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Whitfield H, Rodriguez RF, Shipton ML, Li AW, Riley AM, Potter BV, Hemmings AM, Brearley CA. Crystal Structure and Enzymology of Solanum tuberosum Inositol Tris/Tetrakisphosphate Kinase 1 ( StITPK1). Biochemistry 2024; 63:42-52. [PMID: 38146842 PMCID: PMC10765375 DOI: 10.1021/acs.biochem.3c00404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Revised: 11/30/2023] [Accepted: 11/30/2023] [Indexed: 12/27/2023]
Abstract
Inositol phosphates and their pyrophosphorylated derivatives are responsive to the phosphate supply and are agents of phosphate homeostasis and other aspects of physiology. It seems likely that the enzymes that interconvert these signals work against the prevailing milieu of mixed populations of competing substrates and products. The synthesis of inositol pyrophosphates is mediated in plants by two classes of ATP-grasp fold kinase: PPIP5 kinases, known as VIH, and members of the inositol tris/tetrakisphosphate kinase (ITPK) family, specifically ITPK1/2. A molecular explanation of the contribution of ITPK1/2 to inositol pyrophosphate synthesis and turnover in plants is incomplete: the absence of nucleotide in published crystal structures limits the explanation of phosphotransfer reactions, and little is known of the affinity of potential substrates and competitors for ITPK1. Herein, we describe a complex of ADP and StITPK1 at 2.26 Å resolution and use a simple fluorescence polarization approach to compare the affinity of binding of diverse inositol phosphates, inositol pyrophosphates, and analogues. By simple HPLC, we reveal the novel catalytic capability of ITPK1 for different inositol pyrophosphates and show Ins(3,4,5,6)P4 to be a potent inhibitor of the inositol pyrophosphate-synthesizing activity of ITPK1. We further describe the exquisite specificity of ITPK1 for the myo-isomer among naturally occurring inositol hexakisphosphates.
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Affiliation(s)
- Hayley
L. Whitfield
- School
of Biological Sciences, University of East
Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
| | - Raquel Faba Rodriguez
- School
of Biological Sciences, University of East
Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
- School
of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
| | - Megan L. Shipton
- Medicinal
Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K.
| | - Arthur W.H. Li
- School
of Biological Sciences, University of East
Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
- School
of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
| | - Andrew M. Riley
- Medicinal
Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K.
| | - Barry V.L. Potter
- Medicinal
Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K.
| | - Andrew M. Hemmings
- School
of Biological Sciences, University of East
Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
- School
of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
- College
of Food Science and Technology, Shanghai
Ocean University, Shanghai 201306, China
| | - Charles A. Brearley
- School
of Biological Sciences, University of East
Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
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Riemer E, Qiu D, Laha D, Harmel RK, Gaugler P, Gaugler V, Frei M, Hajirezaei MR, Laha NP, Krusenbaum L, Schneider R, Saiardi A, Fiedler D, Jessen HJ, Schaaf G, Giehl RFH. ITPK1 is an InsP 6/ADP phosphotransferase that controls phosphate signaling in Arabidopsis. MOLECULAR PLANT 2021; 14:1864-1880. [PMID: 34274522 PMCID: PMC8573591 DOI: 10.1016/j.molp.2021.07.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 06/28/2021] [Accepted: 07/13/2021] [Indexed: 05/20/2023]
Abstract
In plants, phosphate (Pi) homeostasis is regulated by the interaction of PHR transcription factors with stand-alone SPX proteins, which act as sensors for inositol pyrophosphates. In this study, we combined different methods to obtain a comprehensive picture of how inositol (pyro)phosphate metabolism is regulated by Pi and dependent on the inositol phosphate kinase ITPK1. We found that inositol pyrophosphates are more responsive to Pi than lower inositol phosphates, a response conserved across kingdoms. Using the capillary electrophoresis electrospray ionization mass spectrometry (CE-ESI-MS) we could separate different InsP7 isomers in Arabidopsis and rice, and identify 4/6-InsP7 and a PP-InsP4 isomer hitherto not reported in plants. We found that the inositol pyrophosphates 1/3-InsP7, 5-InsP7, and InsP8 increase several fold in shoots after Pi resupply and that tissue-specific accumulation of inositol pyrophosphates relies on ITPK1 activities and MRP5-dependent InsP6 compartmentalization. Notably, ITPK1 is critical for Pi-dependent 5-InsP7 and InsP8 synthesis in planta and its activity regulates Pi starvation responses in a PHR-dependent manner. Furthermore, we demonstrated that ITPK1-mediated conversion of InsP6 to 5-InsP7 requires high ATP concentrations and that Arabidopsis ITPK1 has an ADP phosphotransferase activity to dephosphorylate specifically 5-InsP7 under low ATP. Collectively, our study provides new insights into Pi-dependent changes in nutritional and energetic states with the synthesis of regulatory inositol pyrophosphates.
