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Chakraborty P, Deb BK, Arige V, Musthafa T, Malik S, Yule DI, Taylor CW, Hasan G. Regulation of store-operated Ca 2+ entry by IP 3 receptors independent of their ability to release Ca 2. eLife 2023; 12:e80447. [PMID: 37466241 PMCID: PMC10406432 DOI: 10.7554/elife.80447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 07/18/2023] [Indexed: 07/20/2023] Open
Abstract
Loss of endoplasmic reticular (ER) Ca2+ activates store-operated Ca2+ entry (SOCE) by causing the ER localized Ca2+ sensor STIM to unfurl domains that activate Orai channels in the plasma membrane at membrane contact sites (MCS). Here, we demonstrate a novel mechanism by which the inositol 1,4,5 trisphosphate receptor (IP3R), an ER-localized IP3-gated Ca2+ channel, regulates neuronal SOCE. In human neurons, SOCE evoked by pharmacological depletion of ER-Ca2+ is attenuated by loss of IP3Rs, and restored by expression of IP3Rs even when they cannot release Ca2+, but only if the IP3Rs can bind IP3. Imaging studies demonstrate that IP3Rs enhance association of STIM1 with Orai1 in neuronal cells with empty stores; this requires an IP3-binding site, but not a pore. Convergent regulation by IP3Rs, may tune neuronal SOCE to respond selectively to receptors that generate IP3.
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Affiliation(s)
- Pragnya Chakraborty
- National Centre for Biological Sciences, Tata Institute of Fundamental ResearchBangaloreIndia
- SASTRA UniversityThanjavurIndia
| | - Bipan Kumar Deb
- National Centre for Biological Sciences, Tata Institute of Fundamental ResearchBangaloreIndia
| | - Vikas Arige
- Department of Pharmacology and Physiology, University of RochesterRochesterUnited States
| | - Thasneem Musthafa
- National Centre for Biological Sciences, Tata Institute of Fundamental ResearchBangaloreIndia
| | - Sundeep Malik
- Department of Pharmacology and Physiology, University of RochesterRochesterUnited States
| | - David I Yule
- Department of Pharmacology and Physiology, University of RochesterRochesterUnited States
| | - Colin W Taylor
- Department of Pharmacology, University of CambridgeCambridgeUnited Kingdom
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental ResearchBangaloreIndia
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2
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Taylor CW, Bowden SA. What about nitrogen? Using nitrogen as a carrier gas during the analysis of petroleum biomarkers by gas chromatography mass spectrometry. J Chromatogr A 2023; 1697:463989. [PMID: 37075497 DOI: 10.1016/j.chroma.2023.463989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 04/06/2023] [Accepted: 04/11/2023] [Indexed: 04/21/2023]
Abstract
Gas chromatography mass spectrometry (GC-MS) is a commonly used method for organic geochemistry for both academic research and applications such as petroleum analysis. Gas chromatography requires a carrier gas, which needs to be both volatile and stable and in most organic geochemical applications helium or hydrogen have been used, with helium predominating for gas chromatography mass spectrometry. Helium, however, is becoming an increasingly scarce resource and is not sustainable. Hydrogen is the most commonly considered alternative carrier gas to helium but has characteristics that in certain respects make its use less practical, foremost is that hydrogen is flammable and explosive. But as hydrogen is increasingly used as a fuel, higher demand may also make its use less desirable. Here we show that nitrogen can be used for the GC-MS analysis of fossil lipid biomarkers. Using nitrogen, chromatographic separation of isomers and homologues can be achieved, but sensitivity is orders of magnitude less than for helium. It is reasonable to use nitrogen as a carrier gas in applications where low levels of detection are not needed, such as the characterization of samples of crude oil or foodstuffs, or potentially as part of a gas-mixture seeking to reduce helium-demand but maintain a level of chromatographic separation sufficient to support proxy-based characterizations of petroleum.
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Affiliation(s)
- Colin W Taylor
- Department of Geology and Geophysics, School of Geosciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom, AB24 3UE, 01224 273495.
| | - Stephen A Bowden
- Department of Geology and Geophysics, School of Geosciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom, AB24 3UE, 01224 273495
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3
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Smith HA, Taylor CW. Dissociation of inositol 1,4,5-trisphosphate from IP 3 receptors contributes to termination of Ca 2+ puffs. J Biol Chem 2023; 299:102871. [PMID: 36621623 PMCID: PMC9971896 DOI: 10.1016/j.jbc.2023.102871] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/23/2022] [Accepted: 12/26/2022] [Indexed: 01/07/2023] Open
Abstract
Ca2+ puffs are brief, localized Ca2+ signals evoked by physiological stimuli that arise from the coordinated opening of a few clustered inositol 1,4,5-trisphosphate receptors (IP3Rs). However, the mechanisms that control the amplitude and termination of Ca2+ puffs are unresolved. To address these issues, we expressed SNAP-tagged IP3R3 in HEK cells without endogenous IP3Rs and used total internal reflection fluorescence microscopy to visualize the subcellular distribution of IP3Rs and the Ca2+ puffs that they evoke. We first confirmed that SNAP-IP3R3 were reliably identified and that they evoked normal Ca2+ puffs after photolysis of a caged analog of IP3. We show that increased IP3R expression caused cells to assemble more IP3R clusters, each of which contained more IP3Rs, but the mean amplitude of Ca2+ puffs (indicative of the number of open IP3Rs) was unaltered. We thus suggest that functional interactions between IP3Rs constrain the number of active IP3Rs within a cluster. Furthermore, Ca2+ puffs evoked by IP3R with reduced affinity for IP3 had undiminished amplitude, but the puffs decayed more quickly. The selective effect of reducing IP3 affinity on the decay times of Ca2+ puffs was not mimicked by exposing normal IP3R to a lower concentration of IP3. We conclude that distinct mechanisms constrain recruitment of IP3Rs during the rising phase of a Ca2+ puff and closure of IP3Rs during the falling phase, and that only the latter is affected by the rate of IP3 dissociation.
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Affiliation(s)
- Holly A Smith
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom.
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4
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Bootman MD, Galione A, Taylor CW. A tribute to Professor Sir Michael J. Berridge FRS (1938-2020). Biochim Biophys Acta Mol Cell Res 2021; 1868:119014. [PMID: 33756284 DOI: 10.1016/j.bbamcr.2021.119014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Martin D Bootman
- The Open University, School of Life, Health and Chemical Sciences, Faculty of Science, Technology, Engineering and Mathematics, Walton Hall, Milton Keynes MK7 6AA, UK.
| | - Antony Galione
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
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5
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Lagos-Cabré R, Ivanova A, Taylor CW. Ca 2+ Release by IP 3 Receptors Is Required to Orient the Mitotic Spindle. Cell Rep 2020; 33:108483. [PMID: 33326774 PMCID: PMC7758162 DOI: 10.1016/j.celrep.2020.108483] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 09/23/2020] [Accepted: 11/13/2020] [Indexed: 11/30/2022] Open
Abstract
The mitotic spindle distributes chromosomes evenly to daughter cells during mitosis. The orientation of the spindle, guided by internal and external cues, determines the axis of cell division and thereby contributes to tissue morphogenesis. Progression through mitosis requires local Ca2+ signals at critical steps, and because store-operated Ca2+ entry is inhibited during mitosis, those signals probably require Ca2+ release through inositol 1,4,5-trisphosphate receptors (IP3Rs). In cells without IP3Rs, astral microtubules around the daughter centrosome are shorter than those at the mother centrosome, and the mitotic spindle fails to align with the substratum during metaphase. The misalignment is due to the spindle ineffectively detecting internal cues rather than a failure of cells to recognize the substratum. Expression of type 3 IP3R is sufficient to rescue spindle alignment, but only if the IP3R has a functional pore. We conclude that Ca2+ signals evoked by IP3Rs are required to orient the mitotic spindle. IP3 receptors are required for mitotic spindle orientation Only IP3 receptors with a functional channel restore spindle orientation Ca2+ release through IP3 receptors is required for spindle orientation
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Affiliation(s)
- Raul Lagos-Cabré
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Adelina Ivanova
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
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Su X, Dohle W, Mills SJ, Watt JM, Rossi AM, Taylor CW, Potter BVL. Inositol Adenophostin: Convergent Synthesis of a Potent Agonist of d- myo-Inositol 1,4,5-Trisphosphate Receptors. ACS Omega 2020; 5:28793-28811. [PMID: 33195933 PMCID: PMC7659177 DOI: 10.1021/acsomega.0c04145] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 10/08/2020] [Indexed: 06/11/2023]
Abstract
d-myo-Inositol 1,4,5-trisphosphate receptors (IP3Rs) are Ca2+ channels activated by the intracellular messenger inositol 1,4,5-trisphosphate (IP3, 1). The glyconucleotide adenophostin A (AdA, 2) is a potent agonist of IP3Rs. A recent synthesis of d-chiro-inositol adenophostin (InsAdA, 5) employed suitably protected chiral building blocks and replaced the d-glucose core by d-chiro-inositol. An alternative approach to fully chiral material is now reported using intrinsic sugar chirality to avoid early isomer resolution, involving the coupling of a protected and activated racemic myo-inositol derivative to a d-ribose derivative. Diastereoisomer separation was achieved after trans-isopropylidene group removal and the absolute ribose-inositol conjugate stereochemistry assigned with reference to the earlier synthesis. Optimization of stannylene-mediated regiospecific benzylation was explored using the model 1,2-O-isopropylidene-3,6-di-O-benzyl-myo-inositol and conditions successfully transferred to one conjugate diastereoisomer with 3:1 selectivity. However, only roughly 1:1 regiospecificity was achieved on the required diastereoisomer. The conjugate regioisomers of benzyl derivatives 39 and 40 were successfully separated and 39 was transformed subsequently to InsAdA after amination, pan-phosphorylation, and deprotection. InsAdA from this synthetic route bound with greater affinity than AdA to IP3R1 and was more potent in releasing Ca2+ from intracellular stores through IP3Rs. It is the most potent full agonist of IP3R1 known and .equipotent with material from the fully chiral synthetic route.
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Affiliation(s)
- Xiangdong Su
- Medicinal
Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K.
| | - Wolfgang Dohle
- Medicinal
Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K.
| | - Stephen J. Mills
- Medicinal
Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K.
| | - Joanna M. Watt
- Medicinal
Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K.
