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Taneera J, Khalique A, Abdrabh S, Mohammed AK, Bouzid A, El-Huneidi W, Bustanji Y, Sulaiman N, Albasha S, Saber-Ayad M, Hamad M. Fat mass and obesity-associated (FTO) gene is essential for insulin secretion and β-cell function: In vitro studies using INS-1 cells and human pancreatic islets. Life Sci 2024; 339:122421. [PMID: 38232799 DOI: 10.1016/j.lfs.2024.122421] [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: 06/22/2023] [Revised: 12/21/2023] [Accepted: 01/08/2024] [Indexed: 01/19/2024]
Abstract
AIMS In this study, we investigated the role of the FTO gene in pancreatic β-cell biology and its association with type 2 diabetes (T2D). To address this issue, human pancreatic islets and rat INS-1 (832/13) cells were used to perform gene silencing, overexpression, and functional analysis of FTO expression; levels of FTO were also measured in serum samples obtained from diabetic and obese individuals. RESULTS The findings revealed that FTO expression was reduced in islets from hyperglycemic/diabetic donors compared to normal donors. This reduction correlated with decreased INS and GLUT1 expression and increased PDX1, GCK, and SNAP25 expression. Silencing of Fto in INS-1 cells impaired insulin release and mitochondrial ATP production and increased apoptosis in pro-apoptotic cytokine-treated cells. However, glucose uptake and reactive oxygen species production rates remained unaffected. Downregulation of key β-cell genes was observed following Fto-silencing, while Glut2 and Gck were unaffected. RNA-seq analysis identified several dysregulated genes involved in metal ion binding, calcium ion binding, and protein serine/threonine kinase activity. Furthermore, our findings showed that Pdx1 or Mafa-silencing did not influence FTO protein expression. Overexpression of FTO in human islets promoted insulin secretion and upregulated INS, PDX1, MAFA, and GLUT1 expression. Serum FTO levels did not significantly differ between individuals with diabetes or obesity and their healthy counterparts. CONCLUSION These findings suggest that FTO plays a crucial role in β-cell survival, metabolism, and function and point to a potential therapeutic utility of FTO in T2D patients.
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Affiliation(s)
- Jalal Taneera
- College of Medicine, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates; Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates; Center of Excellence of Precision Medicine, Research Institute of Medical and Health Sciences, University of Sharjah, United Arab Emirates.
| | - Anila Khalique
- Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates
| | - Sham Abdrabh
- Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates
| | - Abdul Khader Mohammed
- Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates
| | - Amal Bouzid
- Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates
| | - Waseem El-Huneidi
- College of Medicine, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates; Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates
| | - Yasser Bustanji
- College of Medicine, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates; Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates; School of Pharmacy, The University of Jordan, Amman 11942, Jordan
| | - Nabil Sulaiman
- College of Medicine, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates; Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates
| | - Sarah Albasha
- Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates
| | - Maha Saber-Ayad
- College of Medicine, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates; Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates
| | - Mawieh Hamad
- Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates; College of Health Sciences, University of Sharjah, Sharjah, P.O. Box 27272, United Arab Emirates
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Chen X, Xie X, Li J, Sun L, Lv Z, Yao X, Li L, Jin H, Cui S, Liu J. BCAS2 Participates in Insulin Synthesis and Secretion via mRNA Alternative Splicing in Mice. Endocrinology 2023; 165:bqad152. [PMID: 37820033 DOI: 10.1210/endocr/bqad152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Revised: 09/22/2023] [Accepted: 10/09/2023] [Indexed: 10/13/2023]
Abstract
Insulin secreted by pancreatic β cells is essential for maintaining blood glucose levels. Diabetes is caused primarily by a loss of β cells or impairment of β-cell function. A previous whole-transcriptome analysis of islets from a type 2 diabetes group and a control group showed that a splicing disorder occurred in approximately 25% of splicing events. Breast carcinoma amplified sequence 2 (BCAS2) is a spliceosome component whose function in islet β cells is unclear. Here, we report that knockdown of Bcas2 decreased glucose- and KCl-stimulated insulin secretion in the NIT-1 cell line. Pancreas weight, glucose tolerance, and insulin sensitivity were measured in normal chow-fed Bcas2 f/f-βKO mice, and β-cell mass and islet size were analyzed by immunohistochemistry. Glucose intolerance developed in Bcas2 f/f-βKO mice, but there were no significant differences in pancreas weight, insulin sensitivity, β-cell mass, or islet size. Furthermore, observation of glucose-stimulated insulin secretion and insulin secretion granules in normal chow-fed mice revealed that the insulin level in serum and the number of insulin secretion granules were decreased in Bcas2 f/f-βKO mice. These differences were related to abnormal splicing of Syt7 and Tcf7l2 pre-mRNA. Taken together, these results demonstrate that BCAS2 is involved in alternative splicing during insulin synthesis and secretion.
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Affiliation(s)
- Xuexue Chen
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Xiaomei Xie
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Jianhua Li
- Reproductive Medical Center, Department of Obstetrics and Gynecology, the Seventh Medical Center of PLA General Hospital, Beijing 100007, China
| | - Longjie Sun
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Zheng Lv
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Xiaohong Yao
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Lei Li
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Hua Jin
- Department of Pathology, the Seventh Medical Center of PLA General Hospital, Beijing 100007, China
| | - Sheng Cui
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, China
| | - Jiali Liu
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing 100193, China
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3
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Vanheer L, Fantuzzi F, To SK, Schiavo A, Van Haele M, Ostyn T, Haesen T, Yi X, Janiszewski A, Chappell J, Rihoux A, Sawatani T, Roskams T, Pattou F, Kerr-Conte J, Cnop M, Pasque V. Inferring regulators of cell identity in the human adult pancreas. NAR Genom Bioinform 2023; 5:lqad068. [PMID: 37435358 PMCID: PMC10331937 DOI: 10.1093/nargab/lqad068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 06/17/2023] [Accepted: 06/28/2023] [Indexed: 07/13/2023] Open
Abstract
Cellular identity during development is under the control of transcription factors that form gene regulatory networks. However, the transcription factors and gene regulatory networks underlying cellular identity in the human adult pancreas remain largely unexplored. Here, we integrate multiple single-cell RNA-sequencing datasets of the human adult pancreas, totaling 7393 cells, and comprehensively reconstruct gene regulatory networks. We show that a network of 142 transcription factors forms distinct regulatory modules that characterize pancreatic cell types. We present evidence that our approach identifies regulators of cell identity and cell states in the human adult pancreas. We predict that HEYL, BHLHE41 and JUND are active in acinar, beta and alpha cells, respectively, and show that these proteins are present in the human adult pancreas as well as in human induced pluripotent stem cell (hiPSC)-derived islet cells. Using single-cell transcriptomics, we found that JUND represses beta cell genes in hiPSC-alpha cells. BHLHE41 depletion induced apoptosis in primary pancreatic islets. The comprehensive gene regulatory network atlas can be explored interactively online. We anticipate our analysis to be the starting point for a more sophisticated dissection of how transcription factors regulate cell identity and cell states in the human adult pancreas.
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Affiliation(s)
| | | | - San Kit To
- Department of Development and Regeneration; KU Leuven - University of Leuven; Single-cell Omics Institute and Leuven Stem Cell Institute, Herestraat 49, B-3000 Leuven, Belgium
| | - Andrea Schiavo
- ULB Center for Diabetes Research; Université Libre de Bruxelles; Route de Lennik 808, B-1070 Brussels, Belgium
| | - Matthias Van Haele
- Department of Imaging and Pathology; Translational Cell and Tissue Research, KU Leuven and University Hospitals Leuven; Herestraat 49, B-3000 Leuven, Belgium
| | - Tessa Ostyn
- Department of Imaging and Pathology; Translational Cell and Tissue Research, KU Leuven and University Hospitals Leuven; Herestraat 49, B-3000 Leuven, Belgium
| | - Tine Haesen
- Department of Development and Regeneration; KU Leuven - University of Leuven; Single-cell Omics Institute and Leuven Stem Cell Institute, Herestraat 49, B-3000 Leuven, Belgium
| | - Xiaoyan Yi
- ULB Center for Diabetes Research; Université Libre de Bruxelles; Route de Lennik 808, B-1070 Brussels, Belgium
| | - Adrian Janiszewski
- Department of Development and Regeneration; KU Leuven - University of Leuven; Single-cell Omics Institute and Leuven Stem Cell Institute, Herestraat 49, B-3000 Leuven, Belgium
| | - Joel Chappell
- Department of Development and Regeneration; KU Leuven - University of Leuven; Single-cell Omics Institute and Leuven Stem Cell Institute, Herestraat 49, B-3000 Leuven, Belgium
| | - Adrien Rihoux
- Department of Development and Regeneration; KU Leuven - University of Leuven; Single-cell Omics Institute and Leuven Stem Cell Institute, Herestraat 49, B-3000 Leuven, Belgium
| | - Toshiaki Sawatani
- ULB Center for Diabetes Research; Université Libre de Bruxelles; Route de Lennik 808, B-1070 Brussels, Belgium
| | - Tania Roskams
- Department of Imaging and Pathology; Translational Cell and Tissue Research, KU Leuven and University Hospitals Leuven; Herestraat 49, B-3000 Leuven, Belgium
| | - Francois Pattou
- University of Lille, Inserm, CHU Lille, Institute Pasteur Lille, U1190-EGID, F-59000 Lille, France
- European Genomic Institute for Diabetes, F-59000 Lille, France
- University of Lille, F-59000 Lille, France
| | - Julie Kerr-Conte
- University of Lille, Inserm, CHU Lille, Institute Pasteur Lille, U1190-EGID, F-59000 Lille, France
- European Genomic Institute for Diabetes, F-59000 Lille, France
- University of Lille, F-59000 Lille, France
| | - Miriam Cnop
- Correspondence may also be addressed to Miriam Cnop. Tel: +32 2 555 6305; Fax: +32 2 555 6239;
| | - Vincent Pasque
- To whom correspondence should be addressed. Tel: +32 16 376283; Fax: +32 16 330827;
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4
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Saeed R, Mohammed AK, Saleh SE, Aboshanab KM, Aboulwafa MM, Taneera J. Expression Silencing of Mitogen-Activated Protein Kinase 8 Interacting Protein-1 Conferred Its Role in Pancreatic β-Cell Physiology and Insulin Secretion. Metabolites 2023; 13:metabo13020307. [PMID: 36837926 PMCID: PMC9964862 DOI: 10.3390/metabo13020307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/11/2023] [Accepted: 02/16/2023] [Indexed: 02/22/2023] Open
Abstract
Mitogen-activated protein kinase 8 interacting protein-1 (MAPK8IP1) gene has been recognized as a susceptibility gene for diabetes. However, its action in the physiology of pancreatic β-cells is not fully understood. Herein, bioinformatics and genetic analyses on the publicly available database were performed to map the expression of the MAPK8IP1 gene in human pancreatic islets and to explore whether this gene contains any genetic variants associated with type 2 diabetes (T2D). Moreover, a series of functional experiments were executed in a rat insulinoma cell line (INS-1 832/13) to investigate the role of the Mapk8ip1 gene in β-cell function. Metabolic engineering using RNA-sequencing (RNA-seq) data confirmed higher expression levels of MAPK8IP1 in human islets compared to other metabolic tissues. Additionally, comparable expression of MAPK8IP1 expression was detected in sorted human endocrine cells. However, β-cells exhibited higher expression of MAPK8IP1 than ductal and PSC cells. Notably, MAPK8IP1 expression was reduced in diabetic islets, and the expression was positively correlated with insulin and the β-cell transcription factor PDX1 and MAFA. Using the TIGER portal, we found that one genetic variant, "rs7115753," in the proximity of MAPK8IP1, passes the genome-wide significance for the association with T2D. Expression silencing of Mapk8ip1 by small interfering RNA (siRNA) in INS-1 cells reduced insulin secretion, glucose uptake rate, and reactive oxygen species (ROS) production. In contrast, insulin content, cell viability, and apoptosis without cytokines were unaffected. However, silencing of Mapk8ip1 reduced cytokines-induced apoptosis and downregulated the expression of several pancreatic β-cell functional markers including, Ins1, Ins2, Pdx1, MafA, Glut2, Gck, Insr, Vamp2, Syt5, and Cacna1a at mRNA and/or protein levels. Finally, we reported that siRNA silencing of Pdx1 resulted in the downregulation of MAPK8IP1 expression in INS-1 cells. In conclusion, our findings confirmed that MAPK8IP1 is an important component of pancreatic β-cell physiology and insulin secretion.
