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Márquez-Moñino MÁ, Ortega-García R, Whitfield H, Riley AM, Infantes L, Garrett SW, Shipton ML, Brearley CA, Potter BVL, González B. Substrate promiscuity of inositol 1,4,5-trisphosphate kinase driven by structurally-modified ligands and active site plasticity. Nat Commun 2024; 15:1502. [PMID: 38374076 PMCID: PMC10876669 DOI: 10.1038/s41467-024-45917-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Accepted: 02/05/2024] [Indexed: 02/21/2024] Open
Abstract
D-myo-inositol 1,4,5-trisphosphate (InsP3) is a fundamental second messenger in cellular Ca2+ mobilization. InsP3 3-kinase, a highly specific enzyme binding InsP3 in just one mode, phosphorylates InsP3 specifically at its secondary 3-hydroxyl group to generate a tetrakisphosphate. Using a chemical biology approach with both synthetised and established ligands, combining synthesis, crystallography, computational docking, HPLC and fluorescence polarization binding assays using fluorescently-tagged InsP3, we have surveyed the limits of InsP3 3-kinase ligand specificity and uncovered surprisingly unforeseen biosynthetic capacity. Structurally-modified ligands exploit active site plasticity generating a helix-tilt. These facilitated uncovering of unexpected substrates phosphorylated at a surrogate extended primary hydroxyl at the inositol pseudo 3-position, applicable even to carbohydrate-based substrates. Crystallization experiments designed to allow reactions to proceed in situ facilitated unequivocal characterization of the atypical tetrakisphosphate products. In summary, we define features of InsP3 3-kinase plasticity and substrate tolerance that may be more widely exploitable.
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Affiliation(s)
- María Ángeles Márquez-Moñino
- Department of Crystallography and Structural Biology, Institute of Physical-Chemistry Blas Cabrera, CSIC, Serrano 119, 28006, Madrid, Spain
| | - Raquel Ortega-García
- Department of Crystallography and Structural Biology, Institute of Physical-Chemistry Blas Cabrera, CSIC, Serrano 119, 28006, Madrid, Spain
| | - Hayley Whitfield
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Andrew M Riley
- Drug Discovery and Medicinal Chemistry, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK
| | - Lourdes Infantes
- Department of Crystallography and Structural Biology, Institute of Physical-Chemistry Blas Cabrera, CSIC, Serrano 119, 28006, Madrid, Spain
| | - Shane W Garrett
- Wolfson Laboratory of Medicinal Chemistry, Department of Life Sciences, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Megan L Shipton
- Drug Discovery and Medicinal Chemistry, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK
| | - Charles A Brearley
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Barry V L Potter
- Drug Discovery and Medicinal Chemistry, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK.
- Wolfson Laboratory of Medicinal Chemistry, Department of Life Sciences, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
| | - Beatriz González
- Department of Crystallography and Structural Biology, Institute of Physical-Chemistry Blas Cabrera, CSIC, Serrano 119, 28006, Madrid, Spain.
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2
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Della-Felice F, de Andrade Bartolomeu A, Pilli RA. The phosphate ester group in secondary metabolites. Nat Prod Rep 2022; 39:1066-1107. [PMID: 35420073 DOI: 10.1039/d1np00078k] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Covering: 2000 to mid-2021The phosphate ester is a versatile, widespread functional group involved in a plethora of biological activities. Its presence in secondary metabolites, however, is relatively rare compared to other functionalities and thus is part of a rather unexplored chemical space. Herein, the chemistry of secondary metabolites containing the phosphate ester group is discussed. The text emphasizes their structural diversity, biological and pharmacological profiles, and synthetic approaches employed in the phosphorylation step during total synthesis campaigns, covering the literature from 2000 to mid-2021.