- Wolfson
Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, U.K.
| | - Ana M. Rossi
- Department
of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
| | - Colin W. Taylor
- Department
of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
| | - Barry V. L. Potter
- Medicinal
Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K.
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8
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Shipton ML, Riley AM, Rossi AM, Brearley CA, Taylor CW, Potter BVL. Both d- and l-Glucose Polyphosphates Mimic d- myo-Inositol 1,4,5-Trisphosphate: New Synthetic Agonists and Partial Agonists at the Ins(1,4,5)P 3 Receptor. J Med Chem 2020; 63:5442-5457. [PMID: 32286062 PMCID: PMC7260056 DOI: 10.1021/acs.jmedchem.0c00215] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
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Chiral sugar derivatives are potential
cyclitol surrogates of the
Ca2+-mobilizing intracellular messenger d-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. Six novel polyphosphorylated analogues derived from both d- and l-glucose were synthesized. Binding to Ins(1,4,5)P3 receptors [Ins(1,4,5)P3R] and the ability to release
Ca2+ from intracellular stores via type 1 Ins(1,4,5)P3Rs were investigated. β-d-Glucopyranosyl 1,3,4-tris-phosphate,
with similar phosphate regiochemistry and stereochemistry to Ins(1,4,5)P3, and α-d-glucopyranosyl 1,3,4-tris-phosphate
are full agonists, being equipotent and 23-fold less potent than Ins(1,4,5)P3, respectively, in Ca2+-release assays and similar
to Ins(1,4,5)P3 and 15-fold weaker in binding assays. They
can be viewed as truncated analogues of adenophostin A and refine
understanding of structure-activity relationships for this Ins(1,4,5)P3R agonist. l-Glucose-derived ligands, methyl α-l-glucopyranoside 2,3,6-trisphosphate and methyl α-l-glucopyranoside 2,4,6-trisphosphate, are also active, while
their corresponding d-enantiomers, methyl α-d-glucopyranoside 2,3,6-trisphosphate and methyl α-d-glucopyranoside 2,4,6-trisphosphate, are inactive. Interestingly,
both l-glucose-derived ligands are partial agonists: they
are among the least efficacious agonists of Ins(1,4,5)P3R yet identified, providing new leads for antagonist development.
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Affiliation(s)
- Megan L Shipton
- Drug Discovery & Medicinal Chemistry, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U. K
| | - Andrew M Riley
- Drug Discovery & Medicinal Chemistry, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U. K
| | - Ana M Rossi
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U. K
| | - Charles A Brearley
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U. K
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U. K
| | - Barry V L Potter
- Drug Discovery & Medicinal Chemistry, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U. K
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9
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Taylor CW, Dodwell D, Darby SC, Broggio J, McGale P. Eligibility for Partial Breast Radiotherapy in England. Clin Oncol (R Coll Radiol) 2020; 32:217-220. [PMID: 31668377 DOI: 10.1016/j.clon.2019.09.061] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 09/11/2019] [Indexed: 11/25/2022]
Affiliation(s)
- C W Taylor
- Nuffield Department of Population Health, University of Oxford, Oxford, UK; Oxford University Hospitals NHS Foundation Trust, Oxford, UK.
| | - D Dodwell
- Nuffield Department of Population Health, University of Oxford, Oxford, UK; Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - S C Darby
- Nuffield Department of Population Health, University of Oxford, Oxford, UK
| | - J Broggio
- Public Health England, Birmingham, UK
| | - P McGale
- Nuffield Department of Population Health, University of Oxford, Oxford, UK
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10
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Mills SJ, Rossi AM, Konieczny V, Bakowski D, Taylor CW, Potter BVL. d- chiro-Inositol Ribophostin: A Highly Potent Agonist of d- myo-Inositol 1,4,5-Trisphosphate Receptors: Synthesis and Biological Activities. J Med Chem 2020; 63:3238-3251. [PMID: 32052631 PMCID: PMC7104261 DOI: 10.1021/acs.jmedchem.9b01986] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Analogues
of the Ca2+-releasing intracellular messenger d-myo-inositol 1,4,5-trisphosphate [1, Ins(1,4,5)P3] are important synthetic targets. Replacement
of the α-glucopyranosyl motif in the natural product mimic adenophostin 2 by d-chiro-inositol in d-chiro-inositol adenophostin 4 increased
the potency. Similar modification of the non-nucleotide Ins(1,4,5)P3 mimic ribophostin 6 may increase the activity. d-chiro-Inositol ribophostin 10 was synthesized by coupling as building blocks suitably protected
ribose 12 with l-(+)-3-O-trifluoromethylsulfonyl-6-O-p-methoxybenzyl-1,2:4,5-di-O-isopropylidene-myo-inositol 11. Separable
diastereoisomeric 3-O-camphanate esters of (±)-6-O-p-methoxy-benzyl-1,2:4,5-di-O-isopropylidene-myo-inositol allowed the preparation
of 11. Selective trans-isopropylidene
deprotection in coupled 13, then monobenzylation gave
separable regioisomers 15 and 16. p-Methoxybenzyl group deprotection of 16, phosphitylation/oxidation,
then deprotection afforded 10, which was a full agonist
in Ca2+-release assays; its potency and binding affinity
for Ins(1,4,5)P3R were similar to those of adenophostin.
Both 4 and 10 elicited a store-operated
Ca2+ current ICRAC in patch-clamped cells, unlike
Ins(1,4,5)P3 consistent with resistance to metabolism. d-chiro-Inositol ribophostin is the most potent
small-molecule Ins(1,4,5)P3 receptor agonist without a
nucleobase yet synthesized.
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Affiliation(s)
- Stephen J Mills
- Drug Discovery & Medicinal Chemistry, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom
| | - Ana M Rossi
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Vera Konieczny
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Daniel Bakowski
- Centre of Integrative Physiology, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Barry V L Potter
- Drug Discovery & Medicinal Chemistry, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom
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11
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Rossi AM, Taylor CW. Reliable measurement of free Ca 2+ concentrations in the ER lumen using Mag-Fluo-4. Cell Calcium 2020; 87:102188. [PMID: 32179239 PMCID: PMC7181174 DOI: 10.1016/j.ceca.2020.102188] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/27/2020] [Accepted: 02/27/2020] [Indexed: 12/12/2022]
Abstract
Mag-Fluo-4 loaded into ER by incubation of cells with Mag-Fluo-4 AM reliably reports ER free [Ca2+]. However, the Ca2+ affinity of Mag-Fluo-4 determined in vitro appears too high to allow measurements of ER luminal [Ca2+]. We use an antibody (QAb) to quench the fluorescence of leaked indicator. Using QAb, we show that indicator within the ER has low affinity and sensitivity across a wide range of [Ca2+]. Incomplete de-esterification of compartmentalized indicator allows it to effectively report ER free [Ca2+].
Synthetic Ca2+ indicators are widely used to report changes in free [Ca2+], usually in the cytosol but also within organelles. Mag-Fluo-4, loaded into the endoplasmic reticulum (ER) by incubating cells with Mag-Fluo-4 AM, has been used to measure changes in free [Ca2+] within the ER, where the free [Ca2+] is estimated to be between 100 μM and 1 mM. Many results are consistent with Mag-Fluo-4 reliably reporting changes in free [Ca2+] within the ER, but the results are difficult to reconcile with the affinity of Mag-Fluo-4 for Ca2+ measured in vitro (KDCa ∼22 μM). Using an antibody to quench the fluorescence of indicator that leaked from the ER, we established that the affinity of Mag-Fluo-4 within the ER is much lower (KDCa ∼1 mM) than that measured in vitro. We show that partially de-esterified Mag-Fluo-4 has reduced affinity for Ca2+, suggesting that incomplete de-esterification of Mag-Fluo-4 AM within the ER provides indicators with affinities for Ca2+ that are both appropriate for the ER lumen and capable of reporting a wide range of free [Ca2+].
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Affiliation(s)
- Ana M Rossi
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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12
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Atakpa P, Thillaiappan NB, Mataragka S, Prole DL, Taylor CW. IP 3 Receptors Preferentially Associate with ER-Lysosome Contact Sites and Selectively Deliver Ca 2+ to Lysosomes. Cell Rep 2019; 25:3180-3193.e7. [PMID: 30540949 PMCID: PMC6302550 DOI: 10.1016/j.celrep.2018.11.064] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 07/30/2018] [Accepted: 11/15/2018] [Indexed: 12/22/2022] Open
Abstract
Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) allow extracellular stimuli to redistribute Ca2+ from the ER to cytosol or other organelles. We show, using small interfering RNA (siRNA) and vacuolar H+-ATPase (V-ATPase) inhibitors, that lysosomes sequester Ca2+ released by all IP3R subtypes, but not Ca2+ entering cells through store-operated Ca2+ entry (SOCE). A low-affinity Ca2+ sensor targeted to lysosomal membranes reports large, local increases in cytosolic [Ca2+] during IP3-evoked Ca2+ release, but not during SOCE. Most lysosomes associate with endoplasmic reticulum (ER) and dwell at regions populated by IP3R clusters, but IP3Rs do not assemble ER-lysosome contacts. Increasing lysosomal pH does not immediately prevent Ca2+ uptake, but it causes lysosomes to slowly redistribute and enlarge, reduces their association with IP3Rs, and disrupts Ca2+ exchange with ER. In a "piston-like" fashion, ER concentrates cytosolic Ca2+ and delivers it, through large-conductance IP3Rs, to a low-affinity lysosomal uptake system. The involvement of IP3Rs allows extracellular stimuli to regulate Ca2+ exchange between the ER and lysosomes.
