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Kolic J, Sun WG, Cen HH, Ewald JD, Rogalski JC, Sasaki S, Sun H, Rajesh V, Xia YH, Moravcova R, Skovsø S, Spigelman AF, Manning Fox JE, Lyon J, Beet L, Xia J, Lynn FC, Gloyn AL, Foster LJ, MacDonald PE, Johnson JD. Proteomic predictors of individualized nutrient-specific insulin secretion in health and disease. Cell Metab 2024; 36:1619-1633.e5. [PMID: 38959864 DOI: 10.1016/j.cmet.2024.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 02/26/2024] [Accepted: 06/03/2024] [Indexed: 07/05/2024]
Abstract
Population-level variation and mechanisms behind insulin secretion in response to carbohydrate, protein, and fat remain uncharacterized. We defined prototypical insulin secretion responses to three macronutrients in islets from 140 cadaveric donors, including those with type 2 diabetes. The majority of donors' islets exhibited the highest insulin response to glucose, moderate response to amino acid, and minimal response to fatty acid. However, 9% of donors' islets had amino acid responses, and 8% had fatty acid responses that were larger than their glucose-stimulated insulin responses. We leveraged this heterogeneity and used multi-omics to identify molecular correlates of nutrient responsiveness, as well as proteins and mRNAs altered in type 2 diabetes. We also examined nutrient-stimulated insulin release from stem cell-derived islets and observed responsiveness to fat but not carbohydrate or protein-potentially a hallmark of immaturity. Understanding the diversity of insulin responses to carbohydrate, protein, and fat lays the groundwork for personalized nutrition.
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Affiliation(s)
- Jelena Kolic
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada.
| | - WenQing Grace Sun
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Haoning Howard Cen
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Jessica D Ewald
- Institute of Parasitology, McGill University, Montreal, QC, Canada
| | - Jason C Rogalski
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Shugo Sasaki
- Diabetes Research Group, BC Children's Hospital Research Institute, Vancouver, BC, Canada; Department of Surgery, School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
| | - Han Sun
- Department of Pediatrics, Division of Endocrinology, Stanford School of Medicine, Stanford, CA, USA
| | - Varsha Rajesh
- Department of Pediatrics, Division of Endocrinology, Stanford School of Medicine, Stanford, CA, USA
| | - Yi Han Xia
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Renata Moravcova
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Søs Skovsø
- Valkyrie Life Sciences, Vancouver, BC, Canada
| | - Aliya F Spigelman
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Jocelyn E Manning Fox
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - James Lyon
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Leanne Beet
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Jianguo Xia
- Institute of Parasitology, McGill University, Montreal, QC, Canada
| | - Francis C Lynn
- Diabetes Research Group, BC Children's Hospital Research Institute, Vancouver, BC, Canada; Department of Surgery, School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
| | - Anna L Gloyn
- Department of Pediatrics, Division of Endocrinology, Stanford School of Medicine, Stanford, CA, USA; Stanford Diabetes Research Center, Stanford School of Medicine, Stanford, CA, USA; Wellcome Center for Human Genetics, University of Oxford, Oxford, UK
| | - Leonard J Foster
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - James D Johnson
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada; Vancouver Coastal Health Research Institute, Vancouver, BC, Canada.
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Kolic J, Sun WG, Cen HH, Ewald J, Rogalski JC, Sasaki S, Sun H, Rajesh V, Xia YH, Moravcova R, Skovsø S, Spigelman AF, Manning Fox JE, Lyon J, Beet L, Xia J, Lynn FC, Gloyn AL, Foster LJ, MacDonald PE, Johnson JD. Proteomic predictors of individualized nutrient-specific insulin secretion in health and disease. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2023.05.24.23290298. [PMID: 38496562 PMCID: PMC10942505 DOI: 10.1101/2023.05.24.23290298] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Population level variation and molecular mechanisms behind insulin secretion in response to carbohydrate, protein, and fat remain uncharacterized despite ramifications for personalized nutrition. Here, we define prototypical insulin secretion dynamics in response to the three macronutrients in islets from 140 cadaveric donors, including those diagnosed with type 2 diabetes. While islets from the majority of donors exhibited the expected relative response magnitudes, with glucose being highest, amino acid moderate, and fatty acid small, 9% of islets stimulated with amino acid and 8% of islets stimulated with fatty acids had larger responses compared with high glucose. We leveraged this insulin response heterogeneity and used transcriptomics and proteomics to identify molecular correlates of specific nutrient responsiveness, as well as those proteins and mRNAs altered in type 2 diabetes. We also examine nutrient-responsiveness in stem cell-derived islet clusters and observe that they have dysregulated fuel sensitivity, which is a hallmark of functionally immature cells. Our study now represents the first comparison of dynamic responses to nutrients and multi-omics analysis in human insulin secreting cells. Responses of different people's islets to carbohydrate, protein, and fat lay the groundwork for personalized nutrition. ONE-SENTENCE SUMMARY Deep phenotyping and multi-omics reveal individualized nutrient-specific insulin secretion propensity.
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Loh YP, Xiao L, Park JJ. Trafficking of hormones and trophic factors to secretory and extracellular vesicles: a historical perspective and new hypothesis. EXTRACELLULAR VESICLES AND CIRCULATING NUCLEIC ACIDS 2023; 4:568-587. [PMID: 38435713 PMCID: PMC10906782 DOI: 10.20517/evcna.2023.34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 03/05/2024]
Abstract
It is well known that peptide hormones and neurotrophic factors are intercellular messengers that are packaged into secretory vesicles in endocrine cells and neurons and released by exocytosis upon the stimulation of the cells in a calcium-dependent manner. These secreted molecules bind to membrane receptors, which then activate signal transduction pathways to mediate various endocrine/trophic functions. Recently, there is evidence that these molecules are also in extracellular vesicles, including small extracellular vesicles (sEVs), which appear to be taken up by recipient cells. This finding raised the hypothesis that they may have functions differentiated from their classical secretory hormone/neurotrophic factor actions. In this article, the historical perspective and updated mechanisms for the sorting and packaging of hormones and neurotrophic factors into secretory vesicles and their transport in these organelles for release at the plasma membrane are reviewed. In contrast, little is known about the packaging of hormones and neurotrophic factors into extracellular vesicles. One proposal is that these molecules could be sorted at the trans-Golgi network, which then buds to form Golgi-derived vesicles that can fuse to endosomes and subsequently form intraluminal vesicles. They are then taken up by multivesicular bodies to form extracellular vesicles, which are subsequently released. Other possible mechanisms for packaging RSP proteins into sEVs are discussed. We highlight some studies in the literature that suggest the dual vesicular pathways for the release of hormones and neurotrophic factors from the cell may have some physiological significance in intercellular communication.
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Affiliation(s)
- Y. Peng Loh
- Section on Cellular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Lan Xiao
- Section on Cellular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Joshua J. Park
- Scientific Review Branch, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA
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Khalid E, Chang JP. Small GTPase control of pituitary hormone secretion: Evidence from studies in the goldfish (Carassius auratus) neuroendocrine model. Gen Comp Endocrinol 2023; 339:114287. [PMID: 37060929 DOI: 10.1016/j.ygcen.2023.114287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 03/27/2023] [Accepted: 04/10/2023] [Indexed: 04/17/2023]
Abstract
The secretion of vertebrate pituitary hormones is regulated by multiple hypothalamic factors, which, while generally activating unique receptor systems, ultimately propagate signals through interacting intracellular regulatory elements to modulate hormone exocytosis. One important family of intracellular regulators is the monomeric small GTPases, a subset of which (Arf1/6, Rac, RhoA, and Ras) is highly conserved across vertebrates and regulates secretory vesicle exocytosis in many cell types. In this study, we investigated the roles of these small GTPases in basal and agonist-dependent hormone release from dispersed goldfish (Carassius auratus) pituitary cells in perifusion experiments. Inhibition of these small GTPases elevated basal LH and GH secretion, except for Ras inhibition which only increased basal LH release. However, variable responses were observed with regard to LH and GH responses to the two goldfish native gonadotropin-releasing hormones (GnRH2 and GnRH3). GnRH-dependent LH release, but not GH secretion, was mediated by Arf1/6 GTPases. In contrast, inhibition of Rac and RhoA GTPases selectively enhanced GnRH3- and GnRH2-dependent GH release, respectively, while Ras inhibition only enhanced GnRH3-evoked LH secretion. Together, our results reveal novel divergent cell-type- and ligand-specific roles for small GTPases in the control of goldfish pituitary hormone exocytosis in unstimulated and GnRH-evoked release.
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Affiliation(s)
- Enezi Khalid
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada, T6G 2E9
| | - John P Chang
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada, T6G 2E9.
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PI3K and AKT at the Interface of Signaling and Metabolism. Curr Top Microbiol Immunol 2022; 436:311-336. [DOI: 10.1007/978-3-031-06566-8_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Jia JD, Jiang WG, Luo X, Li RR, Zhao YC, Tian G, Li YN. Vascular endothelial growth factor B inhibits insulin secretion in MIN6 cells and reduces Ca 2+ and cyclic adenosine monophosphate levels through PI3K/AKT pathway. World J Diabetes 2021; 12:480-498. [PMID: 33889292 PMCID: PMC8040075 DOI: 10.4239/wjd.v12.i4.480] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 01/25/2021] [Accepted: 03/08/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Type 2 diabetes (T2D) is characterized by insufficient insulin secretion caused by defective pancreatic β-cell function or insulin resistance, resulting in an increase in blood glucose. However, the mechanism involved in this lack of insulin secretion is unclear. The level of vascular endothelial growth factor B (VEGF-B) is significantly increased in T2D patients. The inactivation of VEGF-B could restore insulin sensitivity in db/db mice by reducing fatty acid accumulation. It is speculated that VEGF-B is related to pancreatic β-cell dysfunction and is an important factor affecting β-cell secretion of insulin. As an in vitro model of normal pancreatic β-cells, the MIN6 cell line can be used to analyze the mechanism of insulin secretion and related biological effects.
AIM To study the role of VEGF-B in the insulin secretion signaling pathway in MIN6 cells and explore the effect of VEGF-B on blood glucose regulation.
METHODS The MIN6 mouse pancreatic islet β-cell line was used as the model system. By administering exogenous VEGF-B protein or knocking down VEGF-B expression in MIN6 cells, we examined the effects of VEGF-B on insulin secretion, Ca2+ and cyclic adenosine monophosphate (cAMP) levels, and the insulin secretion signaling pathway.
RESULTS Exogenous VEGF-B inhibited the secretion of insulin and simultaneously reduced the levels of Ca2+ and cAMP in MIN6 cells. Exogenous VEGF-B also reduced the expression of phospholipase C gamma 1 (PLCγ1), phosphatidylinositol 3-kinase (PI3K), serine/threonine kinase (AKT), and other proteins in the insulin secretion pathway. Upon knockdown of VEGF-B, MIN6 cells exhibited increased insulin secretion and Ca2+ and cAMP levels and upregulated expression of PLCγ1, PI3K, AKT, and other proteins.
CONCLUSION VEGF-B can regulate insulin secretion by modulating the levels of Ca2+ and cAMP. VEGF-B involvement in insulin secretion is related to the expression of PLCγ1, PI3K, AKT, and other signaling proteins. These results provide theoretical support and an experimental basis for the study of VEGF-B in the pathogenesis of T2D.
