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Marmugi A, Parnis J, Chen X, Carmichael L, Hardy J, Mannan N, Marchetti P, Piemonti L, Bosco D, Johnson P, Shapiro JAM, Cruciani-Guglielmacci C, Magnan C, Ibberson M, Thorens B, Valdivia HH, Rutter GA, Leclerc I. Sorcin Links Pancreatic β-Cell Lipotoxicity to ER Ca2+ Stores. Diabetes 2016; 65:1009-21. [PMID: 26822088 PMCID: PMC4806657 DOI: 10.2337/db15-1334] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 01/18/2016] [Indexed: 01/02/2023]
Abstract
Preserving β-cell function during the development of obesity and insulin resistance would limit the worldwide epidemic of type 2 diabetes. Endoplasmic reticulum (ER) calcium (Ca(2+)) depletion induced by saturated free fatty acids and cytokines causes β-cell ER stress and apoptosis, but the molecular mechanisms behind these phenomena are still poorly understood. Here, we demonstrate that palmitate-induced sorcin downregulation and subsequent increases in glucose-6-phosphatase catalytic subunit-2 (G6PC2) levels contribute to lipotoxicity. Sorcin is a calcium sensor protein involved in maintaining ER Ca(2+) by inhibiting ryanodine receptor activity and playing a role in terminating Ca(2+)-induced Ca(2+) release. G6PC2, a genome-wide association study gene associated with fasting blood glucose, is a negative regulator of glucose-stimulated insulin secretion (GSIS). High-fat feeding in mice and chronic exposure of human islets to palmitate decreases endogenous sorcin expression while levels of G6PC2 mRNA increase. Sorcin-null mice are glucose intolerant, with markedly impaired GSIS and increased expression of G6pc2 Under high-fat diet, mice overexpressing sorcin in the β-cell display improved glucose tolerance, fasting blood glucose, and GSIS, whereas G6PC2 levels are decreased and cytosolic and ER Ca(2+) are increased in transgenic islets. Sorcin may thus provide a target for intervention in type 2 diabetes.
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Affiliation(s)
- Alice Marmugi
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Julia Parnis
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Xi Chen
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI
| | - LeAnne Carmichael
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Julie Hardy
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Naila Mannan
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K
| | - Piero Marchetti
- Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy
| | - Lorenzo Piemonti
- Diabetes Research Institute (HSR-DRI), San Raffaele Scientific Institute, Milan, Italy
| | - Domenico Bosco
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
| | - Paul Johnson
- Nuffield Department of Surgical Sciences, University of Oxford, Oxford, U.K
| | - James A M Shapiro
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, Alberta, Canada
| | | | - Christophe Magnan
- Unit of Functional and Adaptive Biology, Paris Diderot University-Paris 7, Paris, France
| | - Mark Ibberson
- Vital-IT Group, SIB Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Bernard Thorens
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Héctor H Valdivia
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K.
| | - Isabelle Leclerc
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology & Metabolism, Department of Medicine, Imperial College London, London, U.K.
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Multiple roles of glucose-6-phosphatases in pathophysiology. Biochim Biophys Acta Gen Subj 2013; 1830:2608-18. [DOI: 10.1016/j.bbagen.2012.12.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 12/11/2012] [Accepted: 12/13/2012] [Indexed: 12/28/2022]
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Cole JT, Kean WS, Pollard HB, Verma A, Watson WD. Glucose-6-phosphate reduces calcium accumulation in rat brain endoplasmic reticulum. Front Mol Neurosci 2012; 5:51. [PMID: 22529775 PMCID: PMC3330244 DOI: 10.3389/fnmol.2012.00051] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 04/01/2012] [Indexed: 12/01/2022] Open
Abstract
Brain cells expend large amounts of energy sequestering calcium (Ca2+), while loss of Ca2+ compartmentalization leads to cell damage or death. Upon cell entry, glucose is converted to glucose-6-phosphate (G6P), a parent substrate to several metabolic major pathways, including glycolysis. In several tissues, G6P alters the ability of the endoplasmic reticulum (ER) to sequester Ca2+. This led to the hypothesis that G6P regulates Ca2+ accumulation by acting as an endogenous ligand for sarco-endoplasmic reticulum calcium ATPase (SERCA). Whole brain ER microsomes were pooled from adult male Sprague-Dawley rats. Using radio-isotopic assays, 45Ca2+ accumulation was quantified following incubation with increasing amounts of G6P, in the presence or absence of thapsigargin, a potent SERCA inhibitor. To qualitatively assess SERCA activity, the simultaneous release of inorganic phosphate (Pi) coupled with Ca2+ accumulation was quantified. Addition of G6P significantly and decreased Ca2+ accumulation in a dose-dependent fashion (1–10 mM). The reduction in Ca2+ accumulation was not significantly different that seen with addition of thapsigargin. Addition of glucose-1-phosphate or fructose-6-phosphate, or other glucose metabolic pathway intermediates, had no effect on Ca2+ accumulation. Further, the release of Pi was markedly decreased, indicating G6P-mediated SERCA inhibition as the responsible mechanism for reduced Ca2+ uptake. Simultaneous addition of thapsigargin and G6P did decrease inorganic phosphate in comparison to either treatment alone, which suggests that the two treatments have different mechanisms of action. Therefore, G6P may be a novel, endogenous regulator of SERCA activity. Additionally, pathological conditions observed during disease states that disrupt glucose homeostasis, may be attributable to Ca2+ dystasis caused by altered G6P regulation of SERCA activity.
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Affiliation(s)
- Jeffrey T Cole
- Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda MD, USA
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4
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de Oliveira MC, Torrezan R, da Costa CEM, Ambiel CR, Constantin RP, Ishii-Iwamoto EL, Salgueiro-Pagadigorria CL. Changes in calcium fluxes in mitochondria, microsomes, and plasma membrane vesicles of livers from monosodium L-glutamate-obese rats. Metabolism 2011; 60:1433-41. [PMID: 21489575 DOI: 10.1016/j.metabol.2011.02.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 02/09/2011] [Accepted: 02/17/2011] [Indexed: 01/11/2023]
Abstract
The purpose of this work was to evaluate if the fat liver accumulation interferes with intracellular calcium fluxes and the liver glycogenolytic response to a calcium-mobilizing α(1)-adrenergic agonist, phenylephrine. The animal model of monosodium L-glutamate (MSG)-induced obesity was used. The adult rats develop obesity and steatosis. Calcium fluxes were evaluated through measuring the (45)Ca(2+) uptake by liver microsomes, inside-out plasma membrane, and mitochondria. In the liver, assessments were performed on the calcium-dependent glycogenolytic response to phenylephrine and the glycogen contents. The Ca(2+) uptake by microsomes and plasma membrane vesicles was reduced in livers from obese rats as a result of reduction in the Ca(2+)-ATPase activities. In addition, the plasma membrane Na(+)/K(+)-ATPase was reduced. All these matched effects could contribute to elevated resting intracellular calcium levels in the hepatocytes. Livers from obese rats, albeit smaller and with similar glycogen contents to those of control rats, released higher amounts of glucose in response to phenylephrine infusion, which corroborates these observations. Mitochondria from obese rats exhibited a higher capacity of retaining calcium, a phenomenon that could be attributed to a minor susceptibility of the mitochondrial permeability transition pore opening.
