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Asadi F, Gunawardana SC, Dolle RE, Piston DW. An orally available compound suppresses glucagon hypersecretion and normalizes hyperglycemia in type 1 diabetes. JCI Insight 2024; 9:e172626. [PMID: 38258903 PMCID: PMC10906223 DOI: 10.1172/jci.insight.172626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 12/05/2023] [Indexed: 01/24/2024] Open
Abstract
Suppression of glucagon hypersecretion can normalize hyperglycemia during type 1 diabetes (T1D). Activating erythropoietin-producing human hepatocellular receptor type-A4 (EphA4) on α cells reduced glucagon hypersecretion from dispersed α cells and T1D islets from both human donor and mouse models. We synthesized a high-affinity small molecule agonist for the EphA4 receptor, WCDD301, which showed robust plasma and liver microsome metabolic stability in both mouse and human preparations. In islets and dispersed islet cells from nondiabetic and T1D human donors, WCDD301 reduced glucagon secretion comparable to the natural EphA4 ligand, Ephrin-A5. In diabetic NOD and streptozotocin-treated mice, once-daily oral administration of WCDD301 formulated with a time-release excipient reduced plasma glucagon and normalized blood glucose for more than 3 months. These results suggest that targeting the α cell EphA4 receptor by sustained release of WCDD301 is a promising pharmacologic pathway for normalizing hyperglycemia in patients with T1D.
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Affiliation(s)
| | | | - Roland E. Dolle
- Center for Drug Discovery, Washington University School of Medicine, St. Louis, Missouri, USA
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2
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Polino AJ, Ng XW, Rooks R, Piston DW. Disrupting actin filaments enhances glucose-stimulated insulin secretion independent of the cortical actin cytoskeleton. J Biol Chem 2023; 299:105334. [PMID: 37827287 PMCID: PMC10641669 DOI: 10.1016/j.jbc.2023.105334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 09/17/2023] [Accepted: 10/02/2023] [Indexed: 10/14/2023] Open
Abstract
Just under the plasma membrane of most animal cells lies a dense meshwork of actin filaments called the cortical cytoskeleton. In insulin-secreting pancreatic β cells, a long-standing model posits that the cortical actin layer primarily acts to restrict access of insulin granules to the plasma membrane. Here we test this model and find that stimulating β cells with pro-secretory stimuli (glucose and/or KCl) has little impact on the cortical actin layer. Chemical perturbations of actin polymerization, by either disrupting or enhancing filamentation, dramatically enhance glucose-stimulated insulin secretion. Using scanning electron microscopy, we directly visualize the cortical cytoskeleton, allowing us to validate the effect of these filament-disrupting chemicals. We find the state of the cortical actin layer does not correlate with levels of insulin secretion, suggesting filament disruptors act on insulin secretion independently of the cortical cytoskeleton.
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Affiliation(s)
- Alexander J Polino
- Department of Cell Biology & Physiology, Washington University School of Medicine, St Louis, Missouri, USA
| | - Xue Wen Ng
- Department of Cell Biology & Physiology, Washington University School of Medicine, St Louis, Missouri, USA
| | - Rebecca Rooks
- Department of Cell Biology & Physiology, Washington University School of Medicine, St Louis, Missouri, USA
| | - David W Piston
- Department of Cell Biology & Physiology, Washington University School of Medicine, St Louis, Missouri, USA.
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3
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Polino AJ, Wen Ng X, Rooks R, Piston DW. Disrupting actin filaments enhances glucose-stimulated insulin secretion independent of the cortical actin cytoskeleton. bioRxiv 2023:2023.07.15.549141. [PMID: 37502863 PMCID: PMC10369950 DOI: 10.1101/2023.07.15.549141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Just under the plasma membrane of most animal cells lies a dense meshwork of actin filaments called the cortical cytoskeleton. In insulin-secreting pancreatic β cells, a longstanding model posits that the cortical actin layer primarily acts to restrict access of insulin granules to the plasma membrane. Here we test this model and find that stimulating β cells with pro-secretory stimuli (glucose and/or KCl) has little impact on the cortical actin layer. Chemical perturbations of actin polymerization, by either disrupting or enhancing filamentation, dramatically enhances glucose-stimulated insulin secretion. We find that this enhancement does not correlate with the state of the cortical actin layer, suggesting filament disruptors act on insulin secretion independently of the cortical cytoskeleton.
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Affiliation(s)
| | | | | | - David W. Piston
- Department of Cell Biology & Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
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4
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Cheng J, McMahon SM, Piston DW, Jackson MB. Comparing confocal and two-photon Ca 2+ imaging of thin low-scattering preparations. Biophys Rep (N Y) 2023; 3:100109. [PMID: 37213258 PMCID: PMC10192416 DOI: 10.1016/j.bpr.2023.100109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Ca2+ imaging provides insight into biological processes ranging from subcellular dynamics to neural network activity. Two-photon microscopy has assumed a dominant role in Ca2+ imaging. The longer wavelength infra-red illumination undergoes less scattering, and absorption is confined to the focal plane. Two-photon imaging can thus penetrate thick tissue ∼10-fold more deeply than single-photon visible imaging to make two-photon microscopy an exceptionally powerful method for probing function in intact brain. However, two-photon excitation produces photobleaching and photodamage that increase very steeply with light intensity, limiting how strongly one can illuminate. In thin samples, illumination intensity can assume a dominant role in determining signal quality, raising the possibility that single-photon microscopy may be preferable. We therefore tested laser scanning single-photon and two-photon microscopy side by side with Ca2+ imaging in neuronal compartments at the surface of a brain slice. We optimized illumination intensity for each light source to obtain the brightest signal without photobleaching. Intracellular Ca2+ rises elicited by one action potential had twice the signal/noise ratio with confocal as with two-photon imaging in axons, were 31% higher in dendrites, and about the same in cell bodies. The superior performance of confocal imaging in finer neuronal processes likely reflects the dominance of shot noise when fluorescence is dim. Thus, when out-of-focus absorption and scattering are not issues, single-photon confocal imaging can yield better quality signals than two-photon microscopy.
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Affiliation(s)
- Jinbo Cheng
- Department of Neuroscience, University of Wisconsin, Madison, Wisconsin
| | - Shane M McMahon
- Department of Neuroscience, University of Wisconsin, Madison, Wisconsin
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri
| | - Meyer B Jackson
- Department of Neuroscience, University of Wisconsin, Madison, Wisconsin
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5
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Polino AJ, Sviben S, Melena I, Piston DW, Hughes JW. Scanning electron microscopy of human islet cilia. Proc Natl Acad Sci U S A 2023; 120:e2302624120. [PMID: 37205712 PMCID: PMC10235940 DOI: 10.1073/pnas.2302624120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 04/12/2023] [Indexed: 05/21/2023] Open
Abstract
Human islet primary cilia are vital glucose-regulating organelles whose structure remains uncharacterized. Scanning electron microscopy (SEM) is a useful technique for studying the surface morphology of membrane projections like cilia, but conventional sample preparation does not reveal the submembrane axonemal structure, which holds key implications for ciliary function. To overcome this challenge, we combined SEM with membrane-extraction techniques to examine primary cilia in native human islets. Our data show well-preserved cilia subdomains which demonstrate both expected and unexpected ultrastructural motifs. Morphometric features were quantified when possible, including axonemal length and diameter, microtubule conformations, and chirality. We further describe a ciliary ring, a structure that may be a specialization in human islets. Key findings are correlated with fluorescence microscopy and interpreted in the context of cilia function as a cellular sensor and communications locus in pancreatic islets.
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Affiliation(s)
- Alexander J. Polino
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO63110
| | - Sanja Sviben
- Washington University Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO63110
| | - Isabella Melena
- Department of Medicine, Washington University School of Medicine, Saint Louis, MO63110
| | - David W. Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO63110
| | - Jing W. Hughes
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO63110
- Department of Medicine, Washington University School of Medicine, Saint Louis, MO63110
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Dong G, Adak S, Spyropoulos G, Zhang Q, Feng C, Yin L, Speck SL, Shyr Z, Morikawa S, Kitamura RA, Kathayat RS, Dickinson BC, Ng XW, Piston DW, Urano F, Remedi MS, Wei X, Semenkovich CF. Palmitoylation couples insulin hypersecretion with β cell failure in diabetes. Cell Metab 2023; 35:332-344.e7. [PMID: 36634673 PMCID: PMC9908855 DOI: 10.1016/j.cmet.2022.12.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 10/14/2022] [Accepted: 12/15/2022] [Indexed: 01/13/2023]
Abstract
Hyperinsulinemia often precedes type 2 diabetes. Palmitoylation, implicated in exocytosis, is reversed by acyl-protein thioesterase 1 (APT1). APT1 biology was altered in pancreatic islets from humans with type 2 diabetes, and APT1 knockdown in nondiabetic islets caused insulin hypersecretion. APT1 knockout mice had islet autonomous increased glucose-stimulated insulin secretion that was associated with prolonged insulin granule fusion. Using palmitoylation proteomics, we identified Scamp1 as an APT1 substrate that localized to insulin secretory granules. Scamp1 knockdown caused insulin hypersecretion. Expression of a mutated Scamp1 incapable of being palmitoylated in APT1-deficient cells rescued insulin hypersecretion and nutrient-induced apoptosis. High-fat-fed islet-specific APT1-knockout mice and global APT1-deficient db/db mice showed increased β cell failure. These findings suggest that APT1 is regulated in human islets and that APT1 deficiency causes insulin hypersecretion leading to β cell failure, modeling the evolution of some forms of human type 2 diabetes.