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Affiliation(s)
- Jing-Dan Jia
- Department of Pathophysiology, School of Basic Medicine, Binzhou Medical University, Yantai 264003, Shandong Province, China
| | - Wen-Guo Jiang
- Department of Pharmacy, Binzhou Medical University, Yantai 264003, Shandong Province, China
| | - Xu Luo
- Department of Pathophysiology, School of Basic Medicine, Binzhou Medical University, Yantai 264003, Shandong Province, China
| | - Rong-Rong Li
- Department of Pathophysiology, School of Basic Medicine, Binzhou Medical University, Yantai 264003, Shandong Province, China
| | - Yu-Chi Zhao
- Department of Surgery, Yantaishan Hospital, Yantai 264001, Shandong Province, China
| | - Geng Tian
- Department of Pharmacy, Binzhou Medical University, Yantai 264003, Shandong Province, China
| | - Ya-Na Li
- Department of Pathophysiology, School of Basic Medicine, Binzhou Medical University, Yantai 264003, Shandong Province, China
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Lee YN, Yi HJ, Goh H, Park JY, Ferber S, Shim IK, Kim SC. Spheroid Fabrication Using Concave Microwells Enhances the Differentiation Efficacy and Function of Insulin-Producing Cells via Cytoskeletal Changes. Cells 2020; 9:cells9122551. [PMID: 33261076 PMCID: PMC7768489 DOI: 10.3390/cells9122551] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/11/2020] [Accepted: 11/24/2020] [Indexed: 01/21/2023] Open
Abstract
Pancreatic islet transplantation is the fundamental treatment for insulin-dependent diabetes; however, donor shortage is a major hurdle in its use as a standard treatment. Accordingly, differentiated insulin-producing cells (DIPCs) are being developed as a new islet source. Differentiation efficiency could be enhanced if the spheroid structure of the natural islets could be recapitulated. Here, we fabricated DIPC spheroids using concave microwells, which enabled large-scale production of spheroids of the desired size. We prepared DIPCs from human liver cells by trans-differentiation using transcription factor gene transduction. Islet-related gene expression and insulin secretion levels were higher in spheroids compared to those in single-cell DIPCs, whereas actin–myosin interactions significantly decreased. We verified actin–myosin-dependent insulin expression in single-cell DIPCs by using actin–myosin interaction inhibitors. Upon transplanting cells into the kidney capsule of diabetic mouse, blood glucose levels decreased to 200 mg/dL in spheroid-transplanted mice but not in single cell-transplanted mice. Spheroid-transplanted mice showed high engraftment efficiency in in vivo fluorescence imaging. These results demonstrated that spheroids fabricated using concave microwells enhanced the engraftment and functions of DIPCs via actin–myosin-mediated cytoskeletal changes. Our strategy potentially extends the clinical application of DIPCs for improved differentiation, glycemic control, and transplantation efficiency of islets.
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Affiliation(s)
- Yu Na Lee
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Asan Medical Center, Department of Medical Science, Asan Medical Institute of Convergence Science and Technology (AMIST), University of Ulsan College of Medicine, Seoul 05505, Korea
| | - Hye Jin Yi
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Asan Medical Center, Department of Medical Science, Asan Medical Institute of Convergence Science and Technology (AMIST), University of Ulsan College of Medicine, Seoul 05505, Korea
| | - Hanse Goh
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
| | - Ji Yoon Park
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Department of Chemistry, Wesleyan University, Middletown, CT 06457, USA
| | - Sarah Ferber
- Regenerative Medicine, Stem Cell and Tissue Engineering Center, Sheba Medical Center, Tel-Hashomer 52621, Israel;
- Dia-Cure, Acad. Nicolae Cajal Institute of Medical Scientific Research, Titu Maiorescu University, 022328 Bucharest, Romania
- Orgenesis Ltd., Ness-Ziona 7403631, Israel
- Department of Human Genetics, Sackler School of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - In Kyong Shim
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Asan Medical Center, Department of Medical Science, Asan Medical Institute of Convergence Science and Technology (AMIST), University of Ulsan College of Medicine, Seoul 05505, Korea
- Correspondence: or (I.K.S.); (S.C.K.); Tel.: +82-2-3010-4173 (I.K.S.); +82-2-3010-3936 (S.C.K.)
| | - Song Cheol Kim
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Asan Medical Center, Department of Medical Science, Asan Medical Institute of Convergence Science and Technology (AMIST), University of Ulsan College of Medicine, Seoul 05505, Korea
- Asan Medical Center, Department of Surgery, University of Ulsan College of Medicine, Seoul 05505, Korea
- Correspondence: or (I.K.S.); (S.C.K.); Tel.: +82-2-3010-4173 (I.K.S.); +82-2-3010-3936 (S.C.K.)
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The Combination of Whole Cell Lipidomics Analysis and Single Cell Confocal Imaging of Fluidity and Micropolarity Provides Insight into Stress-Induced Lipid Turnover in Subcellular Organelles of Pancreatic Beta Cells. Molecules 2019; 24:molecules24203742. [PMID: 31627330 PMCID: PMC6833103 DOI: 10.3390/molecules24203742] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 10/13/2019] [Accepted: 10/14/2019] [Indexed: 12/22/2022] Open
Abstract
Modern omics techniques reveal molecular structures and cellular networks of tissues and cells in unprecedented detail. Recent advances in single cell analysis have further revolutionized all disciplines in cellular and molecular biology. These methods have also been employed in current investigations on the structure and function of insulin secreting beta cells under normal and pathological conditions that lead to an impaired glucose tolerance and type 2 diabetes. Proteomic and transcriptomic analyses have pointed to significant alterations in protein expression and function in beta cells exposed to diabetes like conditions (e.g., high glucose and/or saturated fatty acids levels). These nutritional overload stressful conditions are often defined as glucolipotoxic due to the progressive damage they cause to the cells. Our recent studies on the rat insulinoma-derived INS-1E beta cell line point to differential effects of such conditions in the phospholipid bilayers in beta cells. This review focuses on confocal microscopy-based detection of these profound alterations in the plasma membrane and membranes of insulin granules and lipid droplets in single beta cells under such nutritional load conditions.
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Function, Regulation and Biological Roles of PI3Kγ Variants. Biomolecules 2019; 9:biom9090427. [PMID: 31480354 PMCID: PMC6770443 DOI: 10.3390/biom9090427] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 08/14/2019] [Accepted: 08/15/2019] [Indexed: 12/19/2022] Open
Abstract
Phosphatidylinositide 3-kinase (PI3K) γ is the only class IB PI3K member playing significant roles in the G-protein-dependent regulation of cell signaling in health and disease. Originally found in the immune system, increasing evidence suggest a wide array of functions in the whole organism. PI3Kγ occur as two different heterodimeric variants: PI3Kγ (p87) and PI3Kγ (p101), which share the same p110γ catalytic subunit but differ in their associated non-catalytic subunit. Here we concentrate on specific PI3Kγ features including its regulation and biological functions. In particular, the roles of its non-catalytic subunits serving as the main regulators determining specificity of class IB PI3Kγ enzymes are highlighted.
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Buchanan CM, Lee KL, Shepherd PR. For Better or Worse: The Potential for Dose Limiting the On-Target Toxicity of PI 3-Kinase Inhibitors. Biomolecules 2019; 9:biom9090402. [PMID: 31443495 PMCID: PMC6770514 DOI: 10.3390/biom9090402] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 08/15/2019] [Accepted: 08/21/2019] [Indexed: 02/07/2023] Open
Abstract
The hyper-activation of the phosphoinositide (PI) 3-kinase signaling pathway is a hallmark of many cancers and overgrowth syndromes, and as a result, there has been intense interest in the development of drugs that target the various isoforms of PI 3-kinase. Given the key role PI 3-kinases play in many normal cell functions, there is significant potential for the disruption of essential cellular functions by PI 3-kinase inhibitors in normal tissues; so-called on-target drug toxicity. It is, therefore, no surprise that progress within the clinical development of PI 3-kinase inhibitors as single-agent anti-cancer therapies has been slowed by the difficulty of identifying a therapeutic window. The aim of this review is to place the cellular, tissue and whole-body effects of PI 3-kinase inhibition in the context of understanding the potential for dose limiting on-target toxicities and to introduce possible strategies to overcome these.
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Affiliation(s)
- Christina M Buchanan
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Kate L Lee
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Peter R Shepherd
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
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11
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A Comprehensive Survey of the Roles of Highly Disordered Proteins in Type 2 Diabetes. Int J Mol Sci 2017; 18:ijms18102010. [PMID: 28934129 PMCID: PMC5666700 DOI: 10.3390/ijms18102010] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 09/04/2017] [Accepted: 09/12/2017] [Indexed: 01/03/2023] Open
Abstract
Type 2 diabetes mellitus (T2DM) is a chronic and progressive disease that is strongly associated with hyperglycemia (high blood sugar) related to either insulin resistance or insufficient insulin production. Among the various molecular events and players implicated in the manifestation and development of diabetes mellitus, proteins play several important roles. The Kyoto Encyclopedia of Genes and Genomes (KEGG) database has information on 34 human proteins experimentally shown to be related to the T2DM pathogenesis. It is known that many proteins associated with different human maladies are intrinsically disordered as a whole, or contain intrinsically disordered regions. The presented study shows that T2DM is not an exception to this rule, and many proteins known to be associated with pathogenesis of this malady are intrinsically disordered. The multiparametric bioinformatics analysis utilizing several computational tools for the intrinsic disorder characterization revealed that IRS1, IRS2, IRS4, MAFA, PDX1, ADIPO, PIK3R2, PIK3R5, SoCS1, and SoCS3 are expected to be highly disordered, whereas VDCC, SoCS2, SoCS4, JNK9, PRKCZ, PRKCE, insulin, GCK, JNK8, JNK10, PYK, INSR, TNF-α, MAPK3, and Kir6.2 are classified as moderately disordered proteins, and GLUT2, GLUT4, mTOR, SUR1, MAPK1, IKKA, PRKCD, PIK3CB, and PIK3CA are predicted as mostly ordered. More focused computational analyses and intensive literature mining were conducted for a set of highly disordered proteins related to T2DM. The resulting work represents a comprehensive survey describing the major biological functions of these proteins and functional roles of their intrinsically disordered regions, which are frequently engaged in protein–protein interactions, and contain sites of various posttranslational modifications (PTMs). It is also shown that intrinsic disorder-associated PTMs may play important roles in controlling the functions of these proteins. Consideration of the T2DM proteins from the perspective of intrinsic disorder provides useful information that can potentially lead to future experimental studies that may uncover latent and novel pathways associated with the disease.
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12
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Breasson L, Sardi C, Becattini B, Zani F, Solinas G. PI3Kγ ablation does not promote diabetes in db/db mice, but improves insulin sensitivity and reduces pancreatic β-cell apoptosis. FASEB J 2017; 32:319-329. [PMID: 28904022 DOI: 10.1096/fj.201700372rr] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Accepted: 08/28/2017] [Indexed: 11/11/2022]
Abstract
PI3Kγ has emerged as a promising target for the treatment of obesity and insulin resistance; however, previous studies have indicated that PI3Kγ activity in pancreatic β cells is required for normal insulin secretion in response to glucose. Hence, a possible deterioration of insulin secretion capacity in patients who are predisposed to the failure of pancreatic β-cell function is a major concern for the pharmacologic inhibition of PI3Kγ. To address this issue, we investigated the effects of PI3Kγ ablation in db/db diabetic mice, a genetic model of obesity-driven β-cell failure and diabetes. Mice that lacked PI3Kγ were backcrossed into db/+ mice C57BL/KS (>10 generations) to obtain db/db-PI3Kγ-/- mice. db/db-PI3Kγ-/- mice and control db/db mice were phenotyped for glucose homeostasis, insulin sensitivity, insulin secretion, steatosis, metabolic inflammation, pancreatic islet morphometry, islet cellular composition, and inflammation. Pancreatic β-cell apoptosis and proliferation were also evaluated. db/db-PI3Kγ -/- mice and control db/db mice developed similar body weight, steatosis, glycemia, and insulin levels after a glucose load; however, db/db-PI3Kγ-/- mice displayed improved insulin tolerance, higher levels of fasting serum insulin, and lower pancreatic insulin content. In db/db-PI3Kγ-/- mice, the number of adipose tissue macrophages was similar to control, but displayed reduced adipose tissue neutrophils and M2-polarized adipose tissue gene expression. Finally, db/db-PI3Kγ-/- mice have more pancreatic β cells and larger islets than db/db mice, despite displaying similar islet inflammation. This phenotype could be explained by reduced β-cell apoptosis in db/db-PI3Kγ-/- mice compared with control db/db mice. Our results are consistent with the concept that the beneficial action of PI3Kγ ablation in obesity-driven glucose intolerance is largely a result of its leptin-dependent effects on adiposity and, to a lesser extent, the promotion of adipose tissue neutrophil recruitment and M1 polarization of gene expression. Of importance, our data challenge the concept that PI3Kγ is required for insulin secretion in response to glucose in vivo, and indicate that PI3Kγ ablation protects db/db mice from β-cell apoptosis and improves fasting insulin levels. We conclude that PI3Kγ inhibition in obese patients who are predisposed to β-cell failure is not expected to produce adverse effects on insulin secretion.-Breasson, L., Sardi, C., Becattini, B., Zani, F., Solinas, G. PI3Kγ ablation does not promote diabetes in db/db mice, but improves insulin sensitivity and reduces pancreatic β-cell apoptosis.