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Affiliation(s)
- Peace Atakpa
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | | | - Stefania Mataragka
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - David L Prole
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
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13
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Duane FK, McGale P, Teoh S, Mortimer C, Broggio J, Darby SC, Dodwell D, Lavery B, Oliveros S, Vallis KA, Taylor CW. International Variation in Criteria for Internal Mammary Chain Radiotherapy. Clin Oncol (R Coll Radiol) 2019; 31:453-461. [PMID: 31060973 PMCID: PMC6575151 DOI: 10.1016/j.clon.2019.04.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 03/08/2019] [Accepted: 03/16/2019] [Indexed: 11/29/2022]
Abstract
AIMS Evidence has emerged that internal mammary chain (IMC) radiotherapy reduces breast cancer mortality, leading to changes in treatment guidelines. This study investigated current IMC radiotherapy criteria and the percentages of patients irradiated for breast cancer in England who fulfilled them. MATERIALS AND METHODS A systematic search was undertaken for national guidelines published in English during 2013-2018 presenting criteria for 'consideration of' or 'recommendation for' IMC radiotherapy. Patient and tumour variables were collected for patients who received breast cancer radiotherapy in England during 2012-2016. The percentages of patients fulfilling criteria stipulated in each set of guidelines were calculated. RESULTS In total, 111 729 women were recorded as receiving adjuvant breast cancer radiotherapy in England during 2012-2016 and full data were available on 48 095 of them. Percentages of patients fulfilling IMC radiotherapy criteria in various national guidelines were: UK Royal College of Radiologists 13% (6035/48 095), UK National Institute for Health and Care Excellence 18% (8816/48 095), Germany 32% (15 646/48 095), Ireland 56% (26 846/48 095) and USA 59% (28 373/48 095). Differences between countries occurred because in Ireland and the USA, treatment may be considered in some node-negative patients, whereas in the UK, treatment is considered if at least four axillary nodes are involved or for high-risk patients with one to three positive nodes. In Germany, treatment may be considered for all node-positive patients. CONCLUSIONS There is substantial variability between countries in criteria for consideration of IMC radiotherapy, despite guidelines being based on the same evidence. This will probably lead to large variations in practice and resource needs worldwide.
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Affiliation(s)
- F K Duane
- St Luke's Radiation Oncology Network, St. James's Hospital, Dublin, Ireland.
| | - P McGale
- Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK
| | - S Teoh
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK
| | - C Mortimer
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK
| | - J Broggio
- Public Health England, Birmingham, UK
| | - S C Darby
- Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK
| | - D Dodwell
- Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK
| | - B Lavery
- Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - S Oliveros
- Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - K A Vallis
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK
| | - C W Taylor
- Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK; Oxford University Hospitals NHS Foundation Trust, Oxford, UK
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14
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Prole DL, Taylor CW. A genetically encoded toolkit of functionalized nanobodies against fluorescent proteins for visualizing and manipulating intracellular signalling. BMC Biol 2019; 17:41. [PMID: 31122229 PMCID: PMC6533734 DOI: 10.1186/s12915-019-0662-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 05/02/2019] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Intrabodies enable targeting of proteins in live cells, but generating specific intrabodies against the thousands of proteins in a proteome poses a challenge. We leverage the widespread availability of fluorescently labelled proteins to visualize and manipulate intracellular signalling pathways in live cells by using nanobodies targeting fluorescent protein tags. RESULTS We generated a toolkit of plasmids encoding nanobodies against red and green fluorescent proteins (RFP and GFP variants), fused to functional modules. These include fluorescent sensors for visualization of Ca2+, H+ and ATP/ADP dynamics; oligomerising or heterodimerising modules that allow recruitment or sequestration of proteins and identification of membrane contact sites between organelles; SNAP tags that allow labelling with fluorescent dyes and targeted chromophore-assisted light inactivation; and nanobodies targeted to lumenal sub-compartments of the secretory pathway. We also developed two methods for crosslinking tagged proteins: a dimeric nanobody, and RFP-targeting and GFP-targeting nanobodies fused to complementary hetero-dimerizing domains. We show various applications of the toolkit and demonstrate, for example, that IP3 receptors deliver Ca2+ to the outer membrane of only a subset of mitochondria and that only one or two sites on a mitochondrion form membrane contacts with the plasma membrane. CONCLUSIONS This toolkit greatly expands the utility of intrabodies and will enable a range of approaches for studying and manipulating cell signalling in live cells.
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Affiliation(s)
- David L Prole
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK.
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK.
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15
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Dohle W, Su X, Mills SJ, Rossi AM, Taylor CW, Potter BVL. A synthetic cyclitol-nucleoside conjugate polyphosphate is a highly potent second messenger mimic. Chem Sci 2019; 10:5382-5390. [PMID: 31171961 PMCID: PMC6540904 DOI: 10.1039/c9sc00445a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A densely functionalised phosphorylated chiro-inositol-nucleoside ether conjugate constructed from cyclic fragments is the most potent IP3 receptor ligand discovered.
Reactions that form sec–sec ethers are well known, but few lead to compounds with dense functionality around the O-linkage. Replacement of the α-glucopyranosyl unit of adenophostin A, a potent d-myo-inositol 1,4,5-trisphosphate (IP3R) agonist, with a d-chiro-inositol surrogate acting substantially as a pseudosugar, leads to “d-chiro-inositol adenophostin”. At its core, this cyclitol-nucleoside trisphosphate comprises an ether linkage between the axial 1-hydroxyl position of d-chiro-inositol and the 3′-hydroxyl group of an adenosine ribose sugar. A divergent synthesis of d-chiro-inositol adenophostin has been achieved. Key features of the synthetic strategy to produce a triol for phosphorylation include a new selective mono-tosylation of racemic 1,2:4,5-di-O-isopropylidene-myo-inositol using tosyl imidazole; subsequent conversion of the product into separable camphanate ester derivatives, one leading to a chiral myo-inositol triflate used as a synthetic building block and the other to l-1-O-methyl-myo-inositol [l-(+)-bornesitol] to assign the absolute configuration; the nucleophilic coupling of an alkoxide of a ribose pent-4-ene orthoester unit with a structurally rigid chiral myo-inositol triflate derivative, representing the first sec–sec ether formation between a cyclitol and ribose. Reaction of the coupled product with a silylated nucleobase completes the assembly of the core structure. Further protecting group manipulation, mixed O- and N-phosphorylation, and subsequent removal of all protecting groups in a single step achieves the final product, avoiding a separate N6 protection/deprotection strategy. d-chiro-Inositol adenophostin evoked Ca2+ release through IP3Rs at lower concentrations than adenophostin A, hitherto the most potent known agonist of IP3Rs.
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Affiliation(s)
- Wolfgang Dohle
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Xiangdong Su
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Stephen J Mills
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Ana M Rossi
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Barry V L Potter
- Medicinal Chemistry & Drug Discovery, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
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16
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Taylor CW, Machaca K. IP3 receptors and store-operated Ca2+ entry: a license to fill. Curr Opin Cell Biol 2019; 57:1-7. [DOI: 10.1016/j.ceb.2018.10.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 10/05/2018] [Indexed: 10/28/2022]
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17
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Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs), by releasing Ca2+ from the endoplasmic reticulum (ER) of animal cells, allow Ca2+ to be redistributed from the ER to the cytosol or other organelles, and they initiate store-operated Ca2+ entry (SOCE). For all three IP3R subtypes, binding of IP3 primes them to bind Ca2+, which then triggers channel opening. We are now close to understanding the structural basis of IP3R activation. Ca2+-induced Ca2+ release regulated by IP3 allows IP3Rs to regeneratively propagate Ca2+ signals. The smallest of these regenerative events is a Ca2+ puff, which arises from the nearly simultaneous opening of a small cluster of IP3Rs. Ca2+ puffs are the basic building blocks for all IP3-evoked Ca2+ signals, but only some IP3 clusters, namely those parked alongside the ER-plasma membrane junctions where SOCE occurs, are licensed to respond. The location of these licensed IP3Rs may allow them to selectively regulate SOCE.
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Affiliation(s)
- David L Prole
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
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18
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Atakpa P, van Marrewijk LM, Apta-Smith M, Chakraborty S, Taylor CW. GPN does not release lysosomal Ca 2+ but evokes Ca 2+ release from the ER by increasing the cytosolic pH independently of cathepsin C. J Cell Sci 2019; 132:jcs223883. [PMID: 30617110 PMCID: PMC6382017 DOI: 10.1242/jcs.223883] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 12/20/2018] [Indexed: 12/15/2022] Open
Abstract
The dipeptide glycyl-l-phenylalanine 2-naphthylamide (GPN) is widely used to perturb lysosomes because its cleavage by the lysosomal enzyme cathepsin C is proposed to rupture lysosomal membranes. We show that GPN evokes a sustained increase in lysosomal pH (pHly), and transient increases in cytosolic pH (pHcyt) and Ca2+ concentration ([Ca2+]c). None of these effects require cathepsin C, nor are they accompanied by rupture of lysosomes, but they are mimicked by structurally unrelated weak bases. GPN-evoked increases in [Ca2+]c require Ca2+ within the endoplasmic reticulum (ER), but they are not mediated by ER Ca2+ channels amplifying Ca2+ release from lysosomes. GPN increases [Ca2+]c by increasing pHcyt, which then directly stimulates Ca2+ release from the ER. We conclude that physiologically relevant increases in pHcyt stimulate Ca2+ release from the ER in a manner that is independent of IP3 and ryanodine receptors, and that GPN does not selectively target lysosomes.
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Affiliation(s)
- Peace Atakpa
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Laura M van Marrewijk
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Michael Apta-Smith
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Sumita Chakraborty
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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19
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Brailoiu E, Chakraborty S, Brailoiu GC, Zhao P, Barr JL, Ilies MA, Unterwald EM, Abood ME, Taylor CW. Choline Is an Intracellular Messenger Linking Extracellular Stimuli to IP 3-Evoked Ca 2+ Signals through Sigma-1 Receptors. Cell Rep 2019; 26:330-337.e4. [PMID: 30625315 PMCID: PMC6326163 DOI: 10.1016/j.celrep.2018.12.051] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 10/11/2018] [Accepted: 12/11/2018] [Indexed: 11/18/2022] Open
Abstract
Sigma-1 receptors (Sig-1Rs) are integral ER membrane proteins. They bind diverse ligands, including psychoactive drugs, and regulate many signaling proteins, including the inositol 1,4,5-trisphosphate receptors (IP3Rs) that release Ca2+ from the ER. The endogenous ligands of Sig-1Rs are unknown. Phospholipase D (PLD) cleaves phosphatidylcholine to choline and phosphatidic acid (PA), with PA assumed to mediate all downstream signaling. We show that choline is also an intracellular messenger. Choline binds to Sig-1Rs, it mimics other Sig-1R agonists by potentiating Ca2+ signals evoked by IP3Rs, and it is deactivated by metabolism. Receptors, by stimulating PLC and PLD, deliver two signals to IP3Rs: IP3 activates IP3Rs, and choline potentiates their activity through Sig-1Rs. Choline is also produced at synapses by degradation of acetylcholine. Choline uptake by transporters activates Sig-1Rs and potentiates Ca2+ signals. We conclude that choline is an endogenous agonist of Sig-1Rs linking extracellular stimuli, and perhaps synaptic activity, to Ca2+ signals.
