1
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Ravala SK, Adame-Garcia SR, Li S, Chen CL, Cianfrocco MA, Gutkind JS, Cash JN, Tesmer JJG. Structural and dynamic changes in P-Rex1 upon activation by PIP 3 and inhibition by IP 4. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.09.15.557836. [PMID: 37745379 PMCID: PMC10515948 DOI: 10.1101/2023.09.15.557836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
PIP3-dependent Rac exchanger 1 (P-Rex1) is abundantly expressed in neutrophils and plays central roles in chemotaxis and cancer metastasis by serving as a guanine-nucleotide exchange factor (GEF) for Rac. The enzyme is synergistically activated by PIP3 and the heterotrimeric Gβγ subunits, but mechanistic details remain poorly understood. While investigating the regulation of P-Rex1 by PIP3, we discovered that Ins(1,3,4,5)P4 (IP4) inhibits P-Rex1 activity and induces large decreases in backbone dynamics in diverse regions of the protein. Cryo-electron microscopy analysis of the P-Rex1·IP4 complex revealed a conformation wherein the pleckstrin homology (PH) domain occludes the active site of the Dbl homology (DH) domain. This configuration is stabilized by interactions between the first DEP domain (DEP1) and the DH domain and between the PH domain and a 4-helix bundle (4HB) subdomain that extends from the C-terminal domain of P-Rex1. Disruption of the DH-DEP1 interface in a DH/PH-DEP1 fragment enhanced activity and led to a more extended conformation in solution, whereas mutations that constrain the occluded conformation led to decreased GEF activity. Variants of full-length P-Rex1 in which the DH-DEP1 and PH-4HB interfaces were disturbed exhibited enhanced activity during chemokine-induced cell migration, confirming that the observed structure represents the autoinhibited state in living cells. Interactions with PIP3-containing liposomes led to disruption of these interfaces and increased dynamics protein-wide. Our results further suggest that inositol phosphates such as IP4 help to inhibit basal P-Rex1 activity in neutrophils, similar to their inhibitory effects on phosphatidylinositol-3-kinase.
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Affiliation(s)
- Sandeep K. Ravala
- Departments of Biological Sciences and of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907, United States
| | - Sendi Rafael Adame-Garcia
- Department of Pharmacology and Moores Cancer Center, University of California, San Diego, San Diego, CA 92093, USA
| | - Sheng Li
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - Chun-Liang Chen
- Departments of Biological Sciences and of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907, United States
| | - Michael A. Cianfrocco
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - J. Silvio Gutkind
- Department of Pharmacology and Moores Cancer Center, University of California, San Diego, San Diego, CA 92093, USA
| | - Jennifer N. Cash
- Department of Molecular and Cellular Biology, University of California-Davis, Davis, CA, 95616, USA
| | - John J. G. Tesmer
- Departments of Biological Sciences and of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907, United States
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2
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Frybortova V, Satka S, Jourova L, Zapletalova I, Srejber M, Briolotti P, Daujat-Chavanieu M, Gerbal-Chaloin S, Anzenbacher P, Otyepka M, Anzenbacherova E. On the Possible Effect of Phytic Acid (Myo-Inositol Hexaphosphoric Acid, IP6) on Cytochromes P450 and Systems of Xenobiotic Metabolism in Different Hepatic Models. Int J Mol Sci 2024; 25:3610. [PMID: 38612422 PMCID: PMC11011971 DOI: 10.3390/ijms25073610] [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: 02/14/2024] [Revised: 03/18/2024] [Accepted: 03/20/2024] [Indexed: 04/14/2024] Open
Abstract
As compounds of natural origin enter human body, it is necessary to investigate their possible interactions with the metabolism of drugs and xenobiotics in general, namely with the cytochrome P450 (CYP) system. Phytic acid (myo-inositol hexaphosphoric acid, IP6) is mainly present in plants but is also an endogenous compound present in mammalian cells and tissues. It has been shown to exhibit protective effect in many pathological conditions. For this paper, its interaction with CYPs was studied using human liver microsomes, primary human hepatocytes, the HepG2 cell line, and molecular docking. Docking experiments and absorption spectra demonstrated the weak ability of IP6 to interact in the heme active site of CYP1A. Molecular docking suggested that IP6 preferentially binds to the protein surface, whereas binding to the active site of CYP1A2 was found to be less probable. Subsequently, we investigated the ability of IP6 to modulate the metabolism of xenobiotics for both the mRNA expression and enzymatic activity of CYP1A enzymes. Our findings revealed that IP6 can slightly modulate the mRNA levels and enzyme activity of CYP1A. However, thanks to the relatively weak interactions of IP6 with CYPs, the chances of the mechanisms of clinically important drug-drug interactions involving IP6 are low.
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Affiliation(s)
- Veronika Frybortova
- Department of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University Olomouc, 775 15 Olomouc, Czech Republic; (V.F.); (E.A.)
| | - Stefan Satka
- Department of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University Olomouc, 775 15 Olomouc, Czech Republic; (V.F.); (E.A.)
| | - Lenka Jourova
- Department of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University Olomouc, 775 15 Olomouc, Czech Republic; (V.F.); (E.A.)
| | - Iveta Zapletalova
- Department of Pharmacology, Faculty of Medicine and Dentistry, Palacky University Olomouc, 775 15 Olomouc, Czech Republic;
| | - Martin Srejber
- Czech Advanced Technology and Research Institute (CATRIN), Palacky University Olomouc, 779 00 Olomouc, Czech Republic
| | - Philippe Briolotti
- Institute for Regenerative Medicine and Biotherapy (IRMB), University Montpellier, INSERM, CHU Montpellier, F-34000 Montpellier, France (S.G.-C.)
| | - Martine Daujat-Chavanieu
- Institute for Regenerative Medicine and Biotherapy (IRMB), University Montpellier, INSERM, CHU Montpellier, F-34000 Montpellier, France (S.G.-C.)
| | - Sabine Gerbal-Chaloin
- Institute for Regenerative Medicine and Biotherapy (IRMB), University Montpellier, INSERM, CHU Montpellier, F-34000 Montpellier, France (S.G.-C.)
| | - Pavel Anzenbacher
- Department of Pharmacology, Faculty of Medicine and Dentistry, Palacky University Olomouc, 775 15 Olomouc, Czech Republic;
| | - Michal Otyepka
- Czech Advanced Technology and Research Institute (CATRIN), Palacky University Olomouc, 779 00 Olomouc, Czech Republic
- IT4Innovations, VŠB—Technical University of Ostrava, 708 00 Ostrava, Czech Republic
| | - Eva Anzenbacherova
- Department of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University Olomouc, 775 15 Olomouc, Czech Republic; (V.F.); (E.A.)
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3
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Ricaña CL, Dick RA. Inositol Phosphates and Retroviral Assembly: A Cellular Perspective. Viruses 2021; 13:v13122516. [PMID: 34960784 PMCID: PMC8703376 DOI: 10.3390/v13122516] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 12/09/2021] [Accepted: 12/11/2021] [Indexed: 12/13/2022] Open
Abstract
Understanding the molecular mechanisms of retroviral assembly has been a decades-long endeavor. With the recent discovery of inositol hexakisphosphate (IP6) acting as an assembly co-factor for human immunodeficiency virus (HIV), great strides have been made in retroviral research. In this review, the enzymatic pathways to synthesize and metabolize inositol phosphates (IPs) relevant to retroviral assembly are discussed. The functions of these enzymes and IPs are outlined in the context of the cellular biology important for retroviruses. Lastly, the recent advances in understanding the role of IPs in retroviral biology are surveyed.
