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Ucuncu E, Rajamani K, Wilson MSC, Medina-Cano D, Altin N, David P, Barcia G, Lefort N, Banal C, Vasilache-Dangles MT, Pitelet G, Lorino E, Rabasse N, Bieth E, Zaki MS, Topcu M, Sonmez FM, Musaev D, Stanley V, Bole-Feysot C, Nitschké P, Munnich A, Bahi-Buisson N, Fossoud C, Giuliano F, Colleaux L, Burglen L, Gleeson JG, Boddaert N, Saiardi A, Cantagrel V. MINPP1 prevents intracellular accumulation of the chelator inositol hexakisphosphate and is mutated in Pontocerebellar Hypoplasia. Nat Commun 2020; 11:6087. [PMID: 33257696 PMCID: PMC7705663 DOI: 10.1038/s41467-020-19919-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Accepted: 10/29/2020] [Indexed: 12/13/2022] Open
Abstract
Inositol polyphosphates are vital metabolic and secondary messengers, involved in diverse cellular functions. Therefore, tight regulation of inositol polyphosphate metabolism is essential for proper cell physiology. Here, we describe an early-onset neurodegenerative syndrome caused by loss-of-function mutations in the multiple inositol-polyphosphate phosphatase 1 gene (MINPP1). Patients are found to have a distinct type of Pontocerebellar Hypoplasia with typical basal ganglia involvement on neuroimaging. We find that patient-derived and genome edited MINPP1−/− induced stem cells exhibit an inefficient neuronal differentiation combined with an increased cell death. MINPP1 deficiency results in an intracellular imbalance of the inositol polyphosphate metabolism. This metabolic defect is characterized by an accumulation of highly phosphorylated inositols, mostly inositol hexakisphosphate (IP6), detected in HEK293 cells, fibroblasts, iPSCs and differentiating neurons lacking MINPP1. In mutant cells, higher IP6 level is expected to be associated with an increased chelation of intracellular cations, such as iron or calcium, resulting in decreased levels of available ions. These data suggest the involvement of IP6-mediated chelation on Pontocerebellar Hypoplasia disease pathology and thereby highlight the critical role of MINPP1 in the regulation of human brain development and homeostasis. Tight regulation of inositol polyphosphate metabolism is essential for proper cell physiology. Here, the authors describe an early-onset neurodegenerative syndrome caused by loss-of-function mutations in the MINPP1 gene, characterised by intracellular imbalance of inositol polyphosphate metabolism.
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Affiliation(s)
- Ekin Ucuncu
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Karthyayani Rajamani
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Miranda S C Wilson
- MRC Laboratory for Molecular Cell Biology, University College London, WC1E 6BT, London, UK
| | - Daniel Medina-Cano
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Nami Altin
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Pierre David
- Transgenesis Platform, Laboratoire d'Expérimentation Animale et Transgenèse (LEAT), Imagine Institute, Structure Fédérative de Recherche Necker INSERM US24/CNRS UMS3633, 75015, Paris, France
| | - Giulia Barcia
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France.,Département de Génétique Médicale, AP-HP, Hôpital Necker-Enfants Malades, F-75015, Paris, France
| | - Nathalie Lefort
- Université de Paris, iPSC Core Facility, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Céline Banal
- Université de Paris, iPSC Core Facility, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | | | - Gaële Pitelet
- Service de Neuropédiatrie, CHU Nice, 06200, Nice, France
| | - Elsa Lorino
- ESEAN, 44200 Nantes, Service de maladies chroniques de l'enfant, CHU Nantes, 44093, Nantes, France
| | - Nathalie Rabasse
- Service de pédiatrie, hôpital d'Antibes-Juan-les-Pins, 06600, Antibes-Juan-les-Pins, France
| | - Eric Bieth
- Service de Génétique Médicale, CHU Toulouse, 31059, Toulouse, France
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, 12311, Egypt
| | - Meral Topcu
- Department of Child Neurology, Faculty of Medicine, Hacettepe University, Ankara, 06100, Turkey
| | - Fatma Mujgan Sonmez
- Guven Hospital, Child Neurology Department, Ankara, Turkey.,Department of Child Neurology, Faculty of Medicine, Karadeniz Technical University, Trabzon, 61080, Turkey
| | - Damir Musaev