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Affiliation(s)
- Guifang Dong
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA; Hubei Key Laboratory of Animal Nutrition and Feed Science, Wuhan Polytechnic University, Wuhan 430023, China
| | - Sangeeta Adak
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - George Spyropoulos
- Department of Pediatrics, Washington University, St. Louis, MO 63110, USA
| | - Qiang Zhang
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Chu Feng
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Li Yin
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Sarah L Speck
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Zeenat Shyr
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Shuntaro Morikawa
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Rie Asada Kitamura
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Rahul S Kathayat
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Bryan C Dickinson
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Xue Wen Ng
- Department of Cell Biology & Physiology, Washington University, St. Louis, MO 63110, USA
| | - David W Piston
- Department of Cell Biology & Physiology, Washington University, St. Louis, MO 63110, USA
| | - Fumihiko Urano
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA; Department of Pathology & Immunology, Washington University, St. Louis, MO 63110, USA
| | - Maria S Remedi
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA; Department of Cell Biology & Physiology, Washington University, St. Louis, MO 63110, USA
| | - Xiaochao Wei
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA.
| | - Clay F Semenkovich
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA; Department of Cell Biology & Physiology, Washington University, St. Louis, MO 63110, USA.
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Matamoros M, Ng XW, Brettmann JB, Piston DW, Nichols CG. Conformational plasticity of NaK2K and TREK2 potassium channel selectivity filters. Nat Commun 2023; 14:89. [PMID: 36609575 PMCID: PMC9822992 DOI: 10.1038/s41467-022-35756-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 12/23/2022] [Indexed: 01/07/2023] Open
Abstract
The K+ channel selectivity filter (SF) is defined by TxGYG amino acid sequences that generate four identical K+ binding sites (S1-S4). Only two sites (S3, S4) are present in the non-selective bacterial NaK channel, but a four-site K+-selective SF is obtained by mutating the wild-type TVGDGN SF sequence to a canonical K+ channel TVGYGD sequence (NaK2K mutant). Using single molecule FRET (smFRET), we show that the SF of NaK2K, but not of non-selective NaK, is ion-dependent, with the constricted SF configuration stabilized in high K+ conditions. Patch-clamp electrophysiology and non-canonical fluorescent amino acid incorporation show that NaK2K selectivity is reduced by crosslinking to limit SF conformational movement. Finally, the eukaryotic K+ channel TREK2 SF exhibits essentially identical smFRET-reported ion-dependent conformations as in prokaryotic K+ channels. Our results establish the generality of K+-induced SF conformational stability across the K+ channel superfamily, and introduce an approach to study manipulation of channel selectivity.
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Affiliation(s)
- Marcos Matamoros
- Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Xue Wen Ng
- Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Joshua B Brettmann
- Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA
- Millipore-Sigma Inc., St. Louis, MO, USA
| | - David W Piston
- Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Colin G Nichols
- Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA.
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA.
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Chen KH, Doliba N, May CL, Roman J, Ustione A, Tembo T, Negron A, Radovick S, Piston DW, Glaser B, Kaestner KH, Matschinsky FM. Genetic activation of glucokinase in a minority of pancreatic beta cells causes hypoglycemia in mice. Life Sci 2022; 309:120952. [PMID: 36100080 PMCID: PMC10312065 DOI: 10.1016/j.lfs.2022.120952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 09/06/2022] [Accepted: 09/08/2022] [Indexed: 01/05/2023]
Abstract
AIMS Glucokinase (GK) is expressed in the glucose-sensing cells of the islets of Langerhans and plays a critical role in glucose homeostasis. Here, we tested the hypothesis that genetic activation of GK in a small subset of β-cells is sufficient to change the glucose set-point of the whole islet. MATERIAL AND METHODS Mouse models of cell-type specific GK deficiency (GKKO) and genetic enzyme activation (GKKI) in a subset of β-cells were obtained by crossing the αGSU (gonadotropin alpha subunit)-Cre transgene with the appropriate GK mutant alleles. Metabolic analyses consisted of glucose tolerance tests, perifusion of isolated islets and intracellular calcium measurements. KEY FINDINGS The αGSU-Cre transgene produced genetically mosaic islets, as Cre was active in 15 ± 1.2 % of β-cells. While mice deficient for GK in a subset of islet cells were normal, unexpectedly, GKKI mice were chronically hypoglycemic, glucose intolerant, and had a lower threshold for glucose stimulated insulin secretion. GKKI mice exhibited an average fasting blood glucose level of 3.5 mM. GKKI islets responded with intracellular calcium signals that spread through the whole islets at 1 mM and secreted insulin at 3 mM glucose. SIGNIFICANCE Genetic activation of GK in a minority of β-cells is sufficient to change the glucose threshold for insulin secretion in the entire islet and thereby glucose homeostasis in the whole animal. These data support the model in which β-cells with higher GK activity function as 'hub' or 'trigger' cells and thus control insulin secretion by the β-cell collective within the islet.
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Affiliation(s)
- Kevin H Chen
- Department of Biochemistry and Biophysics and Institute for Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA 19014, USA
| | - Nicolai Doliba
- Department of Biochemistry and Biophysics and Institute for Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA 19014, USA
| | - Catherine L May
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA 19014, USA
| | - Jeffrey Roman
- Department of Biochemistry and Biophysics and Institute for Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA 19014, USA
| | - Alessandro Ustione
- Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Teguru Tembo
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA 19014, USA
| | - Ariel Negron
- Department of Medicine and Pediatrics, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
| | - Sally Radovick
- Department of Medicine and Pediatrics, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Benjamin Glaser
- Endocrinology and Metabolism Department, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Klaus H Kaestner
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA 19014, USA.
| | - Franz M Matschinsky
- Department of Biochemistry and Biophysics and Institute for Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA 19014, USA.
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Ng XW, Chung YH, Asadi F, Kong C, Ustione A, Piston DW. RhoA as a Signaling Hub Controlling Glucagon Secretion From Pancreatic α-Cells. Diabetes 2022; 71:2384-2394. [PMID: 35904939 PMCID: PMC9630081 DOI: 10.2337/db21-1010] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 07/26/2022] [Indexed: 11/13/2022]
Abstract
Glucagon hypersecretion from pancreatic islet α-cells exacerbates hyperglycemia in type 1 diabetes (T1D) and type 2 diabetes. Still, the underlying mechanistic pathways that regulate glucagon secretion remain controversial. Among the three complementary main mechanisms (intrinsic, paracrine, and juxtacrine) proposed to regulate glucagon release from α-cells, juxtacrine interactions are the least studied. It is known that tonic stimulation of α-cell EphA receptors by ephrin-A ligands (EphA forward signaling) inhibits glucagon secretion in mouse and human islets and restores glucose inhibition of glucagon secretion in sorted mouse α-cells, and these effects correlate with increased F-actin density. Here, we elucidate the downstream target of EphA signaling in α-cells. We demonstrate that RhoA, a Rho family GTPase, plays a key role in this pathway. Pharmacological inhibition of RhoA disrupts glucose inhibition of glucagon secretion in islets and decreases cortical F-actin density in dispersed α-cells and α-cells in intact islets. Quantitative FRET biosensor imaging shows that increased RhoA activity follows directly from EphA stimulation. We show that in addition to modulating F-actin density, EphA forward signaling and RhoA activity affect α-cell Ca2+ activity in a novel mechanistic pathway. Finally, we show that stimulating EphA forward signaling restores glucose inhibition of glucagon secretion from human T1D donor islets.
