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Yoo YM, Joo SS. Serotonin Influences Insulin Secretion in Rat Insulinoma INS-1E Cells. Int J Mol Sci 2024; 25:6828. [PMID: 38999937 PMCID: PMC11241493 DOI: 10.3390/ijms25136828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Revised: 06/15/2024] [Accepted: 06/19/2024] [Indexed: 07/14/2024] Open
Abstract
Serotonin or 5-hydroxytryptamine (5-HT) is a monoamine that plays a critical role in insulin secretion, energy metabolism, and mitochondrial biogenesis. However, the action of serotonin in insulin production and secretion by pancreatic β cells has not yet been elucidated. Here, we investigated how exogenous nanomolar serotonin concentrations regulate insulin synthesis and secretion in rat insulinoma INS-1E cells. Nanomolar serotonin concentrations (10 and 50 nM) significantly increased insulin protein expression above the constant levels in untreated control cells and decreased insulin protein levels in the media. The reductions in insulin protein levels in the media may be associated with ubiquitin-mediated protein degradation. The levels of membrane vesicle trafficking-related proteins including Rab5, Rab3A, syntaxin6, clathrin, and EEA1 proteins were significantly decreased by serotonin treatment compared to the untreated control cells, whereas the expressions of Rab27A, GOPC, and p-caveolin-1 proteins were significantly reduced by serotonin treatment. In this condition, serotonin receptors, Gαq-coupled 5-HT2b receptor (Htr2b), and ligand-gated ion channel receptor Htr3a were significantly decreased by serotonin treatment. To confirm the serotonylation of Rab3A and Rab27A during insulin secretion, we investigated the protein levels of Rab3A and Rab27A, in which transglutaminase 2 (TGase2) serotonylated Rab3A but not Rab27A. The increases in ERK phosphorylation levels were consistent with increases in the expression of p-Akt. Also, the expression level of the Bcl-2 protein was significantly increased by 50 and 100 nM serotonin treatment compared to the untreated control cells, whereas the levels of Cu/Zn-SOD and Mn-SOD proteins decreased. These results indicate that nanomolar serotonin treatment regulates the insulin protein level but decreases this level in media through membrane vesicle trafficking-related proteins (Rab5, Rab3A, syntaxin6, clathrin, and EEA1), the Akt/ERK pathway, and Htr2b/Htr3a in INS-1E cells.
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Affiliation(s)
- Yeong-Min Yoo
- East Coast Life Sciences Institute, College of Life Science, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea
- Department of Marine Bioscience, College of Life Science, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea
| | - Seong Soo Joo
- Department of Marine Bioscience, College of Life Science, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea
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2
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Pulli K, Saarimäki-Vire J, Ahonen P, Liu X, Ibrahim H, Chandra V, Santambrogio A, Wang Y, Vaaralahti K, Iivonen AP, Känsäkoski J, Tommiska J, Kemkem Y, Varjosalo M, Vuoristo S, Andoniadou CL, Otonkoski T, Raivio T. A splice site variant in MADD affects hormone expression in pancreatic β cells and pituitary gonadotropes. JCI Insight 2024; 9:e167598. [PMID: 38775154 PMCID: PMC11141940 DOI: 10.1172/jci.insight.167598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 04/12/2024] [Indexed: 06/02/2024] Open
Abstract
MAPK activating death domain (MADD) is a multifunctional protein regulating small GTPases RAB3 and RAB27, MAPK signaling, and cell survival. Polymorphisms in the MADD locus are associated with glycemic traits, but patients with biallelic variants in MADD manifest a complex syndrome affecting nervous, endocrine, exocrine, and hematological systems. We identified a homozygous splice site variant in MADD in 2 siblings with developmental delay, diabetes, congenital hypogonadotropic hypogonadism, and growth hormone deficiency. This variant led to skipping of exon 30 and in-frame deletion of 36 amino acids. To elucidate how this mutation causes pleiotropic endocrine phenotypes, we generated relevant cellular models with deletion of MADD exon 30 (dex30). We observed reduced numbers of β cells, decreased insulin content, and increased proinsulin-to-insulin ratio in dex30 human embryonic stem cell-derived pancreatic islets. Concordantly, dex30 led to decreased insulin expression in human β cell line EndoC-βH1. Furthermore, dex30 resulted in decreased luteinizing hormone expression in mouse pituitary gonadotrope cell line LβT2 but did not affect ontogeny of stem cell-derived GnRH neurons. Protein-protein interactions of wild-type and dex30 MADD revealed changes affecting multiple signaling pathways, while the GDP/GTP exchange activity of dex30 MADD remained intact. Our results suggest MADD-specific processes regulate hormone expression in pancreatic β cells and pituitary gonadotropes.
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Affiliation(s)
- Kristiina Pulli
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Jonna Saarimäki-Vire
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Pekka Ahonen
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Xiaonan Liu
- Institute of Biotechnology, Helsinki Institute of Life Science (HiLIFE), University of Helsinki, Helsinki, Finland
| | - Hazem Ibrahim
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Vikash Chandra
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Alice Santambrogio
- Centre for Craniofacial and Regenerative Biology, King’s College London, London, United Kingdom
- Department of Medicine III, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Yafei Wang
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Kirsi Vaaralahti
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Anna-Pauliina Iivonen
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
| | - Johanna Känsäkoski
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- Department of Physiology, Faculty of Medicine
| | - Johanna Tommiska
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- Department of Physiology, Faculty of Medicine
| | - Yasmine Kemkem
- Centre for Craniofacial and Regenerative Biology, King’s College London, London, United Kingdom
| | - Markku Varjosalo
- Institute of Biotechnology, Helsinki Institute of Life Science (HiLIFE), University of Helsinki, Helsinki, Finland
| | - Sanna Vuoristo
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- Department of Obstetrics and Gynecology; and
- HiLIFE, University of Helsinki, Helsinki, Finland
| | - Cynthia L. Andoniadou
- Centre for Craniofacial and Regenerative Biology, King’s College London, London, United Kingdom
- Department of Medicine III, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Timo Otonkoski
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- New Children’s Hospital, Helsinki University Hospital, Pediatric Research Center, Helsinki, Finland
| | - Taneli Raivio
- Stem Cells and Metabolism Research Program (STEMM), Research Programs Unit, Faculty of Medicine, and
- Department of Physiology, Faculty of Medicine
- New Children’s Hospital, Helsinki University Hospital, Pediatric Research Center, Helsinki, Finland
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3
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Kodera S, Kimura T, Nishioka T, Kaneko YK, Yamaguchi M, Kaibuchi K, Ishikawa T. GDP-bound Rab27a regulates clathrin disassembly through HSPA8 after insulin secretion. Arch Biochem Biophys 2023; 749:109789. [PMID: 37852426 DOI: 10.1016/j.abb.2023.109789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 10/12/2023] [Accepted: 10/15/2023] [Indexed: 10/20/2023]
Abstract
Clathrin-dependent endocytosis is a key process for secretory cells, in which molecules on the plasma membrane are both degraded and recycled in a stimulus-dependent manner. There are many reports showing that disruption of endocytosis is involved in the onset of various diseases. Recently, it has been reported that such disruption in pancreatic β-cells causes impaired insulin secretion and might be associated with the pathology of diabetes mellitus. Compared with exocytosis, there are few reports on the molecular mechanism of endocytosis in pancreatic β-cells. We previously reported that GDP-bound Rab27a regulates endocytosis through its GDP-dependent effectors after insulin secretion. In this study, we identified heat shock protein family A member 8 (HSPA8) as a novel interacting protein for GDP-bound Rab27a. HSPA8 directly bound GDP-bound Rab27a via the β2 region of its substrate binding domain (SBD). The β2 fragment was capable of inhibiting the interaction between HSPA8 and GDP-bound Rab27a, and suppressed glucose-induced clathrin-dependent endocytosis in pancreatic β-cells. The region also affected clathrin dynamics on purified clathrin-coated vesicles (CCVs). These results suggest that the interaction between GDP-bound Rab27a and HSPA8 regulates clathrin disassembly from CCVs and subsequent vesicle transport. The regulatory stages in endocytosis by HSPA8 differ from those for other GDP-bound Rab27a effectors. This study shows that GDP-bound Rab27a dominantly regulates each stage in glucose-induced endocytosis through its specific effectors in pancreatic β-cells.
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Affiliation(s)
- Soshiro Kodera
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan
| | - Toshihide Kimura
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan.
| | - Tomoki Nishioka
- Division of Cell Biology, International Center for Brain Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake City, Aichi, 470-1192, Japan
| | - Yukiko K Kaneko
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan
| | - Momoka Yamaguchi
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan
| | - Kozo Kaibuchi
- Division of Cell Biology, International Center for Brain Science, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake City, Aichi, 470-1192, Japan
| | - Tomohisa Ishikawa
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka City, Shizuoka, 422-8526, Japan
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Taguchi T, Duan W, Wolfson W, Duhon B, Halphen EG, Lopez MJ. Feline Adipose Derived Multipotent Stromal Cell Transdifferentiation Into Functional Insulin Producing Cell Clusters. Front Bioeng Biotechnol 2022; 10:904519. [PMID: 35769100 PMCID: PMC9234738 DOI: 10.3389/fbioe.2022.904519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 05/10/2022] [Indexed: 11/22/2022] Open
Abstract
Diabetes mellitus (DM) is one of the most prevalent feline endocrinopathies, affecting up to 1% of pet cats. De novo generation of functional insulin producing cell (IPC) clusters via transdifferentiation of feline adipose-derived multipotent stromal cells (ASCs) may not only provide a viable, functional cell therapy for feline DM, but may also serve as a platform for developing a comparable human treatment given feline and human DM similarities. Cells were induced to form IPCs with a novel, three-stage culture process with stromal or differentiation medium under static and dynamic conditions. Clusters were evaluated for intracellular zinc, viability, intracellular insulin, glucagon, and somatostatin, ultrastructure, glucose stimulated insulin secretion in the presence or absence of theophylline, and protein and gene expression. Isolated cells were multipotent, and cell clusters cultured in both media had robust cell viability. Those cultured in differentiation medium contained zinc and mono- or polyhormonal α-, β-, and δ-like cells based on immunohistochemical labeling and Mallory-Heidenhan Azan-Gomori’s staining. Ultrastructurally, cell clusters cultured in differentiation medium contained insulin granules within vesicles, and clusters had a concentration-dependent insulin response to glucose in the presence and absence of theophylline which increased both insulin secretion and intracellular content. Expression of NK6.1, Pax6, Isl1, Glut2, RAB3A, glucagon, insulin, and somatostatin increased with differentiation stage for both sexes, and expression of nestin at stages 1 and 2 and Neurod1 at stage 2 was higher in cells from female donors. The cluster insulin secretion responses and endocrine and oncogene gene expression profiles were inconsistent with insulinoma characteristics. A total of 180 proteins were upregulated in differentiated clusters, and the majority were associated with biological regulation, metabolic processes, or stimulus response. Dynamic culture of IPC clusters resulted in clusters composed of cells primarily expressing insulin that released higher insulin with glucose stimulation than those in static culture. Collectively, the results of this study support generation of functional IPC clusters using feline ASCs isolated from tissues removed during routine sterilization. Further, cluster functionality is enhanced with dynamic, motion-driven shear stress. This work establishes a foundation for development of strategies for IPC therapy for short or long-term diabetes treatment and may represent an option to study prevention and treatment of diabetes across species.
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Affiliation(s)
- Takashi Taguchi
- Laboratory for Equine and Comparative Orthopedic Research, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
| | - Wei Duan
- Laboratory for Equine and Comparative Orthopedic Research, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
| | - Wendy Wolfson
- Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
| | - Brandy Duhon
- Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
| | - Emily G. Halphen
- Laboratory for Equine and Comparative Orthopedic Research, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
| | - Mandi J. Lopez
- Laboratory for Equine and Comparative Orthopedic Research, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, United States
- *Correspondence: Mandi J. Lopez,
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Ham H, Medlyn M, Billadeau DD. Locked and Loaded: Mechanisms Regulating Natural Killer Cell Lytic Granule Biogenesis and Release. Front Immunol 2022; 13:871106. [PMID: 35558071 PMCID: PMC9088006 DOI: 10.3389/fimmu.2022.871106] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 03/29/2022] [Indexed: 11/22/2022] Open
Abstract
NK cell-mediated cytotoxicity is a critical element of our immune system required for protection from microbial infections and cancer. NK cells bind to and eliminate infected or cancerous cells via direct secretion of cytotoxic molecules toward the bound target cells. In this review, we summarize the current understanding of the molecular regulations of NK cell cytotoxicity, focusing on lytic granule development and degranulation processes. NK cells synthesize apoptosis-inducing proteins and package them into specialized organelles known as lytic granules (LGs). Upon activation of NK cells, LGs converge with the microtubule organizing center through dynein-dependent movement along microtubules, ultimately polarizing to the cytotoxic synapse where they subsequently fuse with the NK plasma membrane. From LGs biogenesis to degranulation, NK cells utilize several strategies to protect themselves from their own cytotoxic molecules. Additionally, molecular pathways that enable NK cells to perform serial killing are beginning to be elucidated. These advances in the understanding of the molecular pathways behind NK cell cytotoxicity will be important to not only improve current NK cell-based anti-cancer therapies but also to support the discovery of additional therapeutic opportunities.