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Affiliation(s)
- Monique Cristine de Oliveira
- Laboratory of Biological Oxidations, Department of Biochemistry, University of Maringá, 87020900 Maringá, Brazil
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Csala M, Marcolongo P, Lizák B, Senesi S, Margittai E, Fulceri R, Magyar JE, Benedetti A, Bánhegyi G. Transport and transporters in the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1325-41. [PMID: 17466261 DOI: 10.1016/j.bbamem.2007.03.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2006] [Revised: 03/08/2007] [Accepted: 03/15/2007] [Indexed: 12/12/2022]
Abstract
Enzyme activities localized in the luminal compartment of the endoplasmic reticulum are integrated into the cellular metabolism by transmembrane fluxes of their substrates, products and/or cofactors. Most compounds involved are bulky, polar or even charged; hence, they cannot be expected to diffuse through lipid bilayers. Accordingly, transport processes investigated so far have been found protein-mediated. The selective and often rate-limiting transport processes greatly influence the activity, kinetic features and substrate specificity of the corresponding luminal enzymes. Therefore, the phenomenological characterization of endoplasmic reticulum transport contributes largely to the understanding of the metabolic functions of this organelle. Attempts to identify the transporter proteins have only been successful in a few cases, but recent development in molecular biology promises a better progress in this field.
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Affiliation(s)
- Miklós Csala
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary
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Csala M, Staines AG, Bánhegyi G, Mandl J, Coughtrie MWH, Burchell B. Evidence for multiple glucuronide transporters in rat liver microsomes. Biochem Pharmacol 2004; 68:1353-62. [PMID: 15345325 DOI: 10.1016/j.bcp.2004.05.055] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Accepted: 05/26/2004] [Indexed: 12/01/2022]
Abstract
The transport of glucuronides across the endoplasmic reticulum membrane is an important step in the overall process of biotransformation, although the mechanism remains unclear and the participating transporters are unidentified. Using a rapid filtration assay in combination with liquid chromatography-mass spectrometry, we measured the transport of a variety of beta-D-glucuronides in rat liver microsomes and investigated the substrate specificity of the participating transporter(s) by inhibition studies. Time-dependent and bi-directional transport of phenolphthalein glucuronide was detected and the kinetic parameters for transport were determined. The K(m) and V(max) values of high affinity transport were 26microM and 3.9nmol/min/mg protein, respectively. Phenolphthalein glucuronide transport was inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid and N-ethylmaleimide. Transport inhibition studies revealed competition between three glucuronides: phenolphthalein glucuronide, estradiol 17-glucuronide and naphthol AS-BI glucuronide indicating that they share a common transporter in the endoplasmic reticulum membrane. Their transport was inhibited by phenolphthalein, but was not affected by p-nitrophenyl glucuronide, naphthyl glucuronide or d-glucuronate. Morphine 3-glucuronide transport was not inhibited by any of the latter four compounds or by phenolphthalein glucuronide. This novel experimental approach has produced data consistent with the presence of multiple (at least three) transporters catalyzing the transport of glucuronides through the endoplasmic reticulum membrane. These data also indicate that the size and/or shape of the aglycone rather than the glucuronic acid moiety per se is an important determinant of transporter specificity.
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Affiliation(s)
- Miklós Csala
- Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, Scotland.
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Sava G, Frausin F, Cocchietto M, Vita F, Podda E, Spessotto P, Furlani A, Scarcia V, Zabucchi G. Actin-dependent tumour cell adhesion after short-term exposure to the antimetastasis ruthenium complex NAMI-A. Eur J Cancer 2004; 40:1383-96. [PMID: 15177498 DOI: 10.1016/j.ejca.2004.01.034] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2003] [Revised: 09/20/2003] [Accepted: 01/16/2004] [Indexed: 11/25/2022]
Abstract
Imidazolium trans-imidazoledimethylsulphoxidetrachlororuthenate (NAMI-A) was tested in vitro on the pro-adhesive properties, evaluated as resistance to trypsin treatment, which is a bona fide measure of adhesion strength, of KB and HeLa carcinoma cell lines and on human polymorphonuclear neutrophils (HPMN). NAMI-A increased the pro-adhesive activity of KB cells at 0.001 mM concentration, after few minutes incubation and this effect was not influenced by the vehicle used for cell challenge, neither did it depend on NAMI-A concentration or on temperature. The same effect occurred on HeLa cells at 0.01 mM NAMI-A. This effect, detected at concentrations up to 100 times lower than those necessary to block cells at the G(2)-M premitotic phase of cell cycle, or to inhibit matrix metalloproteinase release or cell invasion, was not related to ruthenium uptake by tumour cells. HeLa cells and healthy HPMN, following short exposure to 0.1 mM NAMI-A, assumed a different shape, with the extrusion of filopodia (HeLa) and of large lamellopodia (HPMN), which increased their interactions with the substrate. This effect was attributed to stabilisation, altered turnover and sensitivity to cytochalasin D of actin filaments. Provided that adhesion is associated with cell motility and invasion, these data suggest that NAMI-A may exert antimetastatic properties at concentrations lower than those observed in the lungs at the end of a conventional intraperitoneal treatment in vivo.
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Affiliation(s)
- G Sava
- Department of Biomedical Sciences, University of Trieste, Via L. Giorgieri 7, 34127 Trieste, Italy.
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Salgueiro-Pagadigorria CL, Kelmer-Bracht AM, Bracht A, Ishii-Iwamoto EL. Naproxen affects Ca2+ fluxes in mitochondria, microsomes and plasma membrane vesicles. Chem Biol Interact 2004; 147:49-63. [PMID: 14726152 DOI: 10.1016/j.cbi.2003.10.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
There is substantial evidence that nonsteroidal anti-inflammatory drugs (NSAIDs) affect cellular processes regulated by Ca(2+) ions, including the metabolic responses of the liver to Ca(2+)-dependent hormones. The aim of the present study was to determine whether the effects of naproxen are mediated by a direct action on cellular Ca(2+) fluxes. The effects of naproxen on 45Ca(2+) fluxes in mitochondria, microsomes and inside-out plasma membrane vesicles were examined. Naproxen strongly impaired the mitochondrial capacity to retain 45Ca(2+) and inhibited also ATP-dependent 45Ca(2+) uptake by microsomes. Naproxen did not modify 45Ca(2+) uptake by inside-out plasma membrane vesicles, but it inhibited the hexokinase/glucose-induced Ca(2+) efflux from preloaded vesicles. Additional assays performed in isolated mitochondria revealed that naproxen causes mitochondrial uncoupling and swelling in the presence of Ca(2+) ions. These effects were prevented by EGTA, ruthenium red and cyclosporin A, indicating that naproxen acts synergistically with Ca(2+) ions by promoting the mitochondrial permeability transition. The experimental results suggest that naproxen may impair the metabolic responses to Ca(2+)-dependent hormones acting by at least two mechanisms: (1) by interfering with the supply of external Ca(2+) through a direct action on the plasma membrane Ca(2+) influx, and (2) by affecting the refilling of the agonist-sensitive internal stores, including endoplasmic reticulum and mitochondria.