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4
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Ucuncu E, Rajamani K, Wilson MSC, Medina-Cano D, Altin N, David P, Barcia G, Lefort N, Banal C, Vasilache-Dangles MT, Pitelet G, Lorino E, Rabasse N, Bieth E, Zaki MS, Topcu M, Sonmez FM, Musaev D, Stanley V, Bole-Feysot C, Nitschké P, Munnich A, Bahi-Buisson N, Fossoud C, Giuliano F, Colleaux L, Burglen L, Gleeson JG, Boddaert N, Saiardi A, Cantagrel V. MINPP1 prevents intracellular accumulation of the chelator inositol hexakisphosphate and is mutated in Pontocerebellar Hypoplasia. Nat Commun 2020; 11:6087. [PMID: 33257696 PMCID: PMC7705663 DOI: 10.1038/s41467-020-19919-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Accepted: 10/29/2020] [Indexed: 12/13/2022] Open
Abstract
Inositol polyphosphates are vital metabolic and secondary messengers, involved in diverse cellular functions. Therefore, tight regulation of inositol polyphosphate metabolism is essential for proper cell physiology. Here, we describe an early-onset neurodegenerative syndrome caused by loss-of-function mutations in the multiple inositol-polyphosphate phosphatase 1 gene (MINPP1). Patients are found to have a distinct type of Pontocerebellar Hypoplasia with typical basal ganglia involvement on neuroimaging. We find that patient-derived and genome edited MINPP1−/− induced stem cells exhibit an inefficient neuronal differentiation combined with an increased cell death. MINPP1 deficiency results in an intracellular imbalance of the inositol polyphosphate metabolism. This metabolic defect is characterized by an accumulation of highly phosphorylated inositols, mostly inositol hexakisphosphate (IP6), detected in HEK293 cells, fibroblasts, iPSCs and differentiating neurons lacking MINPP1. In mutant cells, higher IP6 level is expected to be associated with an increased chelation of intracellular cations, such as iron or calcium, resulting in decreased levels of available ions. These data suggest the involvement of IP6-mediated chelation on Pontocerebellar Hypoplasia disease pathology and thereby highlight the critical role of MINPP1 in the regulation of human brain development and homeostasis. Tight regulation of inositol polyphosphate metabolism is essential for proper cell physiology. Here, the authors describe an early-onset neurodegenerative syndrome caused by loss-of-function mutations in the MINPP1 gene, characterised by intracellular imbalance of inositol polyphosphate metabolism.
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Affiliation(s)
- Ekin Ucuncu
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Karthyayani Rajamani
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Miranda S C Wilson
- MRC Laboratory for Molecular Cell Biology, University College London, WC1E 6BT, London, UK
| | - Daniel Medina-Cano
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Nami Altin
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Pierre David
- Transgenesis Platform, Laboratoire d'Expérimentation Animale et Transgenèse (LEAT), Imagine Institute, Structure Fédérative de Recherche Necker INSERM US24/CNRS UMS3633, 75015, Paris, France
| | - Giulia Barcia
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France.,Département de Génétique Médicale, AP-HP, Hôpital Necker-Enfants Malades, F-75015, Paris, France
| | - Nathalie Lefort
- Université de Paris, iPSC Core Facility, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Céline Banal
- Université de Paris, iPSC Core Facility, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | | | - Gaële Pitelet
- Service de Neuropédiatrie, CHU Nice, 06200, Nice, France
| | - Elsa Lorino
- ESEAN, 44200 Nantes, Service de maladies chroniques de l'enfant, CHU Nantes, 44093, Nantes, France
| | - Nathalie Rabasse
- Service de pédiatrie, hôpital d'Antibes-Juan-les-Pins, 06600, Antibes-Juan-les-Pins, France
| | - Eric Bieth
- Service de Génétique Médicale, CHU Toulouse, 31059, Toulouse, France
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, 12311, Egypt
| | - Meral Topcu
- Department of Child Neurology, Faculty of Medicine, Hacettepe University, Ankara, 06100, Turkey
| | - Fatma Mujgan Sonmez
- Guven Hospital, Child Neurology Department, Ankara, Turkey.,Department of Child Neurology, Faculty of Medicine, Karadeniz Technical University, Trabzon, 61080, Turkey
| | - Damir Musaev
- Laboratory for Pediatric Brain Diseases, Rady Children's Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Valentina Stanley
- Laboratory for Pediatric Brain Diseases, Rady Children's Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Christine Bole-Feysot
- Université de Paris, Genomics Platform, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Patrick Nitschké
- Université de Paris, Bioinformatics Core Facility, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Arnold Munnich
- Université de Paris, Translational Genetics Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Nadia Bahi-Buisson
- Université de Paris, Genetics and Development of the Cerebral Cortex Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Catherine Fossoud
- Centre de Référence des Troubles des Apprentissages, Hôpitaux Pédiatriques de Nice CHU-Lenval, 06200, Nice, France
| | - Fabienne Giuliano
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Nice, 06202, Nice, France
| | - Laurence Colleaux
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France
| | - Lydie Burglen
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France.,Centre de Référence des Malformations et Maladies Congénitales du Cervelet, Département de Génétique, AP-HP, Sorbonne Université, Hôpital Trousseau, 75012, Paris, France
| | - Joseph G Gleeson
- Laboratory for Pediatric Brain Diseases, Rady Children's Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Nathalie Boddaert
- Département de radiologie pédiatrique, INSERM UMR 1163 and INSERM U1000, AP-HP, Hôpital Necker-Enfants Malades, F-75015, Paris, France
| | - Adolfo Saiardi
- MRC Laboratory for Molecular Cell Biology, University College London, WC1E 6BT, London, UK.
| | - Vincent Cantagrel
- Université de Paris, Developmental Brain Disorders Laboratory, Imagine Institute, INSERM UMR 1163, F-75015, Paris, France.
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5
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McNamara DE, Dovey CM, Hale AT, Quarato G, Grace CR, Guibao CD, Diep J, Nourse A, Cai CR, Wu H, Kalathur RC, Green DR, York JD, Carette JE, Moldoveanu T. Direct Activation of Human MLKL by a Select Repertoire of Inositol Phosphate Metabolites. Cell Chem Biol 2019; 26:863-877.e7. [PMID: 31031142 DOI: 10.1016/j.chembiol.2019.03.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 02/08/2019] [Accepted: 03/15/2019] [Indexed: 12/29/2022]
Abstract
Necroptosis is an inflammatory form of programmed cell death executed through plasma membrane rupture by the pseudokinase mixed lineage kinase domain-like (MLKL). We previously showed that MLKL activation requires metabolites of the inositol phosphate (IP) pathway. Here we reveal that I(1,3,4,6)P4, I(1,3,4,5,6)P5, and IP6 promote membrane permeabilization by MLKL through directly binding the N-terminal executioner domain (NED) and dissociating its auto-inhibitory region. We show that IP6 and inositol pentakisphosphate 2-kinase (IPPK) are required for necroptosis as IPPK deletion ablated IP6 production and inhibited necroptosis. The NED auto-inhibitory region is more extensive than originally described and single amino acid substitutions along this region induce spontaneous necroptosis by MLKL. Activating IPs bind three sites with affinity of 100-600 μM to destabilize contacts between the auto-inhibitory region and NED, thereby promoting MLKL activation. We therefore uncover MLKL's activating switch in NED triggered by a select repertoire of IP metabolites.
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Affiliation(s)
- Dan E McNamara
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Cole M Dovey
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Andrew T Hale
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Giovanni Quarato
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Christy R Grace
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Cristina D Guibao
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jonathan Diep
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Amanda Nourse
- Molecular Interaction Analysis Shared Resource, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Casey R Cai
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Hong Wu
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Ravi C Kalathur
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Douglas R Green
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - John D York
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Jan E Carette
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Tudor Moldoveanu
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
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6
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Yin MX, Catimel B, Gregory M, Condron M, Kapp E, Holmes AB, Burgess AW. Synthesis of an inositol hexakisphosphate (IP6) affinity probe to study the interactome from a colon cancer cell line. Integr Biol (Camb) 2016; 8:309-18. [PMID: 26840369 DOI: 10.1039/c5ib00264h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Inositol hexakisphosphate (InsP6 or IP6) is an important signalling molecule in vesicular trafficking, neurotransmission, immune responses, regulation of protein kinases and phosphatases, activation of ion channels, antioxidant functions and anticancer activities. An IP6 probe was synthesised from myo-inositol via a derivatised analogue, which was immobilised through a terminal amino group onto Dynabeads. Systematic analysis of the IP6 interactome has been performed using the IP6 affinity probe using cytosolic extracts from the LIM1215 colonic carcinoma cell line. LC/MS/MS analysis identified 77 proteins or protein complexes that bind to IP6 specifically, including AP-2 complex proteins and β-arrestins as well as a number of novel potential IP6 interacting proteins. Bioinformatic enrichment analysis of the IP6 interactome reinforced the concept that IP6 regulates a number of biological processes including cell cycle and division, signal transduction, intracellular protein transport, vesicle-mediated transport and RNA splicing.