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Affiliation(s)
- Rania Saeed
- Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo 11566, Egypt
- Sharjah Institute for Medical Research, University of Sharjah, Sharjah 27272, United Arab Emirates
| | - Abdul Khader Mohammed
- Sharjah Institute for Medical Research, University of Sharjah, Sharjah 27272, United Arab Emirates
| | - Sarra E. Saleh
- Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo 11566, Egypt
| | - Khaled M. Aboshanab
- Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo 11566, Egypt
- Correspondence: (K.M.A.); (J.T.); Tel.: +20-10075-82620 (K.M.A.); +971-6505-7743 (J.T.)
| | - Mohammad M. Aboulwafa
- Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo 11566, Egypt
- Faculty of Pharmacy, King Salman International University, Ras-Sudr 46612, Egypt
| | - Jalal Taneera
- Sharjah Institute for Medical Research, University of Sharjah, Sharjah 27272, United Arab Emirates
- Department of Basic Sciences, College of Medicine, University of Sharjah, Sharjah 27272, United Arab Emirates
- Correspondence: (K.M.A.); (J.T.); Tel.: +20-10075-82620 (K.M.A.); +971-6505-7743 (J.T.)
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5
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Yan C, Jiang J, Yang Y, Geng X, Dong W. The function of VAMP2 in mediating membrane fusion: An overview. Front Mol Neurosci 2022; 15:948160. [PMID: 36618823 PMCID: PMC9816800 DOI: 10.3389/fnmol.2022.948160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 12/05/2022] [Indexed: 12/24/2022] Open
Abstract
Vesicle-associated membrane protein 2 (VAMP2, also known as synaptobrevin-2), encoded by VAMP2 in humans, is a key component of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex. VAMP2 combined with syntaxin-1A (SYX-1A) and synaptosome-associated protein 25 (SNAP-25) produces a force that induces the formation of fusion pores, thereby mediating the fusion of synaptic vesicles and the release of neurotransmitters. VAMP2 is largely unstructured in the absence of interaction partners. Upon interaction with other SNAREs, the structure of VAMP2 stabilizes, resulting in the formation of four structural domains. In this review, we highlight the current knowledge of the roles of the VAMP2 domains and the interaction between VAMP2 and various fusion-related proteins in the presynaptic cytoplasm during the fusion process. Our summary will contribute to a better understanding of the roles of the VAMP2 protein in membrane fusion.
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Affiliation(s)
- Chong Yan
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Jie Jiang
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Yuan Yang
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Xiaoqi Geng
- Department of Neurosurgery, Neurosurgical Clinical Research Center of Sichuan Province, Affiliated Hospital of Southwest Medical University, Luzhou, China,*Correspondence: Xiaoqi Geng,
| | - Wei Dong
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China,Wei Dong,
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Ballin M, Griep W, Patel M, Karl M, Mentrup T, Rivera‐Monroy J, Foo B, Schwappach B, Schröder B. The intramembrane proteases
SPPL2a
and
SPPL2b
regulate the homeostasis of selected
SNARE
proteins. FEBS J 2022; 290:2320-2337. [PMID: 36047592 DOI: 10.1111/febs.16610] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 06/28/2022] [Accepted: 08/30/2022] [Indexed: 01/15/2023]
Abstract
Signal peptide peptidase (SPP) and SPP-like (SPPL) aspartyl intramembrane proteases are known to contribute to sequential processing of type II-oriented membrane proteins referred to as regulated intramembrane proteolysis. The ER-resident family members SPP and SPPL2c were shown to also cleave tail-anchored proteins, including selected SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins facilitating membrane fusion events. Here, we analysed whether the related SPPL2a and SPPL2b proteases, which localise to the endocytic or late secretory pathway, are also able to process SNARE proteins. Therefore, we screened 18 SNARE proteins for cleavage by SPPL2a and SPPL2b based on cellular co-expression assays, of which the proteins VAMP1, VAMP2, VAMP3 and VAMP4 were processed by SPPL2a/b demonstrating the capability of these two proteases to proteolyse tail-anchored proteins. Cleavage of the four SNARE proteins was scrutinised at the endogenous level upon SPPL2a/b inhibition in different cell lines as well as by analysing VAMP1-4 levels in tissues and primary cells of SPPL2a/b double-deficient (dKO) mice. Loss of SPPL2a/b activity resulted in an accumulation of VAMP1-4 in a cell type- and tissue-dependent manner, identifying these proteins as SPPL2a/b substrates validated in vivo. Therefore, we propose that SPPL2a/b control cellular levels of VAMP1-4 by initiating the degradation of these proteins, which might impact cellular trafficking.
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Affiliation(s)
- Moritz Ballin
- Biochemical Institute Christian Albrechts University Kiel Kiel Germany
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Wolfram Griep
- Biochemical Institute Christian Albrechts University Kiel Kiel Germany
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Mehul Patel
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Martin Karl
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Torben Mentrup
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
| | - Jhon Rivera‐Monroy
- Department of Molecular Biology University Medical Center Göttingen Göttingen Germany
| | - Brian Foo
- Department of Molecular Biology University Medical Center Göttingen Göttingen Germany
| | - Blanche Schwappach
- Department of Molecular Biology University Medical Center Göttingen Göttingen Germany
| | - Bernd Schröder
- Institute of Physiological Chemistry Technische Universität Dresden Dresden Germany
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7
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Deng K, Thorn P. Presynaptic-like mechanisms and the control of insulin secretion in pancreatic β-cells. Cell Calcium 2022; 104:102585. [DOI: 10.1016/j.ceca.2022.102585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 03/24/2022] [Accepted: 03/26/2022] [Indexed: 12/18/2022]
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Watanabe A, Tanaka A, Koga C, Matsumoto M, Okazaki Y, Kin T, Miyajima A. CD82 is a marker to isolate β cell precursors from human iPS cells and plays a role for the maturation of β cells. Sci Rep 2021; 11:9530. [PMID: 33953224 PMCID: PMC8100138 DOI: 10.1038/s41598-021-88978-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 04/16/2021] [Indexed: 02/07/2023] Open
Abstract
Generation of pancreatic β cells from pluripotent stem cells is a key technology to develop cell therapy for insulin-dependent diabetes and considerable efforts have been made to produce β cells. However, due to multiple and lengthy differentiation steps, production of β cells is often unstable. It is also desirable to eliminate undifferentiated cells to avoid potential risks of tumorigenesis. To isolate β cell precursors from late stage pancreatic endocrine progenitor (EP) cells derived from iPS cells, we have identified CD82, a member of the tetraspanin family. CD82+ cells at the EP stage differentiated into endocrine cells more efficiently than CD82- EP stage cells. We also show that CD82+ cells in human islets secreted insulin more efficiently than CD82- cells. Furthermore, knockdown of CD82 expression by siRNA or inhibition of CD82 by monoclonal antibodies in NGN3+ cells suppressed the function of β cells with glucose-stimulated insulin secretion, suggesting that CD82 plays a role in maturation of EP cells to β cells.
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Affiliation(s)
- Ami Watanabe
- Institute for Quantitative Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan.
- Gene Techno Science Co.,Ltd, Kita 21-jo Nishi 11-chome Kita-ku, Sapporo, 001-0021, Japan.
| | - Anna Tanaka
- Institute for Quantitative Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Chizuko Koga
- Institute for Quantitative Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Masahito Matsumoto
- Graduate School of Medical and Dental Sciences, Department of Biofunction Research, Institute of Biomaterials and Bioenginnering, Tokyo Medical University and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-0062, Japan
| | - Yasushi Okazaki
- Diagnostics and Therapeutics of Intractable Diseases, Graduate School of Medicine, Intractable Disease Research Center, Juntendo University, 2-1-2 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan
| | - Tatsuya Kin
- Clinical Islet Laboratory, University of Alberta Hospital, 210 College Plaza, 8215-112 St, Edmonton, AB, T6G2C8, Canada
| | - Atsushi Miyajima
- Institute for Quantitative Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan.
- Gene Techno Science Co.,Ltd, Kita 21-jo Nishi 11-chome Kita-ku, Sapporo, 001-0021, Japan.
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9
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Isolation and Proteomics of the Insulin Secretory Granule. Metabolites 2021; 11:metabo11050288. [PMID: 33946444 PMCID: PMC8147143 DOI: 10.3390/metabo11050288] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 04/28/2021] [Accepted: 04/28/2021] [Indexed: 12/21/2022] Open
Abstract
Insulin, a vital hormone for glucose homeostasis is produced by pancreatic beta-cells and when secreted, stimulates the uptake and storage of glucose from the blood. In the pancreas, insulin is stored in vesicles termed insulin secretory granules (ISGs). In Type 2 diabetes (T2D), defects in insulin action results in peripheral insulin resistance and beta-cell compensation, ultimately leading to dysfunctional ISG production and secretion. ISGs are functionally dynamic and many proteins present either on the membrane or in the lumen of the ISG may modulate and affect different stages of ISG trafficking and secretion. Previously, studies have identified few ISG proteins and more recently, proteomics analyses of purified ISGs have uncovered potential novel ISG proteins. This review summarizes the proteins identified in the current ISG proteomes from rat insulinoma INS-1 and INS-1E cell lines. Here, we also discuss techniques of ISG isolation and purification, its challenges and potential future directions.
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10
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Undesirable Status of Prostate Cancer Cells after Intensive Inhibition of AR Signaling: Post-AR Era of CRPC Treatment. Biomedicines 2021; 9:biomedicines9040414. [PMID: 33921329 PMCID: PMC8069212 DOI: 10.3390/biomedicines9040414] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 04/07/2021] [Accepted: 04/09/2021] [Indexed: 12/19/2022] Open
Abstract
Recent advances in prostate cancer (PC) research unveiled real androgen receptor (AR) functions in castration-resistant PC (CRPC). Moreover, AR still accelerates PC cell proliferation via the activation of several mechanisms (e.g., mutation, variants, and amplifications in CRPC). New-generation AR signaling-targeted agents, inhibiting extremely the activity of AR, were developed based on these incontrovertible mechanisms of AR-induced CRPC progression. However, long-term administration of AR signaling-targeted agents subsequently induces the major problem that AR (complete)-independent CRPC cells present neither AR nor prostate-specific antigen, including neuroendocrine differentiation as a subtype of AR-independent CRPC. Moreover, there are few treatments effective for AR-independent CRPC with solid evidence. This study focuses on the transformation mechanisms of AR-independent from AR-dependent CRPC cells and potential treatment strategy for AR-independent CRPC and discusses them based on a review of basic and clinical literature.
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11
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Chronically Elevated Exogenous Glucose Elicits Antipodal Effects on the Proteome Signature of Differentiating Human iPSC-Derived Pancreatic Progenitors. Int J Mol Sci 2021; 22:ijms22073698. [PMID: 33918250 PMCID: PMC8038174 DOI: 10.3390/ijms22073698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/22/2021] [Accepted: 03/27/2021] [Indexed: 12/14/2022] Open
Abstract
The past decade revealed that cell identity changes, such as dedifferentiation or transdifferentiation, accompany the insulin-producing β-cell decay in most diabetes conditions. Mapping and controlling the mechanisms governing these processes is, thus, extremely valuable for managing the disease progression. Extracellular glucose is known to influence cell identity by impacting the redox balance. Here, we use global proteomics and pathway analysis to map the response of differentiating human pancreatic progenitors to chronically increased in vitro glucose levels. We show that exogenous high glucose levels impact different protein subsets in a concentration-dependent manner. In contrast, regardless of concentration, glucose elicits an antipodal effect on the proteome landscape, inducing both beneficial and detrimental changes in regard to achieving the desired islet cell fingerprint. Furthermore, we identified that only a subgroup of these effects and pathways are regulated by changes in redox balance. Our study highlights a complex effect of exogenous glucose on differentiating pancreas progenitors characterized by a distinct proteome signature.
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12
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Tang BL. SNAREs and developmental disorders. J Cell Physiol 2020; 236:2482-2504. [PMID: 32959907 DOI: 10.1002/jcp.30067] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 08/20/2020] [Accepted: 09/09/2020] [Indexed: 12/12/2022]
Abstract
Members of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) family mediate membrane fusion processes associated with vesicular trafficking and autophagy. SNAREs mediate core membrane fusion processes essential for all cells, but some SNAREs serve cell/tissue type-specific exocytic/endocytic functions, and are therefore critical for various aspects of embryonic development. Mutations or variants of their encoding genes could give rise to developmental disorders, such as those affecting the nervous system and immune system in humans. Mutations to components in the canonical synaptic vesicle fusion SNARE complex (VAMP2, STX1A/B, and SNAP25) and a key regulator of SNARE complex formation MUNC18-1, produce variant phenotypes of autism, intellectual disability, movement disorders, and epilepsy. STX11 and MUNC18-2 mutations underlie 2 subtypes of familial hemophagocytic lymphohistiocytosis. STX3 mutations contribute to variant microvillus inclusion disease. Chromosomal microdeletions involving STX16 play a role in pseudohypoparathyroidism type IB associated with abnormal imprinting of the GNAS complex locus. In this short review, I discuss these and other SNARE gene mutations and variants that are known to be associated with a variety developmental disorders, with a focus on their underlying cellular and molecular pathological basis deciphered through disease modeling. Possible pathogenic potentials of other SNAREs whose variants could be disease predisposing are also speculated upon.
