1
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Parys JB, Lemos FO. The interplay between associated proteins, redox state and Ca 2+ in the intraluminal ER compartment regulates the IP 3 receptor. Cell Calcium 2024; 117:102823. [PMID: 37976974 DOI: 10.1016/j.ceca.2023.102823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/06/2023] [Accepted: 11/08/2023] [Indexed: 11/19/2023]
Abstract
There have been in the last three decades repeated publications indicating that the inositol 1,4,5-trisphosphate receptor (IP3R) is regulated not only by cytosolic Ca2+ but also by intraluminal Ca2+. Although most studies indicated that a decreasing intraluminal Ca2+ level led to an inhibition of the IP3R, a number of publications reported exactly the opposite effect, i.e. an inhibition of the IP3R by high intraluminal Ca2+ levels. Although intraluminal Ca2+-binding sites on the IP3Rs were reported, a regulatory role for them was not demonstrated. It is also well known that the IP3R is regulated by a vast array of associated proteins, but only relatively recently proteins were identified that can be linked to the regulation of the IP3R by intraluminal Ca2+. The first to be reported was annexin A1 that is proposed to associate with the second intraluminal loop of the IP3R at high intraluminal Ca2+ levels and to inhibit the IP3R. More recently, ERdj5/PDIA19 reductase was described to reduce an intraluminal disulfide bridge of IP3R1 only at low intraluminal Ca2+ levels and thereby to inhibit the IP3R. Annexin A1 and ERdj5/PDIA19 can therefore explain most of the experimental results on the regulation of the IP3R by intraluminal Ca2+. Further studies are needed to provide a fuller understanding of the regulation of the IP3R from the intraluminal side. These findings underscore the importance of the state of the endoplasmic reticulum in the control of IP3R activity.
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Affiliation(s)
- Jan B Parys
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Leuven Kanker Instituut (LKI), Campus Gasthuisberg O&N1 - Box 802, Herestraat 49, B-3000, Leuven, Belgium.
| | - Fernanda O Lemos
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Leuven Kanker Instituut (LKI), Campus Gasthuisberg O&N1 - Box 802, Herestraat 49, B-3000, Leuven, Belgium
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2
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Quantal Ca 2+ release mediated by very few IP 3 receptors that rapidly inactivate allows graded responses to IP 3. Cell Rep 2021; 37:109932. [PMID: 34731613 PMCID: PMC8578705 DOI: 10.1016/j.celrep.2021.109932] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 07/16/2021] [Accepted: 10/12/2021] [Indexed: 11/22/2022] Open
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are intracellular Ca2+ channels that link extracellular stimuli to Ca2+ signals. Ca2+ release from intracellular stores is "quantal": low IP3 concentrations rapidly release a fraction of the stores. Ca2+ release then slows or terminates without compromising responses to further IP3 additions. The mechanisms are unresolved. Here, we synthesize a high-affinity partial agonist of IP3Rs and use it to demonstrate that quantal responses do not require heterogenous Ca2+ stores. IP3Rs respond incrementally to IP3 and close after the initial response to low IP3 concentrations. Comparing functional responses with IP3 binding shows that only a tiny fraction of a cell's IP3Rs mediate incremental Ca2+ release; inactivation does not therefore affect most IP3Rs. We conclude, and test by simulations, that Ca2+ signals evoked by IP3 pulses arise from rapid activation and then inactivation of very few IP3Rs. This allows IP3Rs to behave as increment detectors mediating graded Ca2+ release.