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Affiliation(s)
- Eugen Brailoiu
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA.
| | | | - G Cristina Brailoiu
- Department of Pharmaceutical Sciences, Jefferson College of Pharmacy, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Pingwei Zhao
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Jeffrey L Barr
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Marc A Ilies
- Department of Pharmaceutical Sciences, Temple University School of Pharmacy, Philadelphia, PA 19140, USA
| | - Ellen M Unterwald
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Mary E Abood
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Colin W Taylor
- Department of Pharmacology, Tennis Court Road, Cambridge CB2 1PD, UK.
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20
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Abstract
ABSTRACT
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are widely expressed intracellular channels that release Ca2+ from the endoplasmic reticulum (ER). We review how studies of IP3Rs removed from their intracellular environment (‘ex cellula’), alongside similar analyses of ryanodine receptors, have contributed to understanding IP3R behaviour. Analyses of permeabilized cells have demonstrated that the ER is the major intracellular Ca2+ store, and that IP3 stimulates Ca2+ release from this store. Radioligand binding confirmed that the 4,5-phosphates of IP3 are essential for activating IP3Rs, and facilitated IP3R purification and cloning, which paved the way for structural analyses. Reconstitution of IP3Rs into lipid bilayers and patch-clamp recording from the nuclear envelope have established that IP3Rs have a large conductance and select weakly between Ca2+ and other cations. Structural analyses are now revealing how IP3 binding to the N-terminus of the tetrameric IP3R opens the pore ∼7 nm away from the IP3-binding core (IBC). Communication between the IBC and pore passes through a nexus of interleaved domains contributed by structures associated with the pore and cytosolic domains, which together contribute to a Ca2+-binding site. These structural analyses provide evidence to support the suggestion that IP3 gates IP3Rs by first stimulating Ca2+ binding, which leads to pore opening and Ca2+ release.
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Affiliation(s)
- Ana M. Rossi
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W. Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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21
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Thillaiappan NB, Chakraborty P, Hasan G, Taylor CW. IP 3 receptors and Ca 2+ entry. Biochim Biophys Acta Mol Cell Res 2018; 1866:1092-1100. [PMID: 30448464 DOI: 10.1016/j.bbamcr.2018.11.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 11/07/2018] [Accepted: 11/08/2018] [Indexed: 12/23/2022]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3R) are the most widely expressed intracellular Ca2+ release channels. Their activation by IP3 and Ca2+ allows Ca2+ to pass rapidly from the ER lumen to the cytosol. The resulting increase in cytosolic [Ca2+] may directly regulate cytosolic effectors or fuel Ca2+ uptake by other organelles, while the decrease in ER luminal [Ca2+] stimulates store-operated Ca2+ entry (SOCE). We are close to understanding the structural basis of both IP3R activation, and the interactions between the ER Ca2+-sensor, STIM, and the plasma membrane Ca2+ channel, Orai, that lead to SOCE. IP3Rs are the usual means through which extracellular stimuli, through ER Ca2+ release, stimulate SOCE. Here, we review evidence that the IP3Rs most likely to respond to IP3 are optimally placed to allow regulation of SOCE. We also consider evidence that IP3Rs may regulate SOCE downstream of their ability to deplete ER Ca2+ stores. Finally, we review evidence that IP3Rs in the plasma membrane can also directly mediate Ca2+ entry in some cells.
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Affiliation(s)
| | - Pragnya Chakraborty
- Department of Pharmacology, Tennis Court Road, Cambridge CB2 1PD, United Kingdom; National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore 560065, India
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore 560065, India
| | - Colin W Taylor
- Department of Pharmacology, Tennis Court Road, Cambridge CB2 1PD, United Kingdom.
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22
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Müller MS, Fouyssac M, Taylor CW. Effective Glucose Uptake by Human Astrocytes Requires Its Sequestration in the Endoplasmic Reticulum by Glucose-6-Phosphatase-β. Curr Biol 2018; 28:3481-3486.e4. [PMID: 30415704 PMCID: PMC6224479 DOI: 10.1016/j.cub.2018.08.060] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 08/08/2018] [Accepted: 08/29/2018] [Indexed: 12/12/2022]
Abstract
After its uptake into the cytosol, intracellular glucose is phosphorylated to glucose-6-phosphate (G6P), trapping it within the cell and preparing it for metabolism. In glucose-exporting tissues, like liver, G6P is transported into the ER, where it is dephosphorylated by G6Pase-α. The glucose is then returned to the cytosol for export [1, 2]. Defects in these pathways cause glycogen storage diseases [1]. G6Pase-β, an isozyme of G6Pase-α, is widely expressed [3, 4]. Its role in cells that do not export glucose is unclear, although mutations in G6Pase-β cause severe and widespread abnormalities [5, 6, 7]. Astrocytes, the most abundant cells in the brain, provide metabolic support to neurons, facilitated by astrocytic endfeet that contact blood capillaries or neurons [8, 9, 10, 11, 12]. Perivascular endfeet are the main site of glucose uptake by astrocytes [13], but in human brain they may be several millimeters away from the perineuronal processes [14]. We show that cultured human fetal astrocytes express G6Pase-β, but not G6Pase-α. ER-targeted glucose sensors [15, 16] reveal that G6Pase-β allows the ER of human astrocytes to accumulate glucose by importing G6P from the cytosol. Glucose uptake by astrocytes, ATP production, and Ca2+ accumulation by the ER are attenuated after knockdown of G6Pase-β using lentivirus-delivered shRNA and substantially rescued by expression of G6Pase-α. We suggest that G6Pase-β activity allows effective uptake of glucose by astrocytes, and we speculate that it allows the ER to function as an intracellular “highway” delivering glucose from perivascular endfeet to the perisynaptic processes. Glucose-6-phosphatase-β (G6Pase-β) is expressed in human astrocytes G6P is sequestered by ER and dephosphorylated to glucose in the lumen by G6Pase-β Loss of G6Pase-β reduces glucose uptake, intracellular ATP, and ER Ca2+ content ER may provide a protected highway for long-range glucose transport in astrocytes
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Affiliation(s)
- Margit S Müller
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK.
| | - Maxime Fouyssac
- Department of Psychology, University of Cambridge, Cambridge CB2 3EB, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK.
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23
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Mataragka S, Taylor CW. All three IP 3 receptor subtypes generate Ca 2+ puffs, the universal building blocks of IP 3-evoked Ca 2+ signals. J Cell Sci 2018; 131:jcs.220848. [PMID: 30097556 PMCID: PMC6127726 DOI: 10.1242/jcs.220848] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 07/27/2018] [Indexed: 12/19/2022] Open
Abstract
All three subtypes of inositol 1,4,5-trisphosphate receptor (IP3R) are intracellular Ca2+ channels that are co-regulated by IP3 and Ca2+. This allows IP3Rs to evoke regenerative Ca2+ signals, the smallest of which are Ca2+ puffs that reflect the coordinated opening of a few clustered IP3Rs. We use total internal reflection microscopy (TIRF) microscopy to record Ca2+ signals in HEK cells expressing all three IP3R subtypes or a single native subtype. Ca2+ puffs are less frequent in cells expressing one IP3R subtype, commensurate with them expressing fewer IP3Rs than wild-type cells. However, all three IP3R subtypes generate broadly similar Ca2+ puffs with similar numbers of IP3Rs contributing to each. This suggests that IP3R clusters may be assembled by conserved mechanisms that generate similarly sized clusters across different IP3R expression levels. The Ca2+ puffs evoked by IP3R2 had slower kinetics and more prolonged durations, which may be due to IP3 binding with greater affinity to IP3R2. We conclude that Ca2+ puffs are the building blocks for the Ca2+ signals evoked by all IP3Rs. Summary: All IP3 receptor subtypes can generate Ca2+ puffs, suggesting that these coordinated openings of clustered IP3Rs are the building blocks of all IP3-evoked Ca2+ signals.
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Affiliation(s)
- Stefania Mataragka
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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24
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Riley AM, Unterlass JE, Konieczny V, Taylor CW, Helleday T, Potter BVL. A synthetic diphosphoinositol phosphate analogue of inositol trisphosphate. Medchemcomm 2018; 9:1105-1113. [PMID: 30079174 PMCID: PMC6071853 DOI: 10.1039/c8md00149a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 05/01/2018] [Indexed: 01/17/2023]
Abstract
Diphosphoinositol phosphates (PP-InsPs) are inositol phosphates (InsPs) that contain PP (diphosphate) groups. Converting a phosphate group in an InsP into a diphosphate has been reported to enhance affinity for some binding proteins. We synthesised 1-PP-Ins(4,5)P2, the first diphosphate analogue of the intracellular signalling molecule InsP3, and examined its effects on InsP3 receptors, which are intracellular Ca2+ channels. 1-PP-Ins(4,5)P2 was indistinguishable from InsP3 in its ability to bind to and activate type 1 InsP3 receptors, indicating that the diphosphate modification of InsP3 affected neither affinity nor efficacy. Nevertheless, 1-PP-Ins(4,5)P2 is the most potent 1-phosphate modified analogue of InsP3 yet identified. PP-InsPs are generally hydrolysed by diphosphoinositol phosphate phosphohydrolases (DIPPs), but 1-PP-Ins(4,5)P2 was not readily metabolised by human DIPPs. Differential scanning fluorimetry showed that 1-PP-Ins(4,5)P2 stabilises DIPP proteins, but to a lesser extent than naturally occurring substrates 1-PP-InsP5 and 5-PP-InsP5. The non-hydrolysable InsP7 analogues 1-PCP-InsP5 and 5-PCP-InsP5 showed comparable stabilising abilities to their natural counterparts and may therefore be promising substrate analogues for co-crystallisation with DIPPs.
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Affiliation(s)
- Andrew M. Riley
- Medicinal Chemistry and Drug Discovery
, Department of Pharmacology
, University of Oxford
,
Mansfield Road
, Oxford OX1 3QT
, UK
.