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Affiliation(s)
| | | | | | | | | | - David W. Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO
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10
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Kebede MA, Piston DW. Sorting Out the Receptor Isoforms Underlying Dopamine Inhibition of Insulin Secretion. Diabetes 2022; 71:1831-1833. [PMID: 35984964 DOI: 10.2337/dbi22-0018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 06/10/2022] [Indexed: 11/13/2022]
Affiliation(s)
- Melkam A Kebede
- Discipline of Physiology, School of Medical Sciences, Charles Perkins Centre, The University of Sydney, Camperdown, Sydney, Australia
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, MO
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11
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Kelly KP, Borsetti H, Wenzler ME, Ustione A, Kim K, Christov PP, Ramirez B, Bauer JA, Piston DW, Johnson CH, Sulikowski GA. Screen for Small-Molecule Modulators of Circadian Rhythms Reveals Phenazine as a Redox-State Modifying Clockwork Tuner. ACS Chem Biol 2022; 17:1658-1664. [PMID: 35679588 PMCID: PMC9398883 DOI: 10.1021/acschembio.2c00240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A high-throughput cell-based screen identified redox-active small molecules that produce a period lengthening of the circadian rhythm. The strongest period lengthening phenotype was induced by a phenazine carboxamide (VU661). Comparison to two isomeric benzquinoline carboxamides (VU673 and VU164) shows the activity is associated with the redox modulating phenazine functionality. Furthermore, ex vivo cell analysis using optical redox ratio measurements shows the period lengthening phenotype to be associated with a shift to the NAD/FAD oxidation state of nicotinamide and flavine coenzymes.
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Affiliation(s)
| | | | | | - Alessandro Ustione
- Department of Cell Biology & Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, United States
| | - Kwangho Kim
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States,Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Plamen P. Christov
- Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Bianca Ramirez
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Joshua A. Bauer
- Vanderbilt Institute of Chemical Biology and Department of Biochemistry, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - David W. Piston
- Department of Cell Biology & Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, United States
| | - Carl Hirschie Johnson
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, United States; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Gary A. Sulikowski
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
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12
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Wen Ng X, DiGruccio MR, Piston DW. Role of complexin 2 in the regulation of pancreatic islet cell physiology. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.2292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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13
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Abstract
Blood glucose homeostasis requires proper function of pancreatic islets, which secrete insulin, glucagon, and somatostatin from the β-, α-, and δ-cells, respectively. Each islet cell type is equipped with intrinsic mechanisms for glucose sensing and secretory actions, but these intrinsic mechanisms alone cannot explain the observed secretory profiles from intact islets. Regulation of secretion involves interconnected mechanisms among and between islet cell types. Islet cells lose their normal functional signatures and secretory behaviors upon dispersal as compared to intact islets and in vivo. In dispersed islet cells, the glucose response of insulin secretion is attenuated from that seen from whole islets, coordinated oscillations in membrane potential and intracellular Ca2+ activity, as well as the two-phase insulin secretion profile, are missing, and glucagon secretion displays higher basal secretion profile and a reverse glucose-dependent response from that of intact islets. These observations highlight the critical roles of intercellular communication within the pancreatic islet, and how these communication pathways are crucial for proper hormonal and nonhormonal secretion and glucose homeostasis. Further, misregulated secretions of islet secretory products that arise from defective intercellular islet communication are implicated in diabetes. Intercellular communication within the islet environment comprises multiple mechanisms, including electrical synapses from gap junctional coupling, paracrine interactions among neighboring cells, and direct cell-to-cell contacts in the form of juxtacrine signaling. In this article, we describe the various mechanisms that contribute to proper islet function for each islet cell type and how intercellular islet communications are coordinated among the same and different islet cell types. © 2021 American Physiological Society. Compr Physiol 11:2191-2225, 2021.
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Affiliation(s)
- Xue W Ng
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - Yong H Chung
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
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14
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Wen Ng X, DiGruccio MR, Piston DW. Quantification of Insulin Vesicle Dynamics, Fusion Events and Calcium Activity in Intact Mouse Islets. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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15
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Foust D, Piston DW. Number and Brightness Analysis with Spatial Filters. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.2225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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16
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Abreu D, Asada R, Revilla JMP, Lavagnino Z, Kries K, Piston DW, Urano F. Wolfram syndrome 1 gene regulates pathways maintaining beta-cell health and survival. J Transl Med 2020; 100:849-862. [PMID: 32060407 PMCID: PMC7286786 DOI: 10.1038/s41374-020-0408-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Revised: 02/03/2020] [Accepted: 02/04/2020] [Indexed: 12/17/2022] Open
Abstract
Wolfram Syndrome 1 (WFS1) protein is an endoplasmic reticulum (ER) factor whose deficiency results in juvenile-onset diabetes secondary to cellular dysfunction and apoptosis. The mechanisms guiding β-cell outcomes secondary to WFS1 function, however, remain unclear. Here, we show that WFS1 preserves normal β-cell physiology by promoting insulin biosynthesis and negatively regulating ER stress. Depletion of Wfs1 in vivo and in vitro causes functional defects in glucose-stimulated insulin secretion and insulin content, triggering Chop-mediated apoptotic pathways. Genetic proof of concept studies coupled with RNA-seq reveal that increasing WFS1 confers a functional and a survival advantage to β-cells under ER stress by increasing insulin gene expression and downregulating the Chop-Trib3 axis, thereby activating Akt pathways. Remarkably, WFS1 and INS levels are reduced in type-2 diabetic (T2DM) islets, suggesting that WFS1 may contribute to T2DM β-cell pathology. Taken together, this work reveals essential pathways regulated by WFS1 to control β-cell survival and function primarily through preservation of ER homeostasis.
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Affiliation(s)
- Damien Abreu
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO 63110, USA,Medical Scientist Training Program, Washington University School of Medicine, St. Louis, MO 63110, U.S.A
| | - Rie Asada
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO 63110, USA,Department of Biochemistry, Institute of Biomedical & Health Science, Hiroshima University, Hiroshima 734-8553, Japan
| | - John M. P. Revilla
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Zeno Lavagnino
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA,Experimental Imaging Center DIBIT, IRCCS Ospedale San Raffaele, 20132, Milan, Italy
| | - Kelly Kries
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - David W. Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Fumihiko Urano
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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17
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Hughes JW, Cho JH, Conway HE, DiGruccio MR, Ng XW, Roseman HF, Abreu D, Urano F, Piston DW. Primary cilia control glucose homeostasis via islet paracrine interactions. Proc Natl Acad Sci U S A 2020; 117:8912-8923. [PMID: 32253320 PMCID: PMC7184063 DOI: 10.1073/pnas.2001936117] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Pancreatic islets regulate glucose homeostasis through coordinated actions of hormone-secreting cells. What underlies the function of the islet as a unit is the close approximation and communication among heterogeneous cell populations, but the structural mediators of islet cellular cross talk remain incompletely characterized. We generated mice specifically lacking β-cell primary cilia, a cellular organelle that has been implicated in regulating insulin secretion, and found that the β-cell cilia are required for glucose sensing, calcium influx, insulin secretion, and cross regulation of α- and δ-cells. Protein expression profiling in islets confirms perturbation in these cellular processes and reveals additional targets of cilia-dependent signaling. At the organism level, the deletion of β-cell cilia disrupts circulating hormone levels, impairs glucose homeostasis and fuel usage, and leads to the development of diabetes. Together, these findings demonstrate that primary cilia not only orchestrate β-cell-intrinsic activity but also mediate cross talk both within the islet and from islets to other metabolic tissues, thus providing a unique role of cilia in nutrient metabolism and insight into the pathophysiology of diabetes.
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Affiliation(s)
- Jing W Hughes
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110;
| | - Jung Hoon Cho
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Hannah E Conway
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Michael R DiGruccio
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Xue Wen Ng
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Henry F Roseman
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Damien Abreu
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Fumihiko Urano
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
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18
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Foust DJ, Piston DW. N-Color Spatial Cumulant Analysis to Detect G-Protein Dynamics with Two-Photon Microscopy. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.1852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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19
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Ng XW, DiGruccio MR, Tkaczyk TS, Piston DW. Simultaneous Imaging of Insulin Vesicle Dynamics and Calcium Activity in Live Intact Mouse ISLETS by diSPIM. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.2579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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20
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Chung YH, Piston DW. RhoA Mediated Juxtacrine Regulation of Glucagon Secretion. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.1454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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21
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Verma M, Choi J, Cottrell KA, Lavagnino Z, Thomas EN, Pavlovic-Djuranovic S, Szczesny P, Piston DW, Zaher HS, Puglisi JD, Djuranovic S. A short translational ramp determines the efficiency of protein synthesis. Nat Commun 2019; 10:5774. [PMID: 31852903 PMCID: PMC6920384 DOI: 10.1038/s41467-019-13810-1] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 11/25/2019] [Indexed: 01/26/2023] Open
Abstract
Translation initiation is a major rate-limiting step for protein synthesis. However, recent studies strongly suggest that the efficiency of protein synthesis is additionally regulated by multiple factors that impact the elongation phase. To assess the influence of early elongation on protein synthesis, we employed a library of more than 250,000 reporters combined with in vitro and in vivo protein expression assays. Here we report that the identity of the amino acids encoded by codons 3 to 5 impact protein yield. This effect is independent of tRNA abundance, translation initiation efficiency, or overall mRNA structure. Single-molecule measurements of translation kinetics revealed pausing of the ribosome and aborted protein synthesis on codons 4 and 5 of distinct amino acid and nucleotide compositions. Finally, introduction of preferred sequence motifs only at specific codon positions improves protein synthesis efficiency for recombinant proteins. Collectively, our data underscore the critical role of early elongation events in translational control of gene expression. Several factors contribute to the efficiency of protein expression. Here the authors show that the identity of amino acids encoded by codons at position 3–5 significantly impact translation efficiency and protein expression levels.