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Affiliation(s)
- Meng-Xin Yin
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3052, Australia
| | - Bruno Catimel
- Ludwig Institute for Cancer Research, Melbourne-Austin Branch, Olivia Newton-John Cancer & Wellness Centre, Studley Road, Heidelberg, Victoria 3084, Australia
| | - Mark Gregory
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3052, Australia
| | - Melanie Condron
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia. and Department of Medical Biology, University of Melbourne, Parkville, Victoria 3052, Australia
| | - Eugene Kapp
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia. and Department of Medical Biology, University of Melbourne, Parkville, Victoria 3052, Australia
| | - Andrew B Holmes
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3052, Australia
| | - Antony W Burgess
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia. and Department of Medical Biology, University of Melbourne, Parkville, Victoria 3052, Australia and Department of Surgery, RMH, University of Melbourne, Parkville, Victoria 3052, Australia
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7
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Veiga N, Macho I, Gómez K, González G, Kremer C, Torres J. Potentiometric and spectroscopic study of the interaction of 3d transition metal ions with inositol hexakisphosphate. J Mol Struct 2015. [DOI: 10.1016/j.molstruc.2015.05.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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8
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Abstract
Neutrophils play critical roles in innate immunity and host defense. However, excessive neutrophil accumulation or hyper-responsiveness of neutrophils can be detrimental to the host system. Thus, the response of neutrophils to inflammatory stimuli needs to be tightly controlled. Many cellular processes in neutrophils are mediated by localized formation of an inositol phospholipid, phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3), at the plasma membrane. The PtdIns(3,4,5)P3 signaling pathway is negatively regulated by lipid phosphatases and inositol phosphates, which consequently play a critical role in controlling neutrophil function and would be expected to act as ideal therapeutic targets for enhancing or suppressing innate immune responses. Here, we comprehensively review current understanding about the action of lipid phosphatases and inositol phosphates in the control of neutrophil function in infection and inflammation.
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Affiliation(s)
- Hongbo R Luo
- Department of Pathology, Harvard Medical School, Boston, MA, USA Department of Lab Medicine, Children's Hospital Boston, Dana-Farber/Harvard Cancer Center, Boston, MA, USA
| | - Subhanjan Mondal
- Department of Pathology, Harvard Medical School, Boston, MA, USA Department of Lab Medicine, Children's Hospital Boston, Dana-Farber/Harvard Cancer Center, Boston, MA, USA Promega Corporation, Madison, WI, USA
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9
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Torres J, Giorgi C, Veiga N, Kremer C, Bianchi A. Interaction of myo-inositol hexakisphosphate with biogenic and synthetic polyamines. Org Biomol Chem 2015; 13:7500-12. [DOI: 10.1039/c5ob00900f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
myo-Inositol hexakisphosphate (phytate) forms very stable adducts with biogenic and synthetic polyamines in aqueous solution.
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Affiliation(s)
- Julia Torres
- Cátedra de Química Inorgánica
- Departamento Estrella Campos
- Facultad de Química
- Universidad de la República
- Montevideo
| | - Claudia Giorgi
- Department of Chemistry “Ugo Schiff”
- University of Florence
- Sesto Fiorentino
- Italy
| | - Nicolás Veiga
- Cátedra de Química Inorgánica
- Departamento Estrella Campos
- Facultad de Química
- Universidad de la República
- Montevideo
| | - Carlos Kremer
- Cátedra de Química Inorgánica
- Departamento Estrella Campos
- Facultad de Química
- Universidad de la República
- Montevideo
| | - Antonio Bianchi
- Department of Chemistry “Ugo Schiff”
- University of Florence
- Sesto Fiorentino
- Italy
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10
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Veiga N, Torres J, Macho I, Gómez K, Godage HY, Riley AM, Potter BVL, González G, Kremer C. Inframolecular acid-base and coordination properties towards Na(+) and Mg(2+) of myo-inositol 1,3,4,5,6-pentakisphosphate: a structural approach to biologically relevant species. Dalton Trans 2013. [PMID: 23183928 PMCID: PMC4011121 DOI: 10.1039/c2dt31807e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The myo-inositol phosphates (InsPs) are specific signalling metabolites ubiquitous in eukaryotic cells. Although Ins(1,3,4,5,6)P(5) is the second most abundant member of the InsPs family, its certain biological roles are far from being elucidated, in part due to the large number of species formed by Ins(1,3,4,5,6)P(5) in the presence of metal ions. In light of this, we have strived in the past to make a complete and at the same time "biological-user-friendly" description of the Ins(1,3,4,5,6)P(5) chemistry with mono and multivalent cations. In this work we expand these studies focusing on the inframolecular aspects of its protonation equilibria and the microscopic details of its coordination behaviour towards biologically relevant metal ions. We present here a systematic study of the Ins(1,3,4,5,6)P(5) intrinsic acid-base processes, in a non-interacting medium, and over a wide pH range, analyzing the (31)P NMR curves by means of a model based on the Cluster Expansion Method. In addition, we have used a computational approach to analyse the energetic and structural features of the protonation and conformational changes of Ins(1,3,4,5,6)P(5), and how they are influenced by the presence of two physiologically relevant cations, Na(+) and Mg(2+).
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Affiliation(s)
- Nicolás Veiga
- Cátedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, CC 1157, Montevideo, Uruguay.
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11
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Shears SB, Ganapathi SB, Gokhale NA, Schenk TMH, Wang H, Weaver JD, Zaremba A, Zhou Y. Defining signal transduction by inositol phosphates. Subcell Biochem 2012; 59:389-412. [PMID: 22374098 PMCID: PMC3925325 DOI: 10.1007/978-94-007-3015-1_13] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ins(1,4,5)P(3) is a classical intracellular messenger: stimulus-dependent changes in its levels elicits biological effects through its release of intracellular Ca(2+) stores. The Ins(1,4,5)P(3) response is "switched off" by its metabolism to a range of additional inositol phosphates. These metabolites have themselves come to be collectively described as a signaling "family". The validity of that latter definition is critically examined in this review. That is, we assess the strength of the hypothesis that Ins(1,4,5)P(3) metabolites are themselves "classical" signals. Put another way, what is the evidence that the biological function of a particular inositol phosphate depends upon stimulus dependent changes in its levels? In this assessment, examples of an inositol phosphate acting as a cofactor (i.e. its function is not stimulus-dependent) do not satisfy our signaling criteria. We conclude that Ins(3,4,5,6)P(4) is, to date, the only Ins(1,4,5)P(3) metabolite that has been validated to act as a second messenger.
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Key Words
- adenosine deaminase
- akt
- β-cells
- calcium
- camp
- camkii
- chloride channel
- clc3
- compartmentalization
- dna repair
- endosomes
- erk
- frizzled receptor
- gap1ip4bp
- mrna export
- ins(1,4,5)p3
- ins(1,4,5)p4 receptor
- ins(1,3,4)p3
- ins(1,3,4,5)p4
- ins(1,3,4,5)p4 receptor
- ins(1,4,5,6)p4
- ins(3,4,5,6)p4
- ins(1,3,4,5,6)p5
- insp6
- insulin
- ipmk
- ipk2
- ip5k
- itp
- itpk1
- itpkb
- lymphocytes
- ku
- neutrophils
- protein phosphatase
- ptdins(4,5)p2
- ptdins(3,4,5)p3
- ph domain
- pten
- rasa3
- transcription
- wnt ligand
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Affiliation(s)
- Stephen B Shears
- Inositol Signaling Section, Laboratory of Signal Transduction, NIEHS, NIH, DHHS, Research Triangle Park, 27709, NC, USA, USA,
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12
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The behaviour of inositol 1,3,4,5,6-pentakisphosphate in the presence of the major biological metal cations. J Biol Inorg Chem 2009; 14:1001-13. [PMID: 19415348 PMCID: PMC2745655 DOI: 10.1007/s00775-009-0510-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 04/20/2009] [Indexed: 01/07/2023]
Abstract
The inositol phosphates are ubiquitous metabolites in eukaryotes, of which the most abundant are inositol hexakisphosphate (InsP 6) and inositol 1,3,4,5,6-pentakisphosphate [Ins(1,3,4,5,6)P5)]. These two compounds, poorly understood functionally, have complicated complexation and solid formation behaviours with multivalent cations. For InsP 6, we have previously described this chemistry and its biological implications (Veiga et al. in J Inorg Biochem 100:1800, 2006; Torres et al. in J Inorg Biochem 99:828, 2005). We now cover similar ground for Ins(1,3,4,5,6)P5, describing its interactions in solution with Na+, K+, Mg2+, Ca2+, Cu2+, Fe2+ and Fe3+, and its solid-formation equilibria with Ca2+ and Mg2+. Ins(1,3,4,5,6)P5 forms soluble complexes of 1:1 stoichiometry with all multivalent cations studied. The affinity for Fe3+ is similar to that of InsP6 and inositol 1,2,3-trisphosphate, indicating that the 1,2,3-trisphosphate motif, which Ins(1,3,4,5,6)P5 lacks, is not absolutely necessary for high-affinity Fe3+ complexation by inositol phosphates, even if it is necessary for their prevention of the Fenton reaction. With excess Ca2+ and Mg2+, Ins(1,3,4,5,6)P5 also forms the polymetallic complexes [M4(H2L)] [where L is fully deprotonated Ins(1,3,4,5,6)P5]. However, unlike InsP6, Ins(1,3,4,5,6)P5 is predicted not to be fully associated with Mg2+ under simulated cytosolic/nuclear conditions. The neutral Mg2+ and Ca2+ complexes have significant windows of solubility, but they precipitate as [Mg4(H2L)] x 23H2O or [Ca4(H2L)] x 16H2O whenever they exceed 135 and 56 microM in concentration, respectively. Nonetheless, the low stability of the [M4(H2L)] complexes means that the 1:1 species contribute to the overall solubility of Ins(1,3,4,5,6)P 5 even under significant Mg2+ or Ca2+ excesses. We summarize the solubility behaviour of Ins(1,3,4,5,6)P5 in straightforward plots.
