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Walker SA, Kupzig S, Lockyer PJ, Bilu S, Zharhary D, Cullen PJ. Analyzing the role of the putative inositol 1,3,4,5-tetrakisphosphate receptor GAP1IP4BP in intracellular Ca2+ homeostasis. J Biol Chem 2002; 277:48779-85. [PMID: 12356770 DOI: 10.1074/jbc.m204839200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inositol 1,3,4,5-tetrakisphosphate (IP(4)) has been linked to a potential role in the regulation of intracellular free Ca(2+) concentration ([Ca(2+)](i)) following cellular stimulation with agonists that activate phosphoinositide-specific phospholipase C. However, despite many studies, the function of IP(4) remains unclear and indeed there is still some debate over whether it has a function at all. Here we have used various molecular approaches to address whether manipulation of the potential IP(4) receptor, GAP1(IP4BP), affects [Ca(2+)](i) following cellular stimulation. Using single cell imaging, we show that the overexpression of a constitutively active and a potential dominant negative form of GAP1(IP4BP) appear to have no effect on Ca(2+) mobilization or Ca(2+) entry following stimulation of HeLa cells with histamine. In addition, through the use of small interfering RNA duplexes, we have examined the effect of suppressing endogenous GAP1(IP4BP) production on [Ca(2+)](i). In HeLa cells in which the endogenous level of GAP1(IP4BP) has been suppressed by approximately 95%, we failed to observe any effect on Ca(2+) mobilization or Ca(2+) entry following histamine stimulation. Thus, using various approaches to manipulate the function of endogenous GAP1(IP4BP) in intact HeLa cells, we have been unable to observe any detectable effect of GAP1(IP4BP) on [Ca(2+)](i).
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Affiliation(s)
- Simon A Walker
- Department of Biochemistry, Inositide Group, Integrated Signalling Laboratories, School of Medical Sciences, University of Bristol, United Kingdom
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2
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Chung SK, Kwon YU, Shin JH, Chang YT, Lee C, Shin BG, Kim KC, Kim MJ. Divergent syntheses of all possible optically active regioisomers of myo-inositol tris- and tetrakisphosphates. J Org Chem 2002; 67:5626-37. [PMID: 12153261 DOI: 10.1021/jo0257694] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Since the discovery of D-myo-inositol 1,4,5-trisphosphate, which plays a pivotal role as a second messenger in transmembrane signaling, the scope of the phosphoinositide-based signaling processes has been continually expanding. However, the clear understanding of the molecular signal transduction mechanisms including the functions of newly found IP(n) is still lacking. As a continuing effort to our previously reported syntheses of all possible 39 optically inactive regioisomers of myo-inositol phosphates (IP(n); n = 1-6), we synthesized all possible optically active regioisomers of myo-IP(3) and myo-IP(4) using chiral IBz(3)s and IBz(2)s, respectively. A series of procedures involving CRL-catalyzed enzymatic resolution of racemic 1,2:5,6-di-O-isopropylidene-myo-inositol and base-catalyzed benzoyl migration in tri- and dibenzoyl-isopropylidene-myo-inositol afforded eight enantiomeric pairs of IBz(3) and six enantiomeric pairs of IBz(2), respectively. Phosphorylation of these intermediates by the phosphitylation and oxidation procedure gave the target products.
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Affiliation(s)
- Sung-Kee Chung
- Department of Chemistry, Division of Molecular and Life Sciences, Pohang University of Science & Technology, Pohang 790-784, South Korea.
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3
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Kwon YU, Lee C, Chung SK. Facile syntheses of all possible diastereomers of conduritol and various derivatives of inositol stereoisomers in high enantiopurity from myo-inositol. J Org Chem 2002; 67:3327-38. [PMID: 12003543 DOI: 10.1021/jo016237a] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphoinositide-based signaling processes are crucially important in intracellular signal transduction events. Inositol phosphate analogues have been useful in probing the structure-activity relationships between inositol phosphates and biomacromolecules, and in studying biological functions of newly found inositol phosphates. Thus, a systematic and ready access to inositol stereoisomers is highly desirable. And practical and convenient syntheses of conduritols and related compounds are also important because of their biological activities and their synthetic utilities in the preparation of other bioactive molecules. We herein report the first syntheses of all possible diastereomers of conduritol and various derivatives of eight inositol stereoisomers in high enantiopurity from myo-inositol, which involve efficient enzymatic resolution of the intermediates conduritol B and C derivatives, followed by oxidation-reduction or the Mitsunobu reaction, and cis-dihydroxylation in stereo- and regioselective manners.