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Aiello DP, Fu L, Miseta A, Bedwell DM. Intracellular glucose 1-phosphate and glucose 6-phosphate levels modulate Ca2+ homeostasis in Saccharomyces cerevisiae. J Biol Chem 2002; 277:45751-8. [PMID: 12351653 DOI: 10.1074/jbc.m208748200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The enzyme phosphoglucomutase plays a key role in cellular metabolism by virtue of its ability to interconvert Glc-1-P and Glc-6-P. It was recently shown that a yeast strain lacking the major isoform of phosphoglucomutase (pgm2Delta) accumulates a high level of Glc-1-P and exhibits several phenotypes related to altered Ca(2+) homeostasis when d-galactose is utilized as the carbon source (Fu, L., Miseta, A., Hunton, D., Marchase, R. B., and Bedwell, D. M. (2000) J. Biol. Chem. 275, 5431-5440). These phenotypes include increased Ca(2+) uptake and accumulation and sensitivity to high environmental Ca(2+) levels. In the present study, we overproduced the enzyme UDP-Glc pyrophosphorylase to test whether the overproduction of a downstream metabolite produced from Glc-1-P can also mediate changes in Ca(2+) homeostasis. We found that overproduction of UDP-Glc did not cause any alterations in Ca(2+) uptake or accumulation. We also examined whether Glc-6-P can influence cellular Ca(2+) homeostasis. A yeast strain lacking the beta-subunit of phosphofructokinase (pfk2Delta) accumulates a high level of Glc-6-P (Huang, D., Wilson, W. A., and Roach, P. J. (1997) J. Biol. Chem. 272, 22495-22501). We found that this increase in Glc-6-P led to a 1.5-2-fold increase in total cellular Ca(2+). We also found that the pgm2Delta/pfk2Delta strain, which accumulated high levels of both Glc-6-P and Glc-1-P, no longer exhibited the Ca(2+)-related phenotypes associated with high Glc-1-P levels in the pgm2Delta mutant. These results provide strong evidence that cellular Ca(2+) homeostasis is coupled to the relative levels of Glc-6-P and Glc-1-P in yeast.
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Affiliation(s)
- David P Aiello
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294-2170, USA
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10
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Abstract
Glucose-6-phosphatase (G6Pase), an enzyme found mainly in the liver and the kidneys, plays the important role of providing glucose during starvation. Unlike most phosphatases acting on water-soluble compounds, it is a membrane-bound enzyme, being associated with the endoplasmic reticulum. In 1975, W. Arion and co-workers proposed a model according to which G6Pase was thought to be a rather unspecific phosphatase, with its catalytic site oriented towards the lumen of the endoplasmic reticulum [Arion, Wallin, Lange and Ballas (1975) Mol. Cell. Biochem. 6, 75--83]. Substrate would be provided to this enzyme by a translocase that is specific for glucose 6-phosphate, thereby accounting for the specificity of the phosphatase for glucose 6-phosphate in intact microsomes. Distinct transporters would allow inorganic phosphate and glucose to leave the vesicles. At variance with this substrate-transport model, other models propose that conformational changes play an important role in the properties of G6Pase. The last 10 years have witnessed important progress in our knowledge of the glucose 6-phosphate hydrolysis system. The genes encoding G6Pase and the glucose 6-phosphate translocase have been cloned and shown to be mutated in glycogen storage disease type Ia and type Ib respectively. The gene encoding a G6Pase-related protein, expressed specifically in pancreatic islets, has also been cloned. Specific potent inhibitors of G6Pase and of the glucose 6-phosphate translocase have been synthesized or isolated from micro-organisms. These as well as other findings support the model initially proposed by Arion. Much progress has also been made with regard to the regulation of the expression of G6Pase by insulin, glucocorticoids, cAMP and glucose.
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Affiliation(s)
- Emile van Schaftingen
- Laboratoire de Chimie Physiologique, UCL and ICP, Avenue Hippocrate 75, B-1200 Brussels, Belgium.
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Lin B, Annabi B, Hiraiwa H, Pan CJ, Chou JY. Cloning and characterization of cDNAs encoding a candidate glycogen storage disease type 1b protein in rodents. J Biol Chem 1998; 273:31656-60. [PMID: 9822626 DOI: 10.1074/jbc.273.48.31656] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glycogen storage disease type 1 (GSD-1) is a group of genetic disorders caused by a deficiency in the activity of the enzyme glucose-6-phosphatase. (G6Pase). GSD-1a and GSD-1b, the two major subgroups, have been confirmed at the molecular genetic level. The gene responsible for GSD-1b maps to human chromosome 11q23 and a candidate human GSD-1b cDNA that encodes a microsomal transmembrane protein has been identified. In this study, we show that this cDNA maps to chromosome 11q23; thus it is a strong candidate for GSD-1b. Furthermore, we isolated and characterized candidate murine and rat GSD-1b cDNAs. Both encode transmembrane proteins sharing 93-95% sequence homology to the human GSD-1b protein. The expression profiles of murine GSD-1b and G6Pase differ both in the liver and in the kidney; the GSD-1b transcript appears before the G6Pase mRNA during development. In addition to G6Pase deficiency, GSD-1b patients suffer neutropenia, neutrophil dysfunction, and recurrent bacterial infections. Interestingly, although the G6Pase mRNA is expressed primarily in the liver, kidney, and intestine, the GSD-1b mRNA is expressed in numerous tissues, including human neutrophils/monocytes.
