1
|
Abstract
The coupling of anion exchange high-pressure liquid chromatography (HPLC) with electrospray ionization mass spectrometry (ESI-MS) allows for the simultaneous detection of the six forms of inositol phosphate (InsP). Here we describe a rapid quantitative analysis of InsPs by HPLC-ESI-MS, which can be applied to a wide array of sample types. With this method, InsPs could be separated and detected within 20 min of sample injection. The detection limit was as low as 25 pmol (i.e., ca. 2 nmol/g sample) for each type of InsP, which is particularly important for analytes that are often present at low abundance in nature.
Collapse
|
2
|
Cordeiro CD, Saiardi A, Docampo R. The inositol pyrophosphate synthesis pathway in Trypanosoma brucei is linked to polyphosphate synthesis in acidocalcisomes. Mol Microbiol 2017; 106:319-333. [PMID: 28792096 DOI: 10.1111/mmi.13766] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2017] [Indexed: 12/19/2022]
Abstract
Inositol pyrophosphates are novel signaling molecules possessing high-energy pyrophosphate bonds and involved in a number of biological functions. Here, we report the correct identification and characterization of the kinases involved in the inositol pyrophosphate biosynthetic pathway in Trypanosoma brucei: inositol polyphosphate multikinase (TbIPMK), inositol pentakisphosphate 2-kinase (TbIP5K) and inositol hexakisphosphate kinase (TbIP6K). TbIP5K and TbIP6K were not identifiable by sequence alone and their activities were validated by enzymatic assays with the recombinant proteins or by their complementation of yeast mutants. We also analyzed T. brucei extracts for the presence of inositol phosphates using polyacrylamide gel electrophoresis and high-performance liquid chromatography. Interestingly, we could detect inositol phosphate (IP), inositol 4,5-bisphosphate (IP2 ), inositol 1,4,5-trisphosphate (IP3 ), and inositol hexakisphosphate (IP6 ) in T. brucei different stages. Bloodstream forms unable to produce inositol pyrophosphates, due to downregulation of TbIPMK expression by conditional knockout, have reduced levels of polyphosphate and altered acidocalcisomes. Our study links the inositol pyrophosphate pathway to the synthesis of polyphosphate in acidocalcisomes, and may lead to better understanding of these organisms and provide new targets for drug discovery.
Collapse
Affiliation(s)
- Ciro D Cordeiro
- Department of Cellular Biology, and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, WC1E 6BT, Gower Street, London, UK
| | - Roberto Docampo
- Department of Cellular Biology, and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
| |
Collapse
|
3
|
Phillippy BQ, Perera IY, Donahue JL, Gillaspy GE. Certain Malvaceae Plants Have a Unique Accumulation of myo-Inositol 1,2,4,5,6-Pentakisphosphate. PLANTS (BASEL, SWITZERLAND) 2015; 4:267-83. [PMID: 27135328 PMCID: PMC4844327 DOI: 10.3390/plants4020267] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 05/19/2015] [Indexed: 01/28/2023]
Abstract
Methods used to quantify inositol phosphates in seeds lack the sensitivity and specificity necessary to accurately detect the lower concentrations of these compounds contained in the leaves of many plants. In order to measure inositol hexakisphosphate (InsP₆) and inositol pentakisphosphate (InsP₅) levels in leaves of different plants, a method was developed to concentrate and pre-purify these compounds prior to analysis. Inositol phosphates were extracted from leaves with diluted HCl and concentrated on small anion exchange columns. Reversed-phase solid phase extraction cartridges were used to remove compounds that give peaks that sometimes interfere during HPLC. The method permitted the determination of InsP₆ and InsP₅ concentrations in leaves as low as 10 µM and 2 µM, respectively. Most plants analyzed contained a high ratio of InsP₆ to InsP₅. In contrast, certain members of the Malvaceae family, such as cotton (Gossypium) and some hibiscus (Hibiscus) species, had a preponderance of InsP₅. Radiolabeling of cotton seedlings also showed increased amounts of InsP₅ relative to InsP₆. Why some Malvaceae species exhibit a reversal of the typical ratios of these inositol phosphates is an intriguing question for future research.
Collapse
Affiliation(s)
- Brian Q Phillippy
- Plant and Microbial Biology, Campus Box 7612, North Carolina State University, Raleigh, NC 27695, USA.
| | - Imara Y Perera
- Plant and Microbial Biology, Campus Box 7612, North Carolina State University, Raleigh, NC 27695, USA.
| | - Janet L Donahue
- Biochemistry, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA.
| | - Glenda E Gillaspy
- Biochemistry, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA.
| |
Collapse
|
4
|
Loss O, Wu CT, Riccio A, Saiardi A. Modulation of inositol polyphosphate levels regulates neuronal differentiation. Mol Biol Cell 2013; 24:2981-9. [PMID: 23864704 PMCID: PMC3771958 DOI: 10.1091/mbc.e13-04-0198] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The modulation of inositol pentakisphosphate (IP5) and hexakisphosphate (IP6) intracellular levels controls the differentiation and survival of PC12 cells and primary neurons. These mechanisms are controlled by the levels of the protein kinase IP5-2K responsible for the conversion of IP5 into IP6. The binding of neurotrophins to tropomyosin receptor kinase receptors initiates several signaling pathways, including the activation of phospholipase C-γ, which promotes the release of diacylglycerol and inositol 1,4,5-trisphosphate (IP3). In addition to recycling back to inositol, IP3 serves as a precursor for the synthesis of higher phosphorylated inositols, such as inositol 1,3,4,5,6-pentakisphosphate (IP5) and inositol hexakisphosphate (IP6). Previous studies on the effect of neurotrophins on inositol signaling were limited to the analysis of IP3 and its dephosphorylation products. Here we demonstrate that nerve growth factor (NGF) regulates the levels of IP5 and IP6 during PC12 differentiation. Furthermore, both NGF and brain-derived neurotrophic factor alter IP5 and IP6 intracellular ratio in differentiated PC12 cells and primary neurons. Neurotrophins specifically regulate the expression of IP5-2 kinase (IP5-2K), which phosphorylates IP5 into IP6. IP5-2K is rapidly induced after NGF treatment, but its transcriptional levels sharply decrease in fully differentiated PC12 cells. Reduction of IP5-2K protein levels by small interfering RNA has an effect on the early stages of PC12 cell differentiation, whereas fully differentiated cells are not affected. Conversely, perturbation of IP5-2K levels by overexpression suggests that both differentiated PC12 cells and sympathetic neurons require low levels of the enzyme for survival. Therefore maintaining appropriate intracellular levels of inositol polyphosphates is necessary for neuronal survival and differentiation.