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Affiliation(s)
- Yong-Uk Kwon
- Department of Chemistry, Division of Molecular and Life Sciences, Pohang University of Science & Technology, Pohang 790-784, South Korea
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4
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Horne G, Potter BV. Synthesis of the enantiomers of 6-deoxy-myo-inositol 1,3,4,5-tetrakisphosphate, structural analogues of myo-inositol 1,3,4,5-tetrakisphosphate. Chemistry 2001; 7:80-7. [PMID: 11205029 DOI: 10.1002/1521-3765(20010105)7:1<80::aid-chem80>3.0.co;2-b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
D-myo-Inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4] is produced rapidly from the established second messenger D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P4] in stimulated cells. Despite extensive investigations, in particular concerning its potential role in mediating cellular Ca2+ influx, no exact cellular function has been described for this inositol phosphate; however, binding sites have been identified in a number of tissues and it has been shown to act synergistically with Ins(1,4,5)P3. To assist in the elucidation of the mechanism of action and structural requirements within the Ins(1,3,4,5)P4 moiety that are necessary for recognition and activation of the receptor, structural analogues of this tetrakisphosphate are required. Routes for the synthesis of racemic 6-deoxy-myo-inositol 1,3,4,5-tetrakisphosphate [6-deoxy-DL-Ins(1,3,4,5)P4] and the chiral antipodes D- and L-6-deoxy-myo-inositol 1,3,4,5-tetrakisphosphate are described here. The racemic tetrakisphosphate was synthesised from DL-1,2-O-isopropylidene-myo-inositol in eight steps. Deoxygenation at C-6 was achieved following the Barton-McCombie procedure. Both chiral tetrakisphosphates were synthesised through resolution of racemic cis-diol 6-deoxy-1,4,5-tri-O-p-methoxybenzyl-myo-inositol with the chiral auxiliary (S)-(+)-O-acetylmandelic acid. Absolute configuration was confirmed by synthesis of the known D-6-deoxy-myo-inositol. Both D-6-deoxy-Ins(1,3,4,5)P4 and its enantiomer will be useful tools to unravel the enigmatic role of Ins(1,3,4,5)P4 in the polyphosphoinositide pathway of signal transduction.
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Affiliation(s)
- G Horne
- Department of Pharmacy and Pharmacology, University of Bath, UK
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5
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Ferguson KM, Kavran JM, Sankaran VG, Fournier E, Isakoff SJ, Skolnik EY, Lemmon MA. Structural basis for discrimination of 3-phosphoinositides by pleckstrin homology domains. Mol Cell 2000; 6:373-84. [PMID: 10983984 DOI: 10.1016/s1097-2765(00)00037-x] [Citation(s) in RCA: 287] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Pleckstrin homology (PH) domains are protein modules of around 120 amino acids found in many proteins involved in cellular signaling. Certain PH domains drive signal-dependent membrane recruitment of their host proteins by binding strongly and specifically to lipid second messengers produced by agonist-stimulated phosphoinositide 3-kinases (PI 3-Ks). We describe X-ray crystal structures of two different PH domains bound to Ins(1,3,4,5)P4, the head group of the major PI 3-K product PtdIns(3,4,5)P3. One of these PH domains (from Grp1) is PtdIns(3,4,5)P3 specific, while the other (from DAPP1/PHISH) binds strongly to both PtdIns(3,4,5)P3 and its 5'-dephosphorylation product, PtdIns(3,4)P2. Comparison of the two structures provides an explanation for the distinct phosphoinositide specificities of the two PH domains and allows us to predict the 3-phosphoinositide selectivity of uncharacterized PH domains.
