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Hu X, Li H, Yang M, Chen Y, Zeng A, Wu J, Zhang J, Tian Y, Tang J, Qian S, Wu M. Effect of Long Non-coding RNA and DNA Methylation on Gene Expression in Dental Fluorosis. Biol Trace Elem Res 2024; 202:221-232. [PMID: 37059921 DOI: 10.1007/s12011-023-03660-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 04/04/2023] [Indexed: 04/16/2023]
Abstract
In the process of tooth development, the interaction between genetic information, epigenetic inheritance, and environment jointly affects the teeth formation. At present, the mechanism of dental fluorosis is rarely studied from transcriptomics, and there is no report on epigenetic perspective. In the study, SD rats were randomly divided into dental fluorosis group and control group fed with NaF (150 mg/L) or distilled water for 8 weeks. After 3.5 days of birth, the RNAs or DNA of rat mandibular molars were detected by RNA-seq or MethylTarget, respectively. The results demonstrated that a total of 1723 differentially expressed genes (DEGs) and 2511 differential expression lncRNAs (DE-lncRNAs) were mainly involved in the ion channels, calcium ion transport, and immunomodulatory signaling pathways. ATP2C1 and Nr1d1, which were related to Ca2+ transport, cellular calcium homeostasis, endoplasmic reticulum stress and immunity, may be the key genes in the formation of dental fluorosis. Notably, we also found that the immune response plays an important role in the formation of dental fluorosis, and a large amount of DEGs was enriched in immune regulation and NF-κB signaling pathways. Furthermore, the methylation levels of 13 sites were increased in Ago4, Atf3, Atp2c1, Dusp1, Habp4, and Mycl, while methylation levels of 5 CpG sites decreased in Ago4, Atp2c1, Habp4, and Traf6, and conformably, the expression of these genes have been significantly changed. This study comprehensively analyzed the occurrence mechanism of dental fluorosis from transcriptomics and epigenetics, so as to provide theoretical reference for further research.
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Affiliation(s)
- Xiaoyan Hu
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
| | - Huiru Li
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
| | - Minzhi Yang
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
| | - Yujiong Chen
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
| | - Ailin Zeng
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
| | - Jiayuan Wu
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
- Special Key Laboratory of Oral Disease Research, Higher Education Institution in Guizhou Province, Zunyi, 563006, China
| | - Jian Zhang
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
- Special Key Laboratory of Oral Disease Research, Higher Education Institution in Guizhou Province, Zunyi, 563006, China
| | - Yuan Tian
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
- Special Key Laboratory of Oral Disease Research, Higher Education Institution in Guizhou Province, Zunyi, 563006, China
| | - Jing Tang
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
- Special Key Laboratory of Oral Disease Research, Higher Education Institution in Guizhou Province, Zunyi, 563006, China
| | - Shengyan Qian
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China
- Special Key Laboratory of Oral Disease Research, Higher Education Institution in Guizhou Province, Zunyi, 563006, China
| | - Mingsong Wu
- Hospital of Stomatology, Zunyi Medical University, Zunyi, 563099, China.
- Special Key Laboratory of Oral Disease Research, Higher Education Institution in Guizhou Province, Zunyi, 563006, China.
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Roles of cADPR and NAADP in pancreatic beta cell signalling. Cell Calcium 2022; 103:102562. [DOI: 10.1016/j.ceca.2022.102562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 02/05/2022] [Accepted: 02/09/2022] [Indexed: 11/19/2022]
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Germanos M, Gao A, Taper M, Yau B, Kebede MA. Inside the Insulin Secretory Granule. Metabolites 2021; 11:metabo11080515. [PMID: 34436456 PMCID: PMC8401130 DOI: 10.3390/metabo11080515] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 08/03/2021] [Accepted: 08/03/2021] [Indexed: 12/19/2022] Open
Abstract
The pancreatic β-cell is purpose-built for the production and secretion of insulin, the only hormone that can remove glucose from the bloodstream. Insulin is kept inside miniature membrane-bound storage compartments known as secretory granules (SGs), and these specialized organelles can readily fuse with the plasma membrane upon cellular stimulation to release insulin. Insulin is synthesized in the endoplasmic reticulum (ER) as a biologically inactive precursor, proinsulin, along with several other proteins that will also become members of the insulin SG. Their coordinated synthesis enables synchronized transit through the ER and Golgi apparatus for congregation at the trans-Golgi network, the initiating site of SG biogenesis. Here, proinsulin and its constituents enter the SG where conditions are optimized for proinsulin processing into insulin and subsequent insulin storage. A healthy β-cell is continually generating SGs to supply insulin in vast excess to what is secreted. Conversely, in type 2 diabetes (T2D), the inability of failing β-cells to secrete may be due to the limited biosynthesis of new insulin. Factors that drive the formation and maturation of SGs and thus the production of insulin are therefore critical for systemic glucose control. Here, we detail the formative hours of the insulin SG from the luminal perspective. We do this by mapping the journey of individual members of the SG as they contribute to its genesis.
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Idevall-Hagren O, Tengholm A. Metabolic regulation of calcium signaling in beta cells. Semin Cell Dev Biol 2020; 103:20-30. [PMID: 32085965 DOI: 10.1016/j.semcdb.2020.01.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 01/10/2020] [Accepted: 01/28/2020] [Indexed: 12/22/2022]
Abstract
The cytoplasmic Ca2+ concentration ([Ca2+]cyt) regulates a vast number of cellular functions, including insulin secretion from beta cells. The major physiological insulin secretagogue, glucose, triggers [Ca2+]cyt oscillations in beta cells. Synchronization of the oscillations among the beta cells within an islet underlies the generation of pulsatile insulin secretion. This review describes the mechanisms generating [Ca2+]cyt oscillations, the interactions between [Ca2+]cyt and cell metabolism, as well as the contribution of various organelles to the shaping of [Ca2+]cyt signals and insulin secretion. It also discusses how Ca2+ signals are coordinated and spread throughout the islets and data indicating that altered Ca2+ signaling is associated with beta cell dysfunction and development of type 2 diabetes.
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Affiliation(s)
- Olof Idevall-Hagren
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, SE-751 23 Uppsala, Sweden
| | - Anders Tengholm
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, SE-751 23 Uppsala, Sweden.
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SNV discovery and functional candidate gene identification for milk composition based on whole genome resequencing of Holstein bulls with extremely high and low breeding values. PLoS One 2019; 14:e0220629. [PMID: 31369641 PMCID: PMC6675115 DOI: 10.1371/journal.pone.0220629] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 07/19/2019] [Indexed: 02/06/2023] Open
Abstract
We have sequenced the whole genomes of eight proven Holstein bulls from the four half-sib or full-sib families with extremely high and low estimated breeding values (EBV) for milk protein percentage (PP) and fat percentage (FP) using Illumina re-sequencing technology. Consequently, 2.3 billion raw reads were obtained with an average effective depth of 8.1×. After single nucleotide variant (SNV) calling, total 10,961,243 SNVs were identified, and 57,451 of them showed opposite fixed sites between the bulls with high and low EBVs within each family (called as common differential SNVs). Next, we annotated the common differential SNVs based on the bovine reference genome, and observed that 45,188 SNVs (78.70%) were located in the intergenic region of genes and merely 11,871 SNVs (20.67%) located within the protein-coding genes. Of them, 13,099 common differential SNVs that were within or close to protein-coding genes with less than 5 kb were chosen for identification of candidate genes for milk compositions in dairy cattle. By integrated analysis of the 2,657 genes with the GO terms and pathways related to protein and fat metabolism, and the known quantitative trait loci (QTLs) for milk protein and fat traits, we identified 17 promising candidate genes: ALG14, ATP2C1, PLD1, C3H1orf85, SNX7, MTHFD2L, CDKN2D, COL5A3, FDX1L, PIN1, FIG4, EXOC7, LASP1, PGS1, SAO, GPLD1 and MGEA5. Our findings provided an important foundation for further study and a prompt for molecular breeding of dairy cattle.
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The Trans Golgi Region is a Labile Intracellular Ca 2+ Store Sensitive to Emetine. Sci Rep 2018; 8:17143. [PMID: 30464185 PMCID: PMC6249204 DOI: 10.1038/s41598-018-35280-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 09/10/2018] [Indexed: 01/22/2023] Open
Abstract
The Golgi apparatus (GA) is a bona fide Ca2+ store; however, there is a lack of GA-specific Ca2+ mobilizing agents. Here, we report that emetine specifically releases Ca2+ from GA in HeLa and HL-1 atrial myocytes. Additionally, it has become evident that the trans-Golgi is a labile Ca2+ store that requires a continuous source of Ca2+ from either the external milieu or from the ER, to enable it to produce a detectable transient increase in cytosolic Ca2+. Our data indicates that the emetine-sensitive Ca2+ mobilizing mechanism is different from the two classical Ca2+ release mechanisms, i.e. IP3 and ryanodine receptors. This newly discovered ability of emetine to release Ca2+ from the GA may explain why chronic consumption of ipecac syrup has muscle side effects.
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Rodríguez MA, Martínez-Higuera A, Valle-Solis MI, Hernandes-Alejandro M, Chávez-Munguía B, Figueroa-Gutiérrez AH, Salas-Casas A. A putative calcium-ATPase of the secretory pathway family may regulate calcium/manganese levels in the Golgi apparatus of Entamoeba histolytica. Parasitol Res 2018; 117:3381-3389. [PMID: 30084034 DOI: 10.1007/s00436-018-6030-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 07/25/2018] [Indexed: 01/01/2023]
Abstract
Calcium regulates many cellular processes in protozoa, including growth, differentiation, programmed cell death, exocytosis, endocytosis, phagocytosis, fusion of the endosomes of distinct stages with phagosomes, fusion of phagosomes with lysosomes, and recycling the membrane. In Entamoeba histolytica, the protozoa responsible for human amoebiasis, calcium ions are essential for signaling pathways that lead to growth and development. In addition, calcium is crucial in the modulation of gene expression in this microorganism. However, there is scant information about the proteins responsible for regulating calcium levels in this parasite. In this work, we characterized a protein of E. histolytica that shows a close phylogenetic relationship with Ca2+ pumps that belong to the family of secretory pathway calcium ATPases (SPCA), which for several organisms are located in the Golgi apparatus. The amoeba protein analyzed herein has several amino acid residues that are characteristic of SPCA members. By an immunofluorescent technique using specific antibodies and immunoelectron microscopy, the protein was detected on the membrane of some cytoplasmic vacuoles. Moreover, this putative calcium-ATPase was located in vacuoles stained with NBD C6-ceramide, a Golgi marker. Overall, the current findings support the hypothesis that the presently analyzed protein corresponds to the SPCA of E. histolytica.