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13
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Alcázar-Román AR, Wente SR. Inositol polyphosphates: a new frontier for regulating gene expression. Chromosoma 2007; 117:1-13. [DOI: 10.1007/s00412-007-0126-4] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2007] [Revised: 09/12/2007] [Accepted: 09/13/2007] [Indexed: 10/22/2022]
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14
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Jia Y, Subramanian KK, Erneux C, Pouillon V, Hattori H, Jo H, You J, Zhu D, Schurmans S, Luo HR. Inositol 1,3,4,5-tetrakisphosphate negatively regulates phosphatidylinositol-3,4,5- trisphosphate signaling in neutrophils. Immunity 2007; 27:453-67. [PMID: 17825589 PMCID: PMC2084373 DOI: 10.1016/j.immuni.2007.07.016] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2007] [Revised: 06/15/2007] [Accepted: 07/30/2007] [Indexed: 01/24/2023]
Abstract
Many neutrophil functions are regulated by phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P3) that mediates protein membrane translocation via binding to pleckstrin homolog (PH) domains within target proteins. Here we show that inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4), a cytosolic small molecule, bound the same PH domain of target proteins and competed for binding to PtdIns(3,4,5)P3. In neutrophils, chemoattractant stimulation triggered rapid elevation in Ins(1,3,4,5)P4 concentration. Depletion of Ins(1,3,4,5)P4 by deleting the gene encoding InsP3KB, which converts Ins(1,4,5)P3 to Ins(1,3,4,5)P4, enhanced membrane translocation of the PtdIns(3,4,5)P3-specific PH domain. This led to enhanced sensitivity to chemoattractant stimulation, elevated superoxide production, and enhanced neutrophil recruitment to inflamed peritoneal cavity. On the contrary, augmentation of intracellular Ins(1,3,4,5)P4 concentration blocked PH domain-mediated membrane translocation of target proteins and dramatically decreased the sensitivity of neutrophils to chemoattractant stimulation. These findings establish a role for Ins(1,3,4,5)P4 in cellular signal transduction pathways and provide another mechanism for modulating PtdIns(3,4,5)P3 signaling in neutrophils.
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Affiliation(s)
- Yonghui Jia
- Department of Pathology, Harvard Medical School, Dana-Farber/Harvard Cancer Center, Department of Lab Medicine, Children's Hospital Boston, Karp Family Research Building, Room 10214, Boston, MA 02115, USA
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15
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Veiga N, Torres J, Domínguez S, Mederos A, Irvine RF, Díaz A, Kremer C. The behaviour of myo-inositol hexakisphosphate in the presence of magnesium(II) and calcium(II): protein-free soluble InsP6 is limited to 49 microM under cytosolic/nuclear conditions. J Inorg Biochem 2006; 100:1800-10. [PMID: 16920196 PMCID: PMC1874250 DOI: 10.1016/j.jinorgbio.2006.06.016] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Revised: 06/21/2006] [Accepted: 06/25/2006] [Indexed: 11/30/2022]
Abstract
Progress in the biology of myo-inositol hexakisphosphate (InsP(6)) has been delayed by the lack of a quantitative description of its multiple interactions with divalent cations. Our recent initial description of these [J. Torres, S. Dominguez, M.F. Cerda, G. Obal, A. Mederos, R.F. Irvine, A. Diaz, C. Kremer, J. Inorg. Biochem. 99 (2005) 828-840] predicted that under cytosolic/nuclear conditions, protein-free soluble InsP(6) occurs as Mg(5)(H(2)L), a neutral complex that exists thanks to a significant, but undefined, window of solubility displayed by solid Mg(5)(H(2)L).22H(2)O (L is fully deprotonated InsP(6)). Here we complete the description of the InsP(6)-Mg(2+)-Ca(2+) system, defining the solubilities of the Mg(2+) and Ca(2+) (Ca(5)(H(2)L).16H(2)O) solids in terms of K(s0)=[M(2+)](5)[H(2)L(10-)], with pK(s0)=32.93 for M=Mg and pK(s0)=39.3 for M=Ca. The concentration of soluble Mg(5)(H(2)L) at 37 degrees C and I=0.15M NaClO(4) is limited to 49muM, yet InsP(6) in mammalian cells may reach 100muM. Any cytosolic/nuclear InsP(6) in excess of 49muM must be protein- or membrane-bound, or as solid Mg(5)(H(2)L).22H(2)O, and any extracellular InsP(6) (e.g. in plasma) is surely protein-bound.
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Affiliation(s)
- Nicolás Veiga
- Cátedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, Montevideo, Uruguay
| | - Julia Torres
- Cátedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, Montevideo, Uruguay
| | - Sixto Domínguez
- Departamento de Química Inorgánica, Universidad de La Laguna, Tenerife, Canary Islands, Spain
| | - Alfredo Mederos
- Departamento de Química Inorgánica, Universidad de La Laguna, Tenerife, Canary Islands, Spain
| | - Robin F. Irvine
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Alvaro Díaz
- Cátedra de Inmunología, Facultad de Química/Ciencias, Universidad de la República, Montevideo, Uruguay
- Corresponding authors. Fax: +598 2 4874320 (A. Díaz), +598 2 9241906 (C. Kremer).
| | - Carlos Kremer
- Cátedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, Montevideo, Uruguay
- Corresponding authors. Fax: +598 2 4874320 (A. Díaz), +598 2 9241906 (C. Kremer).
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16
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Casaravilla C, Brearley C, Soulé S, Fontana C, Veiga N, Bessio MI, Ferreira F, Kremer C, Díaz A. Characterization of myo-inositol hexakisphosphate deposits from larval Echinococcus granulosus. FEBS J 2006; 273:3192-203. [PMID: 16792701 DOI: 10.1111/j.1742-4658.2006.05328.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The abundant metabolite myo-inositol hexakisphosphate (InsP6) can form vesicular deposits with cations, a widespread phenomenon in plants also found in the cestode parasite, Echinococcus granulosus. In this organism, the deposits are exocytosed, accumulating in a host-exposed sheath of extracellular matrix termed the laminated layer. The formation and mobilization of InsP6 deposits, which involve precipitation and solubilization reactions, respectively, cannot yet be rationalized in quantitative chemical terms, as the solids involved have not been formally described. We report such a description for the InsP6 deposits from E. granulosus, purified as the solid residue left by mild alkaline digestion of the principal mucin component of the laminated layer. The deposits are largely composed of the compound Ca5H2L.16H2O (L representing fully deprotonated InsP6), and additionally contain Mg2+ (6-9% molar ratio with respect to Ca2+), but not K+. Calculations employing recently available chemical constants show that the precipitation of Ca5H2L.16H2O is predicted by thermodynamics in secretory vesicle-like conditions. The deposits appear to be similar to microcrystalline solids when analysed under the electron microscope; we estimate that each crystal comprises around 200 InsP6 molecules. We calculate that the deposits increase, by three orders of magnitude, the surface area available for adsorption of host proteins, a salient ability of the laminated layer. The major inositol phosphate in the deposits, other than InsP6, is myo-inositol (1,2,4,5,6) pentakisphosphate, or its enantiomer, inositol (2,3,4,5,6) pentakisphosphate. The compound appears to be a subproduct of the intracellular pathways leading to the synthesis and vesicular accumulation of InsP6, rather than arising from extracellular hydrolysis of InsP6.