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Affiliation(s)
- Franco Della-Felice
- Institute of Chemistry, University of Campinas (UNICAMP), P.O. Box 6154, CEP 13083-970 Campinas, Sao Paulo, Brazil.,Institute of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology, Av. Països Catalans 16, 43007 Tarragona, Spain.
| | | | - Ronaldo Aloise Pilli
- Institute of Chemistry, University of Campinas (UNICAMP), P.O. Box 6154, CEP 13083-970 Campinas, Sao Paulo, Brazil
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3
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Mechanism of BIP-4 mediated inhibition of InsP3Kinase-A. Biosci Rep 2021; 41:229216. [PMID: 34232294 PMCID: PMC8292763 DOI: 10.1042/bsr20211259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 07/02/2021] [Accepted: 07/02/2021] [Indexed: 11/17/2022] Open
Abstract
Overexpression of the neuronal InsP3kinase-A increases malignancy of different tumor types. Since InsP3kinase-A highly selectively binds Ins(1,4,5)P3, small molecules competing with Ins(1,4,5)P3 provide a promising approach for the therapeutic targeting of InsP3kinase-A. Based on this consideration, we analyzed the binding mechanism of BIP-4 (2-[3,5-dimethyl-1-(4-nitrophenyl)-1H-pyrazol-4-yl]-5, 8-dinitro-1H-benzo[de]isoquinoline-1,3(2H)-dione), a known competitive small-molecule inhibitor of Ins(1,4,5)P3. We tested a total of 80 BIP-4 related compounds in biochemical assays. The results of these experiments revealed that neither the nitrophenyl nor the benzisochinoline group inhibited InsP3kinase-A activity. Moreover, none of the BIP-4 related compounds competed for Ins(1,4,5)P3, demonstrating the high selectivity of BIP-4. To analyze the inhibition mechanism of BIP-4, mutagenesis experiments were performed. The results of these experiments suggest that the nitro groups attached to the benzisochinoline ring compete for binding of Ins(1,4,5)P3 while the nitrophenyl group is associated with amino acids of the ATP-binding pocket. Our results now offer the possibility to optimize BIP-4 to design specific InsP3Kinase-A inhibitors suitable for therapeutic targeting of the enzyme.
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4
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Elich M, Sauer K. Regulation of Hematopoietic Cell Development and Function Through Phosphoinositides. Front Immunol 2018; 9:931. [PMID: 29780388 PMCID: PMC5945867 DOI: 10.3389/fimmu.2018.00931] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 04/16/2018] [Indexed: 01/01/2023] Open
Abstract
One of the most paramount receptor-induced signal transduction mechanisms in hematopoietic cells is production of the lipid second messenger phosphatidylinositol(3,4,5)trisphosphate (PIP3) by class I phosphoinositide 3 kinases (PI3K). Defective PIP3 signaling impairs almost every aspect of hematopoiesis, including T cell development and function. Limiting PIP3 signaling is particularly important, because excessive PIP3 function in lymphocytes can transform them and cause blood cancers. Here, we review the key functions of PIP3 and related phosphoinositides in hematopoietic cells, with a special focus on those mechanisms dampening PIP3 production, turnover, or function. Recent studies have shown that beyond “canonical” turnover by the PIP3 phosphatases and tumor suppressors phosphatase and tensin homolog (PTEN) and SH2 domain-containing inositol-5-phosphatase-1 (SHIP-1/2), PIP3 function in hematopoietic cells can also be dampened through antagonism with the soluble PIP3 analogs inositol(1,3,4,5)tetrakisphosphate (IP4) and inositol-heptakisphosphate (IP7). Other evidence suggests that IP4 can promote PIP3 function in thymocytes. Moreover, IP4 or the kinases producing it limit store-operated Ca2+ entry through Orai channels in B cells, T cells, and neutrophils to control cell survival and function. We discuss current models for how soluble inositol phosphates can have such diverse functions and can govern as distinct processes as hematopoietic stem cell homeostasis, neutrophil macrophage and NK cell function, and development and function of B cells and T cells. Finally, we will review the pathological consequences of dysregulated IP4 activity in immune cells and highlight contributions of impaired inositol phosphate functions in disorders such as Kawasaki disease, common variable immunodeficiency, or blood cancer.
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Affiliation(s)
- Mila Elich
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA, United States
| | - Karsten Sauer
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA, United States.,Oncology R&D, Pfizer Worldwide R&D, San Diego, CA, United States
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5
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Peng Z, Maxwell D, Sun D, Ying Y, Schuber PT, Bhanu Prasad BA, Gelovani J, Yung WKA, Bornmann WG. Design and Synthesis of an Inositol Phosphate Analog Based on Computational Docking Studies. Tetrahedron 2014; 70:984-990. [PMID: 25110363 DOI: 10.1016/j.tet.2013.11.092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A virtual library of 54 inositol analog mimics of In(1,4,5)P3 has been docked, scored, and ranked within the binding site of human inositol 1,4,5-trisphosphate 3-kinase A (IP3-3KA). Chemical synthesis of the best scoring structure that also met distance criteria for 3'-OH to -P in Phosphate has been attempted along with the synthesis of (1S,2R,3S,4S)-3-fluoro-2,4-dihydroxycyclohexanecarboxylic acid as an inositol analog, useful for non-invasive visualization and quantitation of IP3-3KA enzymatic activity.