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Affiliation(s)
- Mario A Rodríguez
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, Mexico
| | | | - Martha I Valle-Solis
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, Mexico
| | - Mario Hernandes-Alejandro
- Departamento de Bioingeniería, Unidad Profesional Interdisciplinaria de Biotecnología del Instituto Politécnico Nacional (UPIBI-IPN), Mexico City, Mexico
| | - Bibiana Chávez-Munguía
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, Mexico
| | - Ana H Figueroa-Gutiérrez
- Instituto de Ciencias de la Salud, Área Académica de Gerontología, Universidad Autónoma del Estado de Hidalgo, Ex Hacienda la Concepción, s/n; Carretera Actopan-Tilcuautla, San Agustín Tlaxiaca, Hidalgo, Mexico
| | - Andrés Salas-Casas
- Instituto de Ciencias de la Salud, Área Académica de Gerontología, Universidad Autónoma del Estado de Hidalgo, Ex Hacienda la Concepción, s/n; Carretera Actopan-Tilcuautla, San Agustín Tlaxiaca, Hidalgo, Mexico.
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Ke M, Wu H, Zhu Z, Zhang C, Zhang Y, Deng Y. Differential proteomic analysis of white adipose tissues from T2D KKAy mice by LC-ESI-QTOF. Proteomics 2017; 17. [PMID: 27995753 DOI: 10.1002/pmic.201600219] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 11/28/2016] [Accepted: 12/13/2016] [Indexed: 12/14/2022]
Abstract
Type 2 diabetes (T2D) has become a worldwide increasingly social health burden for its high morbidity and heightened prevalence. As one of the main tissues involved in uptake of glucose under the stimulation of insulin, WAT plays very important role in metabolic and homeostasis regulation. We performed a differential proteomics study to investigate alterations in epididymis fat pad of high fat diet fed T2D KKAy mice compared to normal fed C57BL/6J mice, by 18 O-labeling relative quantitative technique. Among 329 confidently identified proteins, 121 proteins showed significant changes with CV ≤ 20% (fold changes of >2 or <0.5 as threshold). According to GO classification, we found that altered proteins contained members of biological processes of metabolic process, oxidative stress, ion homeostasis, apoptosis and cell division. In metabolic, proteins assigned to fatty acid biosynthesis (FAS etc.) were decreased, the key enzyme (ACOX3) in β-oxidation process was increased. Increased glycolysis enzymes (ENOB etc.) and decreased TCA cycle related enzymes (SCOT1 etc.) suggested that glucose metabolism in mitochondria of T2D mice might be impaired. Elevated oxidative stress was observed with alterations of a series of oxidordeuctase (QSOX1 etc.). Besides, alterations of ion homeostasis (AT2C1 etc.) proteins were also observed. The enhancement of cell proliferation associated proteins (ELYS etc.) and inhibition of apoptosis associated proteins (RASF6 etc.) in WAT might contributed to the fat pad and body weight gain. Overall, these changes in WAT may serve as a reference for understanding the functional mechanism of T2D.
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Affiliation(s)
- Ming Ke
- Beijing Institute of Technology, School of life science, Haidian, Beijing, P. R. China
| | - Hanyan Wu
- Beijing Institute of Technology, School of life science, Haidian, Beijing, P. R. China
| | - Zhaoyang Zhu
- Beijing Institute of Technology, School of life science, Haidian, Beijing, P. R. China
| | - Chi Zhang
- Beijing Institute of Technology, School of life science, Haidian, Beijing, P. R. China
| | - Yongqian Zhang
- Beijing Institute of Technology, School of life science, Haidian, Beijing, P. R. China
| | - Yunlin Deng
- Beijing Institute of Technology, School of life science, Haidian, Beijing, P. R. China
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Rutter GA, Hodson DJ, Chabosseau P, Haythorne E, Pullen TJ, Leclerc I. Local and regional control of calcium dynamics in the pancreatic islet. Diabetes Obes Metab 2017; 19 Suppl 1:30-41. [PMID: 28466490 DOI: 10.1111/dom.12990] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 04/19/2017] [Accepted: 04/24/2017] [Indexed: 12/31/2022]
Abstract
Ca2+ is the key intracellular regulator of insulin secretion, acting in the β-cell as the ultimate trigger for exocytosis. In response to high glucose, ATP-sensitive K+ channel closure and plasma membrane depolarization engage a sophisticated machinery to drive pulsatile cytosolic Ca2+ changes. Voltage-gated Ca2+ channels, Ca2+ -activated K+ channels and Na+ /Ca2+ exchange all play important roles. The use of targeted Ca2+ probes has revealed that during each cytosolic Ca2+ pulse, uptake of Ca2+ by mitochondria, endoplasmic reticulum (ER), secretory granules and lysosomes fine-tune cytosolic Ca2+ dynamics and control organellar function. For example, changes in the expression of the Ca2+ -binding protein Sorcin appear to provide a link between ER Ca2+ levels and ER stress, affecting β-cell function and survival. Across the islet, intercellular communication between highly interconnected "hubs," which act as pacemaker β-cells, and subservient "followers," ensures efficient insulin secretion. Loss of connectivity is seen after the deletion of genes associated with type 2 diabetes (T2D) and follows metabolic and inflammatory insults that characterize this disease. Hubs, which typically comprise ~1%-10% of total β-cells, are repurposed for their specialized role by expression of high glucokinase (Gck) but lower Pdx1 and Nkx6.1 levels. Single cell-omics are poised to provide a deeper understanding of the nature of these cells and of the networks through which they communicate. New insights into the control of both the intra- and intercellular Ca2+ dynamics may thus shed light on T2D pathology and provide novel opportunities for therapy.
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Affiliation(s)
- Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
| | - David J Hodson
- Institute of Metabolism and Systems Research (IMSR), University of Birmingham, Edgbaston, UK
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, COMPARE University of Birmingham and University of Nottingham Midlands, Birmingham, UK
| | - Pauline Chabosseau
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
| | - Elizabeth Haythorne
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
| | - Timothy J Pullen
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
| | - Isabelle Leclerc
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, and the Imperial Pancreatic Islet Biology and Diabetes Consortium, Hammersmith Hospital, Imperial College London, London, UK
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da Silva Xavier G, Mondragon A, Mourougavelou V, Cruciani-Guglielmacci C, Denom J, Herrera PL, Magnan C, Rutter GA. Pancreatic alpha cell-selective deletion of Tcf7l2 impairs glucagon secretion and counter-regulatory responses to hypoglycaemia in mice. Diabetologia 2017; 60:1043-1050. [PMID: 28343277 PMCID: PMC5423960 DOI: 10.1007/s00125-017-4242-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Accepted: 02/15/2017] [Indexed: 01/19/2023]
Abstract
AIMS/HYPOTHESIS Transcription factor 7-like 2 (TCF7L2) is a high mobility group (HMG) box-containing transcription factor and downstream effector of the Wnt signalling pathway. SNPs in the TCF7L2 gene have previously been associated with an increased risk of type 2 diabetes in genome-wide association studies. In animal studies, loss of Tcf7l2 function is associated with defective islet beta cell function and survival. Here, we explore the role of TCF7L2 in the control of the counter-regulatory response to hypoglycaemia by generating mice with selective deletion of the Tcf7l2 gene in pancreatic alpha cells. METHODS Alpha cell-selective deletion of Tcf7l2 was achieved by crossing mice with floxed Tcf7l2 alleles to mice bearing a Cre recombinase transgene driven by the preproglucagon promoter (PPGCre), resulting in Tcf7l2AKO mice. Glucose homeostasis and hormone secretion in vivo and in vitro, and islet cell mass were measured using standard techniques. RESULTS While glucose tolerance was unaffected in Tcf7l2AKO mice, glucose infusion rates were increased (AUC for glucose during the first 60 min period of hyperinsulinaemic-hypoglycaemic clamp test was increased by 1.98 ± 0.26-fold [p < 0.05; n = 6] in Tcf7l2AKO mice vs wild-type mice) and glucagon secretion tended to be lower (plasma glucagon: 0.40 ± 0.03-fold vs wild-type littermate controls [p < 0.01; n = 6]). Tcf7l2AKO mice displayed reduced fasted plasma glucose concentration. Glucagon release at low glucose was impaired in islets isolated from Tcf7l2AKO mice (0.37 ± 0.02-fold vs islets from wild-type littermate control mice [p < 0.01; n = 6). Alpha cell mass was also reduced (72.3 ± 20.3% [p < 0.05; n = 7) in Tcf7l2AKO mice compared with wild-type mice. CONCLUSIONS/INTERPRETATION The present findings demonstrate an alpha cell-autonomous role for Tcf7l2 in the control of pancreatic glucagon secretion and the maintenance of alpha cell mass and function.
