
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
| | - Jürgen Weiss
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
| | - Delsi Altenhofen
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
| | - Tim Benninghoff
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
| | - Anna Pujol
- Center of Animal Biotechnology and Gene Therapy, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Fatima Bosch
- Center of Animal Biotechnology and Gene Therapy, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Ingo Rustenbeck
- Institute of Pharmacology, Toxicology and Clinical Pharmacy, Technical University Braunschweig, Braunschweig, Germany
| | - D Margriet Ouwens
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
| | - G Hege Thoresen
- Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway
| | - Christian de Wendt
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
| | - Sandra Lebek
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
| | - Tanja Schallschmidt
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
| | - Martin Kragl
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
| | - Eckhard Lammert
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
| | - Alexandra Chadt
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
| | - Hadi Al-Hasani
- German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Medical Faculty, Duesseldorf, Germany
- German Center for Diabetes Research, Duesseldorf, Germany
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34
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Greitzer-Antes D, Xie L, Qin T, Xie H, Zhu D, Dolai S, Liang T, Kang F, Hardy AB, He Y, Kang Y, Gaisano HY. K v2.1 clusters on β-cell plasma membrane act as reservoirs that replenish pools of newcomer insulin granule through their interaction with syntaxin-3. J Biol Chem 2018; 293:6893-6904. [PMID: 29549124 DOI: 10.1074/jbc.ra118.002703] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Revised: 03/09/2018] [Indexed: 01/22/2023] Open
Abstract
The voltage-dependent K+ (Kv) channel Kv2.1 is a major delayed rectifier in many secretory cells, including pancreatic β cells. In addition, Kv2.1 has a direct role in exocytosis at an undefined step, involving SNARE proteins, that is independent of its ion-conducting pore function. Here, we elucidated the precise step in exocytosis. We previously reported that syntaxin-3 (Syn-3) is the key syntaxin that mediates exocytosis of newcomer secretory granules that spend minimal residence time on the plasma membrane before fusion. Using high-resolution total internal reflection fluorescence microscopy, we now show that Kv2.1 forms reservoir clusters on the β-cell plasma membrane and binds Syn-3 via its C-terminal C1b domain, which recruits newcomer insulin secretory granules into this large reservoir. Upon glucose stimulation, secretory granules were released from this reservoir to replenish the pool of newcomer secretory granules for subsequent fusion, occurring just adjacent to the plasma membrane Kv2.1 clusters. C1b deletion blocked the aforementioned Kv2.1-Syn-3-mediated events and reduced fusion of newcomer secretory granules. These insights have therapeutic implications, as Kv2.1 overexpression in type-2 diabetes rat islets restored biphasic insulin secretion.
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Affiliation(s)
- Dafna Greitzer-Antes
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Li Xie
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Tairan Qin
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Huanli Xie
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Dan Zhu
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Subhankar Dolai
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Tao Liang
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Fei Kang
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Alexandre B Hardy
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Yan He
- the Department of Epidemiology and Health Statistics, School of Public Health and Family Medicine, Capital Medical University, Beijing 100050, China
| | - Youhou Kang
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Herbert Y Gaisano
- From the Departments of Medicine and Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
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35
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Gandasi NR, Yin P, Omar-Hmeadi M, Ottosson Laakso E, Vikman P, Barg S. Glucose-Dependent Granule Docking Limits Insulin Secretion and Is Decreased in Human Type 2 Diabetes. Cell Metab 2018; 27:470-478.e4. [PMID: 29414688 DOI: 10.1016/j.cmet.2017.12.017] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/26/2017] [Accepted: 12/23/2017] [Indexed: 01/19/2023]
Abstract
Glucose-stimulated insulin secretion is biphasic, with a rapid first phase and a slowly developing sustained second phase; both are disturbed in type 2 diabetes (T2D). Biphasic secretion results from vastly different release probabilities of individual insulin granules, but the morphological and molecular basis for this is unclear. Here, we show that human insulin secretion and exocytosis critically depend on the availability of membrane-docked granules and that T2D is associated with a strong reduction in granule docking. Glucose accelerated granule docking, and this effect was absent in T2D. Newly docked granules only slowly acquired release competence; this was regulated by major signaling pathways, but not glucose. Gene expression analysis indicated that key proteins involved in granule docking are downregulated in T2D, and overexpression of these proteins increased granule docking. The findings establish granule docking as an important glucose-dependent step in human insulin secretion that is dysregulated in T2D.
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Affiliation(s)
- Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Peng Yin
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Muhmmad Omar-Hmeadi
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Emilia Ottosson Laakso
- Diabetes and Endocrinology Unit, Department of Clinical Sciences, Lund University Diabetes Centre, 20502 Malmö, Sweden
| | - Petter Vikman
- Diabetes and Endocrinology Unit, Department of Clinical Sciences, Lund University Diabetes Centre, 20502 Malmö, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden.