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Affiliation(s)
- Hyoungjun Ham
- Division of Oncology Research, Mayo Clinic, Rochester, MN, United States
| | - Michael Medlyn
- Department of Immunology College of Medicine, Mayo Clinic, Rochester, MN, United States
| | - Daniel D Billadeau
- Division of Oncology Research, Mayo Clinic, Rochester, MN, United States.,Department of Immunology College of Medicine, Mayo Clinic, Rochester, MN, United States
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Izumi T. In vivo Roles of Rab27 and Its Effectors in Exocytosis. Cell Struct Funct 2021; 46:79-94. [PMID: 34483204 PMCID: PMC10511049 DOI: 10.1247/csf.21043] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 08/31/2021] [Indexed: 11/11/2022] Open
Abstract
The monomeric GTPase Rab27 regulates exocytosis of a broad range of vesicles in multicellular organisms. Several effectors bind GTP-bound Rab27a and/or Rab27b on secretory vesicles to execute a series of exocytic steps, such as vesicle maturation, movement along microtubules, anchoring within the peripheral F-actin network, and tethering to the plasma membrane, via interactions with specific proteins and membrane lipids in a local milieu. Although Rab27 effectors generally promote exocytosis, they can also temporarily restrict it when they are involved in the rate-limiting step. Genetic alterations in Rab27-related molecules cause discrete diseases manifesting pigment dilution and immunodeficiency, and can also affect common diseases such as diabetes and cancer in complex ways. Although the function and mechanism of action of these effectors have been explored, it is unclear how multiple effectors act in coordination within a cell to regulate the secretory process as a whole. It seems that Rab27 and various effectors constitutively reside on individual vesicles to perform consecutive exocytic steps. The present review describes the unique properties and in vivo roles of the Rab27 system, and the functional relationship among different effectors coexpressed in single cells, with pancreatic beta cells used as an example.Key words: membrane trafficking, regulated exocytosis, insulin granules, pancreatic beta cells.
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Affiliation(s)
- Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
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7
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Zhao MM, Lu J, Li S, Wang H, Cao X, Li Q, Shi TT, Matsunaga K, Chen C, Huang H, Izumi T, Yang JK. Berberine is an insulin secretagogue targeting the KCNH6 potassium channel. Nat Commun 2021; 12:5616. [PMID: 34556670 PMCID: PMC8460738 DOI: 10.1038/s41467-021-25952-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 09/08/2021] [Indexed: 11/09/2022] Open
Abstract
Coptis chinensis is an ancient Chinese herb treating diabetes in China for thousands of years. However, its underlying mechanism remains poorly understood. Here, we report the effects of its main active component, berberine (BBR), on stimulating insulin secretion. In mice with hyperglycemia induced by a high-fat diet, BBR significantly increases insulin secretion and reduced blood glucose levels. However, in mice with hyperglycemia induced by global or pancreatic islet β-cell-specific Kcnh6 knockout, BBR does not exert beneficial effects. BBR directly binds KCNH6 potassium channels, significantly accelerates channel closure, and subsequently reduces KCNH6 currents. Consequently, blocking KCNH6 currents prolongs high glucose-dependent cell membrane depolarization and increases insulin secretion. Finally, to assess the effect of BBR on insulin secretion in humans, a randomized, double-blind, placebo-controlled, two-period crossover, single-dose, phase 1 clinical trial (NCT03972215) including 15 healthy men receiving a 160-min hyperglycemic clamp experiment is performed. The pre-specified primary outcomes are assessment of the differences of serum insulin and C-peptide levels between BBR and placebo treatment groups during the hyperglycemic clamp study. BBR significantly promotes insulin secretion under hyperglycemic state comparing with placebo treatment, while does not affect basal insulin secretion in humans. All subjects tolerate BBR well, and we observe no side effects in the 14-day follow up period. In this study, we identify BBR as a glucose-dependent insulin secretagogue for treating diabetes without causing hypoglycemia that targets KCNH6 channels.
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Affiliation(s)
- Miao-Miao Zhao
- Department of Endocrinology, Beijing Tongren Hospital, Capital Medical University, 100730, Beijing, China
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, 100730, Beijing, China
| | - Jing Lu
- Department of Endocrinology, Beijing Tongren Hospital, Capital Medical University, 100730, Beijing, China
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, 100730, Beijing, China
| | - Sen Li
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, 100730, Beijing, China
| | - Hao Wang
- Department of Endocrinology, Beijing Tongren Hospital, Capital Medical University, 100730, Beijing, China
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, 100730, Beijing, China
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Xi Cao
- Department of Endocrinology, Beijing Tongren Hospital, Capital Medical University, 100730, Beijing, China
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, 100730, Beijing, China
| | - Qi Li
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, 100730, Beijing, China
| | - Ting-Ting Shi
- Department of Endocrinology, Beijing Tongren Hospital, Capital Medical University, 100730, Beijing, China
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, 100730, Beijing, China
| | - Kohichi Matsunaga
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Chen Chen
- School of Biomedical Sciences, University of Queensland, Brisbane, QLD, 4072, Australia
| | - Haixia Huang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, 100069, Beijing, China
| | - Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Jin-Kui Yang
- Department of Endocrinology, Beijing Tongren Hospital, Capital Medical University, 100730, Beijing, China.
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, 100730, Beijing, China.
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Veluthakal R, Thurmond DC. Emerging Roles of Small GTPases in Islet β-Cell Function. Cells 2021; 10:1503. [PMID: 34203728 PMCID: PMC8232272 DOI: 10.3390/cells10061503] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 06/08/2021] [Accepted: 06/08/2021] [Indexed: 12/16/2022] Open
Abstract
Several small guanosine triphosphatases (GTPases) from the Ras protein superfamily regulate glucose-stimulated insulin secretion in the pancreatic islet β-cell. The Rho family GTPases Cdc42 and Rac1 are primarily involved in relaying key signals in several cellular functions, including vesicle trafficking, plasma membrane homeostasis, and cytoskeletal dynamics. They orchestrate specific changes at each spatiotemporal region within the β-cell by coordinating with signal transducers, guanine nucleotide exchange factors (GEFs), GTPase-activating factors (GAPs), and their effectors. The Arf family of small GTPases is involved in vesicular trafficking (exocytosis and endocytosis) and actin cytoskeletal dynamics. Rab-GTPases regulate pre-exocytotic and late endocytic membrane trafficking events in β-cells. Several additional functions for small GTPases include regulating transcription factor activity and mitochondrial dynamics. Importantly, defects in several of these GTPases have been found associated with type 2 diabetes (T2D) etiology. The purpose of this review is to systematically denote the identities and molecular mechanistic steps in the glucose-stimulated insulin secretion pathway that leads to the normal release of insulin. We will also note newly identified defects in these GTPases and their corresponding regulatory factors (e.g., GDP dissociation inhibitors (GDIs), GEFs, and GAPs) in the pancreatic β-cells, which contribute to the dysregulation of metabolism and the development of T2D.
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Affiliation(s)
- Rajakrishnan Veluthakal
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes & Metabolism Research Institute, City of Hope Beckman Research Institute, Duarte, CA 91010, USA
| | - Debbie C. Thurmond
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes & Metabolism Research Institute, City of Hope Beckman Research Institute, Duarte, CA 91010, USA
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Tokuo H, Komaba S, Coluccio LM. In pancreatic β-cells myosin 1b regulates glucose-stimulated insulin secretion by modulating an early step in insulin granule trafficking from the Golgi. Mol Biol Cell 2021; 32:1210-1220. [PMID: 33826361 PMCID: PMC8351557 DOI: 10.1091/mbc.e21-03-0094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Pancreatic β-cells secrete insulin, which controls blood glucose levels, and defects in insulin secretion are responsible for diabetes mellitus. The actin cytoskeleton and some myosins support insulin granule trafficking and release, although a role for the class I myosin Myo1b, an actin- and membrane-associated load-sensitive motor, in insulin biology is unknown. We found by immunohistochemistry that Myo1b is expressed in islet cells of the rat pancreas. In cultured rat insulinoma 832/13 cells, Myo1b localized near actin patches, the trans-Golgi network (TGN) marker TGN38, and insulin granules in the perinuclear region. Myo1b depletion by small interfering RNA in 832/13 cells reduced intracellular proinsulin and insulin content and glucose-stimulated insulin secretion (GSIS) and led to the accumulation of (pro)insulin secretory granules (SGs) at the TGN. Using an in situ fluorescent pulse-chase strategy to track nascent proinsulin, Myo1b depletion in insulinoma cells reduced the number of (pro)insulin-containing SGs budding from the TGN. The studies indicate for the first time that in pancreatic β-cells Myo1b controls GSIS at least in part by mediating an early stage in insulin granule trafficking from the TGN.
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Affiliation(s)
- Hiroshi Tokuo
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, MA 02118-2518
| | - Shigeru Komaba
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, MA 02118-2518
| | - Lynne M Coluccio
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, MA 02118-2518
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10
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Wang H, Mizuno K, Takahashi N, Kobayashi E, Shirakawa J, Terauchi Y, Kasai H, Okunishi K, Izumi T. Melanophilin Accelerates Insulin Granule Fusion without Predocking to the Plasma Membrane. Diabetes 2020; 69:2655-2666. [PMID: 32994278 DOI: 10.2337/db20-0069] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 09/21/2020] [Indexed: 12/20/2022]
Abstract
Direct observation of fluorescence-labeled secretory granule exocytosis in living pancreatic β-cells has revealed heterogeneous prefusion behaviors: some granules dwell beneath the plasma membrane before fusion, while others fuse immediately once they are recruited to the plasma membrane. Although the former mode seems to follow sequential docking-priming-fusion steps as found in synaptic vesicle exocytosis, the latter mode, which is unique to secretory granule exocytosis, has not been explored well. Here, we show that melanophilin, one of the effectors of the monomeric guanosine-5'-triphosphatase Rab27 on the granule membrane, is involved in such an accelerated mode of exocytosis. Melanophilin-mutated leaden mouse and melanophilin-downregulated human pancreatic β-cells both exhibit impaired glucose-stimulated insulin secretion, with a specific reduction in fusion events that bypass stable docking to the plasma membrane. Upon stimulus-induced [Ca2+]i rise, melanophilin mediates this type of fusion by dissociating granules from myosin-Va and actin in the actin cortex and by associating them with a fusion-competent, open form of syntaxin-4 on the plasma membrane. These findings provide the hitherto unknown mechanism to support sustainable exocytosis by which granules are recruited from the cell interior and fuse promptly without stable predocking to the plasma membrane.
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Affiliation(s)
- Hao Wang
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma, Japan
| | - Kouichi Mizuno
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma, Japan
| | - Noriko Takahashi
- Department of Physiology, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan
| | - Eri Kobayashi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma, Japan
| | - Jun Shirakawa
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Yasuo Terauchi
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Katsuhide Okunishi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma, Japan
| | - Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma, Japan
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11
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Lien W, Chen Y, Li Y, Wu J, Huang K, Lin J, Lin S, Hou C, Wang H, Wu C, Huang S, Chan C. Lifespan regulation in α/β posterior neurons of the fly mushroom bodies by Rab27. Aging Cell 2020; 19:e13179. [PMID: 32627932 PMCID: PMC7431830 DOI: 10.1111/acel.13179] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 05/25/2020] [Indexed: 12/13/2022] Open
Abstract
Brain function has been implicated to control the aging process and modulate lifespan. However, continuous efforts remain for the identification of the minimal sufficient brain region and the underlying mechanism for neuronal regulation of longevity. Here, we show that the Drosophila lifespan is modulated by rab27 functioning in a small subset of neurons of the mushroom bodies (MB), a brain structure that shares analogous functions with mammalian hippocampus and hypothalamus. Depleting rab27 in the α/βp neurons of the MB is sufficient to extend lifespan, enhance systemic stress responses, and alter energy homeostasis, all without trade‐offs in major life functions. Within the α/βp neurons, rab27KO causes the mislocalization of phosphorylated S6K thus attenuates TOR signaling, resulting in decreased protein synthesis and reduced neuronal activity. Consistently, expression of dominant‐negative S6K in the α/βp neurons increases lifespan. Furthermore, the expression of phospho‐mimetic S6 in α/βp neurons of rab27KO rescued local protein synthesis and reversed lifespan extension. These findings demonstrate that inhibiting TOR‐mediated protein synthesis in α/βp neurons is sufficient to promote longevity.