Collapse
Affiliation(s)
- Omar Loss
- Cell Biology Unit and Laboratory for Molecular Cell Biology, Medical Research Council, University College London, London WC1E 6BT, United Kingdom Department of Cell and Developmental Biology, University College London, London WC1E 6BT, United Kingdom Department of Neuroscience, University College London, London WC1E 6BT, United Kingdom
| | | | | | | |
Collapse
|
5
|
Banfic H, Bedalov A, York JD, Visnjic D. Inositol pyrophosphates modulate S phase progression after pheromone-induced arrest in Saccharomyces cerevisiae. J Biol Chem 2012. [PMID: 23179856 DOI: 10.1074/jbc.m112.412288] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Several studies have demonstrated the activation of phosphoinositide-specific phospholipase C (Plc) in nuclei of mammalian cells during synchronous progression through the cell cycle, but the downstream targets of Plc-generated inositol 1,4,5-trisphosphate are poorly described. Phospholipid signaling in the budding yeast Saccharomyces cerevisiae shares similarities with endonuclear phospholipid signaling in mammals, and many recent studies point to a role for inositol phosphates, including InsP(5), InsP(6), and inositol pyrophosphates, in mediating the action of Plc. In this study, we investigated the changes in inositol phosphate levels in α-factor-treated S. cerevisiae, which allows cells to progress synchronously through the cell cycle after release from a G(1) block. We found an increase in the activity of Plc1 early after release from the block with a concomitant increase in the levels of InsP(7) and InsP(8). Treatment of cells with the Plc inhibitor U73122 prevented increases in inositol phosphate levels and blocked progression of cells through S phase after pheromone arrest. The enzymatic activity of Kcs1 in vitro and HPLC analysis of [(3)H]inositol-labeled kcs1Δ cells confirmed that Kcs1 is the principal kinase responsible for generation of pyrophosphates in synchronously progressing cells. Analysis of plc1Δ, kcs1Δ, and ddp1Δ yeast mutants further confirmed the role that a Plc1- and Kcs1-mediated increase in pyrophosphates may have in progression through S phase. Our data provide genetic, metabolic, and biochemical evidence that synthesis of inositol pyrophosphates through activation of Plc1 and Kcs1 plays an important role in the signaling response required for cell cycle progression after mating pheromone arrest.
Collapse
Affiliation(s)
- Hrvoje Banfic
- Department of Physiology and Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Salata 3, 10 000 Zagreb, Croatia.
| | | | | | | |
Collapse
|
6
|
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.
Collapse
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
Collapse
Affiliation(s)
- Stephen B Shears
- Inositol Signaling Section, Laboratory of Signal Transduction, NIEHS, NIH, DHHS, Research Triangle Park, 27709, NC, USA, USA,
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Sakaguchi R, Tainaka K, Shimada N, Nakano S, Inoue M, Kiyonaka S, Mori Y, Morii T. An in vivo fluorescent sensor reveals intracellular ins(1,3,4,5)P4 dynamics in single cells. Angew Chem Int Ed Engl 2010; 49:2150-3. [PMID: 19899175 DOI: 10.1002/anie.200903951] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Reiko Sakaguchi
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Sauer K, Cooke MP. Regulation of immune cell development through soluble inositol-1,3,4,5-tetrakisphosphate. Nat Rev Immunol 2010; 10:257-71. [PMID: 20336153 PMCID: PMC2922113 DOI: 10.1038/nri2745] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The membrane lipid phosphatidylinositol-3,4,5-trisphosphate (PtdInsP(3)) regulates membrane receptor signalling in many cells, including immunoreceptor signalling. Here, we review recent data that have indicated essential roles for the soluble PtdInsP(3) analogue inositol-1,3,4,5-tetrakisphosphate (InsP(4)) in T cell, B cell and neutrophil development and function. Decreased InsP(4) production in leukocytes causes immunodeficiency in mice and might contribute to inflammatory vasculitis in Kawasaki disease in humans. InsP(4)-producing kinases could therefore provide attractive drug targets for inflammatory and infectious diseases.
Collapse
Affiliation(s)
- Karsten Sauer
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92037, USA.
| | | |
Collapse
|
9
|
Sakaguchi R, Tainaka K, Shimada N, Nakano S, Inoue M, Kiyonaka S, Mori Y, Morii T. An In Vivo Fluorescent Sensor Reveals Intracellular Ins(1,3,4,5)P4Dynamics in Single Cells. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200903951] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
10
|
Sauer K, Huang YH, Lin H, Sandberg M, Mayr GW. Phosphoinositide and inositol phosphate analysis in lymphocyte activation. CURRENT PROTOCOLS IN IMMUNOLOGY 2009; Chapter 11:11.1.1-11.1.46. [PMID: 19918943 PMCID: PMC4500525 DOI: 10.1002/0471142735.im1101s87] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Lymphocyte antigen receptor engagement profoundly changes the cellular content of phosphoinositide lipids and soluble inositol phosphates. Among these, the phosphoinositides phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-trisphosphate (PIP3) play key signaling roles by acting as pleckstrin homology (PH) domain ligands that recruit signaling proteins to the plasma membrane. Moreover, PIP2 acts as a precursor for the second messenger molecules diacylglycerol and soluble inositol 1,4,5-trisphosphate (IP3), essential mediators of PKC, Ras/Erk, and Ca2+ signaling in lymphocytes. IP3 phosphorylation by IP3 3-kinases generates inositol 1,3,4,5-tetrakisphosphate (IP4), an essential soluble regulator of PH domain binding to PIP3 in developing T cells. Besides PIP2, PIP3, IP3, and IP4, lymphocytes produce multiple other phosphoinositides and soluble inositol phosphates that could have important physiological functions. To aid their analysis, detailed protocols that allow one to simultaneously measure the levels of multiple different phosphoinositide or inositol phosphate isomers in lymphocytes are provided here. They are based on thin layer, conventional and high-performance liquid chromatographic separation methods followed by radiolabeling or non-radioactive metal-dye detection. Finally, less broadly applicable non-chromatographic methods for detection of specific phosphoinositide or inositol phosphate isomers are discussed. Support protocols describe how to obtain pure unstimulated CD4+CD8+ thymocyte populations for analyses of inositol phosphate turnover during positive and negative selection, key steps in T cell development.
