1
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Ghosh S, Sanchez AM, Schwer B, Prucker I, Jork N, Jessen HJ, Shuman S. Activities and genetic interactions of fission yeast Aps1, a Nudix-type inositol pyrophosphatase and inorganic polyphosphatase. mBio 2024; 15:e0108424. [PMID: 38940614 PMCID: PMC11323792 DOI: 10.1128/mbio.01084-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Accepted: 05/28/2024] [Indexed: 06/29/2024] Open
Abstract
Inositol pyrophosphate 1,5-IP8 regulates expression of a fission yeast phosphate homeostasis regulon, comprising phosphate acquisition genes pho1, pho84, and tgp1, via its action as an agonist of precocious termination of transcription of the upstream lncRNAs that repress PHO mRNA synthesis. 1,5-IP8 levels are dictated by a balance between the Asp1 N-terminal kinase domain that converts 5-IP7 to 1,5-IP8 and three inositol pyrophosphatases-the Asp1 C-terminal domain (a histidine acid phosphatase), Siw14 (a cysteinyl-phosphatase), and Aps1 (a Nudix enzyme). In this study, we report the biochemical and genetic characterization of Aps1 and an analysis of the effects of Asp1, Siw14, and Aps1 mutations on cellular inositol pyrophosphate levels. We find that Aps1's substrate repertoire embraces inorganic polyphosphates, 5-IP7, 1-IP7, and 1,5-IP8. Aps1 displays a ~twofold preference for hydrolysis of 1-IP7 versus 5-IP7 and aps1∆ cells have twofold higher levels of 1-IP7 vis-à-vis wild-type cells. While neither Aps1 nor Siw14 is essential for growth, an aps1∆ siw14∆ double mutation is lethal on YES medium. This lethality is a manifestation of IP8 toxicosis, whereby excessive 1,5-IP8 drives derepression of tgp1, leading to Tgp1-mediated uptake of glycerophosphocholine. We were able to recover an aps1∆ siw14∆ mutant on ePMGT medium lacking glycerophosphocholine and to suppress the severe growth defect of aps1∆ siw14∆ on YES by deleting tgp1. However, the severe growth defect of an aps1∆ asp1-H397A strain could not be alleviated by deleting tgp1, suggesting that 1,5-IP8 levels in this double-pyrophosphatase mutant exceed a threshold beyond which overzealous termination affects other genes, which results in cytotoxicity. IMPORTANCE Repression of the fission yeast PHO genes tgp1, pho1, and pho84 by lncRNA-mediated interference is sensitive to changes in the metabolism of 1,5-IP8, a signaling molecule that acts as an agonist of precocious lncRNA termination. 1,5-IP8 is formed by phosphorylation of 5-IP7 and catabolized by inositol pyrophosphatases from three distinct enzyme families: Asp1 (a histidine acid phosphatase), Siw14 (a cysteinyl phosphatase), and Aps1 (a Nudix hydrolase). This study entails a biochemical characterization of Aps1 and an analysis of how Asp1, Siw14, and Aps1 mutations impact growth and inositol pyrophosphate pools in vivo. Aps1 catalyzes hydrolysis of inorganic polyphosphates, 5-IP7, 1-IP7, and 1,5-IP8 in vitro, with a ~twofold preference for 1-IP7 over 5-IP7. aps1∆ cells have twofold higher levels of 1-IP7 than wild-type cells. An aps1∆ siw14∆ double mutation is lethal because excessive 1,5-IP8 triggers derepression of tgp1, leading to toxic uptake of glycerophosphocholine.
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Affiliation(s)
- Shreya Ghosh
- Molecular Biology Program, Sloan Kettering Institute, New York, New York, USA
| | - Ana M. Sanchez
- Molecular Biology Program, Sloan Kettering Institute, New York, New York, USA
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, New York, USA
| | - Beate Schwer
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA
| | - Isabel Prucker
- Institute of Organic Chemistry, University of Freiburg, Freiburg, Germany
| | - Nikolaus Jork
- Institute of Organic Chemistry, University of Freiburg, Freiburg, Germany
| | - Henning J. Jessen
- Institute of Organic Chemistry, University of Freiburg, Freiburg, Germany
- CIBSS - Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Stewart Shuman
- Molecular Biology Program, Sloan Kettering Institute, New York, New York, USA
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2
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Zong G, Desfougères Y, Portela-Torres P, Kwon YU, Saiardi A, Shears SB, Wang H. Biochemical and structural characterization of an inositol pyrophosphate kinase from a giant virus. EMBO J 2024; 43:462-480. [PMID: 38216735 PMCID: PMC10897400 DOI: 10.1038/s44318-023-00005-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 11/11/2023] [Accepted: 11/15/2023] [Indexed: 01/14/2024] Open
Abstract
Kinases that synthesize inositol phosphates (IPs) and pyrophosphates (PP-IPs) control numerous biological processes in eukaryotic cells. Herein, we extend this cellular signaling repertoire to viruses. We have biochemically and structurally characterized a minimalist inositol phosphate kinase (i.e., TvIPK) encoded by Terrestrivirus, a nucleocytoplasmic large ("giant") DNA virus (NCLDV). We show that TvIPK can synthesize inositol pyrophosphates from a range of scyllo- and myo-IPs, both in vitro and when expressed in yeast cells. We present multiple crystal structures of enzyme/substrate/nucleotide complexes with individual resolutions from 1.95 to 2.6 Å. We find a heart-shaped ligand binding pocket comprising an array of positively charged and flexible side chains, underlying the observed substrate diversity. A crucial arginine residue in a conserved "G-loop" orients the γ-phosphate of ATP to allow substrate pyrophosphorylation. We highlight additional conserved catalytic and architectural features in TvIPK, and support their importance through site-directed mutagenesis. We propose that NCLDV inositol phosphate kinases may have assisted evolution of inositol pyrophosphate signaling, and we discuss the potential biogeochemical significance of TvIPK in soil niches.
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Affiliation(s)
- Guangning Zong
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA
| | - Yann Desfougères
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Paloma Portela-Torres
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Yong-Uk Kwon
- Department of Chemistry and Nanoscience, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, South Korea
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK.
| | - Stephen B Shears
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA.
| | - Huanchen Wang
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA.
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3
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Gu C, Li X, Zong G, Wang H, Shears SB. IP8: A quantitatively minor inositol pyrophosphate signaling molecule that punches above its weight. Adv Biol Regul 2024; 91:101002. [PMID: 38064879 DOI: 10.1016/j.jbior.2023.101002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 11/27/2023] [Indexed: 02/25/2024]
Abstract
The inositol pyrophosphates (PP-IPs) are specialized members of the wider inositol phosphate signaling family that possess functionally significant diphosphate groups. The PP-IPs exhibit remarkable functionally versatility throughout the eukaryotic kingdoms. However, a quantitatively minor PP-IP - 1,5 bisdiphosphoinositol tetrakisphosphate (1,5-IP8) - has received considerably less attention from the cell signalling community. The main purpose of this review is to summarize recently-published data which have now brought 1,5-IP8 into the spotlight, by expanding insight into the molecular mechanisms by which this polyphosphate regulates many fundamental biological processes.
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Affiliation(s)
- Chunfang Gu
- Inositol signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709 USA
| | - Xingyao Li
- Inositol signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709 USA
| | - Guangning Zong
- Inositol signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709 USA
| | - Huanchen Wang
- Inositol signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709 USA.
| | - Stephen B Shears
- Inositol signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709 USA.