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Affiliation(s)
- Ludovic Breasson
- Department of Molecular and Clinical Medicine, The Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Claudia Sardi
- Department of Molecular and Clinical Medicine, The Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Barbara Becattini
- Department of Molecular and Clinical Medicine, The Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Fabio Zani
- Cancer Research UK Beatson Institute, Glasgow, United Kingdom
| | - Giovanni Solinas
- Department of Molecular and Clinical Medicine, The Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden;
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Foer D, Zhu M, Cardone RL, Simpson C, Sullivan R, Nemiroff S, Lee G, Kibbey RG, Petersen KF, Insogna KL. Impact of gain-of-function mutations in the low-density lipoprotein receptor-related protein 5 (LRP5) on glucose and lipid homeostasis. Osteoporos Int 2017; 28:2011-2017. [PMID: 28283687 PMCID: PMC6693506 DOI: 10.1007/s00198-017-3977-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 02/16/2017] [Indexed: 10/20/2022]
Abstract
UNLABELLED LRP5 loss-of-function mutations have been shown to cause profound osteoporosis and have been associated with impaired insulin sensitivity and dysregulated lipid metabolism. We hypothesized that gain-of-function mutations in LRP5 would also affect these parameters. We therefore studied individuals with LRP5 gain-of-function mutations exhibiting high bone mass (HBM) phenotypes and found that while there was no detected change in insulin sensitivity, there was a significant reduction in serum LDL. INTRODUCTION Wnt signaling through LRP5 represents a newly appreciated metabolic pathway, which potentially represents a target for drug discovery in type 2 diabetes and hyperlipidemia. Studies in animal models suggest a physiologic link between LRP5 and glucose and lipid homeostasis; however, whether it plays a similar role in humans is unclear. As current literature links loss-of-function LRP5 to impaired glucose and lipid metabolism, we hypothesized that individuals with an HBM-causing mutation in LRP5 would exhibit improved glucose and lipid homeostasis. Since studies in animal models have suggested that Wnt signaling augments insulin secretion, we also examined the effect of Wnt signaling on glucose-stimulated insulin secretion on human pancreatic islets. METHODS This was a matched case-control study. We used several methods to assess glucose and lipid metabolism in 11 individuals with HBM-causing mutations in LRP5. Affected study participants were recruited from previously identified kindreds with HBM-causing LRP5 mutations and included 9 males and 2 females. Two subjects that were being treated with insulin for type 2 diabetes were excluded from our analysis, as this would have obscured our ability to determine the impact of gain-of-function LRP5 mutations on glucose metabolism. The mean age of the evaluated study subjects was 55 ± 7 with a mean BMI of 27.2 ± 2.0. Control subjects were matched and recruited from the general community at an equivalent ratio, with 18 males and 4 females (mean age 56 ± 4; mean BMI 27.2 ± 1.0). Study testing was conducted at an academic medical center. RESULTS There were no statistically significant differences between affected and matched control populations for HbA1c (p = 0.06), eAG (p = 0.06), insulin (p = 0.82), HOMA-B (p = 0.34), or HOMA-IR (p = 0.66). The mean Insulin Sensitivity Index (ISI) was also similar between control and affected individuals. Total cholesterol (p = 0.43), triglycerides (TG) (p = 0.56), and HDL (p = 0.32) were not different between the same two groups. In a small subset of studied subjects, intramyocellular and hepatic lipid content were similar in the affected individuals and controls when quantified by proton magnetic resonance spectroscopy (MRS). However, the mean value for serum LDL was significantly lower (p = 0.04) in affected individuals. In primary human islets, there were no differences between control and Wnt treatment groups for insulin secretion measured as area under the curve (AUC) for first phase (p = 0.17) or second phase (p = 0.33) insulin secretion. CONCLUSIONS Although our sample size was small, our data do not support the hypothesis that HBM-causing LRP5 mutations, associated with increased Wnt signaling, improve glucose metabolism in humans. However, it does appear that LRP5 variants may affect LDL metabolism, a major risk factor for coronary artery disease. The molecular mechanisms underpinning this effect warrant further study.
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Affiliation(s)
- D Foer
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA
| | - M Zhu
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA
| | - R L Cardone
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA
| | - C Simpson
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA
| | - R Sullivan
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA
| | - S Nemiroff
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA
| | - G Lee
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA
| | - R G Kibbey
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, 06520, USA
| | - K F Petersen
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA
- Novo-Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - K L Insogna
- Section of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, PO Box 208020, 333 Cedar Street, New Haven, CT, 06520, USA.
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Xu Y, Toomre DK, Bogan JS, Hao M. Excess cholesterol inhibits glucose-stimulated fusion pore dynamics in insulin exocytosis. J Cell Mol Med 2017; 21:2950-2962. [PMID: 28544529 PMCID: PMC5661106 DOI: 10.1111/jcmm.13207] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 03/28/2017] [Indexed: 01/06/2023] Open
Abstract
Type 2 diabetes is caused by defects in both insulin sensitivity and insulin secretion. Glucose triggers insulin secretion by causing exocytosis of insulin granules from pancreatic β-cells. High circulating cholesterol levels and a diminished capacity of serum to remove cholesterol from β-cells are observed in diabetic individuals. Both of these effects can lead to cholesterol accumulation in β-cells and contribute to β-cell dysfunction. However, the molecular mechanisms by which cholesterol accumulation impairs β-cell function remain largely unknown. Here, we used total internal reflection fluorescence microscopy to address, at the single-granule level, the role of cholesterol in regulating fusion pore dynamics during insulin exocytosis. We focused particularly on the effects of cholesterol overload, which is relevant to type 2 diabetes. We show that excess cholesterol reduced the number of glucose-stimulated fusion events, and modulated the proportion of full fusion and kiss-and-run fusion events. Analysis of single exocytic events revealed distinct fusion kinetics, with more clustered and compound exocytosis observed in cholesterol-overloaded β-cells. We provide evidence for the involvement of the GTPase dynamin, which is regulated in part by cholesterol-induced phosphatidylinositol 4,5-bisphosphate enrichment in the plasma membrane, in the switch between full fusion and kiss-and-run fusion. Characterization of insulin exocytosis offers insights into the role that elevated cholesterol may play in the development of type 2 diabetes.
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Affiliation(s)
- Yingke Xu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Department of Bioengineering, Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang University, Hangzhou, China
| | - Derek K Toomre
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Jonathan S Bogan
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
| | - Mingming Hao
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.,Department of Biochemistry, Weill Cornell Medical College, New York, NY, USA
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Maulucci G, Cohen O, Daniel B, Sansone A, Petropoulou PI, Filou S, Spyridonidis A, Pani G, De Spirito M, Chatgilialoglu C, Ferreri C, Kypreos KE, Sasson S. Fatty acid-related modulations of membrane fluidity in cells: detection and implications. Free Radic Res 2016; 50:S40-S50. [PMID: 27593084 DOI: 10.1080/10715762.2016.1231403] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Metabolic homeostasis of fatty acids is complex and well-regulated in all organisms. The biosynthesis of saturated fatty acids (SFA) in mammals provides substrates for β-oxidation and ATP production. Monounsaturated fatty acids (MUFA) are products of desaturases that introduce a methylene group in cis geometry in SFA. Polyunsaturated fatty acids (n-6 and n-3 PUFA) are products of elongation and desaturation of the essential linoleic acid and α-linolenic acid, respectively. The liver processes dietary fatty acids and exports them in lipoproteins for distribution and storage in peripheral tissues. The three types of fatty acids are integrated in membrane phospholipids and determine their biophysical properties and functions. This study was aimed at investigating effects of fatty acids on membrane biophysical properties under varying nutritional and pathological conditions, by integrating lipidomic analysis of membrane phospholipids with functional two-photon microscopy (fTPM) of cellular membranes. This approach was applied to two case studies: first, pancreatic beta-cells, to investigate hormetic and detrimental effects of lipids. Second, red blood cells extracted from a genetic mouse model defective in lipoproteins, to understand the role of lipids in hepatic diseases and metabolic syndrome and their effect on circulating cells.
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Affiliation(s)
- G Maulucci
- a Institute of Physics, Università Cattolica del Sacro Cuore , Roma , Italy
| | - O Cohen
- b Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Faculty of Medicine , The Hebrew University , Jerusalem , Israel
| | - B Daniel
- b Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Faculty of Medicine , The Hebrew University , Jerusalem , Israel
| | - A Sansone
- c ISOF, BioFreeRadicals Group, Consiglio Nazionale delle Ricerche , Bologna , Italy
| | - P I Petropoulou
- d Department of Pharmacology , University of Patras Medical School , Rio , Greece
| | - S Filou
- d Department of Pharmacology , University of Patras Medical School , Rio , Greece
| | - A Spyridonidis
- e Hematology Department , University of Patras Medical School , Rio , Greece
| | - G Pani
- f Institute of General Pathology, Università Cattolica del Sacro Cuore , Roma , Italy
| | - M De Spirito
- a Institute of Physics, Università Cattolica del Sacro Cuore , Roma , Italy
| | - C Chatgilialoglu
- c ISOF, BioFreeRadicals Group, Consiglio Nazionale delle Ricerche , Bologna , Italy
| | - C Ferreri
- c ISOF, BioFreeRadicals Group, Consiglio Nazionale delle Ricerche , Bologna , Italy
| | - K E Kypreos
- d Department of Pharmacology , University of Patras Medical School , Rio , Greece
| | - S Sasson
- b Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Faculty of Medicine , The Hebrew University , Jerusalem , Israel
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16
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Bhattacharya S, McElhanon KE, Gushchina LV, Weisleder N. Role of phosphatidylinositol-4,5-bisphosphate 3-kinase signaling in vesicular trafficking. Life Sci 2016; 167:39-45. [PMID: 27760304 DOI: 10.1016/j.lfs.2016.10.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 10/13/2016] [Accepted: 10/14/2016] [Indexed: 02/07/2023]
Abstract
Phosphatidylinositol-4,5-bisphosphate 3-kinases (PI3Ks) are regulatory enzymes involved in the generation of lipid species that modulate cellular signaling pathways through downstream effectors to influence a variety of cellular functions. Years of intensive study of PI3Ks have produced a significant body of literature in many areas, including that PI3K can mediate intracellular vesicular trafficking and through these actions contribute to a number of important physiological functions. This review focuses on the crucial roles that PI3K and AKT, a major downstream partner of PI3K, play in the regulation of vesicle trafficking during various forms of vesicular endocytosis and exocytosis.
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Affiliation(s)
- Sayak Bhattacharya
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States
| | - Kevin E McElhanon
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States
| | - Liubov V Gushchina
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States
| | - Noah Weisleder
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States.
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17
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Quinault A, Gausseres B, Bailbe D, Chebbah N, Portha B, Movassat J, Tourrel-Cuzin C. Disrupted dynamics of F-actin and insulin granule fusion in INS-1 832/13 beta-cells exposed to glucotoxicity: partial restoration by glucagon-like peptide 1. Biochim Biophys Acta Mol Basis Dis 2016; 1862:1401-11. [DOI: 10.1016/j.bbadis.2016.04.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 03/22/2016] [Accepted: 04/11/2016] [Indexed: 01/11/2023]
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18
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Kolic J, Manning Fox JE, Chepurny OG, Spigelman AF, Ferdaoussi M, Schwede F, Holz GG, MacDonald PE. PI3 kinases p110α and PI3K-C2β negatively regulate cAMP via PDE3/8 to control insulin secretion in mouse and human islets. Mol Metab 2016; 5:459-471. [PMID: 27408772 PMCID: PMC4921792 DOI: 10.1016/j.molmet.2016.05.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Revised: 04/26/2016] [Accepted: 05/04/2016] [Indexed: 01/09/2023] Open
Abstract
OBJECTIVES Phosphatidylinositol-3-OH kinase (PI3K) signalling in the endocrine pancreas contributes to glycaemic control. However, the mechanism by which PI3K modulates insulin secretion from the pancreatic beta cell is poorly understood. Thus, our objective was two-fold; to determine the signalling pathway by which acute PI3K inhibition enhances glucose-stimulated insulin secretion (GSIS) and to examine the role of this pathway in islets from type-2 diabetic (T2D) donors. METHODS Isolated islets from mice and non-diabetic or T2D human donors, or INS 832/13 cells, were treated with inhibitors of PI3K and/or phosphodiesterases (PDEs). The expression of PI3K-C2β was knocked down using siRNA. We measured insulin release, single-cell exocytosis, intracellular Ca(2+) responses ([Ca(2+)]i) and Ca(2+) channel currents, intracellular cAMP concentrations ([cAMP]i), and activation of cAMP-dependent protein kinase A (PKA) and protein kinase B (PKB/AKT). RESULTS The non-specific PI3K inhibitor wortmannin amplifies GSIS, raises [cAMP]i and activates PKA, but is without effect in T2D islets. Direct inhibition of specific PDE isoforms demonstrates a role for PDE3 (in humans and mice) and PDE8 (in mice) downstream of PI3K, and restores glucose-responsiveness of T2D islets. We implicate a role for the Class II PI3K catalytic isoform PI3K-C2β in this effect by limiting beta cell exocytosis. CONCLUSIONS PI3K limits GSIS via PDE3 in human islets. While inhibition of p110α or PIK-C2β signalling per se, may promote nutrient-stimulated insulin release, we now suggest that this signalling pathway is perturbed in islets from T2D donors.