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Affiliation(s)
- Wen‐Yu Lien
- Graduate Institute of Physiology College of Medicine National Taiwan University Taipei Taiwan
| | - Yu‐Ting Chen
- Graduate Institute of Physiology College of Medicine National Taiwan University Taipei Taiwan
| | - Yi‐Jhan Li
- Graduate Institute of Physiology College of Medicine National Taiwan University Taipei Taiwan
| | - Jie‐Kai Wu
- Department of Biochemistry and Graduate Institute of Biomedical Sciences College of Medicine Chang Gung University Taoyuan Taiwan
| | - Kuan‐Lin Huang
- Graduate Institute of Physiology College of Medicine National Taiwan University Taipei Taiwan
| | - Jian‐Rong Lin
- Graduate Institute of Physiology College of Medicine National Taiwan University Taipei Taiwan
| | - Shih‐Ching Lin
- Graduate Institute of Physiology College of Medicine National Taiwan University Taipei Taiwan
| | - Chia‐Chun Hou
- Graduate Institute of Physiology College of Medicine National Taiwan University Taipei Taiwan
| | - Horng‐Dar Wang
- Institute of Biotechnology National Tsing Hua University Hsinchu Taiwan
| | - Chia‐Lin Wu
- Department of Biochemistry and Graduate Institute of Biomedical Sciences College of Medicine Chang Gung University Taoyuan Taiwan
- Department of Neurology Linkou Chang Gung Memorial Hospital Taoyuan Taiwan
| | - Shu‐Yi Huang
- Department of Medical Research National Taiwan University Hospital Taipei Taiwan
| | - Chih‐Chiang Chan
- Graduate Institute of Physiology College of Medicine National Taiwan University Taipei Taiwan
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12
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Bowman SL, Bi-Karchin J, Le L, Marks MS. The road to lysosome-related organelles: Insights from Hermansky-Pudlak syndrome and other rare diseases. Traffic 2020; 20:404-435. [PMID: 30945407 DOI: 10.1111/tra.12646] [Citation(s) in RCA: 120] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/02/2019] [Accepted: 04/02/2019] [Indexed: 12/11/2022]
Abstract
Lysosome-related organelles (LROs) comprise a diverse group of cell type-specific, membrane-bound subcellular organelles that derive at least in part from the endolysosomal system but that have unique contents, morphologies and functions to support specific physiological roles. They include: melanosomes that provide pigment to our eyes and skin; alpha and dense granules in platelets, and lytic granules in cytotoxic T cells and natural killer cells, which release effectors to regulate hemostasis and immunity; and distinct classes of lamellar bodies in lung epithelial cells and keratinocytes that support lung plasticity and skin lubrication. The formation, maturation and/or secretion of subsets of LROs are dysfunctional or entirely absent in a number of hereditary syndromic disorders, including in particular the Hermansky-Pudlak syndromes. This review provides a comprehensive overview of LROs in humans and model organisms and presents our current understanding of how the products of genes that are defective in heritable diseases impact their formation, motility and ultimate secretion.
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Affiliation(s)
- Shanna L Bowman
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania.,Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jing Bi-Karchin
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania.,Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Linh Le
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania.,Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Cell and Molecular Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Michael S Marks
- Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia Research Institute, Philadelphia, Pennsylvania.,Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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13
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Abstract
Glucose-induced (physiological) insulin secretion from the islet β-cell involves interplay between cationic (i.e., changes in intracellular calcium) and metabolic (i.e., generation of hydrophobic and hydrophilic second messengers) events. A large body of evidence affirms support for novel regulation, by G proteins, of specific intracellular signaling events, including actin cytoskeletal remodeling, transport of insulin-containing granules to the plasma membrane for fusion, and secretion of insulin into the circulation. This article highlights the following aspects of GPCR-G protein biology of the islet. First, it overviews our current understanding of the identity of a wide variety of G protein regulators and their modulatory roles in GPCR-G protein-effector coupling, which is requisite for optimal β-cell function under physiological conditions. Second, it describes evidence in support of novel, noncanonical, GPCR-independent mechanisms of activation of G proteins in the islet. Third, it highlights the evidence indicating that abnormalities in G protein function lead to islet β-cell dysregulation and demise under the duress of metabolic stress and diabetes. Fourth, it summarizes observations of potential beneficial effects of GPCR agonists in preventing/halting metabolic defects in the islet β-cell under various pathological conditions (e.g., metabolic stress and inflammation). Lastly, it identifies knowledge gaps and potential avenues for future research in this evolving field of translational islet biology. Published 2020. Compr Physiol 10:453-490, 2020.
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Affiliation(s)
- Anjaneyulu Kowluru
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Center for Translational Research in Diabetes, Biomedical Research Service, John D. Dingell VA Medical Center, Wayne State University, Detroit, Michigan, USA
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14
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Zhou Y, Liu Z, Zhang S, Zhuang R, Liu H, Liu X, Qiu X, Zhang M, Zheng Y, Li L, Hong W, Wang T. RILP Restricts Insulin Secretion Through Mediating Lysosomal Degradation of Proinsulin. Diabetes 2020; 69:67-82. [PMID: 31624142 DOI: 10.2337/db19-0086] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 10/06/2019] [Indexed: 11/13/2022]
Abstract
Insulin secretion is tightly regulated by membrane trafficking. RILP (Rab7 interacting lysosomal protein) regulates the endocytic trafficking, but its role in insulin secretion has not been investigated. In this study, we found that overexpression of RILP inhibited insulin secretion in both the β-cell lines and freshly isolated islets. Consequently, the expression of RILP in islets suppressed the ability to recover the glucose homeostasis in type 1 diabetes mice upon transplantation. Of physiological relevance is that RILP expression was upregulated in the diabetic mouse islets. Mechanistically, overexpression of RILP induced insulin granule clustering, decreased the number of proinsulin-containing granules in β-cells, and significantly promoted proinsulin degradation. Conversely, RILP depletion sustained proinsulin and increased insulin secretion. The proinsulin degradation induced by RILP expression was inhibited by lysosomal inhibitors and was Rab7-dependent. Finally, we showed that RILP interacts with insulin granule-associated Rab26 to restrict insulin secretion. This study presents a new pathway regulating insulin secretion and mechanically demonstrates a novel function of RILP in modulating insulin secretion through mediating the lysosomal degradation of proinsulin.
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Affiliation(s)
- Yuxia Zhou
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Zhiyu Liu
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Shengmei Zhang
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Ruijuan Zhuang
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Huiying Liu
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Xiaoqing Liu
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Xi Qiu
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Ming Zhang
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Yanpan Zheng
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Liangcheng Li
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Wanjin Hong
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
- Institute of Molecular and Cell Biology, A STAR (Agency of Science, Technology and Research), Singapore, Singapore
| | - Tuanlao Wang
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
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15
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Shen L, Gu Y, Qiu Y, Cheng T, Nie A, Cui C, Fu C, Li T, Li X, Fu L, Wang Y, Ni Q, Wang Q, Wang W, Feng B. Atorvastatin Targets the Islet Mevalonate Pathway to Dysregulate mTOR Signaling and Reduce β-Cell Functional Mass. Diabetes 2020; 69:48-59. [PMID: 31649162 DOI: 10.2337/db19-0178] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 10/14/2019] [Indexed: 11/13/2022]
Abstract
Statins are cholesterol-lowering agents that increase the incidence of diabetes and impair glucose tolerance via their detrimental effects on nonhepatic tissues, such as pancreatic islets, but the underlying mechanism has not been determined. In atorvastatin (ator)-treated high-fat diet-fed mice, we found reduced pancreatic β-cell size and β-cell mass, fewer mature insulin granules, and reduced insulin secretion and glucose tolerance. Transcriptome profiling of primary pancreatic islets showed that ator inhibited the expression of pancreatic transcription factor, mechanistic target of rapamycin (mTOR) signaling, and small G protein (sGP) genes. Supplementation of the mevalonate pathway intermediate geranylgeranyl pyrophosphate (GGPP), which is produced by 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, significantly restored the attenuated mTOR activity, v-maf musculoaponeurotic fibrosarcoma oncogene homolog A (MafA) expression, and β-cell function after ator, lovastatin, rosuvastatin, and fluvastatin treatment; this effect was potentially mediated by sGP prenylation. Rab5a, the sGP in pancreatic islets most affected by ator treatment, was found to positively regulate mTOR signaling and β-cell function. Rab5a knockdown mimicked the effect of ator treatment on β-cells. Thus, ator impairs β-cell function by regulating sGPs, for example, Rab5a, which subsequently attenuates islet mTOR signaling and reduces functional β-cell mass. GGPP supplementation could constitute a new approach for preventing statin-induced hyperglycemia.
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Affiliation(s)
- Linyan Shen
- Department of Metabolism and Endocrinology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yanyun Gu
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yixuan Qiu
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Tingting Cheng
- Department of Metabolism and Endocrinology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Aifang Nie
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Canqi Cui
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chenyang Fu
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Tingting Li
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xuelin Li
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Lihong Fu
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yanqiu Wang
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qicheng Ni
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qidi Wang
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Weiqing Wang
- National Research Centre for Endocrine and Metabolic Diseases, Shanghai Institute for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Bo Feng
- Department of Metabolism and Endocrinology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
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16
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Nguyen PM, Gandasi NR, Xie B, Sugahara S, Xu Y, Idevall-Hagren O. The PI(4)P phosphatase Sac2 controls insulin granule docking and release. J Cell Biol 2019; 218:3714-3729. [PMID: 31533953 PMCID: PMC6829663 DOI: 10.1083/jcb.201903121] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 06/20/2019] [Accepted: 08/08/2019] [Indexed: 12/12/2022] Open
Abstract
Insulin granule biogenesis involves transport to, and stable docking at, the plasma membrane before priming and fusion. Defects in this pathway result in impaired insulin secretion and are a hallmark of type 2 diabetes. We now show that the phosphatidylinositol 4-phosphate phosphatase Sac2 localizes to insulin granules in a substrate-dependent manner and that loss of Sac2 results in impaired insulin secretion. Sac2 operates upstream of granule docking, since loss of Sac2 prevented granule tethering to the plasma membrane and resulted in both reduced granule density and number of exocytic events. Sac2 levels correlated positively with the number of docked granules and exocytic events in clonal β cells and with insulin secretion in human pancreatic islets, and Sac2 expression was reduced in islets from type 2 diabetic subjects. Taken together, we identified a phosphoinositide switch on the surface on insulin granules that is required for stable granule docking at the plasma membrane and impaired in human type 2 diabetes.
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Affiliation(s)
- Phuoc My Nguyen
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Beichen Xie
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sari Sugahara
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.,Laboratory of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Yingke Xu
- Department of Biomedical Engineering, Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou, China
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17
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Chen G, Yuan A, Cai T, Li CM, Bentley AR, Zhou J, N Shriner D, A Adeyemo A, N Rotimi C. Measuring gene-gene interaction using Kullback-Leibler divergence. Ann Hum Genet 2019; 83:405-417. [PMID: 31206606 DOI: 10.1111/ahg.12324] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 03/30/2019] [Accepted: 04/12/2019] [Indexed: 12/29/2022]
Abstract
Genome-wide association studies (GWAS) are used to investigate genetic variants contributing to complex traits. Despite discovering many loci, a large proportion of "missing" heritability remains unexplained. Gene-gene interactions may help explain some of this gap. Traditionally, gene-gene interactions have been evaluated using parametric statistical methods such as linear and logistic regression, with multifactor dimensionality reduction (MDR) used to address sparseness of data in high dimensions. We propose a method for the analysis of gene-gene interactions across independent single-nucleotide polymorphisms (SNPs) in two genes. Typical methods for this problem use statistics based on an asymptotic chi-squared mixture distribution, which is not easy to use. Here, we propose a Kullback-Leibler-type statistic, which follows an asymptotic, positive, normal distribution under the null hypothesis of no relationship between SNPs in the two genes, and normally distributed under the alternative hypothesis. The performance of the proposed method is evaluated by simulation studies, which show promising results. The method is also used to analyze real data and identifies gene-gene interactions among RAB3A, MADD, and PTPRN on type 2 diabetes (T2D) status.