Collapse
Affiliation(s)
- Karsten Sauer
- The Scripps Research Institute, La Jolla, California
| | | | - Hongying Lin
- University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Mark Sandberg
- Genomics Institute of the Novartis Research Foundation (GNF), San Diego, California
| | - Georg W Mayr
- University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| |
Collapse
|
11
|
Spry C, Saliba KJ. The human malaria parasite Plasmodium falciparum is not dependent on host coenzyme A biosynthesis. J Biol Chem 2009; 284:24904-13. [PMID: 19584050 PMCID: PMC2757193 DOI: 10.1074/jbc.m109.025312] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Indexed: 11/06/2022] Open
Abstract
Pantothenate, a precursor of the fundamental enzyme cofactor coenzyme A (CoA), is essential for growth of the intraerythrocytic stage of human and avian malaria parasites. Avian malaria parasites have been reported to be incapable of de novo CoA synthesis and instead salvage CoA from the host erythrocyte; hence, pantothenate is required for CoA biosynthesis within the host cell and not the parasite itself. Whether the same is true of the intraerythrocytic stage of the human malaria parasite, Plasmodium falciparum, remained to be established. In this study we investigated the metabolic fate of [(14)C]pantothenate within uninfected and P. falciparum-infected human erythrocytes. We provide evidence consistent with normal human erythrocytes, unlike rat erythrocytes (which have been reported to possess an incomplete CoA biosynthesis pathway), being capable of CoA biosynthesis from pantothenate. We also show that CoA biosynthesis is substantially higher in P. falciparum-infected erythrocytes and that P. falciparum, unlike its avian counterpart, generates most of the CoA synthesized in the infected erythrocyte, presumably necessitated by insufficient CoA biosynthesis in the host erythrocyte. Our data raise the possibility that malaria parasites rationalize their biosynthetic activity depending on the capacity of their host cell to synthesize the metabolites they require.
Collapse
Affiliation(s)
| | - Kevin J. Saliba
- From the Research School of Biology and
- Medical School, College of Medicine, Biology and Environment, The Australian National University, Canberra, ACT 0200, Australia
| |
Collapse
|
12
|
Lee WK, Lee SY, Kim WI, Rho YH, Bae YS, Lee C, Kim IY, Yu YG. Characterization of the InsP6-dependent interaction between CK2 and Nopp140. Biochem Biophys Res Commun 2008; 376:439-44. [DOI: 10.1016/j.bbrc.2008.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Accepted: 09/05/2008] [Indexed: 12/15/2022]
|
13
|
Berggren PO, Barker CJ. A key role for phosphorylated inositol compounds in pancreatic β-cell stimulus–secretion coupling. ACTA ACUST UNITED AC 2008; 48:276-94. [DOI: 10.1016/j.advenzreg.2007.11.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
14
|
Huang YH, Grasis JA, Miller AT, Xu R, Soonthornvacharin S, Andreotti AH, Tsoukas CD, Cooke MP, Sauer K. Positive regulation of Itk PH domain function by soluble IP4. Science 2007; 316:886-9. [PMID: 17412921 DOI: 10.1126/science.1138684] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Pleckstrin homology (PH) domain-mediated protein recruitment to cellular membranes is of paramount importance for signal transduction. The recruitment of many PH domains is controlled through production and turnover of their membrane ligand, phosphatidylinositol 3,4,5-trisphosphate (PIP3). We show that phosphorylation of the second messenger inositol 1,4,5-trisphosphate (IP3) into inositol 1,3,4,5-tetrakisphosphate (IP4) establishes another mode of PH domain regulation through a soluble ligand. At physiological concentrations, IP4 promoted PH domain binding to PIP3. In primary mouse CD4+CD8+ thymocytes, this was required for full activation of the protein tyrosine kinase Itk after T cell receptor engagement. Our data suggest that IP4 establishes a feedback loop of phospholipase C-gamma1 activation through Itk that is essential for T cell development.
Collapse
Affiliation(s)
- Yina H Huang
- Department of Immunology, Scripps Research Institute, La Jolla, CA 92037, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Kim YK, Lee KJ, Jeon H, Yu YG. Protein kinase CK2 is inhibited by human nucleolar phosphoprotein p140 in an inositol hexakisphosphate-dependent manner. J Biol Chem 2006; 281:36752-7. [PMID: 17038328 DOI: 10.1074/jbc.m604785200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein kinase CK2 is a ubiquitous protein kinase that can phosphorylate various proteins involved in central cellular processes, such as signal transduction, cell division, and proliferation. We have shown that the human nucleolar phosphoprotein p140 (hNopp140) is able to regulate the catalytic activity of CK2. Unphosphorylated hNopp140 and phospho-hNopp140 bind to the regulatory and catalytic subunits of CK2, respectively, and the interaction between hNopp140 and CK2 was prevented by inositol hexakisphosphate (InsP(6)). Phosphorylation of alpha-casein, genimin, or human phosphatidylcholine transfer protein-like protein by CK2 was inhibited by hNopp140, and InsP(6) recovered the suppressed activity of CK2 by hNopp140. These observations indicated that hNopp140 serves as a negative regulator of CK2 and that InsP(6) stimulates the activity of CK2 by blocking the interaction between hNopp140 and CK2.
Collapse
Affiliation(s)
- Yun-Kyoung Kim
- Department of Chemistry, Kookmin University, 861-1 Jeoungneung-dong, Songbuk-gu, 136-702 Seoul, Korea
| | | | | | | |
Collapse
|
16
|
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: 58] [Impact Index Per Article: 3.2] [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.
Collapse
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).
| |
Collapse
|
17
|
Spry C, Chai CLL, Kirk K, Saliba KJ. A class of pantothenic acid analogs inhibits Plasmodium falciparum pantothenate kinase and represses the proliferation of malaria parasites. Antimicrob Agents Chemother 2005; 49:4649-57. [PMID: 16251308 PMCID: PMC1280137 DOI: 10.1128/aac.49.11.4649-4657.2005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2005] [Revised: 06/14/2005] [Accepted: 08/22/2005] [Indexed: 11/20/2022] Open
Abstract
The growth and proliferation of the human malaria parasite Plasmodium falciparum are dependent on the parasite's ability to obtain essential nutrients. One nutrient for which the parasite has an absolute requirement is the water-soluble vitamin pantothenic acid (vitamin B5). In this study, a series of pantothenic acid analogs which retain the 2,4-dihydroxy-3,3-dimethylbutyramide core of pantothenic acid but deviate in structure from one another and from pantothenic acid in the nature of the substituent attached to the amide nitrogen were synthesized using an efficient single-step synthetic route. Eight of 10 analogs tested inhibited the proliferation of intraerythrocytic P. falciparum parasites in vitro, doing so with 50% inhibitory concentrations between 15 and 200 microM. The compounds were generally selective, inhibiting the proliferation of a human cell line (the Jurkat cell line) only at concentrations severalfold higher than those required for inhibition of parasite growth. It was demonstrated that compounds in this series inhibited the phosphorylation of pantothenic acid by pantothenate kinase, the first step in the parasite's biosynthesis of the essential enzyme cofactor coenzyme A, doing so competitively, with K(i) values in the nanomolar range.