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3
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Mak DOD, Vais H, Cheung KH, Foskett JK. Patch-clamp electrophysiology of intracellular Ca2+ channels. Cold Spring Harb Protoc 2013; 2013:787-97. [PMID: 24003191 DOI: 10.1101/pdb.top066217] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The modulation of cytoplasmic free Ca(2+) concentration ([Ca(2+)]i) is a universal intracellular signaling pathway that regulates numerous cellular physiological processes. Ubiquitous intracellular Ca(2+)-release channels localized to the endoplasmic/sarcoplasmic reticulum-inositol 1,4,5-trisphosphate receptor (InsP3R) and ryanodine receptor (RyR) channels-play a central role in [Ca(2+)]i signaling in all animal cells. Despite their intracellular localization, electrophysiological studies of the single-channel permeation and gating properties of these Ca(2+)-release channels using the powerful patch-clamp approach have been possible by application of this technique to isolated nuclei because the channels are present in membranes of the nuclear envelope. Here we provide a concise description of how nuclear patch-clamp experiments have been used to study single-channel properties of different InsP3R channels in the outer nuclear membrane. We compare this with other methods for studying intracellular Ca(2+) release. We also briefly describe application of the technique to InsP3R channels in the inner nuclear membrane and to channels in the outer nuclear membrane of HEK293 cells expressing recombinant RyR.
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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4
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Vais H, Foskett JK, Ullah G, Pearson JE, Mak DOD. Permeant calcium ion feed-through regulation of single inositol 1,4,5-trisphosphate receptor channel gating. ACTA ACUST UNITED AC 2012; 140:697-716. [PMID: 23148262 PMCID: PMC3514735 DOI: 10.1085/jgp.201210804] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The ubiquitous inositol 1,4,5-trisphosphate (InsP(3)) receptor (InsP(3)R) Ca(2+) release channel plays a central role in the generation and modulation of intracellular Ca(2+) signals, and is intricately regulated by multiple mechanisms including cytoplasmic ligand (InsP(3), free Ca(2+), free ATP(4-)) binding, posttranslational modifications, and interactions with cytoplasmic and endoplasmic reticulum (ER) luminal proteins. However, regulation of InsP(3)R channel activity by free Ca(2+) in the ER lumen ([Ca(2+)](ER)) remains poorly understood because of limitations of Ca(2+) flux measurements and imaging techniques. Here, we used nuclear patch-clamp experiments in excised luminal-side-out configuration with perfusion solution exchange to study the effects of [Ca(2+)](ER) on homotetrameric rat type 3 InsP(3)R channel activity. In optimal [Ca(2+)](i) and subsaturating [InsP(3)], jumps of [Ca(2+)](ER) from 70 nM to 300 µM reduced channel activity significantly. This inhibition was abrogated by saturating InsP(3) but restored when [Ca(2+)](ER) was raised to 1.1 mM. In suboptimal [Ca(2+)](i), jumps of [Ca(2+)](ER) (70 nM to 300 µM) enhanced channel activity. Thus, [Ca(2+)](ER) effects on channel activity exhibited a biphasic dependence on [Ca(2+)](i). In addition, the effect of high [Ca(2+)](ER) was attenuated when a voltage was applied to oppose Ca(2+) flux through the channel. These observations can be accounted for by Ca(2+) flux driven through the open InsP(3)R channel by [Ca(2+)](ER), raising local [Ca(2+)](i) around the channel to regulate its activity through its cytoplasmic regulatory Ca(2+)-binding sites. Importantly, [Ca(2+)](ER) regulation of InsP(3)R channel activity depended on cytoplasmic Ca(2+)-buffering conditions: it was more pronounced when [Ca(2+)](i) was weakly buffered but completely abolished in strong Ca(2+)-buffering conditions. With strong cytoplasmic buffering and Ca(2+) flux sufficiently reduced by applied voltage, both activation and inhibition of InsP(3)R channel gating by physiological levels of [Ca(2+)](ER) were completely abolished. Collectively, these results rule out Ca(2+) regulation of channel activity by direct binding to the luminal aspect of the channel.