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Affiliation(s)
- Gabriela da Silva Xavier
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, W12 0NN, UK.
| | - Angeles Mondragon
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, W12 0NN, UK
| | - Vishnou Mourougavelou
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, W12 0NN, UK
| | | | - Jessica Denom
- Université Paris Diderot Paris 7 - CNRS UMR 8251, Paris, France
| | - Pedro Luis Herrera
- Department of Genetic Medicine & Development, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | | | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, W12 0NN, UK
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Chen J, De Raeymaecker J, Hovgaard JB, Smaardijk S, Vandecaetsbeek I, Wuytack F, Møller JV, Eggermont J, De Maeyer M, Christensen SB, Vangheluwe P. Structure/activity relationship of thapsigargin inhibition on the purified Golgi/secretory pathway Ca 2+/Mn 2+-transport ATPase (SPCA1a). J Biol Chem 2017; 292:6938-6951. [PMID: 28264934 DOI: 10.1074/jbc.m117.778431] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 03/02/2017] [Indexed: 12/11/2022] Open
Abstract
The Golgi/secretory pathway Ca2+/Mn2+-transport ATPase (SPCA1a) is implicated in breast cancer and Hailey-Hailey disease. Here, we purified recombinant human SPCA1a from Saccharomyces cerevisiae and measured Ca2+-dependent ATPase activity following reconstitution in proteoliposomes. The purified SPCA1a displays a higher apparent Ca2+ affinity and a lower maximal turnover rate than the purified sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA1a). The lipids cholesteryl hemisuccinate, linoleamide/oleamide, and phosphatidylethanolamine inhibit and phosphatidic acid and sphingomyelin enhance SPCA1a activity. Moreover, SPCA1a is blocked by micromolar concentrations of the commonly used SERCA1a inhibitors thapsigargin (Tg), cyclopiazonic acid, and 2,5-di-tert-butylhydroquinone. Because tissue-specific targeting of SERCA2b by Tg analogues is considered for prostate cancer therapy, the inhibition of SPCA1a by Tg might represent an off-target risk. We assessed the structure-activity relationship (SAR) of Tg for SPCA1a by in silico modeling, site-directed mutagenesis, and measuring the potency of a series of Tg analogues. These indicate that Tg and the analogues are bound via the Tg scaffold but with lower affinity to the same homologous cavity as on the membrane surface of SERCA1a. The lower Tg affinity may depend on a more flexible binding cavity in SPCA1a, with low contributions of the Tg O-3, O-8, and O-10 chains to the binding energy. Conversely, the protein interaction of the Tg O-2 side chain with SPCA1a appears comparable with that of SERCA1a. These differences define a SAR of Tg for SPCA1a distinct from that of SERCA1a, indicating that Tg analogues with a higher specificity for SPCA1a can probably be developed.
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Affiliation(s)
- Jialin Chen
- From the Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, and
| | - Joren De Raeymaecker
- Biochemistry, Molecular and Structural Biology Section, Department of Chemistry, KU Leuven, 3000 Leuven, Belgium
| | - Jannik Brøndsted Hovgaard
- the Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen, Denmark, and
| | - Susanne Smaardijk
- From the Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, and
| | - Ilse Vandecaetsbeek
- From the Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, and
| | - Frank Wuytack
- From the Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, and
| | | | - Jan Eggermont
- From the Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, and
| | - Marc De Maeyer
- Biochemistry, Molecular and Structural Biology Section, Department of Chemistry, KU Leuven, 3000 Leuven, Belgium
| | - Søren Brøgger Christensen
- the Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen, Denmark, and
| | - Peter Vangheluwe
- From the Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, and
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Li LH, Tian XR, Jiang Z, Zeng LW, He WF, Hu ZP. The Golgi Apparatus: Panel Point of Cytosolic Ca(2+) Regulation. Neurosignals 2016; 21:272-84. [PMID: 23796968 DOI: 10.1159/000350471] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 03/05/2013] [Indexed: 12/21/2022] Open
Abstract
The Golgi apparatus (GA), an intermediate organelle of the cell inner membrane system, plays a key role in protein glycosylation and secretion. In recent years, this organelle has been found to act as a vital intracellular Ca(2+) store because different Ca (2+) regulators, such as the inositol-1,4,5-triphosphate receptor, sarco/endoplasmic reticulum Ca(2+) -ATPase and secretory pathway Ca 2+ -ATPase, were demonstrated to localize on their membrane. The mechanisms involved in Ca(2+) release and uptake in the GA have now been established.Here, based on careful backward looking on compartments and patterns in GA Ca (2+) regulation, we review neurological diseases related to GA calcium remodeling and propose a modified cytosolic Ca(2+) adjustment model, in which GA acts as part of the panel point.
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Affiliation(s)
- Li-Hua Li
- Department of Neurology, Second Xiangya Hospital, Central-South University, Changsha; School of Medicine, Jishou University, Jishou , PR China
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Scheinman EJ, Damouni R, Caspi A, Shen-Orr Z, Tiosano D, LeRoith D. The beneficial effect of growth hormone treatment on islet mass in streptozotocin-treated mice. Diabetes Metab Res Rev 2015; 31:492-9. [PMID: 25529355 DOI: 10.1002/dmrr.2631] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Accepted: 12/09/2014] [Indexed: 12/22/2022]
Abstract
BACKGROUND Type 1 diabetes is an autoimmune disease, characterized by a loss of pancreatic β-cell mass and function, which results in dramatic reductions in insulin secretion and circulating insulin levels. Patients with type 1 diabetes are traditionally treated with insulin injections and insulin pumps ex vivo or undergo transplantation. Growth hormone (GH) has been shown to be involved in β-cell function and survival in culture. METHODS Twelve-week-old female C57BL/6 mice were treated with streptozotocin and monitored for their weight and blood glucose levels. Fourteen days post-initial injection, these mice were separated into two groups at random. One group was treated with GH while the other treated with vehicle for up to 3 weeks. These mice were compared with mice not treated with streptozotocin. RESULTS Under our experimental conditions, we observed that mice treated with GH had larger islets and higher serum insulin levels than streptozotocin-treated mice treated with saline (0.288 vs. 0.073 ng/mL, p < 0.01). CONCLUSIONS Our data demonstrate that GH may rescue islets and therefore may possess therapeutic potential in the treatment of type 1 diabetes, although consideration should be made regarding GH's effect on insulin resistance.
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Affiliation(s)
- Eyal J Scheinman
- The Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Rawan Damouni
- The Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Avishay Caspi
- Diabetes and Metabolism Clinical Research Center of Excellence, Clinical Research Institute at Rambam (CRIR), Rambam Health Care Campus, Haifa, Israel
| | - Zila Shen-Orr
- Diabetes and Metabolism Clinical Research Center of Excellence, Clinical Research Institute at Rambam (CRIR), Rambam Health Care Campus, Haifa, Israel
| | - Dov Tiosano
- The Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
- Pediatric Endocrinology Unit, Meyer Children's Hospital, Rambam Health Care Campus, Haifa, Israel
| | - Derek LeRoith
- The Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
- Diabetes and Metabolism Clinical Research Center of Excellence, Clinical Research Institute at Rambam (CRIR), Rambam Health Care Campus, Haifa, Israel
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14
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Pancreatic β-cell identity, glucose sensing and the control of insulin secretion. Biochem J 2015; 466:203-18. [PMID: 25697093 DOI: 10.1042/bj20141384] [Citation(s) in RCA: 251] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Insulin release from pancreatic β-cells is required to maintain normal glucose homoeostasis in man and many other animals. Defective insulin secretion underlies all forms of diabetes mellitus, a disease currently reaching epidemic proportions worldwide. Although the destruction of β-cells is responsible for Type 1 diabetes (T1D), both lowered β-cell mass and loss of secretory function are implicated in Type 2 diabetes (T2D). Emerging results suggest that a functional deficiency, involving de-differentiation of the mature β-cell towards a more progenitor-like state, may be an important driver for impaired secretion in T2D. Conversely, at least in rodents, reprogramming of islet non-β to β-cells appears to occur spontaneously in models of T1D, and may occur in man. In the present paper, we summarize the biochemical properties which define the 'identity' of the mature β-cell as a glucose sensor par excellence. In particular, we discuss the importance of suppressing a group of 11 'disallowed' housekeeping genes, including Ldha and the monocarboxylate transporter Mct1 (Slc16a1), for normal nutrient sensing. We then survey the changes in the expression and/or activity of β-cell-enriched transcription factors, including FOXO1, PDX1, NKX6.1, MAFA and RFX6, as well as non-coding RNAs, which may contribute to β-cell de-differentiation and functional impairment in T2D. The relevance of these observations for the development of new approaches to treat T1D and T2D is considered.
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15
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Gilon P, Chae HY, Rutter GA, Ravier MA. Calcium signaling in pancreatic β-cells in health and in Type 2 diabetes. Cell Calcium 2014; 56:340-61. [DOI: 10.1016/j.ceca.2014.09.001] [Citation(s) in RCA: 116] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/26/2014] [Accepted: 09/01/2014] [Indexed: 12/24/2022]
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16
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Mo GX, Bai XW, Li ZJ, Yan XW, He XQ, Rong MQ. A Novel Insulinotropic Peptide from the Skin Secretions of Amolops loloensis Frog. NATURAL PRODUCTS AND BIOPROSPECTING 2014; 4:309-13. [PMID: 25294221 PMCID: PMC4199949 DOI: 10.1007/s13659-014-0037-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 08/21/2014] [Indexed: 05/12/2023]
Abstract
Various kinds of biologically active peptides have previously been isolated from the skin secretions of Amolops loloensis frog, such as antimicrobial peptides, bradykinin-like peptides and algesic peptides. A novel insulinotropic peptide named amolopin was identified in A. loloensis frog's skin secretion. Its primary structure sequence was determined by Edman degradation as: FLPIVGKSLSGLSGKL-NH2. BLAST search indicates that the amino acid sequence of amolopin is quite different from other known insulin secretagogues, including mastoparan, exendins and α-latrotoxin, nor does it like incretins (e.g. glucagons like peptide-1 and glucose-dependent insulinotropic ploypeptide) either. However, amolopin shows certain structural similarity with amphibian antimicrobial temporins and vespid chemotactic peptides isolated from Vespa magnifica. Amolopin can stimulate insulin release in INS-1 cells in a dose-dependent manner. Primary investigation on its action mechanisms reveals that amolopin does not increase the influx of Ca(2+). In conclusion, a novel 16-amino acid peptide with insulin-releasing activity is initially discovered from the skin secretion of A. loloensis frog. Further work is necessary to evaluate its potential as novel anti-diabetic candidate.