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Affiliation(s)
- K M Ferguson
- Department of Biochemistry and Biophysics and The Johnson Foundation, University of Pennsylvania School of Medicine, Philadelphia 19104, USA
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6
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Cozier G, Sessions R, Bottomley JR, Reynolds JS, Cullen PJ. Molecular modelling and site-directed mutagenesis of the inositol 1,3,4,5-tetrakisphosphate-binding pleckstrin homology domain from the Ras GTPase-activating protein GAP1IP4BP. Biochem J 2000; 349:333-42. [PMID: 10861245 PMCID: PMC1221154 DOI: 10.1042/0264-6021:3490333] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
GAP1(IP4BP) is a Ras GTPase-activating protein (GAP) that in vitro is regulated by the cytosolic second messenger inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P(4)]. We have studied Ins(1,3,4,5)P(4) binding to GAP1(IP4BP), and shown that the inositol phosphate specificity and binding affinity are similar to Ins(1,3,4,5)P(4) binding to Bruton's tyrosine kinase (Btk), evidence which suggests a similar mechanism for Ins(1,3,4,5)P(4) binding. The crystal structure of the Btk pleckstrin homology (PH) domain in complex with Ins(1,3,4,5)P(4) has shown that the binding site is located in a partially buried pocket between the beta 1/beta 2- and beta 3/beta 4-loops. Many of the residues involved in the binding are conserved in GAP1(IP4BP). Therefore we generated a model of the PH domain of GAP1(IP4BP) in complex with Ins(1,3,4,5)P(4) based on the Btk-Ins(1,3,4,5)P(4) complex crystal structure. This model had the typical PH domain fold, with the proposed binding site modelling well on the Btk structure. The model has been verified by site-directed mutagenesis of various residues in and around the proposed binding site. These mutations have markedly reduced affinity for Ins(1,3,4,5)P(4), indicating a specific and tight fit for the substrate. The model can also be used to explain the specificity of inositol phosphate binding.
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Affiliation(s)
- G Cozier
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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7
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Chung SK, Kwon YU, Chang YT, Sohn KH, Shin JH, Park KH, Hong BJ, Chung IH. Synthesis of all possible regioisomers of scyllo-inositol phosphate. Bioorg Med Chem 1999; 7:2577-89. [PMID: 10632068 DOI: 10.1016/s0968-0896(99)00183-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
scyllo-Inositol is the all equatorial stereoisomer of myo-inositol. All possible 12 regioisomers of scyllo-inositol phosphate were synthesized for the first time via a scyllo-inositol benzoate intermediate, which was derived from a myo-inositol derivative. The stereoinversion of myo-inositol into scyllo-inositol was accomplished by Mitsunobu reaction of the vicinal cis-diol. The requisite intermediates, scyllo-inositol benzoates were obtained by benzoyl migration or random benzoylation, and phosphorylated to give scyllo-IPn.
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Affiliation(s)
- S K Chung
- Department of Chemistry, Pohang University of Science and Technology, South Korea.
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8
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Abstract
Synthesis of six inositol stereoisomers was successfully carried out via conduritol intermediates prepared from myo-inositol. Dihydroxylation and epoxidation followed by ring opening of the conduritol B, C and F derivatives gave epi-, allo-, muco-, neo-, DL-chiro- and scyllo-inositol. The cis-inositol derivative, which may not be prepared by this approach, was synthesized in 5 steps via 2-O-benzoyl-myo-inositol orthoformate as the key intermediate.
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Affiliation(s)
- S K Chung
- Department of Chemistry, Pohang University of Science & Technology, Korea
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9
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Stereoselective synthesis of myo-inositol-1,3,4,5-tetrakisphosphate analogues from 6-deoxy d-inositol precursors. Tetrahedron 1999. [DOI: 10.1016/s0040-4020(99)00366-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Cullen PJ. Bridging the GAP in inositol 1,3,4,5-tetrakisphosphate signalling. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1436:35-47. [PMID: 9838034 DOI: 10.1016/s0005-2760(98)00149-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- P J Cullen
- Lister Institute Research Fellow, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.
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11
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Kavran JM, Klein DE, Lee A, Falasca M, Isakoff SJ, Skolnik EY, Lemmon MA. Specificity and promiscuity in phosphoinositide binding by pleckstrin homology domains. J Biol Chem 1998; 273:30497-508. [PMID: 9804818 DOI: 10.1074/jbc.273.46.30497] [Citation(s) in RCA: 358] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Pleckstrin homology (PH) domains are small protein modules involved in recruitment of signaling molecules to cellular membranes, in some cases by binding specific phosphoinositides. We describe use of a convenient "dot-blot" approach to screen 10 different PH domains for those that recognize particular phosphoinositides. Each PH domain bound phosphoinositides in the assay, but only two (from phospholipase C-delta1 and Grp1) showed clear specificity for a single species. Using soluble inositol phosphates, we show that the Grp1 PH domain (originally cloned on the basis of its phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) binding) binds specifically to D-myo-inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4) (the PtdIns(3,4,5)P3 headgroup) with KD = 27.3 nM, but binds D-myo-inositol 1,3,4-trisphosphate (Ins(1,3,4)P3) or D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) over 80-fold more weakly. We show that this specificity allows localization of the Grp1 PH domain to the plasma membrane of mammalian cells only when phosphatidylinositol 3-kinase (PI 3-K) is activated. The presence of three adjacent equatorial phosphate groups was critical for inositol phosphate binding by the Grp1 PH domain. By contrast, another PH domain capable of PI 3-K-dependent membrane recruitment (encoded by EST684797) does not distinguish Ins(1,3,4)P3 from Ins(1,3,4,5)P3 (binding both with very high affinity), despite selecting strongly against Ins(1,4,5)P3. The remaining PH domains tested appear significantly less specific for particular phosphoinositides. Together with data presented in the literature, our results suggest that many PH domains bind similarly to multiple phosphoinositides (and in some cases phosphatidylserine), and are likely to be regulated in vivo by the most abundant species to which they bind. Thus, using the same simple approach to study several PH domains simultaneously, our studies suggest that highly specific phosphoinositide binding is a characteristic of relatively few cases.