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Affiliation(s)
- Esther Riemer
- Department of Plant Nutrition, Institute of Crop Science and Resource Conservation, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Danye Qiu
- Department of Chemistry and Pharmacy and CIBSS-Centre for Integrative Biological Signalling Studies, Albert-Ludwigs University Freiburg, 79104 Freiburg, Germany
| | - Debabrata Laha
- Medical Research Council Laboratory for Molecular Cell Biology (MRC-LMCB), University College London, London WC1E 6BT, UK; Department of Biochemistry, Indian Institute of Science, Bengaluru, Karnataka 560 012, India
| | - Robert K Harmel
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, 13125 Berlin, Germany; Department of Chemistry, Humboldt Universität zu Berlin, 12489 Berlin, Germany
| | - Philipp Gaugler
- Department of Plant Nutrition, Institute of Crop Science and Resource Conservation, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Verena Gaugler
- Department of Plant Nutrition, Institute of Crop Science and Resource Conservation, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Michael Frei
- Institute of Agronomy and Crop Physiology, Justus-Liebig University Giessen, 35392 Giessen, Germany
| | - Mohammad-Reza Hajirezaei
- Department of Physiology & Cell Biology, Leibniz-Institute of Plant Genetics and Crop Plant Research, 06466 Gatersleben, Germany
| | - Nargis Parvin Laha
- Department of Plant Nutrition, Institute of Crop Science and Resource Conservation, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Lukas Krusenbaum
- Department of Plant Nutrition, Institute of Crop Science and Resource Conservation, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Robin Schneider
- Department of Plant Nutrition, Institute of Crop Science and Resource Conservation, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology (MRC-LMCB), University College London, London WC1E 6BT, UK
| | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, 13125 Berlin, Germany; Department of Chemistry, Humboldt Universität zu Berlin, 12489 Berlin, Germany
| | - Henning J Jessen
- Department of Chemistry and Pharmacy and CIBSS-Centre for Integrative Biological Signalling Studies, Albert-Ludwigs University Freiburg, 79104 Freiburg, Germany
| | - Gabriel Schaaf
- Department of Plant Nutrition, Institute of Crop Science and Resource Conservation, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany.
| | - Ricardo F H Giehl
- Department of Physiology & Cell Biology, Leibniz-Institute of Plant Genetics and Crop Plant Research, 06466 Gatersleben, Germany.