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Affiliation(s)
- Zhenghong Peng
- Department of Experimental Therapeutics, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd. Box 603, Houston, TX 77030, USA
| | - David Maxwell
- Department of Experimental Therapeutics, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd. Box 603, Houston, TX 77030, USA
| | - Duoli Sun
- Department of Experimental Therapeutics, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd. Box 603, Houston, TX 77030, USA
| | - Yunming Ying
- Department of Experimental Diagnostic Imaging, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd. Box 603, Houston, TX 77030, USA
| | - Paul T Schuber
- Department of Experimental Therapeutics, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd. Box 603, Houston, TX 77030, USA
| | - Basvoju A Bhanu Prasad
- Department of Experimental Therapeutics, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd. Box 603, Houston, TX 77030, USA
| | - Juri Gelovani
- Department of Experimental Diagnostic Imaging, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd. Box 603, Houston, TX 77030, USA
| | - Wai-Kwan Alfred Yung
- Department of Experimental Diagnostic Imaging, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd. Box 603, Houston, TX 77030, USA
| | - William G Bornmann
- Department of Experimental Therapeutics, University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd. Box 603, Houston, TX 77030, USA
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6
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Saleem H, Tovey SC, Rahman T, Riley AM, Potter BVL, Taylor CW. Stimulation of inositol 1,4,5-trisphosphate (IP3) receptor subtypes by analogues of IP3. PLoS One 2013; 8:e54877. [PMID: 23372785 PMCID: PMC3556037 DOI: 10.1371/journal.pone.0054877] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 12/17/2012] [Indexed: 11/19/2022] Open
Abstract
Most animal cells express mixtures of the three subtypes of inositol 1,4,5-trisphosphate receptor (IP(3)R) encoded by vertebrate genomes. Activation of each subtype by different agonists has not hitherto been examined in cells expressing defined homogenous populations of IP(3)R. Here we measure Ca(2+) release evoked by synthetic analogues of IP(3) using a Ca(2+) indicator within the lumen of the endoplasmic reticulum of permeabilized DT40 cells stably expressing single subtypes of mammalian IP(3)R. Phosphorylation of (1,4,5)IP(3) to (1,3,4,5)IP(4) reduced potency by ~100-fold. Relative to (1,4,5)IP(3), the potencies of IP(3) analogues modified at the 1-position (malachite green (1,4,5)IP(3)), 2-position (2-deoxy(1,4,5)IP(3)) or 3-position (3-deoxy(1,4,5)IP(3), (1,3,4,5)IP(4)) were similar for each IP(3)R subtype. The potency of an analogue, (1,4,6)IP(3), in which the orientations of the 2- and 3-hydroxyl groups were inverted, was also reduced similarly for all three IP(3)R subtypes. Most analogues of IP(3) interact similarly with the three IP(3)R subtypes, but the decrease in potency accompanying removal of the 1-phosphate from (1,4,5)IP(3) was least for IP(3)R3. Addition of a large chromophore (malachite green) to the 1-phosphate of (1,4,5)IP(3) only modestly reduced potency suggesting that similar analogues could be used to measure (1,4,5)IP(3) binding optically. These data provide the first structure-activity analyses of key IP(3) analogues using homogenous populations of each mammalian IP(3)R subtype. They demonstrate broadly similar structure-activity relationships for all mammalian IP(3)R subtypes and establish the potential utility of (1,4,5)IP(3) analogues with chromophores attached to the 1-position.