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Affiliation(s)
- Manasvi Verma
- Department of Cell Biology and Physiology, Washington University School of Medicine, 600 South Euclid Avenue, Campus Box 8228, St. Louis, MO, 63110, USA
| | - Junhong Choi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, 94305-5126, USA.,Department of Applied Physics, Stanford University, Stanford, CA, 94305-5126, USA.,Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Kyle A Cottrell
- Department of Cell Biology and Physiology, Washington University School of Medicine, 600 South Euclid Avenue, Campus Box 8228, St. Louis, MO, 63110, USA
| | - Zeno Lavagnino
- Department of Cell Biology and Physiology, Washington University School of Medicine, 600 South Euclid Avenue, Campus Box 8228, St. Louis, MO, 63110, USA.,Experimental Imaging Center, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Erica N Thomas
- Department of Biology, Washington University, St Louis, MO, 63105, USA
| | - Slavica Pavlovic-Djuranovic
- Department of Cell Biology and Physiology, Washington University School of Medicine, 600 South Euclid Avenue, Campus Box 8228, St. Louis, MO, 63110, USA
| | - Pawel Szczesny
- Department of Bioinformatics, Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine, 600 South Euclid Avenue, Campus Box 8228, St. Louis, MO, 63110, USA
| | - Hani S Zaher
- Department of Biology, Washington University, St Louis, MO, 63105, USA
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, 94305-5126, USA
| | - Sergej Djuranovic
- Department of Cell Biology and Physiology, Washington University School of Medicine, 600 South Euclid Avenue, Campus Box 8228, St. Louis, MO, 63110, USA.
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22
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Emfinger CH, Lőrincz R, Wang Y, York NW, Singareddy SS, Ikle JM, Tryon RC, McClenaghan C, Shyr ZA, Huang Y, Reissaus CA, Meyer D, Piston DW, Hyrc K, Remedi MS, Nichols CG. Beta-cell excitability and excitability-driven diabetes in adult Zebrafish islets. Physiol Rep 2019; 7:e14101. [PMID: 31161721 PMCID: PMC6546968 DOI: 10.14814/phy2.14101] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 04/30/2019] [Accepted: 04/30/2019] [Indexed: 12/15/2022] Open
Abstract
Islet β-cell membrane excitability is a well-established regulator of mammalian insulin secretion, and defects in β-cell excitability are linked to multiple forms of diabetes. Evolutionary conservation of islet excitability in lower organisms is largely unexplored. Here we show that adult zebrafish islet calcium levels rise in response to elevated extracellular [glucose], with similar concentration-response relationship to mammalian β-cells. However, zebrafish islet calcium transients are nor well coupled, with a shallower glucose-dependence of cytoplasmic calcium concentration. We have also generated transgenic zebrafish that conditionally express gain-of-function mutations in ATP-sensitive K+ channels (KATP -GOF) in β-cells. Following induction, these fish become profoundly diabetic, paralleling features of mammalian diabetes resulting from equivalent mutations. KATP -GOF fish become severely hyperglycemic, with slowed growth, and their islets lose glucose-induced calcium responses. These results indicate that, although lacking tight cell-cell coupling of intracellular Ca2+ , adult zebrafish islets recapitulate similar excitability-driven β-cell glucose responsiveness to those in mammals, and exhibit profound susceptibility to diabetes as a result of inexcitability. While illustrating evolutionary conservation of islet excitability in lower vertebrates, these results also provide important validation of zebrafish as a suitable animal model in which to identify modulators of islet excitability and diabetes.
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Affiliation(s)
- Christopher H. Emfinger
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Department of MedicineDivision of Endocrinology, Metabolism, and Lipid ResearchWashington University in St. Louis School of MedicineSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Réka Lőrincz
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
- Institute of Molecular Biology/CMBILeopold‐Franzens‐University InnsbruckInnsbruckAustria
| | - Yixi Wang
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Nathaniel W. York
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Soma S. Singareddy
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Jennifer M. Ikle
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
- Department of PediatricsWashington University in St. Louis School of MedicineSt. LouisMissouri
- Present address:
Department of CardiologyRenmin Hospital of Wuhan UniversityWuhanChina
| | - Robert C. Tryon
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Conor McClenaghan
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Zeenat A. Shyr
- Department of MedicineDivision of Endocrinology, Metabolism, and Lipid ResearchWashington University in St. Louis School of MedicineSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Yan Huang
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
- Department of PediatricsWashington University in St. Louis School of MedicineSt. LouisMissouri
- Present address:
Department of CardiologyRenmin Hospital of Wuhan UniversityWuhanChina
| | - Christopher A. Reissaus
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
| | - Dirk Meyer
- Institute of Molecular Biology/CMBILeopold‐Franzens‐University InnsbruckInnsbruckAustria
| | - David W. Piston
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Krzysztof Hyrc
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Maria S. Remedi
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Department of MedicineDivision of Endocrinology, Metabolism, and Lipid ResearchWashington University in St. Louis School of MedicineSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Colin G. Nichols
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
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23
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Dyson HJ, Hall KB, Piston DW. Economics and Politics of Publishing in Our Mission-Driven Society. Biophys J 2019; 116:E1-E2. [DOI: 10.1016/j.bpj.2019.04.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 04/22/2019] [Indexed: 11/16/2022] Open
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24
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Hughes JW, Ustione A, Lavagnino Z, Piston DW. Regulation of islet glucagon secretion: Beyond calcium. Diabetes Obes Metab 2018; 20 Suppl 2:127-136. [PMID: 30230183 PMCID: PMC6148361 DOI: 10.1111/dom.13381] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 05/03/2018] [Accepted: 05/23/2018] [Indexed: 12/19/2022]
Abstract
The islet of Langerhans plays a key role in glucose homeostasis through regulated secretion of the hormones insulin and glucagon. Islet research has focused on the insulin-secreting β-cells, even though aberrant glucagon secretion from α-cells also contributes to the aetiology of diabetes. Despite its importance, the mechanisms controlling glucagon secretion remain controversial. Proper α-cell function requires the islet milieu, where β- and δ-cells drive and constrain α-cell dynamics. The response of glucagon to glucose is similar between isolated islets and that measured in vivo, so it appears that the glucose dependence requires only islet-intrinsic factors and not input from blood flow or the nervous system. Elevated intracellular free Ca2+ is needed for α-cell exocytosis, but interpreting Ca2+ data is tricky since it is heterogeneous among α-cells at all physiological glucose levels. Total Ca2+ activity in α-cells increases slightly with glucose, so Ca2+ may serve a permissive, rather than regulatory, role in glucagon secretion. On the other hand, cAMP is a more promising candidate for controlling glucagon secretion and is itself driven by paracrine signalling from β- and δ-cells. Another pathway, juxtacrine signalling through the α-cell EphA receptors, stimulated by β-cell ephrin ligands, leads to a tonic inhibition of glucagon secretion. We discuss potential combinations of Ca2+ , cAMP, paracrine and juxtacrine factors in the regulation of glucagon secretion, focusing on recent data in the literature that might unify the field towards a quantitative understanding of α-cell function.