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An ATP-responsive metabolic cassette comprised of inositol tris/tetrakisphosphate kinase 1 (ITPK1) and inositol pentakisphosphate 2-kinase (IPK1) buffers diphosphosphoinositol phosphate levels. Biochem J 2021; 477:2621-2638. [PMID: 32706850 PMCID: PMC7115839 DOI: 10.1042/bcj20200423] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 06/29/2020] [Accepted: 07/06/2020] [Indexed: 12/27/2022]
Abstract
Inositol polyphosphates are ubiquitous molecular signals in metazoans, as are their pyrophosphorylated derivatives that bear a so-called ‘high-energy’ phosphoanhydride bond. A structural rationale is provided for the ability of Arabidopsis inositol tris/tetrakisphosphate kinase 1 to discriminate between symmetric and enantiomeric substrates in the production of diverse symmetric and asymmetric myo-inositol phosphate and diphospho-myo-inositol phosphate (inositol pyrophosphate) products. Simple tools are applied to chromatographic resolution and detection of known and novel diphosphoinositol phosphates without resort to radiolabeling approaches. It is shown that inositol tris/tetrakisphosphate kinase 1 and inositol pentakisphosphate 2-kinase comprise a reversible metabolic cassette converting Ins(3,4,5,6)P4 into 5-InsP7 and back in a nucleotide-dependent manner. Thus, inositol tris/tetrakisphosphate kinase 1 is a nexus of bioenergetics status and inositol polyphosphate/diphosphoinositol phosphate metabolism. As such, it commands a role in plants that evolution has assigned to a different class of enzyme in mammalian cells. The findings and the methods described will enable a full appraisal of the role of diphosphoinositol phosphates in plants and particularly the relative contribution of reversible inositol phosphate hydroxykinase and inositol phosphate phosphokinase activities to plant physiology.
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Sashidhar N, Harloff HJ, Potgieter L, Jung C. Gene editing of three BnITPK genes in tetraploid oilseed rape leads to significant reduction of phytic acid in seeds. PLANT BIOTECHNOLOGY JOURNAL 2020; 18:2241-2250. [PMID: 32191373 PMCID: PMC7589381 DOI: 10.1111/pbi.13380] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 02/07/2020] [Accepted: 02/28/2020] [Indexed: 05/20/2023]
Abstract
Commercialization of Brassica napus. L (oilseed rape) meal as protein diet is gaining more attention due to its well-balanced amino acid and protein contents. Phytic acid (PA) is a major source of phosphorus in plants but is considered as anti-nutritive for monogastric animals including humans due to its adverse effects on essential mineral absorption. The undigested PA causes eutrophication, which potentially threatens aquatic life. PA accounts to 2-5% in mature seeds of oilseed rape and is synthesized by complex pathways involving multiple enzymes. Breeding polyploids for recessive traits is challenging as gene functions are encoded by several paralogs. Gene redundancy often requires to knock out several gene copies to study their underlying effects. Therefore, we adopted CRISPR-Cas9 mutagenesis to knock out three functional paralogs of BnITPK. We obtained low PA mutants with an increase of free phosphorus in the canola grade spring cultivar Haydn. These mutants could mark an important milestone in rapeseed breeding with an increase in protein value and no adverse effects on oil contents.
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Affiliation(s)
- Niharika Sashidhar
- Plant Breeding InstituteChristian‐Albrechts‐University of KielKielGermany
| | - Hans J. Harloff
- Plant Breeding InstituteChristian‐Albrechts‐University of KielKielGermany
| | - Lizel Potgieter
- Environmental GenomicsBotanical InstituteChristian‐Albrechts‐University of KielKielGermany
- Environmental GenomicsMax‐Planck‐Institute for Evolutionary BiologyPlönGermany
| | - Christian Jung
- Plant Breeding InstituteChristian‐Albrechts‐University of KielKielGermany
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5
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Whitfield H, Gilmartin M, Baker K, Riley AM, Godage HY, Potter BVL, Hemmings AM, Brearley CA. A Fluorescent Probe Identifies Active Site Ligands of Inositol Pentakisphosphate 2-Kinase. J Med Chem 2018; 61:8838-8846. [PMID: 30160967 DOI: 10.1021/acs.jmedchem.8b01022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Inositol pentakisphosphate 2-kinase catalyzes the phosphorylation of the axial 2-OH of myo-inositol 1,3,4,5,6-pentakisphosphate for de novo synthesis of myo-inositol hexakisphosphate. Disruption of inositol pentakisphosphate 2-kinase profoundly influences cellular processes, from nuclear mRNA export and phosphate homeostasis in yeast and plants to establishment of left-right asymmetry in zebrafish. We elaborate an active site fluorescent probe that allows high throughput screening of Arabidopsis inositol pentakisphosphate 2-kinase. We show that the probe has a binding constant comparable to the Km values of inositol phosphate substrates of this enzyme and can be used to prospect for novel substrates and inhibitors of inositol phosphate kinases. We identify several micromolar Ki inhibitors and validate this approach by solving the crystal structure of protein in complex with purpurogallin. We additionally solve structures of protein in complexes with epimeric higher inositol phosphates. This probe may find utility in characterization of a wide family of inositol phosphate kinases.