; Fax: +44 (0)1865 271853
; Tel: +44 (0)1865 271945
| | - Judith E. Unterlass
- Science for Life Laboratory
, Department of Oncology-Pathology
, Karolinska Institutet
,
SE-171 21 Solna
, Sweden
| | - Vera Konieczny
- Department of Pharmacology
, University of Cambridge
,
Tennis Court Road
, Cambridge CB2 1PD
, UK
| | - Colin W. Taylor
- Department of Pharmacology
, University of Cambridge
,
Tennis Court Road
, Cambridge CB2 1PD
, UK
| | - Thomas Helleday
- Science for Life Laboratory
, Department of Oncology-Pathology
, Karolinska Institutet
,
SE-171 21 Solna
, Sweden
| | - Barry V. L. Potter
- Medicinal Chemistry and Drug Discovery
, Department of Pharmacology
, University of Oxford
,
Mansfield Road
, Oxford OX1 3QT
, UK
.
; Fax: +44 (0)1865 271853
; Tel: +44 (0)1865 271945
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25
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Dale P, Head V, Dowling MR, Taylor CW. Selective inhibition of histamine-evoked Ca 2+ signals by compartmentalized cAMP in human bronchial airway smooth muscle cells. Cell Calcium 2017; 71:53-64. [PMID: 29604964 PMCID: PMC5893132 DOI: 10.1016/j.ceca.2017.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 12/13/2017] [Accepted: 12/13/2017] [Indexed: 01/29/2023]
Abstract
β2-adrenoceptors, via cAMP and PKA, inhibit histamine-evoked Ca2+ signals in human bronchial airway smooth muscle cells. Responses to other Ca2+-mobilizing receptors are unaffected or minimally affected by cAMP. There is no consistent relationship between the amounts of cAMP produced by different stimuli and inhibition of histamine-evoked Ca2+ release. Local delivery of cAMP within hyperactive signaling junctions stimulates PKA. PKA inhibits an early step in the signaling pathway activated by H1 histamine receptors.
Intracellular Ca2+ and cAMP typically cause opposing effects on airway smooth muscle contraction. Receptors that stimulate these pathways are therapeutic targets in asthma and chronic obstructive pulmonary disease. However, the interactions between different G protein-coupled receptors (GPCRs) that evoke cAMP and Ca2+ signals in human bronchial airway smooth muscle cells (hBASMCs) are poorly understood. We measured Ca2+ signals in cultures of fluo-4-loaded hBASMCs alongside measurements of intracellular cAMP using mass spectrometry or [3H]-adenine labeling. Interactions between the signaling pathways were examined using selective ligands of GPCRs, and inhibitors of Ca2+ and cAMP signaling pathways. Histamine stimulated Ca2+ release through inositol 1,4,5-trisphosphate (IP3) receptors in hBASMCs. β2-adrenoceptors, through cAMP and protein kinase A (PKA), substantially inhibited histamine-evoked Ca2+ signals. Responses to other Ca2+-mobilizing stimuli were unaffected by cAMP (carbachol and bradykinin) or minimally affected (lysophosphatidic acid). Prostaglandin E2 (PGE2), through EP2 and EP4 receptors, stimulated formation of cAMP and inhibited histamine-evoked Ca2+ signals. There was no consistent relationship between the inhibition of Ca2+ signals and the amounts of intracellular cAMP produced by different stimuli. We conclude that β-adrenoceptors, EP2 and EP4 receptors, through cAMP and PKA, selectively inhibit Ca2+ signals evoked by histamine in hBASMCs, suggesting that PKA inhibits an early step in H1 receptor signaling. Local delivery of cAMP within hyperactive signaling junctions mediates the inhibition.
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Affiliation(s)
- Philippa Dale
- Department of Pharmacology,Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Victoria Head
- Novartis Institutes for BioMedical Research, Fabrikstrasse, CH-4056, Basel, Switzerland
| | - Mark R Dowling
- Novartis Institutes for BioMedical Research Inc., 250 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Colin W Taylor
- Department of Pharmacology,Tennis Court Road, Cambridge, CB2 1PD, UK.
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26
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Keebler MV, Taylor CW. Endogenous signalling pathways and caged IP 3 evoke Ca 2+ puffs at the same abundant immobile intracellular sites. J Cell Sci 2017; 130:3728-3739. [PMID: 28893841 PMCID: PMC5702060 DOI: 10.1242/jcs.208520] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/04/2017] [Indexed: 12/18/2022] Open
Abstract
The building blocks of intracellular Ca2+ signals evoked by inositol 1,4,5-trisphosphate receptors (IP3Rs) are Ca2+ puffs, transient focal increases in Ca2+ concentration that reflect the opening of small clusters of IP3Rs. We use total internal reflection fluorescence microscopy and automated analyses to detect Ca2+ puffs evoked by photolysis of caged IP3 or activation of endogenous muscarinic receptors with carbachol in human embryonic kidney 293 cells. Ca2+ puffs evoked by carbachol initiated at an estimated 65±7 sites/cell, and the sites remained immobile for many minutes. Photolysis of caged IP3 evoked Ca2+ puffs at a similar number of sites (100±35). Increasing the carbachol concentration increased the frequency of Ca2+ puffs without unmasking additional Ca2+ release sites. By measuring responses to sequential stimulation with carbachol or photolysed caged IP3, we established that the two stimuli evoked Ca2+ puffs at the same sites. We conclude that IP3-evoked Ca2+ puffs initiate at numerous immobile sites and the sites become more likely to fire as the IP3 concentration increases; there is no evidence that endogenous signalling pathways selectively deliver IP3 to specific sites. Summary: Ca2+ puffs are the building blocks for IP3-evoked Ca2+ signals. Ca2+ puffs evoked by caged IP3 or via endogenous signalling pathways initiate at the same fixed intracellular sites.
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Affiliation(s)
- Michael V Keebler
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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Taylor EJA, Pantazaka E, Shelley KL, Taylor CW. Prostaglandin E 2 Inhibits Histamine-Evoked Ca 2+ Release in Human Aortic Smooth Muscle Cells through Hyperactive cAMP Signaling Junctions and Protein Kinase A. Mol Pharmacol 2017; 92:533-545. [PMID: 28877931 PMCID: PMC5635517 DOI: 10.1124/mol.117.109249] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 08/23/2017] [Indexed: 11/22/2022] Open
Abstract
In human aortic smooth muscle cells, prostaglandin E2 (PGE2) stimulates adenylyl cyclase (AC) and attenuates the increase in intracellular free Ca2+ concentration evoked by activation of histamine H1 receptors. The mechanisms are not resolved. We show that cAMP mediates inhibition of histamine-evoked Ca2+ signals by PGE2. Exchange proteins activated by cAMP were not required, but the effects were attenuated by inhibition of cAMP-dependent protein kinase (PKA). PGE2 had no effect on the Ca2+ signals evoked by protease-activated receptors, heterologously expressed muscarinic M3 receptors, or by direct activation of inositol 1,4,5-trisphosphate (IP3) receptors by photolysis of caged IP3. The rate of Ca2+ removal from the cytosol was unaffected by PGE2, but PGE2 attenuated histamine-evoked IP3 accumulation. Substantial inhibition of AC had no effect on the concentration-dependent inhibition of Ca2+ signals by PGE2 or butaprost (to activate EP2 receptors selectively), but it modestly attenuated responses to EP4 receptors, activation of which generated less cAMP than EP2 receptors. We conclude that inhibition of histamine-evoked Ca2+ signals by PGE2 occurs through “hyperactive signaling junctions,” wherein cAMP is locally delivered to PKA at supersaturating concentrations to cause uncoupling of H1 receptors from phospholipase C. This sequence allows digital signaling from PGE2 receptors, through cAMP and PKA, to histamine-evoked Ca2+ signals.
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Affiliation(s)
- Emily J A Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Evangelia Pantazaka
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Kathryn L Shelley
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
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Muller MS, Taylor CW. ATP evokes Ca 2+ signals in cultured foetal human cortical astrocytes entirely through G protein-coupled P2Y receptors. J Neurochem 2017; 142:876-885. [PMID: 28677119 PMCID: PMC5601250 DOI: 10.1111/jnc.14119] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 05/15/2017] [Accepted: 06/29/2017] [Indexed: 01/07/2023]
Abstract
Extracellular ATP plays important roles in coordinating the activities of astrocytes and neurons, and aberrant signalling is associated with neurodegenerative diseases. In rodents, ATP stimulates opening of Ca2+‐permeable channels formed by P2X receptor subunits in the plasma membrane. It is widely assumed, but not verified, that P2X receptors also evoke Ca2+ signals in human astrocytes. Here, we directly assess this hypothesis. We showed that cultured foetal cortical human astrocytes express mRNA for several P2X receptor subunits (P2X4, P2X5, P2X6) and G protein‐coupled P2Y receptors (P2Y1, P2Y2, P2Y6, P2Y11). In these astrocytes, ATP stimulated Ca2+ release from intracellular stores through IP3 receptors and store‐operated Ca2+ entry. These responses were entirely mediated by P2Y1 and P2Y2 receptors. Agonists of P2X receptors did not evoke Ca2+ signals, and nor did ATP when Ca2+ release from intracellular stores and store‐operated Ca2+ entry were inhibited. We conclude that ATP‐evoked Ca2+ signals in cultured human foetal astrocytes are entirely mediated by P2Y1 and P2Y2 receptors, with no contribution from P2X receptors. ![]()
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Affiliation(s)
- Margit S Muller
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, UK
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Babu Thillaiappan N, Chavda AP, Tovey SC, Prole DL, Taylor CW. Ca 2+ Signals Originate from Immobile IP 3 Receptors at ER-PM Junctions. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.2619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Abstract
Ca2+ and cAMP are ubiquitous intracellular messengers and interactions between them are commonplace. Here the effects of cAMP on inositol 1,4,5-trisphosphate receptors (IP3Rs) are briefly reviewed. All three subtypes of IP3R are phosphorylated by cAMP-dependent protein kinase (PKA). This potentiates IP3-evoked Ca2+ release through IP3R1 and IP3R2, but probably has little effect on IP3R3. In addition, cAMP can directly sensitize all three IP3R subtypes to IP3. The high concentrations of cAMP required for this PKA-independent modulation of IP3Rs is delivered to them within signalling junctions that include type 6 adenylyl cyclase and IP3R2.