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Affiliation(s)
- Bor L Tang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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13
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Merriman C, Fu D. Down-regulation of the islet-specific zinc transporter-8 (ZnT8) protects human insulinoma cells against inflammatory stress. J Biol Chem 2019; 294:16992-17006. [PMID: 31591269 DOI: 10.1074/jbc.ra119.010937] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 10/04/2019] [Indexed: 12/31/2022] Open
Abstract
Zinc transporter-8 (ZnT8) primarily functions as a zinc-sequestrating transporter in the insulin-secretory granules (ISGs) of pancreatic β-cells. Loss-of-function mutations in ZnT8 are associated with protection against type-2 diabetes (T2D), but the protective mechanism is unclear. Here, we developed an in-cell ZnT8 assay to track endogenous ZnT8 responses to metabolic and inflammatory stresses applied to human insulinoma EndoC-βH1 cells. Unexpectedly, high glucose and free fatty acids did not alter cellular ZnT8 levels, but proinflammatory cytokines acutely, reversibly, and gradually down-regulated ZnT8. Approximately 50% of the cellular ZnT8 was localized to the endoplasmic reticulum (ER), which was the primary target of the cytokine-mediated ZnT8 down-regulation. Transcriptome profiling of cytokine-exposed β-cells revealed an adaptive unfolded protein response (UPR) including a marked immunoproteasome activation that coordinately degraded ZnT8 and insulin over a 1,000-fold cytokine concentration range. RNAi-mediated ZnT8 knockdown protected cells against cytokine cytotoxicity, whereas inhibiting immunoproteasomes blocked cytokine-induced ZnT8 degradation and triggered a transition of the adaptive UPR to cell apoptosis. Hence, cytokine-induced down-regulation of the ER ZnT8 level promotes adaptive UPR, acting as a protective mechanism that decongests the ER burden of ZnT8 to protect β-cells from proapoptotic UPR during chronic low-grade inflammation.
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Affiliation(s)
- Chengfeng Merriman
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Dax Fu
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
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14
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Fezoua-Boubegtiten Z, Hastoy B, Scotti P, Milochau A, Bathany K, Desbat B, Castano S, Oda R, Lang J. The transmembrane domain of the SNARE protein VAMP2 is highly sensitive to its lipid environment. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:670-676. [DOI: 10.1016/j.bbamem.2018.12.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 11/15/2018] [Accepted: 12/17/2018] [Indexed: 12/12/2022]
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15
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Wang Y, Hao N, Lin H, Wang T, Xie J, Yuan Y. Down-regulation of CASK in glucotoxicity-induced insulin dysfunction in pancreatic β cells. Acta Biochim Biophys Sin (Shanghai) 2018; 50:281-287. [PMID: 29293883 DOI: 10.1093/abbs/gmx139] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 12/08/2017] [Indexed: 12/28/2022] Open
Abstract
High-glucose level exerts deleterious effects on pancreatic β cells, but the mechanisms remain unclear. Calcium/calmodulin-dependent serine protein kinase (CASK) plays a vital role in neural development and release of neurotransmitters, and probably plays a role in the anchoring of insulin on pancreatic β cell membrane. Hypoxia-inducible factor 1α (HIF1α) is involved in β-cell dysfunction. The aim of this study was to provide some basic evidence that CASK could be involved in glucotoxicity-induced insulin secretion dysfunction mediated by HIF1α in INS-1E cells. CASK overexpression plasmid, HIF1α agonist (CoCl2), and HIF1α selective inhibitor (KC7F2) were used. The results showed that chronic stimulation with high glucose could induce insulin secretion dysfunction in INS-1E β cells. Overexpression of CASK partially reversed the effects of high glucose on insulin secretion. CoCl2 reduced the expression of CASK, but KC7F2 reversed the glucotoxicity-induced CASK level reduction. These results suggested that glucotoxicity-induced insulin secretion defects in INS-1E cells could be mediated by HIF1α via the down-regulation of CASK.
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Affiliation(s)
- Yao Wang
- Department of Endocrinology, Zhongda Hospital, Institute of Diabetes, Southeast University, Nanjing 210009, China
| | - Nana Hao
- Department of Endocrinology, Affiliated Fuyang Hospital of Anhui Medical University, Fuyang 236000, China
| | - Haiyan Lin
- Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 211166, China
| | - Tianyuan Wang
- Department of Endocrinology, Zhongda Hospital, Institute of Diabetes, Southeast University, Nanjing 210009, China
| | - Jinyang Xie
- Department of Endocrinology, Zhongda Hospital, Institute of Diabetes, Southeast University, Nanjing 210009, China
| | - Yuexing Yuan
- Department of Endocrinology, Zhongda Hospital, Institute of Diabetes, Southeast University, Nanjing 210009, China
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16
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Hastoy B, Clark A, Rorsman P, Lang J. Fusion pore in exocytosis: More than an exit gate? A β-cell perspective. Cell Calcium 2017; 68:45-61. [PMID: 29129207 DOI: 10.1016/j.ceca.2017.10.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 10/17/2017] [Accepted: 10/24/2017] [Indexed: 12/14/2022]
Abstract
Secretory vesicle exocytosis is a fundamental biological event and the process by which hormones (like insulin) are released into the blood. Considerable progress has been made in understanding this precisely orchestrated sequence of events from secretory vesicle docked at the cell membrane, hemifusion, to the opening of a membrane fusion pore. The exact biophysical and physiological regulation of these events implies a close interaction between membrane proteins and lipids in a confined space and constrained geometry to ensure appropriate delivery of cargo. We consider some of the still open questions such as the nature of the initiation of the fusion pore, the structure and the role of the Soluble N-ethylmaleimide-sensitive-factor Attachment protein REceptor (SNARE) transmembrane domains and their influence on the dynamics and regulation of exocytosis. We discuss how the membrane composition and protein-lipid interactions influence the likelihood of the nascent fusion pore forming. We relate these factors to the hypothesis that fusion pore expansion could be affected in type-2 diabetes via changes in disease-related gene transcription and alterations in the circulating lipid profile. Detailed characterisation of the dynamics of the fusion pore in vitro will contribute to understanding the larger issue of insulin secretory defects in diabetes.
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Affiliation(s)
- Benoit Hastoy
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK.
| | - Anne Clark
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK; Metabolic Research, Institute of Neuroscience and Physiology, University of Goteborg, Medicinaregatan 11, S-41309 Göteborg, Sweden
| | - Jochen Lang
- Laboratoire de Chimie et Biologie des Membranes et Nano-objets (CBMN), CNRS UMR 5248, Université de Bordeaux, Allée de Geoffrey St Hilaire, 33600 Pessac, France.
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17
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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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18
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Hastoy B, Scotti PA, Milochau A, Fezoua-Boubegtiten Z, Rodas J, Megret R, Desbat B, Laguerre M, Castano S, Perrais D, Rorsman P, Oda R, Lang J. A Central Small Amino Acid in the VAMP2 Transmembrane Domain Regulates the Fusion Pore in Exocytosis. Sci Rep 2017; 7:2835. [PMID: 28588281 PMCID: PMC5460238 DOI: 10.1038/s41598-017-03013-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 04/27/2017] [Indexed: 11/30/2022] Open
Abstract
Exocytosis depends on cytosolic domains of SNARE proteins but the function of the transmembrane domains (TMDs) in membrane fusion remains controversial. The TMD of the SNARE protein synaptobrevin2/VAMP2 contains two highly conserved small amino acids, G100 and C103, in its central portion. Substituting G100 and/or C103 with the β-branched amino acid valine impairs the structural flexibility of the TMD in terms of α-helix/β-sheet transitions in model membranes (measured by infrared reflection-absorption or evanescent wave spectroscopy) during increase in protein/lipid ratios, a parameter expected to be altered by recruitment of SNAREs at fusion sites. This structural change is accompanied by reduced membrane fluidity (measured by infrared ellipsometry). The G100V/C103V mutation nearly abolishes depolarization-evoked exocytosis (measured by membrane capacitance) and hormone secretion (measured biochemically). Single-vesicle optical (by TIRF microscopy) and biophysical measurements of ATP release indicate that G100V/C103V retards initial fusion-pore opening, hinders its expansion and leads to premature closure in most instances. We conclude that the TMD of VAMP2 plays a critical role in membrane fusion and that the structural mobility provided by the central small amino acids is crucial for exocytosis by influencing the molecular re-arrangements of the lipid membrane that are necessary for fusion pore opening and expansion.
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Affiliation(s)
- Benoît Hastoy
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.,Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, OX3 7LJ, UK
| | - Pier A Scotti
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Alexandra Milochau
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Zahia Fezoua-Boubegtiten
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Jorge Rodas
- Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.,Laboratoire de l'Intégration du Matériau au Système, UMR CNRS 5218, 351 Cours de la Libération, 33400 Talence, France.,Institut Polytechnique de Bordeaux, Avernue des Facultés, 33405, Talence, France
| | - Rémi Megret
- Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.,Laboratoire de l'Intégration du Matériau au Système, UMR CNRS 5218, 351 Cours de la Libération, 33400 Talence, France.,Institut Polytechnique de Bordeaux, Avernue des Facultés, 33405, Talence, France
| | - Bernard Desbat
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Michel Laguerre
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Sabine Castano
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - David Perrais
- Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.,Interdisciplinary Institute for Neuroscience, UMR CNRS 5287, 146, rue Léo-Saignat, 33077, Bordeaux, France
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, OX3 7LJ, UK
| | - Reiko Oda
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France.,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France
| | - Jochen Lang
- Laboratory of Membrane Chemistry and Biology (CBMN), UMR CNRS 5248, Université de Bordeaux, Allée de Geoffroy St Hilaire, 33600, Pessac, France. .,Université de Bordeaux, 351 Cours de la Libération, 33400, Talence, France.
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19
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Xu Y, Toomre DK, Bogan JS, Hao M. Excess cholesterol inhibits glucose-stimulated fusion pore dynamics in insulin exocytosis. J Cell Mol Med 2017; 21:2950-2962. [PMID: 28544529 PMCID: PMC5661106 DOI: 10.1111/jcmm.13207] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 03/28/2017] [Indexed: 01/06/2023] Open
Abstract
Type 2 diabetes is caused by defects in both insulin sensitivity and insulin secretion. Glucose triggers insulin secretion by causing exocytosis of insulin granules from pancreatic β-cells. High circulating cholesterol levels and a diminished capacity of serum to remove cholesterol from β-cells are observed in diabetic individuals. Both of these effects can lead to cholesterol accumulation in β-cells and contribute to β-cell dysfunction. However, the molecular mechanisms by which cholesterol accumulation impairs β-cell function remain largely unknown. Here, we used total internal reflection fluorescence microscopy to address, at the single-granule level, the role of cholesterol in regulating fusion pore dynamics during insulin exocytosis. We focused particularly on the effects of cholesterol overload, which is relevant to type 2 diabetes. We show that excess cholesterol reduced the number of glucose-stimulated fusion events, and modulated the proportion of full fusion and kiss-and-run fusion events. Analysis of single exocytic events revealed distinct fusion kinetics, with more clustered and compound exocytosis observed in cholesterol-overloaded β-cells. We provide evidence for the involvement of the GTPase dynamin, which is regulated in part by cholesterol-induced phosphatidylinositol 4,5-bisphosphate enrichment in the plasma membrane, in the switch between full fusion and kiss-and-run fusion. Characterization of insulin exocytosis offers insights into the role that elevated cholesterol may play in the development of type 2 diabetes.
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Affiliation(s)
- Yingke Xu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Department of Bioengineering, Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang University, Hangzhou, China
| | - Derek K Toomre
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Jonathan S Bogan
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
| | - Mingming Hao
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.,Department of Biochemistry, Weill Cornell Medical College, New York, NY, USA
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20
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Petrenko V, Saini C, Giovannoni L, Gobet C, Sage D, Unser M, Heddad Masson M, Gu G, Bosco D, Gachon F, Philippe J, Dibner C. Pancreatic α- and β-cellular clocks have distinct molecular properties and impact on islet hormone secretion and gene expression. Genes Dev 2017; 31:383-398. [PMID: 28275001 PMCID: PMC5358758 DOI: 10.1101/gad.290379.116] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 02/02/2017] [Indexed: 01/10/2023]
Abstract
Here, Petrenko et al. present the first integrative analysis of the molecular properties of circadian clocks in α and β pancreatic cells and provide new insights into the complex regulation of islet cell physiology at transcriptional and functional levels. A critical role of circadian oscillators in orchestrating insulin secretion and islet gene transcription has been demonstrated recently. However, these studies focused on whole islets and did not explore the interplay between α-cell and β-cell clocks. We performed a parallel analysis of the molecular properties of α-cell and β-cell oscillators using a mouse model expressing three reporter genes: one labeling α cells, one specific for β cells, and a third monitoring circadian gene expression. Thus, phase entrainment properties, gene expression, and functional outputs of the α-cell and β-cell clockworks could be assessed in vivo and in vitro at the population and single-cell level. These experiments showed that α-cellular and β-cellular clocks are oscillating with distinct phases in vivo and in vitro. Diurnal transcriptome analysis in separated α and β cells revealed that a high number of genes with key roles in islet physiology, including regulators of glucose sensing and hormone secretion, are differentially expressed in these cell types. Moreover, temporal insulin and glucagon secretion exhibited distinct oscillatory profiles both in vivo and in vitro. Altogether, our data indicate that differential entrainment characteristics of circadian α-cell and β-cell clocks are an important feature in the temporal coordination of endocrine function and gene expression.