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Affiliation(s)
- J M Kavran
- Department of Biochemistry and Biophysics, and Johnson Research Foundation, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6089, USA
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12
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Loomis-Husselbee JW, Walker CD, Bottomley JR, Cullen PJ, Irvine RF, Dawson AP. Modulation of Ins(2,4,5)P3-stimulated Ca2+ mobilization by ins(1,3,4, 5)P4: enhancement by activated G-proteins, and evidence for the involvement of a GAP1 protein, a putative Ins(1,3,4,5)P4 receptor. Biochem J 1998; 331 ( Pt 3):947-52. [PMID: 9560326 PMCID: PMC1219439 DOI: 10.1042/bj3310947] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have previously shown that addition of Ins(1,3,4,5)P4 to permeabilized L1210 cells increases the amount of Ca2+ mobilized by a submaximal concentration of Ins(2,4,5)P3, and we suggested that, in doing this, Ins(1,3,4,5)P4 is not working via an InsP3 receptor but indirectly via an InsP4 receptor [Loomis-Husselbee, Cullen, Dreikhausen, Irvine and Dawson (1996) Biochem. J. 314, 811-816]. Here we have investigated whether this effect might be mediated by GAP1(IP4BP), recently identified as a putative receptor for Ins(1,3, 4,5)P4. GAP1(IP4BP) is a protein that interacts with one or more monomeric G-proteins, so we sought evidence for involvement of monomeric G-proteins in the effects of Ins(1,3,4,5)P4 in permeabilized L1210 cells. Guanosine 5'-[gamma-thio]triphosphate (GTP[S]) enhanced the effect of Ins(1,3,4,5)P4 on Ins(2,4, 5)P3-stimulated Ca2+ mobilization, but had no effect on the action of Ins(2,4,5)P3 alone. A specific enhancement of only the action of Ins(1,3,4,5)P4 was also seen with GTP[S]-loaded R-Ras or Rap1a (two G-proteins known to interact with GAP1(IP4BP)), whereas H-Ras was inactive at similar concentrations. Guanosine 5'-[beta-thio]diphosphate (GDP[S]) did not alter the action of either Ins(2,4,5)P3 or Ins(1,3,4,5)P4. Finally, the addition of exogenous GAP1(IP4BP), purified from platelets, markedly enhanced the effect of Ins(1,3,4,5)P4, and again, the amount of Ca2+ mobilized by Ins(2,4,5)P3 alone was unaltered. We conclude that the increase in Ins(2,4,5)P3-stimulated Ca2+ mobilization by Ins(1,3,4, 5)P4 may be mediated by GAP1(IP4BP) or a closely related protein (such as GAP1(m)), and if so, the action of the GAP1 is not solely to regulate GTP loading of a G-protein, but rather it acts with a G-protein to cause its effect.
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Affiliation(s)
- J W Loomis-Husselbee
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QJ, UK.