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
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Kennedy AJ, Yang P, Read C, Kuc RE, Yang L, Taylor EJA, Taylor CW, Maguire JJ, Davenport AP. Chemerin Elicits Potent Constrictor Actions via Chemokine-Like Receptor 1 (CMKLR1), not G-Protein-Coupled Receptor 1 (GPR1), in Human and Rat Vasculature. J Am Heart Assoc 2016; 5:JAHA.116.004421. [PMID: 27742615 PMCID: PMC5121526 DOI: 10.1161/jaha.116.004421] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Circulating levels of chemerin are significantly higher in hypertensive patients and positively correlate with blood pressure. Chemerin activates chemokine-like receptor 1 (CMKLR1 or ChemR23) and is proposed to activate the "orphan" G-protein-coupled receptor 1 (GPR1), which has been linked with hypertension. Our aim was to localize chemerin, CMKLR1, and GPR1 in the human vasculature and determine whether 1 or both of these receptors mediate vasoconstriction. METHODS AND RESULTS Using immunohistochemistry and molecular biology in conduit arteries and veins and resistance vessels, we localized chemerin to endothelium, smooth muscle, and adventitia and found that CMKLR1 and GPR1 were widely expressed in smooth muscle. C9 (chemerin149-157) contracted human saphenous vein (pD2=7.30±0.31) and resistance arteries (pD2=7.05±0.54) and increased blood pressure in rats by 9.1±1.0 mm Hg at 200 nmol. Crucially, these in vitro and in vivo vascular actions were blocked by CCX832, which we confirmed to be highly selective for CMKLR1 over GPR1. C9 inhibited cAMP accumulation in human aortic smooth muscle cells and preconstricted rat aorta, consistent with the observed vasoconstrictor action. Downstream signaling was explored further and, compared to chemerin, C9 showed a bias factor=≈5000 for the Gi protein pathway, suggesting that CMKLR1 exhibits biased agonism. CONCLUSIONS Our data suggest that chemerin acts at CMKLR1, but not GPR1, to increase blood pressure. Chemerin has an established detrimental role in metabolic syndrome, and these direct vascular actions may contribute to hypertension, an additional risk factor for cardiovascular disease. This study provides proof of principle for the therapeutic potential of selective CMKLR1 antagonists.
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Affiliation(s)
- Amanda J Kennedy
- Experimental Medicine and Immunotherapeutics, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Peiran Yang
- Experimental Medicine and Immunotherapeutics, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Cai Read
- Experimental Medicine and Immunotherapeutics, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Rhoda E Kuc
- Experimental Medicine and Immunotherapeutics, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Lucy Yang
- Experimental Medicine and Immunotherapeutics, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Emily J A Taylor
- Department of Pharmacology, University of Cambridge, United Kingdom
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, United Kingdom
| | - Janet J Maguire
- Experimental Medicine and Immunotherapeutics, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Anthony P Davenport
- Experimental Medicine and Immunotherapeutics, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, University of Cambridge, United Kingdom
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Vibhute AM, Pushpanandan P, Varghese M, Koniecnzy V, Taylor CW, Sureshan KM. Synthesis of dimeric analogs of adenophostin A that potently evoke Ca 2+ release through IP 3 receptors. RSC Adv 2016; 6:86346-86351. [PMID: 28066549 PMCID: PMC5171214 DOI: 10.1039/c6ra19413c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 09/05/2016] [Indexed: 11/21/2022] Open
Abstract
Syntheses and Ca2+ release potentials of four dimeric analogs of adenophostin A (AdA) through activation of type 1 IP3R are reported. These analogs are full agonists of IP3R and are equipotent to AdA, the most potent agonist of IP3R.
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are tetrameric intracellular channels through which many extracellular stimuli initiate the Ca2+ signals that regulate diverse cellular responses. There is considerable interest in developing novel ligands of IP3R. Adenophostin A (AdA) is a potent agonist of IP3R and since some dimeric analogs of IP3R ligands are more potent than the corresponding monomer; we considered whether dimeric AdA analogs might provide agonists with increased potency. We previously synthesized traizolophostin, in which a simple triazole replaced the adenine of AdA, and showed it to be equipotent to AdA. Here, we used click chemistry to synthesize four homodimeric analogs of triazolophostin, connected by oligoethylene glycol chains of different lengths. We evaluated the potency of these analogs to release Ca2+ through type 1 IP3R and established that the newly synthesized dimers are equipotent to AdA and triazolophostin.
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Affiliation(s)
- Amol M Vibhute
- School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram , Kerala 695016 , India . ; http://kms514.wix.com/kmsgroup
| | - Poornenth Pushpanandan
- School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram , Kerala 695016 , India . ; http://kms514.wix.com/kmsgroup
| | - Maria Varghese
- School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram , Kerala 695016 , India . ; http://kms514.wix.com/kmsgroup
| | - Vera Koniecnzy
- Department of Pharmacology , University of Cambridge , Tennis Court Road , Cambridge , CB2 1PD , UK
| | - Colin W Taylor
- Department of Pharmacology , University of Cambridge , Tennis Court Road , Cambridge , CB2 1PD , UK
| | - Kana M Sureshan
- School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram , Kerala 695016 , India . ; http://kms514.wix.com/kmsgroup
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Chakraborty S, Deb BK, Chorna T, Konieczny V, Taylor CW, Hasan G. Mutant IP3 receptors attenuate store-operated Ca2+ entry by destabilizing STIM-Orai interactions in Drosophila neurons. J Cell Sci 2016; 129:3903-3910. [PMID: 27591258 PMCID: PMC5087660 DOI: 10.1242/jcs.191585] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 08/30/2016] [Indexed: 12/25/2022] Open
Abstract
Store-operated Ca2+ entry (SOCE) occurs when loss of Ca2+ from the endoplasmic reticulum (ER) stimulates the Ca2+ sensor, STIM, to cluster and activate the plasma membrane Ca2+ channel Orai (encoded by Olf186-F in flies). Inositol 1,4,5-trisphosphate receptors (IP3Rs, which are encoded by a single gene in flies) are assumed to regulate SOCE solely by mediating ER Ca2+ release. We show that in Drosophila neurons, mutant IP3R attenuates SOCE evoked by depleting Ca2+ stores with thapsigargin. In normal neurons, store depletion caused STIM and the IP3R to accumulate near the plasma membrane, association of STIM with Orai, clustering of STIM and Orai at ER–plasma-membrane junctions and activation of SOCE. These responses were attenuated in neurons with mutant IP3Rs and were rescued by overexpression of STIM with Orai. We conclude that, after depletion of Ca2+ stores in Drosophila, translocation of the IP3R to ER–plasma-membrane junctions facilitates the coupling of STIM to Orai that leads to activation of SOCE. Summary: In Drosophila neurons, mutant IP3 receptors disrupt store-operated Ca2+ entry by destabilizing interaction of STIM with the Ca2+ channel, Orai. The interactions could coordinate store emptying with Ca2+ entry.
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Affiliation(s)
- Sumita Chakraborty
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bellary Road, Bangalore 560065, India Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Bipan K Deb
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bellary Road, Bangalore 560065, India
| | - Tetyana Chorna
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bellary Road, Bangalore 560065, India
| | - Vera Konieczny
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bellary Road, Bangalore 560065, India
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Srivats S, Balasuriya D, Pasche M, Vistal G, Edwardson JM, Taylor CW, Murrell-Lagnado RD. Sigma1 receptors inhibit store-operated Ca 2+ entry by attenuating coupling of STIM1 to Orai1. J Gen Physiol 2016. [DOI: 10.1085/jgp.1475oia26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Srivats S, Balasuriya D, Pasche M, Vistal G, Edwardson JM, Taylor CW, Murrell-Lagnado RD. Sigma1 receptors inhibit store-operated Ca2+ entry by attenuating coupling of STIM1 to Orai1. J Cell Biol 2016; 213:65-79. [PMID: 27069021 PMCID: PMC4828687 DOI: 10.1083/jcb.201506022] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Accepted: 02/24/2016] [Indexed: 11/24/2022] Open
Abstract
Sigma1 receptors (σ1Rs) are expressed widely; they bind diverse ligands, including psychotropic drugs and steroids, regulate many ion channels, and are implicated in cancer and addiction. It is not known how σ1Rs exert such varied effects. We demonstrate that σ1Rs inhibit store-operated Ca(2+)entry (SOCE), a major Ca(2+)influx pathway, and reduce the Ca(2+)content of the intracellular stores. SOCE was inhibited by expression of σ1R or an agonist of σ1R and enhanced by loss of σ1R or an antagonist. Within the endoplasmic reticulum (ER), σ1R associated with STIM1, the ER Ca(2+)sensor that regulates SOCE. This interaction was modulated by σ1R ligands. After depletion of Ca(2+)stores, σ1R accompanied STIM1 to ER-plasma membrane (PM) junctions where STIM1 stimulated opening of the Ca(2+)channel, Orai1. The association of STIM1 with σ1R slowed the recruitment of STIM1 to ER-PM junctions and reduced binding of STIM1 to PM Orai1. We conclude that σ1R attenuates STIM1 coupling to Orai1 and thereby inhibits SOCE.
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Affiliation(s)
- Shyam Srivats
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, England, UK
| | - Dilshan Balasuriya
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, England, UK
| | - Mathias Pasche
- MRC Laboratory for Molecular Biology, Cambridge CB2 0QH, England, UK
| | - Gerard Vistal
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, England, UK
| | - J Michael Edwardson
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, England, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, England, UK
| | - Ruth D Murrell-Lagnado
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, England, UK Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton BN1 9QG, England, UK
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Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors are the channels responsible for Ca(2+)release from the endoplasmic and sarcoplasmic reticulum. Research inScience Signalingby Alzayadyet al show that all four IP3-binding sites within the tetrameric IP3R must bind IP3before the channel can open, which has important consequences for the distribution of both IP3and IP3R activity within cells.
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK.
| | - Vera Konieczny
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
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Abstract
IP3R initiate most cellular Ca2+ signaling. AdA is the most potent agonist of IP3R. The structural complexity of AdA makes synthesis of its analogs cumbersome. We report an easy method for generating a library of potent triazole-based analogs of AdA, triazolophostins, which are the most potent AdA analogs devoid of a nucleobase.