Collapse
Affiliation(s)
- Christina Spry
- School of Biochemistry and Molecular Biology, The Australian National University, Canberra ACT 0200, Australia
| | | | | | | |
Collapse
|
18
|
Deleu S, Choi K, Pesesse X, Cho J, Sulis ML, Parsons R, Shears SB. Physiological levels of PTEN control the size of the cellular Ins(1,3,4,5,6)P(5) pool. Cell Signal 2005; 18:488-98. [PMID: 15979280 DOI: 10.1016/j.cellsig.2005.05.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2005] [Revised: 05/17/2005] [Accepted: 05/24/2005] [Indexed: 12/27/2022]
Abstract
To understand how a signaling molecule's activities are regulated, we need insight into the processes controlling the dynamic balance between its synthesis and degradation. For the Ins(1,3,4,5,6)P5 signal, this information is woefully inadequate. For example, the only known cytosolic enzyme with the capacity to degrade Ins(1,3,4,5,6)P5 is the tumour-suppressor PTEN [J.J. Caffrey, T. Darden, M.R. Wenk, S.B. Shears, FEBS Lett. 499 (2001) 6 ], but the biological relevance has been questioned by others [E.A. Orchiston, D. Bennett, N.R. Leslie, R.G. Clarke, L. Winward, C.P. Downes, S.T. Safrany, J. Biol. Chem. 279 (2004) 1116 ]. The current study emphasizes the role of physiological levels of PTEN in Ins(1,3,4,5,6)P5 homeostasis. We employed two cell models. First, we used a human U87MG glioblastoma PTEN-null cell line that hosts an ecdysone-inducible PTEN expression system. Second, the human H1299 bronchial cell line, in which PTEN is hypomorphic due to promoter methylation, has been stably transfected with physiologically relevant levels of PTEN. In both models, a novel consequence of PTEN expression was to increase Ins(1,3,4,5,6)P5 pool size by 30-40% (p<0.01); this response was wortmannin-insensitive and, therefore, independent of the PtdIns 3-kinase pathway. In U87MG cells, induction of the G129R catalytically inactive PTEN mutant did not affect Ins(1,3,4,5,6)P(5) levels. PTEN induction did not alter the expression of enzymes participating in Ins(1,3,4,5,6)P5 synthesis. Another effect of PTEN expression in U87MG cells was to decrease InsP6 levels by 13% (p<0.02). The InsP6-phosphatase, MIPP, may be responsible for the latter effect; we show that recombinant human MIPP dephosphorylates InsP6 to D/L-Ins(1,2,4,5,6)P5, levels of which increased 60% (p<0.05) following PTEN expression in U87MG cells. Overall, our data add higher inositol phosphates to the list of important cellular regulators [Y. Huang, R.P. Wernyj, D.D. Norton, P. Precht, M.C. Seminario, R.L. Wange, Oncogene, 24 (2005) 3819 ] the levels of which are modulated by expression of the highly pleiotropic PTEN protein.
Collapse
Affiliation(s)
- Sandrine Deleu
- Inositol Signaling Section, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHSS, Research Triangle Park, NC 27709, USA
| | | | | | | | | | | | | |
Collapse
|
19
|
Wen BG, Pletcher MT, Warashina M, Choe SH, Ziaee N, Wiltshire T, Sauer K, Cooke MP. Inositol (1,4,5) trisphosphate 3 kinase B controls positive selection of T cells and modulates Erk activity. Proc Natl Acad Sci U S A 2004; 101:5604-9. [PMID: 15064401 PMCID: PMC397439 DOI: 10.1073/pnas.0306907101] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mechanisms governing positive selection of T cells in the thymus are still incompletely understood. Here, we describe a N-ethyl-N-nitrosourea induced recessive mouse mutant, Ms. T-less, which lacks T cells in the peripheral blood because of a complete block of thymocyte development at the CD4(+)CD8(+) stage. Single nucleotide polymorphism mapping and candidate gene sequencing revealed a nonsense mutation in the inositol (1,4,5) trisphosphate 3 kinase B (Itpkb) gene in Ms. T-less mice. Accordingly, Ms. T-less thymocytes do not show detectable expression of Itpkb protein and have drastically reduced basal inositol (1,4,5) trisphosphate kinase activity. Itpkb converts inositol (1,4,5) trisphosphate to inositol (1,3,4,5) tetrakisphosphate, soluble second messengers that have been implicated in Ca(2+) signaling. Surprisingly, Ca(2+) responses show no significant differences between wild type (WT) and mutant thymocytes. However, extracellular signal-regulated kinase (Erk) activation in response to suboptimal antigen receptor stimulation is attenuated in Ms. T-less thymocytes, suggesting a role for Itpkb in linking T cell receptor signaling to efficient and sustained Erk activation.
Collapse
Affiliation(s)
- Ben G Wen
- Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, CA 92121, USA
| | | | | | | | | | | | | | | |
Collapse
|
20
|
Orchiston EA, Bennett D, Leslie NR, Clarke RG, Winward L, Downes CP, Safrany ST. PTEN M-CBR3, a versatile and selective regulator of inositol 1,3,4,5,6-pentakisphosphate (Ins(1,3,4,5,6)P5). Evidence for Ins(1,3,4,5,6)P5 as a proliferative signal. J Biol Chem 2003; 279:1116-22. [PMID: 14561749 DOI: 10.1074/jbc.m310933200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The PTEN (phosphatase and tensin homologue deleted on chromosome 10) tumor suppressor is a phosphatidylinositol 3,4,5-trisphosphate (PtdInsP3) 3-phosphatase that plays a crucial role in regulating many cellular processes by antagonizing the phosphoinositide 3-kinase signaling pathway. Although able to metabolize soluble inositol phosphates in vitro, the question of their significance as physiological substrates is unresolved. We show that inositol phosphates are not regulated by wild type PTEN, but that a synthetic mutant, PTEN M-CBR3, previously thought to be inactive toward inositides, can selectively regulate inositol 1,3,4,5,6-pentakisphosphate (Ins(1,3,4,5,6)P5). Transfection of U87-MG cells with PTEN M-CBR3 lowered Ins(1,3,4,5,6)P5 levels by 60% without detectable effect on PtdInsP3. Although PTEN M-CBR3 is a 3-phosphatase, levels of myo-inositol 1,4,5,6-tetrakisphosphate were not increased, whereas myo-inositol 1,3,4,6-tetrakisphospate levels increased by 80%. We have used PTEN M-CBR3 to study the physiological function of Ins(1,3,4,5,6)P5 and have found that Ins(1,3,4,5,6)P5 does not modulate PKB phosphorylation, nor does it regulate clathrin-mediated epidermal growth factor receptor internalization. By contrast, PTEN M-CBR3 expression, and the subsequent lowering of Ins(1,3,4,5,6)P5, are associated with reduced anchorage-independent colony formation and anchorage-dependent proliferation in U87-MG cells. Our results, together with previously published data, suggest that Ins(1,3,4,5,6)P5 has a role in proliferation.