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Affiliation(s)
- Guo-Xiang Mo
- School of Biological Sciences, Nanjing Agriculture University, Nanjing, 210095 Jiangshu China
| | - Xue-Wei Bai
- School of Biological Sciences, Nanjing Agriculture University, Nanjing, 210095 Jiangshu China
| | - Zong-Jie Li
- School of Biological Sciences, Nanjing Agriculture University, Nanjing, 210095 Jiangshu China
| | - Xiu-Wen Yan
- School of Biological Sciences, Nanjing Agriculture University, Nanjing, 210095 Jiangshu China
| | - Xiao-Qing He
- Kunming Institue of Zoology, Chinese Academy of Sciences, Kunming, 650223 Yunnan China
| | - Ming-Qiang Rong
- Kunming Institue of Zoology, Chinese Academy of Sciences, Kunming, 650223 Yunnan China
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17
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Zatyka M, Da Silva Xavier G, Bellomo EA, Leadbeater W, Astuti D, Smith J, Michelangeli F, Rutter GA, Barrett TG. Sarco(endo)plasmic reticulum ATPase is a molecular partner of Wolfram syndrome 1 protein, which negatively regulates its expression. Hum Mol Genet 2014; 24:814-27. [PMID: 25274773 DOI: 10.1093/hmg/ddu499] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Wolfram syndrome is an autosomal recessive disorder characterized by neurodegeneration and diabetes mellitus. The gene responsible for the syndrome (WFS1) encodes an endoplasmic reticulum (ER)-resident transmembrane protein that is involved in the regulation of the unfolded protein response (UPR), intracellular ion homeostasis, cyclic adenosine monophosphate production and regulation of insulin biosynthesis and secretion. In this study, single cell Ca(2+) imaging with fura-2 and direct measurements of free cytosolic ATP concentration ([ATP]CYT) with adenovirally expressed luciferase confirmed a reduced and delayed rise in cytosolic free Ca(2+) concentration ([Ca(2+)]CYT), and additionally, diminished [ATP]CYT rises in response to elevated glucose concentrations in WFS1-depleted MIN6 cells. We also observed that sarco(endo)plasmic reticulum ATPase (SERCA) expression was elevated in several WFS1-depleted cell models and primary islets. We demonstrated a novel interaction between WFS1 and SERCA by co-immunoprecipitation in Cos7 cells and with endogenous proteins in human neuroblastoma cells. This interaction was reduced when cells were treated with the ER stress inducer dithiothreitol. Treatment of WFS1-depleted neuroblastoma cells with the proteasome inhibitor MG132 resulted in reduced accumulation of SERCA levels compared with wild-type cells. Together these results reveal a role for WFS1 in the negative regulation of SERCA and provide further insights into the function of WFS1 in calcium homeostasis.
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Affiliation(s)
| | - Gabriela Da Silva Xavier
- Department of Cell Biology, Division of Medicine, Faculty of Medicine, Imperial Centre for Translation and Experimental Medicine, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Elisa A Bellomo
- Department of Cell Biology, Division of Medicine, Faculty of Medicine, Imperial Centre for Translation and Experimental Medicine, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | | | - Dewi Astuti
- Department of Medical and Molecular Genetics
| | - Joel Smith
- Department of Medical and Molecular Genetics
| | - Frank Michelangeli
- School of Clinical and Experimental Medicine, The Medical School School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK and
| | - Guy A Rutter
- Department of Cell Biology, Division of Medicine, Faculty of Medicine, Imperial Centre for Translation and Experimental Medicine, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
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Wong AKC, Capitanio P, Lissandron V, Bortolozzi M, Pozzan T, Pizzo P. Heterogeneity of Ca2+ handling among and within Golgi compartments. J Mol Cell Biol 2014; 5:266-76. [PMID: 23918284 DOI: 10.1093/jmcb/mjt024] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The Golgi apparatus (GA) is a dynamic intracellular Ca(2+) store endowed with complex Ca(2+) homeostatic mechanisms in part distinct from those of the endoplasmic reticulum (ER). We describe the generation of a novel fluorescent Ca(2+) probe selectively targeted to the medial-Golgi. We demonstrate that in the medial-Golgi: (i) Ca(2+) accumulation takes advantage of two distinct pumps, the sarco/endoplasmic reticulum Ca(2+) ATPase and the secretory pathway Ca(2+) ATPase1; (ii) activation of IP3 or ryanodine receptors causes Ca(2+) release, while no functional two-pore channel was found; (iii) luminal Ca(2+) concentration appears higher than that of the trans-Golgi, but lower than that of the ER, suggesting the existence of a cis- to trans-Golgi Ca(2+) concentration gradient. Thus, the GA represents a Ca(2+) store of high complexity where, despite the continuous flow of membranes and luminal contents, each sub-compartment maintains its Ca(2+) identity with specific Ca(2+) homeostatic characteristics. The functional role of such micro-heterogeneity in GA Ca(2+) handling is discussed.
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Affiliation(s)
- Andrea K C Wong
- Department of Biomedical Sciences, University of Padua, 35121 Padua, Italy
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19
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Vuckovic D, Dagley LF, Purcell AW, Emili A. Membrane proteomics by high performance liquid chromatography-tandem mass spectrometry: Analytical approaches and challenges. Proteomics 2013; 13:404-23. [DOI: 10.1002/pmic.201200340] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 09/24/2012] [Accepted: 10/09/2012] [Indexed: 01/01/2023]
Affiliation(s)
- Dajana Vuckovic
- Banting and Best Department of Medical Research; Terrence Donnelly Centre for Cellular and Biomolecular Research; University of Toronto; Toronto ON Canada
| | - Laura F. Dagley
- Banting and Best Department of Medical Research; Terrence Donnelly Centre for Cellular and Biomolecular Research; University of Toronto; Toronto ON Canada
- Department of Biochemistry and Molecular Biology; Bio21 Molecular Science and Biotechnology Institute; University of Melbourne; Parkville Victoria Australia
| | - Anthony W. Purcell
- Department of Biochemistry and Molecular Biology; Bio21 Molecular Science and Biotechnology Institute; University of Melbourne; Parkville Victoria Australia
- Department of Biochemistry and Molecular Biology; Monash University; Clayton Victoria Australia
| | - Andrew Emili
- Banting and Best Department of Medical Research; Terrence Donnelly Centre for Cellular and Biomolecular Research; University of Toronto; Toronto ON Canada
- Department of Molecular Genetics; University of Toronto; Toronto ON Canada
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20
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Profiling of kidney vascular endothelial cell plasma membrane proteins by liquid chromatography-tandem mass spectrometry. Clin Exp Nephrol 2012; 17:327-37. [PMID: 23229650 PMCID: PMC3684716 DOI: 10.1007/s10157-012-0708-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 10/01/2012] [Indexed: 11/14/2022]
Abstract
Background Vascular endothelial cells (VECs) play crucial roles in physiological and pathologic conditions in tissues and organs. Most of these roles are related to VEC plasma membrane proteins. In the kidney, VECs are closely associated with structures and functions; however, plasma membrane proteins in kidney VECs remain to be fully elucidated. Methods Rat kidneys were perfused with cationic colloidal silica nanoparticles (CCSN) to label the VEC plasma membrane. The CCSN-labeled plasma membrane fraction was collected by gradient ultracentrifugation. The VEC plasma membrane or whole-kidney lysate proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and digested with trypsin in gels for liquid chromatography–tandem mass spectrometry. Enrichment analysis was then performed. Results The VEC plasma membrane proteins were purified by the CCSN method with high yield (approximately 20 μg from 1 g of rat kidney). By Mascot search, 582 proteins were identified in the VEC plasma membrane fraction, and 1,205 proteins were identified in the kidney lysate. In addition to 16 VEC marker proteins such as integrin beta-1 and intercellular adhesion molecule-2 (ICAM-2), 8 novel proteins such as Deltex 3-like protein and phosphatidylinositol binding clathrin assembly protein (PICALM) were identified. As expected, many key functions of plasma membranes in general and of endothelial cells in particular (i.e., leukocyte adhesion) were significantly overrepresented in the proteome of CCSN-labeled kidney VEC fraction. Conclusions The CCSN method is a reliable technique for isolation of VEC plasma membrane from the kidney, and proteomic analysis followed by bioinformatics revealed the characteristics of in vivo VECs in the kidney. Electronic supplementary material The online version of this article (doi:10.1007/s10157-012-0708-1) contains supplementary material, which is available to authorized users.
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21
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Andreux PA, Williams EG, Koutnikova H, Houtkooper RH, Champy MF, Henry H, Schoonjans K, Williams RW, Auwerx J. Systems genetics of metabolism: the use of the BXD murine reference panel for multiscalar integration of traits. Cell 2012; 150:1287-99. [PMID: 22939713 DOI: 10.1016/j.cell.2012.08.012] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 06/06/2012] [Accepted: 08/03/2012] [Indexed: 01/22/2023]
Abstract
Metabolic homeostasis is achieved by complex molecular and cellular networks that differ significantly among individuals and are difficult to model with genetically engineered lines of mice optimized to study single gene function. Here, we systematically acquired metabolic phenotypes by using the EUMODIC EMPReSS protocols across a large panel of isogenic but diverse strains of mice (BXD type) to study the genetic control of metabolism. We generated and analyzed 140 classical phenotypes and deposited these in an open-access web service for systems genetics (www.genenetwork.org). Heritability, influence of sex, and genetic modifiers of traits were examined singly and jointly by using quantitative-trait locus (QTL) and expression QTL-mapping methods. Traits and networks were linked to loci encompassing both known variants and novel candidate genes, including alkaline phosphatase (ALPL), here linked to hypophosphatasia. The assembled and curated phenotypes provide key resources and exemplars that can be used to dissect complex metabolic traits and disorders.
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Affiliation(s)
- Pénélope A Andreux
- Laboratory of Integrative and Systems Physiology, School of Life Sciences, École Polytechnique Fédérale de Lausanne 1015, Switzerland
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22
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Bis(2-hydroxy-3-tert-butyl-5-methyl-phenyl)-methane (bis-phenol) is a potent and selective inhibitor of the secretory pathway Ca2+ ATPase (SPCA1). Biochem Biophys Res Commun 2012; 424:616-9. [DOI: 10.1016/j.bbrc.2012.07.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 07/02/2012] [Indexed: 11/22/2022]
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Leoni L, Dhyani A, La Riviere P, Vogt S, Lai B, Roman BB. β-Cell subcellular localization of glucose-stimulated Mn uptake by X-ray fluorescence microscopy: implications for pancreatic MRI. CONTRAST MEDIA & MOLECULAR IMAGING 2012; 6:474-81. [PMID: 22144025 DOI: 10.1002/cmmi.447] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Manganese (Mn) is a calcium (Ca) analog that has long been used as a magnetic resonance imaging (MRI) contrast agent for investigating cardiac tissue functionality, for brain mapping and for neuronal tract tracing studies. Recently, we have extended its use to investigate pancreatic β-cells and showed that, in the presence of MnCl(2), glucose-activated pancreatic islets yield significant signal enhancement in T(1)-weigheted MR images. In this study, we exploited for the first time the unique capabilities of X-ray fluorescence microscopy (XFM) to both visualize and quantify the metal in pancreatic β-cells at cellular and subcellular levels. MIN-6 insulinoma cells grown in standard tissue culture conditions had only a trace amount of Mn, 1.14 ± 0.03 × 10(-11)µg/µm(2), homogenously distributed across the cell. Exposure to 2 mM glucose and 50 µM MnCl(2) for 20 min resulted in nonglucose-dependent Mn uptake and the overall cell concentration increased to 8.99 ± 2.69 × 10(-11) µg/µm(2). When cells were activated by incubation in 16 mM glucose in the presence of 50 µM MnCl(2), a significant increase in cytoplasmic Mn was measured, reaching 2.57 ± 1.34 × 10(-10) µg/µm(2). A further rise in intracellular concentration was measured following KCl-induced depolarization, with concentrations totaling 1.25 ± 0.33 × 10(-9) and 4.02 ± 0.71 × 10(-10) µg/µm(2) in the cytoplasm and nuclei, respectively. In both activated conditions Mn was prevalent in the cytoplasm and localized primarily in a perinuclear region, possibly corresponding to the Golgi apparatus and involving the secretory pathway. These data are consistent with our previous MRI findings, confirming that Mn can be used as a functional imaging reporter of pancreatic β-cell activation and also provide a basis for understanding how subcellular localization of Mn will impact MRI contrast.