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Affiliation(s)
- Horia Vais
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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5
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Abstract
The calcium ion (Ca(2+)) is the simplest and most versatile intracellular messenger known. The discovery of Ca(2+) sparks and a related family of elementary Ca(2+) signaling events has revealed fundamental principles of the Ca(2+) signaling system. A newly appreciated "digital" subsystem consisting of brief, high Ca(2+) concentration over short distances (nanometers to microns) comingles with an "analog" global Ca(2+) signaling subsystem. Over the past 15 years, much has been learned about the theoretical and practical aspects of spark formation and detection. The quest for the spark mechanisms [the activation, coordination, and termination of Ca(2+) release units (CRUs)] has met unexpected challenges, however, and raised vexing questions about CRU operation in situ. Ample evidence shows that Ca(2+) sparks catalyze many high-threshold Ca(2+) processes involved in cardiac and skeletal muscle excitation-contraction coupling, vascular tone regulation, membrane excitability, and neuronal secretion. Investigation of Ca(2+) sparks in diseases has also begun to provide novel insights into hypertension, cardiac arrhythmias, heart failure, and muscular dystrophy. An emerging view is that spatially and temporally patterned activation of the digital subsystem confers on intracellular Ca(2+) signaling an exquisite architecture in space, time, and intensity, which underpins signaling efficiency, stability, specificity, and diversity. These recent advances in "sparkology" thus promise to unify the simplicity and complexity of Ca(2+) signaling in biology.
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Affiliation(s)
- Heping Cheng
- Institute of Molecular Medicine, National Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing, China.
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6
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Ionescu L, White C, Cheung KH, Shuai J, Parker I, Pearson JE, Foskett JK, Mak DOD. Mode switching is the major mechanism of ligand regulation of InsP3 receptor calcium release channels. ACTA ACUST UNITED AC 2007; 130:631-45. [PMID: 17998395 PMCID: PMC2151663 DOI: 10.1085/jgp.200709859] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) plays a critical role in generation of complex Ca2+ signals in many cell types. In patch clamp recordings of isolated nuclei from insect Sf9 cells, InsP3R channels were consistently detected with regulation by cytoplasmic InsP3 and free Ca2+ concentrations ([Ca2+]i) very similar to that observed for vertebrate InsP3R. Long channel activity durations of the Sf9-InsP3R have now enabled identification of a novel aspect of InsP3R gating: modal gating. Using a novel algorithm to analyze channel modal gating kinetics, InsP3R gating can be separated into three distinct modes: a low activity mode, a fast kinetic mode, and a burst mode with channel open probability (Po) within each mode of 0.007 ± 0.002, 0.24 ± 0.03, and 0.85 ± 0.02, respectively. Channels reside in each mode for long periods (tens of opening and closing events), and transitions between modes can be discerned with high resolution (within two channel opening and closing events). Remarkably, regulation of channel gating by [Ca2+]i and [InsP3] does not substantially alter channel Po within a mode. Instead, [Ca2+]i and [InsP3] affect overall channel Po primarily by changing the relative probability of the channel being in each mode, especially the high and low Po modes. This novel observation therefore reveals modal switching as the major mechanism of physiological regulation of InsP3R channel activity, with implications for the kinetics of Ca2+ release events in cells.