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Affiliation(s)
- Hayley Whitfield
- School of Biological Sciences , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , U.K
| | - Megan Gilmartin
- School of Biological Sciences , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , U.K
| | - Kendall Baker
- School of Biological Sciences , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , U.K
| | - Andrew M Riley
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology , University of Oxford , Mansfield Road , Oxford OX1 3QT , U.K
| | - H Y Godage
- Medicinal Chemistry, Department of Pharmacy and Pharmacology , University of Bath , Claverton Down , Bath BA2 7AY , U.K
| | - Barry V L Potter
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology , University of Oxford , Mansfield Road , Oxford OX1 3QT , U.K.,Medicinal Chemistry, Department of Pharmacy and Pharmacology , University of Bath , Claverton Down , Bath BA2 7AY , U.K
| | - Andrew M Hemmings
- School of Biological Sciences , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , U.K
| | - Charles A Brearley
- School of Biological Sciences , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , U.K
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6
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Whitfield H, Riley AM, Diogenous S, Godage HY, Potter BVL, Brearley CA. Simple synthesis of 32P-labelled inositol hexakisphosphates for study of phosphate transformations. PLANT AND SOIL 2018; 427:149-161. [PMID: 29880988 PMCID: PMC5984642 DOI: 10.1007/s11104-017-3315-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 06/12/2017] [Indexed: 06/08/2023]
Abstract
BACKGROUND AND AIMS In many soils inositol hexakisphosphate in its various forms is as abundant as inorganic phosphate. The organismal and geochemical processes that exchange phosphate between inositol hexakisphosphate and other pools of soil phosphate are poorly defined, as are the organisms and enzymes involved. We rationalized that simple enzymic synthesis of inositol hexakisphosphate labeled with 32P would greatly enable study of transformation of soil inositol phosphates when combined with robust HPLC separations of different inositol phosphates. METHODS We employed the enzyme inositol pentakisphosphate 2-kinase, IP5 2-K, to transfer phosphate from [γ-32P]ATP to axial hydroxyl(s) of myo-, neo- and 1D-chiro-inositol phosphate substrates. RESULTS 32P-labeled inositol phosphates were separated by anion exchange HPLC with phosphate eluents. Additional HPLC methods were developed to allow facile separation of myo-, neo-, 1D-chiro- and scyllo-inositol hexakisphosphate on acid gradients. CONCLUSIONS We developed enzymic approaches that allow the synthesis of labeled myo-inositol 1,[32P]2,3,4,5,6-hexakisphosphate; neo-inositol 1,[32P]2,3,4,[32P]5,6 - hexakisphosphate and 1D-chiro-inositol [32P]1,2,3,4,5,[32P]6-hexakisphosphate. Additionally, we describe HPLC separations of all inositol hexakisphosphates yet identified in soils, using a collection of soil inositol phosphates described in the seminal historic studies of Cosgrove, Tate and coworkers. Our study will enable others to perform radiotracer experiments to analyze fluxes of phosphate to/from inositol hexakisphosphates in different soils.