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4
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Hostachy S, Wang H, Zong G, Franke K, Riley AM, Schmieder P, Potter BVL, Shears SB, Fiedler D. Fluorination Influences the Bioisostery of Myo-Inositol Pyrophosphate Analogs. Chemistry 2023; 29:e202302426. [PMID: 37773020 PMCID: PMC7615343 DOI: 10.1002/chem.202302426] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 09/14/2023] [Accepted: 09/28/2023] [Indexed: 09/30/2023]
Abstract
Inositol pyrophosphates (PP-IPs) are densely phosphorylated messenger molecules involved in numerous biological processes. PP-IPs contain one or two pyrophosphate group(s) attached to a phosphorylated myo-inositol ring. 5PP-IP5 is the most abundant PP-IP in human cells. To investigate the function and regulation by PP-IPs in biological contexts, metabolically stable analogs have been developed. Here, we report the synthesis of a new fluorinated phosphoramidite reagent and its application for the synthesis of a difluoromethylene bisphosphonate analog of 5PP-IP5 . Subsequently, the properties of all currently reported analogs were benchmarked using a number of biophysical and biochemical methods, including co-crystallization, ITC, kinase activity assays and chromatography. Together, the results showcase how small structural alterations of the analogs can have notable effects on their properties in a biochemical setting and will guide in the choice of the most suitable analog(s) for future investigations.
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Affiliation(s)
- Sarah Hostachy
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)Robert-Rössle-Straße 1013125BerlinGermany
| | - Huanchen Wang
- Inositol Signaling GroupNational Institutes of HealthResearch Triangle ParkNorth Carolina27709USA
| | - Guangning Zong
- Inositol Signaling GroupNational Institutes of HealthResearch Triangle ParkNorth Carolina27709USA
| | - Katy Franke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)Robert-Rössle-Straße 1013125BerlinGermany
| | - Andrew M. Riley
- Medicinal Chemistry & Drug Discovery Department of PharmacologyUniversity of OxfordOxfordOX1 3QTUK
| | - Peter Schmieder
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)Robert-Rössle-Straße 1013125BerlinGermany
| | - Barry V. L. Potter
- Medicinal Chemistry & Drug Discovery Department of PharmacologyUniversity of OxfordOxfordOX1 3QTUK
| | - Stephen B. Shears
- Inositol Signaling GroupNational Institutes of HealthResearch Triangle ParkNorth Carolina27709USA
| | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)Robert-Rössle-Straße 1013125BerlinGermany
- Institut für ChemieHumboldt-Universität zu BerlinBrook-Taylor-Str. 212489BerlinGermany
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5
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Sanchez AM, Schwer B, Jork N, Jessen HJ, Shuman S. Activities, substrate specificity, and genetic interactions of fission yeast Siw14, a cysteinyl-phosphatase-type inositol pyrophosphatase. mBio 2023; 14:e0205623. [PMID: 37772819 PMCID: PMC10653929 DOI: 10.1128/mbio.02056-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Accepted: 08/09/2023] [Indexed: 09/30/2023] Open
Abstract
IMPORTANCE The inositol pyrophosphate signaling molecule 1,5-IP8 modulates fission yeast phosphate homeostasis via its action as an agonist of RNA 3'-processing and transcription termination. Cellular 1,5-IP8 levels are determined by a balance between the activities of the inositol polyphosphate kinase Asp1 and several inositol pyrophosphatase enzymes. Here, we characterize Schizosaccharomyces pombe Siw14 (SpSiw14) as a cysteinyl-phosphatase-family pyrophosphatase enzyme capable of hydrolyzing the phosphoanhydride substrates inorganic pyrophosphate, inorganic polyphosphate, and inositol pyrophosphates 5-IP7, 1-IP7, and 1,5-IP8. Genetic analyses implicate SpSiw14 in 1,5-IP8 catabolism in vivo, insofar as: loss of SpSiw14 activity is lethal in the absence of the Nudix-type inositol pyrophosphatase enzyme Aps1; and siw14∆ aps1∆ lethality depends on synthesis of 1,5-IP8 by the Asp1 kinase. Suppression of siw14∆ aps1∆ lethality by loss-of-function mutations of 3'-processing/termination factors points to precocious transcription termination as the cause of 1,5-IP8 toxicosis.
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Affiliation(s)
- Ana M. Sanchez
- Molecular Biology Program, Sloan Kettering Institute, New York, New York, USA
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, New York, USA
| | - Beate Schwer
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA
| | - Nikolaus Jork
- Institute of Organic Chemistry and Centre for Integrative Biological Signaling Studies, University of Freiburg, Freiburg, Germany
- Spemann Graduate School of Biology and Medicine, University of Freiburg, Freiburg, Germany
| | - Henning J. Jessen
- Institute of Organic Chemistry and Centre for Integrative Biological Signaling Studies, University of Freiburg, Freiburg, Germany
| | - Stewart Shuman
- Molecular Biology Program, Sloan Kettering Institute, New York, New York, USA
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6
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Aguirre T, Dornan GL, Hostachy S, Neuenschwander M, Seyffarth C, Haucke V, Schütz A, von Kries JP, Fiedler D. An unconventional gatekeeper mutation sensitizes inositol hexakisphosphate kinases to an allosteric inhibitor. eLife 2023; 12:RP88982. [PMID: 37843983 PMCID: PMC10578927 DOI: 10.7554/elife.88982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2023] Open
Abstract
Inositol hexakisphosphate kinases (IP6Ks) are emerging as relevant pharmacological targets because a multitude of disease-related phenotypes has been associated with their function. While the development of potent IP6K inhibitors is gaining momentum, a pharmacological tool to distinguish the mammalian isozymes is still lacking. Here, we implemented an analog-sensitive approach for IP6Ks and performed a high-throughput screen to identify suitable lead compounds. The most promising hit, FMP-201300, exhibited high potency and selectivity toward the unique valine gatekeeper mutants of IP6K1 and IP6K2, compared to the respective wild-type (WT) kinases. Biochemical validation experiments revealed an allosteric mechanism of action that was corroborated by hydrogen deuterium exchange mass spectrometry measurements. The latter analysis suggested that displacement of the αC helix, caused by the gatekeeper mutation, facilitates the binding of FMP-201300 to an allosteric pocket adjacent to the ATP-binding site. FMP-201300 therefore serves as a valuable springboard for the further development of compounds that can selectively target the three mammalian IP6Ks; either as analog-sensitive kinase inhibitors or as an allosteric lead compound for the WT kinases.
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Affiliation(s)
- Tim Aguirre
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)BerlinGermany
- Institut für Chemie, Humboldt-Universität zu BerlinBerlinGermany
| | - Gillian L Dornan
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)BerlinGermany
| | - Sarah Hostachy
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)BerlinGermany
| | | | - Carola Seyffarth
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)BerlinGermany
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)BerlinGermany
| | - Anja Schütz
- Max‐Delbrück‐Center for Molecular Medicine in the Helmholtz Association (MDC)BerlinGermany
| | | | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)BerlinGermany
- Institut für Chemie, Humboldt-Universität zu BerlinBerlinGermany
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7
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Chabert V, Kim GD, Qiu D, Liu G, Michaillat Mayer L, Jamsheer K M, Jessen HJ, Mayer A. Inositol pyrophosphate dynamics reveals control of the yeast phosphate starvation program through 1,5-IP 8 and the SPX domain of Pho81. eLife 2023; 12:RP87956. [PMID: 37728314 PMCID: PMC10511240 DOI: 10.7554/elife.87956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/21/2023] Open
Abstract
Eukaryotic cells control inorganic phosphate to balance its role as essential macronutrient with its negative bioenergetic impact on reactions liberating phosphate. Phosphate homeostasis depends on the conserved INPHORS signaling pathway that utilizes inositol pyrophosphates and SPX receptor domains. Since cells synthesize various inositol pyrophosphates and SPX domains bind them promiscuously, it is unclear whether a specific inositol pyrophosphate regulates SPX domains in vivo, or whether multiple inositol pyrophosphates act as a pool. In contrast to previous models, which postulated that phosphate starvation is signaled by increased production of the inositol pyrophosphate 1-IP7, we now show that the levels of all detectable inositol pyrophosphates of yeast, 1-IP7, 5-IP7, and 1,5-IP8, strongly decline upon phosphate starvation. Among these, specifically the decline of 1,5-IP8 triggers the transcriptional phosphate starvation response, the PHO pathway. 1,5-IP8 inactivates the cyclin-dependent kinase inhibitor Pho81 through its SPX domain. This stimulates the cyclin-dependent kinase Pho85-Pho80 to phosphorylate the transcription factor Pho4 and repress the PHO pathway. Combining our results with observations from other systems, we propose a unified model where 1,5-IP8 signals cytosolic phosphate abundance to SPX proteins in fungi, plants, and mammals. Its absence triggers starvation responses.