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Affiliation(s)
- Guanjie Chen
- Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
| | - Ao Yuan
- Department of Biostatistics, Bioinformatics and Biomathematics, Georgetown University, Washington, DC
| | - Tao Cai
- Experimental Medicine Section, Laboratory of Sensory Biology, NIDCR, NIH, Bethesda, Maryland
| | - Chuan-Ming Li
- Division of Scientific Program, National Institute of Deafness and Other Communication Disorders, Rockville, Maryland, 20892
| | - Amy R Bentley
- Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
| | - Jie Zhou
- Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
| | - Daniel N Shriner
- Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
| | - Adebowale A Adeyemo
- Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
| | - Charles N Rotimi
- Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
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18
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Boucher JM, Robich M, Scott SS, Yang X, Ryzhova L, Turner JE, Pinz I, Liaw L. Rab27a Regulates Human Perivascular Adipose Progenitor Cell Differentiation. Cardiovasc Drugs Ther 2019; 32:519-530. [PMID: 30105417 DOI: 10.1007/s10557-018-6813-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
PURPOSE Perivascular adipose tissue (PVAT) surrounds blood vessels and regulates vascular tone through paracrine secretion of cytokines. During conditions promoting cardiometabolic dysfunction, such as obesity, cytokine secretion is altered towards a proinflammatory and proatherogenic profile. Despite the clinical implications for cardiovascular disease, studies addressing the biology of human PVAT remain limited. We are interested in characterizing the resident adipose progenitor cells (APCs) because of their potential role in PVAT expansion during obesity. We also focused on proteins regulating paracrine interactions, including the small GTPase Rab27a, which regulates protein trafficking and secretion. METHODS PVAT from the ascending aorta was collected from patients with severe cardiovascular disease undergoing coronary artery bypass grafting (CABG). Freshly-isolated PVAT was digested and APC expanded in culture for characterizing progenitor markers, evaluating adipogenic potential and assessing the function(s) of Rab27a. RESULTS Using flow cytometry, RT-PCR, and immunoblot, we characterized APC from human PVAT as negative for CD45 and CD31 and expressing CD73, CD105, and CD140A. These APCs differentiate into multilocular, UCP1-producing adipocytes in vitro. Rab27a was detected in interstitial cells of human PVAT in vivo and along F-actin tracks of PVAT-APC in vitro. Knockdown of Rab27a using siRNA in PVAT-APC prior to induction resulted in a marked reduction in lipid accumulation and reduced expression of adipogenic differentiation markers. CONCLUSIONS PVAT-APC from CABG donors express common adipocyte progenitor markers and differentiate into UCP1-containing adipocytes. Rab27a has an endogenous role in promoting the maturation of adipocytes from human PVAT-derived APC.
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Affiliation(s)
- Joshua M Boucher
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04072, USA
| | - Michael Robich
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04072, USA
- Division of Thoracic and Cardiac Surgery, Maine Medical Center, Portland, ME, 04102, USA
| | - S Spencer Scott
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04072, USA
| | - Xuehui Yang
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04072, USA
| | - Larisa Ryzhova
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04072, USA
| | - Jacqueline E Turner
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04072, USA
| | - Ilka Pinz
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04072, USA
| | - Lucy Liaw
- Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME, 04072, USA.
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19
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McKay BS. Pigmentation and vision: Is GPR143 in control? J Neurosci Res 2019; 97:77-87. [PMID: 29761529 PMCID: PMC6235735 DOI: 10.1002/jnr.24246] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 02/21/2018] [Accepted: 03/21/2018] [Indexed: 12/30/2022]
Abstract
Albinism, typically characterized by decreased melanin synthesis, is associated with significant visual deficits owing to developmental changes during neurosensory retina development. All albinism is caused by genetic mutations in a group of diverse genes including enzymes, transporters, G-protein coupled receptor. Interestingly, these genes are not expressed in the neurosensory retina. Further, regardless of cause of albinism, all forms of albinism have the same retinal pathology, the extent of which is variable. In this review, we explore the possibility that this similarity in retinal phenotype is because all forms of albinism funnel through the same final common pathway. There are currently seven known genes linked to the seven forms of ocular cutaneous albinism. These types of albinism are the most common, and result in changes to all pigmented tissues (hair, skin, eyes). We will discuss the incidence and mechanism, where known, to develop a picture as to how the mutations cause albinism. Next, we will examine the one form of albinism which causes tissue-specific pathology, ocular albinism, where the eye exhibits the retinal albinism phenotype despite near normal melanin synthesis. We will discuss a potential way to treat the disease and restore normal retinal development. Finally, we will briefly discuss the possibility that this same pathway may intersect with the most common cause of permanent vision loss in the elderly.
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Affiliation(s)
- Brian S McKay
- Department of Ophthalmology and Vision Science, University of Arizona, Tucson, Arizona
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20
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Feng F, Jiang Y, Lu H, Lu X, Wang S, Wang L, Wei M, Lu W, Du Z, Ye Z, Yang G, Yuan F, Ma Y, Lei X, Lu Z. Rab27A mediated by NF-κB promotes the stemness of colon cancer cells via up-regulation of cytokine secretion. Oncotarget 2018; 7:63342-63351. [PMID: 27556511 PMCID: PMC5325368 DOI: 10.18632/oncotarget.11454] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 08/11/2016] [Indexed: 12/21/2022] Open
Abstract
Recent evidences have unveiled critical roles of cancer stem cells (CSCs) in tumorigenicity, but how interactions between CSC and tumor environments help maintain CSC initiation remains obscure. The small GTPases Rab27A regulates autocrine and paracrine cytokines by monitoring exocytosis of extracellular vesicles, and is reported to promote certain tumor progression. We observe that overexpression of Rab27A increased sphere formation efficiency (SFE) by increasing the proportion of CD44+ and PKH26high cells in HT29 cell lines, and accelerating the growth of colosphere with higher percentage of cells at S phase. Mechanism study revealed that the supernatant derived from HT29 sphere after Rab27A overexpression was able to expand sphere numbers with elevated secretion of VEGF and TGF-β. In tumor implanting nude mice model, tumor initiation rates and tumor sizes were enhanced by Rab27A with obvious angiogenesis. As a contrast, knocking down Rab27A impaired the above effects. More importantly, the correlation between higher p65 level and Rab27A in colon sphere was detected, p65 was sufficient to induce up-regulation of Rab27A and a functional NF-κB binding site in the Rab27A promoter was demonstrated. Altogether, our findings reveal a unique mechanism that tumor environment related NF-κB signaling promotes various colon cancer stem cells (cCSCs) properties via an amplified paracrine mechanism regulated by higher Rab27A level.
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Affiliation(s)
- Feixue Feng
- The State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, China.,Department of Clinical Laboratory, the Affiliated Hospital of Shaanxi University of Chinese Medicine, Xianyang, China
| | - Yinghao Jiang
- The State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, China
| | - Huanyu Lu
- Department of Occupational and Environmental Health, the Ministry of Education Key Lab of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an, China
| | - Xiaozhao Lu
- The State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, China
| | - Shan Wang
- The State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, China
| | - Lifeng Wang
- The State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China
| | - Mengying Wei
- The State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China
| | - Wei Lu
- The State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, China
| | - Zhichao Du
- The State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, China
| | - Zichen Ye
- The State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, China
| | - Guodong Yang
- The State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China
| | - Fang Yuan
- Department of Clinical Laboratory, the Affiliated Hospital of Shaanxi University of Chinese Medicine, Xianyang, China
| | - Yanxia Ma
- Department of Clinical Laboratory, the Affiliated Hospital of Shaanxi University of Chinese Medicine, Xianyang, China
| | - Xiaoying Lei
- The State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, China
| | - Zifan Lu
- The State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, Fourth Military Medical University, Xi'an, China
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Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 446] [Impact Index Per Article: 74.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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22
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Feng F, Zhang J, Fan X, Yuan F, Jiang Y, Lv R, Ma Y. Downregulation of Rab27A contributes to metformin-induced suppression of breast cancer stem cells. Oncol Lett 2017; 14:2947-2953. [PMID: 28928832 PMCID: PMC5588170 DOI: 10.3892/ol.2017.6542] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Accepted: 04/28/2017] [Indexed: 01/16/2023] Open
Abstract
Cancer stem cells (CSCs) are associated with tumor initiation, therapeutic resistance, relapse and metastasis. However, the underlying mechanisms CSCs use to preserve stemness are not yet fully understood. The present study demonstrated that the expression of RAB27A, member RAS oncogene family (Rab27a), which was reported to promote tumor progression by upregulating exocytosis of extracellular vesicles, was higher in mammosphere cells than in adherent MDA-MB-231 breast cancer cells. Downregulation of Rab27A inhibited mammosphere formation by decreasing the proportion of CD44+CD24-/low cells of the MDA-MB-231 cell line. Furthermore, Rab27A overexpression redistributed the cell cycle of breast (b) CSCs. The present study revealed that downregulation of Rab27A enhanced the capacity of metformin, the most widely used oral hypoglycemic drug for the treatment of type II diabetes, to inhibit mammosphere growth. Metformin reduced the expression of Rab27A dose-dependently. These data suggested that Rab27A acts as a mediator of human bCSCs by promoting the growth of mammospheres and that synergistic suppression of Rab27A, alone or in combination with metformin, holds promise for therapeutically targeting bCSCs.
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Affiliation(s)
- Feixue Feng
- Department of Clinical Laboratory, The Affiliated Hospital of Shaanxi University of Chinese Medicine, Xianyang, Shaanxi 712000, P.R. China
| | - Jianping Zhang
- Department of Clinical Laboratory, The XianYang Central Hospital, Xianyang, Shaanxi 712000, P.R. China
| | - Xiaoxuan Fan
- Department of Clinical Laboratory, The Affiliated Hospital of Shaanxi University of Chinese Medicine, Xianyang, Shaanxi 712000, P.R. China
| | - Fang Yuan
- Department of Clinical Laboratory, The Affiliated Hospital of Shaanxi University of Chinese Medicine, Xianyang, Shaanxi 712000, P.R. China
| | - Yinghao Jiang
- Department of Pharmacogenomics, The School of Pharmacy, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Ruihua Lv
- Department of Clinical Laboratory, The Affiliated Hospital of Shaanxi University of Chinese Medicine, Xianyang, Shaanxi 712000, P.R. China
| | - Yanxia Ma
- Department of Clinical Laboratory, The Affiliated Hospital of Shaanxi University of Chinese Medicine, Xianyang, Shaanxi 712000, P.R. China
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23
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Molecular regulation of insulin granule biogenesis and exocytosis. Biochem J 2017; 473:2737-56. [PMID: 27621482 DOI: 10.1042/bcj20160291] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 04/19/2016] [Indexed: 12/15/2022]
Abstract
Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by hyperglycemia, insulin resistance and hyperinsulinemia in early disease stages but a relative insulin insufficiency in later stages. Insulin, a peptide hormone, is produced in and secreted from pancreatic β-cells following elevated blood glucose levels. Upon its release, insulin induces the removal of excessive exogenous glucose from the bloodstream primarily by stimulating glucose uptake into insulin-dependent tissues as well as promoting hepatic glycogenesis. Given the increasing prevalence of T2DM worldwide, elucidating the underlying mechanisms and identifying the various players involved in the synthesis and exocytosis of insulin from β-cells is of utmost importance. This review summarizes our current understanding of the route insulin takes through the cell after its synthesis in the endoplasmic reticulum as well as our knowledge of the highly elaborate network that controls insulin release from the β-cell. This network harbors potential targets for anti-diabetic drugs and is regulated by signaling cascades from several endocrine systems.
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24
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miR-124a expression contributes to the monophasic pattern of insulin secretion in islets from pregnant rats submitted to a low-protein diet. Eur J Nutr 2017; 57:1471-1483. [PMID: 28314963 DOI: 10.1007/s00394-017-1425-z] [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: 10/24/2016] [Accepted: 03/01/2017] [Indexed: 10/19/2022]
Abstract
PURPOSE To evaluate the role of miR-124a in the regulation of genes involved in insulin exocytosis and its effects on the kinetics of insulin secretion in pancreatic islets from pregnant rats submitted to a low-protein diet. METHODS Adult control non-pregnant (CNP) and control pregnant (CP) rats were fed a normal protein diet (17%), whereas low-protein non-pregnant (LPNP) and low-protein pregnant (LPP) rats were fed a low-protein diet (6%) from days 1 to 15 of pregnancy. Kinetics of the glucose-induced insulin release and measurement of [Ca2+]i in pancreatic islets were assessed by standard protocols. The miR-124a expression and gene transcriptions from pancreatic islets were determined by real-time polymerase chain reaction. RESULTS In islets from LPP rats, the first phase of insulin release was abrogated. The AUC [Ca2+]i from the LPP group was lower compared with the other groups. miR-124a expression was reduced by a low-protein diet. SNAP-25 mRNA, protein expression, and Rab3A protein content were lower in the LPP rats than in CP rats. Syntaxin 1A and Kir6.2 mRNA levels were decreased in islets from low-protein rats compared with control rats, whereas their protein content was reduced in islets from pregnant rats. CONCLUSIONS Loss of biphasic insulin secretion in islets from LPP rats appears to have resulted from reduced [Ca2+]i due, at least in part, to Kir6.2 underexpression and from the changes in exocytotic elements that are influenced either directly or indirectly by miR-124a.