- Laboratory for Pediatric Brain Diseases, Rady Children's Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Valentina Stanley
- Laboratory for Pediatric Brain Diseases, Rady Children's Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Christine Bole-Feysot
- Université de Paris, Genomics Platform, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Patrick Nitschké
- Université de Paris, Bioinformatics Core Facility, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Arnold Munnich
- Université de Paris, Translational Genetics Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Nadia Bahi-Buisson
- Université de Paris, Genetics and Development of the Cerebral Cortex Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Catherine Fossoud
- Centre de Référence des Troubles des Apprentissages, Hôpitaux Pédiatriques de Nice CHU-Lenval, 06200, Nice, France
| | - Fabienne Giuliano
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Nice, 06202, Nice, France
| | - Laurence Colleaux
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Lydie Burglen
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France.,Centre de Référence des Malformations et Maladies Congénitales du Cervelet, Département de Génétique, AP-HP, Sorbonne Université, Hôpital Trousseau, 75012, Paris, France
| | - Joseph G Gleeson
- Laboratory for Pediatric Brain Diseases, Rady Children's Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Nathalie Boddaert
- Département de radiologie pédiatrique, INSERM UMR 1163 and INSERM U1000, AP-HP, Hôpital Necker-Enfants Malades, F-75015, Paris, France
| | - Adolfo Saiardi
- MRC Laboratory for Molecular Cell Biology, University College London, WC1E 6BT, London, UK.
| | - Vincent Cantagrel
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France.
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Agrawal R, Kalmady SV, Venkatasubramanian G. In SilicoModel-driven Assessment of the Effects of Brain-derived Neurotrophic Factor Deficiency on Glutamate and Gamma-Aminobutyric Acid: Implications for Understanding Schizophrenia Pathophysiology. CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE 2017; 15:115-125. [PMID: 28449558 PMCID: PMC5426484 DOI: 10.9758/cpn.2017.15.2.115] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 08/15/2016] [Accepted: 08/17/2016] [Indexed: 01/14/2023]
Abstract
Objective Deficient brain-derived neurotrophic factor (BDNF) is one of the important mechanisms underlying the neuroplasticity abnormalities in schizophrenia. Aberration in BDNF signaling pathways directly or circuitously influences neurotransmitters like glutamate and gamma-aminobutyric acid (GABA). For the first time, this study attempts to construct and simulate the BDNF-neurotransmitter network in order to assess the effects of BDNF deficiency on glutamate and GABA. Methods Using CellDesigner, we modeled BDNF interactions with calcium influx via N-methyl-D-aspartate receptor (NMDAR)- Calmodulin activation; synthesis of GABA via cell cycle regulators protein kinase B, glycogen synthase kinase and β-catenin; transportation of glutamate and GABA. Steady state stability, perturbation time-course simulation and sensitivity analysis were performed in COPASI after assigning the kinetic functions, optimizing the unknown parameters using random search and genetic algorithm. Results Study observations suggest that increased glutamate in hippocampus, similar to that seen in schizophrenia, could potentially be contributed by indirect pathway originated from BDNF. Deficient BDNF could suppress Glutamate decarboxylase 67-mediated GABA synthesis. Further, deficient BDNF corresponded to impaired transport via vesicular glutamate transporter, thereby further increasing the intracellular glutamate in GABAergic and glutamatergic cells. BDNF also altered calcium dependent neuroplasticity via NMDAR modulation. Sensitivity analysis showed that Calmodulin, cAMP response element-binding protein (CREB) and CREB regulated transcription coactivator-1 played significant role in this network. Conclusion The study presents in silicoquantitative model of biochemical network constituting the key signaling molecules implicated in schizophrenia pathogenesis. It provides mechanistic insights into putative contribution of deficient BNDF towards alterations in neurotransmitters and neuroplasticity that are consistent with current understanding of the disorder.