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Affiliation(s)
- B Lin
- Heritable Disorders Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA
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Hwang TL, Lau YT, Tsai MM, Liu MS. Changes of adenosine triphosphate-dependent calcium uptake in microsomal fractions of rat liver during sepsis. Surgery 1997; 121:662-7. [PMID: 9186467 DOI: 10.1016/s0039-6060(97)90055-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Intracellular calcium concentration is an important regulator of cellular metabolism. Endoplasmic reticulum membranes play an important role in the regulation of cytoplasmic calcium in the mammalian liver. The characterization of the changes of calcium uptake in endoplasmic reticulum may contribute to the potential intracellular mechanisms for cellular dysfunction during sepsis. METHODS The effects of sepsis on the calcium uptake in rough endoplasmic reticulum of rat liver were studied. Sepsis was induced by means of cecal ligation and puncture (CLP). The control rats underwent sham operation. Microsomal fractions were isolated from the liver with differential centrifugation. RESULTS The calcium uptake by liver endoplasmic reticulum was decreased by 30% to 35% (p < 0.05) during early sepsis (9 hours after CLP) and by 38% to 43% (p < 0.05) during late sepsis (18 hours after CLP), respectively. The maximum velocity values for adenosine triphosphate (ATP) and for Ca2+ were also decreased by 25% to 37% (p < 0.05) during early sepsis and by 35% to 42% (p < 0.05) during late sepsis. The Michaelis-Menten constant for ATP and Ca2+ transport had no difference among three groups. The magnesium stimulation and vanadate inhibitory activity were also decreased by 17% to 38% (p < 0.05) during early sepsis and by 34% to 50% (p < 0.05) during late sepsis. CONCLUSIONS These data demonstrate that ATP-dependent calcium uptake in rough endoplasmic reticulum of rat liver was impaired during early and late sepsis. Because the low intracellular calcium concentration plays an important role in the regulation of cellular function, an impairment in the ATP-dependent calcium uptake by endoplasmic reticulum during early and late sepsis may have a pathophysiologic significance in contributing to the development of altered hepatic metabolism during sepsis.
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Affiliation(s)
- T L Hwang
- Department of Surgery & Physiology, Chang Gung Memorial Hospital, Chang Gung Medical College, Taipei, Taiwan, R.O.C
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Darbha S, Marchase RB. Regulation of intracellular calcium is closely linked to glucose metabolism in J774 macrophages. Cell Calcium 1996; 20:361-71. [PMID: 8939356 DOI: 10.1016/s0143-4160(96)90042-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The effects of 2-deoxy-D-glucose (2dGlc) and glucose deprivation were investigated in the J774 murine macrophage-like cell line. 2dGlc addition or glucose deprivation for 4 min led to an inhibition in the transient increase in cytoplasmic free Ca2+ ([Ca2+]i) that otherwise occurs in response to three different agonists: IgG, ATP and platelet activating factor. This inhibition was preceded by a partial release of Ca2+ from intracellular, thapsigargin-sensitive stores. In contrast, the transition from 5 to 30 mM glucose caused a decrease in [Ca2+]i and a corresponding increase in thapsigargin-sensitive sequestered Ca2+. The effects of an alternate glycolytic inhibitor, NaF, and a mitochondrial inhibitor, rotenone, were also tested. These inhibitors caused neither a release of Ca2+ from intracellular stores nor an inhibition in any of the agonist responses. The capacitative influx of extracellular Ca2+ following depletion of intracellular stores was also found to be selectively inhibited by the prior addition of 2dGlc or with glucose deprivation. In addition, when an elevated plateau of [Ca2+]i was established by the irreversible depletion of intracellular Ca2+ stores, the addition of 2dGlc caused a decrease in the on-going capacitative entry of Ca2+.
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Affiliation(s)
- S Darbha
- Department of Cell Biology, University of Alabama at Birmingham 35294-0005, USA
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Abstract
The major role of the liver endoplasmic reticulum phosphate/pyrophosphate transport proteins is the regulation of blood glucose levels. The glucose-6-phosphatase enzyme is an endoplasmic reticulum enzyme system which hydrolyzes glucose-6-phosphate to glucose and phosphate. Glucose-6-phosphatase is the terminal step of both gluconeogenesis and glycogenolysis. The glucose-6-phosphatase enzyme is a very hydrophobic membrane protein and its active site is inside the lumen of the endoplasmic reticulum. The substrates and products of the enzyme therefore have to cross the endoplasmic reticulum membrane. The glucose-6-phosphatase enzyme is associated with a calcium binding protein (SP). There are also transport proteins for the substrate glucose-6-phosphate (T1) and the products phosphate (T2) and glucose (T3). There appear to be at least two different liver endoplasmic reticulum proteins that can transport phosphate. One of the proteins T2b can also transport pyrophosphate and carbamyl phosphate which are also substrates for the glucose-6-phosphatase enzyme. The metabolic regulation, genetic deficiencies, ontogeny and tissue distribution of the endoplasmic reticulum T2 proteins will be described.
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Affiliation(s)
- A Burchell
- Department of Obstetrics and Gynaecology, Ninewells Hospital and Medical School, University of Dundee, Scotland, United Kingdom
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Rivera AA, White CR, Guest LL, Elton TS, Marchase RB. Hyperglycemia alters cytoplasmic Ca2+ responses to capacitative Ca2+ influx in rat aortic smooth muscle cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 269:C1482-8. [PMID: 8572177 DOI: 10.1152/ajpcell.1995.269.6.c1482] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Concentrations of free cytoplasmic Ca2+ in rat aortic smooth muscle (RASM) cells were monitored using the ratiometric Ca2+ indicator fura 2-acetoxymethyl ester (AM). In RASM cells cultured in 5 mM Glc, incubation with angiotensin II, ATP, or thapsigargin [a selective inhibitor of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase] depleted SR Ca2+ stores and initiated a capacitative Ca2+ influx through the plasma membrane. This influx was resistant to verapamil, a selective inhibitor of L-type voltage-gated Ca2+ channels, but was sensitive to SKF-96365, an inhibitor of the receptor-operated Ca2+ entry pathway. RASM cells cultured in 25 mM Glc exhibited a significant decrease in cytoplasmic Ca2+ responses to agonist-induced Ca2+ release from SR stores and to subsequent capacitative Ca2+ entry. In addition, the cytoplasmic response to thapsigargin-induced release of Ca2+ from the SR in hyperglycemic cells peaked more sharply than in control cells and returned to baseline more rapidly. The effects of hyperglycemia were not overcome by myo-inositol supplementation.