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13
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Chung SK, Yu SH, Chang YT. Syntheses of D-Myo-Inositol-1,2,6-Trisphosphate and -2,6-bisphosphate. J Carbohydr Chem 1998. [DOI: 10.1080/07328309808002899] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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14
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Liu C, Potter BV. Synthesis of 3-Position-Modified Analogues of myo-Inositol 1,4,5-Trisphosphate, Tools for Investigation of the Polyphosphoinositide Pathway of Cellular Signaling. J Org Chem 1997; 62:8335-40. [PMID: 11671970 DOI: 10.1021/jo970926y] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methods for the synthesis of 3-O-(carboxymethyl)- and 3-O-alkylated myo-inositol 1,4,5-trisphosphates in racemic form from myo-inositol have been devised. For DL-3-O-(carboxymethyl)-myo-inositol 1,4,5-trisphosphate, an analogue of myo-inositol 1,3,4,5-tetrakisphosphate, DL-3-O-allyl-2,6-di-O-benzyl-1-O-(p-methoxybenzyl)-4,5-O-isopropylidene-myo-inositol (14) was prepared from myo-inositol in seven steps. The triol DL-3-O-allyl-2,6-di-O-benzyl-myo-inositol (26), which was obtained after treatment of 14 with acid, was phosphitylated and the product oxidized to give the fully protected trisphosphate 27. The efficient oxidative cleavage of the 3-O-allyl ether of 27 in the presence of the cyanoethyl-protected phosphate triesters was achieved by treatment of 27 with NaIO(4)/RuCl(3).hydrate to afford the fully protected 3-O-(carboxymethyl) trisphosphate 28. After deblocking, DL-3-O-(carboxymethyl) trisphosphate 6 was obtained. For DL-3-O-alkylated myo-inositol 1,4,5-trisphosphate analogues, the fully protected 14 was isomerized to the cis-prop-1-enyl derivative 15. The propenyl group was removed to give DL-2,6-di-O-benzyl-1-O-(p-methoxybenzyl)-4,5-isopropylidene-myo-inositol (16). The 3-O-methyl ether 17, 3-O-ethyl ether 18, and 3-O-n-propyl ether 19 derivatives were synthesized by treatment of the anion of 16 with methyl iodide, ethyl iodide, or n-propyl iodide, respectively. Removal of the isopropylidene and p-methoxybenzyl groups afforded 3-O-alkylated triols 20, 21, or 22, which were phosphitylated and the products oxidized to give the respective fully protected 3-O-alkylated trisphosphates 23-25. Deprotection furnished 3-O-methyl- (3), 3-O-ethyl- (4), or 3-O-n-propyl-myo-inositol 1,4,5-trisphosphate (5). These compounds will be useful pharmacological tools to explore the interaction of myo-inositol 1,4,5-trisphosphate with its receptor and metabolic enzymes.
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Affiliation(s)
- C Liu
- Department of Medicinal Chemistry, School of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, U.K
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15
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Choi G, Chang YT, Chung SK, Choi KY. Molecular interactions of all possible regioisomers of synthetic myo-inositol phosphates with inositol 1,4,5-trisphosphate 3-kinase. Bioorg Med Chem Lett 1997. [DOI: 10.1016/s0960-894x(97)10060-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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16
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Fischer KM. Parkinson's disease, amyotrophic lateral sclerosis and spinal muscular atrophy are caused by an unstable (CAG)n trinucleotide repeat microsatellite. Med Hypotheses 1997; 49:337-45. [PMID: 9352504 DOI: 10.1016/s0306-9877(97)90200-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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17
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Riley AM, Mahon MF, Potter BVL. Einfache Synthese der Enantiomere vonmyo-Inosit-1,3,4,5-tetrakisphosphat durch direkte chirale Desymmetrisierung vonmyo-Inositorthoformiat. Angew Chem Int Ed Engl 1997. [DOI: 10.1002/ange.19971091341] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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18
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Fukuda M, Mikoshiba K. Structure-function relationships of the mouse Gap1m. Determination of the inositol 1,3,4,5-tetrakisphosphate-binding domain. J Biol Chem 1996; 271:18838-42. [PMID: 8702543 DOI: 10.1074/jbc.271.31.18838] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Gap1(IP4BP), one of a member of Ras GTPase-activating proteins, has been identified as a specific inositol 1,3,4,5-tetrakisphosphate (IP4)-binding protein (Cullen, P. J., Hsuan, J. J., Truong, O., Letcher, A. J., Jackson, T. R., Dawson, A. P., and Irvine, R. F. (1995) Nature 386, 527-530). In this paper we describe Gap1(m), which is closely related to Gap1(IP4BP), to also be an IP4-binding protein and show that the pleckstrin homology domain (PH) is the central IP4-binding domain by expressing fragments of the mouse Gap1(m) in Escherichia coli as fusion proteins and examining their activities. However, in addition to the PH domain, an adjacent GAP-related domain and carboxyl terminus are required for high affinity specific IP4 binding. The PH domain is highly conserved in the Gap1 family and also has striking homology to the amino-terminal region of Bruton's tyrosine kinase. Substitution of Cys for Arg at position 628 in the PH domain corresponding to the mutation of Bruton's tyrosine kinase observed in X-linked immunodeficiency mice results in a dramatic reduction of IP4 binding activity as well as phospholipid binding capacity of Gap1(m). This mutant also showed the GAP activity against Ha-Ras to be similar to that of the wild type Gap1(m). Our results suggest that the PH domain of Gap1(m) functions as a modulatory domain of GAP activity by binding IP4 and phospholipids.