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Affiliation(s)
- Volodymyr Petrenko
- Endocrinology, Diabetes, Hypertension, and Nutrition, University Hospital of Geneva, CH-1211 Geneva, Switzerland.,Department of Cellular Physiology and Metabolism, Diabetes Center, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland.,Institute of Genetics and Genomics in Geneva (iGE3), University of Geneva, CH-1211 Geneva, Switzerland
| | - Camille Saini
- Endocrinology, Diabetes, Hypertension, and Nutrition, University Hospital of Geneva, CH-1211 Geneva, Switzerland.,Department of Cellular Physiology and Metabolism, Diabetes Center, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland.,Institute of Genetics and Genomics in Geneva (iGE3), University of Geneva, CH-1211 Geneva, Switzerland
| | - Laurianne Giovannoni
- Endocrinology, Diabetes, Hypertension, and Nutrition, University Hospital of Geneva, CH-1211 Geneva, Switzerland.,Department of Cellular Physiology and Metabolism, Diabetes Center, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland.,Institute of Genetics and Genomics in Geneva (iGE3), University of Geneva, CH-1211 Geneva, Switzerland
| | - Cedric Gobet
- Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, CH-1015 Lausanne, Switzerland.,School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Daniel Sage
- Biomedical Imaging Group, EPFL, CH-1015 Lausanne, Switzerland
| | - Michael Unser
- Biomedical Imaging Group, EPFL, CH-1015 Lausanne, Switzerland
| | - Mounia Heddad Masson
- Endocrinology, Diabetes, Hypertension, and Nutrition, University Hospital of Geneva, CH-1211 Geneva, Switzerland
| | - Guoqiang Gu
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37240, USA
| | - Domenico Bosco
- Department of Surgery, Cell Isolation and Transplantation Centre, University Hospital of Geneva, CH-1211 Geneva, Switzerland
| | - Frédéric Gachon
- Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, CH-1015 Lausanne, Switzerland.,School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Jacques Philippe
- Endocrinology, Diabetes, Hypertension, and Nutrition, University Hospital of Geneva, CH-1211 Geneva, Switzerland
| | - Charna Dibner
- Endocrinology, Diabetes, Hypertension, and Nutrition, University Hospital of Geneva, CH-1211 Geneva, Switzerland.,Department of Cellular Physiology and Metabolism, Diabetes Center, Faculty of Medicine, University of Geneva, CH-1211 Geneva, Switzerland.,Institute of Genetics and Genomics in Geneva (iGE3), University of Geneva, CH-1211 Geneva, Switzerland
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21
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Juan-Mateu J, Rech TH, Villate O, Lizarraga-Mollinedo E, Wendt A, Turatsinze JV, Brondani LA, Nardelli TR, Nogueira TC, Esguerra JLS, Alvelos MI, Marchetti P, Eliasson L, Eizirik DL. Neuron-enriched RNA-binding Proteins Regulate Pancreatic Beta Cell Function and Survival. J Biol Chem 2017; 292:3466-3480. [PMID: 28077579 PMCID: PMC5336178 DOI: 10.1074/jbc.m116.748335] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 01/10/2017] [Indexed: 01/05/2023] Open
Abstract
Pancreatic beta cell failure is the central event leading to diabetes. Beta cells share many phenotypic traits with neurons, and proper beta cell function relies on the activation of several neuron-like transcription programs. Regulation of gene expression by alternative splicing plays a pivotal role in brain, where it affects neuronal development, function, and disease. The role of alternative splicing in beta cells remains unclear, but recent data indicate that splicing alterations modulated by both inflammation and susceptibility genes for diabetes contribute to beta cell dysfunction and death. Here we used RNA sequencing to compare the expression of splicing-regulatory RNA-binding proteins in human islets, brain, and other human tissues, and we identified a cluster of splicing regulators that are expressed in both beta cells and brain. Four of them, namely Elavl4, Nova2, Rbox1, and Rbfox2, were selected for subsequent functional studies in insulin-producing rat INS-1E, human EndoC-βH1 cells, and in primary rat beta cells. Silencing of Elavl4 and Nova2 increased beta cell apoptosis, whereas silencing of Rbfox1 and Rbfox2 increased insulin content and secretion. Interestingly, Rbfox1 silencing modulates the splicing of the actin-remodeling protein gelsolin, increasing gelsolin expression and leading to faster glucose-induced actin depolymerization and increased insulin release. Taken together, these findings indicate that beta cells share common splicing regulators and programs with neurons. These splicing regulators play key roles in insulin release and beta cell survival, and their dysfunction may contribute to the loss of functional beta cell mass in diabetes.
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Affiliation(s)
- Jonàs Juan-Mateu
- ULB Center for Diabetes Research, Université Libre de Bruxelles, 1070 Brussels, Belgium.
| | - Tatiana H Rech
- ULB Center for Diabetes Research, Université Libre de Bruxelles, 1070 Brussels, Belgium
| | - Olatz Villate
- ULB Center for Diabetes Research, Université Libre de Bruxelles, 1070 Brussels, Belgium
| | | | - Anna Wendt
- Lund University Diabetes Center, Unit of Islets Cell Exocytosis, Department of Clinical Sciences Malmö, Lund University, SE 205 02 Malmö, Sweden
| | | | - Letícia A Brondani
- ULB Center for Diabetes Research, Université Libre de Bruxelles, 1070 Brussels, Belgium
| | - Tarlliza R Nardelli
- ULB Center for Diabetes Research, Université Libre de Bruxelles, 1070 Brussels, Belgium
| | - Tatiane C Nogueira
- ULB Center for Diabetes Research, Université Libre de Bruxelles, 1070 Brussels, Belgium
| | - Jonathan L S Esguerra
- Lund University Diabetes Center, Unit of Islets Cell Exocytosis, Department of Clinical Sciences Malmö, Lund University, SE 205 02 Malmö, Sweden
| | - Maria Inês Alvelos
- ULB Center for Diabetes Research, Université Libre de Bruxelles, 1070 Brussels, Belgium
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, Islet Cell Laboratory, University of Pisa, 56126 Pisa, Italy
| | - Lena Eliasson
- Lund University Diabetes Center, Unit of Islets Cell Exocytosis, Department of Clinical Sciences Malmö, Lund University, SE 205 02 Malmö, Sweden
| | - Décio L Eizirik
- ULB Center for Diabetes Research, Université Libre de Bruxelles, 1070 Brussels, Belgium; Welbio, Université Libre de Bruxelles, 808 Route de Lennik, CP618, 1070 Brussels, Belgium.
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Kunii M, Ohara-Imaizumi M, Takahashi N, Kobayashi M, Kawakami R, Kondoh Y, Shimizu T, Simizu S, Lin B, Nunomura K, Aoyagi K, Ohno M, Ohmuraya M, Sato T, Yoshimura SI, Sato K, Harada R, Kim YJ, Osada H, Nemoto T, Kasai H, Kitamura T, Nagamatsu S, Harada A. Opposing roles for SNAP23 in secretion in exocrine and endocrine pancreatic cells. J Cell Biol 2016; 215:121-138. [PMID: 27697926 PMCID: PMC5057288 DOI: 10.1083/jcb.201604030] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 08/26/2016] [Indexed: 12/17/2022] Open
Abstract
Kunii et al. reveal that the SNARE protein SNAP23 plays distinct roles in the secretion of amylase in exocrine cells and of insulin in endocrine cells the pancreas and show that MF286, a novel inhibitor of SNAP23, may be a new drug candidate for diabetes. The membrane fusion of secretory granules with plasma membranes is crucial for the exocytosis of hormones and enzymes. Secretion disorders can cause various diseases such as diabetes or pancreatitis. Synaptosomal-associated protein 23 (SNAP23), a soluble N-ethyl-maleimide sensitive fusion protein attachment protein receptor (SNARE) molecule, is essential for secretory granule fusion in several cell lines. However, the in vivo functions of SNAP23 in endocrine and exocrine tissues remain unclear. In this study, we show opposing roles for SNAP23 in secretion in pancreatic exocrine and endocrine cells. The loss of SNAP23 in the exocrine and endocrine pancreas resulted in decreased and increased fusion of granules to the plasma membrane after stimulation, respectively. Furthermore, we identified a low molecular weight compound, MF286, that binds specifically to SNAP23 and promotes insulin secretion in mice. Our results demonstrate opposing roles for SNAP23 in the secretion mechanisms of the endocrine and exocrine pancreas and reveal that the SNAP23-binding compound MF286 may be a promising drug for diabetes treatment.
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Affiliation(s)
- Masataka Kunii
- Laboratory of Molecular Traffic, Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Mica Ohara-Imaizumi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Graduate School of Medicine, Center for Disease Biology and Integrative Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Masaki Kobayashi
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan
| | - Ryosuke Kawakami
- Laboratory of Molecular and Cellular Biophysics, Research Institute for Electronic Science, Hokkaido University, Hokkaido 001-0020, Japan
| | - Yasumitsu Kondoh
- Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, Saitama 351-0198, Japan
| | - Takeshi Shimizu
- Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, Saitama 351-0198, Japan
| | - Siro Simizu
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, Kanagawa 223-8522, Japan
| | - Bangzhong Lin
- Drug Discovery Team, Office for University-Industry Collaboration Planning and Promotion, Osaka University, Osaka 565-0871, Japan
| | - Kazuto Nunomura
- Drug Discovery Team, Office for University-Industry Collaboration Planning and Promotion, Osaka University, Osaka 565-0871, Japan
| | - Kyota Aoyagi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Mitsuyo Ohno
- Laboratory of Structural Physiology, Graduate School of Medicine, Center for Disease Biology and Integrative Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Masaki Ohmuraya
- Institute of Resource Development and Analysis, Kumamoto University, Kumamoto 860-0811, Japan
| | - Takashi Sato
- Laboratory of Molecular Traffic, Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan
| | - Shin-Ichiro Yoshimura
- Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Ken Sato
- Laboratory of Molecular Traffic, Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan
| | - Reiko Harada
- Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan Department of Judo Therapy, Takarazuka University of Medical and Health Care, Hyogo 666-0152, Japan
| | - Yoon-Jeong Kim
- Drug Discovery Team, Office for University-Industry Collaboration Planning and Promotion, Osaka University, Osaka 565-0871, Japan
| | - Hiroyuki Osada
- Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, Saitama 351-0198, Japan
| | - Tomomi Nemoto
- Laboratory of Molecular and Cellular Biophysics, Research Institute for Electronic Science, Hokkaido University, Hokkaido 001-0020, Japan
| | - Haruo Kasai
- Laboratory of Structural Physiology, Graduate School of Medicine, Center for Disease Biology and Integrative Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Tadahiro Kitamura
- Metabolic Signal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan
| | - Shinya Nagamatsu
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Akihiro Harada
- Laboratory of Molecular Traffic, Department of Molecular and Cellular Biology, Institute for Molecular and Cellular Regulation, Gunma University, Gunma 371-8512, Japan Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
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Aoyagi K, Ohara-Imaizumi M, Itakura M, Torii S, Akimoto Y, Nishiwaki C, Nakamichi Y, Kishimoto T, Kawakami H, Harada A, Takahashi M, Nagamatsu S. VAMP7 Regulates Autophagy to Maintain Mitochondrial Homeostasis and to Control Insulin Secretion in Pancreatic β-Cells. Diabetes 2016; 65:1648-59. [PMID: 26953164 DOI: 10.2337/db15-1207] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 03/03/2016] [Indexed: 11/13/2022]
Abstract
VAMP7 is a SNARE protein that mediates specific membrane fusions in intracellular trafficking and was recently reported to regulate autophagosome formation. However, its function in pancreatic β-cells is largely unknown. To elucidate the physiological role of VAMP7 in β-cells, we generated pancreatic β-cell-specific VAMP7 knockout (Vamp7(flox/Y);Cre) mice. VAMP7 deletion impaired glucose-stimulated ATP production and insulin secretion, though VAMP7 was not localized to insulin granules. VAMP7-deficient β-cells showed defective autophagosome formation and reduced mitochondrial function. p62/SQSTM1, a marker protein for defective autophagy, was selectively accumulated on mitochondria in VAMP7-deficient β-cells. These findings suggest that accumulation of dysfunctional mitochondria that are degraded by autophagy caused impairment of glucose-stimulated ATP production and insulin secretion in Vamp7(flox/Y);Cre β-cells. Feeding a high-fat diet to Vamp7(flox/Y);Cre mice exacerbated mitochondrial dysfunction, further decreased ATP production and insulin secretion, and consequently induced glucose intolerance. Moreover, we found upregulated VAMP7 expression in wild-type mice fed a high-fat diet and in db/db mice, a model for diabetes. Thus our data indicate that VAMP7 regulates autophagy to maintain mitochondrial quality and insulin secretion in response to pathological stress in β-cells.