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Affiliation(s)
- Hayley Whitfield
- School of Biological Sciences, University of Norwich, Norwich Research Park, Norwich, NR4 7TJ UK
| | - Andrew M. Riley
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Rd, Oxford, OX1 3QT UK
| | - Soulla Diogenous
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY UK
| | - Himali Y. Godage
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY UK
| | - Barry V. L. Potter
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Rd, Oxford, OX1 3QT UK
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY UK
| | - Charles A. Brearley
- School of Biological Sciences, University of Norwich, Norwich Research Park, Norwich, NR4 7TJ UK
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7
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Franco-Echevarría E, Sanz-Aparicio J, Brearley CA, González-Rubio JM, González B. The crystal structure of mammalian inositol 1,3,4,5,6-pentakisphosphate 2-kinase reveals a new zinc-binding site and key features for protein function. J Biol Chem 2017; 292:10534-10548. [PMID: 28450399 PMCID: PMC5481561 DOI: 10.1074/jbc.m117.780395] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 04/25/2017] [Indexed: 12/28/2022] Open
Abstract
Inositol 1,3,4,5,6-pentakisphosphate 2-kinases (IP5 2-Ks) are part of a family of enzymes in charge of synthesizing inositol hexakisphosphate (IP6) in eukaryotic cells. This protein and its product IP6 present many roles in cells, participating in mRNA export, embryonic development, and apoptosis. We reported previously that the full-length IP5 2-K from Arabidopsis thaliana is a zinc metallo-enzyme, including two separated lobes (the N- and C-lobes). We have also shown conformational changes in IP5 2-K and have identified the residues involved in substrate recognition and catalysis. However, the specific features of mammalian IP5 2-Ks remain unknown. To this end, we report here the first structure for a murine IP5 2-K in complex with ATP/IP5 or IP6. Our structural findings indicated that the general folding in N- and C-lobes is conserved with A. thaliana IP5 2-K. A helical scaffold in the C-lobe constitutes the inositol phosphate-binding site, which, along with the participation of the N-lobe, endows high specificity to this protein. However, we also noted large structural differences between the orthologues from these two eukaryotic kingdoms. These differences include a novel zinc-binding site and regions unique to the mammalian IP5 2-K, as an unexpected basic patch on the protein surface. In conclusion, our findings have uncovered distinct features of a mammalian IP5 2-K and set the stage for investigations into protein-protein or protein-RNA interactions important for IP5 2-K function and activity.
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Affiliation(s)
- Elsa Franco-Echevarría
- From the Departamento de Cristalografía y Biología Estructural, Instituto de Química-Física "Rocasolano," Consejo Superior de Investigaciones Científicas, Serrano 119, 28006 Madrid, Spain and
| | - Julia Sanz-Aparicio
- From the Departamento de Cristalografía y Biología Estructural, Instituto de Química-Física "Rocasolano," Consejo Superior de Investigaciones Científicas, Serrano 119, 28006 Madrid, Spain and
| | - Charles A Brearley
- the School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, United Kingdom
| | - Juana M González-Rubio
- From the Departamento de Cristalografía y Biología Estructural, Instituto de Química-Física "Rocasolano," Consejo Superior de Investigaciones Científicas, Serrano 119, 28006 Madrid, Spain and
| | - Beatriz González
- From the Departamento de Cristalografía y Biología Estructural, Instituto de Química-Física "Rocasolano," Consejo Superior de Investigaciones Científicas, Serrano 119, 28006 Madrid, Spain and
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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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9
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Vincent JA, Stacey M, Stacey G, Bilyeu KD. Phytic Acid and Inorganic Phosphate Composition in Soybean Lines with Independent IPK1 Mutations. THE PLANT GENOME 2015; 8:eplantgenome2014.10.0077. [PMID: 33228287 DOI: 10.3835/plantgenome2014.10.0077] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 11/20/2014] [Indexed: 06/11/2023]
Abstract
Soybean seeds contain a large amount of P, which is stored as phytic acid (PA). Phytic acid is indigestible by nonruminant livestock and considered an antinutritional factor in soybean meal. Several low PA soybean lines have been discovered, but many of these lines have either minor reductions in PA or inadequate germination and emergence. The reduced PA phenotype of soybean line Gm-lpa-ZC-2 was previously shown to be the result of a mutation in a gene encoding an inositol pentakisphosphate 2-kinase on chromosome 14 (14IPK1). While the 14IPK1 mutation was shown to have no impact on germination and emergence, the reduction in PA was modest (up to 50%). Our objective was to determine the effect on seed P partitioning for a novel mutation of an independent IPK1 gene on chromosome six (06IPK1) on its own and in combination with mutant alleles of the 14IPK1. We developed soybean populations and conducted genotype and phenotype association analyses based on the genotype of the 06IPK1 and 14IPK1 genes and the seed P partitioning profile. The lines with both mutant IPK1 genes had very low PA levels, moderate accumulation of inorganic phosphate (Pi), and accumulation of high amounts of P in lower inositols. The developed lines did not have significant reductions in germination or field emergence. In addition, characterization of the lower inositols produced in the mutant lines suggests that IPK1 is a polyphosphate kinase and provides some insight into the PA biosynthesis pathway in soybean seeds.