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36
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Nan H, Han L, Ma J, Yang C, Su R, He J. STX3 represses the stability of the tumor suppressor PTEN to activate the PI3K-Akt-mTOR signaling and promotes the growth of breast cancer cells. Biochim Biophys Acta Mol Basis Dis 2018; 1864:1684-1692. [PMID: 29408595 DOI: 10.1016/j.bbadis.2018.01.031] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 01/14/2018] [Accepted: 01/30/2018] [Indexed: 01/01/2023]
Abstract
Syntaxin 3, also known as STX3, is a protein encoded by the STX3 gene in humans. This protein is one of the fundamental components of the exocytotic machinery required for the docking and fusion of secretory granules with the plasma membrane. The roles of STX3 in human breast cancer remains elusive. Here we report that STX3 acts as an oncogenic protein in human breast cancer. We analyzed the expression of STX3 in 148 patients with breast cancer. The mRNA and protein levels of STX3 are significantly up-regulated in human breast cancer compared with matched adjacent non-cancer tissues. The up-regulation of STX3 is correlated with high disease stage and predicts overall and disease-free survival in patients with breast cancer. Lentivirus-mediated knockdown of STX3 represses in vitro proliferation and colony formation and in vivo growth of breast cancer cells, whereas STX3 overexpression promotes the growth of breast cancer cells in vitro and in vivo. We find that STX3 promotes the proliferation of breast cancer cells by increasing the activation of the Akt-mTOR signaling, and Akt inhibitor Ipatasertib or MK-2206 represses STX3 effects on the growth of breast cancer cells. Further mechanism study shows that STX3 binds to PTEN and increases PTEN ubiquitination and degradation, thus leading to activation of the PI3K-Akt-mTOR signaling. Therefore, STX3 promotes the growth of breast cancer cells by regulating the PTEN-PI3K-Akt-mTOR signaling.
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Affiliation(s)
- Haocheng Nan
- Department of Breast Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, PR China
| | - Lili Han
- Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, PR China
| | - Jiequn Ma
- Department of Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, PR China
| | - Chengcheng Yang
- Department of Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, PR China
| | - Rujuan Su
- Department of Oncology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, PR China
| | - Jianjun He
- Department of Breast Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, PR China.
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37
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Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 446] [Impact Index Per Article: 74.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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38
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Fujiwara T, Kofuji T, Mishima T, Akagawa K. Syntaxin 1B contributes to regulation of the dopaminergic system through GABA transmission in the CNS. Eur J Neurosci 2017; 46:2867-2874. [PMID: 29139159 DOI: 10.1111/ejn.13779] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 11/09/2017] [Accepted: 11/09/2017] [Indexed: 12/17/2022]
Abstract
In neuronal plasma membrane, two syntaxin isoforms, HPC-1/syntaxin 1A (STX1A) and syntaxin 1B (STX1B), are predominantly expressed as soluble N-ethylmaleimide-sensitive fusion attachment protein receptors, also known as t-SNAREs. We previously reported that glutamatergic and GABAergic synaptic transmissions are impaired in Stx1b null mutant (Stx1b-/- ) mice but are almost normal in Stx1a null mutant (Stx1a-/- ) mice. These observations suggested that STX1A and STX1B have distinct functions in fast synaptic transmission in the central nervous system (CNS). Interestingly, recent studies indicated that Stx1a-/- or Stx1a+/- mice exhibit disruption in the monoaminergic system in the CNS, causing unusual behaviour that is similar to neuropsychological alterations observed in psychiatric patients. Here, we studied whether STX1B contributes to the regulation of monoaminergic system and if STX1B is related to neuropsychological properties in human neuropsychological disorders similar to STX1A. We found that monoamine release in vitro was normal in Stx1b+/- mice unlike Stx1a-/- or Stx1a+/- mice, but the basal extracellular dopamine (DA) concentration in the ventral striatum was increased. DA secretion in the ventral striatum is regulated by GABAergic neurons, and Stx1b+/- mice exhibited reduced GABA release both in vitro and in vivo, disrupting the DAergic system in the CNS of these mice. We also found that Stx1b+/- mice exhibited reduced pre-pulse inhibition (PPI), which is believed to represent one of the prominent schizotypal behavioural profiles of human psychiatric patients. The reduction in PPI was rescued by DA receptor antagonists. These observations indicated that STX1B contributes to excess activity of the DAergic system through regulation of GABAergic transmission.