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25
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Dolai S, Xie L, Zhu D, Liang T, Qin T, Xie H, Kang Y, Chapman ER, Gaisano HY. Synaptotagmin-7 Functions to Replenish Insulin Granules for Exocytosis in Human Islet β-Cells. Diabetes 2016; 65:1962-76. [PMID: 27207520 PMCID: PMC5384637 DOI: 10.2337/db15-1436] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 04/16/2016] [Indexed: 12/13/2022]
Abstract
Synaptotagmin (Syt)-7, a major component of the exocytotic machinery in neurons, is also the major Syt in rodent pancreatic β-cells shown to mediate glucose-stimulated insulin secretion (GSIS). However, Syt-7's precise exocytotic actions in β-cells remain unknown. We show that Syt-7 is abundant in human β-cells. Adenovirus-short hairpin RNA knockdown (KD) of Syt-7 in human islets reduced first- and second-phase GSIS attributed to the reduction of exocytosis of predocked and newcomer insulin secretory granules (SGs). Glucose stimulation expectedly induced Syt-7 association in a Ca(2+)-dependent manner with syntaxin-3 and syntaxin-1A soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes known to mediate exocytosis of newcomer and predocked SGs, respectively. However, Syt-7-KD did not disrupt SNARE complex assembly. Instead, electron microscopy analysis showed that Syt-7-KD reduced the recruitment of SGs to the plasma membrane after glucose-stimulated depletion, which could not be rescued by glucagon-like peptide 1 pretreatment. To assess the possibility that this new action of Syt-7 on SG recruitment may involve calmodulin (CaM), pretreatment of islets with CaM blocker calmidazolium showed effects very similar to those of Syt-7-KD. Syt-7 therefore plays a novel more dominant function in the replenishment of releasable SG pools in human β-cells than its previously purported role in exocytotic fusion per se.
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Affiliation(s)
- Subhankar Dolai
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Li Xie
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Dan Zhu
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Tao Liang
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Tairan Qin
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Huanli Xie
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Youhou Kang
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Edwin R Chapman
- Department of Neuroscience, Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI
| | - Herbert Y Gaisano
- Department of Medicine, University of Toronto, Toronto, ON, Canada Department of Physiology, University of Toronto, Toronto, ON, Canada
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26
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Yamaoka M, Ishizaki T, Kimura T. GTP- and GDP-Dependent Rab27a Effectors in Pancreatic Beta-Cells. Biol Pharm Bull 2016; 38:663-8. [PMID: 25947911 DOI: 10.1248/bpb.b14-00886] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Small guanosine triphosphatases (GTPases) participate in a wide variety of cellular functions including proliferation, differentiation, adhesion, and intracellular transport. Conventionally, only the guanosine 5'-triphosphate (GTP)-bound small GTPase interacts with effector proteins, and the resulting downstream signals control specific cellular functions. Therefore, the GTP-bound form is regarded as active, and the focus has been on searching for proteins that bind the GTP form to look for their effectors. The Rab family small GTPase Rab27a is highly expressed in some secretory cells and is involved in the control of membrane traffic. The present study reviews recent progress in our understanding of the roles of Rab27a and its effectors in pancreatic beta-cells. In the basal state, GTP-bound Rab27a controls insulin secretion at pre-exocytic stages via its GTP-dependent effectors. We previously identified novel guanosine 5'-diphosphate (GDP)-bound Rab27-interacting proteins. Interestingly, GDP-bound Rab27a controls endocytosis of the secretory membrane via its interaction with these proteins. We also demonstrated that the insulin secretagogue glucose converts Rab27a from its GTP- to GDP-bound forms. Thus, GTP- and GDP-bound Rab27a regulate pre-exocytic and endocytic stages in membrane traffic, respectively. Since the physiological importance of GDP-bound GTPases has been largely overlooked, we consider that the investigation of GDP-dependent effectors for other GTPases is necessary for further understanding of cellular function.
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Affiliation(s)
- Mami Yamaoka
- Department of Pharmacology, Oita University Faculty of Medicine
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27
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Yamaoka M, Ando T, Terabayashi T, Okamoto M, Takei M, Nishioka T, Kaibuchi K, Matsunaga K, Ishizaki R, Izumi T, Niki I, Ishizaki T, Kimura T. PI3K regulates endocytosis after insulin secretion by mediating signaling crosstalk between Arf6 and Rab27a. J Cell Sci 2015; 129:637-49. [PMID: 26683831 DOI: 10.1242/jcs.180141] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 12/03/2015] [Indexed: 01/12/2023] Open
Abstract
In secretory cells, endocytosis is coupled to exocytosis to enable proper secretion. Although endocytosis is crucial to maintain cellular homeostasis before and after secretion, knowledge about secretagogue-induced endocytosis in secretory cells is still limited. Here, we searched for proteins that interacted with the Rab27a GTPase-activating protein (GAP) EPI64 (also known as TBC1D10A) and identified the Arf6 guanine-nucleotide-exchange factor (GEF) ARNO (also known as CYTH2) in pancreatic β-cells. We found that the insulin secretagogue glucose promotes phosphatidylinositol (3,4,5)-trisphosphate (PIP3) generation through phosphoinositide 3-kinase (PI3K), thereby recruiting ARNO to the intracellular side of the plasma membrane. Peripheral ARNO promotes clathrin assembly through its GEF activity for Arf6 and regulates the early stage of endocytosis. We also found that peripheral ARNO recruits EPI64 to the same area and that the interaction requires glucose-induced endocytosis in pancreatic β-cells. Given that GTP- and GDP-bound Rab27a regulate exocytosis and the late stage of endocytosis, our results indicate that the glucose-induced activation of PI3K plays a pivotal role in exocytosis-endocytosis coupling, and that ARNO and EPI64 regulate endocytosis at distinct stages.
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Affiliation(s)
- Mami Yamaoka
- Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
| | - Tomomi Ando
- Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
| | - Takeshi Terabayashi
- Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
| | - Mitsuhiro Okamoto
- Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
| | - Masahiro Takei
- Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
| | - Tomoki Nishioka
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa, Nagoya, Aichi 466-8550, Japan
| | - Kozo Kaibuchi
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa, Nagoya, Aichi 466-8550, Japan JST, CREST, 4-1-8 Honcho, Kawaguchi 332-0012, Japan
| | - Kohichi Matsunaga
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Ray Ishizaki
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
| | - Ichiro Niki
- Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
| | - Toshimasa Ishizaki
- Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
| | - Toshihide Kimura
- Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
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28
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Jiang S, Shen D, Jia WJ, Han X, Shen N, Tao W, Gao X, Xue B, Li CJ. GGPPS-mediated Rab27A geranylgeranylation regulates β cell dysfunction during type 2 diabetes development by affecting insulin granule docked pool formation. J Pathol 2015; 238:109-19. [PMID: 26434932 DOI: 10.1002/path.4652] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 08/19/2015] [Accepted: 09/28/2015] [Indexed: 11/09/2022]
Abstract
Loss of first-phase insulin secretion associated with β cell dysfunction is an independent predictor of type 2 diabetes mellitus (T2DM) onset. Here we found that a critical enzyme involved in protein prenylation, geranylgeranyl pyrophosphate synthase (GGPPS), is required to maintain first-phase insulin secretion. GGPPS shows a biphasic expression pattern in islets of db/db mice during the progression of T2DM: GGPPS is increased during the insulin compensatory period, followed by a decrease during β cell dysfunction. Ggpps deletion in β cells results in typical T2DM β cell dysfunction, with blunted glucose-stimulated insulin secretion and consequent insulin secretion insufficiency. However, the number and size of islets and insulin biosynthesis are unaltered. Transmission electron microscopy shows a reduced number of insulin granules adjacent to the cellular membrane, suggesting a defect in docked granule pool formation, while the reserve pool is unaffected. Ggpps ablation depletes GGPP and impairs Rab27A geranylgeranylation, which is responsible for the docked pool deficiency in Ggpps-null mice. Moreover, GGPPS re-expression or GGPP administration restore glucose-stimulated insulin secretion in Ggpps-null islets. These results suggest that GGPPS-controlled protein geranylgeranylation, which regulates formation of the insulin granule docked pool, is critical for β cell function and insulin release during the development of T2DM.
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Affiliation(s)
- Shan Jiang
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Di Shen
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Wen-Jun Jia
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Xiao Han
- Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, People's Republic of China
| | - Ning Shen
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Weiwei Tao
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Xiang Gao
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Bin Xue
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
| | - Chao-Jun Li
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Centre and School of Medicine, Nanjing University, People's Republic of China
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29
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β-Cell Insulin Secretion Requires the Ubiquitin Ligase COP1. Cell 2015; 163:1457-67. [PMID: 26627735 DOI: 10.1016/j.cell.2015.10.076] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 09/22/2015] [Accepted: 10/19/2015] [Indexed: 11/20/2022]
Abstract
A variety of signals finely tune insulin secretion by pancreatic β cells to prevent both hyper-and hypoglycemic states. Here, we show that post-translational regulation of the transcription factors ETV1, ETV4, and ETV5 by the ubiquitin ligase COP1 (also called RFWD2) in β cells is critical for insulin secretion. Mice lacking COP1 in β cells developed diabetes due to insulin granule docking defects that were fully rescued by genetic deletion of Etv1, Etv4, and Etv5. Genes regulated by ETV1, ETV4, or ETV5 in the absence of mouse COP1 were enriched in human diabetes-associated genes, suggesting that they also influence human β-cell pathophysiology. In normal β cells, ETV4 was stabilized upon membrane depolarization and limited insulin secretion under hyperglycemic conditions. Collectively, our data reveal that ETVs negatively regulate insulin secretion for the maintenance of normoglycemia.
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30
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Reichhart N, Markowski M, Ishiyama S, Wagner A, Crespo-Garcia S, Schorb T, Ramalho JS, Milenkovic VM, Föckler R, Seabra MC, Strauß O. Rab27a GTPase modulates L-type Ca2+ channel function via interaction with the II-III linker of CaV1.3 subunit. Cell Signal 2015; 27:2231-40. [PMID: 26235199 DOI: 10.1016/j.cellsig.2015.07.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 07/28/2015] [Indexed: 12/31/2022]
Abstract
In a variety of cells, secretory processes require the activation of both Rab27a and L-type channels of the Ca(V)1.3 subtype. In the retinal pigment epithelium (RPE), Rab27a and Ca(V)1.3 channels regulate growth-factor secretion towards its basolateral side. Analysis of murine retina sections revealed a co-localization of both Rab27a and Ca(V)1.3 at the basolateral membrane of the RPE. Heterologously expressed Ca(V)1.3/β3/α2δ1 channels showed negatively shifted voltage-dependence and decreased current density of about 70% when co-expressed with Rab27a. However, co-localization analysis using α(5)β(1) integrin as a membrane marker revealed that Rab27a co-expression reduced the surface expression of Ca(V)1.3 only about 10%. Physical binding of heterologously expressed Rab27a with Ca(V)1.3 channels was shown by co-localization in immunocytochemistry as well as co-immunoprecipitation which was abolished after deletion of a MyRIP-homologous amino acid sequence at the II-III linker of the Ca(V)1.3 subunit. Rab27a over-expression in ARPE-19 cells positively shifted the voltage dependence, decreased current density of endogenous Ca(V)1.3 channels and reduced VEGF-A secretion. We show the first evidence of a direct functional modulation of an ion channel by Rab27a suggesting a new mechanism of Rab and ion channel interaction in the control of VEGF-A secretion in the RPE.
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Affiliation(s)
- Nadine Reichhart
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany; Experimental Ophthalmology, Eye Hospital, Charité University Medicine, Campus Virchow-Clinic, Berlin, Germany
| | - Magdalena Markowski
- Experimental Ophthalmology, Eye Hospital, Charité University Medicine, Campus Virchow-Clinic, Berlin, Germany
| | - Shimpei Ishiyama
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
| | - Andrea Wagner
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
| | - Sergio Crespo-Garcia
- Experimental Ophthalmology, Eye Hospital, Charité University Medicine, Campus Virchow-Clinic, Berlin, Germany
| | - Talitha Schorb
- Experimental Ophthalmology, Eye Hospital, Charité University Medicine, Campus Virchow-Clinic, Berlin, Germany
| | - José S Ramalho
- CEDOC, Faculdade de Ciências Médicas (FCM), Universidade Nova de Lisboa, Lisbon, Portugal
| | - Vladimir M Milenkovic
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany; Department of Psychiatry and Psychotherapy, Molecular Neuroscience, University of Regensburg, Germany
| | - Renate Föckler
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
| | - Miguel C Seabra
- CEDOC, Faculdade de Ciências Médicas (FCM), Universidade Nova de Lisboa, Lisbon, Portugal
| | - Olaf Strauß
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany; Experimental Ophthalmology, Eye Hospital, Charité University Medicine, Campus Virchow-Clinic, Berlin, Germany.