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Affiliation(s)
- Cecilia Casaravilla
- Cátedra de Inmunología, Facultad de Química/Ciencias, Universidad de la República, Montevideo, Uruguay
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17
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Torres J, Domínguez S, Cerdá MF, Obal G, Mederos A, Irvine RF, Díaz A, Kremer C. Solution behaviour of myo-inositol hexakisphosphate in the presence of multivalent cations. Prediction of a neutral pentamagnesium species under cytosolic/nuclear conditions. J Inorg Biochem 2005; 99:828-40. [PMID: 15708805 DOI: 10.1016/j.jinorgbio.2004.12.011] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Revised: 12/20/2004] [Accepted: 12/21/2004] [Indexed: 10/26/2022]
Abstract
myo-Inositol hexakisphosphate (InsP6) is an ubiquitous and abundant molecule in the cytosol and nucleus of eukaryotic cells whose biological functions are incompletely known. A major hurdle for studying the biology of InsP6 has been a deficiency of a full understanding of the chemistry of its interaction with divalent and trivalent cations. This deficiency has limited our appreciation of how it remains in solution within cells, and the likely degree to which it might interact in vivo with physiologically important cations such as Ca2+ and Fe3+. We report here the initial part of the description of the InsP6-multivalent cation chemistry, including its solution equilibria studied by high resolution potentiometry and (for the Fe(III)/Fe(II) couple) cyclic voltammetry. InsP6 forms anionic complexes of high affinities and 1:1 stoichiometry with Mg(II), Ca(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II). Of particular importance is the observation that, in the exceptional case of Mg(II), InsP6 forms the species [Mg5(H2L)] (L representing fully deprotonated InsP6); this soluble neutral species is predicted to be the predominant form of InsP6 under nuclear or cytosolic conditions in animal cells. Contrary to previous suggestions, InsP6 is predicted not to interact with cytosolic calcium even when calcium is increased during signalling events. In vitro, InsP6 also forms high affinity 1:1 complexes with Fe(III) and Al(III). However, our data predict that in the biological context of excess free Mg(II), neither Fe(III) nor Fe(II) are complexed by InsP6.
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Affiliation(s)
- Julia Torres
- Cátedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, CC 1157, Montevideo, Uruguay
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18
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Abstract
When viewing the changes in our understanding of inositides over the last 20 years, it is difficult to know whether to be more impressed by the proliferation in the number of inositides themselves (e.g. seven polyphosphoinositol lipids, more than 30 inositol phosphates), or by the number of functions for each. This review will focus on two specific aspects of this diversity: the evolution of the polyphosphoinositides, and the synthesis and functions of the higher inositol phosphates.
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Affiliation(s)
- Robin F Irvine
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
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19
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Lehoux EA, Baker SM, Bush JA, Spivey HO. An assay of mammalian cell micropermeabilization based on measurements of cellular lactate production. Anal Biochem 2004; 334:234-8. [PMID: 15494129 DOI: 10.1016/j.ab.2004.08.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2004] [Indexed: 11/23/2022]
Abstract
A method for the quantitative assay of mammalian cell micropermeabilization is described. The method is based on the permeabilization-induced loss of endogenous glycolytic cofactors and consequent discontinuation of cellular lactate production. Advantages of the method include sensitivity and precision similar to that of micropermeabilization assays based on the release of 86Rb+ from preloaded cells, avoidance of radioactivity, and simplicity of the measurements and equipment required.
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Affiliation(s)
- Eric A Lehoux
- Department of Biochemistry and Molecular Biology, Noble Research Center, Oklahoma State University, Stillwater, OK 74078, USA.
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20
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Barker CJ, Wright J, Hughes PJ, Kirk CJ, Michell RH. Complex changes in cellular inositol phosphate complement accompany transit through the cell cycle. Biochem J 2004; 380:465-73. [PMID: 14992690 PMCID: PMC1224188 DOI: 10.1042/bj20031872] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2003] [Revised: 02/20/2004] [Accepted: 03/02/2004] [Indexed: 11/17/2022]
Abstract
Inositol polyphosphates other than Ins(1,4,5)P3 are involved in several aspects of cell regulation. For example, recent evidence has implicated InsP6, Ins(1,3,4,5,6)P5 and their close metabolic relatives, which are amongst the more abundant intracellular inositol polyphosphates, in chromatin organization, DNA maintenance, gene transcription, nuclear mRNA transport, membrane trafficking and control of cell proliferation. However, little is known of how the intracellular concentrations of inositol polyphosphates change through the cell cycle. Here we show that the concentrations of several inositol polyphosphates fluctuate in synchrony with the cell cycle in proliferating WRK-1 cells. InsP6, Ins(1,3,4,5,6)P5 and their metabolic relatives behave similarly: concentrations are high during G1-phase, fall to much lower levels during S-phase and rise again late in the cycle. The Ins(1,2,3)P3 concentration shows especially large fluctuations, and PP-InsP5 fluctuations are also very marked. Remarkably, Ins(1,2,3)P3 turns over fastest during S-phase, when its concentration is lowest. These results establish that several fairly abundant intracellular inositol polyphosphates, for which important biological roles are emerging, display dynamic behaviour that is synchronized with cell-cycle progression.
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21
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Perera NM, Michell RH, Dove SK. Hypo-osmotic Stress Activates Plc1p-dependent Phosphatidylinositol 4,5-Bisphosphate Hydrolysis and Inositol Hexakisphosphate Accumulation in Yeast. J Biol Chem 2004; 279:5216-26. [PMID: 14625296 DOI: 10.1074/jbc.m305068200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polyphosphoinositide-specific phospholipases (PICs) of the delta-subfamily are ubiquitous in eukaryotes, but an inability to control these enzymes physiologically has been a major obstacle to understanding their cellular function(s). Plc1p is similar to metazoan delta-PICs and is the only PIC in Saccharomyces cerevisiae. Genetic studies have implicated Plc1p in several cell functions, both nuclear and cytoplasmic. Here we show that a brief hypo-osmotic episode provokes rapid Plc1p-catalyzed hydrolysis of PtdIns(4,5)P2 in intact yeast by a mechanism independent of extracellular Ca2+. Much of this PtdIns(4,5)P2 hydrolysis occurs at the plasma membrane. The hydrolyzed PtdIns(4,5)P2 is mainly derived from PtdIns4P made by the PtdIns 4-kinase Stt4p. PtdIns(4,5)P2 hydrolysis occurs normally in mutants lacking Arg82p or Ipk1p, but they accumulate no InsP6, showing that these enzymes normally convert the liberated Ins(1,4,5)P3 rapidly and quantitatively to InsP6. We conclude that hypo-osmotic stress activates Plc1p-catalyzed PtdIns(4,5)P2 at the yeast plasma membrane and the liberated Ins(1,4,5)P3 is speedily converted to InsP6. This ability routinely to activate Plc1p-catalyzed PtdIns(4,5)P2 hydrolysis in vivo opens up new opportunities for molecular and genetic scrutiny of the regulation and functions of phosphoinositidases C of the delta-subfamily.
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Affiliation(s)
- Nevin M Perera
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
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22
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Shears SB. How versatile are inositol phosphate kinases? Biochem J 2004; 377:265-80. [PMID: 14567754 PMCID: PMC1223885 DOI: 10.1042/bj20031428] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2003] [Revised: 10/14/2003] [Accepted: 10/20/2003] [Indexed: 01/31/2023]
Abstract
This review assesses the extent and the significance of catalytic versatility shown by several inositol phosphate kinases: the inositol phosphate multikinase, the reversible Ins(1,3,4) P (3)/Ins(3,4,5,6) P (4) kinase, and the kinases that synthesize diphosphoinositol polyphosphates. Particular emphasis is placed upon data that are relevant to the situation in vivo. It will be shown that catalytic promiscuity towards different inositol phosphates is not typically an evolutionary compromise, but instead is sometimes exploited to facilitate tight regulation of physiological processes. This multifunctionality can add to the complexity with which inositol signalling pathways interact. This review also assesses some proposed additional functions for the catalytic domains, including transcriptional regulation, protein kinase activity and control by molecular 'switching', all in the context of growing interest in 'moonlighting' (gene-sharing) proteins.