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Affiliation(s)
- A A Rivera
- Department of Cell Biology, University of Alabama at Birmingham 35294-0005, USA
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16
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Loret SM, Devos PE. Corrective note about R* cells of the digestive gland of the shore crab Carcinus maenas. Cell Tissue Res 1995. [DOI: 10.1007/bf00307813] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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17
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Fulceri R, Gamberucci A, Scott HM, Giunti R, Burchell A, Benedetti A. Fatty acyl-CoA esters inhibit glucose-6-phosphatase in rat liver microsomes. Biochem J 1995; 307 ( Pt 2):391-7. [PMID: 7733874 PMCID: PMC1136661 DOI: 10.1042/bj3070391] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In native rat liver microsomes glucose 6-phosphatase activity is dependent not only on the activity of the glucose-6-phosphatase enzyme (which is lumenal) but also on the transport of glucose-6-phosphate, phosphate and glucose through the respective translocases T1, T2 and T3. By using enzymic assay techniques, palmitoyl-CoA or CoA was found to inhibit glucose-6-phosphatase activity in intact microsomes. The effect of CoA required ATP and fatty acids to form fatty acyl esters. Increasing concentrations (2-50 microM) of CoA (plus ATP and 20 microM added palmitic acid) or of palmitoyl-CoA progressively decreased glucose-6-phosphatase activity to 50% of the control value. The inhibition lowered the Vmax without significantly changing the Km. A non-hydrolysable analogue of palmitoyl-CoA also inhibited, demonstrating that binding of palmitoyl-CoA rather than hydrolysis produces the inhibition. Light-scattering measurements of osmotically induced changes in the size of rat liver microsomal vesicles pre-equilibrated in a low-osmolality buffer demonstrated that palmitoyl-CoA alone or CoA plus ATP and palmitic acid altered the microsomal permeability to glucose 6-phosphate, but not to glucose or phosphate, indicating that T1 is the site of palmitoyl-CoA binding and inhibition of glucose-6-phosphatase activity in native microsomes. The type of inhibition found suggests that liver microsomes may comprise vesicles heterogeneous with respect to glucose-6-phosphate translocase(s), i.e. sensitive or insensitive to fatty acid ester inhibition.
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Affiliation(s)
- R Fulceri
- Istituto di Patologia Generale, University of Siena, Italy
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18
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Dey NB, Bounelis P, Fritz TA, Bedwell DM, Marchase RB. The glycosylation of phosphoglucomutase is modulated by carbon source and heat shock in Saccharomyces cerevisiae. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)47136-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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19
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Bygrave FL, Benedetti A. Calcium: its modulation in liver by cross-talk between the actions of glucagon and calcium-mobilizing agonists. Biochem J 1993; 296 ( Pt 1):1-14. [PMID: 8250828 PMCID: PMC1137647 DOI: 10.1042/bj2960001] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- F L Bygrave
- Division of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra, ACT
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20
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Fulceri R, Gamberucci A, Bellomo G, Giunti R, Benedetti A. CoA and fatty acyl-CoA derivatives mobilize calcium from a liver reticular pool. Biochem J 1993; 295 ( Pt 3):663-9. [PMID: 8240274 PMCID: PMC1134610 DOI: 10.1042/bj2950663] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The effect of CoA and fatty acyl-CoA esters on Ca2+ fluxes has been studied in isolated liver microsomes and in digitonin-permeabilized hepatocytes. When microsomes were loaded with increasing concentrations of Ca2+ (6-29 nmol/mg of protein), the extent to which CoA and palmitoyl-CoA released Ca2+ increased. At 23 nmol of Ca2+/mg of protein, half-maximal [CoA] and [palmitoyl-CoA] were 35 and 50 microM respectively. Under conditions of minimal Ca2+ loading, net release of Ca2+ was absent, but Ca2+ translocation from a CoA-sensitive to a CoA-insensitive pool took place. The effect of CoA required the presence of fatty acids, probably to form fatty acyl esters. In permeabilized hepatocytes, the pool(s) mobilized by CoA (or by palmitoyl-CoA) appeared to be different from that mobilized by Ins(1,4,5)P3.
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Affiliation(s)
- R Fulceri
- Instituto di Patologia Generale, University of Siena, Italy
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21
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Fulceri R, Bellomo G, Gamberucci A, Romani A, Benedetti A. Physiological concentrations of inorganic phosphate affect MgATP-dependent Ca2+ storage and inositol trisphosphate-induced Ca2+ efflux in microsomal vesicles from non-hepatic cells. Biochem J 1993; 289 ( Pt 1):299-306. [PMID: 8424767 PMCID: PMC1132164 DOI: 10.1042/bj2890299] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
1. MgATP-dependent 45Ca2+ uptake by microsomes obtained from various non-hepatic tissues, namely rat brain, rat solid Morris hepatoma 3924A and human platelets, was measured in the presence of P(i) at low, cytosol-like, concentrations. 2. Increasing P(i) concentrations (0.5-3 mM) caused a progressive enlargement of the 45Ca(2+)-storage capacity of all the microsomal fractions. 3. As a result of P(i) stimulation of Ca2+ uptake, 45Ca2+ and [32P]P(i) were co-accumulated by the three microsomal fractions. 4. The time course for 45Ca2+ and [32P]P(i) accumulation in brain microsomes revealed a biphasic 45Ca2+ uptake: a rapid phase was followed by a second, slower, phase, which depended on the presence of P(i). During the P(i)-dependent phase, the uptake of 45Ca2+ was paralleled by the uptake of [32P]Pi. 5. The passive efflux of Ca2+ was paralleled by the efflux of P(i) and vice versa. In fact, the inhibition of active Ca2+ uptake by excess EGTA, or lowering the P(i) concentration of the incubation system by dilution, caused the release of 45Ca2+ and [32P]P(i) from 45Ca2+ or [32P]P(i) pre-loaded brain microsomes. The Ca2+ ionophore A23187 also released 45Ca2+ and [32P]P(i). 6. Ca2+ efflux by A23187 was rapid (t 1/2 approx. 2 s) and independent of the extent of intravesicular Ca2+ loading, which indicates that Ca2+ and P(i) do not form intravesicular insoluble complexes. 7. The progressive increase in Ca2+ accumulation, depending on P(i) stimulation, resulted in a proportional increase in the amount of Ca2+ releasable by InsP3 in the three non-hepatic microsomal fractions and in digitonin-permeabilized platelets. 8. Concomitantly to Ca2+, microsomal P(i) was also released by InsP3.