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Affiliation(s)
- Rimjhim Agrawal
- Translational Psychiatry Laboratory, Neurobiology Research Centre, National Institute of Mental Health and Neuro Sciences, Bangalore, India
| | - Sunil Vasu Kalmady
- Translational Psychiatry Laboratory, Neurobiology Research Centre, National Institute of Mental Health and Neuro Sciences, Bangalore, India
| | - Ganesan Venkatasubramanian
- Translational Psychiatry Laboratory, Neurobiology Research Centre, National Institute of Mental Health and Neuro Sciences, Bangalore, India
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Duong QH, Clark KD, Lapsley KG, Pegg RB. Quantification of inositol phosphates in almond meal and almond brown skins by HPLC/ESI/MS. Food Chem 2017; 229:84-92. [PMID: 28372252 DOI: 10.1016/j.foodchem.2017.02.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 01/26/2017] [Accepted: 02/07/2017] [Indexed: 10/20/2022]
Abstract
The extraction and measurement of all six forms of inositol phosphates (InsPs) in almond meal and brown skins were improved from existing methods by pH adjustment, supplementation of EDTA, and rapid analysis via anion-exchange high-performance liquid chromatography coupled with electrospray ionization mass spectrometry. The quantity of InsPs in six major almond cultivars ranged from 8 to 12μmol/g in the meal and 5 to 14μmol/g in the brown skins. InsP6 was the dominant form, but lower forms still accounted for ∼20% of the total InsPs molar concentration in a majority of the samples. InsPs contributed 32-55% of the organic phosphorus content and 20-38% of the total phosphorus content in the meal. In brown skins, these ranges were 44-77% and 30-52%, respectively. The successful application of this analytical method with almonds demonstrates its potential use for re-examination of the reported phytic acid contents in many other tree nuts, legumes, grains, and complex foods.
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Affiliation(s)
- Quynh H Duong
- Department of Food Science & Technology, College of Agricultural and Environmental Sciences, The University of Georgia, 100 Cedar Street, Athens, GA 30602, USA
| | - Kevin D Clark
- Department of Food Science & Technology, College of Agricultural and Environmental Sciences, The University of Georgia, 100 Cedar Street, Athens, GA 30602, USA
| | - Karen G Lapsley
- Almond Board of California, 1150 Ninth Street, Suite, 1500, Modesto, CA 95354, USA
| | - Ronald B Pegg
- Department of Food Science & Technology, College of Agricultural and Environmental Sciences, The University of Georgia, 100 Cedar Street, Athens, GA 30602, USA.
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Wilson MSC, Saiardi A. Importance of Radioactive Labelling to Elucidate Inositol Polyphosphate Signalling. Top Curr Chem (Cham) 2017; 375:14. [PMID: 28101851 PMCID: PMC5396384 DOI: 10.1007/s41061-016-0099-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 12/21/2016] [Indexed: 01/09/2023]
Abstract
Inositol polyphosphates, in their water-soluble or lipid-bound forms, represent a large and multifaceted family of signalling molecules. Some inositol polyphosphates are well recognised as defining important signal transduction pathways, as in the case of the calcium release factor Ins(1,4,5)P3, generated by receptor activation-induced hydrolysis of the lipid PtdIns(4,5)P2 by phospholipase C. The birth of inositol polyphosphate research would not have occurred without the use of radioactive phosphate tracers that enabled the discovery of the “PI response”. Radioactive labels, mainly of phosphorus but also carbon and hydrogen (tritium), have been instrumental in the development of this research field and the establishment of the inositol polyphosphates as one of the most important networks of regulatory molecules present in eukaryotic cells. Advancements in microscopy and mass spectrometry and the development of colorimetric assays have facilitated inositol polyphosphate research, but have not eliminated the need for radioactive experimental approaches. In fact, such experiments have become easier with the cloning of the inositol polyphosphate kinases, enabling the systematic labelling of specific positions of the inositol ring with radioactive phosphate. This approach has been valuable for elucidating their metabolic pathways and identifying specific and novel functions for inositol polyphosphates. For example, the synthesis of radiolabelled inositol pyrophosphates has allowed the discovery of a new protein post-translational modification. Therefore, radioactive tracers have played and will continue to play an important role in dissecting the many complex aspects of inositol polyphosphate physiology. In this review we aim to highlight the historical importance of radioactivity in inositol polyphosphate research, as well as its modern usage.