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Affiliation(s)
- Valentin Chabert
- Département d'immunobiologie, Université de LausanneEpalingesSwitzerland
| | - Geun-Don Kim
- Département d'immunobiologie, Université de LausanneEpalingesSwitzerland
| | - Danye Qiu
- Institute of Organic Chemistry, Centre for Integrative Biological Signalling Studies, University of FreiburgFreiburgGermany
| | - Guizhen Liu
- Institute of Organic Chemistry, Centre for Integrative Biological Signalling Studies, University of FreiburgFreiburgGermany
| | | | | | - Henning J Jessen
- Institute of Organic Chemistry, Centre for Integrative Biological Signalling Studies, University of FreiburgFreiburgGermany
| | - Andreas Mayer
- Département d'immunobiologie, Université de LausanneEpalingesSwitzerland
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8
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Qiu D, Gu C, Liu G, Ritter K, Eisenbeis VB, Bittner T, Gruzdev A, Seidel L, Bengsch B, Shears SB, Jessen HJ. Capillary electrophoresis mass spectrometry identifies new isomers of inositol pyrophosphates in mammalian tissues. Chem Sci 2023; 14:658-667. [PMID: 36741535 PMCID: PMC9847636 DOI: 10.1039/d2sc05147h] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 12/02/2022] [Indexed: 12/12/2022] Open
Abstract
Technical challenges have to date prevented a complete profiling of the levels of myo-inositol phosphates (InsPs) and pyrophosphates (PP-InsPs) in mammalian tissues. Here, we have deployed capillary electrophoresis mass spectrometry to identify and record the levels of InsPs and PP-InsPs in several tissues obtained from wild type mice and a newly created PPIP5K2 knockout strain. We observe that the mouse colon harbours unusually high levels of InsPs and PP-InsPs. Additionally, the PP-InsP profile is considerably more complex than previously reported for animal cells: using chemically synthesized internal stable isotope references and high-resolution mass spectra, we characterize two new PP-InsP isomers as 4/6-PP-InsP5 and 2-PP-InsP5. The latter has not previously been described in nature. The analysis of feces and the commercial mouse diet suggests that the latter is one potential source of noncanonical isomers in the colon. However, we also identify both molecules in the heart, indicating unknown synthesis pathways in mammals. We also demonstrate that the CE-MS method is sensitive enough to measure PP-InsPs from patient samples such as colon biopsies and peripheral blood mononuclear cells (PBMCs). Strikingly, PBMCs also contain 4/6-PP-InsP5 and 2-PP-InsP5. In summary, our study substantially expands PP-InsP biology in mammals.
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Affiliation(s)
- Danye Qiu
- Institute of Organic Chemistry, Faculty of Chemistry and Pharmacy, University of Freiburg79104FreiburgGermany,CIBSS – Centre for Integrative Biological Signaling Studies, University of FreiburgGermany
| | - Chunfang Gu
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of HealthResearch Triangle ParkNC27709USA
| | - Guizhen Liu
- Institute of Organic Chemistry, Faculty of Chemistry and Pharmacy, University of Freiburg79104FreiburgGermany
| | - Kevin Ritter
- Institute of Organic Chemistry, Faculty of Chemistry and Pharmacy, University of Freiburg79104FreiburgGermany
| | - Verena B. Eisenbeis
- Institute of Organic Chemistry, Faculty of Chemistry and Pharmacy, University of Freiburg79104FreiburgGermany
| | - Tamara Bittner
- Institute of Organic Chemistry, Faculty of Chemistry and Pharmacy, University of Freiburg79104FreiburgGermany
| | - Artiom Gruzdev
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of HealthResearch Triangle ParkNC27709USA
| | - Lea Seidel
- CIBSS – Centre for Integrative Biological Signaling Studies, University of FreiburgGermany,Clinic for Internal Medicine II (Gastroenterology, Hepatology, Endocrinology and Infectious Diseases), Freiburg University Medical Center, Faculty of Medicine, University of FreiburgFreiburgGermany,SGBM – Spemann Graduate School of Biology and Medicine, University of FreiburgGermany
| | - Bertram Bengsch
- CIBSS – Centre for Integrative Biological Signaling Studies, University of FreiburgGermany,Clinic for Internal Medicine II (Gastroenterology, Hepatology, Endocrinology and Infectious Diseases), Freiburg University Medical Center, Faculty of Medicine, University of FreiburgFreiburgGermany
| | - Stephen B. Shears
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of HealthResearch Triangle ParkNC27709USA
| | - Henning J. Jessen
- Institute of Organic Chemistry, Faculty of Chemistry and Pharmacy, University of Freiburg79104FreiburgGermany,CIBSS – Centre for Integrative Biological Signaling Studies, University of FreiburgGermany
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9
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Sahu S, Gordon J, Gu C, Sobhany M, Fiedler D, Stanley RE, Shears SB. Nucleolar Architecture Is Modulated by a Small Molecule, the Inositol Pyrophosphate 5-InsP 7. Biomolecules 2023; 13:biom13010153. [PMID: 36671538 PMCID: PMC9855682 DOI: 10.3390/biom13010153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 12/28/2022] [Accepted: 01/09/2023] [Indexed: 01/14/2023] Open
Abstract
Inositol pyrophosphates (PP-InsPs); are a functionally diverse family of eukaryotic molecules that deploy a highly-specialized array of phosphate groups as a combinatorial cell-signaling code. One reductive strategy to derive a molecular-level understanding of the many actions of PP-InsPs is to individually characterize the proteins that bind them. Here, we describe an alternate approach that seeks a single, collective rationalization for PP-InsP binding to an entire group of proteins, i.e., the multiple nucleolar proteins previously reported to bind 5-InsP7 (5-diphospho-inositol-1,2,3,4,6-pentakisphosphate). Quantitative confocal imaging of the outer nucleolar granular region revealed its expansion when cellular 5-InsP7 levels were elevated by either (a) reducing the 5-InsP7 metabolism by a CRISPR-based knockout (KO) of either NUDT3 or PPIP5Ks; or (b), the heterologous expression of wild-type inositol hexakisphosphate kinase, i.e., IP6K2; separate expression of a kinase-dead IP6K2 mutant did not affect granular volume. Conversely, the nucleolar granular region in PPIP5K KO cells shrank back to the wild-type volume upon attenuating 5-InsP7 synthesis using either a pan-IP6K inhibitor or the siRNA-induced knockdown of IP6K1+IP6K2. Significantly, the inner fibrillar volume of the nucleolus was unaffected by 5-InsP7. We posit that 5-InsP7 acts as an 'electrostatic glue' that binds together positively charged surfaces on separate proteins, overcoming mutual protein-protein electrostatic repulsion the latter phenomenon is a known requirement for the assembly of a non-membranous biomolecular condensate.