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Affiliation(s)
- Tomonori Fujiwara
- Department of Cell Physiology, Kyorin University School of Medicine, Shinkawa, Mitaka, Tokyo, 181-8611, Japan
| | - Takefumi Kofuji
- Department of Cell Physiology, Kyorin University School of Medicine, Shinkawa, Mitaka, Tokyo, 181-8611, Japan.,Radioisotope Laboratory, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Tatsuya Mishima
- Department of Cell Physiology, Kyorin University School of Medicine, Shinkawa, Mitaka, Tokyo, 181-8611, Japan
| | - Kimio Akagawa
- Department of Cell Physiology, Kyorin University School of Medicine, Shinkawa, Mitaka, Tokyo, 181-8611, Japan
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39
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Hastoy B, Clark A, Rorsman P, Lang J. Fusion pore in exocytosis: More than an exit gate? A β-cell perspective. Cell Calcium 2017; 68:45-61. [PMID: 29129207 DOI: 10.1016/j.ceca.2017.10.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 10/17/2017] [Accepted: 10/24/2017] [Indexed: 12/14/2022]
Abstract
Secretory vesicle exocytosis is a fundamental biological event and the process by which hormones (like insulin) are released into the blood. Considerable progress has been made in understanding this precisely orchestrated sequence of events from secretory vesicle docked at the cell membrane, hemifusion, to the opening of a membrane fusion pore. The exact biophysical and physiological regulation of these events implies a close interaction between membrane proteins and lipids in a confined space and constrained geometry to ensure appropriate delivery of cargo. We consider some of the still open questions such as the nature of the initiation of the fusion pore, the structure and the role of the Soluble N-ethylmaleimide-sensitive-factor Attachment protein REceptor (SNARE) transmembrane domains and their influence on the dynamics and regulation of exocytosis. We discuss how the membrane composition and protein-lipid interactions influence the likelihood of the nascent fusion pore forming. We relate these factors to the hypothesis that fusion pore expansion could be affected in type-2 diabetes via changes in disease-related gene transcription and alterations in the circulating lipid profile. Detailed characterisation of the dynamics of the fusion pore in vitro will contribute to understanding the larger issue of insulin secretory defects in diabetes.
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Affiliation(s)
- Benoit Hastoy
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK.
| | - Anne Clark
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK; Metabolic Research, Institute of Neuroscience and Physiology, University of Goteborg, Medicinaregatan 11, S-41309 Göteborg, Sweden
| | - Jochen Lang
- Laboratoire de Chimie et Biologie des Membranes et Nano-objets (CBMN), CNRS UMR 5248, Université de Bordeaux, Allée de Geoffrey St Hilaire, 33600 Pessac, France.
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40
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Müller A, Mziaut H, Neukam M, Knoch KP, Solimena M. A 4D view on insulin secretory granule turnover in the β-cell. Diabetes Obes Metab 2017; 19 Suppl 1:107-114. [PMID: 28880479 DOI: 10.1111/dom.13015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 05/16/2017] [Accepted: 05/17/2017] [Indexed: 01/31/2023]
Abstract
Insulin secretory granule (SG) turnover consists of several highly regulated processes allowing for proper β-cell function and insulin secretion. Besides the spatial distribution of insulin SGs, their age has great impact on the likelihood of their secretion and their behaviour within the β-cell. While quantitative measurements performed decades ago demonstrated the preferential secretion of young insulin, new experimental approaches aim to investigate insulin ageing at the granular level. Live-cell imaging, automated image analysis and correlative light and electron microscopy have fostered knowledge of age-defined insulin SG dynamics, their interaction with the cytoskeleton and ultrastructural features. Here, we review our recent work in regards to the connection between insulin SG age, SG dynamics, intracellular location and interaction with other proteins.
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Affiliation(s)
- Andreas Müller
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Hassan Mziaut
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Martin Neukam
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Klaus-Peter Knoch
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Michele Solimena
- Molecular Diabetology, University Hospital and Faculty of Medicine Carl Gustav Carus, TU Dresden, Dresden, Germany
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich, University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany
- German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG), Dresden, Germany
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41
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Gaisano HY. Recent new insights into the role of SNARE and associated proteins in insulin granule exocytosis. Diabetes Obes Metab 2017; 19 Suppl 1:115-123. [PMID: 28880475 DOI: 10.1111/dom.13001] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 04/23/2017] [Accepted: 05/02/2017] [Indexed: 01/22/2023]
Abstract
Initial work on the exocytotic machinery of predocked insulin secretory granules (SGs) in pancreatic β-cells mimicked the SNARE hypothesis work in neurons, which includes SM/SNARE complex and associated priming proteins, fusion clamps and Ca2+ sensors. However, β-cell SGs, unlike neuronal synaptic vesicles, exhibit a biphasic secretory response that requires additional distinct features in exocytosis including newcomer SGs that undergo minimal docking time at the plasma membrane (PM) before fusion and multi-SG (compound) fusion. These exocytotic events are mediated by Munc18/SNARE complexes distinct from that which mediates predocked SG fusion. We review some recent insights in SNARE complex assembly and the promiscuity in SM/SNARE complex formation, whereby both contribute to conferring different insulin SG fusion kinetics. Some SNARE and associated proteins play non-fusion roles, including tethering SGs to Ca2+ channels, SG recruitment from cell interior to PM, and inhibitory SNAREs that block the action of profusion SNAREs. We discuss new insights into how sub-PM cytoskeletal mesh gates SG access to the PM and the targeting of SG exocytosis to PM domains in functionally polarized β-cells within intact islets. These recent developments have major implications on devising clever SNARE replacement therapies that could restore the deficient insulin secretion in diabetic islet β-cells.