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31
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Rab27A Is Present in Mouse Pancreatic Acinar Cells and Is Required for Digestive Enzyme Secretion. PLoS One 2015; 10:e0125596. [PMID: 25951179 PMCID: PMC4423933 DOI: 10.1371/journal.pone.0125596] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 03/16/2015] [Indexed: 01/24/2023] Open
Abstract
The small G-protein Rab27A has been shown to regulate the intracellular trafficking of secretory granules in various cell types. However, the presence, subcellular localization and functional impact of Rab27A on digestive enzyme secretion by mouse pancreatic acinar cells are poorly understood. Ashen mice, which lack the expression of Rab27A due to a spontaneous mutation, were used to investigate the function of Rab27A in pancreatic acinar cells. Isolated pancreatic acini were prepared from wild-type or ashen mouse pancreas by collagenase digestion, and CCK- or carbachol-induced amylase secretion was measured. Secretion occurring through the major-regulated secretory pathway, which is characterized by zymogen granules secretion, was visualized by Dextran-Texas Red labeling of exocytotic granules. The minor-regulated secretory pathway, which operates through the endosomal/lysosomal pathway, was characterized by luminal cell surface labeling of lysosomal associated membrane protein 1 (LAMP1). Compared to wild-type, expression of Rab27B was slightly increased in ashen mouse acini, while Rab3D and digestive enzymes (amylase, lipase, chymotrypsin and elastase) were not affected. Localization of Rab27B, Rab3D and amylase by immunofluorescence was similar in both wild-type and ashen acinar cells. The GTP-bound states of Rab27B and Rab3D in wild-type and ashen mouse acini also remained similar in amount. In contrast, acini from ashen mice showed decreased amylase release induced by CCK- or carbachol. Rab27A deficiency reduced the apical cell surface labeling of LAMP1, but did not affect that of Dextran-Texas Red incorporation into the fusion pockets at luminal surface. These results show that Rab27A is present in mouse pancreatic acinar cells and mainly regulates secretion through the minor-regulated pathway.
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Cazares VA, Subramani A, Saldate JJ, Hoerauf W, Stuenkel EL. Distinct actions of Rab3 and Rab27 GTPases on late stages of exocytosis of insulin. Traffic 2014; 15:997-1015. [PMID: 24909540 DOI: 10.1111/tra.12182] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 06/04/2014] [Accepted: 06/04/2014] [Indexed: 12/16/2022]
Abstract
Rab GTPases associated with insulin-containing secretory granules (SGs) are key in targeting, docking and assembly of molecular complexes governing pancreatic β-cell exocytosis. Four Rab3 isoforms along with Rab27A are associated with insulin granules, yet elucidation of the distinct roles of these Rab families on exocytosis remains unclear. To define specific actions of these Rab families we employ Rab3GAP and/or EPI64A GTPase-activating protein overexpression in β-cells from wild-type or Ashen mice to selectively transit the entire Rab3 family or Rab27A to a GDP-bound state. Ashen mice carry a spontaneous mutation that eliminates Rab27A expression. Using membrane capacitance measurements we find that GTP/GDP nucleotide cycling of Rab27A is essential for generation of the functionally defined immediately releasable pool (IRP) and central to regulating the size of the readily releasable pool (RRP). By comparison, nucleotide cycling of Rab3 GTPases, but not of Rab27A, is essential for a kinetically rapid filling of the RRP with SGs. Aside from these distinct functions, Rab3 and Rab27A GTPases demonstrate considerable functional overlap in building the readily releasable granule pool. Hence, while Rab3 and Rab27A cooperate to generate release-ready SGs in β-cells, they also direct unique kinetic and functional properties of the exocytotic pathway.
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Affiliation(s)
- Victor A Cazares
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, 48109, USA
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Gandasi NR, Barg S. Contact-induced clustering of syntaxin and munc18 docks secretory granules at the exocytosis site. Nat Commun 2014; 5:3914. [PMID: 24835618 DOI: 10.1038/ncomms4914] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 04/17/2014] [Indexed: 02/06/2023] Open
Abstract
Docking of secretory vesicles at the plasma membrane is a poorly understood prerequisite for exocytosis. Current models propose raft-like clusters containing syntaxin as docking receptor, but direct evidence for this is lacking. Here we provide quantitative measurements of several exocytosis proteins (syntaxin, SNAP25, munc18, munc13 and rab3) at the insulin granule release site and show that docking coincides with rapid de novo formation of syntaxin1/munc18 clusters at the nascent docking site. Formation of such clusters prevents undocking and is not observed during failed docking attempts. Overexpression of syntaxins' N-terminal Habc-domain competitively interferes with both cluster formation and successful docking. SNAP25 and munc13 are recruited to the docking site more than a minute later, consistent with munc13's reported role in granule priming rather than docking. We conclude that secretory vesicles dock by inducing syntaxin1/munc18 clustering in the target membrane, and find no evidence for preformed docking receptors.
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Affiliation(s)
- Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
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Li LC, Wang Y, Carr R, Haddad CS, Li Z, Qian L, Oberholzer J, Maker AV, Wang Q, Prabhakar BS. IG20/MADD plays a critical role in glucose-induced insulin secretion. Diabetes 2014; 63:1612-23. [PMID: 24379354 PMCID: PMC3994957 DOI: 10.2337/db13-0707] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Pancreatic β-cell dysfunction is a common feature of type 2 diabetes. Earlier, we had cloned IG20 cDNA from a human insulinoma and had shown that IG20/MADD can encode six different splice isoforms that are differentially expressed and have unique functions, but its role in β-cell function was unexplored. To investigate the role of IG20/MADD in β-cell function, we generated conditional knockout (KMA1ko) mice. Deletion of IG20/MADD in β-cells resulted in hyperglycemia and glucose intolerance associated with reduced and delayed glucose-induced insulin production. KMA1ko β-cells were able to process insulin normally but had increased insulin accumulation and showed a severe defect in glucose-induced insulin release. These findings indicated that IG20/MADD plays a critical role in glucose-induced insulin release from β-cells and that its functional disruption can cause type 2 diabetes. The clinical relevance of these findings is highlighted by recent reports of very strong association of the rs7944584 single nucleotide polymorphism (SNP) of IG20/MADD with fasting hyperglycemia/diabetes. Thus, IG20/MADD could be a therapeutic target for type 2 diabetes, particularly in those with the rs7944584 SNP.
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Affiliation(s)
- Liang-cheng Li
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL
- School of Pharmaceutical Sciences, Xiamen University at Xiang'an, Xiamen, Fujian, China
| | - Yong Wang
- Department of Surgery, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Ryan Carr
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Christine Samir Haddad
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Ze Li
- Department of Surgery, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Lixia Qian
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Jose Oberholzer
- Department of Surgery, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Ajay V. Maker
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL
- Department of Surgery, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Qian Wang
- Department of Surgery, College of Medicine, University of Illinois at Chicago, Chicago, IL
| | - Bellur S. Prabhakar
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, IL
- Corresponding author: Bellur S. Prabhakar,
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Insight into insulin secretion from transcriptome and genetic analysis of insulin-producing cells of Drosophila. Genetics 2014; 197:175-92. [PMID: 24558258 PMCID: PMC4012477 DOI: 10.1534/genetics.113.160663] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Insulin-producing cells (IPCs) in the Drosophila brain produce and release insulin-like peptides (ILPs) to the hemolymph. ILPs are crucial for growth and regulation of metabolic activity in flies, functions analogous to those of mammalian insulin and insulin-like growth factors (IGFs). To identify components functioning in IPCs to control ILP production, we employed genomic and candidate gene approaches. We used laser microdissection and messenger RNA sequencing to characterize the transcriptome of larval IPCs. IPCs highly express many genes homologous to genes active in insulin-producing β-cells of the mammalian pancreas. The genes in common encode ILPs and proteins that control insulin metabolism, storage, secretion, β-cell proliferation, and some not previously linked to insulin production or β-cell function. Among these novelties is unc-104, a kinesin 3 family gene, which is more highly expressed in IPCs compared to most other neurons. Knockdown of unc-104 in IPCs impaired ILP secretion and reduced peripheral insulin signaling. Unc-104 appears to transport ILPs along axons. As a complementary approach, we tested dominant-negative Rab genes to find Rab proteins required in IPCs for ILP production or secretion. Rab1 was identified as crucial for ILP trafficking in IPCs. Inhibition of Rab1 in IPCs increased circulating sugar levels, delayed development, and lowered weight and body size. Immunofluorescence labeling of Rab1 showed its tight association with ILP2 in the Golgi of IPCs. Unc-104 and Rab1 join other proteins required for ILP transport in IPCs.
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Pottekat A, Becker S, Spencer KR, Yates JR, Manning G, Itkin-Ansari P, Balch WE. Insulin biosynthetic interaction network component, TMEM24, facilitates insulin reserve pool release. Cell Rep 2013; 4:921-30. [PMID: 24012759 DOI: 10.1016/j.celrep.2013.07.050] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/16/2013] [Accepted: 07/31/2013] [Indexed: 12/31/2022] Open
Abstract
Insulin homeostasis in pancreatic β cells is now recognized as a critical element in the progression of obesity and type II diabetes (T2D). Proteins that interact with insulin to direct its sequential synthesis, folding, trafficking, and packaging into reserve granules in order to manage release in response to elevated glucose remain largely unknown. Using a conformation-based approach combined with mass spectrometry, we have generated the insulin biosynthetic interaction network (insulin BIN), a proteomic roadmap in the β cell that describes the sequential interacting partners of insulin along the secretory axis. The insulin BIN revealed an abundant C2 domain-containing transmembrane protein 24 (TMEM24) that manages glucose-stimulated insulin secretion from a reserve pool of granules, a critical event impaired in patients with T2D. The identification of TMEM24 in the context of a comprehensive set of sequential insulin-binding partners provides a molecular description of the insulin secretory pathway in β cells.
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Affiliation(s)
- Anita Pottekat
- Department of Cell and Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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Signaling mechanisms of glucose-induced F-actin remodeling in pancreatic islet β cells. Exp Mol Med 2013; 45:e37. [PMID: 23969997 PMCID: PMC3789261 DOI: 10.1038/emm.2013.73] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 12/12/2022] Open
Abstract
The maintenance of whole-body glucose homeostasis is critical for survival, and is controlled by the coordination of multiple organs and endocrine systems. Pancreatic islet β cells secrete insulin in response to nutrient stimuli, and insulin then travels through the circulation promoting glucose uptake into insulin-responsive tissues such as liver, skeletal muscle and adipose. Many of the genes identified in human genome-wide association studies of diabetic individuals are directly associated with β cell survival and function, giving credence to the idea that β-cell dysfunction is central to the development of type 2 diabetes. As such, investigations into the mechanisms by which β cells sense glucose and secrete insulin in a regulated manner are a major focus of current diabetes research. In particular, recent discoveries of the detailed role and requirements for reorganization/remodeling of filamentous actin (F-actin) in the regulation of insulin release from the β cell have appeared at the forefront of islet function research, having lapsed in prior years due to technical limitations. Recent advances in live-cell imaging and specialized reagents have revealed localized F-actin remodeling to be a requisite for the normal biphasic pattern of nutrient-stimulated insulin secretion. This review will provide an historical look at the emergent focus on the role of the actin cytoskeleton and its regulation of insulin secretion, leading up to the cutting-edge research in progress in the field today.