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Affiliation(s)
- Soumyadip Sahu
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Jacob Gordon
- Nucleolar Integrity Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
- Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Keith Peters Building, Hills Rd, Cambridge CB2 0XY, UK
- Department of Haematology, University of Cambridge School of Clinical Medicine, Jeffrey Cheah Biomedical Centre, Cambridge Biomedical Campus, Puddicombe Way, Cambridge CB2 0AW, UK
- Wellcome Trust-Medical Research Council Stem Cell Institute, Jeffrey Cheah Biomedical Centre, Cambridge Biomedical Campus, Puddicombe Way, Cambridge CB2 0AW, UK
| | - Chunfang Gu
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Mack Sobhany
- Nucleolar Integrity Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Robin E. Stanley
- Nucleolar Integrity Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Stephen B. Shears
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
- Correspondence: ; Tel.: +1-984-287-3483
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10
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Benjamin B, Goldgur Y, Jork N, Jessen HJ, Schwer B, Shuman S. Structures of Fission Yeast Inositol Pyrophosphate Kinase Asp1 in Ligand-Free, Substrate-Bound, and Product-Bound States. mBio 2022; 13:e0308722. [PMID: 36468882 PMCID: PMC9765450 DOI: 10.1128/mbio.03087-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 11/07/2022] [Indexed: 12/12/2022] Open
Abstract
Expression of the fission yeast Schizosaccharomyces pombe phosphate regulon is sensitive to the intracellular level of the inositol pyrophosphate signaling molecule 1,5-IP8. IP8 dynamics are determined by Asp1, a bifunctional enzyme consisting of an N-terminal kinase domain and a C-terminal pyrophosphatase domain that catalyze IP8 synthesis and catabolism, respectively. Here, we report structures of the Asp1 kinase domain, crystallized with two protomers in the asymmetric unit, one of which was complexed with ligands (ADPNP, ADP, or ATP; Mg2+ or Mn2+; IP6, 5-IP7, or 1,5-IP8) and the other which was ligand-free. The ligand-free enzyme adopts an "open" conformation that allows ingress of substrates and egress of products. ADPNP, ADP, and ATP and associated metal ions occupy a deep phospho-donor pocket in the active site. IP6 or 5-IP7 engagement above the nucleotide favors adoption of a "closed" conformation, in which surface protein segments undergo movement and a disordered-to-ordered transition to form an inositol polyphosphate-binding site. In a structure mimetic of the kinase Michaelis complex, the anionic 5-IP7 phosphates are encaged by an ensemble of nine cationic amino acids: Lys43, Arg223, Lys224, Lys260, Arg274, Arg285, Lys290, Arg293, and Lys341. Alanine mutagenesis of amino acids that contact the adenosine nucleoside of the ATP donor underscored the contributions of Asp258 interaction with the ribose 3'-OH and of Glu248 with adenine-N6. Changing Glu248 to Gln elicited a gain of function whereby the kinase became adept at using GTP as phosphate donor. Wild-type Asp1 kinase can utilize N6-benzyl-ATP as phosphate donor. IMPORTANCE The inositol pyrophosphate signaling molecule 1,5-IP8 modulates fission yeast phosphate homeostasis via its action as an agonist of RNA 3'-processing and transcription termination. Cellular IP8 levels are determined by Asp1, a bifunctional enzyme composed of an N-terminal kinase and a C-terminal pyrophosphatase domain. Here, we present a series of crystal structures of the Asp1 kinase domain, in a ligand-free state and in complexes with nucleotides ADPNP, ADP, and ATP, divalent cations magnesium and manganese, and inositol polyphosphates IP6, 5-IP7, and 1,5-IP8. Substrate binding elicits a switch from open to closed conformations, entailing a disordered-to-ordered transition and a rearrangement or movement of two peptide segments that form a binding site for the phospho-acceptor. Our structures, along with structure-guided mutagenesis, fortify understanding of the mechanism and substrate specificity of Asp1 kinase, and they extend and complement structural and functional studies of the orthologous human kinase PPIP5K2.
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Affiliation(s)
- Bradley Benjamin
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York, USA
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, New York, USA
| | - Yehuda Goldgur
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Nikolaus Jork
- Institute of Organic Chemistry, University of Freiburg, Freiburg, Germany
| | - Henning J. Jessen
- Institute of Organic Chemistry, University of Freiburg, Freiburg, Germany
| | - Beate Schwer
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA
| | - Stewart Shuman
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York, USA
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11
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Nguyen Trung M, Furkert D, Fiedler D. Versatile signaling mechanisms of inositol pyrophosphates. Curr Opin Chem Biol 2022; 70:102177. [PMID: 35780751 DOI: 10.1016/j.cbpa.2022.102177] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 05/25/2022] [Accepted: 05/27/2022] [Indexed: 01/03/2023]
Abstract
Inositol pyrophosphates (PP-InsPs) constitute a group of highly charged messengers, which regulate central biological processes in health and disease, such as cellular phosphate and general energy homeostasis. Deciphering the molecular mechanisms underlying PP-InsP-mediated signaling remains a challenge due to the unique properties of these molecules, the different modes of action they can access, and a somewhat limited chemical and analytical toolset. Herein, we summarize the most recent mechanistic insights into PP-InsP signaling, which illustrate our progress in connecting mechanism and function of PP-InsPs.
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Affiliation(s)
- Minh Nguyen Trung
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Straße 10, 13125 Berlin, Germany; Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - David Furkert
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Straße 10, 13125 Berlin, Germany; Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Straße 10, 13125 Berlin, Germany; Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany.
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12
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Activities and Structure-Function Analysis of Fission Yeast Inositol Pyrophosphate (IPP) Kinase-Pyrophosphatase Asp1 and Its Impact on Regulation of pho1 Gene Expression. mBio 2022; 13:e0103422. [PMID: 35536002 PMCID: PMC9239264 DOI: 10.1128/mbio.01034-22] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Inositol pyrophosphates (IPPs) are signaling molecules that regulate cellular phosphate homeostasis in diverse eukaryal taxa. In fission yeast, mutations that increase 1,5-IP8 derepress the PHO regulon while mutations that ablate IP8 synthesis are PHO hyper-repressive. Fission yeast Asp1, the principal agent of 1,5-IP8 dynamics, is a bifunctional enzyme composed of an N-terminal IPP kinase domain and a C-terminal IPP pyrophosphatase domain. Here we conducted a biochemical characterization and mutational analysis of the autonomous Asp1 kinase domain (aa 1-385). Reaction of Asp1 kinase with IP6 and ATP resulted in both IP6 phosphorylation to 1-IP7 and hydrolysis of the ATP γ-phosphate, with near-equal partitioning between productive 1-IP7 synthesis and unproductive ATP hydrolysis under optimal kinase conditions. By contrast, reaction of Asp1 kinase with 5-IP7 is 22-fold faster than with IP6 and is strongly biased in favor of IP8 synthesis versus ATP hydrolysis. Alanine scanning identified essential constituents of the active site. We deployed the Ala mutants to show that derepression of pho1 expression correlated with Asp1's kinase activity. In the case of full-length Asp1, the activity of the C-terminal pyrophosphatase domain stifled net phosphorylation of the 1-position during reaction of Asp1 with ATP and either IP6 or 5-IP7. We report that inorganic phosphate is a concentration-dependent enabler of net IP8 synthesis by full-length Asp1 in vitro, by virtue of its antagonism of IP8 turnover. IMPORTANCE Expression of the fission yeast phosphate regulon is sensitive to the intracellular level of the inositol pyrophosphate (IPP) signaling molecule 1,5-IP8. IP8 dynamics are determined by Asp1, a bifunctional enzyme comprising N-terminal IPP 1-kinase and C-terminal IPP 1-pyrophosphatase domains that catalyze IP8 synthesis and catabolism, respectively. Here, we interrogated the activities and specificities of the Asp1 kinase domain and full length Asp1. We find that reaction of Asp1 kinase with 5-IP7 is 22-fold faster than with IP6 and is strongly biased in favor of IP8 synthesis versus the significant unproductive ATP hydrolysis seen during its reaction with IP6. We report that full-length Asp1 catalyzes futile cycles of 1-phosphate phosphorylation by its kinase component and 1-pyrophosphate hydrolysis by its pyrophosphatase component that result in unproductive net consumption of the ATP substrate. Net synthesis of 1,5-IP8 is enabled by physiological concentrations of inorganic phosphate that selectively antagonize IP8 turnover.