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42
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Wheeler SE, Stacey HM, Nahaei Y, Hale SJ, Hardy AB, Reimann F, Gribble FM, Larraufie P, Gaisano HY, Brubaker PL. The SNARE Protein Syntaxin-1a Plays an Essential Role in Biphasic Exocytosis of the Incretin Hormone Glucagon-Like Peptide 1. Diabetes 2017; 66:2327-2338. [PMID: 28596237 PMCID: PMC6237272 DOI: 10.2337/db16-1403] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 06/01/2017] [Indexed: 02/02/2023]
Abstract
Exocytosis of the hormone glucagon-like peptide 1 (GLP-1) by the intestinal L cell is essential for the incretin effect after nutrient ingestion and is critical for the actions of dipeptidyl peptidase 4 inhibitors that enhance GLP-1 levels in patients with type 2 diabetes. Two-photon microscopy revealed that exocytosis of GLP-1 is biphasic, with a first peak at 1-6 min and a second peak at 7-12 min after stimulation with forskolin. Approximately 75% of the exocytotic events were represented by compound granule fusion, and the remainder were accounted for by full fusion of single granules under basal and stimulated conditions. The core SNARE protein syntaxin-1a (syn1a) was expressed by murine ileal L cells. At the single L-cell level, first-phase forskolin-induced exocytosis was reduced to basal (P < 0.05) and second-phase exocytosis abolished (P < 0.05) by syn1a knockout. L cells from intestinal-epithelial syn1a-deficient mice demonstrated a 63% reduction in forskolin-induced GLP-1 release in vitro (P < 0.001) and a 23% reduction in oral glucose-stimulated GLP-1 secretion (P < 0.05) in association with impairments in glucose-stimulated insulin release (by 60%; P < 0.01) and glucose tolerance (by 20%; P < 0.01). The findings identify an exquisite mechanism of metered secretory output that precisely regulates release of the incretin hormone GLP-1 and hence insulin secretion after a meal.
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Affiliation(s)
- Sarah E Wheeler
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Holly M Stacey
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Yasaman Nahaei
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Stephen J Hale
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | | | - Frank Reimann
- Wellcome Trust-MRC Institute of Metabolic Science, Metabolic Research Laboratories, University of Cambridge, Addenbrooke's Hospital, Cambridge, U.K
| | - Fiona M Gribble
- Wellcome Trust-MRC Institute of Metabolic Science, Metabolic Research Laboratories, University of Cambridge, Addenbrooke's Hospital, Cambridge, U.K
| | - Pierre Larraufie
- Wellcome Trust-MRC Institute of Metabolic Science, Metabolic Research Laboratories, University of Cambridge, Addenbrooke's Hospital, Cambridge, U.K
| | - Herbert Y Gaisano
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Patricia L Brubaker
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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43
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Abstract
Pancreatic islet β cells secrete insulin in response to nutrient secretagogues, like glucose, dependent on calcium influx and nutrient metabolism. One of the most intriguing qualities of β cells is their ability to use metabolism to amplify the amount of secreted insulin independent of further alterations in intracellular calcium. Many years studying this amplifying process have shaped our current understanding of β cell stimulus-secretion coupling; yet, the exact mechanisms of amplification have been elusive. Recent studies utilizing metabolomics, computational modeling, and animal models have progressed our understanding of the metabolic amplifying pathway of insulin secretion from the β cell. New approaches will be discussed which offer in-roads to a more complete model of β cell function. The development of β cell therapeutics may be aided by such a model, facilitating the targeting of aspects of the metabolic amplifying pathway which are unique to the β cell.