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Affiliation(s)
- Stephen B Shears
- Inositol Signaling Section, Laboratory of Signal Transduction, NIEHS/NIH/DHSS Research Triangle Park, NC 27709, USA.
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23
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Hidaka K, Kanematsu T, Caffrey JJ, Takeuchi H, Shears SB, Hirata M. The importance to chondrocyte differentiation of changes in expression of the multiple inositol polyphosphate phosphatase. Exp Cell Res 2003; 290:254-64. [PMID: 14567985 DOI: 10.1016/s0014-4827(03)00337-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It is important to both physiological and pathological osteogenesis to understand the significance of changes in gene expression in growth-plate chondrocytes that transit between the proliferative and hypertrophic states. MINPP is one such gene of interest. The Minpp protein dephosphorylates highly phosphorylated inositol signaling molecules InsP(5) and InsP(6). We show here that the ATDC5 chondrocyte progenitor cell line can recapitulate developmentally specific changes in MINPP expression previously only seen in longitudinal bone growth plates-both an initial 2-3-fold increase and a subsequent decrease back to initial levels during transition to hypertrophy. The increase in MINPP expression was accompanied by a 40% decrease in InsP(6) levels in ATDC5 cells. However, InsP(5) levels were not modified. Furthermore, throughout the hypertrophic phase, during which MINPP expression decreased, there were no alterations in InsP(5) and InsP(6) levels. We also created an ATDC5 line that stably overexpressed Minpp at 2-fold higher levels than in wild-type cells. This had no significant effect upon cellular levels of InsP(5) and InsP(6). Thus, substantial changes in MINPP expression can occur without a net effect upon InsP(5) and InsP(6) turnover in vivo. On the other hand, Minpp-overexpressing cells showed impaired chondrogenesis. We noted that the expression of alkaline phosphatase activity was inversely correlated with the expression of MINPP. The ATDC5 cells that overexpress Minpp failed to show an insulin-dependent increase in alkaline phosphatase levels, which presumably affects phosphate balance [J. Biol. Chem. 276 (2001) 33995], and may be the reason cellular differentiation was impaired. In any case, we conclude that Minpp is important to chondrocyte differentiation, but in a manner that is, surprisingly, independent of inositol polyphosphate turnover.
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Affiliation(s)
- Kiyoshi Hidaka
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
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24
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Yu J, Leibiger B, Yang SN, Caffery JJ, Shears SB, Leibiger IB, Barker CJ, Berggren PO. Cytosolic multiple inositol polyphosphate phosphatase in the regulation of cytoplasmic free Ca2+ concentration. J Biol Chem 2003; 278:46210-8. [PMID: 12963730 DOI: 10.1074/jbc.m303743200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Multiple inositol polyphosphate phosphatase (MIPP) is an enzyme that, in vitro, has the interesting property of degrading higher inositol polyphosphates to the Ca2+ second messenger, inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), independently of inositol lipid breakdown. We hypothesized that a truncated cytosolic form of the largely endoplasmic reticulum-confined MIPP (cyt-MIPP) could represent an important new tool in the investigation of Ins(1,4,5)P3-dependent intracellular Ca2+ homeostasis. To optimize our ability to judge the impact of cyt-MIPP on intracellular Ca2+ concentration ([Ca2+]i) we chose a poorly responsive beta-cell line (HIT M2.2.2) with an abnormally low [Ca2+]i. Our results show for the first time in an intact mammalian cell that cyt-MIPP expression leads to a significant enhancement of Ins(1,4,5)P3 concentration. This is achieved without a significant interference from other cyt-MIPP-derived inositol phosphates. Furthermore, the low basal [Ca2+]i of these cells was raised to normal levels (35 to 115 nm) when they expressed cyt-MIPP. Noteworthy is that the normal feeble glucose-induced Ca2+ response of HIT M2.2.2 cells was enhanced dramatically by mechanisms related to this increase in basal [Ca2+]i. These data support the use of cyt-MIPP as an important tool in investigating Ins(1,4,5)P3-dependent Ca2+ homeostasis and suggest a close link between Ins(1,4,5)P3 concentration and basal [Ca2+]i, the latter being an important modulator of Ca2+ signaling in the pancreatic beta-cell.
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Affiliation(s)
- Jia Yu
- Department of Molecular Medicine, The Rolf Luft Center for Diabetes Research, L3, Karolinska Institutet, Karolinska Hospital, Stockholm SE-171 76, Sweden
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25
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Irigoín F, Ferreira F, Fernández C, Sim RB, Díaz A. myo-Inositol hexakisphosphate is a major component of an extracellular structure in the parasitic cestode Echinococcus granulosus. Biochem J 2002; 362:297-304. [PMID: 11853537 PMCID: PMC1222389 DOI: 10.1042/0264-6021:3620297] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
myo-Inositol hexakisphosphate (IP(6)) is an abundant intracellular component of animal cells. In this study we describe the presence of extracellular IP(6) in the hydatid cyst wall (HCW) of the larval stage of the cestode parasite Echinococcus granulosus. The HCW comprises an inner cellular layer and an outer, acellular (laminated) layer up to 2 mm in thickness that protects the parasite from host immune cells. A compound, subsequently identified as IP(6), was detected in and purified from an HCW extract on the basis of its capacity to inhibit complement activation. The identification of the isolated compound was carried out by a combination of NMR, MS and TLC. The majority of IP(6) in the HCW was found in the acellular layer, with only a small fraction of the compound being extracted from cells. In the laminated layer, IP(6) was present in association with calcium, and accounted for up to 15% of the total dry mass of the HCW. IP(6) was not detected in any other structures or stages of the parasite. Our results imply that IP(6) is secreted by the larval stage of the parasite in a polarized fashion towards the interface with the host. This is the first report of the secretion of IP(6), and the possible implications beyond the biology of E. granulosus are discussed.
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Affiliation(s)
- Florencia Irigoín
- Cátedra de Inmunología, Facultad de Química/Ciencias, Universidad de la República, Avenida Alfredo Navarro 3051, piso 2, CP 11600, Montevideo, Uruguay
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26
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Abstract
Following the discovery of inositol-1,4,5-trisphosphate as a second messenger, many other inositol phosphates were discovered in quick succession, with some understanding of their synthesis pathways and a few guesses at their possible functions. But then it all seemed to go comparatively quiet, with an explosion of interest in the inositol lipids. Now the water-soluble phase is once again becoming a focus of interest. Old and new data point to a new vista of inositol phosphates, with functions in many diverse aspects of cell biology, such as ion-channel physiology, membrane dynamics and nuclear signalling.
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Affiliation(s)
- R F Irvine
- Department of Pharmacology, Tennis Court Road, Cambridge CB2 1QJ, UK.
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27
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Abstract
This review assesses the authenticity of inositol hexakisphosphate (InsP(6)) being a wide-ranging regulator of many important cellular functions. Against a background in which the possible importance of localized InsP(6) metabolism is discussed, there is the facile explanation that InsP(6) is merely an "inactive" precursor for the diphosphorylated inositol phosphates. Indeed, many of the proposed cellular functions of InsP(6) cannot sustain a challenge from the implementation of a rigorous set of criteria, which are designed to avoid experimental artefacts.
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Affiliation(s)
- S B Shears
- Inositol Signaling Section, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, 27709, Research Triangle Park, NC, USA.