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Affiliation(s)
- Jing W. Hughes
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Alessandro Ustione
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - Zeno Lavagnino
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - David W. Piston
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
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25
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Ustione A, Piston DW. The Interplay of Dopamine Receptors in the Pancreatic Islet Regulates Hormone Secretion. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.1629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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26
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Piston DW, Foust D, Godin A, Wiseman PW. Resolving Dopamine Receptor Dynamics with Spatial, Temporal, and Spectral Sampling. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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27
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Lavagnino Z, DiGruccio M, Piston DW. Light-Sheet Microscopy Allows Simultaneous Imaging of Second Messengers in Intact Pancreatic Islets. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.2993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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28
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Bechard ME, Bankaitis ED, Ustione A, Piston DW, Magnuson MA, Wright CVE. FUCCI tracking shows cell-cycle-dependent Neurog3 variation in pancreatic progenitors. Genesis 2018; 55. [PMID: 28772022 DOI: 10.1002/dvg.23050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 07/30/2017] [Indexed: 12/29/2022]
Abstract
During pancreas organogenesis, Neurog3HI endocrine-committing cells are generated from a population of Sox9+ mitotic progenitors with only a low level of Neurog3 transcriptional activity (Neurog3TA.LO ). Low-level Neurog3 protein, in Neurog3TA.LO cells, is required to maintain their mitotic endocrine-lineage-primed status. Herein, we describe a Neurog3-driven FUCCI cell-cycle reporter (Neurog3P2A.FUCCI ) derived from a Neurog3 BAC transgenic reporter that functions as a loxed cassette acceptor (LCA). In cycling Sox9+ Neurog3TA.LO progenitors, the majority of cells in S-G2 -M phases have undetectable levels of Neurog3 with increased expression of endocrine progenitor markers, while those in G1 have low Neurog3 levels with increased expression of endocrine differentiation markers. These findings support a model in which variations in Neurog3 protein levels are coordinated with cell-cycle phase progression in Neurog3TA.LO progenitors with entrance into G1 triggering a concerted effort, beyond increasing Neurog3 levels, to maintain an endocrine-lineage-primed state by initiating expression of the downstream endocrine differentiation program prior to endocrine-commitment.
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Affiliation(s)
- Matthew E Bechard
- Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Vanderbilt University Program in Developmental Biology, Nashville, Tennessee
| | - Eric D Bankaitis
- Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Vanderbilt University Program in Developmental Biology, Nashville, Tennessee
| | - Alessandro Ustione
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - David W Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Mark A Magnuson
- Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Vanderbilt University Program in Developmental Biology, Nashville, Tennessee.,Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Christopher V E Wright
- Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Vanderbilt University Program in Developmental Biology, Nashville, Tennessee
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29
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Elliott AD, Bedard N, Ustione A, Baird MA, Davidson MW, Tkaczyk T, Piston DW. Hyperspectral imaging for simultaneous measurements of two FRET biosensors in pancreatic β-cells. PLoS One 2017; 12:e0188789. [PMID: 29211763 PMCID: PMC5718502 DOI: 10.1371/journal.pone.0188789] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 11/13/2017] [Indexed: 01/09/2023] Open
Abstract
Fluorescent protein (FP) biosensors based on Förster resonance energy transfer (FRET) are commonly used to study molecular processes in living cells. There are FP-FRET biosensors for many cellular molecules, but it remains difficult to perform simultaneous measurements of multiple biosensors. The overlapping emission spectra of the commonly used FPs, including CFP/YFP and GFP/RFP make dual FRET measurements challenging. In addition, a snapshot imaging modality is required for simultaneous imaging. The Image Mapping Spectrometer (IMS) is a snapshot hyperspectral imaging system that collects high resolution spectral data and can be used to overcome these challenges. We have previously demonstrated the IMS’s capabilities for simultaneously imaging GFP and CFP/YFP-based biosensors in pancreatic β-cells. Here, we demonstrate a further capability of the IMS to image simultaneously two FRET biosensors with a single excitation band, one for cAMP and the other for Caspase-3. We use these measurements to measure simultaneously cAMP signaling and Caspase-3 activation in pancreatic β-cells during oxidative stress and hyperglycemia, which are essential components in the pathology of diabetes.
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Affiliation(s)
- Amicia D. Elliott
- National Institute of General Medical Sciences, Bethesda, MD, United States of America
| | - Noah Bedard
- Rice University, Bioengineering, Houston, TX, United States of America
| | - Alessandro Ustione
- Washington University in St. Louis, St. Louis, MO, United States of America
| | - Michelle A. Baird
- The Florida State University, National High Magnetic Field Laboratory, Tallahassee, FL, United States of America
| | - Michael W. Davidson
- The Florida State University, National High Magnetic Field Laboratory, Tallahassee, FL, United States of America
| | - Tomasz Tkaczyk
- Rice University, Bioengineering, Houston, TX, United States of America
| | - David W. Piston
- Washington University in St. Louis, St. Louis, MO, United States of America
- * E-mail:
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30
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Lavagnino Z, Dwight J, Ustione A, Nguyen TU, Tkaczyk TS, Piston DW. Snapshot Hyperspectral Light-Sheet Imaging of Signal Transduction in Live Pancreatic Islets. Biophys J 2017; 111:409-417. [PMID: 27463142 DOI: 10.1016/j.bpj.2016.06.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 05/30/2016] [Accepted: 06/16/2016] [Indexed: 01/22/2023] Open
Abstract
The observation of ionic signaling dynamics in intact pancreatic islets has contributed greatly to our understanding of both α- and β-cell function. Insulin secretion from β-cells depends on the firing of action potentials and consequent rises of intracellular calcium activity ([Ca(2+)]i). Zinc (Zn(2+)) is cosecreted with insulin, and has been postulated to play a role in cell-to-cell cross talk within an islet, in particular inhibiting glucagon secretion from α-cells. Thus, measuring [Ca(2+)]i and Zn(2+) dynamics from both α- and β-cells will elucidate mechanisms underlying islet hormone secretion. [Ca(2+)]i and intracellular Zn(2+) can be measured using fluorescent biosensors, but the most efficient sensors have overlapping spectra that complicate their discrimination. Hyperspectral imaging can be used to distinguish signals from multiple fluorophores, but available hyperspectral implementations are either too slow to measure the dynamics of ionic signals or not suitable for thick samples. We have developed a five-dimensional (x,y,z,t,λ) imaging system that leverages a snapshot hyperspectral imaging method, image mapping spectrometry, and light-sheet microscopy. This system provides subsecond temporal resolution from deep within multicellular structures. Using a single excitation wavelength (488 nm) we acquired images from triply labeled samples with two biosensors and a genetically expressing fluorescent protein (spectrally overlapping with one of the biosensors) with high temporal resolution. Measurements of [Ca(2+)]i and Zn(2+) within both α- and β-cells as a function of glucose concentration show heterogeneous uptake of Zn(2+) into α-cells that correlates to the known heterogeneities in [Ca(2+)]i. These differences in intracellular Zn(2+) among α-cells may contribute to the inhibition in glucagon secretion observed at elevated glucose levels.
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Affiliation(s)
- Zeno Lavagnino
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee; Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri
| | - Jason Dwight
- Department of Bioengineering, Rice University, Houston, Texas
| | - Alessandro Ustione
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee; Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri
| | | | | | - David W Piston
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee; Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri.
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Abstract
Misregulated hormone secretion from the islet of Langerhans is central to the pathophysiology of diabetes. Although insulin plays a key role in glucose regulation, the importance of glucagon is increasingly acknowledged. However, the mechanisms that regulate glucagon secretion from α-cells are still unclear. We used pseudoislets reconstituted from dispersed islet cells to study α-cells with and without various indirect effects from other islet cells. Dispersed islet cells secrete aberrant levels of glucagon and insulin at basal and elevated glucose levels. When cultured, murine islet cells reassociate to form pseudoislets, which recover normal glucose-regulated hormone secretion, and human islet cells follow a similar pattern. We created small (∼40-µm) pseudoislets using all of the islet cells or only some of the cell types, which allowed us to characterize novel aspects of regulated hormone secretion. The recovery of regulated glucagon secretion from α-cells in small pseudoislets depends upon the combined action of paracrine factors, such as insulin and somatostatin, and juxtacrine signals between EphA4/7 on α-cells and ephrins on β-cells. Although these signals modulate different pathways, both appear to be required for proper inhibition of glucagon secretion in response to glucose. This improved understanding of the modulation of glucagon secretion can provide novel therapeutic routes for the treatment of some individuals with diabetes.