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Affiliation(s)
- R Fulceri
- Istituto di Patologia Generale, University of Siena, Italy
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22
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Loret SM, Devos PE. Hydrolysis of G6P by a microsomal aspecific phosphatase and glucose phosphorylation by a low K m hexokinase in the digestive gland of the crab Carcinus maenas: variations during the moult cycle. J Comp Physiol B 1992. [DOI: 10.1007/bf00296647] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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23
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Fulceri R, Bellomo G, Gamberucci A, Scott HM, Burchell A, Benedetti A. Permeability of rat liver microsomal membrane to glucose 6-phosphate. Biochem J 1992; 286 ( Pt 3):813-7. [PMID: 1417741 PMCID: PMC1132976 DOI: 10.1042/bj2860813] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Light-scattering measurements of osmotically induced changes in the size of rat liver microsomal vesicles pre-equilibrated in a low-osmolality buffer revealed the following. (1) The increase in extravesicular osmolality by addition of glucose 6-phosphate or mannose 6-phosphate (25 mM each) caused a rapid shrinking of microsomal vesicles. After shrinkage, a rapid swelling phase (t1/2 approx. 22 s) was present with glucose 6-phosphate but absent with mannose 6-phosphate, indicating that the former had entered microsomal vesicles, but the latter had not. (2) Almost identical results were obtained in the absence of any glucose 6-phosphate hydrolysis, i.e. with microsomes pre-treated with 100 microM-vanadate. (3) The anion-channel blocker 4,4'-di-isothiocyanostilbene-2,2'-disulphonic acid (DIDS) suppressed the glucose 6-phosphate-induced swelling phase. (4) The swelling phase was more prolonged as the glucose 6-phosphate concentration increased (t1/2 = 16 +/- 3, 22 +/- 3 and 35 +/- 4 s with 25 mM, 37.5 mM- and 50 mM-glucose 6-phosphate respectively). The behaviour of glucose-6-phosphatase activity of intact and disrupted microsomes measured in the presence of high concentrations (less than 30 mM) of substrate also indicated the saturation of the glucose 6-phosphate permeation system by extravesicular concentrations of glucose 6-phosphate higher than 20-30 mM. Additional experiments showed that vanadate-treated microsomes pre-equilibrated with 0.1 mM- and 1.0 mM-glucose 6-phosphate (and [1-14C]glucose 6-phosphate as a tracer) rapidly (t1/2 less than 20 s) released [1-14C]glucose 6-phosphate when diluted in a glucose 6-phosphate-free medium. The efflux of [1-14C]glucose 6-phosphate was largely prevented by DIDS, allowing an evaluation of the intravesicular space of glucose 6-phosphate of approx. 1.0 microliter/mg of microsomal protein.
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Affiliation(s)
- R Fulceri
- Istituto di Patologia Generale, University of Siena, Italy
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24
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Loret SM, Devos PE. Structure and possible functions of the calcospherite-rich cells (R* cells) in the digestive gland of the shore crab Carcinus maenas. Cell Tissue Res 1992; 267:105-11. [PMID: 1310440 DOI: 10.1007/bf00318696] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
R*-cells of the digestive gland of Carcinus maenas have been investigated functionally and morphologically. A comparison of the capacity of separated cell suspensions to synthesize glycogen gave support to the hypothesis that R and R* cells belong to the same cell line. The unexpected observation of R* cells in gastric juice suggests that their release could represent a mode of redistribution of carbohydrate stores when the feeding activity of the crab is lower. Under electron microscopy, the calcospherites of R* cells appeared to be surrounded by multiple membranous layers, and displayed tubular and vesicular structures in their core. High glucose-6-phosphatase (G6Pase) activity in the subcellular fraction that is enriched in calcospherites suggests that these membranes are derived from the endoplasmic reticulum, via a process in which the enzyme plays a key role. We propose that this is the way by which the R cell differentiates into R* cell.
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Affiliation(s)
- S M Loret
- Département de Biologie, Facultés Universitaires Notre-Dame de la Paix, Namur, Belgium
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25
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Bànhegyi G, Fulceri R, Bellomo G, Romani A, Pompella A, Benedetti A. Role of a nonmitochondrial Ca2+ pool in the synergistic stimulation by cyclic AMP and vasopressin of Ca2+ uptake in isolated rat hepatocytes. Arch Biochem Biophys 1991; 287:320-8. [PMID: 1654813 DOI: 10.1016/0003-9861(91)90485-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The subcellular distribution of 45Ca2+ accumulated by isolated rat hepatocytes exposed to dibutyryl cyclic AMP (dbcAMP) followed by vasopressin (Vp) was studied by means of a nondisruptive technique. When treated with dbcAMP followed by vasopressin, hepatocytes obtained from fed rats accumulated an amount of Ca2+ approximately fivefold higher than that attained under control conditions. Ca2+ released from the mitochondrial compartment by the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) accounted for only a minor portion of the accumulated Ca2+. The largest portion was released by the Ca2+ ionophore A23187 and was attributable to a nonmitochondrial compartment. DbcAMP + Vp-treatment also caused a maximal stimulation of glucose production and a twofold increase in cellular glucose 6-phosphate levels. In hepatocytes obtained from fasted rats, dbcAMP + Vp-stimulated Ca2+ accumulation was lower, although with the same subcellular distribution, and was associated with a minimal glucose production. In the presence of gluconeogenetic substrates (lactate plus pyruvate) hepatocytes from fasted rats were comparable to cells isolated from fed animals. However, Ca2+ accumulation and glucose 6-phosphate production could be dissociated in the absence of dbcAMP, in the presence of lactate/pyruvate alone. Under this condition in fact Vp induced only a minimal accumulation of Ca2+ in hepatocytes isolated from fasted rats, although glucose production was markedly increased. Moreover, treatment of fed rat hepatocytes with 1 mM ATP caused a maximal activation of glycogenolysis, but only a moderate stimulation of cellular Ca2+ accumulation. In this case, sequestration of Ca2+ occurred mainly in the mitochondrial compartment. By contrast, the addition of ATP to dbcAMP-pretreated hepatocytes induced a large accumulation of Ca2+ in a nonmitochondrial pool. Additional experiments using the fluorescent Ca2+ indicator Fura-2 showed that dbcAMP pretreatment can enlarge and prolong the elevation of cytosolic free Ca2+ caused by Vp. A nonmitochondrial Ca2+ pool thus appears mainly responsible for the Ca2+ accumulation stimulated by dbcAMP and Vp in isolated hepatocytes, and cyclic AMP seems able to activate Ca2+ uptake in such a nonmitochondrial pool.
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Affiliation(s)
- G Bànhegyi
- Istituto di Patologia Generale, Università di Siena, Italy
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26
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Fulceri R, Bellomo G, Gamberucci A, Benedetti A. Liver glucose-6-phosphatase activity is not modulated by physiological intracellular Ca2+ concentrations. Biochem J 1991; 275 ( Pt 3):805-7. [PMID: 1645522 PMCID: PMC1150127 DOI: 10.1042/bj2750805] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
1. In the presence of MgATP and increasing amounts of added Ca2+, isolated liver microsomal vesicles accumulate approx. 10 nmol of Ca2+/mg of protein and buffer ambient free Ca2+ at increasing concentrations (0.22-10.9 microM). Under these experimental conditions, microsomal glucose-6-phosphatase activity is unaffected by the concentration of extravesicular free Ca2+. 2. Different levels of intravesicular Ca2+ were obtained by treating microsomes with the Ca2+ ionophore A23187 and by stimulating active microsomal Ca2+ accumulation with Pi (3 mM). In both instances, microsomal glucose-6-phosphatase activity is unaffected by the level of intravesicular Ca2+.