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Affiliation(s)
- Lucian Ionescu
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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7
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Erxleben C, Klauke N, Flötenmeyer M, Blanchard MP, Braun C, Plattner H. Microdomain Ca2+ activation during exocytosis in Paramecium cells. Superposition of local subplasmalemmal calcium store activation by local Ca2+ influx. J Cell Biol 1997; 136:597-607. [PMID: 9024690 PMCID: PMC2134299 DOI: 10.1083/jcb.136.3.597] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
In Paramecium tetraurelia, polyamine-triggered exocytosis is accompanied by the activation of Ca2+-activated currents across the cell membrane (Erxleben. C., and H. Plattner. 1994. J. Cell Biol. 127:935-945). We now show by voltage clamp and extracellular recordings that the product of current x time (As) closely parallels the number of exocytotic events. We suggest that Ca2+ mobilization from subplasmalemmal storage compartments, covering almost the entire cell surface, is a key event. In fact, after local stimulation, Ca2+ imaging with high time resolution reveals rapid, transient, local signals even when extracellular Ca2+ is quenched to or below resting intracellular Ca2+ concentration ([Ca2+]e, < or = [Ca2+]i). Under these conditions, quenched-flow/freeze-fracture analysis shows that membrane fusion is only partially inhibited. Increasing [Ca2+], alone, i.e., without secretagogue, causes rapid, strong cortical increase of [Ca2+]i but no exocytosis. In various cells, the ratio of maximal vs. minimal currents registered during maximal stimulation or single exocytotic events, respectively, correlate nicely with the number of Ca stores available. Since no quantal current steps could be observed, this is again compatible with the combined occurrence of Ca2+ mobilization from stores (providing close to threshold Ca2+ levels) and Ca2+ influx from the medium (which per se does not cause exocytosis). This implies that only the combination of Ca2+ flushes, primarily from internal and secondarily from external sources, can produce a signal triggering rapid, local exocytotic responses, as requested for Paramecium defense.
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Affiliation(s)
- C Erxleben
- Faculty of Biology, University of Konstanz, Germany
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8
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Kaimachnikov NP, Nazarenko VG. Quantal Ca2+ release and inactivation in a model of the inositol 1,4,5-trisphosphate receptor involving transformation of the ligand by the receptor. Biosci Rep 1996; 16:405-13. [PMID: 8913530 DOI: 10.1007/bf01207265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
A model explaining quantal Ca2+ release as an intrinsic property of the inositol 1,4,5-triphosphate (IP3) receptor has been put forward. The model is based on the hypothesis that the IP3 receptor can catalyze a transformation of the IP3 molecule differing from its conventional metabolism. A simple kinetic mechanism is considered, in which IP3-induced Ca2+ channel opening is followed by the step of IP3 conversion and channel closure. Examination of the resulting mathematical model shows that it can reproduce well both partial release of stored Ca2+ and the same responsiveness to subsequent IP3 additions. On incorporation of an additional closed state of the channel, the model describes also a time-dependent channel inactivation at a high IP3 dose. Temperature sensitivity of the catalytic step accounts for the reported elimination of quantal responses and inactivation at low temperature. The transformation product is surmised to be a positional or stereo isomer of IP3.
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Affiliation(s)
- N P Kaimachnikov
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
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9
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Missiaen L, De Smedt H, Parys JB, Raeymaekers L, Droogmans G, Van Den Bosch L, Casteels R. Kinetics of the non-specific calcium leak from non-mitochondrial calcium stores in permeabilized A7r5 cells. Biochem J 1996; 317 ( Pt 3):849-53. [PMID: 8760372 PMCID: PMC1217562 DOI: 10.1042/bj3170849] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have investigated the detailed kinetics of the passive Ca2+ leak from non-mitochondrial Ca2+ stores in permeabilized A7r5 cells. The decrease in the content of stored Ca2+ in the presence of 2 microM thapsigargin deviated from a single-exponential curve in the initial phase of the efflux. The deviation persisted after correcting this efflux for passively bound Ca2+. The non-single-exponential nature of the spontaneous release also occurred when the initial store Ca2+ content was reduced to 40% of its original value by pretreatment with 200 nM inositol 1,4,5-trisphosphate (InsP3). The passive Ca2+ leak could be modelled by two exponential curves with discrete rate constants of 0.06 min-1 and 0.98 min-1, and not by any other type of non-exponential decay. We concluded that individual store units are heterogeneous with respect to their passive Ca2+ permeability. This non-exponential nature of the passive Ca2+ release is unrelated to the non-single-exponential InsP3-induced Ca2+ release.