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Affiliation(s)
- Michael A Kalwat
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States.
| | - Melanie H Cobb
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States
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44
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Schifferer M, Yushchenko DA, Stein F, Bolbat A, Schultz C. A Ratiometric Sensor for Imaging Insulin Secretion in Single β Cells. Cell Chem Biol 2017; 24:525-531.e4. [PMID: 28366620 PMCID: PMC5404835 DOI: 10.1016/j.chembiol.2017.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 12/14/2016] [Accepted: 03/02/2017] [Indexed: 01/03/2023]
Abstract
Despite the urgent need for assays to visualize insulin secretion there is to date no reliable method available for measuring insulin release from single cells. To address this need, we developed a genetically encoded reporter termed RINS1 based on proinsulin superfolder GFP (sfGFP) and mCherry fusions for monitoring insulin secretion. RINS1 expression in MIN6 β cells resulted in proper processing yielding single-labeled insulin species. Unexpectedly, glucose or drug stimulation of insulin secretion in β cells led to the preferential release of the insulin-sfGFP construct, while the mCherry-fused C-peptide remained trapped in exocytic granules. This physical separation was used to monitor glucose-stimulated insulin secretion ratiometrically by total internal reflection fluorescence microscopy in single MIN6 and primary mouse β cells. Further, RINS1 enabled parallel monitoring of pulsatile insulin release in tolbutamide-treated β cells, demonstrating the potential of RINS1 for investigations of antidiabetic drug candidates at the single-cell level.
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Affiliation(s)
- Martina Schifferer
- Interdisciplinary Chemistry Group, Cell Biology & Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Dmytro A Yushchenko
- Interdisciplinary Chemistry Group, Cell Biology & Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany; Group of Chemical Biology, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo namesti 2, 16610 Prague 6, Czech Republic
| | - Frank Stein
- Interdisciplinary Chemistry Group, Cell Biology & Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Andrey Bolbat
- Interdisciplinary Chemistry Group, Cell Biology & Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Carsten Schultz
- Interdisciplinary Chemistry Group, Cell Biology & Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany; Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR 97237, USA.
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45
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Zhu D, Xie L, Kang Y, Dolai S, Bondo Hansen J, Qin T, Xie H, Liang T, Rubin DC, Osborne L, Gaisano HY. Syntaxin 2 Acts as Inhibitory SNARE for Insulin Granule Exocytosis. Diabetes 2017; 66:948-959. [PMID: 28115395 PMCID: PMC5860373 DOI: 10.2337/db16-0636] [Citation(s) in RCA: 19] [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: 05/18/2016] [Accepted: 12/24/2016] [Indexed: 01/03/2023]
Abstract
Of the four syntaxins specialized for exocytosis, syntaxin (Syn)-2 is the least understood. In this study, we used Syn-2/epimorphin knockout mice to examine the role of Syn-2 in insulin secretory granule (SG) exocytosis. Unexpectedly, Syn-2 knockout mice exhibited paradoxical superior glucose homeostasis resulting from an enhanced insulin secretion. This was confirmed in vitro by pancreatic islet perifusion showing an amplified biphasic glucose-stimulated insulin secretion arising from an increase in size of the readily releasable pool of insulin SGs and enhanced SG pool refilling. The increase in insulin exocytosis was attributed mainly to an enhanced recruitment of the larger pool of newcomer SGs that undergoes no residence time on plasma membrane before fusion and, to a lesser extent, also the predocked SGs. Consistently, Syn-2 depletion resulted in a stimulation-induced increase in abundance of exocytotic complexes we previously demonstrated as mediating the fusion of newcomer SGs (Syn-3/VAMP8/SNAP25/Munc18b) and predocked SGs (Syn-1A/VAMP2/SNAP25/Muncn18a). This work is the first to show in mammals that Syn-2 could function as an inhibitory SNARE protein that, when relieved, could promote exocytosis in pancreatic islet β-cells. Thus, Syn-2 may serve as a potential target to treat diabetes.
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Affiliation(s)
- Dan Zhu
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Li Xie
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Youhou Kang
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Subhankar Dolai
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | | | - Tairan Qin
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Huanli Xie
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Tao Liang
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Deborah C Rubin
- Department of Medicine, Washington University School of Medicine in St. Louis, St. Louis, MO
- Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, MO
| | - Lucy Osborne
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Herbert Y Gaisano
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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46
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Aslamy A, Thurmond DC. Exocytosis proteins as novel targets for diabetes prevention and/or remediation? Am J Physiol Regul Integr Comp Physiol 2017; 312:R739-R752. [PMID: 28356294 DOI: 10.1152/ajpregu.00002.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 03/24/2017] [Accepted: 03/24/2017] [Indexed: 12/17/2022]
Abstract
Diabetes remains one of the leading causes of morbidity and mortality worldwide, affecting an estimated 422 million adults. In the US, it is predicted that one in every three children born as of 2000 will suffer from diabetes in their lifetime. Type 2 diabetes results from combinatorial defects in pancreatic β-cell glucose-stimulated insulin secretion and in peripheral glucose uptake. Both processes, insulin secretion and glucose uptake, are mediated by exocytosis proteins, SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complexes, Sec1/Munc18 (SM), and double C2-domain protein B (DOC2B). Increasing evidence links deficiencies in these exocytosis proteins to diabetes in rodents and humans. Given this, emerging studies aimed at restoring and/or enhancing cellular levels of certain exocytosis proteins point to promising outcomes in maintaining functional β-cell mass and enhancing insulin sensitivity. In doing so, new evidence also shows that enhancing exocytosis protein levels may promote health span and longevity and may also harbor anti-cancer and anti-Alzheimer's disease capabilities. Herein, we present a comprehensive review of the described capabilities of certain exocytosis proteins and how these might be targeted for improving metabolic dysregulation.