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Affiliation(s)
- Christopher A Reissaus
- Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, MO, and Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - David W Piston
- Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, MO, and Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
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Lavagnino Z, Piston DW. Monitoring Calcium Activity in Intact Islet of Langherans α-Cells using a Genetically Encoded Biosensor and Light-Sheet Illumination Microscopy. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.1277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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33
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Foust DJ, Ustione A, Piston DW. Fluorescence Fluctuation Spectroscopy of Dopaminergic Signaling in Pancreatic Beta Cells. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Syring KE, Boortz KA, Oeser JK, Ustione A, Platt KA, Shadoan MK, McGuinness OP, Piston DW, Powell DR, O'Brien RM. Combined Deletion of Slc30a7 and Slc30a8 Unmasks a Critical Role for ZnT8 in Glucose-Stimulated Insulin Secretion. Endocrinology 2016; 157:4534-4541. [PMID: 27754787 PMCID: PMC5133349 DOI: 10.1210/en.2016-1573] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Polymorphisms in the SLC30A8 gene, which encodes the ZnT8 zinc transporter, are associated with altered susceptibility to type 2 diabetes (T2D), and SLC30A8 haploinsufficiency is protective against the development of T2D in obese humans. SLC30A8 is predominantly expressed in pancreatic islet β-cells, but surprisingly, multiple knockout mouse studies have shown little effect of Slc30a8 deletion on glucose tolerance or glucose-stimulated insulin secretion (GSIS). Multiple other Slc30a isoforms are expressed at low levels in pancreatic islets. We hypothesized that functional compensation by the Slc30a7 isoform, which encodes ZnT7, limits the impact of Slc30a8 deletion on islet function. We therefore analyzed the effect of Slc30a7 deletion alone or in combination with Slc30a8 on in vivo glucose metabolism and GSIS in isolated islets. Deletion of Slc30a7 alone had complex effects in vivo, impairing glucose tolerance and reducing the glucose-stimulated increase in plasma insulin levels, hepatic glycogen levels, and pancreatic insulin content. Slc30a7 deletion also affected islet morphology and increased the ratio of islet α- to β-cells. However, deletion of Slc30a7 alone had no effect on GSIS in isolated islets, whereas combined deletion of Slc30a7 and Slc30a8 abolished GSIS. These data demonstrate that the function of ZnT8 in islets can be unmasked by removal of ZnT7 and imply that ZnT8 may affect T2D susceptibility through actions in other tissues where it is expressed at low levels rather than through effects on pancreatic islet function.
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Affiliation(s)
- Kristen E Syring
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
| | - Kayla A Boortz
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
| | - James K Oeser
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
| | - Alessandro Ustione
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
| | - Kenneth A Platt
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
| | - Melanie K Shadoan
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
| | - Owen P McGuinness
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
| | - David W Piston
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
| | - David R Powell
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
| | - Richard M O'Brien
- Department of Molecular Physiology and Biophysics (K.E.S., K.A.B., J.K.O., O.P.M., R.M.O.), Vanderbilt University Medical School, Nashville, Tennessee 37232; Department of Cell Biology and Physiology (A.U., D.W.P.), Washington University School of Medicine, St. Louis, Missouri 63110; and Lexicon Pharmaceuticals Incorporated (K.A.P., M.K.S., D.R.P.), The Woodlands, Texas 77381
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Lee J, Harris AN, Holley CL, Mahadevan J, Pyles KD, Lavagnino Z, Scherrer DE, Fujiwara H, Sidhu R, Zhang J, Huang SCC, Piston DW, Remedi MS, Urano F, Ory DS, Schaffer JE. Rpl13a small nucleolar RNAs regulate systemic glucose metabolism. J Clin Invest 2016; 126:4616-4625. [PMID: 27820699 DOI: 10.1172/jci88069] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 09/29/2016] [Indexed: 12/22/2022] Open
Abstract
Small nucleolar RNAs (snoRNAs) are non-coding RNAs that form ribonucleoproteins to guide covalent modifications of ribosomal and small nuclear RNAs in the nucleus. Recent studies have also uncovered additional non-canonical roles for snoRNAs. However, the physiological contributions of these small RNAs are largely unknown. Here, we selectively deleted four snoRNAs encoded within the introns of the ribosomal protein L13a (Rpl13a) locus in a mouse model. Loss of Rpl13a snoRNAs altered mitochondrial metabolism and lowered reactive oxygen species tone, leading to increased glucose-stimulated insulin secretion from pancreatic islets and enhanced systemic glucose tolerance. Islets from mice lacking Rpl13a snoRNAs demonstrated blunted oxidative stress responses. Furthermore, these mice were protected against diabetogenic stimuli that cause oxidative stress damage to islets. Our study illuminates a previously unrecognized role for snoRNAs in metabolic regulation.
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Bechard ME, Bankaitis ED, Hipkens SB, Ustione A, Piston DW, Yang YP, Magnuson MA, Wright CVE. Precommitment low-level Neurog3 expression defines a long-lived mitotic endocrine-biased progenitor pool that drives production of endocrine-committed cells. Genes Dev 2016; 30:1852-65. [PMID: 27585590 PMCID: PMC5024683 DOI: 10.1101/gad.284729.116] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 08/03/2016] [Indexed: 12/22/2022]
Abstract
Bechard et al. show that a cell population defined as Neurog3 transcriptionally active and Sox9+ and often containing nonimmunodetectable Neurog3 protein has a relatively high mitotic index and prolonged epithelial residency. They propose that this endocrine-biased mitotic progenitor state is functionally separated from a pro-ductal pool and endows them with long-term capacity to make endocrine fate-directed progeny. The current model for endocrine cell specification in the pancreas invokes high-level production of the transcription factor Neurogenin 3 (Neurog3) in Sox9+ bipotent epithelial cells as the trigger for endocrine commitment, cell cycle exit, and rapid delamination toward proto-islet clusters. This model posits a transient Neurog3 expression state and short epithelial residence period. We show, however, that a Neurog3TA.LO cell population, defined as Neurog3 transcriptionally active and Sox9+ and often containing nonimmunodetectable Neurog3 protein, has a relatively high mitotic index and prolonged epithelial residency. We propose that this endocrine-biased mitotic progenitor state is functionally separated from a pro-ductal pool and endows them with long-term capacity to make endocrine fate-directed progeny. A novel BAC transgenic Neurog3 reporter detected two types of mitotic behavior in Sox9+Neurog3TA.LO progenitors, associated with progenitor pool maintenance or derivation of endocrine-committed Neurog3HI cells, respectively. Moreover, limiting Neurog3 expression dramatically increased the proportional representation of Sox9+Neurog3TA.LO progenitors, with a doubling of its mitotic index relative to normal Neurog3 expression, suggesting that low Neurog3 expression is a defining feature of this cycling endocrine-biased state. We propose that Sox9+Neurog3TA.LO endocrine-biased progenitors feed production of Neurog3HI endocrine-committed cells during pancreas organogenesis.
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Affiliation(s)
- Matthew E Bechard
- Vanderbilt University Program in Developmental Biology, Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Eric D Bankaitis
- Vanderbilt University Program in Developmental Biology, Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Susan B Hipkens
- Vanderbilt University Program in Developmental Biology, Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Alessandro Ustione
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - David W Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Yu-Ping Yang
- Vanderbilt University Program in Developmental Biology, Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Mark A Magnuson
- Vanderbilt University Program in Developmental Biology, Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Christopher V E Wright
- Vanderbilt University Program in Developmental Biology, Department of Cell and Developmental Biology, Vanderbilt Center for Stem Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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Liv N, van Oosten Slingeland DSB, Baudoin JP, Kruit P, Piston DW, Hoogenboom JP. Electron Microscopy of Living Cells During in Situ Fluorescence Microscopy. ACS Nano 2016; 10:265-73. [PMID: 26580231 PMCID: PMC4729641 DOI: 10.1021/acsnano.5b03970] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We present an approach toward dynamic nanoimaging: live fluorescence of cells encapsulated in a bionanoreactor is complemented with in situ scanning electron microscopy (SEM) on an integrated microscope. This allows us to take SEM snapshots on-demand, that is, at a specific location in time, at a desired region of interest, guided by the dynamic fluorescence imaging. We show that this approach enables direct visualization, with EM resolution, of the distribution of bioconjugated quantum dots on cellular extensions during uptake and internalization.