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Affiliation(s)
- Kyota Aoyagi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Mica Ohara-Imaizumi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Makoto Itakura
- Department of Biochemistry, Kitasato University School of Medicine, Kanagawa, Japan
| | - Seiji Torii
- Biosignal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Yoshihiro Akimoto
- Department of Anatomy, Kyorin University School of Medicine, Tokyo, Japan
| | - Chiyono Nishiwaki
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Yoko Nakamichi
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Takuma Kishimoto
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
| | - Hayato Kawakami
- Department of Anatomy, Kyorin University School of Medicine, Tokyo, Japan
| | - Akihiro Harada
- Department of Cell Biology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Masami Takahashi
- Department of Biochemistry, Kitasato University School of Medicine, Kanagawa, Japan
| | - Shinya Nagamatsu
- Department of Biochemistry, Kyorin University School of Medicine, Tokyo, Japan
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24
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Saini C, Petrenko V, Pulimeno P, Giovannoni L, Berney T, Hebrok M, Howald C, Dermitzakis ET, Dibner C. A functional circadian clock is required for proper insulin secretion by human pancreatic islet cells. Diabetes Obes Metab 2016; 18:355-65. [PMID: 26662378 DOI: 10.1111/dom.12616] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 10/08/2015] [Accepted: 12/01/2015] [Indexed: 01/20/2023]
Abstract
AIM To determine the impact of a functional human islet clock on insulin secretion and gene transcription. METHODS Efficient circadian clock disruption was achieved in human pancreatic islet cells by small interfering RNA-mediated knockdown of CLOCK. Human islet secretory function was assessed in the presence or absence of a functional circadian clock by stimulated insulin secretion assays, and by continuous around-the-clock monitoring of basal insulin secretion. Large-scale transcription analysis was accomplished by RNA sequencing, followed by quantitative RT-PCR analysis of selected targets. RESULTS Circadian clock disruption resulted in a significant decrease in both acute and chronic glucose-stimulated insulin secretion. Moreover, basal insulin secretion by human islet cells synchronized in vitro exhibited a circadian pattern, which was perturbed upon clock disruption. RNA sequencing analysis suggested alterations in 352 transcript levels upon circadian clock disruption. Among them, key regulators of the insulin secretion pathway (GNAQ, ATP1A1, ATP5G2, KCNJ11) and transcripts required for granule maturation and release (VAMP3, STX6, SLC30A8) were affected. CONCLUSIONS Using our newly developed experimental approach for efficient clock disruption in human pancreatic islet cells, we show for the first time that a functional β-cell clock is required for proper basal and stimulated insulin secretion. Moreover, clock disruption has a profound impact on the human islet transcriptome, in particular, on the genes involved in insulin secretion.
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MESH Headings
- CLOCK Proteins/antagonists & inhibitors
- CLOCK Proteins/genetics
- CLOCK Proteins/metabolism
- Cation Transport Proteins/antagonists & inhibitors
- Cation Transport Proteins/chemistry
- Cation Transport Proteins/genetics
- Cation Transport Proteins/metabolism
- Cells, Cultured
- Circadian Clocks/drug effects
- Colforsin/pharmacology
- GTP-Binding Protein alpha Subunits, Gq-G11/antagonists & inhibitors
- GTP-Binding Protein alpha Subunits, Gq-G11/chemistry
- GTP-Binding Protein alpha Subunits, Gq-G11/genetics
- GTP-Binding Protein alpha Subunits, Gq-G11/metabolism
- Gene Expression Profiling
- Gene Expression Regulation/drug effects
- Genes, Reporter/drug effects
- Humans
- Hyperglycemia/metabolism
- Insulin/metabolism
- Insulin Secretion
- Insulin-Secreting Cells/cytology
- Insulin-Secreting Cells/drug effects
- Insulin-Secreting Cells/metabolism
- Islets of Langerhans/cytology
- Islets of Langerhans/drug effects
- Islets of Langerhans/metabolism
- Potassium Channels, Inwardly Rectifying/antagonists & inhibitors
- Potassium Channels, Inwardly Rectifying/chemistry
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Qa-SNARE Proteins/antagonists & inhibitors
- Qa-SNARE Proteins/chemistry
- Qa-SNARE Proteins/genetics
- Qa-SNARE Proteins/metabolism
- RNA Interference
- RNA, Small Interfering
- Sodium-Potassium-Exchanging ATPase/antagonists & inhibitors
- Sodium-Potassium-Exchanging ATPase/chemistry
- Sodium-Potassium-Exchanging ATPase/genetics
- Sodium-Potassium-Exchanging ATPase/metabolism
- Vesicle-Associated Membrane Protein 3/antagonists & inhibitors
- Vesicle-Associated Membrane Protein 3/chemistry
- Vesicle-Associated Membrane Protein 3/genetics
- Vesicle-Associated Membrane Protein 3/metabolism
- Zinc Transporter 8
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Affiliation(s)
- C Saini
- Endocrinology, Diabetes, Hypertension and Nutrition, Diabetes Centre, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Institute of Genetics and Genomics in Geneva (iGE3), Geneva, Switzerland
| | - V Petrenko
- Endocrinology, Diabetes, Hypertension and Nutrition, Diabetes Centre, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Institute of Genetics and Genomics in Geneva (iGE3), Geneva, Switzerland
| | - P Pulimeno
- Endocrinology, Diabetes, Hypertension and Nutrition, Diabetes Centre, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Diabetes Center, UCSF, San Francisco, CA, USA
| | - L Giovannoni
- Endocrinology, Diabetes, Hypertension and Nutrition, Diabetes Centre, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - T Berney
- Department of Surgery, Cell Isolation and Transplantation Centre, University Hospital of Geneva, Geneva, Switzerland
| | - M Hebrok
- Diabetes Center, UCSF, San Francisco, CA, USA
| | - C Howald
- Institute of Genetics and Genomics in Geneva (iGE3), Geneva, Switzerland
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
- Swiss Institute of Bioinformatics, Geneva, Switzerland
| | - E T Dermitzakis
- Institute of Genetics and Genomics in Geneva (iGE3), Geneva, Switzerland
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
- Swiss Institute of Bioinformatics, Geneva, Switzerland
| | - C Dibner
- Endocrinology, Diabetes, Hypertension and Nutrition, Diabetes Centre, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Institute of Genetics and Genomics in Geneva (iGE3), Geneva, Switzerland
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25
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Röder PV, Wu B, Liu Y, Han W. Pancreatic regulation of glucose homeostasis. Exp Mol Med 2016; 48:e219. [PMID: 26964835 PMCID: PMC4892884 DOI: 10.1038/emm.2016.6] [Citation(s) in RCA: 423] [Impact Index Per Article: 52.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 12/03/2015] [Accepted: 12/06/2015] [Indexed: 12/11/2022] Open
Abstract
In order to ensure normal body function, the human body is dependent on a tight control of its blood glucose levels. This is accomplished by a highly sophisticated network of various hormones and neuropeptides released mainly from the brain, pancreas, liver, intestine as well as adipose and muscle tissue. Within this network, the pancreas represents a key player by secreting the blood sugar-lowering hormone insulin and its opponent glucagon. However, disturbances in the interplay of the hormones and peptides involved may lead to metabolic disorders such as type 2 diabetes mellitus (T2DM) whose prevalence, comorbidities and medical costs take on a dramatic scale. Therefore, it is of utmost importance to uncover and understand the mechanisms underlying the various interactions to improve existing anti-diabetic therapies and drugs on the one hand and to develop new therapeutic approaches on the other. This review summarizes the interplay of the pancreas with various other organs and tissues that maintain glucose homeostasis. Furthermore, anti-diabetic drugs and their impact on signaling pathways underlying the network will be discussed.
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Affiliation(s)
- Pia V Röder
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore. E-mail: or
| | - Bingbing Wu
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
| | - Yixian Liu
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
| | - Weiping Han
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
- Metabolism in Human Diseases Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore. E-mail: or
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26
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Strodthoff D, Ma Z, Wirström T, Strawbridge RJ, Ketelhuth DFJ, Engel D, Clarke R, Falkmer S, Hamsten A, Hansson GK, Björklund A, Lundberg AM. Toll-Like Receptor 3 Influences Glucose Homeostasis and β-Cell Insulin Secretion. Diabetes 2015; 64:3425-38. [PMID: 25918231 DOI: 10.2337/db14-0838] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 04/17/2015] [Indexed: 11/13/2022]
Abstract
Toll-like receptors (TLRs) have been implicated in the pathogenesis of type 2 diabetes. We examined the function of TLR3 in glucose metabolism and type 2 diabetes-related phenotypes in animals and humans. TLR3 is highly expressed in the pancreas, suggesting that it can influence metabolism. Using a diet-induced obesity model, we show that TLR3-deficient mice had enhanced glycemic control, facilitated by elevated insulin secretion. Despite having high insulin levels, Tlr3(-/-) mice did not experience disturbances in whole-body insulin sensitivity, suggesting that they have a robust metabolic system that manages increased insulin secretion. Increase in insulin secretion was associated with upregulation of islet glucose phosphorylation as well as exocytotic protein VAMP-2 in Tlr3(-/-) islets. TLR3 deficiency also modified the plasma lipid profile, decreasing VLDL levels due to decreased triglyceride biosynthesis. Moreover, a meta-analysis of two healthy human populations showed that a missense single nucleotide polymorphism in TLR3 (encoding L412F) was linked to elevated insulin levels, consistent with our experimental findings. In conclusion, our results increase the understanding of the function of innate receptors in metabolic disorders and implicate TLR3 as a key control system in metabolic regulation.
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Affiliation(s)
- Daniela Strodthoff
- Cardiovascular Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden Metabolism Unit, Department of Medicine, and Department of Endocrinology, Metabolism and Diabetes, Karolinska Institutet at Karolinska University Hospital Huddinge, Karolinska Institutet/AstraZeneca Integrated Cardio Metabolic Center and Center for Innovative Medicine, NOVUM, Stockholm, Sweden
| | - Zuheng Ma
- Endocrinology and Diabetes Unit, Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Tina Wirström
- Endocrinology and Diabetes Unit, Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Rona J Strawbridge
- Atherosclerosis Research Unit, Center for Molecular Medicine, Department of Medicine Solna, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Daniel F J Ketelhuth
- Cardiovascular Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - David Engel
- Cardiovascular Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Robert Clarke
- Clinical Trial Service Unit and Epidemiological Studies Unit, University of Oxford, Oxford, U.K
| | - Sture Falkmer
- Laboratory of Pathology and Clinical Cytology, Ryhov Hospital, Jönköping, Sweden
| | - Anders Hamsten
- Atherosclerosis Research Unit, Center for Molecular Medicine, Department of Medicine Solna, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Göran K Hansson
- Cardiovascular Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Anneli Björklund
- Endocrinology and Diabetes Unit, Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Anna M Lundberg
- Cardiovascular Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
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27
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The specific and rapid labeling of cell surface proteins with recombinant FKBP-fused fluorescent proteins. Protein Cell 2015; 5:800-3. [PMID: 25109944 PMCID: PMC4180455 DOI: 10.1007/s13238-014-0090-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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28
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Doc2b serves as a scaffolding platform for concurrent binding of multiple Munc18 isoforms in pancreatic islet β-cells. Biochem J 2015; 464:251-8. [PMID: 25190515 DOI: 10.1042/bj20140845] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Biphasic glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells involves soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor (SNARE) protein-regulated exocytosis. SNARE complex assembly further requires the regulatory proteins Munc18c, Munc18-1 and Doc2b. Munc18-1 and Munc18c are required for first- and second-phase GSIS respectively. These distinct Munc18-1 and Munc18c roles are related to their transient high-affinity binding with their cognate target (t-)SNAREs, Syntaxin 1A and Syntaxin 4 respectively. Doc2b is essential for both phases of GSIS, yet the molecular basis for this remains unresolved. Because Doc2b binds to Munc18-1 and Munc18c via its distinct C2A and C2B domains respectively, we hypothesized that Doc2b may provide a plasma membrane-localized scaffold/platform for transient docking of these Munc18 isoforms during GSIS. Towards this, macromolecular complexes composed of Munc18c, Doc2b and Munc18-1 were detected in β-cells. In vitro interaction assays indicated that Doc2b is required to bridge the interaction between Munc18c and Munc18-1 in the macromolecular complex; Munc18c and Munc18-1 failed to associate in the absence of Doc2b. Competition-based GST-Doc2b interaction assays revealed that Doc2b could simultaneously bind both Munc18-1 and Munc18c. Hence these data support a working model wherein Doc2b functions as a docking platform/scaffold for transient interactions with the multiple Munc18 isoforms operative in insulin release, promoting SNARE assembly.