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Affiliation(s)
| | - Minviluz Stacey
- Division of Plant Sciences, Univ. of Missouri, Columbia, MO, 65211
| | - Gary Stacey
- Division of Plant Sciences, Univ. of Missouri, Columbia, MO, 65211
| | - Kristin D Bilyeu
- Division of Plant Sciences, Univ. of Missouri, Columbia, MO, 65211
- USDA-ARS, Plant Genetics Research Unit, Columbia, MO, 65211
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Matsuno K, Fujimura T. Induction of phytic acid synthesis by abscisic acid in suspension-cultured cells of rice. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2014; 217-218:152-157. [PMID: 24467907 DOI: 10.1016/j.plantsci.2013.12.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 12/18/2013] [Accepted: 12/25/2013] [Indexed: 06/03/2023]
Abstract
A pathway of phytic acid (PA) synthesis in plants has been revealed via investigations of low phytic acid mutants. However, the regulation of this pathway is not well understood because it is difficult to control the environments of cells in the seeds, where PA is mainly synthesized. We modified a rice suspension culture system in order to study the regulation of PA synthesis. Rice cells cultured with abscisic acid (ABA) accumulate PA at higher levels than cells cultured without ABA, and PA accumulation levels increase with ABA concentration. On the other hand, higher concentrations of sucrose or inorganic phosphorus do not affect PA accumulation. Mutations in the genes RINO1, OsMIK, OsIPK1 and OsLPA1 have each been reported to confer low phytic acid phenotypes in seeds. Each of these genes is upregulated in cells cultured with ABA. OsITPK4 and OsITPK6 are upregulated in cells cultured with ABA and in developing seeds. These results suggest that the regulation of PA synthesis is similar between developing seeds and cells in this suspension culture system. This system will be a powerful tool for elucidating the regulation of PA synthesis.
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Affiliation(s)
- Koya Matsuno
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan.
| | - Tatsuhito Fujimura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
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11
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Gillaspy GE. The Role of Phosphoinositides and Inositol Phosphates in Plant Cell Signaling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 991:141-57. [DOI: 10.1007/978-94-007-6331-9_8] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Synthesis of inositol phosphate ligands of plant hormone-receptor complexes: pathways of inositol hexakisphosphate turnover. Biochem J 2012; 444:601-9. [PMID: 22429240 DOI: 10.1042/bj20111811] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Reduction of phytate is a major goal of plant breeding programs to improve the nutritional quality of crops. Remarkably, except for the storage organs of crops such as barley, maize and soybean, we know little of the stereoisomeric composition of inositol phosphates in plant tissues. To investigate the metabolic origins of higher inositol phosphates in photosynthetic tissues, we have radiolabelled leaf tissue of Solanum tuberosum with myo-[2-3H]inositol, undertaken a detailed analysis of inositol phosphate stereoisomerism and permeabilized mesophyll protoplasts in media containing inositol phosphates. We describe the inositol phosphate composition of leaf tissue and identify pathways of inositol phosphate metabolism that we reveal to be common to other kingdoms. Our results identify the metabolic origins of a number of higher inositol phosphates including ones that are precursors of cofactors, or cofactors of plant hormone-receptor complexes. The present study affords alternative explanations of the effects of disruption of inositol phosphate metabolism reported in other species, and identifies different inositol phosphates from that described in photosynthetic tissue of the monocot Spirodela polyrhiza. We define the pathways of inositol hexakisphosphate turnover and shed light on the occurrence of a number of inositol phosphates identified in animals, for which metabolic origins have not been defined.