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Affiliation(s)
- Nalan Liv
- Department of Imaging Physics, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | | | - Jean-Pierre Baudoin
- Department of Molecular Physiology and Biophysics, Vanderbilt University, 747 Light Hall, Nashville, Tennessee 37232-0615, United States
| | - Pieter Kruit
- Department of Imaging Physics, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - David W. Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University, 747 Light Hall, Nashville, Tennessee 37232-0615, United States
| | - Jacob P. Hoogenboom
- Department of Imaging Physics, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
- Corresponding Author:
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Abstract
The loss of inhibition of glucagon secretion exacerbates hyperglycemia in type 1 and 2 diabetes. However, the molecular mechanisms that regulate glucagon secretion in unaffected and diabetic states remain relatively unexplained. We present evidence supporting a new model of juxtacrine-mediated regulation of glucagon secretion where neighboring islet cells negatively regulate glucagon secretion through tonic stimulation of α-cell EphA receptors. Primarily through EphA4 receptors, this stimulation correlates with maintenance of a dense F-actin network. In islets, additional stimulation and inhibition of endogenous EphA forward signaling result in inhibition and enhancement, respectively, of glucagon secretion, accompanied by an increase and decrease, respectively, in α-cell F-actin density. Sorted α-cells lack endogenous stimulation of EphA forward signaling from neighboring cells, resulting in enhanced basal glucagon secretion as compared with islets and the elimination of glucose inhibition of glucagon secretion. Restoration of EphA forward signaling in sorted α-cells recapitulates both normal basal glucagon secretion and glucose inhibition of glucagon secretion. Additionally, α-cell-specific EphA4(-/-) mice exhibit abnormal glucagon dynamics, and EphA4(-/-) α-cells contain less dense F-actin networks than EphA4(+/+) α-cells. This juxtacrine-mediated model provides insight into the functional and dysfunctional regulation of glucagon secretion and opens up new therapeutic strategies for the clinical management of diabetes.
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Affiliation(s)
- Troy Hutchens
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - David W Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO
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Gunawardana SC, Piston DW. Insulin-independent reversal of type 1 diabetes in nonobese diabetic mice with brown adipose tissue transplant. Am J Physiol Endocrinol Metab 2015; 308:E1043-55. [PMID: 25898954 PMCID: PMC4469812 DOI: 10.1152/ajpendo.00570.2014] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 04/11/2015] [Indexed: 02/07/2023]
Abstract
Traditional therapies for type 1 diabetes (T1D) involve insulin replacement or islet/pancreas transplantation and have numerous limitations. Our previous work demonstrated the ability of embryonic brown adipose tissue (BAT) transplants to establish normoglycemia without insulin in chemically induced models of insulin-deficient diabetes. The current study sought to extend the technique to an autoimmune-mediated T1D model and document the underlying mechanisms. In nonobese diabetic (NOD) mice, BAT transplants result in complete reversal of T1D associated with rapid and long-lasting euglycemia. In addition, BAT transplants placed prior to the onset of diabetes on NOD mice can prevent or significantly delay the onset of diabetes. As with streptozotocin (STZ)-diabetic models, euglycemia is independent of insulin and strongly correlates with decrease of inflammation and increase of adipokines. Plasma insulin-like growth factor-I (IGF-I) is the first hormone to increase following BAT transplants. Adipose tissue of transplant recipients consistently express IGF-I compared with little or no expression in controls, and plasma IGF-I levels show a direct negative correlation with glucose, glucagon, and inflammatory cytokines. Adipogenic and anti-inflammatory properties of IGF-I may stimulate regeneration of new healthy white adipose tissue, which in turn secretes hypoglycemic adipokines that substitute for insulin. IGF-I can also directly decrease blood glucose through activating insulin receptor. These data demonstrate the potential for insulin-independent reversal of autoimmune-induced T1D with BAT transplants and implicate IGF-I as a likely mediator in the resulting equilibrium.
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Affiliation(s)
- Subhadra C Gunawardana
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - David W Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
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Mendonsa AM, VanSaun MN, Ustione A, Piston DW, Fingleton BM, Gorden DL. Host and tumor derived MMP13 regulate extravasation and establishment of colorectal metastases in the liver. Mol Cancer 2015; 14:49. [PMID: 25880591 PMCID: PMC4351934 DOI: 10.1186/s12943-014-0282-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 12/22/2014] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Non alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases in the United States and worldwide. Our studies have previously shown an increase in metastatic burden in steatotic vs. normal livers using a mouse model of diet induced steatosis. In the present study we aim to identify and evaluate the molecular factors responsible for this increase in tumor burden. METHODS We assessed changes in expression of a panel of matrix metalloproteinases (MMPs) using qRT-PCR between normal and steatotic livers and validated them with western blot analysis of protein levels. To evaluate the role of MMP13 on tumor development, we utilized a splenic injection model of liver metastasis in Wildtype and Mmp13 deficient mice, using either parental or stable Mmp13 knockdown cell lines. Further, to evaluate changes in the ability of tumor cells to extravasate we utilized whole organ confocal microscopy to identify individual tumor cells relative to the vasculature. MTT, migration and invasion assays were performed to evaluate the role of tumor derived MMP13 on hallmarks of cancer in vitro. RESULTS We found that MMP13 was significantly upregulated in the steatotic liver both in mice as well as human patients with NAFLD. We showed a decrease in metastatic tumor burden in Mmp13-/- mice compared to wildtype mice, explained in part by a reduction in the number of tumor cells extravasating from the hepatic vasculature in the Mmp13-/- mice compared to wildtype mice. Additionally, loss of tumor derived MMP13 through stable knockdown in tumor cell lines lead to decreased migratory and invasive properties in vitro and metastatic burden in vivo. CONCLUSIONS This study demonstrates that stromal as well as tumor derived MMP13 contribute to tumor cell extravasation and establishment of metastases in the liver microenvironment.
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Affiliation(s)
- Alisha M Mendonsa
- Department of Cancer Biology, Vanderbilt University, 2220 Pierce Ave S, Nashville, TN, 37232, USA.
| | - Michael N VanSaun
- Department of Cancer Biology, Vanderbilt University, 2220 Pierce Ave S, Nashville, TN, 37232, USA. .,Department of Surgery, Vanderbilt University, 801 Oxford House, 1313 21st Ave. S, Nashville, TN, 37212, USA.
| | - Alessandro Ustione
- Department of Molecular Physiology and Biophysics, Vanderbilt University, 702 Light Hall 21st Avenue South, Nashville, TN, 37232, USA.
| | - David W Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University, 702 Light Hall 21st Avenue South, Nashville, TN, 37232, USA.
| | - Barbara M Fingleton
- Department of Cancer Biology, Vanderbilt University, 2220 Pierce Ave S, Nashville, TN, 37232, USA.
| | - David Lee Gorden
- Department of Cancer Biology, Vanderbilt University, 2220 Pierce Ave S, Nashville, TN, 37232, USA. .,Department of Surgery, Vanderbilt University, 801 Oxford House, 1313 21st Ave. S, Nashville, TN, 37212, USA.
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Abstract
The dysregulation of glucose-inhibited glucagon secretion from the pancreatic islet α-cell is a critical component of diabetes pathology and metabolic disease. We show a previously uncharacterized [Ca(2+)]i-independent mechanism of glucagon suppression in human and murine pancreatic islets whereby cAMP and PKA signaling are decreased. This decrease is driven by the combination of somatostatin, which inhibits adenylyl cyclase production of cAMP via the Gαi subunit of the SSTR2, and insulin, which acts via its receptor to activate phosphodiesterase 3B and degrade cytosolic cAMP. Our data indicate that both somatostatin and insulin signaling are required to suppress cAMP/PKA and glucagon secretion from both human and murine α-cells, and the combination of these two signaling mechanisms is sufficient to reduce glucagon secretion from isolated α-cells as well as islets. Thus, we conclude that somatostatin and insulin together are critical paracrine mediators of glucose-inhibited glucagon secretion and function by lowering cAMP/PKA signaling with increasing glucose.
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Affiliation(s)
- Amicia D Elliott
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Alessandro Ustione
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
| | - David W Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee
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Ustione A, Piston DW. Simultaneous Measurements of Intracellular [Ca2+]i and [cAMP]i in Intact Islets to Study the Mechanism Underlying Dopaminergic Inhibition of Insulin Secretion. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.2390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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43
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Lavagnino Z, Piston DW. Functional Imaging of Intact Pancreatic Islets by Inverted Selective Plane Illumination Microscopy. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.1973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Benninger RKP, Hutchens T, Head WS, McCaughey MJ, Zhang M, Le Marchand SJ, Satin LS, Piston DW. Intrinsic islet heterogeneity and gap junction coupling determine spatiotemporal Ca²⁺ wave dynamics. Biophys J 2014; 107:2723-33. [PMID: 25468351 DOI: 10.1016/j.bpj.2014.10.048] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 09/09/2014] [Accepted: 10/08/2014] [Indexed: 10/24/2022] Open
Abstract
Insulin is released from the islets of Langerhans in discrete pulses that are linked to synchronized oscillations of intracellular free calcium ([Ca(2+)]i). Associated with each synchronized oscillation is a propagating calcium wave mediated by Connexin36 (Cx36) gap junctions. A computational islet model predicted that waves emerge due to heterogeneity in β-cell function throughout the islet. To test this, we applied defined patterns of glucose stimulation across the islet using a microfluidic device and measured how these perturbations affect calcium wave propagation. We further investigated how gap junction coupling regulates spatiotemporal [Ca(2+)]i dynamics in the face of heterogeneous glucose stimulation. Calcium waves were found to originate in regions of the islet having elevated excitability, and this heterogeneity is an intrinsic property of islet β-cells. The extent of [Ca(2+)]i elevation across the islet in the presence of heterogeneity is gap-junction dependent, which reveals a glucose dependence of gap junction coupling. To better describe these observations, we had to modify the computational islet model to consider the electrochemical gradient between neighboring β-cells. These results reveal how the spatiotemporal [Ca(2+)]i dynamics of the islet depend on β-cell heterogeneity and cell-cell coupling, and are important for understanding the regulation of coordinated insulin release across the islet.