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Affiliation(s)
- Arianne Aslamy
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana; and
| | - Debbie C Thurmond
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana; and .,Department of Molecular and Cellular Endocrinology, Beckman Research Institute of City of Hope, Duarte, California
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47
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Qin T, Liang T, Zhu D, Kang Y, Xie L, Dolai S, Sugita S, Takahashi N, Ostenson CG, Banks K, Gaisano HY. Munc18b Increases Insulin Granule Fusion, Restoring Deficient Insulin Secretion in Type-2 Diabetes Human and Goto-Kakizaki Rat Islets with Improvement in Glucose Homeostasis. EBioMedicine 2017; 16:262-274. [PMID: 28163042 PMCID: PMC5474508 DOI: 10.1016/j.ebiom.2017.01.030] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 01/09/2017] [Accepted: 01/20/2017] [Indexed: 01/22/2023] Open
Abstract
Reduced pancreatic islet levels of Munc18a/SNARE complex proteins have been postulated to contribute to the deficient glucose-stimulated insulin secretion (GSIS) in type-2 diabetes (T2D). Whereas much previous work has purported Munc18a/SNARE complex (Syntaxin-1A/VAMP-2/SNAP25) to be primarily involved in predocked secretory granule (SG) fusion, less is known about newcomer SGs that undergo minimal docking time at the plasma membrane before fusion. Newcomer SG fusion has been postulated to involve a distinct SM/SNARE complex (Munc18b/Syntaxin-3/VAMP8/SNAP25), whose levels we find also reduced in islets of T2D humans and T2D Goto-Kakizaki (GK) rats. Munc18b overexpression by adenovirus infection (Ad-Munc18b), by increasing assembly of Munc18b/SNARE complexes, mediated increased fusion of not only newcomer SGs but also predocked SGs in T2D human and GK rat islets, resulting in rescue of the deficient biphasic GSIS. Infusion of Ad-Munc18b into GK rat pancreas led to sustained improvement in glucose homeostasis. However, Munc18b overexpression in normal islets increased only newcomer SG fusion. Therefore, Munc18b could potentially be deployed in human T2D to rescue the deficient GSIS. Human T2D islet β-cells exhibit reduced fusion of predocked & newcomer secretory granules (SGs). Munc18b increases SNARE complexes involved in fusions of both newcomer & predocked SGs. Munc18b rescue of newcomer & predocked SGs increased biphasic secretion in human T2D β-cells. Munc18b rescue of T2D Goto-Kakizaki rat β-cell secretion improves glucose homeostasis.
Deficient insulin secretion from pancreatic islet β-cells in type-2 diabetes (T2D) is partly due to reduced expression of many proteins that assemble into specific complexes that mediate fusion of insulin secretory granules (SGs) with plasma membrane, termed exocytosis. We here show we can infuse a virus that contains the construct of one of the SG fusion proteins, Munc18b, into pancreatic ducts of T2D rats to reach the islets, which restored insulin secretion and improved glycemic control. Munc18b acts to promote the assembly of SG fusion complexes. This strategy could potentially be applied to treat human T2D by endoscopic infusion.
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Affiliation(s)
- Tairan Qin
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Tao Liang
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Dan Zhu
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Youhou Kang
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Li Xie
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Subhankar Dolai
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Shuzo Sugita
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Division of Fundamental Neurobiology, University Health Network, Toronto, ON M5T 2S8, Canada
| | - Noriko Takahashi
- Laboratory of Physiological Chemistry, Institute of Medicinal Chemistry, Hoshi University, Shinagawa, Tokyo 142-8501, Japan
| | - Claes-Goran Ostenson
- Department of Molecular Medicine and Surgery, Endocrinology and Diabetology Unit, Karolinska Institutet, Karolinska University Hospital, SE-171 76 Stockholm, Sweden
| | - Kate Banks
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Division of Comparative Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Herbert Y Gaisano
- Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada.