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13
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Hamila SA, Ooms LM, Rodgers SJ, Mitchell CA. The INPP4B paradox: Like PTEN, but different. Adv Biol Regul 2021; 82:100817. [PMID: 34216856 DOI: 10.1016/j.jbior.2021.100817] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 05/28/2021] [Accepted: 06/10/2021] [Indexed: 06/13/2023]
Abstract
Cancer is a complex and heterogeneous disease marked by the dysregulation of cancer driver genes historically classified as oncogenes or tumour suppressors according to their ability to promote or inhibit tumour development and growth, respectively. Certain genes display both oncogenic and tumour suppressor functions depending on the biological context, and as such have been termed dual-role cancer driver genes. However, because of their context-dependent behaviour, the tumourigenic mechanism of many dual-role genes is elusive and remains a significant knowledge gap in our effort to understand and treat cancer. Inositol polyphosphate 4-phosphatase type II (INPP4B) is an emerging dual-role cancer driver gene, primarily known for its role as a negative regulator of the phosphoinositide 3-kinase (PI3K)/AKT signalling pathway. In response to growth factor stimulation, class I PI3K generates PtdIns(3,4,5)P3 at the plasma membrane. PtdIns(3,4,5)P3 can be hydrolysed by inositol polyphosphate 5-phosphatases to generate PtdIns(3,4)P2, which, together with PtdIns(3,4,5)P3, facilitates the activation of AKT to promote cell proliferation, survival, migration, and metabolism. Phosphatase and tensin homology on chromosome 10 (PTEN) and INPP4B are dual-specificity phosphatases that hydrolyse PtdIns(3,4,5)P3 and PtdIns(3,4)P2, respectively, and thus negatively regulate PI3K/AKT signalling. PTEN is a bona fide tumour suppressor that is frequently lost in human tumours. INPP4B was initially characterised as a tumour suppressor akin to PTEN, and has been implicated as such in a number of cancers, including prostate, thyroid, and basal-like breast cancers. However, evidence has since emerged revealing INPP4B as a paradoxical oncogene in several malignancies, with increased INPP4B expression reported in AML, melanoma and colon cancers among others. Although the tumour suppressive function of INPP4B has been mostly ascribed to its ability to negatively regulate PI3K/AKT signalling, its oncogenic function remains less clear, with proposed mechanisms including promotion of PtdIns(3)P-dependent SGK3 signalling, inhibition of PTEN-dependent AKT activation, and enhancing DNA repair mechanisms to confer chemoresistance. Nevertheless, research is ongoing to identify the factors that dictate the tumourigenic output of INPP4B in different human cancers. In this review we discuss the dualistic role that INPP4B plays in the context of cancer development, progression and treatment, drawing comparisons to PTEN to explore how their similarities and, importantly, their differences may account for their diverging roles in tumourigenesis.
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Affiliation(s)
- Sabryn A Hamila
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, 3800, Australia
| | - Lisa M Ooms
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, 3800, Australia
| | - Samuel J Rodgers
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, 3800, Australia
| | - Christina A Mitchell
- Cancer Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, 3800, Australia.
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14
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PPIP5K2 promotes colorectal carcinoma pathogenesis through facilitating DNA homologous recombination repair. Oncogene 2021; 40:6680-6691. [PMID: 34645979 DOI: 10.1038/s41388-021-02052-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 08/31/2021] [Accepted: 09/29/2021] [Indexed: 12/24/2022]
Abstract
Colorectal carcinoma (CRC) is the second most deadly cancer worldwide. Therapies that take advantage of DNA repair defects have been explored in various tumors but not yet systematically in CRC. Here, we found that Diphosphoinositol Pentakisphosphate Kinase 2 (PPIP5K2), an inositol pyrophosphate kinase, was highly expressed in CRC and associated with a poor prognosis of CRC patients. In vitro and in vivo functional studies demonstrated that PPIP5K2 could promote the proliferation and migration ability of CRC cells independent of its inositol pyrophosphate kinase activity. Mechanically, S1006 dephosphorylation of PPIP5K2 could accelerate its dissociation with 14-3-3 in the cytoplasm, resulting in more nuclear distribution. Moreover, DNA damage treatments such as doxorubicin (DOX) or irradiation (IR) could induce nuclear translocation of PPIP5K2, which subsequently promoted homologous recombination (HR) repair by binding and recruiting RPA70 to the DNA damage site as a novel scaffold protein. Importantly, we verified that S1006 dephosphorylation of PPIP5K2 could significantly enhance the DNA repair ability of CRC cells through a series of DNA repair phenotype assays. In conclusion, PPIP5K2 is critical for enhancing the survival of CRC cells via facilitating DNA HR repair. Our findings revealed an unrecognized biological function and mechanism model of PPIP5K2 dependent on S1006 phosphorylation and provided a potential therapeutic target for CRC patients.
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15
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The inositol pyrophosphate metabolism of Dictyostelium discoideum does not regulate inorganic polyphosphate (polyP) synthesis. Adv Biol Regul 2021; 83:100835. [PMID: 34782304 PMCID: PMC8885430 DOI: 10.1016/j.jbior.2021.100835] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Accepted: 10/28/2021] [Indexed: 11/23/2022]
Abstract
Initial studies on the inositol phosphates metabolism were enabled by the social amoeba Dictyostelium discoideum. The abundant amount of inositol hexakisphosphate (IP6 also known as Phytic acid) present in the amoeba allowed the discovery of the more polar inositol pyrophosphates, IP7 and IP8, possessing one or two high energy phosphoanhydride bonds, respectively. Considering the contemporary growing interest in inositol pyrophosphates, it is surprising that in recent years D. discoideum, has contributed little to our understanding of their metabolism and function. This work fulfils this lacuna, by analysing the ip6k, ppip5k and ip6k-ppip5K amoeba null strains using PAGE, 13C-NMR and CE-MS analysis. Our study reveals an inositol pyrophosphate metabolism more complex than previously thought. The amoeba Ip6k synthesizes the 4/6-IP7 in contrast to the 5-IP7 isomer synthesized by the mammalian homologue. The amoeba Ppip5k synthesizes the same 1/3-IP7 as the mammalian enzyme. In D. discoideum, the ip6k strain possesses residual amounts of IP7. The residual IP7 is also present in the ip6k-ppip5K strain, while the ppip5k single mutant shows a decrease in both IP7 and IP8 levels. This phenotype is in contrast to the increase in IP7 observable in the yeast vip1Δ strain. The presence of IP8 in ppip5k and the presence of IP7 in ip6k-ppip5K indicate the existence of an additional inositol pyrophosphate synthesizing enzyme. Additionally, we investigated the existence of a metabolic relationship between inositol pyrophosphate synthesis and inorganic polyphosphate (polyP) metabolism as observed in yeast. These studies reveal that contrary to the yeast, Ip6k and Ppip5k do not control polyP cellular level in amoeba.