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Affiliation(s)
- Miranda S C Wilson
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK.
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5
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Gawri R, Shiba T, Pilliar R, Kandel R. Inorganic polyphosphates enhances nucleus pulposus tissue formation in vitro. J Orthop Res 2017; 35:41-50. [PMID: 27164002 DOI: 10.1002/jor.23288] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 05/06/2016] [Indexed: 02/04/2023]
Abstract
Disc degeneration is associated with low back pain for which currently there is no optimal therapy so there is a great need to identify new treatment approaches. Inorganic polyphosphates (polyP) are linear polymers of orthophosphate units varying in chain length and present in many cell types. As polyP has anabolic effects on chondrocytes, we hypothesized that polyP treatment would enhance matrix accumulation by nucleus pulposus (NP) cells. NP cells isolated from bovine caudal discs were grown in 3D culture under normoxic or in select experiments under hypoxic conditions, in the presence or absence of various concentrations and sizes of polyP. Gene expression was determined using RT-PCR. Matrix accumulation was quantified by measuring proteoglycan and collagen contents. DAPI fluorescence shift was used to stain for polyP in tissue. DAPI staining showed polyP present predominantly in the pericellular region of in vitro formed tissue. PolyP treatment enhanced matrix accumulation in a concentration and chain length dependant manner. NP cells exposed to polyP-22 (22 phosphate units length) showed an increase in gene expression of aggrecan, Collagen II, Sox 9, and MMP-13 which was maintained for the 14 days of culture. This suggests that polyP may enhance NP tissue formation in vitro by upregulating the expression of matrix genes. As polyP enhances proteoglycan accumulation even under hypoxic conditions, this raises the possibility that polyP may be a novel treatment to induce NP regeneration. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:41-50, 2017.
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Affiliation(s)
- Rahul Gawri
- Lunenfeld-Tanenbaum Research Institute, Mt Sinai Hospital, Toronto, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
| | - Toshikazu Shiba
- Regenetiss Inc., Kunitachi, Tokyo, Japan.,Kitasato Institute for Life Sciences, Kitasato University, Tokyo, Japan
| | - Robert Pilliar
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada.,Faculty of Dentistry, University of Toronto, Canada
| | - Rita Kandel
- Lunenfeld-Tanenbaum Research Institute, Mt Sinai Hospital, Toronto, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada.,Pathology and Laboratory Medicine, Mount Sinai Hospital, 600 University Avenue, Suite 6-500, Toronto, Ontario, Canada, M5G 1X5
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6
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Phillippy BQ, Perera IY, Donahue JL, Gillaspy GE. Certain Malvaceae Plants Have a Unique Accumulation of myo-Inositol 1,2,4,5,6-Pentakisphosphate. PLANTS (BASEL, SWITZERLAND) 2015; 4:267-83. [PMID: 27135328 PMCID: PMC4844327 DOI: 10.3390/plants4020267] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 05/19/2015] [Indexed: 01/28/2023]
Abstract
Methods used to quantify inositol phosphates in seeds lack the sensitivity and specificity necessary to accurately detect the lower concentrations of these compounds contained in the leaves of many plants. In order to measure inositol hexakisphosphate (InsP₆) and inositol pentakisphosphate (InsP₅) levels in leaves of different plants, a method was developed to concentrate and pre-purify these compounds prior to analysis. Inositol phosphates were extracted from leaves with diluted HCl and concentrated on small anion exchange columns. Reversed-phase solid phase extraction cartridges were used to remove compounds that give peaks that sometimes interfere during HPLC. The method permitted the determination of InsP₆ and InsP₅ concentrations in leaves as low as 10 µM and 2 µM, respectively. Most plants analyzed contained a high ratio of InsP₆ to InsP₅. In contrast, certain members of the Malvaceae family, such as cotton (Gossypium) and some hibiscus (Hibiscus) species, had a preponderance of InsP₅. Radiolabeling of cotton seedlings also showed increased amounts of InsP₅ relative to InsP₆. Why some Malvaceae species exhibit a reversal of the typical ratios of these inositol phosphates is an intriguing question for future research.