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Affiliation(s)
- R Fulceri
- Istituto di Patologia Generale, University of Siena, Italy
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27
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Missiaen L, Wuytack F, Raeymaekers L, De Smedt H, Droogmans G, Declerck I, Casteels R. Ca2+ extrusion across plasma membrane and Ca2+ uptake by intracellular stores. Pharmacol Ther 1991; 50:191-232. [PMID: 1662401 DOI: 10.1016/0163-7258(91)90014-d] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The aim of this review is to summarize the various systems that remove Ca2+ from the cytoplasm. We will initially focus on the Ca2+ pump and the Na(+)-Ca2+ exchanger of the plasma membrane. We will review the functional regulation of these systems and the recent progress obtained with molecular-biology techniques, which pointed to the existence of different isoforms of the Ca2+ pump. The Ca2+ pumps of the sarco(endo)plasmic reticulum will be discussed next, by summarizing the discoveries obtained with molecular-biology techniques, and by reviewing the physiological regulation of these proteins. We will finally briefly review the mitochondrial Ca(2+)-uptake mechanism.
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Affiliation(s)
- L Missiaen
- Laboratory of Molecular Signalling, Department of Zoology, Cambridge, U.K
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28
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Fulceri R, Bellomo G, Gamberucci A, Benedetti A. MgATP-dependent accumulation of calcium ions and inorganic phosphate in a liver reticular pool. Biochem J 1990; 272:549-52. [PMID: 2268284 PMCID: PMC1149738 DOI: 10.1042/bj2720549] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
1. MgATP-dependent Ca2+ uptake by rat liver microsomal preparations and permeabilized hepatocytes was measured in the presence or absence of Pi. 2. Monitoring of free Ca2+ in incubation systems with a Ca2+ electrode in the presence of Pi (2-7 mM) revealed a biphasic Ca2+ uptake, with the onset of a second, Pi-dependent, Ca2+ accumulation. 3. Increasing Pi concentrations (up to 10 mM) caused a progressive enlargement of 45Ca2(+)-loading capacity of microsomal fractions. 4. As a result of Pi stimulation of active Ca2+ uptake, [32P]Pi and 45Ca2+ were co-accumulated. 5. Experiments with permeabilized hepatocytes revealed that the amount of Ca2+ releasable by myo-inositol 1,4,5-trisphosphate is unaffected by Pi.
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Affiliation(s)
- R Fulceri
- Istituto di Patologia Generale, University of Siena, Italy
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29
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Fulceri R, Romani A, Pompella A, Benedetti A. Glucose 6-phosphate stimulation of MgATP-dependent Ca2+ uptake by rat kidney microsomes. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1022:129-33. [PMID: 2302399 DOI: 10.1016/0005-2736(90)90409-h] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
(1) The features of MgATP-dependent Ca2+ accumulation under stimulation with glucose 6-phosphate were studied in rat kidney microsomes. (2) Ca2+ accumulated in the presence of MgATP alone does not exceed approx. 2 nmol/mg protein. (3) Glucose 6-phosphate markedly stimulates Ca2+ accumulation, up to steady-state levels approx. 15-fold higher than in its absence. (4) The hydrolysis of glucose 6-phosphate by glucose-6-phosphatase is essential for the stimulation, as shown by inhibiting the glucose 6-phosphate hydrolysis with adequate concentrations of vanadate. Inorganic phosphate is accumulated in microsomal vesicles during glucose 6-phosphate-stimulated Ca2+ uptake in equimolar amounts with respects to Ca2+. (5) Increasing concentrations of glucose 6-phosphate result in increasing stimulations of Ca2+ uptake, until a maximal Ca2(+)-loading capacity of approx. 27 nmol/mg microsomal protein is reached. It is suggested that the enlargement of the kidney microsomal Ca2+ pool induced by glucose 6-phosphate (an important metabolite in kidney) might play a role in the regulation of Ca2+ homeostasis in kidney tubular cells.
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Affiliation(s)
- R Fulceri
- Istituto di Patologia Generale dell'Università di Siena, Italy
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30
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Benedetti A, Graf P, Fulceri R, Romani A, Sies H. Ca2+ mobilization by vasopressin and glucagon in perfused livers. Effect of prior intoxication with bromotrichloromethane. Biochem Pharmacol 1989; 38:1799-805. [PMID: 2735938 DOI: 10.1016/0006-2952(89)90415-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Perfused livers isolated from rats treated with BrCCl3 for up to 15 min were used as an experimental tool to investigate the role of the hepatic endoplasmic reticulum in Ca2+ mobilization elicited by vasopressin and glucagon. BrCCl3-treatment caused extensive impairment (37 to 92%) of Ca2+ pumps of isolated liver microsomes, while Ca2+ pumps of mitochondria and plasma membrane vesicles remained undamaged. In perfused livers of BrCCl3-treated rats, the efflux of Ca2+ and the concomitant stimulation of O2 consumption and glucose release induced by vasopressin were decreased. The extent of the decrease paralleled the duration of BrCCl3-treatment. The decrease of Ca2+ efflux following vasopressin addition was closely correlated with the decrease of active Ca2+ accumulation by isolated microsomes (r = 0.99, P less than 0.001). The Ca2+ efflux elicited by glucagon was also decreased after BrCCl3-treatment, whereas stimulation of O2 consumption and glucose release were retained. The possibility that BrCCl3-treatment might impair the production of the intracellular Ca2+-mobilizing messenger IP3 is unlikely, since vasopressin still induced the formation of inositol phosphates, including IP3, in isolated hepatocytes obtained from BrCCl3-treated rats. Thus, this work supports the hypothesis that the Ca2+ stored in the liver ER is the major pool of intracellular Ca2+ available for mobilization by vasopressin, glucagon and other effectors.
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Affiliation(s)
- A Benedetti
- Institute of General Pathology, University of Siena, Italy
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31
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Hill A, Waddell ID, Hopwood D, Burchell A. The microsomal glucose-6-phosphatase enzyme of human gall-bladder. J Pathol 1989; 158:53-6. [PMID: 2547044 DOI: 10.1002/path.1711580111] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Microsomes isolated from adult human gall-bladders have for the first time been shown to contain specific glucose-6-phosphatase activity. The gall-bladder glucose-6-phosphatase enzyme has the same molecular weight (36,500 daltons) and similar immunological properties and kinetic characteristics to the hepatic microsomal glucose-6-phosphatase enzyme.