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29
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Iorio V, Festa M, Rosati A, Hahne M, Tiberti C, Capunzo M, De Laurenzi V, Turco MC. BAG3 regulates formation of the SNARE complex and insulin secretion. Cell Death Dis 2015; 6:e1684. [PMID: 25766323 PMCID: PMC4385931 DOI: 10.1038/cddis.2015.53] [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: 09/23/2014] [Revised: 01/24/2015] [Accepted: 01/27/2015] [Indexed: 01/07/2023]
Abstract
Insulin release in response to glucose stimulation requires exocytosis of insulin-containing granules. Glucose stimulation of beta cells leads to focal adhesion kinase (FAK) phosphorylation, which acts on the Rho family proteins (Rho, Rac and Cdc42) that direct F-actin remodeling. This process requires docking and fusion of secretory vesicles to the release sites at the plasma membrane and is a complex mechanism that is mediated by SNAREs. This transiently disrupts the F-actin barrier and allows the redistribution of the insulin-containing granules to more peripheral regions of the β cell, hence facilitating insulin secretion. In this manuscript, we show for the first time that BAG3 plays an important role in this process. We show that BAG3 downregulation results in increased insulin secretion in response to glucose stimulation and in disruption of the F-actin network. Moreover, we show that BAG3 binds to SNAP-25 and syntaxin-1, two components of the t-SNARE complex preventing the interaction between SNAP-25 and syntaxin-1. Upon glucose stimulation BAG3 is phosphorylated by FAK and dissociates from SNAP-25 allowing the formation of the SNARE complex, destabilization of the F-actin network and insulin release.
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Affiliation(s)
- V Iorio
- Department of Pharmacy, University of Salerno, via Giovanni Paolo II, 132, Fisciano, SA, Italy
| | - M Festa
- 1] Department of Pharmacy, University of Salerno, via Giovanni Paolo II, 132, Fisciano, SA, Italy [2] BIOUNIVERSA S.r.l., University of Salerno, via Giovanni Paolo II, 132, Fisciano, SA, Italy
| | - A Rosati
- 1] Department of Pharmacy, University of Salerno, via Giovanni Paolo II, 132, Fisciano, SA, Italy [2] BIOUNIVERSA S.r.l., University of Salerno, via Giovanni Paolo II, 132, Fisciano, SA, Italy
| | - M Hahne
- Institut de Génétique Moléculaire de Montpellier, CNRS UMR5535, Montpellier, France
| | - C Tiberti
- Department of Clinical Sciences, University of Rome Sapienza, Rome, Italy
| | - M Capunzo
- Department of Medicine and Surgery, University of Salerno, Via S. Allende, Baronissi, SA, Italy
| | - V De Laurenzi
- 1] BIOUNIVERSA S.r.l., University of Salerno, via Giovanni Paolo II, 132, Fisciano, SA, Italy [2] Department of Experimental and Clinical Sciences, University G. D'Annunzio and Fondazione G. D'Annunzio, Ce.S.I., Chieti, Italy
| | - M C Turco
- 1] BIOUNIVERSA S.r.l., University of Salerno, via Giovanni Paolo II, 132, Fisciano, SA, Italy [2] Department of Medicine and Surgery, University of Salerno, Via S. Allende, Baronissi, SA, Italy
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30
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Parimi V, Goyal R, Poropatich K, Yang XJ. Neuroendocrine differentiation of prostate cancer: a review. AMERICAN JOURNAL OF CLINICAL AND EXPERIMENTAL UROLOGY 2014; 2:273-285. [PMID: 25606573 PMCID: PMC4297323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 12/09/2014] [Indexed: 06/04/2023]
Abstract
Neuroendocrine cells are one of the epithelial populations in the prostate. Neuroendocrine differentiation (NED) has been observed in prostate cancer. In addition to small cell neuroendocrine carcinomas and carcinoid tumors of the prostate, prostatic adenocarcinomas may have NED. The incidence and clinical relevance of NED in prostatic adenocarcinoma is not clearly understood because of conflicting results in the reported studies, and evaluation of NED is not routinely performed in clinical practice. This review is an overall synthesis with an aim to develop a more comprehensive understanding and practical approach towards the current knowledge of neuroendocrine differentiation. In this review we are stratifying these lesions into separate subtypes based on histologic parameters such as tumor morphology, neuroendocrine cell density and distribution and clinical parameters. We also want to identify current controversies and confusing issues not totally resolved in this topic for further investigations. Eventually a clearer understanding of this phenomenon and appropriate handling NED in prostate cancer will benefit clinical practice.
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Affiliation(s)
- Vamsi Parimi
- Robert H Lurie Comprehensive Cancer CenterChicago, IL
| | - Rajen Goyal
- Department of Pathology, Northwestern UniversityChicago, IL
| | | | - Ximing J Yang
- Robert H Lurie Comprehensive Cancer CenterChicago, IL
- Department of Pathology, Northwestern UniversityChicago, IL
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31
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Organization of organelles and VAMP-associated vesicular transport systems in differentiating skeletal muscle cells. Anat Sci Int 2014; 90:33-9. [DOI: 10.1007/s12565-014-0266-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Accepted: 11/19/2014] [Indexed: 10/24/2022]
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32
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Ramalingam L, Oh E, Thurmond DC. Doc2b enrichment enhances glucose homeostasis in mice via potentiation of insulin secretion and peripheral insulin sensitivity. Diabetologia 2014; 57:1476-84. [PMID: 24705606 PMCID: PMC4055500 DOI: 10.1007/s00125-014-3227-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 03/11/2014] [Indexed: 01/08/2023]
Abstract
AIMS/HYPOTHESIS Insulin secretion from pancreatic beta cells and insulin-stimulated glucose uptake into skeletal muscle are processes regulated by similar isoforms of the soluble N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE) and mammalian homologue of unc-18 (Munc18) protein families. Double C2 domain β (Doc2b), a SNARE- and Munc18-interacting protein, is implicated as a crucial effector of glycaemic control. However, whether Doc2b is naturally limiting for these processes, and whether Doc2b enrichment might exert a beneficial effect upon glycaemia in vivo, remains undetermined. METHODS Tetracycline-repressible transgenic (Tg) mice engineered to overexpress Doc2b simultaneously in the pancreas, skeletal muscle and adipose tissues were compared with wild-type (Wt) littermate mice regarding glucose and insulin tolerance, islet function in vivo and ex vivo, and skeletal muscle GLUT4 accumulation in transverse tubule/sarcolemmal surface membranes. SNARE complex formation was further assessed using Doc2b overexpressing L6-GLUT4-myc myoblasts to derive mechanisms relatable to physiological in vivo analyses. RESULTS Doc2b Tg mice cleared glucose substantially faster than Wt mice, correlated with enhancements in both phases of insulin secretion and peripheral insulin sensitivity. Heightened peripheral insulin sensitivity correlated with elevated insulin-stimulated GLUT4 vesicle accumulation in cell surface membranes of Doc2b Tg mouse skeletal muscle. Mechanistic studies demonstrated Doc2b enrichment to enhance syntaxin-4-SNARE complex formation in skeletal muscle cells. CONCLUSIONS/INTERPRETATION Doc2b is a limiting factor in SNARE exocytosis events pertinent to glycaemic regulation in vivo. Doc2b enrichment may provide a novel means to simultaneously boost islet and skeletal muscle function in vivo in the treatment and/or prevention of diabetes.
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Affiliation(s)
- Latha Ramalingam
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
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Li SK, Zhu D, Gaisano HY, Brubaker PL. Role of vesicle-associated membrane protein 2 in exocytosis of glucagon-like peptide-1 from the murine intestinal L cell. Diabetologia 2014; 57:809-18. [PMID: 24356748 DOI: 10.1007/s00125-013-3143-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 11/22/2013] [Indexed: 12/27/2022]
Abstract
AIMS/HYPOTHESIS Glucagon-like peptide-1 (GLP-1), secreted by the enteroendocrine L cell, is an incretin hormone that potently stimulates insulin secretion. Although signalling pathways promoting GLP-1 release are well characterised, the mechanisms by which GLP-1-containing granules fuse to the L cell membrane are unknown. As soluble NSF attachment proteins (SNAREs) are known to mediate granule-membrane fusion, the role of vesicle-associated membrane proteins (VAMPs) in GLP-1 exocytosis was examined. METHODS SNARE expression was determined in murine GLUTag L cells by RT-PCR and immunoblot and in primary murine L cells by immunofluorescence. Co-immunoprecipitation was used to examine SNARE interactions, while tetanus toxin (TetX)-mediated cleavage of VAMP was used with a GLP-1 secretion assay and total internal reflection fluorescence microscopy to determine the role of VAMP2 in exocytosis. RESULTS VAMP2 was expressed in murine L cells and localised to secretory granules in GLUTag cells. VAMP1/3 and the core membrane proteins syntaxin1a and synaptosomal-associated protein 25 kDa (SNAP25) were also detected. TetX cleaved VAMPs in GLUTag cells. However, only VAMP2 interacted with syntaxin1a, as did SNAP25 and Munc18-1. TetX treatment of GLUTag cells prevented glucose-dependent insulinotrophic peptide- and oleic-acid-stimulated GLP-1 secretion (p < 0.05-0.01), as well as K(+)-stimulated single-cell exocytosis (p < 0.05-0.001), while TetX-resistant VAMP2 expression rescued GLP-1 secretion (p < 0.01-0.001). CONCLUSIONS/INTERPRETATION Together, these findings indicate an essential role for VAMP2 in GLP-1 exocytosis from the GLUTag L cell in response to a variety of established secretagogues. An improved understanding of the mechanisms governing the release of GLP-1 may lead to new therapeutic approaches to enhance the levels of this incretin hormone in patients with type 2 diabetes.
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Affiliation(s)
- Samantha K Li
- Department of Physiology, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, ON, M5S 1A8, Canada
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Analysis of synaptic-like microvesicle exocytosis of B-cells using a live imaging technique. PLoS One 2014; 9:e87758. [PMID: 24503905 PMCID: PMC3913683 DOI: 10.1371/journal.pone.0087758] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 01/02/2014] [Indexed: 11/19/2022] Open
Abstract
Pancreatic β-cells play central roles in blood glucose homeostasis. Beside insulin, these cells release neurotransmitters and other signaling molecules stored in synaptic-like microvesicles (SLMVs). We monitored SLMV exocytosis by transfecting a synaptophysin-pHluorin construct and by visualizing the cells by Total Internal Reflection Fluorescence (TIRF) microscopy. SLMV fusion was elicited by 20 mM glucose and by depolarizing K+ concentrations with kinetics comparable to insulin secretion. SLMV exocytosis was prevented by Tetanus and Botulinum-C neurotoxins indicating that the fusion machinery of these organelles includes VAMP-2/-3 and Syntaxin-1, respectively. Sequential visualization of SLMVs by TIRF and epifluorescence microscopy showed that after fusion the vesicle components are rapidly internalized and the organelles re-acidified. Analysis of single fusion episodes revealed the existence of two categories of events. While under basal conditions transient fusion events prevailed, long-lasting episodes were more frequent upon secretagogue exposure. Our observations unveiled similarities between the mechanism of exocytosis of insulin granules and SLMVs. Thus, diabetic conditions characterized by defective insulin secretion are most probably associated also with inappropriate release of molecules stored in SLMVs. The assessment of the contribution of SLMV exocytosis to the manifestation of the disease will be facilitated by the use of the imaging approach described in this study.
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Zhu ZQ, Wang D, Xiang D, Yuan YX, Wang Y. Calcium/calmodulin-dependent serine protein kinase is involved in exendin-4-induced insulin secretion in INS-1 cells. Metabolism 2014; 63:120-6. [PMID: 24140090 DOI: 10.1016/j.metabol.2013.09.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 08/23/2013] [Accepted: 09/15/2013] [Indexed: 12/25/2022]
Abstract
OBJECTIVE Exendin-4 (Ex-4) is an anti-diabetic drug that is a potent agonist of the glucagon-like peptide-1 (GLP-1) receptor. It has already been approved for the treatment of type 2 diabetes mellitus, but its underlying mechanisms of action are not fully understood. Calcium/calmodulin-dependent serine protein kinase (CASK), which plays a vital role in the transport and release of neurotransmitters in neurons, is expressed in pancreatic islet cells and β-cells. This study aimed to investigate whether CASK is involved in the insulin secretagogue action induced by Ex-4 in INS-1 cells. MATERIAL/METHODS A glucose-stimulated insulin secretion (GSIS) assay was performed with or without siRNA treatment against CASK. The expression level and location of CASK were evaluated by real-time PCR, western blotting and immunofluorescence. With the use of a protein kinase A (PKA) inhibitor or an exchange protein directly activated by cAMP-2 (Epac2) agonist, immunoblotting was performed to establish the signaling pathway through which Ex-4 alters CASK expression. RESULTS Knock-down of CASK significantly attenuated the Ex-4-enhanced insulin release, and we showed that Ex-4 could increase transcription of CASK mRNA and expression of CASK protein but did not change the cellular location of CASK. A PKA inhibitor reduced the ability of Ex-4 to stimulate CASK expression, but an Epac2 agonist had no effect suggesting that regulation was mediated by the cAMP/PKA pathway. CONCLUSION Our study suggests that the stimulation of β-cell insulin secretion by Ex-4 is mediated, at least in part, by CASK via a novel signaling mechanism.