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Affiliation(s)
- Lara Leoni
- Department of Radiology, Committee on Medical Physics, University of Chicago, Chicago, IL 60637, USA
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24
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Zampese E, Pizzo P. Intracellular organelles in the saga of Ca2+ homeostasis: different molecules for different purposes? Cell Mol Life Sci 2012; 69:1077-104. [PMID: 21968921 PMCID: PMC11114864 DOI: 10.1007/s00018-011-0845-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 09/15/2011] [Accepted: 09/19/2011] [Indexed: 11/28/2022]
Abstract
An increase in the concentration of cytosolic free Ca(2+) is a key component regulating different cellular processes ranging from egg fertilization, active secretion and movement, to cell differentiation and death. The multitude of phenomena modulated by Ca(2+), however, do not simply rely on increases/decreases in its concentration, but also on specific timing, shape and sub-cellular localization of its signals that, combined together, provide a huge versatility in Ca(2+) signaling. Intracellular organelles and their Ca(2+) handling machineries exert key roles in this complex and precise mechanism, and this review will try to depict a map of Ca(2+) routes inside cells, highlighting the uniqueness of the different Ca(2+) toolkit components and the complexity of the interactions between them.
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Affiliation(s)
- Enrico Zampese
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy
| | - Paola Pizzo
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy
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Shevchenko G, Musunuri S, Wetterhall M, Bergquist J. Comparison of Extraction Methods for the Comprehensive Analysis of Mouse Brain Proteome using Shotgun-based Mass Spectrometry. J Proteome Res 2012; 11:2441-51. [DOI: 10.1021/pr201169q] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ganna Shevchenko
- Department of Physical
and Analytical Chemistry, Analytical Chemistry, Uppsala University, Uppsala, Sweden
| | - Sravani Musunuri
- Department of Physical
and Analytical Chemistry, Analytical Chemistry, Uppsala University, Uppsala, Sweden
| | - Magnus Wetterhall
- Department of Physical
and Analytical Chemistry, Analytical Chemistry, Uppsala University, Uppsala, Sweden
| | - Jonas Bergquist
- Department of Physical
and Analytical Chemistry, Analytical Chemistry, Uppsala University, Uppsala, Sweden
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Micaroni M. Calcium around the Golgi apparatus: implications for intracellular membrane trafficking. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:439-60. [PMID: 22453953 DOI: 10.1007/978-94-007-2888-2_18] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
As with other complex cellular functions, intracellular membrane transport involves the coordinated engagement of a series of organelles and machineries; in the last couple of decades more importance has been given to the role of calcium (Ca(2+)) in the regulation of membrane trafficking, which is directly involved in coordinating the endoplasmic reticulum-to-Golgi-to-plasma membrane delivery of cargo. Consequently, the Golgi apparatus (GA) is now considered not just the place proteins mature in as they move to their final destination(s), but it is increasingly viewed as an intracellular Ca(2+) store. In the last few years the mechanisms regulating the homeostasis of Ca(2+) in the GA and its role in membrane trafficking have begun to be elucidated. Here, these recent discoveries that shed light on the role Ca(2+) plays as of trigger of different steps during membrane trafficking has been reviewed. This includes recruitment of proteins and SNARE cofactors to the Golgi membranes, which are both fundamental for the membrane remodeling and the regulation of fusion/fission events occurring during the passage of cargo across the GA. I conclude by focusing attention on Ca(2+) homeostasis dysfunctions in the GA and their related pathological implications.
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Affiliation(s)
- Massimo Micaroni
- Division of Molecular Cell Biology, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, 4072 Brisbane, St. Lucia, QLD, Australia.
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The Role of the Golgi-Resident SPCA Ca2+/Mn2+ Pump in Ionic Homeostasis and Neural Function. Neurochem Res 2011; 37:455-68. [DOI: 10.1007/s11064-011-0644-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 10/28/2011] [Accepted: 11/02/2011] [Indexed: 12/23/2022]
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Ravier MA, Daro D, Roma LP, Jonas JC, Cheng-Xue R, Schuit FC, Gilon P. Mechanisms of control of the free Ca2+ concentration in the endoplasmic reticulum of mouse pancreatic β-cells: interplay with cell metabolism and [Ca2+]c and role of SERCA2b and SERCA3. Diabetes 2011; 60:2533-45. [PMID: 21885870 PMCID: PMC3178295 DOI: 10.2337/db10-1543] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Sarco-endoplasmic reticulum Ca(2+)-ATPase 2b (SERCA2b) and SERCA3 pump Ca(2+) in the endoplasmic reticulum (ER) of pancreatic β-cells. We studied their role in the control of the free ER Ca(2+) concentration ([Ca(2+)](ER)) and the role of SERCA3 in the control of insulin secretion and ER stress. RESEARCH DESIGN AND METHODS β-Cell [Ca(2+)](ER) of SERCA3(+/+) and SERCA3(-/-) mice was monitored with an adenovirus encoding the low Ca(2+)-affinity sensor D4 addressed to the ER (D4ER) under the control of the insulin promoter. Free cytosolic Ca(2+) concentration ([Ca(2+)](c)) and [Ca(2+)](ER) were simultaneously recorded. Insulin secretion and mRNA levels of ER stress genes were studied. RESULTS Glucose elicited synchronized [Ca(2+)](ER) and [Ca(2+)](c) oscillations. [Ca(2+)](ER) oscillations were smaller in SERCA3(-/-) than in SERCA3(+/+) β-cells. Stimulating cell metabolism with various [glucose] in the presence of diazoxide induced a similar dose-dependent [Ca(2+)](ER) rise in SERCA3(+/+) and SERCA3(-/-) β-cells. In a Ca(2+)-free medium, glucose moderately raised [Ca(2+)](ER) from a highly buffered cytosolic Ca(2+) pool. Increasing [Ca(2+)](c) with high [K] elicited a [Ca(2+)](ER) rise that was larger but more transient in SERCA3(+/+) than SERCA3(-/-) β-cells because of the activation of a Ca(2+) release from the ER in SERCA3(+/+) β-cells. Glucose-induced insulin release was larger in SERCA3(-/-) than SERCA3(+/+) islets. SERCA3 ablation did not induce ER stress. CONCLUSIONS [Ca(2+)](c) and [Ca(2+)](ER) oscillate in phase in response to glucose. Upon [Ca(2+)](c) increase, Ca(2+) is taken up by SERCA2b and SERCA3. Strong Ca(2+) influx triggers a Ca(2+) release from the ER that depends on SERCA3. SERCA3 deficiency neither impairs Ca(2+) uptake by the ER upon cell metabolism acceleration and insulin release nor induces ER stress.
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Affiliation(s)
- Magalie A. Ravier
- Pole d’Endocrinologie, Diabète, et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
- Institut de Génomique Fonctionnelle, CNRS UMR-5203, INSERM U661, Universités de Montpellier 1 et 2, Montpellier, France
| | - Dorothée Daro
- Pole d’Endocrinologie, Diabète, et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Leticia Prates Roma
- Pole d’Endocrinologie, Diabète, et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Jean-Christophe Jonas
- Pole d’Endocrinologie, Diabète, et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Rui Cheng-Xue
- Pole d’Endocrinologie, Diabète, et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Frans C. Schuit
- Gene Expression Unit, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Patrick Gilon
- Pole d’Endocrinologie, Diabète, et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
- Corresponding author: Patrick Gilon,
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Ca2+ signalling in the Golgi apparatus. Cell Calcium 2011; 50:184-92. [DOI: 10.1016/j.ceca.2011.01.006] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 01/11/2011] [Accepted: 01/12/2011] [Indexed: 11/20/2022]
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Gao P, Jiao Y, Xiong Q, Wang CY, Gerling I, Gu W. Genetic and Molecular Basis of QTL of Diabetes in Mouse: Genes and Polymorphisms. Curr Genomics 2011; 9:324-37. [PMID: 19471607 PMCID: PMC2685644 DOI: 10.2174/138920208785133253] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 04/14/2008] [Accepted: 04/17/2008] [Indexed: 12/14/2022] Open
Abstract
A systematic study has been conducted of all available reports in PubMed and OMIM (Online Mendelian Inheritance in Man) to examine the genetic and molecular basis of quantitative genetic loci (QTL) of diabetes with the main focus on genes and polymorphisms. The major question is, What can the QTL tell us? Specifically, we want to know whether those genome regions differ from other regions in terms of genes relevant to diabetes. Which genes are within those QTL regions, and, among them, which genes have already been linked to diabetes? whether more polymorphisms have been associated with diabetes in the QTL regions than in the non-QTL regions. Our search revealed a total of 9038 genes from 26 type 1 diabetes QTL, which cover 667,096,006 bp of the mouse genomic sequence. On one hand, a large number of candidate genes are in each of these QTL; on the other hand, we found that some obvious candidate genes of QTL have not yet been investigated. Thus, the comprehensive search of candidate genes for known QTL may provide unexpected benefit for identifying QTL genes for diabetes.