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Affiliation(s)
- Brian Q Phillippy
- Plant and Microbial Biology, Campus Box 7612, North Carolina State University, Raleigh, NC 27695, USA.
| | - Imara Y Perera
- Plant and Microbial Biology, Campus Box 7612, North Carolina State University, Raleigh, NC 27695, USA.
| | - Janet L Donahue
- Biochemistry, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA.
| | - Glenda E Gillaspy
- Biochemistry, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA.
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Koenig S, Moreau C, Dupont G, Scoumanne A, Erneux C. Regulation of NGF-driven neurite outgrowth by Ins(1,4,5)P3 kinase is specifically associated with the two isoenzymes Itpka and Itpkb in a model of PC12 cells. FEBS J 2015; 282:2553-69. [PMID: 25892505 DOI: 10.1111/febs.13300] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 04/10/2015] [Accepted: 04/15/2015] [Indexed: 11/26/2022]
Abstract
Four inositol phosphate kinases catalyze phosphorylation of the second messenger inositol 1,4,5-trisphosphate [Ins(1,4,5)P3 ] to inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4 ]: these enzymes comprise three isoenzymes of inositol 1,4,5-trisphosphate 3-kinase (Itpk), referred to as Itpka, Itpkb and Itpkc, and the inositol polyphosphate multikinase (IPMK). The four enzymes that act on Ins(1,4,5)P3 are all expressed in rat pheochromocytoma PC12 cells, a model that is used to study neurite outgrowth induced by nerve growth factor (NGF). We compared the effect of over-expression of the four GFP-tagged kinases on NGF-induced neurite outgrowth. Our data show that over-expression of the Itpka and Itpkb isoforms inhibits NGF-induced neurite outgrowth, but over-expression of Itpkc and IPMK does not. Surprisingly, over-expression of the N-terminal F-actin binding domain of Itpka, which lacks catalytic activity, was as effective at inhibiting neurite outgrowth as the full-length enzyme. Neurite length was also significantly decreased in cells over-expressing Itpka and Itpkb but not Itpkc or IPMK. This result did not depend on the over-expression level of any of the kinases. PC12 cells over-expressing GFP-tagged kinase-dead mutants Itpka/b have shorter neurites than GFP control cells. The decrease in neurite length was never as pronounced as observed with wild-type GFP-tagged Itpka/b. Finally, the percentage of neurite-bearing cells was increased in cells over-expressing the membranous type I Ins(1,4,5)P3 5-phosphatase. We conclude that Itpka and Itpkb inhibit neurite outgrowth through both F-actin binding and localized Ins(1,4,5)P3 3-kinase activity. Itpkc and IPMK do not influence neurite outgrowth or neurite length in this model.