IP3 receptors are channels that mediate the release of Ca2+ from the intracellular stores of cells stimulated by hormones or neurotransmitters. Adenophostin A (AdA) is the most potent agonist of IP3 receptors, with the β-anomeric adenine contributing to the increased potency. The potency of AdA and its stability towards the enzymes that degrade IP3 have aroused interest in AdA analogs for biological studies. The complex structure of AdA poses problems that have necessitated optimization of synthetic conditions for each analog. Such lengthy one-at-a-time syntheses limit access to AdA analogs. We have addressed this problem by synthesizing a library of triazole-based AdA analogs, triazolophostins, by employing click chemistry. An advanced intermediate having all the necessary phosphates and a β-azide at the anomeric position was reacted with various alkynes under Cu(i) catalysis to yield triazoles, which upon deprotection gave triazolophostins. All eleven triazolophostins synthesized are more potent than IP3 and some are equipotent with AdA in functional analyses of IP3 receptors. We show that a triazole ring can replace adenine without compromising the potency of AdA and provide facile routes to novel AdA analogs.
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Affiliation(s)
- Amol M Vibhute
- School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala-695016, India.
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Konieczny V, Stefanakis JG, Sitsanidis ED, Ioannidou NAT, Papadopoulos NV, Fylaktakidou KC, Taylor CW, Koumbis AE. Synthesis of inositol phosphate-based competitive antagonists of inositol 1,4,5-trisphosphate receptors. Org Biomol Chem 2016; 14:2504-14. [PMID: 26818818 DOI: 10.1039/c5ob02623g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are intracellular Ca(2+) channels that are widely expressed in animal cells, where they mediate the release of Ca(2+) from intracellular stores evoked by extracellular stimuli. A diverse array of synthetic agonists of IP3Rs has defined structure-activity relationships, but existing antagonists have severe limitations. We combined analyses of Ca(2+) release with equilibrium competition binding to IP3R to show that (1,3,4,6)IP4 is a full agonist of IP3R1 with lower affinity than (1,4,5)IP3. Systematic manipulation of this meso-compound via a versatile synthetic scheme provided a family of dimeric analogs of 2-O-butyryl-(1,3,4,6)IP4 and (1,3,4,5,6)IP5 that compete with (1,4,5)IP3 for binding to IP3R without evoking Ca(2+) release. These novel analogs are the first inositol phosphate-based competitive antagonists of IP3Rs with affinities comparable to that of the only commonly used competitive antagonist, heparin, the utility of which is limited by off-target effects.
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Affiliation(s)
- Vera Konieczny
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK.
| | - John G Stefanakis
- Laboratory of Organic Chemistry, Chemistry Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
| | - Efstratios D Sitsanidis
- Laboratory of Organic Chemistry, Chemistry Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
| | - Natalia-Anastasia T Ioannidou
- Laboratory of Organic Chemistry, Chemistry Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
| | - Nikolaos V Papadopoulos
- Laboratory of Organic Chemistry, Chemistry Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
| | - Konstantina C Fylaktakidou
- Laboratory of Organic, Bioorganic and Natural Product Chemistry, Molecular Biology and Genetics Department, Democritus University of Thrace, 68100 Alexandroupolis, Greece
| | - Colin W Taylor
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK.
| | - Alexandros E Koumbis
- Laboratory of Organic Chemistry, Chemistry Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
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Prole DL, Taylor CW. Inositol 1,4,5-trisphosphate receptors and their protein partners as signalling hubs. J Physiol 2016; 594:2849-66. [PMID: 26830355 PMCID: PMC4887697 DOI: 10.1113/jp271139] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 11/06/2015] [Indexed: 01/26/2023] Open
Abstract
Inositol 1,4,5‐trisphosphate receptors (IP3Rs) are expressed in nearly all animal cells, where they mediate the release of Ca2+ from intracellular stores. The complex spatial and temporal organization of the ensuing intracellular Ca2+ signals allows selective regulation of diverse physiological responses. Interactions of IP3Rs with other proteins contribute to the specificity and speed of Ca2+ signalling pathways, and to their capacity to integrate information from other signalling pathways. In this review, we provide a comprehensive survey of the proteins proposed to interact with IP3Rs and the functional effects that these interactions produce. Interacting proteins can determine the activity of IP3Rs, facilitate their regulation by multiple signalling pathways and direct the Ca2+ that they release to specific targets. We suggest that IP3Rs function as signalling hubs through which diverse inputs are processed and then emerge as cytosolic Ca2+ signals.
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Affiliation(s)
- David L Prole
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD, UK
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Geyer M, Huang F, Sun Y, Vogel SM, Malik AB, Taylor CW, Komarova YA. Microtubule-Associated Protein EB3 Regulates IP3 Receptor Clustering and Ca(2+) Signaling in Endothelial Cells. Cell Rep 2015; 12:79-89. [PMID: 26119739 PMCID: PMC4487770 DOI: 10.1016/j.celrep.2015.06.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 03/27/2015] [Accepted: 05/31/2015] [Indexed: 01/12/2023] Open
Abstract
The mechanisms by which the microtubule cytoskeleton regulates the permeability of endothelial barrier are not well understood. Here, we demonstrate that microtubule-associated end-binding protein 3 (EB3), a core component of the microtubule plus-end protein complex, binds to inositol 1,4,5-trisphosphate receptors (IP3Rs) through an S/TxIP EB-binding motif. In endothelial cells, α-thrombin, a pro-inflammatory mediator that stimulates phospholipase Cβ, increases the cytosolic Ca(2+) concentration and elicits clustering of IP3R3s. These responses, and the resulting Ca(2+)-dependent phosphorylation of myosin light chain, are prevented by depletion of either EB3 or mutation of the TxIP motif of IP3R3 responsible for mediating its binding to EB3. We also show that selective EB3 gene deletion in endothelial cells of mice abrogates α-thrombin-induced increase in endothelial permeability. We conclude that the EB3-mediated interaction of IP3Rs with microtubules controls the assembly of IP3Rs into effective Ca(2+) signaling clusters, which thereby regulate microtubule-dependent endothelial permeability.
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Affiliation(s)
- Melissa Geyer
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Fei Huang
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Ying Sun
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Stephen M Vogel
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Asrar B Malik
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK
| | - Yulia A Komarova
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA.
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Carrara G, Saraiva N, Parsons M, Byrne B, Prole DL, Taylor CW, Smith GL. Golgi anti-apoptotic proteins are highly conserved ion channels that affect apoptosis and cell migration. J Biol Chem 2015; 290:11785-801. [PMID: 25713081 PMCID: PMC4416878 DOI: 10.1074/jbc.m115.637306] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Indexed: 12/03/2022] Open
Abstract
Golgi anti-apoptotic proteins (GAAPs) are multitransmembrane proteins that are expressed in the Golgi apparatus and are able to homo-oligomerize. They are highly conserved throughout eukaryotes and are present in some prokaryotes and orthopoxviruses. Within eukaryotes, GAAPs regulate the Ca2+ content of intracellular stores, inhibit apoptosis, and promote cell adhesion and migration. Data presented here demonstrate that purified viral GAAPs (vGAAPs) and human Bax inhibitor 1 form ion channels and that vGAAP from camelpox virus is selective for cations. Mutagenesis of vGAAP, including some residues conserved in the recently solved structure of a related bacterial protein, BsYetJ, altered the conductance (E207Q and D219N) and ion selectivity (E207Q) of the channel. Mutation of residue Glu-207 or -178 reduced the effects of GAAP on cell migration and adhesion without affecting protection from apoptosis. In contrast, mutation of Asp-219 abrogated the anti-apoptotic activity of GAAP but not its effects on cell migration and adhesion. These results demonstrate that GAAPs are ion channels and define residues that contribute to the ion-conducting pore and affect apoptosis, cell adhesion, and migration independently.
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Affiliation(s)
- Guia Carrara
- From the Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
| | - Nuno Saraiva
- From the Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
| | - Maddy Parsons
- the Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom
| | - Bernadette Byrne
- the Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, United Kingdom, and
| | - David L Prole
- the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom,
| | - Colin W Taylor
- the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom,
| | - Geoffrey L Smith
- From the Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom,
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Saleem H, Tovey SC, Molinski TF, Taylor CW. Interactions of antagonists with subtypes of inositol 1,4,5-trisphosphate (IP3) receptor. Br J Pharmacol 2015; 171:3298-312. [PMID: 24628114 PMCID: PMC4080982 DOI: 10.1111/bph.12685] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 02/26/2014] [Accepted: 03/05/2014] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND AND PURPOSE Inositol 1,4,5-trisphosphate receptors (IP3Rs) are intracellular Ca2+ channels. Interactions of the commonly used antagonists of IP3Rs with IP3R subtypes are poorly understood. EXPERIMENTAL APPROACH IP3-evoked Ca2+ release from permeabilized DT40 cells stably expressing single subtypes of mammalian IP3R was measured using a luminal Ca2+ indicator. The effects of commonly used antagonists on IP3-evoked Ca2+ release and 3H-IP3 binding were characterized. KEY RESULTS Functional analyses showed that heparin was a competitive antagonist of all IP3R subtypes with different affinities for each (IP3R3 > IP3R1 ≥ IP3R2). This sequence did not match the affinities for heparin binding to the isolated N-terminal from each IP3R subtype. 2-aminoethoxydiphenyl borate (2-APB) and high concentrations of caffeine selectively inhibited IP3R1 without affecting IP3 binding. Neither Xestospongin C nor Xestospongin D effectively inhibited IP3-evoked Ca2+ release via any IP3R subtype. CONCLUSIONS AND IMPLICATIONS Heparin competes with IP3, but its access to the IP3-binding core is substantially hindered by additional IP3R residues. These interactions may contribute to its modest selectivity for IP3R3. Practicable concentrations of caffeine and 2-APB inhibit only IP3R1. Xestospongins do not appear to be effective antagonists of IP3Rs.