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Affiliation(s)
- Peng Gao
- Departments of Orthopaedic Surgery, Campbell Clinic and Pathology, University of Tennessee Health Science Center, Memphis, Tennessee, USA
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31
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Vandecaetsbeek I, Vangheluwe P, Raeymaekers L, Wuytack F, Vanoevelen J. The Ca2+ pumps of the endoplasmic reticulum and Golgi apparatus. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a004184. [PMID: 21441596 DOI: 10.1101/cshperspect.a004184] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The various splice variants of the three SERCA- and the two SPCA-pump genes in higher vertebrates encode P-type ATPases of the P(2A) group found respectively in the membranes of the endoplasmic reticulum and the secretory pathway. Of these, SERCA2b and SPCA1a represent the housekeeping isoforms. The SERCA2b form is characterized by a luminal carboxy terminus imposing a higher affinity for cytosolic Ca(2+) compared to the other SERCAs. This is mediated by intramembrane and luminal interactions of this extension with the pump. Other known affinity modulators like phospholamban and sarcolipin decrease the affinity for Ca(2+). The number of proteins reported to interact with SERCA is rapidly growing. Here, we limit the discussion to those for which the interaction site with the ATPase is specified: HAX-1, calumenin, histidine-rich Ca(2+)-binding protein, and indirectly calreticulin, calnexin, and ERp57. The role of the phylogenetically older and structurally simpler SPCAs as transporters of Ca(2+), but also of Mn(2+), is also addressed.
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Affiliation(s)
- Ilse Vandecaetsbeek
- Laboratory of Ca-transport ATPases, Department of Molecular Cell Biology, K.U. Leuven, Leuven, Belgium
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32
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Ravier MA, Cheng-Xue R, Palmer AE, Henquin JC, Gilon P. Subplasmalemmal Ca(2+) measurements in mouse pancreatic beta cells support the existence of an amplifying effect of glucose on insulin secretion. Diabetologia 2010; 53:1947-57. [PMID: 20461354 PMCID: PMC3297670 DOI: 10.1007/s00125-010-1775-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Accepted: 04/07/2010] [Indexed: 10/19/2022]
Abstract
AIMS/HYPOTHESIS Glucose-induced insulin secretion is attributed to a rise of beta cell cytosolic free [Ca(2+)] ([Ca(2+)](c)) (triggering pathway) and amplification of the action of Ca(2+). This concept of amplification rests on observations that glucose can increase Ca(2+)-induced insulin secretion without further elevating an imposed already high [Ca(2+)](c). However, it remains possible that this amplification results from an increase in [Ca(2+)] just under the plasma membrane ([Ca(2+)](SM)), which escaped detection by previous measurements of global [Ca(2+)](c). This was the hypothesis that we tested here by measuring [Ca(2+)](SM). METHODS The genetically encoded Ca(2+) indicators D3-cpv (untargeted) and LynD3-cpv (targeted to plasma membrane) were expressed in clusters of mouse beta cells. LynD3-cpv was also expressed in beta cells within intact islets. [Ca(2+)](SM) changes were monitored using total internal reflection fluorescence microscopy. Insulin secretion was measured in parallel. RESULTS Beta cells expressing D3cpv or LynD3cpv displayed normal [Ca(2+)] changes and insulin secretion in response to glucose. Distinct [Ca(2+)](SM) fluctuations were detected during repetitive variations of KCl between 30 and 32-35 mmol/l, attesting to the adequate sensitivity of our system. When the amplifying pathway was evaluated (high KCl + diazoxide), increasing glucose from 3 to 15 mmol/l consistently lowered [Ca(2+)](SM) while stimulating insulin secretion approximately two fold. Blocking Ca(2+) uptake by the endoplasmic reticulum largely attenuated the [Ca(2+)](SM) decrease produced by high glucose but did not unmask localised [Ca(2+)](SM) increases. CONCLUSIONS/INTERPRETATION Glucose can increase Ca(2+)-induced insulin secretion without causing further elevation of beta cell [Ca(2+)](SM). The phenomenon is therefore a true amplification of the triggering action of Ca(2+).
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Affiliation(s)
- M. A. Ravier
- Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, UCL 55.30, 1200 Brussels, Belgium
| | - R. Cheng-Xue
- Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, UCL 55.30, 1200 Brussels, Belgium
| | - A. E. Palmer
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA
| | - J. C. Henquin
- Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, UCL 55.30, 1200 Brussels, Belgium
| | - P. Gilon
- Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, UCL 55.30, 1200 Brussels, Belgium
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33
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Micaroni M, Perinetti G, Berrie CP, Mironov AA. The SPCA1 Ca2+ Pump and Intracellular Membrane Trafficking. Traffic 2010; 11:1315-33. [DOI: 10.1111/j.1600-0854.2010.01096.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Calcium signalling-dependent mitochondrial dysfunction and bioenergetics regulation in respiratory chain Complex II deficiency. Cell Death Differ 2010; 17:1855-66. [PMID: 20489732 DOI: 10.1038/cdd.2010.51] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Despite advanced knowledge on the genetic basis of oxidative phosphorylation-related diseases, the molecular and/or cellular determinants for tissue-specific dysfunction are not completely understood. Here, we report the cellular events associated with mitochondrial respiratory Complex II deficiency occurring before cell death. Mutation or chronic inhibition of Complex II determined a large increase of basal and agonist-evoked Ca(2+) signals in the cytosol and the mitochondria, in parallel with mitochondrial dysfunction characterized by membrane potential (Δψ(mit)) loss, [ATP] reduction and increased reactive oxygen species production. Cytosolic and mitochondrial Ca(2+) overload are linked to increased endoplasmic reticulum (ER) Ca(2+) leakage, and to SERCA2b and PMCA proteasome-dependent degradation. Increased [Ca(2+)](mit) is also contributed by decreased mitochondrial motility and increased ER-mitochondria contact sites. Interestingly, increased intracellular [Ca(2+)] activated on the one hand a compensatory Ca(2+)-dependent glycolytic ATP production and determined on the second hand mitochondrial pathology. These results revealed the primary function for Ca(2+) signalling in the control of mitochondrial dysfunction and cellular bioenergetics outcomes linked to respiratory chain Complex II deficiency.
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35
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Elschenbroich S, Kim Y, Medin JA, Kislinger T. Isolation of cell surface proteins for mass spectrometry-based proteomics. Expert Rev Proteomics 2010; 7:141-54. [PMID: 20121483 DOI: 10.1586/epr.09.97] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Defining the cell surface proteome has profound importance for understanding cell differentiation and cell-cell interactions, as well as numerous pathogenic abnormalities. Owing to their hydrophobic nature, plasma membrane proteins that reside on the cell surface pose analytical challenges and, despite efforts to overcome difficulties, remain under-represented in proteomic studies. Limitations in the classically employed ultracentrifugation-based approaches have led to the invention of more elaborate techniques for the purification of cell surface proteins. Three of these methods--cell surface coating with cationic colloidal silica beads, biotinylation and chemical capture of surface glycoproteins--allow for marked enrichment of this subcellular proteome, with each approach offering unique advantages and characteristics for different experiments. In this article, we introduce the principles of each purification method and discuss applications from the recent literature.
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36
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Changes in expression and activity of the secretory pathway Ca2+ ATPase 1 (SPCA1) in A7r5 vascular smooth muscle cells cultured at different glucose concentrations. Biosci Rep 2009; 29:397-404. [PMID: 19527224 PMCID: PMC2752273 DOI: 10.1042/bsr20090058] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Diabetes mellitus-related vascular disease is often associated with both a dysregulation of Ca2+ homoeostasis and enhanced secretory activity in VSMCs (vascular smooth muscle cells). Here, we employ a commonly used rat cell line for VSMCs (A7r5 cells) to investigate the effects of glucose on the expression and activity of the SPCA1 (secretory pathway Ca2+-ATPase 1; also known as ATP2C1), which is a P-type Ca2+ pump located in the Golgi apparatus that plays a key role in the secretory pathway. Our results show that mRNA expression levels of SPCA1 are significantly increased in A7r5 cells cultured in high glucose (25.0 mM)-supplemented medium compared with normal glucose (5.55 mM)-supplemented medium. SPCA1 protein expression levels and thapsigargin-insensitive Ca2+-dependent ATPase activity were also consistent with a higher than normal expression level of SPCA1 in high-glucose-cultured A7r5 cells. Analysis of AVP (arginine-vasopressin)-induced cytosolic Ca2+ transients in A7r5 cells (after pre-treatment with thapsigargin) showed faster rise and decay phases in cells grown in high glucose medium compared with cells grown in normal glucose medium, supporting the observation of increased SPCA expression/activity. The significant levels of both Ca2+-ATPase activity and AVP-induced Ca2+ transients, in the presence of thapsigargin, indicate that SPCA must play a significant role in Ca2+ uptake within VSMCs. We therefore propose that, if such increases in SPCA expression and activity also occur in primary VSMCs, this may play a substantial role in the aetiology of diabetes mellitus-associated vascular disease, due to alterations in Ca2+ homoeostasis within the Golgi apparatus.
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37
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Vangheluwe P, Sepúlveda MR, Missiaen L, Raeymaekers L, Wuytack F, Vanoevelen J. Intracellular Ca2+- and Mn2+-Transport ATPases. Chem Rev 2009; 109:4733-59. [DOI: 10.1021/cr900013m] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Peter Vangheluwe
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - M. Rosario Sepúlveda
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Ludwig Missiaen
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Luc Raeymaekers
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Frank Wuytack
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Jo Vanoevelen
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
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38
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Abstract
Many studies of Ca2+ signaling use PC12 cells, yet the balance of Ca2+ clearance mechanisms in these cells is unknown. We used pharmacological inhibition of Ca2+ transporters to characterize Ca2+ clearance after depolarizations in both undifferentiated and nerve growth factor-differentiated PC12 cells. Sarco-endoplasmic reticulum Ca2+ ATPase (SERCA), plasma membrane Ca2+ ATPase (PMCA), and Na+/Ca2+ exchanger (NCX) account for almost all Ca2+ clearance in both cell states, with NCX and PMCA making the greatest contributions. Any contribution of mitochondrial uniporters is small. The ATP pool in differentiated cells was much more labile than that of undifferentiated cells in the presence of agents that dissipated mitochondrial proton gradients. Differentiated PC12 cells have a small component of Ca2+ clearance possessing pharmacological characteristics consistent with secretory pathway Ca2+ ATPase (SPCA), potentially residing on Golgi and/or secretory granules. Undifferentiated and differentiated cells are similar in overall Ca2+ transport and in the small transport due to SERCA, but they differ in the fraction of transport by PMCA and NCX. Transport in neurites of differentiated PC12 cells was qualitatively similar to that in the somata, except that the ER stores in neurites sometimes released Ca2+ instead of clearing it after depolarization. We formulated a mathematical model to simulate the observed Ca2+ clearance and to describe the differences between these undifferentiated and NGF-differentiated states quantitatively. The model required a value for the endogenous Ca2+ binding ratio of PC12 cell cytoplasm, which we measured to be 268 ± 85. Our results indicate that Ca2+ transport in undifferentiated PC12 cells is quite unlike transport in adrenal chromaffin cells, for which they often are considered models. Transport in both cell states more closely resembles that of sympathetic neurons, for which differentiated PC12 cells often are considered models. Comparison with other cell types shows that different cells emphasize different Ca2+ transport mechanisms.