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48
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Liang T, Qin T, Xie L, Dolai S, Zhu D, Prentice KJ, Wheeler M, Kang Y, Osborne L, Gaisano HY. New Roles of Syntaxin-1A in Insulin Granule Exocytosis and Replenishment. J Biol Chem 2016; 292:2203-2216. [PMID: 28031464 DOI: 10.1074/jbc.m116.769885] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Indexed: 01/14/2023] Open
Abstract
In type-2 diabetes (T2D), severely reduced islet syntaxin-1A (Syn-1A) levels contribute to insulin secretory deficiency. We generated β-cell-specific Syn-1A-KO (Syn-1A-βKO) mice to mimic β-cell Syn-1A deficiency in T2D. Glucose tolerance tests showed that Syn-1A-βKO mice exhibited blood glucose elevation corresponding to reduced blood insulin levels. Perifusion of Syn-1A-βKO islets showed impaired first- and second-phase glucose-stimulated insulin secretion (GSIS) resulting from reduction in readily releasable pool and granule pool refilling. To unequivocally determine the β-cell exocytotic defects caused by Syn-1A deletion, EM and total internal reflection fluorescence microscopy showed that Syn-1A-KO β-cells had a severe reduction in the number of secretory granules (SGs) docked onto the plasma membrane (PM) at rest and reduced SG recruitment to the PM after glucose stimulation, the latter indicating defects in replenishment of releasable pools required to sustain second-phase GSIS. Whereas reduced predocked SG fusion accounted for reduced first-phase GSIS, selective reduction of exocytosis of short-dock (but not no-dock) newcomer SGs accounted for the reduced second-phase GSIS. These Syn-1A actions on newcomer SGs were partly mediated by Syn-1A interactions with newcomer SG VAMP8.
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Affiliation(s)
- Tao Liang
- From the Departments of Medicine.,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Tairan Qin
- From the Departments of Medicine.,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Li Xie
- From the Departments of Medicine.,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Subhankar Dolai
- From the Departments of Medicine.,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Dan Zhu
- From the Departments of Medicine.,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Kacey J Prentice
- Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Michael Wheeler
- Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Youhou Kang
- From the Departments of Medicine.,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Lucy Osborne
- From the Departments of Medicine.,Molecular Genetics, and
| | - Herbert Y Gaisano
- From the Departments of Medicine, .,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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49
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Kunii M, Ohara-Imaizumi M, Takahashi N, Kobayashi M, Kawakami R, Kondoh Y, Shimizu T, Simizu S, Lin B, Nunomura K, Aoyagi K, Ohno M, Ohmuraya M, Sato T, Yoshimura SI, Sato K, Harada R, Kim YJ, Osada H, Nemoto T, Kasai H, Kitamura T, Nagamatsu S, Harada A. Opposing roles for SNAP23 in secretion in exocrine and endocrine pancreatic cells. J Cell Biol 2016; 215:121-138. [PMID: 27697926 PMCID: PMC5057288 DOI: 10.1083/jcb.201604030] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 08/26/2016] [Indexed: 12/17/2022] Open
Abstract
Kunii et al. reveal that the SNARE protein SNAP23 plays distinct roles in the secretion of amylase in exocrine cells and of insulin in endocrine cells the pancreas and show that MF286, a novel inhibitor of SNAP23, may be a new drug candidate for diabetes. The membrane fusion of secretory granules with plasma membranes is crucial for the exocytosis of hormones and enzymes. Secretion disorders can cause various diseases such as diabetes or pancreatitis. Synaptosomal-associated protein 23 (SNAP23), a soluble N-ethyl-maleimide sensitive fusion protein attachment protein receptor (SNARE) molecule, is essential for secretory granule fusion in several cell lines. However, the in vivo functions of SNAP23 in endocrine and exocrine tissues remain unclear. In this study, we show opposing roles for SNAP23 in secretion in pancreatic exocrine and endocrine cells. The loss of SNAP23 in the exocrine and endocrine pancreas resulted in decreased and increased fusion of granules to the plasma membrane after stimulation, respectively. Furthermore, we identified a low molecular weight compound, MF286, that binds specifically to SNAP23 and promotes insulin secretion in mice. Our results demonstrate opposing roles for SNAP23 in the secretion mechanisms of the endocrine and exocrine pancreas and reveal that the SNAP23-binding compound MF286 may be a promising drug for diabetes treatment.