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Ljubicic S, Bezzi P, Brajkovic S, Nesca V, Guay C, Ohbayashi N, Fukuda M, Abderrhamani A, Regazzi R. The GTPase Rab37 Participates in the Control of Insulin Exocytosis. PLoS One 2013; 8:e68255. [PMID: 23826383 PMCID: PMC3694898 DOI: 10.1371/journal.pone.0068255] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 05/27/2013] [Indexed: 01/04/2023] Open
Abstract
Rab37 belongs to a subclass of Rab GTPases regulating exocytosis, including also Rab3a and Rab27a. Proteomic studies indicate that Rab37 is associated with insulin-containing large dense core granules of pancreatic β-cells. In agreement with these observations, we detected Rab37 in extracts of β-cell lines and human pancreatic islets and confirmed by confocal microscopy the localization of the GTPase on insulin-containing secretory granules. We found that, as is the case for Rab3a and Rab27a, reduction of Rab37 levels by RNA interference leads to impairment in glucose-induced insulin secretion and to a decrease in the number of granules in close apposition to the plasma membrane. Pull-down experiments revealed that, despite similar functional effects, Rab37 does not interact with known Rab3a or Rab27a effectors and is likely to operate through a different mechanism. Exposure of insulin-secreting cells to proinflammatory cytokines, fatty acids or oxidized low-density lipoproteins, mimicking physiopathological conditions that favor the development of diabetes, resulted in a decrease in Rab37 expression. Our data identify Rab37 as an additional component of the machinery governing exocytosis of β-cells and suggest that impaired expression of this GTPase may contribute to defective insulin release in pre-diabetic and diabetic conditions.
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Affiliation(s)
- Sanda Ljubicic
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Paola Bezzi
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Saska Brajkovic
- EGID FR 3508, INSERM U859, Université de Lille 2, Lille, France
| | - Valeria Nesca
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Claudiane Guay
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Norihiko Ohbayashi
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | | | - Romano Regazzi
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
- * E-mail:
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Komatsu M, Takei M, Ishii H, Sato Y. Glucose-stimulated insulin secretion: A newer perspective. J Diabetes Investig 2013; 4:511-6. [PMID: 24843702 PMCID: PMC4020243 DOI: 10.1111/jdi.12094] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 03/12/2013] [Indexed: 01/23/2023] Open
Abstract
Existing concepts and models for glucose-stimulated insulin secretion (GSIS) are overviewed and a newer perspective has been formulated toward the physiological understanding of GSIS. A conventional model has been created on the basis of in vitro data on application of a square wave high glucose in the absence of any other stimulatory inputs. Glucose elicits rapid insulin release through an adenosine triphosphate-sensitive K(+) channel (KATP channel)-dependent mechanism, which is gradually augmented in a KATP channel-independent manner. Biphasic GSIS thus occurs. In the body, the β-cells are constantly exposed to stimulatory signals, such as glucagon-like peptide 1 (GLP-1), parasympathetic inputs, free fatty acid (FFA), amino acids and slightly suprathreshold levels of glucose, even at fasting. GLP-1 increases cellular cyclic adenosine monophosphate, parasympathetic stimulation activates protein kinase C, and FFA, amino acids and glucose generate metabolic amplification factors. Plasma glucose concentration gradually rises postprandially under such tonic stimulation. We hypothesize that these stimulatory inputs together make the β-cells responsive to glucose independently from its action on KATP channels. Robust GSIS in patients with a loss of function mutation of the sulfonylurea receptor, a subunit of KATP channels, is compatible with this hypothesis. Furthermore, pre-exposure of the islets to an activator of protein kinase A and/or C makes β-cells responsive to glucose in a KATP channel- and Ca(2+)-independent manner. We hypothesize that GSIS occurs in islet β-cells without glucose regulation of KATP channels in vivo, for which priming with cyclic adenosine monophosphate, protein kinase C and non-glucose nutrients are required. To understand the physiology of GSIS, comprehensive integration of accumulated knowledge is required.
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Affiliation(s)
- Mitsuhisa Komatsu
- Department of Internal Medicine Division of Diabetes, Endocrinology and Metabolism Shinshu University School of Medicine Matsumoto Nagano Japan
| | - Masahiro Takei
- Department of Internal Medicine Division of Diabetes, Endocrinology and Metabolism Shinshu University School of Medicine Matsumoto Nagano Japan
| | - Hiroaki Ishii
- Department of Internal Medicine Division of Diabetes, Endocrinology and Metabolism Shinshu University School of Medicine Matsumoto Nagano Japan
| | - Yoshihiko Sato
- Department of Internal Medicine Division of Diabetes, Endocrinology and Metabolism Shinshu University School of Medicine Matsumoto Nagano Japan
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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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Hasegawa K, Wakino S, Kimoto M, Minakuchi H, Fujimura K, Hosoya K, Komatsu M, Kaneko Y, Kanda T, Tokuyama H, Hayashi K, Itoh H. The hydrolase DDAH2 enhances pancreatic insulin secretion by transcriptional regulation of secretagogin through a Sirt1-dependent mechanism in mice. FASEB J 2013; 27:2301-15. [PMID: 23430976 DOI: 10.1096/fj.12-226092] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The role of dimethylarginine dimethylaminohydrolase 2 (DDAH2) in glucose metabolism is unknown. Here, we generated DDAH2 transgenic (Tg) mice. These mice had lower plasma glucose levels (60 min: 298±32 vs. 418±35 mg/dl; 120 min: 205±15 vs. 284±20 mg/dl) and higher insulin levels (15 min: 2.1±0.2 vs. 1.5±0.1 ng/ml; 30 min: 1.8±0.1 vs. 1.5±0.1 ng/ml) during intraperitoneal glucose tolerance tests when fed a high-fat diet (HFD) compared with HFD-fed wild-type (WT) mice. Glucose-stimulated insulin secretion (GSIS) was increased in Tg islets by 33%. Pancreatic asymmetrical dimethylarginine, nitric oxide, and oxidative stress levels were not correlated with improvements in insulin secretion in Tg mice. Secretagogin, an insulin vesicle docking protein, was up-regulated by 2.7-fold in Tg mice and in pancreatic MIN-6 cells overexpressing DDAH2. GSIS in MIN-6 cells was dependent on DDAH2-induced secretagogin expression. Pancreatic Sirt1, DDAH2, and secretagogin were down-regulated in HFD-fed WT mice by 70, 75, and 85%, respectively. Overexpression of Sirt1 overexpression by 3.9-fold increased DDAH2 and secretagogin expression in MIN-6 cells by 3.2- and 2.5-fold, respectively. DDAH2 overexpression improved GSIS in pancreas-specific Sirt1-deficient mice. In summary, the Sirt1/DDAH2/secretagogin pathway is a novel regulator of GSIS.
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Affiliation(s)
- Kazuhiro Hasegawa
- Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
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42
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Loder MK, Tsuboi T, Rutter GA. Live-cell imaging of vesicle trafficking and divalent metal ions by total internal reflection fluorescence (TIRF) microscopy. Methods Mol Biol 2013; 950:13-26. [PMID: 23086867 DOI: 10.1007/978-1-62703-137-0_2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Total internal reflection fluorescence (TIRF) microscopy is an especially powerful tool for visualizing live cellular events. Fluorescent molecules alone provide broad information about the expression and localization of proteins and other molecules; however, the temporal and spatial resolution is confounded by signal from outside the area of interest and the intensity of the illumination required. TIRF overcomes this limitation by using the reflective properties of a laser beam to illuminate a narrow (<100 nm) strip at the surface of a cell with a relatively low powered evanescent wave, thus making it possible to measure events occurring specifically at the plasma membrane such as exocytosis, single molecule interactions, and ionic changes during signal transduction. Here we describe some of the methods for using TIRF microscopy to study the processes involved in exocytosis from excitable cells (i.e., neurons, endocrine, neuroendocrine, and exocrine cells) and the release of physiologically active substances (i.e., neurotransmitters, hormones, and mucus).The failure of regulated exocytosis is associated with various diseases such as allergy, brain dysfunction, and endocrine illness. Diabetes mellitus, which is due to an absolute (type I) or relative (type II) deficiency of insulin secretion from pancreatic β-cells, is a major area of therapeutic interest. Insulin is stored in dense core vesicles with Zn(2+) ions in pancreatic β-cells. Insulin secretion is regulated by plasma glucose concentration which acts through intracellular metabolism to influence intracellular [Ca(2+)]. However, the precise molecular mechanisms controlling insulin granule movement towards, and fusion at, the plasma membrane remain only partially understood. To tackle this problem, we have used live cell imaging techniques to image regulated exocytosis in single living β-cells alongside intracellular Ca(2+) and Zn(2+) concentrations.
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Affiliation(s)
- Merewyn K Loder
- Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London, UK
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Wang H, Ishizaki R, Xu J, Kasai K, Kobayashi E, Gomi H, Izumi T. The Rab27a effector exophilin7 promotes fusion of secretory granules that have not been docked to the plasma membrane. Mol Biol Cell 2012; 24:319-30. [PMID: 23223571 PMCID: PMC3564536 DOI: 10.1091/mbc.e12-04-0265] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Recent microscopic recordings in living cells demonstrated that granules without prior stable docking to the plasma membrane can efficiently undergo exocytosis, although the molecular mechanism is unknown. The present report is the first to identify exophilin7 as a molecule that functions in the exocytosis of undocked granules. Granuphilin, an effector of the small GTPase Rab27a, mediates the stable attachment (docking) of insulin granules to the plasma membrane and inhibits subsequent fusion of docked granules, possibly through interaction with a fusion-inhibitory Munc18-1/syntaxin complex. However, phenotypes of insulin exocytosis differ considerably between Rab27a- and granuphilin-deficient pancreatic β cells, suggesting that other Rab27a effectors function in those cells. We found that one of the putative Rab27a effector family proteins, exophilin7/JFC1/Slp1, is expressed in β cells; however, unlike granuphilin, exophilin7 overexpressed in the β-cell line MIN6 failed to show granule-docking or fusion-inhibitory activity. Furthermore, exophilin7 has no affinities to either Munc18-1 or Munc18-1–interacting syntaxin-1a, in contrast to granuphilin. Although β cells of exophilin7-knockout mice show no apparent abnormalities in intracellular distribution or in ordinary glucose-induced exocytosis of insulin granules, they do show impaired fusion in response to some stronger stimuli, specifically from granules that have not been docked to the plasma membrane. Exophilin7 appears to mediate the fusion of undocked granules through the affinity of its C2A domain toward the plasma membrane phospholipids. These findings indicate that the two Rab27a effectors, granuphilin and exophilin7, differentially regulate the exocytosis of either stably or minimally docked granules, respectively.
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Affiliation(s)
- Hao Wang
- Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan
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44
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Song L, Xia W, Zhou Z, Li Y, Lin Y, Wei J, Wei Z, Xu B, Shen J, Li W, Xu S. Low-level phenolic estrogen pollutants impair islet morphology and β-cell function in isolated rat islets. J Endocrinol 2012; 215:303-11. [PMID: 22946080 DOI: 10.1530/joe-12-0219] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Phenolic estrogen pollutants, a class of typical endocrine-disrupting chemicals, have attracted public attention due to their estrogenic activities of imitating steroid hormone 17β-estradiol (E(2)) effects. Exposure to these pollutants may disrupt insulin secretion and be a risk factor for type 2 diabetes. In this study, we investigated the direct effects of phenolic estrogen diethylstilbestrol (DES), octylphenol (OP), nonylphenol (NP), and bisphenol A (BPA) on rat pancreatic islets in vitro, whose estrogenic activities were DES>NP>OP>BPA. Isolated β-cells were exposed to E(2), DES, OP, NP, or BPA (0, 0.1, 0.5, 2.5, 25, and 250 μg/l) for 24 h. Parameters of insulin secretion, content, and morphology of β-cells were measured. In the glucose-stimulated insulin secretion test, E(2) and DES increased insulin secretion in a dose-dependent manner in a 16.7 mM glucose condition. However, for BPA, NP, or OP with lower estrogenic activity, the relationship between the doses and insulin secretion was an inverted U-shape. Moreover, OP, NP, or BPA (25 μg/l) impaired mitochondrial function in β-cells and induced remarkable swelling of mitochondria with loss of distinct cristae structure within the membrane, which was accompanied by disruption of mRNA expression of genes playing a key role in β-cell function (Glut2 (Slc2a2), Gck, Pdx1, Hnf1α, Rab27a, and Snap25), and mitochondrial function (Ucp2 and Ogdh). Therefore, these phenolic estrogens can disrupt islet morphology and β-cell function, and mitochondrial dysfunction is suggested to play an important role in the impairment of β-cell function.