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Affiliation(s)
- Zheng-Qiu Zhu
- Department of Endocrinology, Zhongda Hospital, Institute of Diabetes, Southeast University, Nanjing 210009, PR China
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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: 97] [Impact Index Per Article: 8.8] [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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Ordelheide AM, Gerst F, Rothfuss O, Heni M, Haas C, Thielker I, Herzberg-Schäfer S, Böhm A, Machicao F, Ullrich S, Stefan N, Fritsche A, Häring HU, Staiger H. Nor-1, a novel incretin-responsive regulator of insulin genes and insulin secretion. Mol Metab 2013; 2:243-55. [PMID: 24044104 DOI: 10.1016/j.molmet.2013.06.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 06/07/2013] [Accepted: 06/10/2013] [Indexed: 01/09/2023] Open
Abstract
B-cell failure at the onset of type 2 diabetes is caused by a decline in β-cell function in the postprandial state and loss of pancreatic β-cell mass. Recently, we showed an association between increased insulin secretion and a single nucleotide polymorphism (SNP), SNP rs12686676, in the NR4A3 gene locus encoding the nuclear receptor Nor-1. Nor-1 is expressed in β-cells, however, not much is known about its function with regard to insulin gene expression and insulin secretion. Nor-1 is induced in a glucose-/incretin-dependent manner via the PKA pathway and directly induces insulin gene expression. Additionally, it stimulates insulin secretion possibly via regulation of potentially important genes in insulin exocytosis. Moreover, we show that the minor allele of NR4A3 SNP rs12686676 fully rescues incretin resistance provoked by a well-described polymorphism in TCF7L2. Thus, Nor-1 represents a promising new target for pharmacological intervention to fight diabetes.
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Affiliation(s)
- Anna-Maria Ordelheide
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, University Hospital Tübingen, Germany ; Institute for Diabetes Research and Metabolic Diseases of the Helmholz Centre Munich at the University of Tübingen, Germany ; German Center for Diabetes Research (DZD), Neuherberg, Germany
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A p21-activated kinase (PAK1) signaling cascade coordinately regulates F-actin remodeling and insulin granule exocytosis in pancreatic β cells. Biochem Pharmacol 2012; 85:808-16. [PMID: 23246867 DOI: 10.1016/j.bcp.2012.12.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 12/04/2012] [Accepted: 12/06/2012] [Indexed: 12/21/2022]
Abstract
Human islet studies implicate an important signaling role for the Cdc42 effector protein p21-activated kinase (PAK1) in the sustained/second-phase of insulin secretion. Because human islets from type 2 diabetic donors lack ∼80% of normal PAK1 protein levels, the mechanistic requirement for PAK1 signaling in islet function was interrogated. Similar to MIN6 β cells, human islets elicited glucose-stimulated PAK1 activation that was sensitive to the PAK1 inhibitor, IPA3. Given that sustained insulin secretion has been correlated with glucose-induced filamentous actin (F-actin) remodeling, we tested the hypothesis that a Cdc42-activated PAK1 signaling cascade is required to elicit F-actin remodeling to mobilize granules to the cell surface. Live-cell imaging captured the glucose-induced cortical F-actin remodeling in MIN6 β cells; IPA3-mediated inhibition of PAK1 abolished this remodeling. IPA3 also ablated glucose-stimulated insulin granule accumulation at the plasma membrane, consistent with its role in sustained/second-phase insulin release. Both IPA3 and a selective inhibitor of the Cdc42 GTPase, ML-141, blunted the glucose-stimulated activation of Raf-1, suggesting Raf-1 to be downstream of Cdc42→PAK1. IPA3 also inhibited MEK1/2 activation, implicating the MEK1/2→ERK1/2 cascade to occur downstream of PAK1. Importantly, PD0325901, a new selective inhibitor of MEK1/2→ERK1/2 activation, impaired F-actin remodeling and the sustained/amplification pathway of insulin release. Taken together, these data suggest that glucose-mediated activation of Cdc42 leads to activation of PAK1 and prompts activation of its downstream targets Raf-1, MEK1/2 and ERK1/2 to elicit F-actin remodeling and recruitment of insulin granules to the plasma membrane to support the sustained phase of insulin release.
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Markwardt ML, Nkobena A, Ding SY, Rizzo MA. Association with nitric oxide synthase on insulin secretory granules regulates glucokinase protein levels. Mol Endocrinol 2012; 26:1617-29. [PMID: 22771492 PMCID: PMC3434526 DOI: 10.1210/me.2012-1183] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Accepted: 06/19/2012] [Indexed: 11/19/2022] Open
Abstract
Glucokinase (GCK) association with insulin-secretory granules is controlled by interaction with nitric oxide synthase (NOS) and is reversed by GCK S-nitrosylation. Nonetheless, the function of GCK sequestration on secretory granules is unknown. Here we report that the S-nitrosylation blocking V367M mutation prevents GCK accumulation on secretory granules by inhibiting association with NOS. Expression of this mutant is reduced compared with a second S-nitrosylation blocking GCK mutant (C371S) that accumulates to secretory granules and is expressed at levels greater than wild type. Even so, the rate of degradation for wild type and mutant GCK proteins were not significantly different from one another, and neither mutation disrupted the ability of GCK to be ubiquitinated. Furthermore, gene silencing of NOS reduced endogenous GCK content but did not affect β-actin content. Treatment of GCK(C371S) expressing cells with short interfering RNA specific for NOS also blocked accumulation of this protein to secretory granules and reduced expression levels to that of GCK(V367M). Conversely, cotransfection of catalytically inactive NOS increased GCK-mCherry levels. Expression of GCK(C371S) in βTC3 cells enhanced glucose metabolism compared with untransfected cells and cells expressing wild type GCK, even though this mutant has slightly reduced enzymatic activity in vitro. Finally, molecular dynamics simulations revealed that V367M induces conformational changes in GCK that are similar to S-nitrosylated GCK, thereby suggesting a mechanism for V367M-inhibition of NOS association. Our findings suggest that sequestration of GCK on secretory granules regulates cellular GCK protein content, and thus cellular GCK activity, by acting as a storage pool for GCK proteins.
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Affiliation(s)
- Michele L Markwardt
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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Schvartz D, Brunner Y, Couté Y, Foti M, Wollheim CB, Sanchez JC. Improved characterization of the insulin secretory granule proteomes. J Proteomics 2012; 75:4620-31. [PMID: 22569486 DOI: 10.1016/j.jprot.2012.04.023] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Revised: 02/22/2012] [Accepted: 04/20/2012] [Indexed: 11/15/2022]
Abstract
Insulin secretory granules (ISGs) are pivotal organelles of pancreatic ß-cells and represent a key participant to glucose homeostasis. Indeed, insulin is packed and processed within these vesicles before its release by exocytosis. It is therefore crucial to acquire qualitative and quantitative data on the ISG proteome, in order to increase our knowledge on ISG biogenesis, maturation and exocytosis. Despites efforts made in the past years, the coverage of the ISG proteome is still incomplete and comprises many potential protein contaminants most likely coming from suboptimal sample preparations. We developed here a 3-step gradient purification procedure combined to Stable Isotope Labeling with Amino acids in Cell culture (SILAC) to further characterize the ISG protein content. Our results allowed to build three complementary proteomes containing 1/ proteins which are enriched in mature ISGs, 2/ proteins sharing multiple localizations including ISGs, and finally 3/ proteins sorted out from immature ISGs and/or co-purifying contaminants. As a proof of concept, the ProSAAS, a neuronal protein found in ISGs was further characterized and its granular localization proved. ProSAAS might represent a novel potential target allowing to better understand the defaults in insulin processing and secretion observed during type 2 diabetes progression. This article is part of a special issue entitled: Translational Proteomics.
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Affiliation(s)
- Domitille Schvartz
- Biomedical Proteomics Research Group, Department of Human Protein Sciences, University Medical Center, Geneva, Switzerland
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Gong Z, Muzumdar RH. Pancreatic function, type 2 diabetes, and metabolism in aging. Int J Endocrinol 2012; 2012:320482. [PMID: 22675349 PMCID: PMC3362843 DOI: 10.1155/2012/320482] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 02/15/2012] [Accepted: 03/02/2012] [Indexed: 12/21/2022] Open
Abstract
Aging is a risk factor for impaired glucose tolerance and diabetes. Of the reported 25.8 million Americans estimated to have diabetes, 26.9% are over the age of 65. In certain ethnic groups, the proportion is even higher; almost 1 in 3 older Hispanics and African Americans and 3 out of 4 Pima Indian elders have diabetes. As per the NHANES III (Third National Health and Nutrition Examination) survey, the percentage of physician-diagnosed diabetes increased from 3.9% in middle-aged adults (40-49 years) to 13.2% in elderly adults (≥75 years). The higher incidence of diabetes is especially alarming considering that diabetes in itself increases the risk for multiple other age-related diseases such as cancer, stroke, cardiovascular diseases, Parkinson's disease, and Alzheimer's disease (AD). In this review, we summarize the current evidence on how aging affects pancreatic β cell function, β cell mass, insulin secretion and insulin sensitivity. We also review the effects of aging on the relationship between insulin sensitivity and insulin secretion. Understanding the mechanisms that lead to impaired glucose homeostasis and T2D in the elderly will lead to development of novel treatments that will prevent or delay diabetes, substantially improve quality of life and ultimately increase overall life span.
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Affiliation(s)
- Zhenwei Gong
- Department of Pediatrics, Divisions of Endocrinology and Geriatrics, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Radhika H. Muzumdar
- Department of Pediatrics, Divisions of Endocrinology and Geriatrics, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Department of Medicine, Divisions of Endocrinology and Geriatrics, Children's Hospital at Montefiore, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
- *Radhika H. Muzumdar:
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Rondas D, Tomas A, Soto-Ribeiro M, Wehrle-Haller B, Halban PA. Novel mechanistic link between focal adhesion remodeling and glucose-stimulated insulin secretion. J Biol Chem 2011; 287:2423-36. [PMID: 22139838 DOI: 10.1074/jbc.m111.279885] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Actin cytoskeleton remodeling is well known to be positively involved in glucose-stimulated pancreatic β cell insulin secretion. We have observed glucose-stimulated focal adhesion remodeling at the β cell surface and have shown this to be crucial for glucose-stimulated insulin secretion. However, the mechanistic link between such remodeling and the insulin secretory machinery remained unknown and was the major aim of this study. MIN6B1 cells, a previously validated model of primary β cell function, were used for all experiments. Total internal reflection fluorescence microscopy revealed the glucose-responsive co-localization of focal adhesion kinase (FAK) and paxillin with integrin β1 at the basal cell surface after short term stimulation. In addition, blockade of the interaction between β1 integrins and the extracellular matrix with an anti-β1 integrin antibody (Ha2/5) inhibited short term glucose-induced phosphorylation of FAK (Tyr-397), paxillin (Tyr-118), and ERK1/2 (Thr-202/Tyr-204). Pharmacological inhibition of FAK activity blocked glucose-induced actin cytoskeleton remodeling and glucose-induced disruption of the F-actin/SNAP-25 association at the plasma membrane as well as the distribution of insulin granules to regions in close proximity to the plasma membrane. Furthermore, FAK inhibition also completely blocked short term glucose-induced activation of the Akt/AS160 signaling pathway. In conclusion, these results indicate 1) that glucose-induced activation of FAK, paxillin, and ERK1/2 is mediated by β1 integrin intracellular signaling, 2) a mechanism whereby FAK mediates glucose-induced actin cytoskeleton remodeling, hence allowing docking and fusion of insulin granules to the plasma membrane, and 3) a possible functional role for the Akt/AS160 signaling pathway in the FAK-mediated regulation of glucose-stimulated insulin secretion.
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Affiliation(s)
- Dieter Rondas
- Department of Genetic Medicine and Development, University of Geneva, CH-1211 Geneva 4, Switzerland.