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Affiliation(s)
- Jelena Kolic
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada.
| | - Jocelyn E Manning Fox
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
| | - Oleg G Chepurny
- Department of Medicine, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA
| | - Aliya F Spigelman
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
| | - Mourad Ferdaoussi
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
| | - Frank Schwede
- BIOLOG Life Science Institute, 28199 Bremen, Germany
| | - George G Holz
- Department of Medicine, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA; Department of Pharmacology, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA
| | - Patrick E MacDonald
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
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Gala-Lopez BL, Pepper AR, Pawlick RL, O'Gorman D, Kin T, Bruni A, Abualhassan N, Bral M, Bautista A, Manning Fox JE, Young LG, MacDonald PE, Shapiro AMJ. Antiaging Glycopeptide Protects Human Islets Against Tacrolimus-Related Injury and Facilitates Engraftment in Mice. Diabetes 2016; 65:451-62. [PMID: 26581595 DOI: 10.2337/db15-0764] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 11/10/2015] [Indexed: 02/05/2023]
Abstract
Clinical islet transplantation has become an established treatment modality for selected patients with type 1 diabetes. However, a large proportion of transplanted islets is lost through multiple factors, including immunosuppressant-related toxicity, often requiring more than one donor to achieve insulin independence. On the basis of the cytoprotective capabilities of antifreeze proteins (AFPs), we hypothesized that supplementation of islets with synthetic AFP analog antiaging glycopeptide (AAGP) would enhance posttransplant engraftment and function and protect against tacrolimus (Tac) toxicity. In vitro and in vivo islet Tac exposure elicited significant but reversible reduction in insulin secretion in both mouse and human islets. Supplementation with AAGP resulted in improvement of islet survival (Tac(+) vs. Tac+AAGP, 31.5% vs. 67.6%, P < 0.01) coupled with better insulin secretion (area under the curve: Tac(+) vs. Tac+AAGP, 7.3 vs. 129.2 mmol/L/60 min, P < 0.001). The addition of AAGP reduced oxidative stress, enhanced insulin exocytosis, improved apoptosis, and improved engraftment in mice by decreasing expression of interleukin (IL)-1β, IL-6, keratinocyte chemokine, and tumor necrosis factor-α. Finally, transplant efficacy was superior in the Tac+AAGP group and was similar to islets not exposed to Tac, despite receiving continuous treatment for a limited time. Thus, supplementation with AAGP during culture improves islet potency and attenuates long-term Tac-induced graft dysfunction.
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Affiliation(s)
- Boris L Gala-Lopez
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada Canadian National Transplant Research Program, University of Alberta, Edmonton, Alberta, Canada
| | - Andrew R Pepper
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada Canadian National Transplant Research Program, University of Alberta, Edmonton, Alberta, Canada
| | - Rena L Pawlick
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Doug O'Gorman
- Clinical Islet Transplant Program, University of Alberta, Edmonton, Alberta, Canada
| | - Tatsuya Kin
- Clinical Islet Transplant Program, University of Alberta, Edmonton, Alberta, Canada
| | - Antonio Bruni
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada Canadian National Transplant Research Program, University of Alberta, Edmonton, Alberta, Canada
| | - Nasser Abualhassan
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada Canadian National Transplant Research Program, University of Alberta, Edmonton, Alberta, Canada
| | - Mariusz Bral
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Austin Bautista
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Jocelyn E Manning Fox
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Lachlan G Young
- ProtoKinetix Inc., Vancouver, Vancouver, British Columbia, Canada
| | - Patrick E MacDonald
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - A M James Shapiro
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada Canadian National Transplant Research Program, University of Alberta, Edmonton, Alberta, Canada Clinical Islet Transplant Program, University of Alberta, Edmonton, Alberta, Canada
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Abstract
Type 2 diabetes is a complex disease. It results from a failure of the body to maintain energy homoeostasis. Multicellular organisms have evolved complex strategies to preserve a relatively stable internal nutrient environment, despite fluctuations in external nutrient availability. This complex strategy involves the co-ordinated responses of multiple organs to promote storage or mobilization of energy sources according to the availability of nutrients and cellular bioenergetics needs. The endocrine pancreas plays a central role in these processes by secreting insulin and glucagon. When this co-ordinated effort fails, hyperglycaemia and hyperlipidaemia develops, characterizing a state of metabolic imbalance and ultimately overt diabetes. Although diabetes is most likely a collection of diseases, scientists are starting to identify genetic components and environmental triggers. Genome-wide association studies revealed that by and large, gene variants associated with type 2 diabetes are implicated in pancreatic β-cell function, suggesting that the β-cell may be the weakest link in the chain of events that results in diabetes. Thus, it is critical to understand how environmental cues affect the β-cell. Phosphoinositides are important 'decoders' of environmental cues. As such, these lipids have been implicated in cellular responses to a wide range of growth factors, hormones, stress agents, nutrients and metabolites. Here we will review some of the well-established and potential new roles for phosphoinositides in β-cell function/dysfunction and discuss how our knowledge of phosphoinositide signalling could aid in the identification of potential strategies for treating or preventing type 2 diabetes.
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Affiliation(s)
- Lucia E Rameh
- Department of Medicine, Boston University School of Medicine, 650 Albany Street, Boston, MA 02118, U.S.A.
| | - Jude T Deeney
- Department of Medicine, Boston University School of Medicine, 650 Albany Street, Boston, MA 02118, U.S.A
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21
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Affiliation(s)
- Vincenzo Cirulli
- Diabetes and Obesity Center of Excellence, Department of Medicine, and Institute for Stem Cell and Regenerative Medicine, Department of Pharmacology, University of Washington, Seattle, WA
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22
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Pemberton JG, Stafford JL, Chang JP. Ligand-selective signal transduction by two endogenous GnRH isoforms involves biased activation of the class I PI3K catalytic subunits p110β, p110γ, and p110δ in pituitary gonadotropes and somatotropes. Endocrinology 2015; 156:218-30. [PMID: 25343277 DOI: 10.1210/en.2014-1640] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In goldfish, 2 endogenous GnRH isoforms, GnRH2 and GnRH3, are released at the pituitary and directly stimulate LH and GH release using the same population of GnRH receptors (GnRHRs) but with GnRH-specific transduction mechanisms. Previously, we have shown that phosphoinositide 3-kinases (PI3Ks) mediate GnRH2- and GnRH3-stimulated LH and GH release. Among the 3 classes of PI3Ks, class I PI3Ks are the best characterized and consist of 4 110-kDa catalytic isoforms (p110α, p110β, p110γ, and p110δ). Importantly, p110β and p110γ, but not p110α or p110δ, can be directly activated by the Gβγ heterodimer of Gαβγ protein complexes. In the present study, we examined the expression of class I PI3K isoforms and the effects of selective inhibitors of p110α, p110β, p110γ, and p110δ catalytic activity on basal, as well as acute, GnRH2- and GnRH3-stimulated LH and GH release responses using primary cultures of dispersed goldfish pituitary cells in column perifusion. Results demonstrate that p110γ and p110δ are involved in the control of basal LH and GH release, whereas p110α and p110β only regulate basal LH secretion. However, p110β and p110γ both participated in GnRH3- and GnRH2-stimulated GH release, whereas p110β and p110γ mediated GnRH2- and GnRH3-induced LH release responses, respectively. GnRH2- and GnRH3-stimulated LH release, as well as GnRH3-elicited GH release, also required p110δ. These results constitute the first evidence for the differential involvement of class I PI3K catalytic subunits in GnRH actions, in general, and suggest that GnRH2 and GnRH3 binding to GnRHRs can bias the activation of class I PI3K signaling to mediate hormone release responses in 2 distinct pituitary cell types. The involvement of both class IA and IB PI3Ks implicates Gβγ subunits, as well as other known regulators of class I PI3Ks, as important components of GnRHR-mediated responses that could influence GnRH-selective signaling in other cell types.
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Affiliation(s)
- Joshua G Pemberton
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9
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23
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Kolic J, Spigelman AF, Smith AM, Manning Fox JE, MacDonald PE. Insulin secretion induced by glucose-dependent insulinotropic polypeptide requires phosphatidylinositol 3-kinase γ in rodent and human β-cells. J Biol Chem 2014; 289:32109-32120. [PMID: 25288806 DOI: 10.1074/jbc.m114.577510] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
PI3Kγ, a G-protein-coupled type 1B phosphoinositol 3-kinase, exhibits a basal glucose-independent activity in β-cells and can be activated by the glucose-dependent insulinotropic polypeptide (GIP). We therefore investigated the role of the PI3Kγ catalytic subunit (p110γ) in insulin secretion and β-cell exocytosis stimulated by GIP. We inhibited p110γ with AS604850 (1 μmol/liter) or knocked it down using an shRNA adenovirus or siRNA duplex in mouse and human islets and β-cells. Inhibition of PI3Kγ blunted the exocytotic and insulinotropic response to GIP receptor activation, whereas responses to the glucagon-like peptide-1 or the glucagon-like peptide-1 receptor agonist exendin-4 were unchanged. Downstream, we find that GIP, much like glucose stimulation, activates the small GTPase protein Rac1 to induce actin remodeling. Inhibition of PI3Kγ blocked these effects of GIP. Although exendin-4 could also stimulate actin remodeling, this was not prevented by p110γ inhibition. Finally, forced actin depolymerization with latrunculin B restored the exocytotic and secretory responses to GIP during PI3Kγ inhibition, demonstrating that the loss of GIP-induced actin depolymerization was indeed limiting insulin exocytosis.
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Affiliation(s)
- Jelena Kolic
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Aliya F Spigelman
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Alannah M Smith
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Jocelyn E Manning Fox
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Patrick E MacDonald
- Department of Pharmacology, and the Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.
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Patterson JN, Cousteils K, Lou JW, Manning Fox JE, MacDonald PE, Joseph JW. Mitochondrial metabolism of pyruvate is essential for regulating glucose-stimulated insulin secretion. J Biol Chem 2014; 289:13335-46. [PMID: 24675076 DOI: 10.1074/jbc.m113.521666] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
It is well known that mitochondrial metabolism of pyruvate is critical for insulin secretion; however, we know little about how pyruvate is transported into mitochondria in β-cells. Part of the reason for this lack of knowledge is that the carrier gene was only discovered in 2012. In the current study, we assess the role of the recently identified carrier in the regulation of insulin secretion. Our studies show that β-cells express both mitochondrial pyruvate carriers (Mpc1 and Mpc2). Using both pharmacological inhibitors and siRNA-mediated knockdown of the MPCs we show that this carrier plays a key role in regulating insulin secretion in clonal 832/13 β-cells as well as rat and human islets. We also show that the MPC is an essential regulator of both the ATP-regulated potassium (KATP) channel-dependent and -independent pathways of insulin secretion. Inhibition of the MPC blocks the glucose-stimulated increase in two key signaling molecules involved in regulating insulin secretion, the ATP/ADP ratio and NADPH/NADP(+) ratio. The MPC also plays a role in in vivo glucose homeostasis as inhibition of MPC by the pharmacological inhibitor α-cyano-β-(1-phenylindol-3-yl)-acrylate (UK5099) resulted in impaired glucose tolerance. These studies clearly show that the newly identified mitochondrial pyruvate carrier sits at an important branching point in nutrient metabolism and that it is an essential regulator of insulin secretion.