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Affiliation(s)
- Joseph G Duman
- Department of Physiology and Biophysics University of Washington School of Medicine, Seattle, WA 98195, USA
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39
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Jewell JL, Luo W, Oh E, Wang Z, Thurmond DC. Filamentous actin regulates insulin exocytosis through direct interaction with Syntaxin 4. J Biol Chem 2008; 283:10716-26. [PMID: 18285343 DOI: 10.1074/jbc.m709876200] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucose-induced insulin exocytosis is coupled to associations between F-actin and SNARE proteins, although the nature and function of these interactions remains unknown. Toward this end we show here that both Syntaxin 1A and Syntaxin 4 associated with F-actin in MIN6 cells and that each interaction was rapidly and transiently diminished by stimulation of cells with d-glucose. Of the two isoforms, only Syntaxin 4 was capable of interacting directly with F-actin in an in vitro sedimentation assay, conferred by the N-terminal 39-112 residues of Syntaxin 4. The 39-112 fragment was capable of selective competitive inhibitory action, disrupting endogenous F-actin-Syntaxin 4 binding in MIN6 cells. Disruption of F-actin-Syntaxin 4 binding correlated with enhanced glucose-stimulated insulin secretion, mediated by increased granule accumulation at the plasma membrane and increased Syntaxin 4 accessibility under basal conditions. However, no increase in basal level Syntaxin 4-VAMP2 association occurred with either latrunculin treatment or expression of the 39-112 fragment. Taken together, these data disclose a new underlying mechanism by which F-actin negatively regulates exocytosis via binding and blocking Syntaxin 4 accessibility, but they also reveal the existence of additional signals and/or steps required to trigger the subsequent docking and fusion steps of exocytosis.
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Affiliation(s)
- Jenna L Jewell
- Department of Biochemistry and Molecular Biology, Center for Diabetes Research, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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40
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Sepúlveda MR, Berrocal M, Marcos D, Wuytack F, Mata AM. Functional and immunocytochemical evidence for the expression and localization of the secretory pathway Ca2+-ATPase isoform 1 (SPCA1) in cerebellum relative to other Ca2+ pumps. J Neurochem 2007; 103:1009-18. [PMID: 17680983 DOI: 10.1111/j.1471-4159.2007.04794.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Membrane fractions of pig cerebellum show Ca2+-ATPase activity and Ca2+ transport due to the presence of the secretory pathway Ca2+-ATPase (SPCA). The SPCA1 isoform shows a wide distribution in the neurons of pig cerebellum, where it is found in the Golgi complex of the soma of Purkinje, stellate, basket and granule cells, and also in more distal components of the secretory pathway associated with a synaptic localization such as in cerebellar glomeruli. The SPCA1 may be involved in loading the Golgi complex and the secretory vesicles of these specific neuronal cell types with Ca2+ and also Mn2+. This study of the cellular and subcellular localization of SPCA1 pumps relative to the sarco(endo) plasmic reticulum Ca2+-ATPase and plasma membrane Ca2+-ATPase pumps hints to a possible specific role of SPCA1 in controlling the luminal secretory pathway Ca2+ (or Mn2+) levels as well as the local cytosolic Ca2+ levels. In addition, it helps to specify the zones that are most vulnerable to Ca2+ and/or Mn2+ dyshomeostasis, a condition that is held responsible of an increasing number of neurological disorders.
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Affiliation(s)
- M Rosario Sepúlveda
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
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41
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Qiu J, Cheng F, Pintel D. Distance-dependent processing of adeno-associated virus type 5 RNA is controlled by 5' exon definition. J Virol 2007; 81:7974-84. [PMID: 17507471 PMCID: PMC1951275 DOI: 10.1128/jvi.00714-07] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adeno-associated virus type 5 (AAV5) is unique among human AAV serotypes in that it uses a polyadenylation site [(pA)p] within the single small intron in the center of the genome. We previously reported that inhibition of polyadenylation at (pA)p, necessary for read-through of P41-generated capsid gene pre-mRNAs which are subsequently spliced, requires binding of U1 snRNP to the upstream donor. Inhibition was reduced as the distance between the cap site and the donor was increased (increasing the size of the 5' exon). Here, we have demonstrated that U1-70K is a key component of U1 snRNP that mediates inhibition of polyadenylation at (pA)p. Furthermore, introduction of a U-rich stretch, predicted to target TIA-1 and thus increase the affinity of U1 snRNP binding to the intervening donor site, significantly augmented inhibition of (pA)p, while depletion of TIA-1 by siRNA increased (pA)p read-through. Finally, artificially tethering the cap binding complex (CBC) components CBP80 and CBP20 upstream of the intron donor increased inhibition of polyadenylation at (pA)p. Our results suggest that interaction with the CBC strengthens U1 snRNP binding to the downstream intron donor in a manner inversely proportional to the size of the 5' exon, thus governing the competition between intron splicing and polyadenylation at (pA)p. This competition must be optimized to program both the levels of polyadenylation of P7- and P19-generated RNA at (pA)p required to produce proper levels of the essential Rep proteins and the splicing of P41-generated RNAs to produce the proper ratio of capsid proteins during AAV5 infection.
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Affiliation(s)
- Jianming Qiu
- Department of Molecular Microbiology and Immunology, University of Missouri--Columbia, School of Medicine, Life Sciences Center, Columbia, Missouri 65212, USA
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42
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Missiaen L, Dode L, Vanoevelen J, Raeymaekers L, Wuytack F. Calcium in the Golgi apparatus. Cell Calcium 2007; 41:405-16. [PMID: 17140658 DOI: 10.1016/j.ceca.2006.11.001] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2006] [Revised: 10/30/2006] [Indexed: 11/16/2022]
Abstract
The secretory-pathway Ca2+-ATPases (SPCAs) represent a recently recognized family of phosphorylation-type ATPases that supply the lumen of the Golgi apparatus with Ca2+ and Mn2+ needed for the normal functioning of this structure. Mutations of the human SPCA1 gene (ATP2C1) cause Hailey-Hailey disease, an autosomal dominant skin disorder in which keratinocytes in the suprabasal layer of the epidermis detach. We will first review the physiology of the SPCAs and then discuss how mutated SPCA1 proteins can lead to an epidermal disorder.
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Affiliation(s)
- Ludwig Missiaen
- Afdeling Fysiologie, Departement Moleculaire Celbiologie, KULeuven Campus Gasthuisberg O/N, Herestraat 49 bus 802, B-3000 Leuven, Belgium.
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43
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Vanoevelen J, Dode L, Raeymaekers L, Wuytack F, Missiaen L. Diseases involving the Golgi calcium pump. Subcell Biochem 2007; 45:385-404. [PMID: 18193645 DOI: 10.1007/978-1-4020-6191-2_14] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Secretory-pathway Ca2(+)-transport ATPases (SPCA) provide the Golgi apparatus with Ca2+ and Mn2+ needed for the normal functioning of this organelle. Loss of one functional copy of the human SPCA1 gene (ATP2C1) causes Hailey-Hailey disease, a rare skin disorder characterized by recurrent blisters and erosions in the flexural areas. Here, we will review the properties and functional role of the SPCAs. The relationship between Hailey-Hailey disease and its defective gene (ATP2C1) will be adressed as well.
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Affiliation(s)
- J Vanoevelen
- Laboratory of Physiology, KULeuven Campus Gasthuisberg O&N1, Herestraat 49 bus 802, B-3000 Leuven, Belgium
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44
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Le Bihan T, Goh T, Stewart II, Salter AM, Bukhman YV, Dharsee M, Ewing R, Wiśniewski JR. Differential analysis of membrane proteins in mouse fore- and hindbrain using a label-free approach. J Proteome Res 2006; 5:2701-10. [PMID: 17022641 DOI: 10.1021/pr060190y] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ability to quantitatively compare protein levels across different regions of the brain to identify disease mechanisms remains a fundamental research challenge. It requires both a robust method to efficiently isolate proteins from small amounts of tissue and a differential technique that provides a sensitive and comprehensive analysis of these proteins. Here, we describe a proteomic approach for the quantitative mapping of membrane proteins between mouse fore- and hindbrain regions. The approach focuses primarily on a recently developed method for the fractionation of membranes and on-membrane protein digestion, but incorporates off-line SCX-fractionation of the peptide mixture and nano-LC-MS/MS analysis using an LTQ-FT-ICR instrument as part of the analytical method. Comparison of mass spectral peak intensities between samples, mapping of peaks to peptides and protein sequences, and statistical analysis were performed using in-house differential analysis software (DAS). In total, 1213 proteins were identified and 967 were quantified; 81% of the identified proteins were known membrane proteins and 38% of the protein sequences were predicted to contain transmembrane helices. Although this paper focuses primarily on characterizing the efficiency of this purification method from a typical sample set, for many of the quantified proteins such as glutamate receptors, GABA receptors, calcium channel subunits, and ATPases, the observed ratios of protein abundance were in good agreement with the known mRNA expression levels and/or intensities of immunostaining in rostral and caudal regions of murine brain. This suggests that the approach would be well-suited for incorporation in more rigorous, larger scale quantitative analysis designed to achieve biological significance.