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Kalwat MA, Wiseman DA, Luo W, Wang Z, Thurmond DC. Gelsolin associates with the N terminus of syntaxin 4 to regulate insulin granule exocytosis. Mol Endocrinol 2011; 26:128-41. [PMID: 22108804 DOI: 10.1210/me.2011-1112] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The plasma membrane soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) protein syntaxin (Syn)4 is required for biphasic insulin secretion, although how it regulates each phase remains unclear. In a screen to identify new Syn4-interacting factors, the calcium-activated F-actin-severing protein gelsolin was revealed. Gelsolin has been previously implicated as a positive effector of insulin secretion, although a molecular mechanism to underlie this function is lacking. Toward this, our in vitro binding studies showed the Syn4-gelsolin interaction to be direct and mediated by the N-terminal Ha domain (amino acid residues 39-70) of Syn4. Syn4-gelsolin complexes formed under basal conditions and dissociated upon acute glucose or KCl stimulation; nifedipine blocked dissociation. The dissociating action of secretagogues could be mimicked by expression of the N-terminal Ha domain of Syn4 fused to green fluorescent protein (GFP) (GFP-39-70). Furthermore, GFP-39-70 expression in isolated mouse islet and clonal MIN6 β-cells initiated insulin release in the absence of appropriate stimuli. Consistent with this, the inhibitory GFP-39-70 peptide also initiated Syn4 activation in the absence of stimuli. Moreover, although MIN6 β-cells expressing the GFP-39-70 peptide maintained normal calcium influx in response to KCl, KCl-stimulated insulin secretion and the triggering pathway of insulin secretion were significantly impaired. Taken together, these data support a mechanistic model for gelsolin's role in insulin exocytosis: gelsolin clamps unsolicited soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE)-regulated exocytosis through direct association with Syn4 in the absence of appropriate stimuli, which is relieved upon stimulus-induced calcium influx to activate gelsolin and induce its dissociation from Syn4 to facilitate insulin exocytosis.
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Affiliation(s)
- Michael A Kalwat
- Departments of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Han WQ, Xia M, Zhang C, Zhang F, Xu M, Li NJ, Li PL. SNARE-mediated rapid lysosome fusion in membrane raft clustering and dysfunction of bovine coronary arterial endothelium. Am J Physiol Heart Circ Physiol 2011; 301:H2028-37. [PMID: 21926345 DOI: 10.1152/ajpheart.00581.2011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The present study attempted to evaluate whether soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) mediate lysosome fusion in response to death receptor activation and contribute to membrane raft (MR) clustering and consequent endothelial dysfunction in coronary arterial endothelial cells. By immunohistochemical analysis, vesicle-associated membrane proteins 2 (VAMP-2, vesicle-SNAREs) were found to be abundantly expressed in the endothelium of bovine coronary arteries. Direct lysosome fusion monitoring by N-(3-triethylammoniumpropyl)-4-[4-(dibutylamino)styryl]pyridinium dibromide (FM1-43) quenching demonstrated that the inhibition of VAMP-2 with tetanus toxin or specific small interfering ribonucleic acid (siRNA) almost completely blocked lysosome fusion to plasma membrane induced by Fas ligand (FasL), a well-known MR clustering stimulator. The involvement of SNAREs was further confirmed by an increased interaction of VAMP-2 with a target-SNARE protein syntaxin-4 after FasL stimulation in coimmunoprecipitation analysis. Also, the inhibition of VAMP-2 with tetanus toxin or VAMP-2 siRNA abolished FasL-induced MR clustering, its colocalization with a NADPH oxidase unit gp91(phox), and increased superoxide production. Finally, FasL-induced impairment of endothelium-dependent vasodilation was reversed by the treatment of bovine coronary arteries with tetanus toxin or VAMP-2 siRNA. VAMP-2 is critical to lysosome fusion in MR clustering, and this VAMP-2-mediated lysosome-MR signalosomes contribute to redox regulation of coronary endothelial function.
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Affiliation(s)
- Wei-Qing Han
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA
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Schubert V, Bouvier D, Volterra A. SNARE protein expression in synaptic terminals and astrocytes in the adult hippocampus: a comparative analysis. Glia 2011; 59:1472-88. [PMID: 21656854 DOI: 10.1002/glia.21190] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 04/27/2011] [Indexed: 01/02/2023]
Abstract
Several evidences suggest that astrocytes release small transmitter molecules, peptides, and protein factors via regulated exocytosis, implying that they function as specialized neurosecretory cells. However, very little is known about the molecular and functional properties of regulated secretion in astrocytes in the adult brain. Establishing these properties is central to the understanding of the communication mode(s) of these cells and their role(s) in the control of synaptic functions and of cerebral blood flow. In this study, we have set-up a high-resolution confocal microscopy approach to distinguish protein expression in astrocytic structures and neighboring synaptic terminals in adult brain tissue. This approach was applied to investigate the expression pattern of core SNARE proteins for vesicle fusion in the dentate gyrus and CA1 regions of the mouse hippocampus. Our comparative analysis shows that astrocytes abundantly express, in their cell body and main processes, all three protein partners necessary to form an operational SNARE complex but not in the same isoforms expressed in neighbouring synaptic terminals. Thus, SNAP25 and VAMP2 are absent from astrocytic processes and typically concentrated in terminals, while SNAP23 and VAMP3 have the opposite expression pattern. Syntaxin 1 is present in both synaptic terminals and astrocytes. These data support the view that astrocytes in the adult hippocampus can communicate via regulated exocytosis and also indicates that astrocytic exocytosis may differ in its properties from action potential-dependent exocytosis at neuronal synapses, as it relies on a distinctive set of SNARE proteins.
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Affiliation(s)
- Vanessa Schubert
- Department of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland
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Torrejón-Escribano B, Escoriza J, Montanya E, Blasi J. Glucose-dependent changes in SNARE protein levels in pancreatic β-cells. Endocrinology 2011; 152:1290-9. [PMID: 21285315 DOI: 10.1210/en.2010-0898] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Prolonged exposure to high glucose concentration alters the expression of a set of proteins in pancreatic β-cells and impairs their capacity to secrete insulin. The cellular and molecular mechanisms that lie behind this effect are poorly understood. In this study, three either in vitro or in vivo models (cultured rat pancreatic islets incubated in high glucose media, partially pancreatectomized rats, and islets transplanted to streptozotozin-induced diabetic mice) were used to evaluate the dependence of the biological model and the treatment, together with the cell location (insulin granule or plasma membrane) of the affected proteins and the possible effect of sustained insulin secretion, on the glucose-induced changes in protein expression. In all three models, islets exposed to high glucose concentrations showed a reduced expression of secretory granule-associated vesicle-soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins synaptobrevin/vesicle-associated membrane protein 2 and cellubrevin but minor or no significant changes in the expression of the membrane-associated target-SNARE proteins syntaxin1 and synaptosomal-associated protein-25 and a marked increase in the expression of synaptosomal-associated protein-23 protein. The inhibition of insulin secretion by the L-type voltage-dependent calcium channel nifedipine or the potassium channel activator diazoxide prevented the glucose-induced reduction in islet insulin content but not in vesicle-SNARE proteins, indicating that the granule depletion due to sustained exocytosis was not involved in the changes of protein expression induced by high glucose concentration. Altogether, the results suggest that high glucose has a direct toxic effect on the secretory pathway by decreasing the expression of insulin granule SNARE-associated proteins.
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Affiliation(s)
- Benjamín Torrejón-Escribano
- Departamento de Patologia i Terapèutica Experimental, Institut d'Investigació Biomèdica de Bellvitge-Universitat de Barcelona, Laboratori 4145, Campus de Bellvitge, Edifici del Pavelló de Govern, C/Feixa Llarga s/n, 08907 L'Hospitalet de Llobregat, Barcelona, Spain
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Differences in islet-enriched miRNAs in healthy and glucose intolerant human subjects. Biochem Biophys Res Commun 2011; 404:16-22. [DOI: 10.1016/j.bbrc.2010.11.024] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Accepted: 11/09/2010] [Indexed: 12/21/2022]
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Roggli E, Britan A, Gattesco S, Lin-Marq N, Abderrahmani A, Meda P, Regazzi R. Involvement of microRNAs in the cytotoxic effects exerted by proinflammatory cytokines on pancreatic beta-cells. Diabetes 2010; 59:978-86. [PMID: 20086228 PMCID: PMC2844845 DOI: 10.2337/db09-0881] [Citation(s) in RCA: 245] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Pancreatic beta-cells exposed to proinflammatory cytokines display alterations in gene expression resulting in defective insulin secretion and apoptosis. MicroRNAs are small noncoding RNAs emerging as key regulators of gene expression. Here, we evaluated the contribution of microRNAs to cytokine-mediated beta-cell cytotoxicity. RESEARCH DESIGN AND METHODS We used global microarray profiling and real-time PCR analysis to detect changes in microRNA expression in beta-cells exposed to cytokines and in islets of pre-diabetic NOD mice. We assessed the involvement of the microRNAs affected in cytokine-mediated beta-cell failure by modifying their expression in insulin-secreting MIN6 cells. RESULTS We found that IL-1beta and TNF-alpha induce the expression of miR-21, miR-34a, and miR-146a both in MIN6 cells and human pancreatic islets. We further show an increase of these microRNAs in islets of NOD mice during development of pre-diabetic insulitis. Blocking miR-21, miR-34a, or miR-146a function using antisense molecules did not restore insulin-promoter activity but prevented the reduction in glucose-induced insulin secretion observed upon IL-1beta exposure. Moreover, anti-miR-34a and anti-miR-146a treatment protected MIN6 cells from cytokine-triggered cell death. CONCLUSIONS Our data identify miR-21, miR-34a, and miR-146a as novel players in beta-cell failure elicited in vitro and in vivo by proinflammatory cytokines, notably during the development of peri-insulitis that precedes overt diabetes in NOD mice.
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Affiliation(s)
- Elodie Roggli
- Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Aurore Britan
- Department of Cell Physiology and Metabolism, School of Medicine, University of Geneva, Geneva, Switzerland
| | - Sonia Gattesco
- Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Nathalie Lin-Marq
- Department of Genetic Medicine and Development, Geneva Eurexpress, School of Medicine, University of Geneva, Geneva, Switzerland
| | - Amar Abderrahmani
- Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
- Service of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
| | - Paolo Meda
- Department of Cell Physiology and Metabolism, School of Medicine, University of Geneva, Geneva, Switzerland
| | - Romano Regazzi
- Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
- Corresponding author: Romano Regazzi,
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Jewell JL, Oh E, Thurmond DC. Exocytosis mechanisms underlying insulin release and glucose uptake: conserved roles for Munc18c and syntaxin 4. Am J Physiol Regul Integr Comp Physiol 2010; 298:R517-31. [PMID: 20053958 DOI: 10.1152/ajpregu.00597.2009] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Type 2 diabetes has been coined "a two-hit disease," as it involves specific defects of glucose-stimulated insulin secretion from the pancreatic beta cells in addition to defects in peripheral tissue insulin action required for glucose uptake. Both of these processes, insulin secretion and glucose uptake, are mediated by SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein core complexes composed of syntaxin, SNAP-23/25, and VAMP proteins. The SNARE core complex is regulated by the Sec1/Munc18 (SM) family of proteins, which selectively bind to their cognate syntaxin isoforms with high affinity. The process of insulin secretion uses multiple Munc18-syntaxin isoform pairs, whereas insulin action in the peripheral tissues appears to use only the Munc18c-syntaxin 4 pair. Importantly, recent reports have linked obesity and Type 2 diabetes in humans with changes in protein levels and single nucleotide polymorphisms (SNPs) of Munc18 and syntaxin isoforms relevant to these exocytotic processes, although the molecular mechanisms underlying the observed phenotypes remain incomplete (5, 104, 144). Given the conservation of these proteins in two seemingly disparate processes and the need to design and implement novel and more effective clinical interventions, it will be vitally important to delineate the mechanisms governing these conserved SNARE-mediated exocytosis events. Thus, we provide here an up-to-date historical review of advancements in defining the roles and molecular mechanisms of Munc18-syntaxin complexes in the pathophysiology of Type 2 diabetes.
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Affiliation(s)
- Jenna L Jewell
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
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Hosaka M, Watanabe T. Secretogranin III: a bridge between core hormone aggregates and the secretory granule membrane. Endocr J 2010; 57:275-86. [PMID: 20203425 DOI: 10.1507/endocrj.k10e-038] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Secretory granules in endocrine cells selectively store bioactive peptide hormones and amines, which are secreted in a regulated manner upon appropriate stimulation. In addition to bioactive substances, various proteins and lipids characteristic of secretory granules are likely recruited to a restricted space at the trans-Golgi Network (TGN), and the space then matures to the secretory granule. Although experimental findings so far have strongly suggested that aggregation- and receptor-mediated processes are essential for the formation of secretory granules, the putative link between these two processes remains to be clarified. Recently, secretogranin III (SgIII) has been identified as a specific binding protein for chromogranin A (CgA), a representative constituent of the core aggregate within secretory granules, and it was later revealed that SgIII can also bind to the cholesterol-rich membrane domain at the TGN. Based on its multifaceted binding properties, SgIII may act as a central player in the formation of cholesterol-rich membrane platforms. Upon these platforms, essential processes for secretory granule biogenesis coordinately occur; that is, selective recruitment of prohormones, processing and modifying of prohormones, and condensation of mature hormones as an aggregate. This review summarizes the findings and theoretical concepts on the issue to date and then focuses on the putative role of SgIII in secretory granule biogenesis in endocrine cells.
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Affiliation(s)
- Masahiro Hosaka
- Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.
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