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Affiliation(s)
- Jessica N Patterson
- From the School of Pharmacy, University of Waterloo, Waterloo, 10A Victoria Street South, Ontario N2G 1C5, Canada and
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25
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Stockinger S, Albers T, Duerr CU, Ménard S, Pütsep K, Andersson M, Hornef MW. Interleukin-13-mediated paneth cell degranulation and antimicrobial peptide release. J Innate Immun 2014; 6:530-41. [PMID: 24556597 DOI: 10.1159/000357644] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 11/30/2013] [Indexed: 12/18/2022] Open
Abstract
Paneth cell-derived enteric antimicrobial peptides significantly contribute to antibacterial host defense and host-microbial homeostasis. Regulation occurs by enzymatic processing and release into the small intestinal lumen, but the stimuli involved are incompletely understood. Here, the capacity of various microbial and immune stimuli to induce antimicrobial peptide release from small intestinal tissue was systematically evaluated using antibacterial activity testing, immunostaining for Paneth cell granules and mass spectrometry. We confirmed the stimulatory activity of the muscarinic receptor agonist carbachol and the nucleotide-binding oligomerization domain ligand muramyl dipeptide. In contrast, no release of antibacterial activity was noted after treatment with the Toll-like receptor ligands poly(I:C), lipopolysaccharide or CpG, and the cytokines interleukin (IL)-15, IL-22, IL-28 and interferon-γ. Rapid Paneth cell degranulation and antimicrobial activity release, however, was observed after stimulation with the endogenous mediators IL-4 and IL-13. This process required phosphatidylinositol 3-kinase and was associated with protein kinase B phosphorylation in Paneth cells. Flow cytometric analysis confirmed expression of the IL-13 receptor α1 on isolated Paneth cells. Our findings identify a novel role of IL-13 as inducer of Paneth cell degranulation and enteric antimicrobial peptide release. IL-13 may thus contribute to mucosal antimicrobial host defense and host microbial homeostasis.
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Affiliation(s)
- Silvia Stockinger
- Institute for Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Hannover, Germany
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26
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Yang YHC, Manning Fox JE, Zhang KL, MacDonald PE, Johnson JD. Intraislet SLIT-ROBO signaling is required for beta-cell survival and potentiates insulin secretion. Proc Natl Acad Sci U S A 2013; 110:16480-5. [PMID: 24065825 PMCID: PMC3799350 DOI: 10.1073/pnas.1214312110] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We previously cataloged putative autocrine/paracrine signaling loops in pancreatic islets, including factors best known for their roles in axon guidance. Emerging evidence points to nonneuronal roles for these factors, including the Slit-Roundabout receptor (Robo) family, in cell growth, migration, and survival. We found SLIT1 and SLIT3 in both beta cells and alpha cells, whereas SLIT2 was predominantly expressed in beta cells. ROBO1 and ROBO2 receptors were detected in beta and alpha cells. Remarkably, even modest knockdown of Slit production resulted in significant beta-cell death, demonstrating a critical autocrine/paracrine survival role for this pathway. Indeed, recombinant SLIT1, SLIT2, and SLIT3 decreased serum deprivation, cytokine, and thapsigargin-induced cell death under hyperglycemic conditions. SLIT treatment also induced a gradual release of endoplasmic reticulum luminal Ca(2+), suggesting a unique molecular mechanism capable of protecting beta cells from endoplasmic reticulum stress-induced apoptosis. SLIT treatment was also associated with rapid actin remodeling. SLITs potentiated glucose-stimulated insulin secretion and increased the frequency of glucose-induced Ca(2+) oscillations. These observations point to unexpected roles for local Slit secretion in the survival and function of pancreatic beta cells. Because diabetes results from a deficiency in functional beta-cell mass, these studies may contribute to therapeutic approaches for improving beta-cell survival and function.
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Affiliation(s)
- Yu Hsuan Carol Yang
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3; and
| | - Jocelyn E. Manning Fox
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada T6G 2E1
| | - Kevin L. Zhang
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3; and
| | - Patrick E. MacDonald
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada T6G 2E1
| | - James D. Johnson
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3; and
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Abstract
The pancreatic islet β cell senses circulating levels of calorigenic nutrients to secrete insulin according to the needs of the organism. Altered insulin secretion is linked to various disorders such as diabetes, hypoglycemic states, and cardiometabolic diseases. Fuel stimuli, including glucose, free fatty acids, and amino acids, promote insulin granule exocytosis primarily via their metabolism in β cells and the production of key signaling metabolites. This paper reviews our current knowledge of the pathways involved in both positive and negative metabolic signaling for insulin secretion and assesses the role of established and candidate metabolic coupling factors, keeping recent developments in focus.
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Affiliation(s)
- Marc Prentki
- Molecular Nutrition Unit, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, QC, Canada.
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Kolic J, Spigelman AF, Plummer G, Leung E, Hajmrle C, Kin T, Shapiro AMJ, Manning Fox JE, MacDonald PE. Distinct and opposing roles for the phosphatidylinositol 3-OH kinase catalytic subunits p110α and p110β in the regulation of insulin secretion from rodent and human beta cells. Diabetologia 2013; 56:1339-49. [PMID: 23568272 DOI: 10.1007/s00125-013-2882-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 02/18/2013] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS Phosphatidylinositol 3-OH kinases (PI3Ks) regulate beta cell mass, gene transcription, and function, although the contribution of the specific isoforms is unknown. As reduced type 1A PI3K signalling is thought to contribute to impaired insulin secretion, we investigated the role of the type 1A PI3K catalytic subunits α and β (p110α and -β) in insulin granule recruitment and exocytosis in rodent and human islets. METHODS The p110α and p110β subunits were inhibited pharmacologically or by small hairpin (sh)RNA-mediated knockdown, and were directly infused or overexpressed in mouse and human islets, beta cells and INS-1 832/13 cells. Glucose-stimulated insulin secretion (GSIS), single-cell exocytosis, Ca(2+) signalling, plasma membrane granule localisation, and actin density were monitored. RESULTS Inhibition or knockdown of p110α increased GSIS. This was not due to altered Ca(2+) responses, depolymerisation of cortical actin or increased cortical granule density, but to enhanced Ca(2+)-dependent exocytosis. Intracellular infusion of recombinant PI3Kα (p110α/p85β) blocked exocytosis. Conversely, knockdown (but not pharmacological inhibition) of p110β blunted GSIS, reduced cortical granule density and impaired exocytosis. Exocytosis was rescued by direct intracellular infusion of recombinant PI3Kβ (p110β/p85β) even when p110β catalytic activity was inhibited. Conversely, both the wild-type p110β and a catalytically inactive mutant directly facilitated exocytosis. CONCLUSIONS/INTERPRETATION Type 1A PI3K isoforms have distinct and opposing roles in the acute regulation of insulin secretion. While p110α acts as a negative regulator of beta cell exocytosis and insulin secretion, p110β is a positive regulator of insulin secretion through a mechanism separate from its catalytic activity.
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Affiliation(s)
- J Kolic
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada T6G 2E1
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30
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Asahara S, Shibutani Y, Teruyama K, Inoue HY, Kawada Y, Etoh H, Matsuda T, Kimura-Koyanagi M, Hashimoto N, Sakahara M, Fujimoto W, Takahashi H, Ueda S, Hosooka T, Satoh T, Inoue H, Matsumoto M, Aiba A, Kasuga M, Kido Y. Ras-related C3 botulinum toxin substrate 1 (RAC1) regulates glucose-stimulated insulin secretion via modulation of F-actin. Diabetologia 2013; 56:1088-97. [PMID: 23412604 PMCID: PMC3622740 DOI: 10.1007/s00125-013-2849-5] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 01/17/2013] [Indexed: 11/03/2022]
Abstract
AIMS/HYPOTHESIS The small G-protein ras-related C3 botulinum toxin substrate 1 (RAC1) plays various roles in mammalian cells, such as in the regulation of cytoskeletal organisation, cell adhesion, migration and morphological changes. The present study examines the effects of RAC1 ablation on pancreatic beta cell function. METHODS Isolated islets from pancreatic beta cell-specific Rac1-knockout (betaRac1(-/-)) mice and RAC1 knockdown INS-1 insulinoma cells treated with small interfering RNA were used to investigate insulin secretion and cytoskeletal organisation in pancreatic beta cells. RESULTS BetaRac1(-/-) mice showed decreased glucose-stimulated insulin secretion, while there were no apparent differences in islet morphology. Isolated islets from the mice had blunted insulin secretion in response to high glucose levels. In RAC1 knockdown INS-1 cells, insulin secretion was also decreased in response to high glucose levels, consistent with the phenotype of betaRac1(-/-) mice. Even under high glucose levels, RAC1 knockdown INS-1 cells remained intact with F-actin, which inhibits the recruitment of the insulin granules, resulting in an inhibition of insulin secretion. CONCLUSIONS/INTERPRETATION In RAC1-deficient pancreatic beta cells, F-actin acts as a barrier for insulin granules and reduces glucose-stimulated insulin secretion.
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Affiliation(s)
- S. Asahara
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Y. Shibutani
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - K. Teruyama
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - H. Y. Inoue
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - Y. Kawada
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - H. Etoh
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
| | - T. Matsuda
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - M. Kimura-Koyanagi
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - N. Hashimoto
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - M. Sakahara
- Cancer Institute, Japanese Foundation of Cancer Research, Tokyo, Japan
| | - W. Fujimoto
- Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - H. Takahashi
- Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - S. Ueda
- Kobe University Graduate School of Agricultural Science, Kobe, Japan
| | - T. Hosooka
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - T. Satoh
- Division of Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - H. Inoue
- Department of Physiology and Metabolism, Brain/Liver Interface Medicine Research Center, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - M. Matsumoto
- Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - A. Aiba
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - M. Kasuga
- Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Y. Kido
- Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan
- Division of Medical Chemistry, Kobe University Graduate School of Health Sciences, Kobe, 654-0142 Japan
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Motoshige H, Oyama K, Takahashi K, Sakurai K. Involvement of phosphatidylinositol 3-kinase/Akt pathway in gemcitabine-induced apoptosis-like cell death in insulinoma cell line INS-1. Biol Pharm Bull 2013; 35:1932-40. [PMID: 23123465 DOI: 10.1248/bpb.b12-00298] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study demonstrated gemcitabine-induced cytotoxicity in the insulinoma cell line INS-1. Gemcitabine inhibited INS-1 cell proliferation and maintained consistent cell number for 24 h, and then caused apoptosis within 48 h of incubation. Since gemcitabine activates the phosphatidylinositol 3-kinase (PI3-K)/Akt pathway, which is involved in the resistance of pancreatic exocrine cancer to gemcitabine, we investigated the participation of this pathway in gemcitabine-induced cytotoxicity in INS-1 cells. LY294002 and wortmannin, two PI3-K inhibitors, significantly prevented gemcitabine-induced cytotoxicity in INS-1 cells, indicating that the PI3-K/Akt pathway is involved in gemcitabine-induced cytotoxicity. Gemcitabine-induced Akt phosphorylation in INS-1 cells was prevented by LY294002. Although gemcitabine induced cell cycle arrest at the G1 and early S phases, LY294002 did not inhibit the cell cycle. These data suggest that PI3-K activation does not influence gemcitabine-induced cell cycle arrest. In gemcitabine-treated cells, nuclear fragmentation and DNA ladder formation were observed. These findings suggest that gemcitabine induced apoptotic cell death in INS-1 cells through the activation of the PI3-K/Akt pathway.