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16
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Couto D, Richter A, Walter H, Furkert D, Hothorn M, Fiedler D. Using Biotinylated myo-Inositol Hexakisphosphate to Investigate Inositol Pyrophosphate-Protein Interactions with Surface-Based Biosensors. Biochemistry 2021; 60:2739-2748. [PMID: 34499474 DOI: 10.1021/acs.biochem.1c00497] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Inositol pyrophosphates (PP-InsPs) are highly phosphorylated molecules that have emerged as central nutrient messengers in eukaryotic organisms. They can bind to structurally diverse target proteins to regulate biological functions, such as protein-protein interactions. PP-InsPs are strongly negatively charged and interact with highly basic surface patches in proteins, making their quantitative biochemical analysis challenging. Here, we present the synthesis of biotinylated myo-inositol hexakisphosphates and their application in surface plasmon resonance and grating-coupled interferometry assays, to enable the rapid identification, validation, and kinetic characterization of InsP- and PP-InsP-protein interactions.
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Affiliation(s)
- Daniel Couto
- Structural Plant Biology Laboratory, Department of Botany and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Annika Richter
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Straße 10, 13125 Berlin, Germany.,Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Henriette Walter
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Straße 10, 13125 Berlin, Germany.,Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - David Furkert
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Straße 10, 13125 Berlin, Germany.,Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Michael Hothorn
- Structural Plant Biology Laboratory, Department of Botany and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Straße 10, 13125 Berlin, Germany.,Institute of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
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17
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Insulin Signal Transduction Perturbations in Insulin Resistance. Int J Mol Sci 2021; 22:ijms22168590. [PMID: 34445300 PMCID: PMC8395322 DOI: 10.3390/ijms22168590] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/23/2021] [Accepted: 07/28/2021] [Indexed: 12/11/2022] Open
Abstract
Type 2 diabetes mellitus is a widespread medical condition, characterized by high blood glucose and inadequate insulin action, which leads to insulin resistance. Insulin resistance in insulin-responsive tissues precedes the onset of pancreatic β-cell dysfunction. Multiple molecular and pathophysiological mechanisms are involved in insulin resistance. Insulin resistance is a consequence of a complex combination of metabolic disorders, lipotoxicity, glucotoxicity, and inflammation. There is ample evidence linking different mechanistic approaches as the cause of insulin resistance, but no central mechanism is yet described as an underlying reason behind this condition. This review combines and interlinks the defects in the insulin signal transduction pathway of the insulin resistance state with special emphasis on the AGE-RAGE-NF-κB axis. Here, we describe important factors that play a crucial role in the pathogenesis of insulin resistance to provide directionality for the events. The interplay of inflammation and oxidative stress that leads to β-cell decline through the IAPP-RAGE induced β-cell toxicity is also addressed. Overall, by generating a comprehensive overview of the plethora of mechanisms involved in insulin resistance, we focus on the establishment of unifying mechanisms to provide new insights for the future interventions of type 2 diabetes mellitus.
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18
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Zong G, Jork N, Hostachy S, Fiedler D, Jessen HJ, Shears SB, Wang H. New structural insights reveal an expanded reaction cycle for inositol pyrophosphate hydrolysis by human DIPP1. FASEB J 2021; 35:e21275. [PMID: 33475202 DOI: 10.1096/fj.202001489r] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 10/30/2020] [Accepted: 11/30/2020] [Indexed: 11/11/2022]
Abstract
Nudix hydrolases attract considerable attention for their wide range of specialized activities in all domains of life. One particular group of Nudix phosphohydrolases (DIPPs), through their metabolism of diphosphoinositol polyphosphates (PP-InsPs), regulates the actions of these polyphosphates upon bioenergetic homeostasis. In the current study, we describe, at an atomic level, hitherto unknown properties of human DIPP1.We provide X-ray analysis of the catalytic core of DIPP1 in crystals complexed with either natural PP-InsPs, alternative PP-InsP stereoisomers, or non-hydrolysable methylene bisphosphonate analogs ("PCP-InsPs"). The conclusions that we draw from these data are interrogated by studying the impact upon catalytic activity upon mutagenesis of certain key residues. We present a picture of a V-shaped catalytic furrow with overhanging ridges constructed from flexible positively charged side chains; within this cavity, the labile phosphoanhydride bond is appropriately positioned at the catalytic site by an extensive series of interlocking polar contacts which we analogize as "suspension cables." We demonstrate functionality for a triglycine peptide within a β-strand which represents a non-canonical addition to the standard Nudix catalytic core structure. We describe pre-reaction enzyme/substrate states which we posit to reflect a role for electrostatic steering in substrate capture. Finally, through time-resolved analysis, we uncover a chronological sequence of DIPP1/product post-reaction states, one of which may rationalize a role for InsP6 as an inhibitor of catalytic activity.
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Affiliation(s)
- Guangning Zong
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Nikolaus Jork
- Institute of Organic Chemistry, CIBSS - Center for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Sarah Hostachy
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Henning J Jessen
- Institute of Organic Chemistry, CIBSS - Center for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Stephen B Shears
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Huanchen Wang
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
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19
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Laha D, Portela-Torres P, Desfougères Y, Saiardi A. Inositol phosphate kinases in the eukaryote landscape. Adv Biol Regul 2020; 79:100782. [PMID: 33422459 PMCID: PMC8024741 DOI: 10.1016/j.jbior.2020.100782] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/15/2020] [Accepted: 12/21/2020] [Indexed: 01/01/2023]
Abstract
Inositol phosphate encompasses a large multifaceted family of signalling molecules that originate from the combinatorial attachment of phosphate groups to the inositol ring. To date, four distinct inositol kinases have been identified, namely, IPK, ITPK, IPPK (IP5-2K), and PPIP5K. Although, ITPKs have recently been identified in archaea, eukaryotes have taken advantage of these enzymes to create a sophisticated signalling network based on inositol phosphates. However, it remains largely elusive what fundamental biochemical principles control the signalling cascade. Here, we present an evolutionary approach to understand the development of the 'inositol phosphate code' in eukaryotes. Distribution analyses of these four inositol kinase groups throughout the eukaryotic landscape reveal the loss of either ITPK, or of PPIP5K proteins in several species. Surprisingly, the loss of IPPK, an enzyme thought to catalyse the rate limiting step of IP6 (phytic acid) synthesis, was also recorded. Furthermore, this study highlights a noteworthy difference between animal (metazoan) and plant (archaeplastida) lineages. While metazoan appears to have a substantial amplification of IPK enzymes, archaeplastida genomes show a considerable increase in ITPK members. Differential evolution of IPK and ITPK between plant and animal lineage is likely reflective of converging functional adaptation of these two types of inositol kinases. Since, the IPK family comprises three sub-types IPMK, IP6K, and IP3-3K each with dedicated enzymatic specificity in metazoan, we propose that the amplified ITPK group in plant could be classified in sub-types with distinct enzymology.
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Affiliation(s)
- Debabrata Laha
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, WC1E6BT, London, UK
| | - Paloma Portela-Torres
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, WC1E6BT, London, UK
| | - Yann Desfougères
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, WC1E6BT, London, UK
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, WC1E6BT, London, UK.