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Affiliation(s)
- M Fukuda
- Molecular Neurobiology Laboratory, Tsukuba Life Science Center, The Institute of Physical and Chemical Research (RIKEN), 3-1-1 Koyadai, Tsukuba, Ibaraki 305, Japan
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19
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O'Rourke F, Matthews E, Feinstein MB. Isolation of InsP4 and InsP6 binding proteins from human platelets: InsP4 promotes Ca2+ efflux from inside-out plasma membrane vesicles containing 104 kDa GAP1IP4BP protein. Biochem J 1996; 315 ( Pt 3):1027-34. [PMID: 8645140 PMCID: PMC1217257 DOI: 10.1042/bj3151027] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A low-density membrane fraction from human platelets contained the plasma membrane marker glycoprotein Ib (GpIb) and selective binding sites for InsP4 and InsP6. It was separated from the bulk of InsP3-receptor-containing membranes, but was heterogeneous, probably also containing surface-connected canalicular system and some lighter elements of the internal dense tubule system. After loading with calcium oxalate and re-centrifugation on Percoll gradients, this mixed fraction was subfractionated into light membranes containing all of the GpIb, high-affinity InsP4 binding sites (KD = 18 nM) and phosphate-stimulated Ca2+ transport activity. InsP4 (EC50 0.6 microM), but not InsP3 or InsP6, released up to 35% of the accumulated Ca2+ from these vesicles, which were shown to be inside-out plasma membrane vesicles by a biotinylation labelling technique and selective removal of right-side-out plasma membrane vesicles with streptavidin-agarose. Most of the InsP4, and all of the InsP6, binding was present in the much denser calcium oxalate-loaded subfractions, which were free of GpIb. InsP6 binding activity was chromatographically purified as a 116 kDa protein (KD for InsP6 = 5.9 nM), with an amino acid content and two internal peptide sequences identical to those of 116 kDa vinculin. A 104 kDa InsP4 binding protein (KD for InsP4 = 12 nM), probably identical to GAP1IP4BP described by Cullen, Hsuan, Truong, Letcher, Jackson, Dawson and Irvine [(1995) Nature (London) 376, 527-530], was also isolated. This InsP4 receptor may mediate Ca2+ influx in platelets that occurs subsequent to receptor-stimulated production of InsP3 and unloading of internal Ca2+ stores.
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Affiliation(s)
- F O'Rourke
- Department of Pharmacology, University of Connecticut School of Medicine, Farmington 06030, USA
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Shears SB. Inositol pentakis- and hexakisphosphate metabolism adds versatility to the actions of inositol polyphosphates. Novel effects on ion channels and protein traffic. Subcell Biochem 1996; 26:187-226. [PMID: 8744266 DOI: 10.1007/978-1-4613-0343-5_7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- S B Shears
- Inositol Lipid Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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Cullen PJ, Hsuan JJ, Truong O, Letcher AJ, Jackson TR, Dawson AP, Irvine RF. Identification of a specific Ins(1,3,4,5)P4-binding protein as a member of the GAP1 family. Nature 1995; 376:527-30. [PMID: 7637787 DOI: 10.1038/376527a0] [Citation(s) in RCA: 243] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4) is produced rapidly from inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) in stimulated cells. Despite extensive experimentation, no clearly defined cellular function has yet been described for this inositol phosphate. Binding sites specific for Ins(1,3,4,5)P4 have been identified in several tissues, and we have purified one such protein to homogeneity. Its high affinity for Ins(1,3,4,5)P4, and its exquisite specificity for this isomeric configuration, suggest it may be an Ins(1,3,4,5)P4 receptor. Here we report the cloning and characterization of this protein as a GTPase-activating protein, specifically a member of the GAP1 family. In vitro it shows GAP activity against both Rap and Ras, but only the Ras GAP activity is inhibited by phospholipids and is specifically stimulated by Ins(1,3,4,5)P4.
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Affiliation(s)
- P J Cullen
- Inositide Laboratory, Babraham Institute, Cambridge, UK
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