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Affiliation(s)
- Hironori Motoshige
- Division of Biochemistry, Department of Life Science, School of Pharmacy, Hokkaido Pharmaceutical University, 7–1 Katsuraoka-cho, Otaru, Hokkaido 047–0264, Japan
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Narang D, Kerr PM, Baserman J, Tam R, Yang W, Searle G, Manning-Fox JE, Paulsen IM, Kozuska JL, MacDonald PE, Light PE, Holt A, Plane F. Triton X-100 inhibits L-type voltage-operated calcium channels. Can J Physiol Pharmacol 2013; 91:316-24. [PMID: 23627843 DOI: 10.1139/cjpp-2012-0257] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Triton X-100 (TX-100) is a nonionic detergent frequently used at millimolar concentrations to disrupt cell membranes and solubilize proteins. At low micromolar concentrations, TX-100 has been reported to inhibit the function of potassium channels. Here, we have used electrophysiological and functional techniques to examine the effects of TX-100 on another class of ion channels, L-type voltage-operated calcium channels (VOCCs). TX-100 (30 nmol·L(-1) to 3 μmol·L(-1)) caused reversible concentration-dependent inhibition of recombinant L-type VOCC (CaV 1.2) currents and of native L-type VOCC currents recorded from rat vascular smooth muscle cells and cardiac myocytes, and murine and human pancreatic β-cells. In functional studies, TX-100 (165 nmol·L(-1) to 3.4 μmol·L(-1)) caused concentration-dependent relaxation of rat isolated mesenteric resistance arteries prestimulated with phenylephrine or KCl. This effect was independent of the endothelium. TX-100 (1.6 μmol·L(-1)) inhibited depolarization-induced exocytosis in both murine and human isolated pancreatic β-cells. These data indicate that at concentrations within the nanomolar to low micromolar range, TX-100 significantly inhibits L-type VOCC activity in a number of cell types, an effect paralleled by inhibition of cell functions dependent upon activation of these channels. This inhibition occurs at concentrations below those used to solubilize proteins and may compromise the use of solutions containing TX-100 in bioassays.
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Affiliation(s)
- Deepak Narang
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
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Cremasco V, Decker CE, Stumpo D, Blackshear PJ, Nakayama KI, Nakayama K, Lupu TS, Graham DB, Novack DV, Faccio R. Protein kinase C-delta deficiency perturbs bone homeostasis by selective uncoupling of cathepsin K secretion and ruffled border formation in osteoclasts. J Bone Miner Res 2012; 27:2452-63. [PMID: 22806935 PMCID: PMC3498518 DOI: 10.1002/jbmr.1701] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 06/12/2012] [Accepted: 06/26/2012] [Indexed: 01/27/2023]
Abstract
Bone homeostasis requires stringent regulation of osteoclasts, which secrete proteolytic enzymes to degrade the bone matrix. Despite recent progress in understanding how bone resorption occurs, the mechanisms regulating osteoclast secretion, and in particular the trafficking route of cathepsin K vesicles, remain elusive. Using a genetic approach, we describe the requirement for protein kinase C-delta (PKCδ) in regulating bone resorption by affecting cathepsin K exocytosis. Importantly, PKCδ deficiency does not perturb formation of the ruffled border or trafficking of lysosomal vesicles containing the vacuolar-ATPase (v-ATPase). Mechanistically, we find that cathepsin K exocytosis is controlled by PKCδ through modulation of the actin bundling protein myristoylated alanine-rich C-kinase substrate (MARCKS). The relevance of our finding is emphasized in vivo because PKCδ-/- mice exhibit increased bone mass and are protected from pathological bone loss in a model of experimental postmenopausal osteoporosis. Collectively, our data provide novel mechanistic insights into the pathways that selectively promote secretion of cathepsin K lysosomes independently of ruffled border formation, providing evidence of the presence of multiple mechanisms that regulate lysosomal exocytosis in osteoclasts.
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Affiliation(s)
- Viviana Cremasco
- Department of Orthopaedics; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Corinne E. Decker
- Department of Orthopaedics; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Deborah Stumpo
- Laboratory of Signal transduction; National Institute of Environmental Health Science; Research Triangle Park, NC, 27709; USA
| | - Perry J. Blackshear
- Laboratory of Signal transduction; National Institute of Environmental Health Science; Research Triangle Park, NC, 27709; USA
| | - Keiichi I. Nakayama
- Department of Molecular and Cellular Biology; Medical Institute of Bioregulation; Kyushu University; Fukuoka, Fukuoka 812-8582; JAPAN
| | - Keiko Nakayama
- Department of Developmental Genetics; Center for Translational and Advanced Animal Research; Graduate School of Medicine; Tohoku University; Aoba-ku, Sendai 980-8575; Japan
| | - Traian S. Lupu
- Department of Orthopaedics; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Daniel B. Graham
- Department of Pathology and Immunology; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Deborah V. Novack
- Department of Pathology and Immunology; Washington University School of Medicine; St. Louis, MO, 63110; USA
| | - Roberta Faccio
- Department of Orthopaedics; Washington University School of Medicine; St. Louis, MO, 63110; USA
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Mourad NI, Nenquin M, Henquin JC. cAMP-mediated and metabolic amplification of insulin secretion are distinct pathways sharing independence of β-cell microfilaments. Endocrinology 2012; 153:4644-54. [PMID: 22948217 DOI: 10.1210/en.2012-1450] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Insulin secretion is triggered by an increase in the cytosolic calcium concentration ([Ca(2+)](c)) in β-cells. Ca(2+)-induced exocytosis of insulin granules can be augmented by metabolic amplification (unknown signals generated through glucose metabolism) or neurohormonal amplification (in particular cAMP mediated). Functional actin microfilaments are not required for metabolic amplification, but their possible role in cAMP-mediated amplification is unknown. It is also uncertain whether cAMP (generated in response to glucose) is implicated in metabolic amplification. These questions were addressed using isolated mouse islets. cAMP levels were increased by phosphodiesterase inhibition (with isobutylmethylxanthine) and adenylate-cyclase stimulation (with forskolin or glucagon-like peptide-1, 7-36 amide). Raising cAMP levels had no steady-state impact on actin polymerization in control islets. Neither disruption (depolymerization by latrunculin) nor stabilization (polymerization by jasplakinolide) of actin microfilaments was counteracted by cAMP. Both changes increased both phases of glucose- or tolbutamide-induced insulin secretion but did not prevent further amplification by cAMP. These large changes in secretion were not caused by changes in [Ca(2+)](c), which was only slightly increased by cAMP. Both phases of insulin secretion were larger in response to glucose than tolbutamide, although [Ca(2+)](c) was lower. This difference in secretion, which reflects metabolic amplification, was independent of microfilaments, was not attributable to differences in cAMP, and persisted in presence of dibutyryl-cAMP or when cAMP levels were variably raised by isobutylmethylxanthine + forskolin or glucagon-like peptide-1, 7-36 amide. We conclude that metabolic and cAMP-mediated amplification of insulin secretion are distinct pathways that accelerate acquisition of release competence by insulin granules that can access exocytotic sites without intervention of microfilaments.
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Affiliation(s)
- Nizar I Mourad
- Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, B-1200 Brussels, Belgium
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35
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Cai EP, Casimir M, Schroer SA, Luk CT, Shi SY, Choi D, Dai XQ, Hajmrle C, Spigelman AF, Zhu D, Gaisano HY, MacDonald PE, Woo M. In vivo role of focal adhesion kinase in regulating pancreatic β-cell mass and function through insulin signaling, actin dynamics, and granule trafficking. Diabetes 2012; 61:1708-18. [PMID: 22498697 PMCID: PMC3379666 DOI: 10.2337/db11-1344] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Focal adhesion kinase (FAK) acts as an adaptor at the focal contacts serving as a junction between the extracellular matrix and actin cytoskeleton. Actin dynamics is known as a determinant step in insulin secretion. Additionally, FAK has been shown to regulate insulin signaling. To investigate the essential physiological role of FAK in pancreatic β-cells in vivo, we generated a transgenic mouse model using rat insulin promoter (RIP)-driven Cre-loxP recombination system to specifically delete FAK in pancreatic β-cells. These RIPcre(+)fak(fl/fl) mice exhibited glucose intolerance without changes in insulin sensitivity. Reduced β-cell viability and proliferation resulting in decreased β-cell mass was observed in these mice, which was associated with attenuated insulin/Akt (also known as protein kinase B) and extracellular signal-related kinase 1/2 signaling and increased caspase 3 activation. FAK-deficient β-cells exhibited impaired insulin secretion with normal glucose sensing and preserved Ca(2+) influx in response to glucose, but a reduced number of docked insulin granules and insulin exocytosis were found, which was associated with a decrease in focal proteins, paxillin and talin, and an impairment in actin depolymerization. This study is the first to show in vivo that FAK is critical for pancreatic β-cell viability and function through regulation in insulin signaling, actin dynamics, and granule trafficking.
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Affiliation(s)
- Erica P. Cai
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
- Toronto General Research Institute, Toronto, Ontario, Canada
| | - Marina Casimir
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | | | - Cynthia T. Luk
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
- Toronto General Research Institute, Toronto, Ontario, Canada
| | - Sally Yu Shi
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
- Toronto General Research Institute, Toronto, Ontario, Canada
| | - Diana Choi
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Xiao Qing Dai
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Catherine Hajmrle
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Aliya F. Spigelman
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Dan Zhu
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Herbert Y. Gaisano
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Patrick E. MacDonald
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
- Corresponding author: Minna Woo, , or Patrick E. MacDonald,
| | - Minna Woo
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
- Toronto General Research Institute, Toronto, Ontario, Canada
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Medicine, St. Michael’s Hospital, Toronto, Ontario, Canada
- Corresponding author: Minna Woo, , or Patrick E. MacDonald,
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Abstract
Class II isoforms of PI3K (phosphoinositide 3-kinase) are still the least investigated and characterized of all PI3Ks. In the last few years, an increased interest in these enzymes has improved our understanding of their cellular functions. However, several questions still remain unanswered on their mechanisms of activation, their specific downstream effectors and their contribution to physiological processes and pathological conditions. Emerging evidence suggests that distinct PI3Ks activate different signalling pathways, indicating that their functional roles are probably not redundant. In the present review, we discuss the recent advances in our understanding of mammalian class II PI3Ks and the evidence suggesting their involvement in human diseases.
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DeSUMOylation Controls Insulin Exocytosis in Response to Metabolic Signals. Biomolecules 2012; 2:269-81. [PMID: 24970137 PMCID: PMC4030845 DOI: 10.3390/biom2020269] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Revised: 05/14/2012] [Accepted: 05/16/2012] [Indexed: 12/25/2022] Open
Abstract
The secretion of insulin by pancreatic islet β-cells plays a pivotal role in glucose homeostasis and diabetes. Recent work suggests an important role for SUMOylation in the control of insulin secretion from β-cells. In this paper we discuss mechanisms whereby (de)SUMOylation may control insulin release by modulating β-cell function at one or more key points; and particularly through the acute and reversible regulation of the exocytotic machinery. Furthermore, we postulate that the SUMO-specific protease SENP1 is an important mediator of insulin exocytosis in response to NADPH, a metabolic secretory signal and major determinant of β-cell redox state. Dialysis of mouse β-cells with NADPH efficiently amplifies β-cell exocytosis even when extracellular glucose is low; an effect that is lost upon knockdown of SENP1. Conversely, over-expression of SENP1 itself augments β-cell exocytosis in a redox-dependent manner. Taken together, we suggest that (de)SUMOylation represents an important mechanism that acutely regulates insulin secretion and that SENP1 can act as an amplifier of insulin exocytosis.
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Monet M, Francoeur N, Boulay G. Involvement of phosphoinositide 3-kinase and PTEN protein in mechanism of activation of TRPC6 protein in vascular smooth muscle cells. J Biol Chem 2012; 287:17672-17681. [PMID: 22493444 DOI: 10.1074/jbc.m112.341354] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPC6 is a cation channel in the plasma membrane that plays a role in Ca(2+) entry after the stimulation of a G(q)-protein-coupled or tyrosine-kinase receptor. TRPC6 translocates to the plasma membrane upon stimulation and remains there as long as the stimulus is present. However, the mechanism that regulates the trafficking and activation of TRPC6 are unclear. In this study we showed phosphoinositide 3-kinase and its antagonistic phosphatase, PTEN, are involved in the activation of TRPC6. The inhibition of PI3K by PIK-93, LY294002, or wortmannin decreased carbachol-induced translocation of TRPC6 to the plasma membrane and carbachol-induced net Ca(2+) entry into T6.11 cells. Conversely, a reduction of PTEN expression did not affect carbachol-induced externalization of TRPC6 but increased Ca(2+) entry through TRPC6 in T6.11 cells. We also showed that the PI3K/PTEN pathway regulates vasopressin-induced translocation of TRPC6 to the plasma membrane and vasopressin-induced Ca(2+) entry into A7r5 cells, which endogenously express TRPC6. In summary, we provided evidence that the PI3K/PTEN pathway plays an important role in the translocation of TRPC6 to the plasma membrane and may thus have a significant impact on Ca(2+) signaling in cells that endogenously express TRPC6.