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Baños-Sanz JI, Sanz-Aparicio J, Whitfield H, Hamilton C, Brearley CA, González B. Conformational changes in inositol 1,3,4,5,6-pentakisphosphate 2-kinase upon substrate binding: role of N-terminal lobe and enantiomeric substrate preference. J Biol Chem 2012; 287:29237-49. [PMID: 22745128 DOI: 10.1074/jbc.m112.363671] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inositol 1,3,4,5,6-pentakisphosphate 2-kinase (IP(5) 2-K) catalyzes the synthesis of inositol 1,2,3,4,5,6-hexakisphosphate from ATP and IP(5). Inositol 1,2,3,4,5,6-hexakisphosphate is implicated in crucial processes such as mRNA export, DNA editing, and phosphorus storage in plants. We previously solved the first structure of an IP(5) 2-K, which shed light on aspects of substrate recognition. However, failure of IP(5) 2-K to crystallize in the absence of inositide prompted us to study putative conformational changes upon substrate binding. We have made mutations to residues on a region of the protein that produces a clasp over the active site. A W129A mutant allowed us to capture IP(5) 2-K in its different conformations by crystallography. Thus, the IP(5) 2-K apo-form structure displays an open conformation, whereas the nucleotide-bound form shows a half-closed conformation, in contrast to the inositide-bound form obtained previously in a closed conformation. Both nucleotide and inositide binding produce large conformational changes that can be understood as two rigid domain movements, although local changes were also observed. Changes in intrinsic fluorescence upon nucleotide and inositide binding are in agreement with the crystallographic findings. Our work suggests that the clasp might be involved in enzyme kinetics, with the N-terminal lobe being essential for inositide binding and subsequent conformational changes. We also show how IP(5) 2-K discriminates between inositol 1,3,4,5-tetrakisphosphate and 3,4,5,6-tetrakisphosphate enantiomers and that substrate preference can be manipulated by Arg(130) mutation. Altogether, these results provide a framework for rational design of specific inhibitors with potential applications as biological tools for in vivo studies, which could assist in the identification of novel roles for IP(5) 2-K in mammals.
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Affiliation(s)
- José Ignacio Baños-Sanz
- Departamento de Cristalografía y Biología Estructural, Instituto de Química-Física Rocasolano, CSIC, Serrano 119, 28006-Madrid, Spain
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Inositol 1,3,4,5,6-pentakisphosphate 2-kinase is a distant IPK member with a singular inositide binding site for axial 2-OH recognition. Proc Natl Acad Sci U S A 2010; 107:9608-13. [PMID: 20453199 DOI: 10.1073/pnas.0912979107] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Inositol phosphates (InsPs) are signaling molecules with multiple roles in cells. In particular (InsP(6)) is involved in mRNA export and editing or chromatin remodeling among other events. InsP(6) accumulates as mixed salts (phytate) in storage tissues of plants and plays a key role in their physiology. Human diets that are exclusively grain-based provide an excess of InsP(6) that, through chelation of metal ions, may have a detrimental effect on human health. Ins(1,3,4,5,6)P(5) 2-kinase (InsP(5) 2-kinase or Ipk1) catalyses the synthesis of InsP(6) from InsP(5) and ATP, and is the only enzyme that transfers a phosphate group to the axial 2-OH of the myo-inositide. We present the first structure for an InsP(5) 2-kinase in complex with both substrates and products. This enzyme presents a singular structural region for inositide binding that encompasses almost half of the protein. The key residues in substrate binding are identified, with Asp368 being responsible for recognition of the axial 2-OH. This study sheds light on the unique molecular mechanism for the synthesis of the precursor of inositol pyrophosphates.
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