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Affiliation(s)
- Masataka Kunii
- Laboratory of Molecular Traffic, Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Mica Ohara-Imaizumi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Graduate School of Medicine, Center for Disease Biology and Integrative Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Masaki Kobayashi
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan
| | - Ryosuke Kawakami
- Laboratory of Molecular and Cellular Biophysics, Research Institute for Electronic Science, Hokkaido University, Hokkaido 001-0020, Japan
| | - Yasumitsu Kondoh
- Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, Saitama 351-0198, Japan
| | - Takeshi Shimizu
- Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, Saitama 351-0198, Japan
| | - Siro Simizu
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, Kanagawa 223-8522, Japan
| | - Bangzhong Lin
- Drug Discovery Team, Office for University-Industry Collaboration Planning and Promotion, Osaka University, Osaka 565-0871, Japan
| | - Kazuto Nunomura
- Drug Discovery Team, Office for University-Industry Collaboration Planning and Promotion, Osaka University, Osaka 565-0871, Japan
| | - Kyota Aoyagi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Mitsuyo Ohno
- Laboratory of Structural Physiology, Graduate School of Medicine, Center for Disease Biology and Integrative Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Masaki Ohmuraya
- Institute of Resource Development and Analysis, Kumamoto University, Kumamoto 860-0811, Japan
| | - Takashi Sato
- Laboratory of Molecular Traffic, Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan
| | - Shin-Ichiro Yoshimura
- Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Ken Sato
- Laboratory of Molecular Traffic, Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan
| | - Reiko Harada
- Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan Department of Judo Therapy, Takarazuka University of Medical and Health Care, Hyogo 666-0152, Japan
| | - Yoon-Jeong Kim
- Drug Discovery Team, Office for University-Industry Collaboration Planning and Promotion, Osaka University, Osaka 565-0871, Japan
| | - Hiroyuki Osada
- Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, Saitama 351-0198, Japan
| | - Tomomi Nemoto
- Laboratory of Molecular and Cellular Biophysics, Research Institute for Electronic Science, Hokkaido University, Hokkaido 001-0020, Japan
| | - Haruo Kasai
- Laboratory of Structural Physiology, Graduate School of Medicine, Center for Disease Biology and Integrative Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Tadahiro Kitamura
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan
| | - Shinya Nagamatsu
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Akihiro Harada
- Laboratory of Molecular Traffic, Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
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50
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Aoyagi K, Ohara-Imaizumi M, Itakura M, Torii S, Akimoto Y, Nishiwaki C, Nakamichi Y, Kishimoto T, Kawakami H, Harada A, Takahashi M, Nagamatsu S. VAMP7 Regulates Autophagy to Maintain Mitochondrial Homeostasis and to Control Insulin Secretion in Pancreatic β-Cells. Diabetes 2016; 65:1648-59. [PMID: 26953164 DOI: 10.2337/db15-1207] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 03/03/2016] [Indexed: 11/13/2022]
Abstract
VAMP7 is a SNARE protein that mediates specific membrane fusions in intracellular trafficking and was recently reported to regulate autophagosome formation. However, its function in pancreatic β-cells is largely unknown. To elucidate the physiological role of VAMP7 in β-cells, we generated pancreatic β-cell-specific VAMP7 knockout (Vamp7(flox/Y);Cre) mice. VAMP7 deletion impaired glucose-stimulated ATP production and insulin secretion, though VAMP7 was not localized to insulin granules. VAMP7-deficient β-cells showed defective autophagosome formation and reduced mitochondrial function. p62/SQSTM1, a marker protein for defective autophagy, was selectively accumulated on mitochondria in VAMP7-deficient β-cells. These findings suggest that accumulation of dysfunctional mitochondria that are degraded by autophagy caused impairment of glucose-stimulated ATP production and insulin secretion in Vamp7(flox/Y);Cre β-cells. Feeding a high-fat diet to Vamp7(flox/Y);Cre mice exacerbated mitochondrial dysfunction, further decreased ATP production and insulin secretion, and consequently induced glucose intolerance. Moreover, we found upregulated VAMP7 expression in wild-type mice fed a high-fat diet and in db/db mice, a model for diabetes. Thus our data indicate that VAMP7 regulates autophagy to maintain mitochondrial quality and insulin secretion in response to pathological stress in β-cells.
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Affiliation(s)
- Kyota Aoyagi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Mica Ohara-Imaizumi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Makoto Itakura
- Department of Biochemistry, Kitasato University School of Medicine, Kanagawa, Japan
| | - Seiji Torii
- Biosignal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Yoshihiro Akimoto
- Department of Anatomy, Kyorin University School of Medicine, Tokyo, Japan
| | - Chiyono Nishiwaki
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Yoko Nakamichi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Takuma Kishimoto
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Hayato Kawakami
- Department of Anatomy, Kyorin University School of Medicine, Tokyo, Japan
| | - Akihiro Harada
- Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Masami Takahashi
- Department of Biochemistry, Kitasato University School of Medicine, Kanagawa, Japan
| | - Shinya Nagamatsu
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
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