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Affiliation(s)
- Michaël Monet
- Department of Pharmacology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Nancy Francoeur
- Department of Pharmacology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Guylain Boulay
- Department of Pharmacology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.
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Jou MY, Lönnerdal B, Philipps AF. Maternal zinc restriction affects postnatal growth and glucose homeostasis in rat offspring differently depending upon adequacy of their nutrient intake. Pediatr Res 2012; 71:228-34. [PMID: 22278188 DOI: 10.1038/pr.2011.44] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
INTRODUCTION We have previously investigated effects of moderate maternal zinc (Zn) restriction on growth and glucose homeostasis in offspring, but interaction between maternal Zn restriction and postnatal nutrition have not been studied. RESULTS Weight and serum Zn were lower in ZnD-IN than in ZnC-IN rats at wk 3, but ZnD-AN and ZnD-EN rats had greater weights than respective controls and higher insulin-like growth factor-1 (ZnD-AN) and leptin levels (ZnD-EN). Subsequently, both ZnD-AN and ZnD-EN pups were insulin resistant, and had evidence of elevated serum leptin and depressed insulin receptor phosphorylation with gender-specific differences up to 15 weeks. DISCUSSION Maternal Zn restriction interacted with postnatal nutritional status, resulting in divergent effects on weight gain and insulin resistance. Interaction between potential effects of fetal Zn restriction and food availability postnatally may be one factor responsible for later metabolic derangements. METHODS Rats were fed Zn restricted (ZnD, 7 μg/g) or control (ZnC, 25 μg/g) diets ad libitum from 3 wk pre-conception to 3 wk post-parturition. Postnatally, litters were culled to 13 (IN, inadequate nutrition), 7 (AN, adequate nutrition), and 4 (EN, excess nutrition) pups/dam, respectively, and nursed by their original mothers. Postweaning, pups were fed rodent diet ad libitum. Tests to assess insulin resistance were performed subsequently.
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Affiliation(s)
- Ming-Yu Jou
- Department of Nutrition, University of California, Davis, Davis, California, USA
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40
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Kruit JK, Wijesekara N, Fox JEM, Dai XQ, Brunham LR, Searle GJ, Morgan GP, Costin AJ, Tang R, Bhattacharjee A, Johnson JD, Light PE, Marsh BJ, MacDonald PE, Verchere CB, Hayden MR. Islet cholesterol accumulation due to loss of ABCA1 leads to impaired exocytosis of insulin granules. Diabetes 2011; 60:3186-96. [PMID: 21998401 PMCID: PMC3219942 DOI: 10.2337/db11-0081] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
OBJECTIVE The ATP-binding cassette transporter A1 (ABCA1) is essential for normal insulin secretion from β-cells. The aim of this study was to elucidate the mechanisms underlying the impaired insulin secretion in islets lacking β-cell ABCA1. RESEARCH DESIGN AND METHODS Calcium imaging, patch clamp, and membrane capacitance were used to assess the effect of ABCA1 deficiency on calcium flux, ion channel function, and exocytosis in islet cells. Electron microscopy was used to analyze β-cell ultrastructure. The quantity and distribution of proteins involved in insulin-granule exocytosis were also investigated. RESULTS We show that a lack of β-cell ABCA1 results in impaired depolarization-induced exocytotic fusion of insulin granules. We observed disturbances in membrane microdomain organization and Golgi and insulin granule morphology in β-cells as well as elevated fasting plasma proinsulin levels in mice in the absence of β-cell ABCA1. Acute cholesterol depletion rescued the exocytotic defect in β-cells lacking ABCA1, indicating that elevated islet cholesterol accumulation directly impairs granule fusion and insulin secretion. CONCLUSIONS Our data highlight a crucial role of ABCA1 and cellular cholesterol in β-cells that is necessary for regulated insulin granule fusion events. These data suggest that abnormalities of cholesterol metabolism may contribute to the impaired β-cell function in diabetes.
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Affiliation(s)
- Janine K. Kruit
- Departments of Medical Genetics, Centre for Molecular Medicine, and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Nadeeja Wijesekara
- Departments of Medical Genetics, Centre for Molecular Medicine, and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jocelyn E. Manning Fox
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Xiao-Qing Dai
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Liam R. Brunham
- Departments of Medical Genetics, Centre for Molecular Medicine, and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Gavin J. Searle
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Garry P. Morgan
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Adam J. Costin
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Renmei Tang
- Departments of Medical Genetics, Centre for Molecular Medicine, and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Alpana Bhattacharjee
- Departments of Medical Genetics, Centre for Molecular Medicine, and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - James D. Johnson
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Peter E. Light
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Brad J. Marsh
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Patrick E. MacDonald
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - C. Bruce Verchere
- Departments of Pathology & Laboratory Medicine and Surgery, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael R. Hayden
- Departments of Medical Genetics, Centre for Molecular Medicine, and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
- Corresponding author: Michael R. Hayden,
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41
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PI3Kγ within a nonhematopoietic cell type negatively regulates diet-induced thermogenesis and promotes obesity and insulin resistance. Proc Natl Acad Sci U S A 2011; 108:E854-63. [PMID: 21949398 DOI: 10.1073/pnas.1106698108] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Obesity is associated with a chronic low-grade inflammation, and specific antiinflammatory interventions may be beneficial for the treatment of type 2 diabetes and other obesity-related diseases. The lipid kinase PI3Kγ is a central proinflammatory signal transducer that plays a major role in leukocyte chemotaxis, mast cell degranulation, and endothelial cell activation. It was also reported that PI3Kγ activity within hematopoietic cells plays an important role in obesity-induced inflammation and insulin resistance. Here, we show that protection from insulin resistance, metabolic inflammation, and fatty liver in mice lacking functional PI3Kγ is largely consequent to their leaner phenotype. We also show that this phenotype is largely based on decreased fat gain, despite normal caloric intake, consequent to increased energy expenditure. Furthermore, our data show that PI3Kγ action on diet-induced obesity depends on PI3Kγ activity within a nonhematopoietic compartment, where it promotes energetic efficiency for fat mass gain. We also show that metabolic modulation by PI3Kγ depends on its lipid kinase activity and might involve kinase-independent signaling. Thus, PI3Kγ is an unexpected but promising drug target for the treatment of obesity and its complications.
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42
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Brown ACN, Oddos S, Dobbie IM, Alakoskela JM, Parton RM, Eissmann P, Neil MAA, Dunsby C, French PMW, Davis I, Davis DM. Remodelling of cortical actin where lytic granules dock at natural killer cell immune synapses revealed by super-resolution microscopy. PLoS Biol 2011; 9:e1001152. [PMID: 21931537 PMCID: PMC3172219 DOI: 10.1371/journal.pbio.1001152] [Citation(s) in RCA: 174] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 08/03/2011] [Indexed: 12/21/2022] Open
Abstract
Natural Killer (NK) cells are innate immune cells that secrete lytic granules to directly kill virus-infected or transformed cells across an immune synapse. However, a major gap in understanding this process is in establishing how lytic granules pass through the mesh of cortical actin known to underlie the NK cell membrane. Research has been hampered by the resolution of conventional light microscopy, which is too low to resolve cortical actin during lytic granule secretion. Here we use two high-resolution imaging techniques to probe the synaptic organisation of NK cell receptors and filamentous (F)-actin. A combination of optical tweezers and live cell confocal microscopy reveals that microclusters of NKG2D assemble into a ring-shaped structure at the centre of intercellular synapses, where Vav1 and Grb2 also accumulate. Within this ring-shaped organisation of NK cell proteins, lytic granules accumulate for secretion. Using 3D-structured illumination microscopy (3D-SIM) to gain super-resolution of ~100 nm, cortical actin was detected in a central region of the NK cell synapse irrespective of whether activating or inhibitory signals dominate. Strikingly, the periodicity of the cortical actin mesh increased in specific domains at the synapse when the NK cell was activated. Two-colour super-resolution imaging revealed that lytic granules docked precisely in these domains which were also proximal to where the microtubule-organising centre (MTOC) polarised. Together, these data demonstrate that remodelling of the cortical actin mesh occurs at the central region of the cytolytic NK cell immune synapse. This is likely to occur for other types of cell secretion and also emphasises the importance of emerging super-resolution imaging technology for revealing new biology.
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Affiliation(s)
- Alice C. N. Brown
- Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
| | - Stephane Oddos
- Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
| | - Ian M. Dobbie
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Juha-Matti Alakoskela
- Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
| | - Richard M. Parton
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Philipp Eissmann
- Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
| | - Mark A. A. Neil
- Department of Physics, Imperial College London, London, United Kingdom
| | | | - Paul M. W. French
- Department of Physics, Imperial College London, London, United Kingdom
| | - Ilan Davis
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Daniel M. Davis
- Division of Cell and Molecular Biology, Imperial College London, London, United Kingdom
- * E-mail:
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Mazza S, Maffucci T. Class II phosphoinositide 3-kinase C2alpha: what we learned so far. INTERNATIONAL JOURNAL OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2011; 2:168-182. [PMID: 21968800 PMCID: PMC3180093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 04/20/2011] [Indexed: 05/31/2023]
Abstract
More than fifteen years after the first identification of a class II isoform of phosphoinositide 3-kinase (PI3K) in Drosophila melanoǵaster this subfamily remains the most enigmatic among all PI3Ks. What are the functions of these enzymes? What are their mechanisms of activation? Which downstream effectors are specifically regulated by these isoforms? Are class I and class II PI3Ks redundant or do they control different intracellular processes? And, more important, do class II PI3Ks have a role in human diseases? The recent increased interest on class II PI3Ks has started providing some answers to these questions but still a lot needs to be done to completely uncover the contribution of these enzymes to physiological processes and possibly to pathological conditions. Here we will summarise the recent findings on the alpha isoform of mammalian class II PI3Ks (PI3K-C2α ) and we will discuss the potential involvement of this enzyme in human diseases.
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Affiliation(s)
- Simona Mazza
- Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Blizard Institute of Cell and Molecular Science, Centre for Diabetes Inositide Signalling Group, London El 2AT UK
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Ata H, Rawat DK, Lincoln T, Gupte SA. Mechanism of glucose-6-phosphate dehydrogenase-mediated regulation of coronary artery contractility. Am J Physiol Heart Circ Physiol 2011; 300:H2054-63. [PMID: 21398595 DOI: 10.1152/ajpheart.01155.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We previously identified glucose-6-phosphate dehydrogenase (G6PD) as a regulator of vascular smooth muscle contraction. In this study, we tested our hypothesis that G6PD activated by KCl via a phosphatase and tensin homologue deleted on chromosome 10 (PTEN)-protein kinase C (PKC) pathway increases vascular smooth muscle contraction and that inhibition of G6PD relaxes smooth muscle by decreasing intracellular Ca(2+) ([Ca(2+)](i)) and Ca(2+) sensitivity to the myofilament. Here we show that G6PD is activated by membrane depolarization via PKC and PTEN pathway and that G6PD inhibition decreases intracellular free calcium ([Ca(2+)](i)) in vascular smooth muscle cells and thus arterial contractility. In bovine coronary artery (CA), KCl (30 mmol/l) increased PKC activity and doubled G6PD V(max) without affecting K(m). KCl-induced PKC and G6PD activation was inhibited by bisperoxo(pyridine-2-carboxyl)oxovanadate (Bpv; 10 μmol/l), a PTEN inhibitor, which also inhibited (P < 0.05) KCl-induced CA contraction. The G6PD blockers 6-aminonicotinamide (6AN; 1 mmol/l) and epiandrosterone (EPI; 100 μmol/l) inhibited KCl-induced increases in G6PD activity, [Ca(2+)](i), Ca(2+)-dependent myosin light chain (MLC) phosphorylation, and contraction. Relaxation of precontracted CA by 6AN and EPI was not blocked by calnoxin (10 μmol/l), a plasma membrane Ca(2+) ATPase inhibitor or by lowering extracellular Na(+), which inhibits the Na(+)/Ca(2+) exchanger (NCX), but cyclopiazonic acid (200 μmol/l), a sarcoplasmic reticulum Ca(2+) ATPase inhibitor, reduced (P < 0.05) 6AN- and EPI-induced relaxation. 6AN also attenuated phosphorylation of myosin phosphatase target subunit 1 (MYPT1) at Ser855, a site phosphorylated by Rho kinase, inhibition of which reduced (P < 0.05) KCl-induced CA contraction and 6AN-induced relaxation. By contrast, 6AN increased (P < 0.05) vasodilator-stimulated phosphoprotein (VASP) phosphorylation at Ser239, indicating that inhibition of G6PD increases PKA or PKG activity. Inhibition of PKG by RT-8-Br-PET-cGMPs (100 nmol/l) diminished 6AN-evoked VASP phosphorylation (P < 0.05), but RT-8-Br-PET-cGMPs increased 6AN-induced relaxation. These findings suggest G6PD inhibition relaxes CA by decreasing Ca(2+) influx, increasing Ca(2+) sequestration, and inhibiting Rho kinase but not by increasing Ca(2+) extrusion or activating PKG.