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Affiliation(s)
- Sandra Koenig
- Interdisciplinary Research Institute, Université Libre de Bruxelles, Brussels, Belgium
| | - Colette Moreau
- Interdisciplinary Research Institute, Université Libre de Bruxelles, Brussels, Belgium
| | - Geneviève Dupont
- Unité de Chronobiologie Théorique, Faculté des Sciences, Université Libre de Bruxelles, Brussels, Belgium
| | - Ariane Scoumanne
- Laboratory of Functional Genetics, GIGA Signal Transduction, Université de Liège, Liège, Belgium
| | - Christophe Erneux
- Interdisciplinary Research Institute, Université Libre de Bruxelles, Brussels, Belgium
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Abstract
The polymer inorganic polyP (polyphosphate) and inositol phosphates, such as IP6 (inositol hexakisphosphate; also known as phytic acid), share many biophysical features. These similarities must be attributed to the phosphate groups present in these molecules. Given the ability of polyP to modify the excitation-emission spectra of DAPI we decided to investigate whether inositol phosphates possess the same property. We discovered that DAPI-IP6 complexes emit at approximately 550 nm when excited with light of wavelength 410-420 nm. IP5 (inositol pentakisphosphate) is also able to induce a similar shift in DAPI fluorescence. Conversely, IP3 (inositol trisphosphate) and IP4 (inositol tetrakisphosphate) are unable to shift DAPI fluorescence. We have employed this newly discovered feature of DAPI to study the enzymatic activity of the inositol polyphosphate multikinase and to monitor phytase phosphatase reactions. Finally, we used DAPI-IP6 fluorescence to determine the amount of IP6 in plant seeds. Using an IP6 standard curve this straight-forward analysis revealed that among the samples tested, borlotti beans possess the highest level of IP6 (9.4 mg/g of dry mass), whereas the Indian urad bean the lowest (3.2 mg/g of dry mass). The newly identified fluorescence properties of the DAPI-IP5 and DAPI-IP6 complexes allow the levels and enzymatic conversion of these two important messengers to be rapidly and reliably monitored.
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9
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Pisani F, Livermore T, Rose G, Chubb JR, Gaspari M, Saiardi A. Analysis of Dictyostelium discoideum inositol pyrophosphate metabolism by gel electrophoresis. PLoS One 2014; 9:e85533. [PMID: 24416420 PMCID: PMC3887064 DOI: 10.1371/journal.pone.0085533] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 11/28/2013] [Indexed: 11/28/2022] Open
Abstract
The social amoeba Dictyostelium discoideum was instrumental in the discovery and early characterization of inositol pyrophosphates, a class of molecules possessing highly-energetic pyrophosphate bonds. Inositol pyrophosphates regulate diverse biological processes and are attracting attention due to their ability to control energy metabolism and insulin signalling. However, inositol pyrophosphate research has been hampered by the lack of simple experimental procedures to study them. The recent development of polyacrylamide gel electrophoresis (PAGE) and simple staining to resolve and detect inositol pyrophosphate species has opened new investigative possibilities. This technology is now commonly applied to study in vitro enzymatic reactions. Here we employ PAGE technology to characterize the D. discoideum inositol pyrophosphate metabolism. Surprisingly, only three major bands are detectable after resolving acidic extract on PAGE. We have demonstrated that these three bands correspond to inositol hexakisphosphate (IP6 or Phytic acid) and its derivative inositol pyrophosphates, IP7 and IP8. Biochemical analyses and genetic evidence were used to establish the genuine inositol phosphate nature of these bands. We also identified IP9 in D. discoideum cells, a molecule so far detected only from in vitro biochemical reactions. Furthermore, we discovered that this amoeba possesses three different inositol pentakisphosphates (IP5) isomers, which are largely metabolised to inositol pyrophosphates. Comparison of PAGE with traditional Sax-HPLC revealed an underestimation of the cellular abundance of inositol pyrophosphates by traditional methods. In fact our study revealed much higher levels of inositol pyrophosphates in D. discoideum in the vegetative state than previously detected. A three-fold increase in IP8 was observed during development of D. discoideum a value lower that previously reported. Analysis of inositol pyrophosphate metabolism using ip6k null amoeba revealed the absence of developmentally-induced synthesis of inositol pyrophosphates, suggesting that the alternative class of enzyme responsible for pyrophosphate synthesis, PP-IP5K, doesn’t’ play a major role in the IP8 developmental increase.
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Affiliation(s)
- Francesca Pisani
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- Department of Biology, Ecology and Earth Science, University of Calabria, Rende, Italy
| | - Thomas Livermore
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Giuseppina Rose
- Department of Biology, Ecology and Earth Science, University of Calabria, Rende, Italy
| | - Jonathan Robert Chubb
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Marco Gaspari
- Laboratory of Proteomics and Mass Spectrometry, Department of Experimental and Clinical Medicine, “Magna Græcia” University of Catanzaro, Catanzaro, Italy
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- * E-mail:
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