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28
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Chi H, Yang X, Kingsley PD, O'Keefe RJ, Puzas JE, Rosier RN, Shears SB, Reynolds PR. Targeted deletion of Minpp1 provides new insight into the activity of multiple inositol polyphosphate phosphatase in vivo. Mol Cell Biol 2000; 20:6496-507. [PMID: 10938126 PMCID: PMC86124 DOI: 10.1128/mcb.20.17.6496-6507.2000] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Multiple inositol polyphosphate phosphatase (Minpp1) metabolizes inositol 1,3,4,5,6-pentakisphosphate (InsP(5)) and inositol hexakisphosphate (InsP(6)) with high affinity in vitro. However, Minpp1 is compartmentalized in the endoplasmic reticulum (ER) lumen, where access of enzyme to these predominantly cytosolic substrates in vivo has not previously been demonstrated. To gain insight into the physiological activity of Minpp1, Minpp1-deficient mice were generated by homologous recombination. Tissue extracts from Minpp1-deficient mice lacked detectable Minpp1 mRNA expression and Minpp1 enzyme activity. Unexpectedly, Minpp1-deficient mice were viable, fertile, and without obvious defects. Although Minpp1 expression is upregulated during chondrocyte hypertrophy, normal chondrocyte differentiation and bone development were observed in Minpp1-deficient mice. Biochemical analyses demonstrate that InsP(5) and InsP(6) are in vivo substrates for ER-based Minpp1, as levels of these polyphosphates in Minpp1-deficient embryonic fibroblasts were 30 to 45% higher than in wild-type cells. This increase was reversed by reintroducing exogenous Minpp1 into the ER. Thus, ER-based Minpp1 plays a significant role in the maintenance of steady-state levels of InsP(5) and InsP(6). These polyphosphates could be reduced below their natural levels by aberrant expression in the cytosol of a truncated Minpp1 lacking its ER-targeting N terminus. This was accompanied by slowed cellular proliferation, indicating that maintenance of cellular InsP(5) and InsP(6) is essential to normal cell growth. Yet, depletion of cellular inositol polyphosphates during erythropoiesis emerges as an additional physiological activity of Minpp1; loss of this enzyme activity in erythrocytes from Minpp1-deficient mice was accompanied by upregulation of a novel, substitutive inositol polyphosphate phosphatase.
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Affiliation(s)
- H Chi
- Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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29
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Abstract
beta-amyloid (A beta) peptides are known to disrupt calcium homeostasis in cells. In the present study, the effects of A beta(25-35) upon the activity of soluble Ins(1,4,5)P3-5-phosphatase have been investigated. A beta(25-35) inhibited, and dithiothreitol (DTT) increased the activity of soluble rat cerebellar Ins(1,4,5)P3-5-phosphatase. The change in activity was not accompanied by an obvious change in the sensitivity of the Ins(1,4,5)P3-5-phosphatase to inhibition by glucose-6-phosphate or phytic acid. A beta(35-25) also inhibited soluble Ins(1,4,5)P3-5-phosphatase activity, but at a lower potency than A beta(25-35). It is concluded that A beta(25-35) affects the metabolism of Ins(1,4,5)P3 although the potency is not sufficiently high to contribute to any significant extent to the effects of this peptide upon calcium homeostasis.
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Affiliation(s)
- A Rönnbäck
- Department of Pharmacology and Clinical Neuroscience, Umeå University, Sweden
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30
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Caffrey JJ, Hidaka K, Matsuda M, Hirata M, Shears SB. The human and rat forms of multiple inositol polyphosphate phosphatase: functional homology with a histidine acid phosphatase up-regulated during endochondral ossification. FEBS Lett 1999; 442:99-104. [PMID: 9923613 DOI: 10.1016/s0014-5793(98)01636-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We have derived the full-length sequences of the human and rat forms of the multiple inositol polyphosphate phosphatase (MIPP); their structural and functional comparison with a chick histidine acid phosphatase (HiPER1) has revealed new information: (1) MIPP is approximately 50% identical to HiPER1, but the ER-targeting domains are divergent; (2) MIPP appears to share the catalytic requirement of histidine acid phosphatases, namely, a C-terminal His residue remote from the RHGxRxP catalytic motif; (3) rat MIPP mRNA is up-regulated during chondrocyte hypertrophy. The latter observation provides a context for proposing that MIPP may aid bone mineralization and salvage the inositol moiety prior to apoptosis.
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Affiliation(s)
- J J Caffrey
- Inositide Signaling Group, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA.
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31
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Shears SB. The versatility of inositol phosphates as cellular signals. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1436:49-67. [PMID: 9838040 DOI: 10.1016/s0005-2760(98)00131-3] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Cells from across the phylogenetic spectrum contain a variety of inositol phosphates. Many different functions have been ascribed to this group of compounds. However, it is remarkable how frequently several of these different inositol phosphates have been linked to various aspects of signal transduction. Therefore, this review assesses the evidence that inositol phosphates have evolved into a versatile family of second messengers.
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Affiliation(s)
- S B Shears
- Inositide Signalling Section, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
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32
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Huang CF, Voglmaier SM, Bembenek ME, Saiardi A, Snyder SH. Identification and purification of diphosphoinositol pentakisphosphate kinase, which synthesizes the inositol pyrophosphate bis(diphospho)inositol tetrakisphosphate. Biochemistry 1998; 37:14998-5004. [PMID: 9778378 DOI: 10.1021/bi981920l] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Diphosphoinositol pentakisphosphate (PP-IP5) and bis(diphospho)inositol tetrakisphosphate (bis-PP-IP4) were recently identified as inositol phosphates which possess pyrophosphate bonds. The molecular mechanisms that regulate the cellular levels of these compounds are not yet characterized. To pursue this question, we have previously purified an inositol hexakisphosphate (IP6) kinase from rat brain supernatants [Voglmaier, S. M., et al. (1996) Proc. Natl. Acad. Sci. U.S.A. 93, 4305-4310]. We now report the identification and purification of another novel kinase, diphosphoinositol pentakisphosphate (PP-IP5) kinase, which uses PP-IP5 as a substrate to form bis(diphospho)inositol tetrakisphosphate (bis-PP-IP4) in soluble fractions of rat forebrain. The purified protein, a monomer of 56 kDa, displays high affinity (Km = 0.7 microM) and selectivity for PP-IP5 as a substrate. The purified enzyme also can transfer a phosphate from bis-PP-IP4 to ADP to form ATP. This ATP synthase activity is an indication of the high phosphoryl group transfer potential of bis-PP-IP4 and may represent a physiological role for PP-IP5 and bis-PP-IP4.
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Affiliation(s)
- C F Huang
- Department of Neuroscience, Pharmacology & Molecular Sciences, and Psychiatry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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33
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Larsson O, Barker CJ, Sjöholm A, Carlqvist H, Michell RH, Bertorello A, Nilsson T, Honkanen RE, Mayr GW, Zwiller J, Berggren PO. Inhibition of phosphatases and increased Ca2+ channel activity by inositol hexakisphosphate. Science 1997; 278:471-4. [PMID: 9334307 DOI: 10.1126/science.278.5337.471] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Inositol hexakisphosphate (InsP6), the dominant inositol phosphate in insulin-secreting pancreatic beta cells, inhibited the serine-threonine protein phosphatases type 1, type 2A, and type 3 in a concentration-dependent manner. The activity of voltage-gated L-type calcium channels is increased in cells treated with inhibitors of serine-threonine protein phosphatases. Thus, the increased calcium channel activity obtained in the presence of InsP6 might result from the inhibition of phosphatase activity. Glucose elicited a transient increase in InsP6 concentration, which indicates that this inositol polyphosphate may modulate calcium influx over the plasma membrane and serve as a signal in the pancreatic beta cell stimulus-secretion coupling.
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Affiliation(s)
- O Larsson
- Rolf Luft Center for Diabetes Research, Department of Molecular Medicine, Karolinska Institute, S-171 76 Stockholm, Sweden
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34
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Van Dijken P, Bergsma JC, Van Haastert PJ. Phospholipase-C-independent inositol 1,4,5-trisphosphate formation in Dictyostelium cells. Activation of a plasma-membrane-bound phosphatase by receptor-stimulated Ca2+ influx. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 244:113-9. [PMID: 9063453 DOI: 10.1111/j.1432-1033.1997.00113.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Dictyostelium cells have enzyme activities that generate the inositol polyphosphate Ins(1,4,5)P3 from Ins(1,3,4,5,6)P5 via the intermediates Ins(1,3,4,5)P4 and Ins(1,4,5,6)P4. These enzyme activities could explain why cells with a deletion of the single phospholipase C gene (plc- cells) possess nearly normal Ins(1,4,5)P3 levels. In this study the regulation and the subcellular localization of the enzyme activities was investigated. The enzyme activities performing the different reaction steps from Ins(1,3,4,5,6)P5 to Ins(1,4,5)P3 are probably due to a single enzyme. Indications for this are the previously shown similar Ca2+ dependencies of the various reaction steps. Furthermore, the activities mediating the complete conversion of Ins(1,3,4,5,6)P5 to Ins(1,4,5)P3 co-purify after subcellular fractionation, solubilization, and chromatography of the proteins. Subcellular fractionation studies demonstrate that the enzyme is localized mainly at the inner face of the plasma membrane. The enzyme activity could not be stimulated in vitro by guanosine 5'-(3-thio)triphosphate, a procedure known to activate G-protein-coupled enzymes in Dictyostelium. Still, in plc- cells the level of Ins(1,4,5)P3 was increased significantly after stimulation with high concentrations of the extracellular ligand cAMP. This stimulation is most likely due to the influx of Ca2+ because no increase of Ins(1,4,5)P3 could be detected in the absence of extracellular Ca2+. The results demonstrate the existence of a new receptor-controlled route for the formation of Ins(1,4,5)P3 that is independent of phospholipase C.