Collapse
Affiliation(s)
- Elaine A Orchiston
- Division of Cell Signalling, Faculty of Life Sciences, MSI/WTB Complex, Dow St., The University of Dundee, Dundee DD1 5EH, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
21
|
Pouillon V, Hascakova-Bartova R, Pajak B, Adam E, Bex F, Dewaste V, Van Lint C, Leo O, Erneux C, Schurmans S. Inositol 1,3,4,5-tetrakisphosphate is essential for T lymphocyte development. Nat Immunol 2003; 4:1136-43. [PMID: 14517551 DOI: 10.1038/ni980] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2003] [Accepted: 08/26/2003] [Indexed: 11/09/2022]
Abstract
Inositol 1,4,5-trisphosphate (Ins(1,4,5)P(3)) is phosphorylated by Ins(1,4,5)P(3) 3-kinase, generating inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P(4)). The physiological function of Ins(1,3,4,5)P(4) is still unclear, but it has been reported to be a potential modulator of calcium mobilization. Disruption of the gene encoding the ubiquitously expressed Ins(1,4,5)P(3) 3-kinase isoform B (Itpkb) in mice caused a severe T cell deficiency due to major alterations in thymocyte responsiveness and selection. However, we were unable to detect substantial defects in Ins(1,4,5)P(3) amounts or calcium mobilization in Itpkb(-/-) thymocytes. These data indicate that Itpkb and Ins(1,3,4,5)P(4) define an essential signaling pathway for T cell precursor responsiveness and development.
Collapse
Affiliation(s)
- Valérie Pouillon
- IRIBHM, IBMM, rue des Professeurs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Affiliation(s)
- Brian Q Phillippy
- United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA 70124, USA
| |
Collapse
|
23
|
Mishra J, Bhalla US. Simulations of inositol phosphate metabolism and its interaction with InsP(3)-mediated calcium release. Biophys J 2002; 83:1298-316. [PMID: 12202356 PMCID: PMC1302229 DOI: 10.1016/s0006-3495(02)73901-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Inositol phosphates function as second messengers for a variety of extracellular signals. Ins(1,4,5)P(3) generated by phospholipase C-mediated hydrolysis of phosphatidylinositol bisphosphate, triggers numerous cellular processes by regulating calcium release from internal stores. The Ins(1,4,5)P(3) signal is coupled to a complex metabolic cascade involving a series of phosphatases and kinases. These enzymes generate a range of inositol phosphate derivatives, many of which have signaling roles of their own. We have integrated published biochemical data to build a mass action model for InsP(3) metabolism. The model includes most inositol phosphates that are currently known to interact with each other. We have used this model to study the effects of a G-protein coupled receptor stimulus that activates phospholipase C on the inositol phosphates. We have also monitored how the metabolic cascade interacts with Ins(1,4,5)P(3)-mediated calcium release. We find temporal dynamics of most inositol phosphates to be strongly influenced by the elaborate networking. We also show that Ins(1,3,4,5)P(4) plays a key role in InsP(3) dynamics and allows for paired pulse facilitation of calcium release. Calcium oscillations produce oscillatory responses in parts of the metabolic network and are in turn temporally modulated by the metabolism of InsP(3).
Collapse
Affiliation(s)
- Jyoti Mishra
- National Centre for Biological Sciences, GKVK Campus, Bangalore 560065, India.
| | | |
Collapse
|
24
|
Grases F, Simonet BM, Vucenik I, Perelló J, Prieto RM, Shamsuddin AM. Effects of exogenous inositol hexakisphosphate (InsP(6)) on the levels of InsP(6) and of inositol trisphosphate (InsP(3)) in malignant cells, tissues and biological fluids. Life Sci 2002; 71:1535-46. [PMID: 12127908 DOI: 10.1016/s0024-3205(02)01927-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
InsP(6) is abundant in cereals and legumes. InsP(6) and lower inositol phosphates, in particular InsP(3), participate in important intracellular processes. In addition, InsP(6) possess significant health benefits, such as anti-cancer effect, kidney stones prevention, lowering serum cholesterol. Because of the insensitivity of existing methods for determination of non-radiolabeled inositol phosphates, little is known about the natural occurrence, much less on the concentrations of InsP(6) and InsP(3) in biological samples. Using gas chromatography-mass detection analysis of HPLC chromatographic fractions, we report a measurement of unlabeled total InsP(3) and InsP(6) (a) as they occur within cells culture, tissues, and plasma, and (b) their changes depending on the presence of exogenous InsP(6). When rats were fed on a purified diet in which InsP(6) was undetectable (AIN-76A) the levels of InsP(6) in brain were 3.35 +/- 0.57 (SE) micromol.kg(-1) and in plasma 0.023 +/- 0.008 (SE) micromol.l(-1). The presence of InsP(6) in diet dramatically influenced its levels in brain and in plasma. When rats were given an InsP(6)-sufficient diet (AIN-76A + 1% InsP(6)), the levels of InsP(6) were about 100-fold higher in brain tissues (36.8 +/- 1.8 (SE)) than in plasma (0.29 +/- 0.02 (SE)); InsP(6) concentrations were 8.5-fold higher than total InsP(3) concentrations in either plasma (0.033 +/- 0.012 (SE)) and brain (4.21 +/- 0.55 (SE)). When animals were given an InsP(6)-poor diet (AIN-76A only), there was a 90% decrease in InsP(6) content in both brain tissue and plasma (p < 0.001); however, there was no change in the level of total InsP(3). In non-stimulated malignant cells (MDA-MB 231 and K562) the InsP(6) contents were 16.2 +/- 9.1 (SE) micromol.kg(-1) for MDA-MB 231 cells and 15.6 +/- 2.7 (SE) for K 562 cells. These values were around 3-fold higher than those of InsP(3) (4.8 +/- 0.5 micromol.kg(-1) and 6.9 +/- 0.1 (SE) for MDA-MB 231 and K562 cells respectively). Treatment of malignant cells with InsP(6) resulted in a 2-fold increase in the intracellular concentrations of total InsP(3) (9.5 +/- 1.3 (SE) and 10.8 +/- 1.0 (SE) micromol.kg(-1) for MDA-MB 231 and K562 cells respectively, p < 0.05), without changes in InsP(6) levels. These results indicate that exogenous InsP(6) directly affects its physiological levels in plasma and brain of normal rats without changes on the total InsP(3) levels. Although a similar fluctuation of InsP(6) concentration was not seen in human malignant cell lines following InsP(6) treatment, an increased intracellular levels of total InsP(3) was clearly observed.
Collapse
Affiliation(s)
- Felix Grases
- Laboratory of Renal Lithiasis Research, Faculty of Science, University of Balearic Islands, Ctra. Valldemossa Km 7.5, 07071 Palma de Mallorca, Spain.
| | | | | | | | | | | |
Collapse
|
25
|
Campbell S, Fisher RJ, Towler EM, Fox S, Issaq HJ, Wolfe T, Phillips LR, Rein A. Modulation of HIV-like particle assembly in vitro by inositol phosphates. Proc Natl Acad Sci U S A 2001; 98:10875-9. [PMID: 11526217 PMCID: PMC58567 DOI: 10.1073/pnas.191224698] [Citation(s) in RCA: 169] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
HIV-1 Gag protein assembles into 100- to 120-nm diameter particles in mammalian cells. Recombinant HIV-1 Gag protein assembles in a fully defined system in vitro into particles that are only 25-30 nm in diameter and that differ significantly in other respects from authentic particles. However, particles with the size and other properties of authentic virions were obtained in vitro by addition of inositol phosphates or phosphatidylinsitol phosphates to the assembly system. Thus, the interactions between HIV-1 Gag protein molecules are altered by binding of inositol derivatives; this binding is apparently essential for normal HIV-1 particle assembly. This requirement is not seen in a deleted Gag protein lacking residues 16-99 within the matrix domain.