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45
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Rutter GA, Tsuboi T, Ravier MA. Ca2+ microdomains and the control of insulin secretion. Cell Calcium 2006; 40:539-51. [PMID: 17030367 DOI: 10.1016/j.ceca.2006.08.015] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Accepted: 08/23/2006] [Indexed: 11/19/2022]
Abstract
Nutrient-induced increases in intracellular free Ca(2+) concentrations are the key trigger for insulin release from pancreatic islet beta-cells. These Ca(2+) changes are tightly regulated temporally, occurring as Ca(2+) influx-dependent baseline oscillations. We explore here the concept that locally high [Ca(2+)] concentrations (i.e. Ca(2+) microdomains) may control exocytosis via the recruitment of key effector proteins to sites of exocytosis. Importantly, recent advances in the development of organelle- and membrane-targeted green fluorescent protein (GFP-) or aequorin-based Ca(2+) indicators, as well as in rapid imaging techniques, are providing new insights into the potential role of these Ca(2+) microdomains in beta-cells. We summarise here some of the evidence indicating that Ca(2+) microdomains beneath the plasma membrane and at the surface of large dense core vesicles may be important in the normal regulation of insulin secretion, and may conceivably contribute to "ATP-sensitive K(+)-channel independent" effects of glucose. We also discuss evidence that, in contrast to certain non-excitable cells, direct transfer of Ca(2+) from the ER to mitochondria via localised physical contacts between these organelles is relatively less important for efficient mitochondrial Ca(2+) uptake in beta-cells. Finally, we discuss evidence from single cell imaging that increases in cytosolic Ca(2+) are not required for the upstroke of oscillations in mitochondrial redox state, but may underlie the reoxidation process.
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Affiliation(s)
- Guy A Rutter
- Department of Cell Biology, Division of Medicine, Imperial College London, Sir Alexander Fleming Building, London, UK.
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46
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Varadi A, Grant A, McCormack M, Nicolson T, Magistri M, Mitchell KJ, Halestrap AP, Yuan H, Schwappach B, Rutter GA. Intracellular ATP-sensitive K+ channels in mouse pancreatic beta cells: against a role in organelle cation homeostasis. Diabetologia 2006; 49:1567-77. [PMID: 16752175 DOI: 10.1007/s00125-006-0257-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2006] [Accepted: 02/28/2006] [Indexed: 11/30/2022]
Abstract
AIMS/HYPOTHESIS ATP-sensitive K(+) (K(ATP)) channels located on the beta cell plasma membrane play a critical role in regulating insulin secretion and are targets for the sulfonylurea class of antihyperglycaemic drugs. Recent reports suggest that these channels may also reside on insulin-containing dense-core vesicles and mitochondria. The aim of this study was to explore these possibilities and to test the hypothesis that vesicle-resident channels play a role in the control of organellar Ca(2+) concentration or pH. METHODS To quantify the subcellular distribution of the pore-forming subunit Kir6.2 and the sulfonylurea binding subunit SUR1 in isolated mouse islets and clonal pancreatic MIN6 beta cells, we used four complementary techniques: immunoelectron microscopy, density gradient fractionation, vesicle immunopurification and fluorescence-activated vesicle isolation. Intravesicular and mitochondrial concentrations of free Ca(2+) were measured in intact or digitonin-permeabilised MIN6 cells using recombinant, targeted aequorins, and intravesicular pH was measured with the recombinant fluorescent probe pHluorin. RESULTS SUR1 and Kir6.2 immunoreactivity were concentrated on dense-core vesicles and on vesicles plus the endoplasmic reticulum/Golgi network, respectively, in both islets and MIN6 cells. Reactivity to neither subunit was detected on mitochondria. Glibenclamide, tolbutamide and diazoxide all failed to affect Ca(2+) uptake into mitochondria, and K(ATP) channel regulators had no significant effect on intravesicular free Ca(2+) concentrations or vesicular pH. CONCLUSIONS/INTERPRETATION A significant proportion of Kir6.2 and SUR1 subunits reside on insulin-secretory vesicles and the distal secretory pathway in mouse beta cells but do not influence intravesicular ion homeostasis. We propose that dense-core vesicles may serve instead as sorting stations for the delivery of channels to the plasma membrane.
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Affiliation(s)
- A Varadi
- Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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47
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Abstract
Darier disease (DD) and Hailey-Hailey disease (HHD) are the only known autosomal-dominant Ca2+ ATPase disorders. Epidermal symptoms selectively occur in the affected individuals, the precise reason for which is still not fully understood. Here, we review the clinical, epidermal, and molecular features of the two genodermatoses. It is concluded that epidermal Ca2+ regulation disturbances and epigenetic factors may play an even more prominent role in the pathogenesis of DD and HHD than earlier appreciated.
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Affiliation(s)
- Réka Szigeti
- 1Department of Dermatology, University of Pécs, Pécs, Hungary
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48
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Dai FF, Zhang Y, Kang Y, Wang Q, Gaisano HY, Braunewell KH, Chan CB, Wheeler MB. The neuronal Ca2+ sensor protein visinin-like protein-1 is expressed in pancreatic islets and regulates insulin secretion. J Biol Chem 2006; 281:21942-21953. [PMID: 16731532 DOI: 10.1074/jbc.m512924200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Visinin-like protein-1 (VILIP-1) is a member of the neuronal Ca2+ sensor protein family that modulates Ca2+-dependent cell signaling events. VILIP-1, which is expressed primarily in the brain, increases cAMP formation in neural cells by modulating adenylyl cyclase, but its functional role in other tissues remains largely unknown. In this study, we demonstrate that VILIP-1 is expressed in murine pancreatic islets and beta-cells. To gain insight into the functions of VILIP-1 in beta-cells, we used both overexpression and small interfering RNA knockdown strategies. Overexpression of VILIP-1 in the MIN6 beta-cell line or isolated mouse islets had no effect on basal insulin secretion but significantly increased glucose-stimulated insulin secretion. cAMP accumulation was elevated in VILIP-1-overexpressing cells, and the protein kinase A inhibitor H-89 attenuated increased glucose-stimulated insulin secretion. Overexpression of VILIP-1 in isolated mouse beta-cells increased cAMP content accompanied by increased cAMP-responsive element-binding protein gene expression and enhanced exocytosis as detected by cell capacitance measurements. Conversely, VILIP-1 knockdown by small interfering RNA caused a reduction in cAMP accumulation and produced a dramatic increase in preproinsulin mRNA, basal insulin secretion, and total cellular insulin content. The increase in preproinsulin mRNA in these cells was attributed to enhanced insulin gene transcription. Taken together, we have shown that VILIP-1 is expressed in pancreatic beta-cells and modulates insulin secretion. Increased VILIP-1 enhanced insulin secretion in a cAMP-associated manner. Down-regulation of VILIP-1 was accompanied by decreased cAMP accumulation but increased insulin gene transcription.
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Affiliation(s)
- Feihan F Dai
- Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Yi Zhang
- Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Youhou Kang
- Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Qinghua Wang
- Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Herbert Y Gaisano
- Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Karl-Heinz Braunewell
- Signal Transduction Research Group, Neuroscience Research Center of the Charité, Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Catherine B Chan
- Department of Biomedical Sciences, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3, Canada
| | - Michael B Wheeler
- Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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49
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Nevins AK, Thurmond DC. Caveolin-1 functions as a novel Cdc42 guanine nucleotide dissociation inhibitor in pancreatic beta-cells. J Biol Chem 2006; 281:18961-72. [PMID: 16714282 DOI: 10.1074/jbc.m603604200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The cycling of the small Rho family GTPase Cdc42 is required for insulin granule exocytosis, although the regulatory proteins involved in Cdc42 cycling in pancreatic beta-cells are unknown. Here we demonstrate that the caveolar protein caveolin-1 (Cav-1) is a Cdc42-binding protein in beta-cells. Cav-1 associated with Cdc42-VAMP2-bound granules present near the plasma membrane under basal conditions. However, stimulation with glucose induced the dissociation of Cav-1 from Cdc42-VAMP2 complexes, coordinate with the timing of Cdc42 activation. Analyses of the Cav-1 scaffolding domain revealed a motif conserved in guanine nucleotide dissociation inhibitors (GDIs), which suggested a novel role for Cav-1 as a Cdc42 GDI in beta-cells. The novel role was further supported by: 1) in vitro binding analyses that demonstrated a direct interaction between Cav-1 and Cdc42; 2) GST-Cdc42 interaction assays showing preferential Cav-1 binding to GDP-Cdc42 over that of GTP-Cdc42; 3) Cav-1 depletion studies resulting in an inappropriate 40% induction of activated Cdc42 in the absence of stimuli and also a 40% increase in basal insulin release from both MIN6 cells and islets. Expression of wild-type Cav-1 in Cav-1-depleted cells restored basal level secretion to normal, whereas expression of a scaffolding domain mutant of Cav-1 failed to normalize secretion. Taken together, these data suggest that Cav-1 functions as a Cdc42 GDI in beta-cells, maintaining Cdc42 in an inactive state and regulating basal secretion in the absence of stimuli. Through its interaction with the Cdc42-VAMP2-bound insulin granule complex, Cav-1 may contribute to the specific targeting of granules to "active sites" of exocytosis organized by caveolae.
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Affiliation(s)
- Angela K Nevins
- Department of Biochemistry and Molecular Biology and Center for Diabetes Research, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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50
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Duman JG, Chen L, Palmer AE, Hille B. Contributions of Intracellular Compartments to Calcium Dynamics: Implicating an Acidic Store. Traffic 2006; 7:859-72. [PMID: 16787398 DOI: 10.1111/j.1600-0854.2006.00432.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many cells show a plateau of elevated cytosolic Ca(2+) after a long depolarization, suggesting delayed Ca(2+) release from intracellular compartments such as mitochondria and endoplasmic reticulum (ER). Mouse pancreatic beta-cells show a thapsigargin-sensitive plateau ('hump') of Ca(2+) after a 30 s depolarization but not after a 10 s depolarization. Surprisingly, this hump depends primarily on compartments other than the mitochondria or ER. It is reduced by only 22% upon blocking mitochondrial Na(+)-Ca(2+) exchange and by only 18% upon blocking ryanodine or IP(3) receptors together. Further, the time course of ER Ca(2+) measured by a targeted cameleon does not depend on the duration of depolarizations. Instead, the hump is reduced 35% by treatments with the dipeptide glycylphenylalanine beta-napthylamide, a tool often used to lyse lysosomes. We show that this dipeptide does not disturb ER functions, but it lyses acidic compartments and releases Ca(2+) into the cytosol. Moreover, it induces leaks in and possibly lyses insulin granules and stops mobilization of secretory granules to the readily releasable pool in beta-cells. We conclude that the dipeptide compromises dense-core secretory granules and that these granules comprise an acidic calcium store in beta-cells whose loading and/or release is sensitive to thapsigargin and which releases Ca(2+) after cytosolic Ca(2+) elevation.
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Affiliation(s)
- Joseph G Duman
- Department of Physiology and Biophysics, University of Washington, Seattle WA 98195, USA
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