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20
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Garg A, Shuman S, Schwer B. A genetic screen for suppressors of hyper-repression of the fission yeast PHO regulon by Pol2 CTD mutation T4A implicates inositol 1-pyrophosphates as agonists of precocious lncRNA transcription termination. Nucleic Acids Res 2020; 48:10739-10752. [PMID: 33010152 PMCID: PMC7641756 DOI: 10.1093/nar/gkaa776] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 09/03/2020] [Accepted: 09/29/2020] [Indexed: 12/23/2022] Open
Abstract
Fission yeast phosphate homeostasis genes are repressed in phosphate-rich medium by transcription of upstream lncRNAs that interferes with activation of the flanking mRNA promoters. lncRNA control of PHO gene expression is influenced by the Thr4 phospho-site in the RNA polymerase II CTD and the 3′ processing/termination factors CPF and Rhn1, mutations of which result in hyper-repression of the PHO regulon. Here, we performed a forward genetic screen for mutations that de-repress Pho1 acid phosphatase expression in CTD-T4A cells. Sequencing of 18 independent STF (Suppressor of Threonine Four) isolates revealed, in every case, a mutation in the C-terminal pyrophosphatase domain of Asp1, a bifunctional inositol pyrophosphate (IPP) kinase/pyrophosphatase that interconverts 5-IP7 and 1,5-IP8. Focused characterization of two STF strains identified 51 coding genes coordinately upregulated vis-à-vis the parental T4A strain, including all three PHO regulon genes (pho1, pho84, tgp1). Whereas these STF alleles—asp1-386(Stop) and asp1-493(Stop)—were lethal in a wild-type CTD background, they were viable in combination with mutations in CPF and Rhn1, in which context Pho1 was also de-repressed. Our findings implicate Asp1 pyrophosphatase in constraining 1,5-IP8 or 1-IP7 synthesis by Asp1 kinase, without which 1-IPPs can accumulate to toxic levels that elicit precocious termination by CPF/Rhn1.
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Affiliation(s)
- Angad Garg
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
| | - Stewart Shuman
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
| | - Beate Schwer
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY 10065, USA
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21
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Wang Z, Jork N, Bittner T, Wang H, Jessen HJ, Shears SB. Rapid stimulation of cellular Pi uptake by the inositol pyrophosphate InsP 8 induced by its photothermal release from lipid nanocarriers using a near infra-red light-emitting diode. Chem Sci 2020; 11:10265-10278. [PMID: 33659052 PMCID: PMC7891704 DOI: 10.1039/d0sc02144j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 09/07/2020] [Indexed: 11/21/2022] Open
Abstract
Inositol pyrophosphates (PP-InsPs), including diphospho-myo-inositol pentakisphosphate (5-InsP7) and bis-diphospho-myo-inositol tetrakisphosphate (1,5-InsP8), are highly polar, membrane-impermeant signaling molecules that control many homeostatic responses to metabolic and bioenergetic imbalance. To delineate their molecular activities, there is an increasing need for a toolbox of methodologies for real-time modulation of PP-InsP levels inside large populations of cultured cells. Here, we describe procedures to package PP-InsPs into thermosensitive phospholipid nanocapsules that are impregnated with a near infra-red photothermal dye; these liposomes are readily accumulated into cultured cells. The PP-InsPs remain trapped inside the liposomes until the cultures are illuminated with a near infra-red light-emitting diode (LED) which permeabilizes the liposomes to promote PP-InsP release. Additionally, so as to optimize these procedures, a novel stably fluorescent 5-InsP7 analogue (i.e., 5-FAM-InsP7) was synthesized with the assistance of click-chemistry; the delivery and deposition of the analogue inside cells was monitored by flow cytometry and by confocal microscopy. We describe quantitatively-controlled PP-InsP release inside cells within 5 min of LED irradiation, without measurable effect upon cell integrity, using a collimated 22 mm beam that can irradiate up to 106 cultured cells. Finally, to interrogate the biological value of these procedures, we delivered 1,5-InsP8 into HCT116 cells and showed it to dose-dependently stimulate the rate of [33P]-Pi uptake; these observations reveal a rheostatic range of concentrations over which 1,5-InsP8 is biologically functional in Pi homeostasis.
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Affiliation(s)
- Zhenzhen Wang
- Signal Transduction Laboratory , National Institute of Environmental Health Sciences , National Institutes of Health , Research Triangle Park , NC 27709 , USA . ; Tel: +1-984-287-3483
| | - Nikolaus Jork
- Institute of Organic Chemistry , CIBSS , Center for Integrative Biological Signalling Studies , University of Freiburg , 79104 Freiburg , Germany
| | - Tamara Bittner
- Institute of Organic Chemistry , CIBSS , Center for Integrative Biological Signalling Studies , University of Freiburg , 79104 Freiburg , Germany
| | - Huanchen Wang
- Signal Transduction Laboratory , National Institute of Environmental Health Sciences , National Institutes of Health , Research Triangle Park , NC 27709 , USA . ; Tel: +1-984-287-3483
| | - Henning J Jessen
- Institute of Organic Chemistry , CIBSS , Center for Integrative Biological Signalling Studies , University of Freiburg , 79104 Freiburg , Germany
| | - Stephen B Shears
- Signal Transduction Laboratory , National Institute of Environmental Health Sciences , National Institutes of Health , Research Triangle Park , NC 27709 , USA . ; Tel: +1-984-287-3483
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22
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Shears SB, Wang H. Metabolism and Functions of Inositol Pyrophosphates: Insights Gained from the Application of Synthetic Analogues. Molecules 2020; 25:E4515. [PMID: 33023101 PMCID: PMC7583957 DOI: 10.3390/molecules25194515] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 09/25/2020] [Accepted: 09/27/2020] [Indexed: 12/17/2022] Open
Abstract
Inositol pyrophosphates (PP-InsPs) comprise an important group of intracellular, diffusible cellular signals that a wide range of biological processes throughout the yeast, plant, and animal kingdoms. It has been difficult to gain a molecular-level mechanistic understanding of the actions of these molecules, due to their highly phosphorylated nature, their low levels, and their rapid metabolic turnover. More recently, these obstacles to success are being surmounted by the chemical synthesis of a number of insightful PP-InsP analogs. This review will describe these analogs and will indicate the important chemical and biological information gained by using them.
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Affiliation(s)
- Stephen B. Shears
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA;
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23
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InsP 7 is a small-molecule regulator of NUDT3-mediated mRNA decapping and processing-body dynamics. Proc Natl Acad Sci U S A 2020; 117:19245-19253. [PMID: 32727897 DOI: 10.1073/pnas.1922284117] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Regulation of enzymatic 5' decapping of messenger RNA (mRNA), which normally commits transcripts to their destruction, has the capacity to dynamically reshape the transcriptome. For example, protection from 5' decapping promotes accumulation of mRNAs into processing (P) bodies-membraneless, biomolecular condensates. Such compartmentalization of mRNAs temporarily removes them from the translatable pool; these repressed transcripts are stabilized and stored until P-body dissolution permits transcript reentry into the cytosol. Here, we describe regulation of mRNA stability and P-body dynamics by the inositol pyrophosphate signaling molecule 5-InsP7 (5-diphosphoinositol pentakisphosphate). First, we demonstrate 5-InsP7 inhibits decapping by recombinant NUDT3 (Nudix [nucleoside diphosphate linked moiety X]-type hydrolase 3) in vitro. Next, in intact HEK293 and HCT116 cells, we monitored the stability of a cadre of NUDT3 mRNA substrates following CRISPR-Cas9 knockout of PPIP5Ks (diphosphoinositol pentakisphosphate 5-kinases type 1 and 2, i.e., PPIP5K KO), which elevates cellular 5-InsP7 levels by two- to threefold (i.e., within the physiological rheostatic range). The PPIP5K KO cells exhibited elevated levels of NUDT3 mRNA substrates and increased P-body abundance. Pharmacological and genetic attenuation of 5-InsP7 synthesis in the KO background reverted both NUDT3 mRNA substrate levels and P-body counts to those of wild-type cells. Furthermore, liposomal delivery of a metabolically resistant 5-InsP7 analog into wild-type cells elevated levels of NUDT3 mRNA substrates and raised P-body abundance. In the context that cellular 5-InsP7 levels normally fluctuate in response to changes in the bioenergetic environment, regulation of mRNA structure by this inositol pyrophosphate represents an epitranscriptomic control process. The associated impact on P-body dynamics has relevance to regulation of stem cell differentiation, stress responses, and, potentially, amelioration of neurodegenerative diseases and aging.