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Affiliation(s)
- Huma Saleem
- Department of Pharmacology, University of Cambridge, Cambridge, UK
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Meena A, Tovey SC, Taylor CW. Sustained signalling by PTH modulates IP3 accumulation and IP3 receptors through cyclic AMP junctions. J Cell Sci 2014; 128:408-20. [PMID: 25431134 PMCID: PMC4294780 DOI: 10.1242/jcs.163071] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Parathyroid hormone (PTH) stimulates adenylyl cyclase through type 1 PTH receptors (PTH1R) and potentiates the Ca2+ signals evoked by carbachol, which stimulates formation of inositol 1,4,5-trisphosphate (IP3). We confirmed that in HEK cells expressing PTH1R, acute stimulation with PTH(1-34) potentiated carbachol-evoked Ca2+ release. This was mediated by locally delivered cyclic AMP (cAMP), but unaffected by inhibition of protein kinase A (PKA), exchange proteins activated by cAMP, cAMP phosphodiesterases (PDEs) or substantial inhibition of adenylyl cyclase. Sustained stimulation with PTH(1-34) causes internalization of PTH1R–adenylyl cyclase signalling complexes, but the consequences for delivery of cAMP to IP3R within cAMP signalling junctions are unknown. Here, we show that sustained stimulation with PTH(1-34) or with PTH analogues that do not evoke receptor internalization reduced the potentiated Ca2+ signals and attenuated carbachol-evoked increases in cytosolic IP3. Similar results were obtained after sustained stimulation with NKH477 to directly activate adenylyl cyclase, or with the membrane-permeant analogue of cAMP, 8-Br-cAMP. These responses were independent of PKA and unaffected by substantial inhibition of adenylyl cyclase. During prolonged stimulation with PTH(1-34), hyperactive cAMP signalling junctions, within which cAMP is delivered directly and at saturating concentrations to its targets, mediate sensitization of IP3R and a more slowly developing inhibition of IP3 accumulation.
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Affiliation(s)
- Abha Meena
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD, UK
| | - Stephen C Tovey
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD, UK
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Abstract
Inositol 1,4,5-trisphosphate (IP3) evokes release of Ca2+ from the endoplasmic reticulum (ER), but the resulting Ca2+ signals are shaped by interactions with additional intracellular organelles. Bafilomycin A1, which prevents lysosomal Ca2+ uptake by inhibiting H+ pumping into lysosomes, increased the amplitude of the initial Ca2+ signals evoked by carbachol in human embryonic kidney (HEK) cells. Carbachol alone and carbachol in combination with parathyroid hormone (PTH) evoke Ca2+ release from distinct IP3-sensitive Ca2+ stores in HEK cells stably expressing human type 1 PTH receptors. Bafilomycin A1 similarly exaggerated the Ca2+ signals evoked by carbachol or carbachol with PTH, indicating that Ca2+ released from distinct IP3-sensitive Ca2+ stores is sequestered by lysosomes. The Ca2+ signals resulting from store-operated Ca2+ entry, whether evoked by thapsigargin or carbachol, were unaffected by bafilomycin A1. Using Gd3+ (1 mM) to inhibit both Ca2+ entry and Ca2+ extrusion, HEK cells were repetitively stimulated with carbachol to assess the effectiveness of Ca2+ recycling to the ER after IP3-evoked Ca2+ release. Blocking lysosomal Ca2+ uptake with bafilomycin A1 increased the amplitude of each carbachol-evoked Ca2+ signal without affecting the rate of Ca2+ recycling to the ER. This suggests that Ca2+ accumulated by lysosomes is rapidly returned to the ER. We conclude that lysosomes rapidly, reversibly and selectively accumulate the Ca2+ released by IP3 receptors residing within distinct Ca2+ stores, but not the Ca2+ entering cells via receptor-regulated, store-operated Ca2+ entry pathways.
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Affiliation(s)
| | - Stephen C. Tovey
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Colin W. Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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Pantazaka E, Taylor EJA, Bernard WG, Taylor CW. Ca(2+) signals evoked by histamine H1 receptors are attenuated by activation of prostaglandin EP2 and EP4 receptors in human aortic smooth muscle cells. Br J Pharmacol 2014; 169:1624-34. [PMID: 23638853 PMCID: PMC3724117 DOI: 10.1111/bph.12239] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 04/19/2013] [Accepted: 04/25/2013] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND AND PURPOSE Histamine and prostaglandin E2 (PGE2 ), directly and via their effects on other cells, regulate the behaviour of vascular smooth muscle (VSM), but their effects on human VSM are incompletely resolved. EXPERIMENTAL APPROACH The effects of PGE2 on histamine-evoked changes in intracellular free Ca(2+) concentration ([Ca(2+) ]i ) and adenylyl cyclase activity were measured in populations of cultured human aortic smooth muscle cells (ASMCs). Selective ligands of histamine and EP receptors were used to identify the receptors that mediate the responses. KEY RESULTS Histamine, via H1 receptors, stimulates an increase in [Ca(2+) ]i that is entirely mediated by activation of inositol 1,4,5-trisphosphate receptors. Selective stimulation of EP2 or EP4 receptors attenuates histamine-evoked Ca(2+) signals, but the effects of PGE2 on both Ca(2+) signals and AC activity are largely mediated by EP2 receptors. CONCLUSIONS AND IMPLICATIONS Two important inflammatory mediators, histamine via H1 receptors and PGE2 acting largely via EP2 receptors, exert opposing effects on [Ca(2+) ]i in human ASMCs.
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Thurley K, Tovey SC, Moenke G, Prince VL, Meena A, Thomas AP, Skupin A, Taylor CW, Falcke M. Reliable encoding of stimulus intensities within random sequences of intracellular Ca2+ spikes. Sci Signal 2014; 7:ra59. [PMID: 24962706 DOI: 10.1126/scisignal.2005237] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ca(2+) is a ubiquitous intracellular messenger that regulates diverse cellular activities. Extracellular stimuli often evoke sequences of intracellular Ca(2+) spikes, and spike frequency may encode stimulus intensity. However, the timing of spikes within a cell is random because each interspike interval has a large stochastic component. In human embryonic kidney (HEK) 293 cells and rat primary hepatocytes, we found that the average interspike interval also varied between individual cells. To evaluate how individual cells reliably encoded stimuli when Ca(2+) spikes exhibited such unpredictability, we combined Ca(2+) imaging of single cells with mathematical analyses of the Ca(2+) spikes evoked by receptors that stimulate formation of inositol 1,4,5-trisphosphate (IP3). This analysis revealed that signal-to-noise ratios were improved by slow recovery from feedback inhibition of Ca(2+) spiking operating at the whole-cell level and that they were robust against perturbations of the signaling pathway. Despite variability in the frequency of Ca(2+) spikes between cells, steps in stimulus intensity caused the stochastic period of the interspike interval to change by the same factor in all cells. These fold changes reliably encoded changes in stimulus intensity, and they resulted in an exponential dependence of average interspike interval on stimulation strength. We conclude that Ca(2+) spikes enable reliable signaling in a cell population despite randomness and cell-to-cell variability, because global feedback reduces noise, and changes in stimulus intensity are represented by fold changes in the stochastic period of the interspike interval.
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Affiliation(s)
- Kevin Thurley
- Mathematical Cell Physiology, Max Delbrück Center for Molecular Medicine, Robert Rössle Straße 10, Berlin 13125, Germany. Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK. Institute for Theoretical Biology, Charité-Universitätsmedizin Berlin, Invalidenstraße 43, Berlin 10115, Germany
| | - Stephen C Tovey
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Gregor Moenke
- Mathematical Cell Physiology, Max Delbrück Center for Molecular Medicine, Robert Rössle Straße 10, Berlin 13125, Germany
| | - Victoria L Prince
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Abha Meena
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Andrew P Thomas
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Alexander Skupin
- Luxembourg Centre for Systems Biomedicine, 7 Avenue des Hauts Fourneaux, Esch sur Alzette 4362, Luxembourg. National Center for Microscopy and Imaging Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
| | - Martin Falcke
- Mathematical Cell Physiology, Max Delbrück Center for Molecular Medicine, Robert Rössle Straße 10, Berlin 13125, Germany. Department of Physics, Humboldt University Berlin, Newtonstraße 15, Berlin 12489, Germany.
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Thurley K, Tovey SC, Moenke G, Prince VL, Meena A, Thomas AP, Skupin A, Taylor CW, Falcke M. Reliable Encoding of Stimulus Intensities by Random Sequences of Ca2+ Spikes. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.1414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are intracellular Ca(2+) channels. They are expressed in most animal cells and mediate release of Ca(2+) from the endoplasmic reticulum (ER) in response to the many stimuli that evoke formation of inositol 1,4,5-trisphosphate (IP3). The opening of individual IP3Rs causes small, transient, local increases in cytosolic Ca(2+) concentration, and these events are the fundamental units of Ca(2+) signaling. These openings allow Ca(2+) signals to be selectively delivered by individual channels to the specific Ca(2+) sensors that evoke cellular responses. Stimulation of IP3Rs by the Ca(2+) they release allows these tiny events to grow into much larger ones by recruitment of neighboring IP3Rs. Understanding how Ca(2+) effectively and specifically regulates so many cellular processes demands an understanding of the interplay between IP3 and Ca(2+) in controlling IP3R gating. Here, we briefly set the scene before introducing high-throughput methods that seek to address this issue.
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
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Abstract
This protocol describes procedures for high-throughput functional analyses of inositol 1,4,5-trisphosphate receptors (IP3Rs) in permeabilized cells. The methods are applicable to native IP3Rs in a variety of cells and to recombinant IP3Rs stably expressed in DT40 cells in which gene disruption has abolished expression of endogenous IP3Rs. A low-affinity Ca(2+)-indicator (Mag-Fluo-4) trapped within the endoplasmic reticulum (ER) of permeabilized cells is used to report changes in luminal free Ca(2+) concentration. A fluorescence plate-reader equipped to allow automated additions permits rapid measurements of the Ca(2+) release evoked by IP3R. The procedure can be completed in 2-3 h.
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Affiliation(s)
- Stephen C Tovey
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
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50
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Abstract
Fluorescence polarization (FP) allows quantification of the binding of a small fluorescent ligand to a larger protein because the free ligand rotates more rapidly than the bound form. This protocol describes an FP assay for the binding of fluorescein-labeled inositol 1,4,5-trisphosphate (IP3) to amino-terminal fragments of the IP3 receptor at different temperatures and in the presence of competing ligands. The method requires fluorescein-labeled IP3 and a plate-reader capable of FP measurements. The assay can measure low-affinity interactions in real time, it avoids use of radioactive materials, is nondestructive, and can resolve changes in Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) that occur with ligand binding. It is applicable to any purified protein for which a fluorescent ligand is available. After optimization, the procedure can be completed in 1-6 h.
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Affiliation(s)
- Ana M Rossi
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
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