Collapse
Affiliation(s)
- S Campbell
- HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702-1201, USA.
| | | | | | | | | | | | | | | |
Collapse
|
26
|
Caffrey JJ, Darden T, Wenk MR, Shears SB. Expanding coincident signaling by PTEN through its inositol 1,3,4,5,6-pentakisphosphate 3-phosphatase activity. FEBS Lett 2001; 499:6-10. [PMID: 11418101 DOI: 10.1016/s0014-5793(01)02500-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PTEN, a tumor suppressor among the most commonly mutated proteins in human cancer, is recognized to be both a protein phosphatase and a phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P(3)) 3-phosphatase. Previous work [Maehama and Dixon, J. Biol. Chem. 273 (1998) 13375-13378] has led to a consensus that inositol phosphates are not physiologically relevant substrates for PTEN. In contrast, we demonstrate that PTEN is an active inositol 1,3,4,5,6-pentakisphosphate (Ins(1,3,4,5,6)P(5)) 3-phosphatase when expressed and purified from bacteria or HEK cells. Kinetic data indicate Ins(1,3,4,5,6)P(5) (K(m)=7.1 microM) and PtdIns(3,4,5)P(3) (K(m)=26 microM) compete for PTEN in vivo. Transient transfection of HEK cells with PTEN decreased Ins(1,3,4,5,6)P(5) levels. We discuss the physiological significance of these studies in relation to recent work showing that dephosphorylation of Ins(1,3,4,5,6)P(5) to inositol 1,4,5,6-tetrakisphosphate is a cell signaling event.
Collapse
Affiliation(s)
- J J Caffrey
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | | | | | | |
Collapse
|
27
|
Hilton JM, Plomann M, Ritter B, Modregger J, Freeman HN, Falck JR, Krishna UM, Tobin AB. Phosphorylation of a synaptic vesicle-associated protein by an inositol hexakisphosphate-regulated protein kinase. J Biol Chem 2001; 276:16341-7. [PMID: 11278843 DOI: 10.1074/jbc.m011122200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite the fact that inositol hexakisphosphate (InsP(6)) is the most abundant inositol metabolite in cells, its cellular function has remained an enigma. In the present study, we present the first evidence of a protein kinase identified in rat cerebral cortex/hippocampus that is activated by InsP(6). The substrate for the InsP(6)-regulated protein kinase was found to be the synaptic vesicle-associated protein, pacsin/syndapin I. This brain-specific protein, which is highly enriched at nerve terminals, is proposed to act as a molecular link coupling components of the synaptic vesicle endocytic machinery to the cytoskeleton. We show here that the association between pacsin/syndapin I and dynamin I can be increased by InsP(6)-dependent phosphorylation of pacsin/syndapin I. These data provide a model by which InsP(6)-dependent phosphorylation regulates synaptic vesicle recycling by increasing the interaction between endocytic proteins at the synapse.
Collapse
Affiliation(s)
- J M Hilton
- Department of Cell Physiology and Pharmacology, University of Leicester, Medical Sciences Building, University Road, Leicester, LE1 9HN, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
28
|
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.
Collapse
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.
| |
Collapse
|
29
|
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: 53] [Impact Index Per Article: 2.2] [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.
Collapse
Affiliation(s)
- H Chi
- Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
| | | | | | | | | | | | | | | |
Collapse
|
30
|
Aulwurm UR, Brand KA. Increased formation of reactive oxygen species due to glucose depletion in primary cultures of rat thymocytes inhibits proliferation. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:5693-8. [PMID: 10971579 DOI: 10.1046/j.1432-1327.2000.01576.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glycolytic glucose degradation to lactate is the only way of energy production in mammalian cells that does not use oxygen, and is thus a means of reducing oxidative stress. The aim of this work was to study the effect on proliferation of progressive glucose depletion during the cell cycle of stimulated cultured rat thymocytes. It has been shown that under conditions of limited glucose supply, these cells increase the generation of reactive oxygen species. Because of the sensitivity of the stimulating transcription factor Sp1 to redox changes with respect to its DNA binding, gene expression of glycolytic enzymes is markedly suppressed. As a consequence, cell division does not occur in glucose depleted thymocytes.
Collapse
Affiliation(s)
- U R Aulwurm
- Institute of Biochemistry, Medical Faculty, University of Erlangen-Nuremberg, Germany
| | | |
Collapse
|
31
|
Saiardi A, Caffrey JJ, Snyder SH, Shears SB. The inositol hexakisphosphate kinase family. Catalytic flexibility and function in yeast vacuole biogenesis. J Biol Chem 2000; 275:24686-92. [PMID: 10827188 DOI: 10.1074/jbc.m002750200] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Saiardi et al. (Saiardi, A., Erdjument-Bromage, H., Snowman, A., Tempst, P., and Snyder, S. H. (1999) Curr. Biol. 9, 1323-1326) previously described the cloning of a kinase from yeast and two kinases from mammals (types 1 and 2), which phosphorylate inositol hexakisphosphate (InsP(6)) to diphosphoinositol pentakisphosphate, a "high energy" candidate regulator of cellular trafficking. We have now studied the significance of InsP(6) kinase activity in Saccharomyces cerevisiae by disrupting the kinase gene. These ip6kDelta cells grew more slowly, their levels of diphosphoinositol polyphosphates were 60-80% lower than wild-type cells, and the cells contained abnormally small and fragmented vacuoles. Novel activities of the mammalian and yeast InsP(6) kinases were identified; inositol pentakisphosphate (InsP(5)) was phosphorylated to diphosphoinositol tetrakisphosphate (PP-InsP(4)), which was further metabolized to a novel compound, tentatively identified as bis-diphosphoinositol trisphosphate. The latter is a new substrate for human diphosphoinositol polyphosphate phosphohydrolase. Kinetic parameters for the mammalian type 1 kinase indicate that InsP(5) (K(m) = 1.2 micrometer) and InsP(6) (K(m) = 6.7 micrometer) compete for phosphorylation in vivo. This is the first time a PP-InsP(4) synthase has been identified. The mammalian type 2 kinase and the yeast kinase are more specialized for the phosphorylation of InsP(6). Synthesis of the diphosphorylated inositol phosphates is thus revealed to be more complex and interdependent than previously envisaged.
Collapse
Affiliation(s)
- A Saiardi
- Departments of Neuroscience, Pharmacology and Molecular Sciences, and Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | | | |
Collapse
|
32
|
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.