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Austin S, Mayer A. Phosphate Homeostasis - A Vital Metabolic Equilibrium Maintained Through the INPHORS Signaling Pathway. Front Microbiol 2020; 11:1367. [PMID: 32765429 PMCID: PMC7381174 DOI: 10.3389/fmicb.2020.01367] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 05/27/2020] [Indexed: 12/12/2022] Open
Abstract
Cells face major changes in demand for and supply of inorganic phosphate (Pi). Pi is often a limiting nutrient in the environment, particularly for plants and microorganisms. At the same time, the need for phosphate varies, establishing conflicts of goals. Cells experience strong peaks of Pi demand, e.g., during the S-phase, when DNA, a highly abundant and phosphate-rich compound, is duplicated. While cells must satisfy these Pi demands, they must safeguard themselves against an excess of Pi in the cytosol. This is necessary because Pi is a product of all nucleotide-hydrolyzing reactions. An accumulation of Pi shifts the equilibria of these reactions and reduces the free energy that they can provide to drive endergonic metabolic reactions. Thus, while Pi starvation may simply retard growth and division, an elevated cytosolic Pi concentration is potentially dangerous for cells because it might stall metabolism. Accordingly, the consequences of perturbed cellular Pi homeostasis are severe. In eukaryotes, they range from lethality in microorganisms such as yeast (Sethuraman et al., 2001; Hürlimann, 2009), severe growth retardation and dwarfism in plants (Puga et al., 2014; Liu et al., 2015; Wild et al., 2016) to neurodegeneration or renal Fanconi syndrome in humans (Legati et al., 2015; Ansermet et al., 2017). Intracellular Pi homeostasis is thus not only a fundamental topic of cell biology but also of growing interest for medicine and agriculture.
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Affiliation(s)
- Sisley Austin
- Département de Biochimie, Université de Lausanne, Lausanne, Switzerland
| | - Andreas Mayer
- Département de Biochimie, Université de Lausanne, Lausanne, Switzerland
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25
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Cridland C, Gillaspy G. Inositol Pyrophosphate Pathways and Mechanisms: What Can We Learn from Plants? Molecules 2020; 25:E2789. [PMID: 32560343 PMCID: PMC7356102 DOI: 10.3390/molecules25122789] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 06/11/2020] [Accepted: 06/13/2020] [Indexed: 11/25/2022] Open
Abstract
The ability of an organism to maintain homeostasis in changing conditions is crucial for growth and survival. Eukaryotes have developed complex signaling pathways to adapt to a readily changing environment, including the inositol phosphate (InsP) signaling pathway. In plants and humans the pyrophosphorylated inositol molecules, inositol pyrophosphates (PP-InsPs), have been implicated in phosphate and energy sensing. PP-InsPs are synthesized from the phosphorylation of InsP6, the most abundant InsP. The plant PP-InsP synthesis pathway is similar but distinct from that of the human, which may reflect differences in how molecules such as Ins(1,4,5)P3 and InsP6 function in plants vs. animals. In addition, PP-InsPs can potentially interact with several major signaling proteins in plants, suggesting PP-InsPs play unique signaling roles via binding to protein partners. In this review, we will compare the biosynthesis and role of PP-InsPs in animals and plants, focusing on three central themes: InsP6 synthesis pathways, synthesis and regulation of the PP-InsPs, and function of a specific protein domain called the Syg1, Pho1, Xpr1 (SPX ) domain in binding PP-InsPs and regulating inorganic phosphate (Pi) sensing. This review will provide novel insights into the biosynthetic pathway and bioactivity of these key signaling molecules in plant and human systems.
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Affiliation(s)
| | - Glenda Gillaspy
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA;
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26
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Reiterer V, Pawłowski K, Desrochers G, Pause A, Sharpe HJ, Farhan H. The dead phosphatases society: a review of the emerging roles of pseudophosphatases. FEBS J 2020; 287:4198-4220. [PMID: 32484316 DOI: 10.1111/febs.15431] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/12/2020] [Accepted: 05/27/2020] [Indexed: 12/11/2022]
Abstract
Phosphatases are a diverse family of enzymes, comprising at least 10 distinct protein folds. Like most other enzyme families, many have sequence variations that predict an impairment or loss of catalytic activity classifying them as pseudophosphatases. Research on pseudoenzymes is an emerging area of interest, with new biological functions repurposed from catalytically active relatives. Here, we provide an overview of the pseudophosphatases identified to date in all major phosphatase families. We will highlight the degeneration of the various catalytic sequence motifs and discuss the challenges associated with the experimental determination of catalytic inactivity. We will also summarize the role of pseudophosphatases in various diseases and discuss the major challenges and future directions in this field.
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Affiliation(s)
| | | | - Guillaume Desrochers
- Department of Biochemistry, McGill University, Montréal, QC, Canada.,Goodman Cancer Research Centre, McGill University, Montréal, QC, Canada
| | - Arnim Pause
- Department of Biochemistry, McGill University, Montréal, QC, Canada.,Goodman Cancer Research Centre, McGill University, Montréal, QC, Canada
| | | | - Hesso Farhan
- Institute of Basic Medical Sciences, University of Oslo, Norway
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27
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Mukherjee S, Haubner J, Chakraborty A. Targeting the Inositol Pyrophosphate Biosynthetic Enzymes in Metabolic Diseases. Molecules 2020; 25:molecules25061403. [PMID: 32204420 PMCID: PMC7144392 DOI: 10.3390/molecules25061403] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/09/2020] [Accepted: 03/11/2020] [Indexed: 12/12/2022] Open
Abstract
In mammals, a family of three inositol hexakisphosphate kinases (IP6Ks) synthesizes the inositol pyrophosphate 5-IP7 from IP6. Genetic deletion of Ip6k1 protects mice from high fat diet induced obesity, insulin resistance and fatty liver. IP6K1 generated 5-IP7 promotes insulin secretion from pancreatic β-cells, whereas it reduces insulin signaling in metabolic tissues by inhibiting the protein kinase Akt. Thus, IP6K1 promotes high fat diet induced hyperinsulinemia and insulin resistance in mice while its deletion has the opposite effects. IP6K1 also promotes fat accumulation in the adipose tissue by inhibiting the protein kinase AMPK mediated energy expenditure. Genetic deletion of Ip6k3 protects mice from age induced fat accumulation and insulin resistance. Accordingly, the pan IP6K inhibitor TNP [N2-(m-trifluorobenzyl), N6-(p-nitrobenzyl)purine] ameliorates obesity, insulin resistance and fatty liver in diet induced obese mice by improving Akt and AMPK mediated insulin sensitivity and energy expenditure. TNP also protects mice from bone loss, myocardial infarction and ischemia reperfusion injury. Thus, the IP6K pathway is a potential target in obesity and other metabolic diseases. Here, we summarize the studies that established IP6Ks as a potential target in metabolic diseases. Further studies will reveal whether inhibition of this pathway has similar pleiotropic benefits on metabolic health of humans.
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