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Affiliation(s)
- Richard K P Benninger
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee; Department of Bioengineering, University of Colorado, Aurora, Colorado; Barbara Davis Center, University of Colorado, Aurora, Colorado.
| | - Troy Hutchens
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee
| | - W Steven Head
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Michael J McCaughey
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Min Zhang
- Department of Pharmacology, Virginia Commonwealth University, Richmond, Virginia
| | - Sylvain J Le Marchand
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee
| | - Leslie S Satin
- Department of Pharmacology, Virginia Commonwealth University, Richmond, Virginia; Department of Pharmacology, University of Michigan, Ann Arbor, Michigan; Brehm Diabetes Center, University of Michigan, Ann Arbor, Michigan
| | - David W Piston
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee.
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DeGuire SM, Earl DC, Du Y, Crews BA, Jacobs AT, Ustione A, Daniel C, Chong KM, Marnett LJ, Piston DW, Bachmann BO, Sulikowski GA. Fluorescent Probes of the Apoptolidins and their Utility in Cellular Localization Studies. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201408906] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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DeGuire SM, Earl DC, Du Y, Crews BA, Jacobs AT, Ustione A, Daniel C, Chong KM, Marnett LJ, Piston DW, Bachmann BO, Sulikowski GA. Fluorescent probes of the apoptolidins and their utility in cellular localization studies. Angew Chem Int Ed Engl 2014; 54:961-4. [PMID: 25430909 DOI: 10.1002/anie.201408906] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 10/27/2014] [Indexed: 11/05/2022]
Abstract
Apoptolidin A has been described among the top 0.1% most-cell-selective cytotoxic agents to be evaluated in the NCI 60 cell line panel. The molecular structure of apoptolidin A consists of a 20-membered macrolide with mono- and disaccharide moieties. In contrast to apoptolidin A, the aglycone (apoptolidinone) shows no cytotoxicity (>10 μM) when evaluated against several tumor cell lines. Apoptolidin H, the C27 deglycosylated analogue of apoptolidin A, displayed sub-micromolar activity against H292 lung carcinoma cells. Selective esterification of apoptolidins A and H with 5-azidopentanoic acid afforded azido-functionalized derivatives of potency equal to that of the parent macrolide. They also underwent strain-promoted alkyne-azido cycloaddition reactions to provide access to fluorescent and biotin-functionalized probes. Microscopy studies demonstrate apoptolidins A and H localize in the mitochondria of H292 human lung carcinoma cells.
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Affiliation(s)
- Sean M DeGuire
- Department of Chemistry, Vanderbilt University, Vanderbilt Institute of Chemical Biology, Nashville, TN 37232 (USA)
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Barnes TM, Otero YF, Elliott AD, Locke AD, Malabanan CM, Coldren AG, Brissova M, Piston DW, McGuinness OP. Interleukin-6 amplifies glucagon secretion: coordinated control via the brain and pancreas. Am J Physiol Endocrinol Metab 2014; 307:E896-905. [PMID: 25205821 PMCID: PMC4233256 DOI: 10.1152/ajpendo.00343.2014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Inappropriate glucagon secretion contributes to hyperglycemia in inflammatory disease. Previous work implicates the proinflammatory cytokine interleukin-6 (IL-6) in glucagon secretion. IL-6-KO mice have a blunted glucagon response to lipopolysaccharide (LPS) that is restored by intravenous replacement of IL-6. Given that IL-6 has previously been demonstrated to have a transcriptional (i.e., slow) effect on glucagon secretion from islets, we hypothesized that the rapid increase in glucagon following LPS occurred by a faster mechanism, such as by action within the brain. Using chronically catheterized conscious mice, we have demonstrated that central IL-6 stimulates glucagon secretion uniquely in the presence of an accompanying stressor (hypoglycemia or LPS). Contrary to our hypothesis, however, we found that IL-6 amplifies glucagon secretion in two ways; IL-6 not only stimulates glucagon secretion via the brain but also by direct action on islets. Interestingly, IL-6 augments glucagon secretion from both sites only in the presence of an accompanying stressor (such as epinephrine). Given that both adrenergic tone and plasma IL-6 are elevated in multiple inflammatory diseases, the interactions of the IL-6 and catecholaminergic signaling pathways in regulating GCG secretion may contribute to our present understanding of these diseases.
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Affiliation(s)
- Tammy M Barnes
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Yolanda F Otero
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Amicia D Elliott
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Alicia D Locke
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Carlo M Malabanan
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Anastasia G Coldren
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Marcela Brissova
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - David W Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Owen P McGuinness
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
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Benninger RKP, Piston DW. Cellular communication and heterogeneity in pancreatic islet insulin secretion dynamics. Trends Endocrinol Metab 2014; 25:399-406. [PMID: 24679927 PMCID: PMC4112137 DOI: 10.1016/j.tem.2014.02.005] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 02/21/2014] [Accepted: 02/25/2014] [Indexed: 11/20/2022]
Abstract
Coordinated pulses of electrical activity and insulin secretion are a hallmark of the islet of Langerhans. These coordinated behaviors are lost when β cells are dissociated, which also leads to increased insulin secretion at low glucose levels. Islets without gap junctions exhibit asynchronous electrical activity similar to dispersed cells, but their secretion at low glucose levels is still clamped off, putatively by a juxtacrine mechanism. Mice lacking β cell gap junctions have near-normal average insulin levels, but are glucose intolerant due to reduced first-phase and pulsatile insulin secretion, illustrating the importance of temporal dynamics. Here, we review the quantitative data on islet synchronization and the current mathematical models that have been developed to explain these behaviors and generate greater understanding of the underlying mechanisms.
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Affiliation(s)
- Richard K P Benninger
- Department of Bioengineering and Barbara Davis Center, University of Colorado Anschutz Medical campus, Aurora, CO, USA.
| | - David W Piston
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, TN, USA.
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Hang Y, Yamamoto T, Benninger RKP, Brissova M, Guo M, Bush W, Piston DW, Powers AC, Magnuson M, Thurmond DC, Stein R. The MafA transcription factor becomes essential to islet β-cells soon after birth. Diabetes 2014; 63:1994-2005. [PMID: 24520122 PMCID: PMC4030115 DOI: 10.2337/db13-1001] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The large Maf transcription factors, MafA and MafB, are expressed with distinct spatial-temporal patterns in rodent islet cells. Analysis of Mafa(-/-) and pancreas-specific Mafa(∆panc) deletion mutant mice demonstrated a primary role for MafA in adult β-cell activity, different from the embryonic importance of MafB. Our interests here were to precisely define when MafA became functionally significant to β-cells, to determine how this was affected by the brief period of postnatal MafB production, and to identify genes regulated by MafA during this period. We found that islet cell organization, β-cell mass, and β-cell function were influenced by 3 weeks of age in Mafa(Δpanc) mice and compromised earlier in Mafa(Δpanc);Mafb(+/-) mice. A combination of genome-wide microarray profiling, electron microscopy, and metabolic assays were used to reveal mechanisms of MafA control. For example, β-cell replication was produced by actions on cyclin D2 regulation, while effects on granule docking affected first-phase insulin secretion. Moreover, notable differences in the genes regulated by embryonic MafB and postnatal MafA gene expression were found. These results not only clearly define why MafA is an essential transcriptional regulator of islet β-cells, but also why cell maturation involves coordinated actions with MafB.
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Affiliation(s)
- Yan Hang
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Tsunehiko Yamamoto
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Richard K P Benninger
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Marcela Brissova
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
| | - Min Guo
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Will Bush
- Department of Biomedical Informatics, Center for Human Genetics Research, Vanderbilt University School of Medicine, Nashville, TN
| | - David W Piston
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Alvin C Powers
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TNDivision of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TNVeterans Affairs Tennessee Valley Healthcare System, Nashville, TN
| | - Mark Magnuson
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Debbie C Thurmond
- Department of Pediatrics, Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN
| | - Roland Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
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