Collapse
Affiliation(s)
- A Rönnbäck
- Department of Pharmacology and Clinical Neuroscience, Umeå University, Sweden
| | | |
Collapse
|
33
|
Li SR, Gyselman VG, Lalude O, Dorudi S, Bustin SA. Transcription of the inositol polyphosphate 1-phosphatase gene (INPP1) is upregulated in human colorectal cancer. Mol Carcinog 2000; 27:322-9. [PMID: 10747296 DOI: 10.1002/(sici)1098-2744(200004)27:4<322::aid-mc10>3.0.co;2-c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We have used suppression subtractive hybridization to demonstrate significant overexpression of the inositol polyphosphate 1-phosphatase gene (INPP1) in colorectal cancer compared with matched normal colon epithelium. Its gene product catalyses the hydrolysis of inositol 1,3,4-trisphosphate and inositol 1, 4-bisphosphate, a key molecule in the phosphoinositide metabolic and signaling pathways. Following confirmation of the differential expression by reverse Northern dot blot analysis, fully quantitative Taqman reverse transcriptase-polymerase chain reaction assays showed that its transcription was upregulated in 42/49 colorectal tumors. There was no significant difference in four tumors and reduced transcription was observed in three. This is the first study to report the upregulation of the INPP1 gene in a human cancer and should facilitate further studies looking at the role of phosphatidylinositol signaling reactions in human colorectal cancer.
Collapse
Affiliation(s)
- S R Li
- Academic Department of Surgery, St Bartholomew's and the Royal London School of Medicine and Dentistry, London, UK
| | | | | | | | | |
Collapse
|
34
|
Hirst PH, Riley AM, Mills SJ, Spiers ID, Poyner DR, Freeman S, Potter BV, Smith AW. Inositol polyphosphate-mediated iron transport in Pseudomonas aeruginosa. J Appl Microbiol 1999; 86:537-43. [PMID: 10196759 DOI: 10.1046/j.1365-2672.1999.00697.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
It has previously been shown that myo-inositol hexakisphosphate (myo-InsP6) mediates iron transport into Pseudomonas aeruginosa and overcomes iron-dependent growth inhibition. In this study, the iron transport properties of myo-inositol trisphosphate and tetrakisphosphate regio-isomers were studied. Pseudomonas aeruginosa accumulated iron (III) at similar rates whether complexed with myo-Ins(1,2,3)P3 or myo-InsP6. Iron accumulation from other compounds, notably D/L myo-Ins(1,2,4,5)P4 and another inositol trisphosphate regio-isomer, D-myo-Ins(1,4,5)P3, was dramatically increased. Iron transport profiles from myo-InsP6 into mutants lacking the outer membrane porins oprF, oprD and oprP were similar to the wild-type, indicating that these porins are not involved in the transport process. The rates of reduction of iron (III) to iron (II) complexed to any of the compounds by a Ps. aeruginosa cell lysate were similar, suggesting that a reductive mechanism is not the rate-determining step.
Collapse
Affiliation(s)
- P H Hirst
- Department of Pharmacy and Pharmacology, University of Bath, UK
| | | | | | | | | | | | | | | |
Collapse
|
35
|
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.
Collapse
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.
| |
Collapse
|
36
|
Bandyopadhyay U, Kaiser T, Rudolf MT, Schultz C, Guse AH, Mayr GW. Vicinal thiols are involved in inositol 1,2,3,5,6-pentakisphosphate 5-phosphatase activity from fetal calf thymus. Biochem Biophys Res Commun 1997; 240:146-9. [PMID: 9367900 DOI: 10.1006/bbrc.1997.7629] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Inositol 1,2,3,5,6-pentakisphosphate (Ins(1,2,3,5,6)P5) 5-phosphatase present in fetal calf thymus has been partially purified. This enzyme was inhibited dose-dependently by different thiol modifiers like N-ethylmaleimide (NEM), p-chloromercuribenzene sulfonate (PCMBS), diamide, and phenylarsine oxide (PAO). The inhibition by PCMBS and diamide was protected by preincubation with dithiothreitol (DTT) and the phosphatase substrate, Ins(1,2,3,5,6)P5. Diamide, a compound that specifically modifies vicinal thiol groups, also blocked the 5-phosphatase dose-dependently. Specificity of this blockade was proven by using dimercaptopropanol (DMP), a compound known to protect vicinal thiol groups. DMP prevented the enzyme from inhibition by diamide. These data suggest that vicinal thiols are involved in Ins(1,2,3,5,6)P5 5-phosphatase activity.
Collapse
|
37
|
Guse AH, Silva CP, Weber K, Ashamu GA, Potter BV, Mayr GW. Regulation of cADP-ribose-induced Ca2+ release by Mg2+ and inorganic phosphate. J Biol Chem 1996; 271:23946-53. [PMID: 8798627 DOI: 10.1074/jbc.271.39.23946] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
cADP-ribose (cADPr) has recently been shown to release Ca2+ from an intracellular store of permeabilized T lymphocyte cell lines (Guse, A. H., da Silva, C. P., Emmrich, F., Ashamu, G. A., Potter, B. V. L., and Mayr, G. W. (1995) J. Immunol. 155, 3353-3359). Using permeabilized Jurkat and HPB. ALL T lymphocytes, the effects of varying concentrations of inorganic phosphate and Mg2+ on cADPr-induced Ca2+ release were investigated. cADPr-induced Ca2+ release was dependent on the concentration of inorganic phosphate, showing very low Ca2+ release activity between 0.5 and 2 mM inorganic phosphate. At 4 to 5 mM inorganic phosphate, the cADPr-induced Ca2+ release was much more pronounced, reaching maximal values at 10 mM inorganic phosphate. The underlying mechanism for this stimulatory effect was an increased loading of the cADPr-sensitive Ca2+ store, which was demonstrated by enhanced resequestration of Ca2+ selectively into the cADPr-sensitive Ca2+ store. The free Mg2+ concentration also influenced cADPr-induced Ca2+ release in permeabilized cells: at 0 and 8.58 mM the release was nearly completely abolished, whereas at 1.06 mM maximal Ca2+ release by cADPr was observed. High performance liquid chromatographic analysis of exogenously added cADPr revealed that the catabolism of cADPr at varying Mg2+ and Pi concentrations had only minor relevance for the modulatory effects observed. To correlate the effects of inorganic phosphate and Mg2+ on cADPr-induced Ca2+ release observed in the permeabilized cell preparations, measurements of these ions in intact Jurkat T lymphocytes were carried out. Intact Jurkat T cells stimulated via the T cell receptor middle dotCD3 complex did not respond with significant elevation of the free intracellular Mg2+ concentration. In contrast, stimulation via the T cell receptor middle dotCD3 complex resulted in an increase in the intracellular inorganic phosphate concentration. These data indicate a role for the intracellular inorganic phosphate concentration in the regulation of cADPr-mediated Ca2+ release in T lymphocytes.