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MESH Headings
- Amino Acid Sequence
- Animals
- Calcium/metabolism
- Cell Line
- Gene Expression
- Inositol 1,4,5-Trisphosphate/chemistry
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors/chemistry
- Inositol 1,4,5-Trisphosphate Receptors/genetics
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Kinetics
- Ligands
- Mice
- Models, Molecular
- Molecular Docking Simulation
- Molecular Sequence Data
- Molecular Structure
- Protein Binding
- Rats
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Structure-Activity Relationship
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Affiliation(s)
- Huma Saleem
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Stephen C. Tovey
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Taufiq Rahman
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Andrew M. Riley
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom
| | - Barry V. L. Potter
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom
| | - Colin W. Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
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7
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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.
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Affiliation(s)
- Karsten Sauer
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92037, USA.
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8
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Best MD, Zhang H, Prestwich GD. Inositol polyphosphates, diphosphoinositol polyphosphates and phosphatidylinositol polyphosphate lipids: Structure, synthesis, and development of probes for studying biological activity. Nat Prod Rep 2010; 27:1403-30. [DOI: 10.1039/b923844c] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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9
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Rossi AM, Riley AM, Tovey SC, Taufiq-Ur-Rahman, Dellis O, Taylor EJA, Veresov VG, Potter BVL, Taylor CW. Synthetic partial agonists reveal key steps in IP3 receptor activation. Nat Chem Biol 2009; 5:631-9. [PMID: 19668195 PMCID: PMC2869033 DOI: 10.1038/nchembio.195] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Accepted: 05/28/2009] [Indexed: 11/10/2022]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP(3)Rs) are ubiquitous intracellular Ca2+ channels. IP(3) binding to the IP(3)-binding core (IBC) near the N terminus initiates conformational changes that lead to opening of a pore. The mechanisms underlying this process are unresolved. We synthesized 2-O-modified IP(3) analogs that are partial agonists of IP(3)R. These are similar to IP(3) in their interactions with the IBC, but they are less effective than IP(3) in rearranging the relationship between the IBC and the N-terminal suppressor domain (SD), and they open the channel at slower rates. IP(3)R with a mutation in the SD occupying a position similar to the 2-O substituent of the partial agonists has a reduced open probability that is similar for full and partial agonists. Bulky or charged substituents from either the ligand or the SD therefore block obligatory coupling of the IBC and the SD. Analysis of DeltaG for ligand binding shows that IP(3) is recognized by the IBC and conformational changes then propagate entirely via the SD to the pore.
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Affiliation(s)
- Ana M. Rossi
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Andrew M. Riley
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Stephen C. Tovey
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Taufiq-Ur-Rahman
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Olivier Dellis
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Emily J. A. Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Valery G. Veresov
- Department of Cell Biophysics, Institute of Biophysics and Cell Engineering, Minsk 220072, Academicheskaya St. 27, Belarus
| | - Barry V. L. Potter
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Colin W. Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
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10
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Padmanabhan U, Dollins DE, Fridy PC, York JD, Downes CP. Characterization of a selective inhibitor of inositol hexakisphosphate kinases: use in defining biological roles and metabolic relationships of inositol pyrophosphates. J Biol Chem 2009; 284:10571-82. [PMID: 19208622 DOI: 10.1074/jbc.m900752200] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inositol hexakisphosphate kinases (IP6Ks) phosphorylate inositol hexakisphosphate (InsP(6)) to yield 5-diphosphoinositol pentakisphosphate (5-[PP]-InsP(5) or InsP(7)). In this study, we report the characterization of a selective inhibitor, N(2)-(m-(trifluoromethy)lbenzyl) N(6)-(p-nitrobenzyl)purine (TNP), for these enzymes. TNP dose-dependently and selectively inhibited the activity of IP6K in vitro and inhibited InsP(7) and InsP(8) synthesis in vivo without affecting levels of other inositol phosphates. TNP did not inhibit either human or yeast Vip/PPIP5K, a newly described InsP(6)/InsP(7) 1/3-kinase. Overexpression of IP6K1, -2, or -3 in cells rescued TNP inhibition of InsP(7) synthesis. TNP had no effect on the activity of a large number of protein kinases, suggesting that it is selective for IP6Ks. TNP reversibly reduced InsP(7)/InsP(8) levels. TNP in combination with genetic studies was used to implicate the involvement of two pathways for synthesis of InsP(8) in yeast. TNP induced a fragmented vacuole phenotype in yeast, consistent with inhibition of Kcs1, a Saccharomyces cerevisiae IP6K. In addition, it also inhibited insulin release from Min6 cells in a dose-dependent manner further implicating InsP(7) in this process. TNP thus provides a means of selectively and rapidly modulating cellular InsP(7) levels, providing a new and versatile tool to study the biological function and metabolic relationships of inositol pyrophosphates.