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Affiliation(s)
- Liqiong Song
- Key Laboratory of Environment and Health, Ministry of Education, School of Public Health, Tongji Medical College, Wuhan, China
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45
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Hong SW, Lee J, Park SE, Rhee EJ, Park CY, Oh KW, Park SW, Lee WY. Repression of sterol regulatory element-binding protein 1-c is involved in the protective effects of exendin-4 in pancreatic β-cell line. Mol Cell Endocrinol 2012; 362:242-52. [PMID: 22820130 DOI: 10.1016/j.mce.2012.07.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 06/06/2012] [Accepted: 07/10/2012] [Indexed: 02/07/2023]
Abstract
Exendin-4 (Ex-4), a long-acting agonist of glucagon-like peptide-1 receptor, is a novel anti-diabetic drug that prevents β-cells against various toxicities. However, the mechanism and molecules mediating the protection procession of Ex-4 are not fully understood. We investigated the protective effect of Ex-4 against lipotoxicity, mediated by a repression of sterol regulatory element-binding protein (SREBP)-1c, a regulator of genes expression involved in fat and cholesterol synthesis. To observe the effect of Ex-4, we evaluated glucose-stimulated insulin secretion (GSIS) and apoptosis in the MIN6 pancreatic β-cell line, which were cultured in DMEM medium containing 500 μM palmitate, with or without 10 nM Ex-4. We also examined the roles of SREBP-1c in lipotoxicity model by knockdown with si-RNA. Treatment with Ex-4 improved insulin secretion and survival as well as reduced SREBP-1c expression and activity in palmitate-treated MIN6 cells. This improvement was accompanied with an upregulation of PI3K/Akt signaling pathway, and LY294.002, a specific inhibitor of PI3 kinase, abrogated effects of Ex-4 on insulin secretion. Moreover, SREBP-1c in nuclei was increased by the inhibition of PI3 kinase. Lipotoxic effects of palmitate in the insulin secretion and apoptosis were significantly prevented by SREBP-1 knockdown. In conclusion, Ex-4 protects β-cell against palmitate-induced β-cell dysfunction and apoptosis, by inhibiting SREBP-1c expression and activity through the PI3K/Akt signaling pathway.
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Affiliation(s)
- Seok-Woo Hong
- Institute of Medical Research, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
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Arora DK, Syed I, Machhadieh B, McKenna CE, Kowluru A. Rab-geranylgeranyl transferase regulates glucose-stimulated insulin secretion from pancreatic β cells. Islets 2012; 4:354-8. [PMID: 23114750 PMCID: PMC3524143 DOI: 10.4161/isl.22538] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
A growing body of evidence implicates essential roles for small molecular weight G-proteins (e.g., Cdc42, Rac1, Arf6 and Rab3A and Rab27A) in islet β-cell function including glucose-stimulated insulin secretion (GSIS). One of the known mechanisms for optimal activation of small G-proteins involves post-translational prenylation, which is mediated by farnesyltransferase (FTase) and geranylgeranyl transferases (GGTases I and II). The FTase catalyzes incorporation of a 15-carbon farnesyl group while the GGTase mediates incorporation of a 20-carbon geranylgeranyl group into the C-terminal cysteines of G-proteins. The FTase, GGTase I and GGTase II prenylate Ras, Cdc42/Rac1, and Rab G-proteins, respectively. While considerable evidence exists on FTase/GGTase I-mediated regulation of GSIS, very little is known about GGTase II (also referred to as Rab GGTase; RGGT) and its regulatory proteins in the cascade of events leading to GSIS. Herein, we provide the first immunological evidence to suggest expression of α- and β-subunits of RGGT in clonal INS 832/13 β-cells, normal rat islets and human islets. Furthermore, Rab escort protein1 (REP1), which has been shown to be critical for prenylation of Rab G-proteins, is also expressed in these cells. Furthermore, evidence is presented to suggest that siRNA-mediated knockdown of α- or β-subunits of RGGT and REP1 markedly attenuates GSIS in INS 832/13 cells. These findings provide the first evidence in support of key roles for RGGT and its regulatory proteins in GSIS.
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Affiliation(s)
- Daleep K. Arora
- Department of Pharmaceutical Sciences; Wayne State University; Detroit, MI USA
| | - Ismail Syed
- Division of Endocrinology; Diabetes and Metabolism; Department of Medicine; Beth Israel Deaconess Medical Center and Harvard Medical School; Boston, MA USA
| | - Baker Machhadieh
- Division of Endocrinology; Wayne State University; Detroit, MI USA
| | - Charles E. McKenna
- Department of Chemistry; University of Southern California; Los Angeles, CA USA
| | - Anjaneyulu Kowluru
- Department of Pharmaceutical Sciences; Wayne State University; Detroit, MI USA
- Division of Endocrinology; Wayne State University; Detroit, MI USA
- Beta-Cell Biochemistry Laboratory; John D. Dingell VA Medical Center; Detroit, MI USA
- Correspondence to: Anjan Kowluru;
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Direnzo D, Hess DA, Damsz B, Hallett JE, Marshall B, Goswami C, Liu Y, Deering T, Macdonald RJ, Konieczny SF. Induced Mist1 expression promotes remodeling of mouse pancreatic acinar cells. Gastroenterology 2012; 143:469-80. [PMID: 22510200 PMCID: PMC3664941 DOI: 10.1053/j.gastro.2012.04.011] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 03/23/2012] [Accepted: 04/10/2012] [Indexed: 12/31/2022]
Abstract
BACKGROUND & AIMS Early embryogenesis involves cell fate decisions that define the body axes and establish pools of progenitor cells. Development does not stop once lineages are specified; cells continue to undergo specific maturation events, and changes in gene expression patterns lead to their unique physiological functions. Secretory pancreatic acinar cells mature postnatally to synthesize large amounts of protein, polarize, and communicate with other cells. The transcription factor MIST1 is expressed by only secretory cells and regulates maturation events. MIST1-deficient acinar cells in mice do not establish apical-basal polarity, properly position zymogen granules, or communicate with adjacent cells, disrupting pancreatic function. We investigated whether MIST1 directly induces and maintains the mature phenotype of acinar cells. METHODS We analyzed the effects of Cre-mediated expression of Mist1 in adult Mist1-deficient (Mist1(KO)) mice. Pancreatic tissues were collected and analyzed by light and electron microscopy, immunohistochemistry, real-time polymerase chain reaction analysis, and chromatin immunoprecipitation. Primary acini were isolated from mice and analyzed in amylase secretion assays. RESULTS Induced expression of Mist1 in adult Mist1(KO) mice restored wild-type gene expression patterns in acinar cells. The acinar cells changed phenotypes, establishing apical-basal polarity, increasing the size of zymogen granules, reorganizing the cytoskeletal network, communicating intercellularly (by synthesizing gap junctions), and undergoing exocytosis. CONCLUSIONS The exocrine pancreas of adult mice can be remodeled by re-expression of the transcription factor MIST1. MIST1 regulates acinar cell maturation and might be used to repair damaged pancreata in patients with pancreatic disorders.
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Affiliation(s)
- Daniel Direnzo
- Department of Biological Sciences and the Purdue Center for Cancer Research, Purdue University, West Lafayette, Indiana
| | - David A. Hess
- Department of Biological Sciences and the Purdue Center for Cancer Research, Purdue University, West Lafayette, Indiana
| | - Barbara Damsz
- Department of Biological Sciences and the Purdue Center for Cancer Research, Purdue University, West Lafayette, Indiana
| | - Judy E. Hallett
- Department of Biological Sciences and the Purdue Center for Cancer Research, Purdue University, West Lafayette, Indiana
| | - Brett Marshall
- Department of Biological Sciences and the Purdue Center for Cancer Research, Purdue University, West Lafayette, Indiana
| | - Chirayu Goswami
- Laboratory for Computational Genomics, Indiana University School of Medicine, Indianapolis, Indiana
| | - Yunlong Liu
- Laboratory for Computational Genomics, Indiana University School of Medicine, Indianapolis, Indiana
| | - Tye Deering
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Raymond J. Macdonald
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Stephen F. Konieczny
- Department of Biological Sciences and the Purdue Center for Cancer Research, Purdue University, West Lafayette, Indiana
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Li J, Song J, Cassidy MG, Rychahou P, Starr ME, Liu J, Li X, Epperly G, Weiss HL, Townsend CM, Gao T, Evers BM. PI3K p110α/Akt signaling negatively regulates secretion of the intestinal peptide neurotensin through interference of granule transport. Mol Endocrinol 2012; 26:1380-93. [PMID: 22700584 DOI: 10.1210/me.2012-1024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Neurotensin (NT), an intestinal peptide secreted from N cells in the small bowel, regulates a variety of physiological functions of the gastrointestinal tract, including secretion, gut motility, and intestinal growth. The class IA phosphatidylinositol 3-kinase (PI3K) family, which comprised of p110 catalytic (α, β and δ) and p85 regulatory subunits, has been implicated in the regulation of hormone secretion from endocrine cells. However, the underlying mechanisms remain poorly understood. In particular, the role of PI3K in intestinal peptide secretion is not known. Here, we show that PI3K catalytic subunit, p110α, negatively regulates NT secretion in vitro and in vivo. We demonstrate that inhibition of p110α, but not p110β, induces NT release in BON, a human endocrine cell line, which expresses NT mRNA and produces NT peptide in a manner analogous to N cells, and QGP-1, a pancreatic endocrine cell line that produces NT peptide. In contrast, overexpression of p110α decreases NT secretion. Consistently, p110α-inhibition increases plasma NT levels in mice. To further delineate the mechanisms contributing to this effect, we demonstrate that inhibition of p110α increases NT granule trafficking by up-regulating α-tubulin acetylation; NT secretion is prevented by overexpression of HDAC6, an α-tubulin deacetylase. Moreover, ras-related protein Rab27A (a small G protein) and kinase D-interacting substrate of 220 kDa (Kidins220), which are associated with NT granules, play a negative and positive role, respectively, in p110α-inhibition-induced NT secretion. Our findings identify the critical role and novel mechanisms for the PI3K signaling pathway in the control of intestinal hormone granule transport and release.
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Affiliation(s)
- Jing Li
- Department of Surgery, University of Kentucky, Lexington, Kentucky, USA
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Salter NW, Ande SR, Nguyen HK, Nyomba BLG, Mishra S. Functional characterization of naturally occurring transglutaminase 2 mutants implicated in early-onset type 2 diabetes. J Mol Endocrinol 2012; 48:203-16. [PMID: 22394545 DOI: 10.1530/jme-11-0064] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Transglutaminase 2 (TG2) is an enzyme with diverse biological functions. TG2 catalyzes transamidation reactions, has intrinsic kinase activity, and acts as a G-protein in intracellular signaling. TG2 (Tgm2)-null mice are glucose intolerant and have impaired glucose-stimulated insulin secretion (GSIS). Furthermore, three naturally occurring missense mutations in the human TGM2 gene, corresponding to amino acid substitutions of Met330Arg, Ile331Asn, and Asn333Ser in the TG2 protein, have been reported and found to be associated with early-onset type 2 diabetes. However, their effect on TG2 function is not fully understood. To determine this, we have reproduced naturally occurring mutations in TG2 using site-directed mutagenesis. Overexpression of Myc-TG2 mutants in INS-1E cells resulted in a reduction of GSIS in comparison with cells overexpressing wild-type Myc-TG2 (WT-TG2). The maximum reduction was found in cells overexpressing Ile331Asn-TG2 (32%) followed by Met330Arg-TG2 (20%), and the least in Asn333Ser-TG2 (7%). Enzymatic analysis revealed that TG2 mutants have impaired transamidation and kinase activities in comparison with WT-TG2. GTP-binding assays showed that TG2 mutants also have altered GTP-binding ability, which is found to be modulated in response to glucose stimulation. Collectively, these data suggest that naturally occurring mutations in TG2 affect transamidation, kinase, and GTP-binding functions of TG2. While reduced insulin secretion, as a result of naturally occurring mutations in TG2, is due to the impairment of more than one biological function of TG2, it is the transamidation function that appears to be impaired during the first phase, whereas the GTP-binding function affects the second phase of insulin secretion.
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Affiliation(s)
- Neil W Salter
- Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada
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Csépányi-Kömi R, Lévay M, Ligeti E. Small G proteins and their regulators in cellular signalling. Mol Cell Endocrinol 2012; 353:10-20. [PMID: 22108439 DOI: 10.1016/j.mce.2011.11.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Revised: 09/27/2011] [Accepted: 11/07/2011] [Indexed: 01/04/2023]
Abstract
Small molecular weight GTPases (small G proteins) are essential in the transduction of signals from different plasma membrane receptors. Due to their endogenous GTP-hydrolyzing activity, these proteins function as time-dependent biological switches controlling diverse cellular functions including cell shape and migration, cell proliferation, gene transcription, vesicular transport and membrane-trafficking. This review focuses on endocrine diseases linked to small G proteins. We provide examples for the regulation of the activity of small G proteins by various mechanisms such as posttranslational modifications, guanine nucleotide exchange factors (GEFs), GTPase activating proteins (GAPs) or guanine nucleotide dissociation inhibitors (GDIs). Finally we summarize endocrine diseases where small G proteins or their regulatory proteins have been revealed as the cause.
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Affiliation(s)
- Roland Csépányi-Kömi
- Department of Physiology, Semmelweis University, Tűzoltó u. 37-47, 1094 Budapest, Hungary
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