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Affiliation(s)
- P Van Dijken
- Department of Biochemistry, University of Groningen, The Netherlands
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35
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Voglmaier SM, Bembenek ME, Kaplin AI, Dormán G, Olszewski JD, Prestwich GD, Snyder SH. Purified inositol hexakisphosphate kinase is an ATP synthase: diphosphoinositol pentakisphosphate as a high-energy phosphate donor. Proc Natl Acad Sci U S A 1996; 93:4305-10. [PMID: 8633060 PMCID: PMC39531 DOI: 10.1073/pnas.93.9.4305] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Diphosphoinositol pentakisphosphate (PP-IP5) and bis(diphospho)inositol tetrakisphosphate (bis-PP-IP4) are recently identified inositol phosphates that possess pyrophosphate bonds. We have purified an inositol hexakisphosphate (IP6) kinase from rat brain supernatants. The pure protein, a monomer of 54 kDa, displays high affinity (Km = 0.7 microM) and selectivity for inositol hexakisphosphate as substrate. It can be dissociated from bis(diphospho)inositol tetrakisphosphate synthetic activity. The purified enzyme transfers a phosphate from PP-IP5 to ADP to form ATP. This ATP synthase activity indicates the high phosphate group transfer potential of PP-IP5 and may represent a physiological role for PP-IP5.
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Affiliation(s)
- S M Voglmaier
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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36
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Kitchen E, Condliffe AM, Rossi AG, Haslett C, Chilvers ER. Characterization of inositol hexakisphosphate (InsP6)-mediated priming in human neutrophils: lack of extracellular [3H]-InsP6 receptors. Br J Pharmacol 1996; 117:979-85. [PMID: 8851521 PMCID: PMC1909423 DOI: 10.1111/j.1476-5381.1996.tb15291.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
1. Inositol hexakisphosphate (InsP6) is a ubiquitous and abundant cytosolic inositol phosphate that has been reported to prime human neutrophils for enhanced agonist-stimulated superoxide anion generation. This led to the proposal that the release of InsP6 from necrotic cells may augment the functional responsiveness of neutrophils at an inflammatory focus. The aim of this study was to examine whether the functional effects of InsP6 in neutrophils are receptor-mediated and establish the magnitude of this priming effect relative to other better characterized priming agents. 2. Analysis of [3H]-InsP6 binding to human neutrophil membranes in 20 mM Tris, 20 mM NaCl, 100 mM KCl, 5 mM EDTA (pH 7.7) buffer using 0.1 mg ml-1 membrane protein and 2.5 nM [3H]-InsP6 (90 min, 4 degrees C), demonstrated specific low affinity [3H]-InsP6 binding that was non-saturable up to a radioligand concentration of 10 nM. 3. [3H]-InsP6 displacement by InsP6 gave a Hill coefficient of 0.55 and best fitted a two-site logistic model (53% KD 150 nM, 47% KD 5 microM). [3H]-InsP6 binding also displayed low (3 fold) selectivity for InsP6 over Ins(1,3,4,5,6)P5. 4. The specific [3H]-InsP6 binding displayed a pH optimum of 8, was abolished by pre-boiling the membranes, and was enhanced by Ca2+, Mg2+ and Na+. 5. In incubations with intact neutrophils, where high levels of specific [3H]-LTB4 binding was observed, no [3H]-InsP6 binding could be identified. 6. Preincubation of neutrophils with 100 microM InsP6 had no effect on resting cell morphology, but caused a minor and transient (maximal at 30 s) enhancement of (0.1 nM) fMLP-induced shape change (% cells shape changed: fMLP 53 +/- 3%, fMLP+InsP6 66 +/- 4%). Similarly, InsP6 (100 microM, 30 s) had no effect on basal superoxide anion generation and, compared to lipopolysaccharide (LPS, 100 ng ml-1, 60 min), tumour necrosis factor-alpha (TNF alpha, 200 u ml-1, 30 min) or platelet-activating factor (PAF, 100 nM, 5 min) caused only a small enhancement of 100 nM fMLP-stimulated superoxide anion generation (fold-increase in superoxide anion generation over fMLP alone: InsP6 1.8 +/- 0.3, LPS 6.8 +/- 0.6, TNF alpha 5.2 +/- 0.7, PAF 5.8 +/- 0.6). 7. While these data support the presence of a specific, albeit low affinity, [3H]-InsP6 binding site in human neutrophil membrane preparations, the lack of binding to intact cells implies that the functional effects of InsP6 (ie. enhanced fMLP-stimulated superoxide anion generation and shape change) are not receptor-mediated.
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Affiliation(s)
- E Kitchen
- Department of Medicine (RIE), University of Edinburgh
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37
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Shears SB. Inositol pentakis- and hexakisphosphate metabolism adds versatility to the actions of inositol polyphosphates. Novel effects on ion channels and protein traffic. Subcell Biochem 1996; 26:187-226. [PMID: 8744266 DOI: 10.1007/978-1-4613-0343-5_7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- S B Shears
- Inositol Lipid Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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38
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Barker CJ, French PJ, Moore AJ, Nilsson T, Berggren PO, Bunce CM, Kirk CJ, Michell RH. Inositol 1,2,3-trisphosphate and inositol 1,2- and/or 2,3-bisphosphate are normal constituents of mammalian cells. Biochem J 1995; 306 ( Pt 2):557-64. [PMID: 7887911 PMCID: PMC1136554 DOI: 10.1042/bj3060557] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
1. An inositol trisphosphate (InsP3) distinct from Ins(1,4,5)P3 and Ins(1,3,4)P3, which we previously observed in myeloid and lymphoid cells [French, Bunce, Stephens, Lord, McConnell, Brown, Creba and Michell (1991) Proc R. Soc. London B 245, 193-201; Bunce, French, Allen, Mountford, Moore, Greaves, Michell and Brown (1993) Biochem. J. 289, 667-673], is present in WRK1 rat mammary tumour cells and pancreatic endocrine beta-cells. 2. It has been identified as Ins(1,2,3)P3 by a combination of oxidation to ribitol, a structurally diagnostic polyol, and ammoniacal hydrolysis to identified inositol monophosphates. 3. Ins(1,2,3)P3 concentration in HL60 cells changed little during stimulation by ATP or fMetLeuPhe or during neutrophilic or monocytic differentiation, and Ins(1,2,3)P3 was unresponsive to vasopressin in WRK1 cells. 4. Ins(1,2,3)P3 was usually more abundant than Ins(1,4,5)P3, often being present at concentrations between approximately 1 microM and approximately 10 microM. 5. HL60, WRK-1 and lymphoid cells also contain Ins(1,2)P2 or Ins(2,3)P2, or a mixture of these two enantiomers, as a major InsP2 species. 6. Ins(1,2,3)P3 and Ins(1,2)P2/Ins(2,3)P2 are readily detected in cells labelled for long periods, but not in acutely labelled cells. This behaviour resembles that of InsP6, the most abundant cellular inositol polyphosphate that includes the 1,2,3-trisphosphate motif, which also achieves isotopic equilibrium with inositol only slowly. 7. Ins(1,2,3)P3 is the major InsP3 that accumulates during metabolism of InsP6 by WRK-1 cell homogenates. 8. Possible metabolic relationships between Ins(1,2,3)P3, Ins(1,2)P2/Ins(2,3)P2 and other inositol polyphosphates in cells, and a possible role for Ins(1,2,3)P3 in cellular iron handling, are considered.
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Affiliation(s)
- C J Barker
- School of Biochemistry, University of Birmingham, UK
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