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Affiliation(s)
- Hirotaka Ata
- Biochemistry & Molecular Biology, MSB 2312, Univ. of South Alabama, College of Medicine, 307 N Univ. Blvd., Mobile, AL 36688, USA
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45
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Dai XQ, Plummer G, Casimir M, Kang Y, Hajmrle C, Gaisano HY, Manning Fox JE, MacDonald PE. SUMOylation regulates insulin exocytosis downstream of secretory granule docking in rodents and humans. Diabetes 2011; 60:838-47. [PMID: 21266332 PMCID: PMC3046844 DOI: 10.2337/db10-0440] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
OBJECTIVE The reversible attachment of small ubiquitin-like modifier (SUMO) proteins controls target localization and function. We examined an acute role for the SUMOylation pathway in downstream events mediating insulin secretion. RESEARCH DESIGN AND METHODS We studied islets and β-cells from mice and human donors, as well as INS-1 832/13 cells. Insulin secretion, intracellular Ca(2+), and β-cell exocytosis were monitored after manipulation of the SUMOylation machinery. Granule localization was imaged by total internal reflection fluorescence and electron microscopy; immunoprecipitation and Western blotting were used to examine the soluble NSF attachment receptor (SNARE) complex formation and SUMO1 interaction with synaptotagmin VII. RESULTS SUMO1 impairs glucose-stimulated insulin secretion by blunting the β-cell exocytotic response to Ca(2+). The effect of SUMO1 to impair insulin secretion and β-cell exocytosis is rapid and does not require altered gene expression or insulin content, is downstream of granule docking at the plasma membrane, and is dependent on SUMO-conjugation because the deSUMOylating enzyme, sentrin/SUMO-specific protease (SENP)-1, rescues exocytosis. SUMO1 coimmunoprecipitates with the Ca(2+) sensor synaptotagmin VII, and this is transiently lost upon glucose stimulation. SENP1 overexpression also disrupts the association of SUMO1 with synaptotagmin VII and mimics the effect of glucose to enhance exocytosis. Conversely, SENP1 knockdown impairs exocytosis at stimulatory glucose levels and blunts glucose-dependent insulin secretion from mouse and human islets. CONCLUSIONS SUMOylation acutely regulates insulin secretion by the direct and reversible inhibition of β-cell exocytosis in response to intracellular Ca(2+) elevation. The SUMO protease, SENP1, is required for glucose-dependent insulin secretion.
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Affiliation(s)
- Xiao-Qing Dai
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Greg Plummer
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Marina Casimir
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Youhou Kang
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Catherine Hajmrle
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | | | - Jocelyn E. Manning Fox
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Patrick E. MacDonald
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
- Corresponding author: Patrick E. MacDonald,
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46
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Geng X, Lou H, Wang J, Li L, Swanson AL, Sun M, Beers-Stolz D, Watkins S, Perez RG, Drain P. α-Synuclein binds the K(ATP) channel at insulin-secretory granules and inhibits insulin secretion. Am J Physiol Endocrinol Metab 2011; 300:E276-86. [PMID: 20858756 PMCID: PMC4459921 DOI: 10.1152/ajpendo.00262.2010] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
α-Synuclein has been studied in numerous cell types often associated with secretory processes. In pancreatic β-cells, α-synuclein might therefore play a similar role by interacting with organelles involved in insulin secretion. We tested for α-synuclein localizing to insulin-secretory granules and characterized its role in glucose-stimulated insulin secretion. Immunohistochemistry and fluorescent sulfonylureas were used to test for α-synuclein localization to insulin granules in β-cells, immunoprecipitation with Western blot analysis for interaction between α-synuclein and K(ATP) channels, and ELISA assays for the effect of altering α-synuclein expression up or down on insulin secretion in INS1 cells or mouse islets, respectively. Differences in cellular phenotype between α-synuclein knockout and wild-type β-cells were found by using confocal microscopy to image the fluorescent insulin biosensor Ins-C-emGFP and by using transmission electron microscopy. The results show that anti-α-synuclein antibodies labeled secretory organelles within β-cells. Anti-α-synuclein antibodies colocalized with K(ATP) channel, anti-insulin, and anti-C-peptide antibodies. α-Synuclein coimmunoprecipitated in complexes with K(ATP) channels. Expression of α-synuclein downregulated insulin secretion at 2.8 mM glucose with little effect following 16.7 mM glucose stimulation. α-Synuclein knockout islets upregulated insulin secretion at 2.8 and 8.4 mM but not 16.7 mM glucose, consistent with the depleted insulin granule density at the β-cell surface membranes observed in these islets. These findings demonstrate that α-synuclein interacts with K(ATP) channels and insulin-secretory granules and functionally acts as a brake on secretion that glucose stimulation can override. α-Synuclein might play similar roles in diabetes as it does in other degenerative diseases, including Alzheimer's and Parkinson's diseases.
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Affiliation(s)
- Xuehui Geng
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pennsylvania, USA
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47
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Dominguez V, Raimondi C, Somanath S, Bugliani M, Loder MK, Edling CE, Divecha N, da Silva-Xavier G, Marselli L, Persaud SJ, Turner MD, Rutter GA, Marchetti P, Falasca M, Maffucci T. Class II phosphoinositide 3-kinase regulates exocytosis of insulin granules in pancreatic beta cells. J Biol Chem 2010; 286:4216-25. [PMID: 21127054 PMCID: PMC3039383 DOI: 10.1074/jbc.m110.200295] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Phosphoinositide 3-kinases (PI3Ks) are critical regulators of pancreatic β cell mass and survival, whereas their involvement in insulin secretion is more controversial. Furthermore, of the different PI3Ks, the class II isoforms were detected in β cells, although their role is still not well understood. Here we show that down-regulation of the class II PI3K isoform PI3K-C2α specifically impairs insulin granule exocytosis in rat insulinoma cells without affecting insulin content, the number of insulin granules at the plasma membrane, or the expression levels of key proteins involved in insulin secretion. Proteolysis of synaptosomal-associated protein of 25 kDa, a process involved in insulin granule exocytosis, is impaired in cells lacking PI3K-C2α. Finally, our data suggest that the mRNA for PI3K-C2α may be down-regulated in islets of Langerhans from type 2 diabetic compared with non-diabetic individuals. Our results reveal a critical role for PI3K-C2α in β cells and suggest that down-regulation of PI3K-C2α may be a feature of type 2 diabetes.
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Affiliation(s)
- Veronica Dominguez
- From the Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Blizard Institute of Cell and Molecular Science, Centre for Diabetes, London E1 2AT, United Kingdom
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48
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Wong VSC, Yeung A, Schultz W, Brubaker PL. R-spondin-1 is a novel beta-cell growth factor and insulin secretagogue. J Biol Chem 2010; 285:21292-302. [PMID: 20442404 PMCID: PMC2898385 DOI: 10.1074/jbc.m110.129874] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Indexed: 12/13/2022] Open
Abstract
R-spondin-1 (Rspo1) is an intestinal growth factor known to exert its effects through activation of the canonical Wnt (cWnt) signaling pathway and subsequent expression of cWnt target genes. We have detected Rspo1 mRNA in murine islets and the murine MIN6 and betaTC beta-cell lines, and Rspo1 protein in MIN6 beta-cells. Rspo1 activated cWnt signaling in MIN6 beta-cells by increasing nuclear beta-catenin and c-myc, a cWnt target gene. Rspo1 also induced insulin mRNA expression in MIN6 cells. Analysis of MIN6 and mouse beta-cell proliferation by [(3)H]thymidine and BrdU incorporation, respectively, revealed that Rspo1 stimulated cell growth. Incubation of MIN6 and mouse beta-cells with cytokines (IL1beta/TNFalpha/interferon-gamma) significantly increased cellular apoptosis; this increase was abolished by pretreatment with Rspo1. Rspo1 also stimulated insulin secretion in a glucose-independent fashion. We further demonstrated that the glucagon-like peptide-1 receptor agonist, exendin4 (EX4), stimulated Rspo1 mRNA transcript levels in MIN6 cells in a glucose-, time-, dose-, and PI3-kinase-dependent fashion. This effect was not limited to this beta-cell line, as similar time-dependent increases in Rspo1 were also observed in the betaTC beta-cell line and mouse islets in response to EX4 treatment. Together, these studies demonstrate that Rspo1 is a novel beta-cell growth factor and insulin secretagogue that is regulated by EX4. These findings suggest that Rspo1 and the cWnt signaling pathway may serve as a novel target to enhance beta-cell growth and function in patients with type 2 diabetes.
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Affiliation(s)
| | | | | | - Patricia L. Brubaker
- From the Departments of Physiology and
- Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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Hamming KS, Soliman D, Webster NJ, Searle GJ, Matemisz LC, Liknes DA, Dai XQ, Pulinilkunnil T, Riedel MJ, Dyck JR, MacDonald PE, Light PE. Inhibition of beta-cell sodium-calcium exchange enhances glucose-dependent elevations in cytoplasmic calcium and insulin secretion. Diabetes 2010; 59:1686-93. [PMID: 20413506 PMCID: PMC2889768 DOI: 10.2337/db09-0630] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVE The sodium-calcium exchanger isoform 1 (NCX1) regulates cytoplasmic calcium (Ca(2+)(c)) required for insulin secretion in beta-cells. NCX1 is alternatively spliced, resulting in the expression of splice variants in different tissues such as NCX1.3 and -1.7 in beta-cells. As pharmacological inhibitors of NCX1 splice variants are in development, the pharmacological profile of beta-cell NCX1.3 and -1.7 and the cellular effects of NCX1 inhibition were investigated. RESEARCH DESIGN AND METHODS The patch-clamp technique was used to examine the pharmacological profile of the NCX1 inhibitor KB-R7943 on recombinant NCX1.3 and -1.7 activity. Ca(2+) imaging and membrane capacitance were used to assess the effects of KB-R7943 on Ca(2+)(c) and insulin secretion in mouse and human beta-cells and islets. RESULTS NCX1.3 and -1.7 calcium extrusion (forward-mode) activity was approximately 16-fold more sensitive to KB-R7943 inhibition compared with cardiac NCX1.1 (IC(50s) = 2.9 and 2.4 vs. 43.0 micromol/l, respectively). In single mouse/human beta-cells, 1 micromol/l KB-R7943 increased insulin granule exocytosis but was without effect on alpha-cell glucagon granule exocytosis. KB-R7943 also augmented sulfonylurea and glucose-stimulated Ca(2+)(c) levels and insulin secretion in mouse and human islets, although KB-R7943 was without effect under nonstimulated conditions. CONCLUSIONS Islet NCX1 splice variants display a markedly greater sensitivity to pharmacological inhibition than the cardiac NCX1.1 splice variant. NCX1 inhibition resulted in glucose-dependent increases in Ca(2+)(c) and insulin secretion in mouse and human islets. Thus, we identify beta-cell NCX1 splice variants as targets for the development of novel glucose-sensitive insulinotropic drugs for type 2 diabetes.
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Affiliation(s)
- Kevin S.C. Hamming
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Daniel Soliman
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Nicola J. Webster
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Gavin J. Searle
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Laura C. Matemisz
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - David A. Liknes
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Xiao-Qing Dai
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Thomas Pulinilkunnil
- Department of Pediatrics, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Michael J. Riedel
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Jason R.B. Dyck
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Department of Pediatrics, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Patrick E. MacDonald
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Peter E. Light
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Corresponding author: Peter E. Light,
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Surface analysis of membrane dynamics. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:766-76. [DOI: 10.1016/j.bbamem.2009.09.016] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 09/18/2009] [Accepted: 09/20/2009] [Indexed: 11/18/2022]
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