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Affiliation(s)
- A Hill
- Department of Medicine, Ninewells Hospital and Medical School, University of Dundee, U.K
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32
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van de Werve G. Liver Glucose-6-phosphatase Activity Is Modulated by Physiological Intracellular Ca2+ Concentrations. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83308-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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33
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Romani A, Fulceri R, Pompella A, Ferro M, Benedetti A. Active Ca2+ accumulation in the endoplasmic reticulum of different hepatomas: stimulation by phosphates and Ca2+-releasing effect of IP3. Ann N Y Acad Sci 1988; 551:249-52. [PMID: 3266724 DOI: 10.1111/j.1749-6632.1988.tb22343.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- A Romani
- Istituto di Patologia Generale della Università di Siena, Italy
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34
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Altin JG, Bygrave FL. Second messengers and the regulation of Ca2+ fluxes by Ca2+-mobilizing agonists in rat liver. Biol Rev Camb Philos Soc 1988; 63:551-611. [PMID: 3058220 DOI: 10.1111/j.1469-185x.1988.tb00670.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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35
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Abstract
Microsomal fractions isolated from pancreatic islet cells were shown to contain high specific glucose-6-phosphatase activity. The islet-cell glucose-6-phosphatase enzyme has the same Mr (36,500), similar immunological properties and kinetic characteristics to the hepatic microsomal glucose-6-phosphatase enzyme.
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Affiliation(s)
- I D Waddell
- Department of Medicine, Ninewells Hospital and Medical School, University of Dundee, U.K
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36
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Stio M, Vanni P, Pinzauti G. A continuous spectrophotometric assay for the enzymatic marker glucose 6-phosphatase. Anal Biochem 1988; 174:32-7. [PMID: 2851277 DOI: 10.1016/0003-2697(88)90515-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A continuous spectrophotometric assay for glucose 6-phosphatase is described. The method uses glucose dehydrogenase and mutarotase as ancillary enzymes. Glucose 6-phosphatase activity is measured by following NADH formation at 340 nm. The method is linear, at least up to 38 mU in the test which corresponds to a delta E of 0.24 min-1, when the enzyme is assayed in a microsomal fraction. We also discuss the method's suitability for subcellular fractionation. No other continuous assay for this important enzymatic marker of the endoplasmic reticulum is currently available.
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Affiliation(s)
- M Stio
- Dipartimento di Scienze Biochimiche, Università di Firenze, Italy
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37
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Romani A, Fulceri R, Pompella A, Benedetti A. MgATP-dependent, glucose 6-phosphate-stimulated liver microsomal Ca2+ accumulation: difference between rough and smooth microsomes. Arch Biochem Biophys 1988; 266:1-9. [PMID: 2972255 DOI: 10.1016/0003-9861(88)90231-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Some features of the MgATP-dependent Ca2+-accumulating capacity of rough as compared to smooth liver microsomal fraction were studied. Smooth microsomes accumulate somewhat higher amounts of Ca2+ than rough ones in the presence of MgATP. In the presence of glucose 6-phosphate, which markedly stimulates MgATP-dependent Ca2+ accumulation in both fractions, smooth microsomes exhibit a much higher Ca2+-accumulating capacity than rough ones. Possible reasons of the differences observed between the two fractions were investigated. Smooth microsomes exhibit a higher Ca2+-dependent ATPase activity, suggesting a higher Ca2+ inward transport into smooth vesicles. Also, following the inhibition of active Ca2+ transport by means of vanadate, smooth microsomes appear to release the Ca2+ previously accumulated--both in the absence (i.e., with MgATP only) and in the presence of glucose 6-phosphate--at a lower rate than rough ones. This indicates a lower passive backflux of Ca2+ accumulated in smooth vesicles. On the basis of these data, differences can be envisaged with respect to cellular Ca2+ handling by different domains of endoplasmic reticulum in the liver.
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Affiliation(s)
- A Romani
- Istituto di Patologia Generale, Università di Siena, Italy
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38
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MgATP-dependent glucose 6-phosphate-stimulated Ca2+ accumulation in liver microsomal fractions. Effects of inositol 1,4,5-trisphosphate and GTP. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)69094-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Linked oscillations of free Ca2+ and the ATP/ADP ratio in permeabilized RINm5F insulinoma cells supplemented with a glycolyzing cell-free muscle extract. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68917-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Corkey BE, Deeney JT, Glennon MC, Matschinsky FM, Prentki M. Regulation of steady-state free Ca2+ levels by the ATP/ADP ratio and orthophosphate in permeabilized RINm5F insulinoma cells. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68916-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Christ B, Jungermann K. Sub-compartmentation of the 'cytosolic' glucose 6-phosphate pool in cultured rat hepatocytes. FEBS Lett 1987; 221:375-80. [PMID: 3622776 DOI: 10.1016/0014-5793(87)80959-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
[14C]Glucose release either from endogenous 14C-prelabelled glycogen or from added 14C-labelled glucose 6-phosphate was measured in filipin-treated, permeabilized hepatocytes in 48 h culture. [14C]Glucose output from prelabelled glycogen was not altered by the addition of 5 mM glucose 6-phosphate to the incubation medium. Conversely, [14C]glucose release from 5 mM labelled glucose 6-phosphate was not influenced by different glycogen concentrations in the cells. Moreover, in the permeabilized cells the anion transport inhibitor DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) inhibited only the liberation of [14C]glucose from labelled glucose 6-phosphate but not from glycogen. It is therefore concluded that there exist at least 2 separate, mutually non-accessible glucose 6-phosphate pools in cultured rat hepatocytes, one linked to glycogenolysis and the other to gluconeogenesis.
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Benedetti A, Fulceri R, Romani A, Comporti M. Stimulatory effect of glucose 6-phosphate on the non-mitochondrial Ca2+ uptake in permeabilized hepatocytes and Ca2+ release by inositol trisphosphate. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 928:282-6. [PMID: 3032281 DOI: 10.1016/0167-4889(87)90187-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The relationships between Ca2+ transport and glucose-6-phosphatase activity, previously studied in isolated liver microsomes, were investigated in permeabilized hepatocytes in the presence of mitochondrial inhibitors. It was found that the addition of glucose 6-phosphate to the cells markedly stimulates the MgATP-dependent Ca2+ uptake. A progressive increase in the stimulation of Ca2+ uptake was seen with increasing amounts of glucose 6-phosphate up to 5 mM concentrations. Vanadate, when added in adequate concentrations (20-40 microM) to the hepatocytes inhibits both the glucose-6-phosphatase activity and the stimulation of Ca2+ uptake by glucose 6-phosphate, while not affecting the MgATP-dependent Ca2+ uptake. The addition of inositol 1,4,5-trisphosphate to permeabilized hepatocytes in which Ca2+ had been accumulated in the presence of MgATP and glucose 6-phosphate, results in a rapid release of Ca2+.
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Wolf BA, Colca JR, Comens PG, Turk J, McDaniel ML. Glucose 6-phosphate regulates Ca2+ steady state in endoplasmic reticulum of islets. A possible link in glucose-induced insulin secretion. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)66560-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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On a possible role for glucose-6-phosphatase in the regulation of liver cell cytosolic calcium concentration. Trends Biochem Sci 1986. [DOI: 10.1016/0968-0004(86)90026-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Hers H. Comment on the paper by A. Benedetti et al. Trends Biochem Sci 1986. [DOI: 10.1016/0968-0004(86)90027-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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