Collapse
Affiliation(s)
- A H Guse
- University of Hamburg, Institute of Physiological Chemistry, Department of Enzyme Chemistry, Grindelallee 117, D-20146 Hamburg, Germany
| | | | | | | | | | | |
Collapse
|
38
|
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.
Collapse
Affiliation(s)
- E Kitchen
- Department of Medicine (RIE), University of Edinburgh
| | | | | | | | | |
Collapse
|
39
|
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
| |
Collapse
|
40
|
Guse AH, Goldwich A, Weber K, Mayr GW. Non-radioactive, isomer-specific inositol phosphate mass determinations: high-performance liquid chromatography-micro-metal-dye detection strongly improves speed and sensitivity of analyses from cells and micro-enzyme assays. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL APPLICATIONS 1995; 672:189-98. [PMID: 8581124 DOI: 10.1016/0378-4347(95)00219-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A microbore high-performance liquid chromatographic (HPLC) method is presented allowing rapid and sensitive mass analysis of inositol phosphates from cells and tissues. An analysis starting from inorganic phosphate up to inositol hexakisphosphate displaying a similar isomer selectivity as compared to the standard metal-dye detection system takes about 15 min. The detection sensitivity was about 15 pmol for inositol trisphosphate, about 10 pmol for inositol tetrakisphosphate, about 5 pmol for inositol pentakisphosphate and less than 5 pmol for inositol hexakisphosphate. The method was validated regarding day-to-day variations and variations at the same day of retention times and peak areas of standard inositol phosphates. Standard deviations of retention times ranged from 0.25 to 0.62% (same day) and from 0.64 to 1.61% (day-to-day variations). Ranges of standard deviations of peak areas were between 2.24% and 3.91% (same day) and 6.13% and 13.8% (day-to-day variations). Linearity of the post-column complexometric metal-dye detection system was demonstrated in the range of a few picomoles and at least 800 pmol. The method was applied to the analysis of inositol phosphates in Jurkat T-lymphocytes and assays from minute amounts of enzymes interconverting inositol phosphates. While measurements of inositol phosphates from cell extracts are now possible using significantly reduced cell numbers, micro-enzyme assays are feasible in reasonable repeated analysis times and with sufficient isomer selectivity. In conclusion, a substantial improvement towards speed of analysis and detection sensitivity of inositol phosphate mass analysis was achieved by microbore metal-dye detection HPLC.
Collapse
Affiliation(s)
- A H Guse
- Abteilung Enzymchemie, Institut für Physiologische Chemie, Universitätskrankenhaus Eppendorf, Hamburg, Germany
| | | | | | | |
Collapse
|
41
|
Hughes PJ, Kirk CJ, Michell RH. Inhibition of porcine brain inositol 1,3,4-trisphosphate kinase by inositol polyphosphates, other polyol phosphates, polyanions and polycations. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1223:57-70. [PMID: 8061054 DOI: 10.1016/0167-4889(94)90073-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We have partially purified an enzyme activity that phosphorylates inositol 1,3,4-trisphosphate from porcine brain, rat liver and bovine testis by FPLC chromatography on Q-Sepharose anion-exchange resin and Heparin-agarose. The products of this reaction were inositol 1,3,4,6-tetrakisphosphate and inositol 1,3,4,5-tetrakisphosphate. The same enzyme appears to be responsible for both 6-kinase and 5-kinase activities against inositol 1,3,4-trisphosphate (the 6-kinase: 5-kinase activity ratio is approximately 4 to 1), has a pH optimum of approximately 6.8 and requires Mg2+ for activity. The Km values of the enzyme for inositol 1,3,4-trisphosphate and ATP were approximately 0.5 microM and approximately 100 microM, respectively. Inositol 3,4,5,6-tetrakisphosphate, inositol 1,3,4,6-tetrakisphosphate and inositol 1,3,4,5-tetrakisphosphate are all competitive inhibitors with K(i) values of 0.4 microM, 3 microM and 5 microM, respectively, well within their likely intracellular concentration ranges: they inhibited 6-kinase and 5-kinase activities equally. 2,3-Bisphosphoglycerate and spermine were also competitive inhibitors, with K(i) values of 0.8 mM an 12 mM, respectively. Dextran sulphate was a non-competitive inhibitor with a Ki of approximately 15 microM, and poly-L-lysine (IC50 approximately 200 microM), polyvinylsulphate (IC50 approximately 250 microM) and heparin (IC50 approximately 2 mg/ml) also inhibited. Inhibition by these compounds suggests that inositol 3,4,5,6-tetrakisphosphate (and to a lesser extent inositol 1,3,4,5-tetrakisphosphate and other naturally occurring intracellular ions) may restrict the synthesis of inositol 1,3,4,6-tetrakisphosphate and hence regulate the rate of inositol penta- and hexakisphosphate synthesis from receptor-generated inositol phosphates.
Collapse
Affiliation(s)
- P J Hughes
- Centre for Clinical Research in Immunology and Signalling, University of Birmingham, UK
| | | | | |
Collapse
|
42
|
Mountford JC, Bunce CM, French PJ, Michell RH, Brown G. Intracellular concentrations of inositol, glycerophosphoinositol and inositol pentakisphosphate increase during haemopoietic cell differentiation. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1222:101-8. [PMID: 7514443 DOI: 10.1016/0167-4889(94)90030-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We have analysed the levels of soluble inositol metabolites in HL60 cells as they differentiate towards neutrophils in response to a combination of all-trans-retinoic acid and granulocyte colony-stimulating factor and towards monocytes in response to 1 alpha-25-dihydroxyvitamin D3. In both cases, differentiation was accompanied by increases in intracellular inositol (Ins), glycerophosphoinositol (GroPIns) and inositol pentakisphosphate (InsP5) concentrations. [GroPIns] reached a peak early in the differentiation of both neutrophils and monocytes and subsequently fell to about double the starting level as the cells acquired mature characteristics, and [InsP5] rose later. Similarly, neutrophils derived in culture by the spontaneous differentiation of myeloid blast cells contained increased levels of Ins, GroPIns and InsP5 when compared to their parental blast cells. We have also compared the inositol metabolites present in two pairs of cell lines which are representative of immature and mature B and T lymphocytes. The mature cells again contained the higher levels of GroPIns and InsP5. We have previously demonstrated increases in Ins, GroPIns and Ins(1,3,4,5,6)P5 levels during the differentiation of HL60 cells towards neutrophils in response to DMSO and of GroPIns during the monocytoid differentiation of normal primitive myeloid blast cells in response to PMA. These observations suggest that deacylation of phosphatidylinositol by a phospholipase A/lysophospholipase pathway, forming GroPIns and probably also regulatory arachidonate metabolites, has some role in haemopoietic cell differentiation. The reasons why Ins(1,3,4,5,6)P5 and Ins accumulate during haemopoietic differentiation remain unknown.
Collapse
Affiliation(s)
- J C Mountford
- Department of Immunology, University of Birmingham, Edgbaston, UK
| | | | | | | | | |
Collapse
|