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Affiliation(s)
- Usha Padmanabhan
- Division of Molecular Physiology, James Black Centre, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
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11
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Caddick SEK, Harrison CJ, Stavridou I, Mitchell JL, Hemmings AM, Brearley CA. A Solanum tuberosum inositol phosphate kinase (StITPK1) displaying inositol phosphate-inositol phosphate and inositol phosphate-ADP phosphotransferase activities. FEBS Lett 2008; 582:1731-7. [PMID: 18442482 DOI: 10.1016/j.febslet.2008.04.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 04/10/2008] [Accepted: 04/10/2008] [Indexed: 10/22/2022]
Abstract
We describe a multifunctional inositol polyphosphate kinase/phosphotransferase from Solanum tuberosum, StITPKalpha (GenBank accession number: EF362784), hereafter called StITPK1. StITPK1 displays inositol 3,4,5,6-tetrakisphosphate 1-kinase activity: K(m) = 27 microM, and V(max) = 19 nmol min(-1) mg(-1). The enzyme displays inositol 1,3,4,5,6-pentakisphosphate 1-phosphatase activity in the absence of a nucleotide acceptor and inositol 1,3,4,5,6-pentakisphosphate-ADP phosphotransferase activity in the presence of physiological concentrations of ADP. Additionally, StITPK1 shows inositol phosphate-inositol phosphate phosphotransferase activity. Homology modelling provides a structural rationale of the catalytic abilities of StITPK1. Inter-substrate transfer of phosphate groups between inositol phosphates is an evolutionarily conserved function of enzymes of this class.
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Affiliation(s)
- Samuel E K Caddick
- School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK
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12
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Vandeput F, Combettes L, Mills SJ, Backers K, Wohlkönig A, Parys JB, De Smedt H, Missiaen L, Dupont G, Potter BVL, Erneux C. Biphenyl 2,3′,4,5′,6‐pentakisphosphate, a novel inositol polyphosphate surrogate, modulates Ca2+responses in rat hepatocytes. FASEB J 2007; 21:1481-91. [PMID: 17264160 DOI: 10.1096/fj.06-7691com] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Benzene polyphosphates containing phosphate groups on one ring are Ins(1,4,5)P3 5-phosphatase inhibitors when evaluated against type-I Ins(1,4,5)P3 5-phosphatase. A novel biphenyl derivative, biphenyl 2,3',4,5',6-pentakisphosphate, with five phosphate groups on two rings was synthesized: It inhibited the activity of two inositol 5-phosphatases: type I and SHIP2 with Ins(1,3,4,5)P4 as substrate. The inhibition was competitive with respect to the substrate. IC50 value measured in rat hepatocytes, which contains the native Ins(1,4,5)P3 5-phosphatase, was in the micromolar range at 1.0 microM Ins(1,4,5)P3 as substrate. Biphenyl 2,3',4,5',6-pentakisphosphate did not affect the activity of Ins(1,4,5)P3 3-kinase A in the 5-100 microM range. Surprisingly, experimental evidence supports an effect of biphenyl 2,3',4,5',6-pentakisphosphate at the level of the Ins(1,4,5)P3 receptor. Finally, when injected into rat hepatocytes, the analog affected the frequency of Ca2+ oscillations in a positive or negative way depending on its concentration. At very high concentrations of the analog, Ca2+ oscillations were even suppressed. These data were interpreted as a dual effect of the biphenyl 2,3',4,5',6-pentakisphosphate on cytosolic [Ca2+] increases: an activation effect through an increase in Ins(1,4,5)P3 level via Ins(1,4,5)P3 5-phosphatase inhibition and an inhibitory effect, which was exerted directly on the Ins(1,4,5)P3 receptor. Thus, our data show for the first time that the frequency of Ca2+ oscillations in response to a Ca2+-mobilizing agonist can be controlled by inhibitors of type-I Ins(1,4,5)P3 5-phosphatase.
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Affiliation(s)
- Fabrice Vandeput
- Institut de Recherche Interdisciplinaire (IRIBHM), Université Libre de Bruxelles, Campus Erasme, 808 Route de Lennik, 1070 Brussels, Belgium
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