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Affiliation(s)
- L Missiaen
- Laboratorium voor Fysiologie, K.U. Leuven Campus Gasthuisberg, Belgium
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10
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Tanimura A, Turner RJ. Calcium release in HSY cells conforms to a steady-state mechanism involving regulation of the inositol 1,4,5-trisphosphate receptor Ca2+ channel by luminal [Ca2+]. J Cell Biol 1996; 132:607-16. [PMID: 8647892 PMCID: PMC2199877 DOI: 10.1083/jcb.132.4.607] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
In many cell types, low concentrations of inositol 1,4,5-trisphosphate (IP3) release only a portion of the intracellular IP3-sensitive Ca2+ store, a phenomenon known as "quantal" Ca2+ release. It has been suggested that this effect is a result of reduced activity of the IP3-dependent Ca2+ channel with decreasing calcium concentration within the IP3-sensitive store ([Ca2+]s). To test this hypothesis, the properties of IP3-dependent Ca2+ release in single saponin-permeabilized HSY cells were studied by monitoring [Ca2+]s using the Ca(2+)-sensitive fluorescent dye mag-fura-2. In permeabilized cells, blockade of the sarco/ER Ca(2+)-ATPase pump in stores partially depleted by IP3 induced further Ca2+ release via an IP3-dependent route, indicating that Ca2+ entry via the sarco/ER Ca(2+)-ATPase pump had been balanced by Ca2+ loss via the IP3-sensitive channel before pump inhibition. IP3-dependent Mn2+ entry, monitored via quenching of luminal mag-fura-2 fluorescence, was readily apparent in filled stores but undetectable in Ca(2+)-depleted stores, indicating markedly reduced IP3-sensitive channel activity in the latter. Also consistent with reduced responsiveness of Ca(2+)-depleted stores to IP3, the initial rate of refilling of these stores was unaffected by the presence of 0.3 microM IP3, a concentration that was clearly effective in eliciting Ca2+ release from filled stores. Analysis of the rate of Ca2+ release at various IP3 concentrations indicated a significant shift of the IP3 dose response toward higher [IP3] with decreasing [Ca2+]s. We conclude that IP3-dependent Ca2+ release in HSY cells is a steady-state process wherein Ca2+ efflux via the IP3 receptor Ca2+ channel is regulated by [Ca2+]s, apparently via changes in the sensitivity of the channel to IP3.
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Affiliation(s)
- A Tanimura
- Clinical Investigations and Patient Care Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892, USA
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11
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Missiaen L, Parys JB, De Smedt H, Sienaert I, Bootman MD, Casteels R. Control of the Ca2+ release induced by myo-inositol trisphosphate and the implication in signal transduction. Subcell Biochem 1996; 26:59-95. [PMID: 8744262 DOI: 10.1007/978-1-4613-0343-5_3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Affiliation(s)
- L Missiaen
- Laboratory for Physiology, Catholic University of Leuven, Belgium
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12
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Abstract
In current models describing agonist-induced oscillations in [Ca2+]i, Ca2+ entry is generally assumed to have a simple sustaining role, replenishing Ca2+ lost from the cell and recharging intracellular Ca2+ stores. In cells from the avian nasal gland, a model exocrine cell, we show that inhibition of Ca2+ entry by La3+, SK&F 96365, or by membrane depolarization, rapidly blocks [Ca2+]i oscillations but does so without detectable depletion of agonist-sensitive Ca2+ stores. As the rate of Mn2+ quenching during [Ca2+]i oscillations is constant, Ca2+ entry is not directly contributing to the [Ca2+]i changes and, instead, appears to be involved in inducing the repetitive release of Ca2+ from internal stores. Together, these data contradict current models in that (i) at the low agonist concentrations where [Ca2+]i oscillations are seen, generated levels of Ins(1,4,5)P3 are themselves inadequate to result in a regenerative [Ca2+]i signal, and (ii) Ca2+ entry is necessary to actually drive the intrinsic oscillatory mechanism.
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Affiliation(s)
- S C Martin
- Department of Physiology, University of Rochester School of Medicine and Dentistry, NY 14642
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13
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Cheek TR, Berridge MJ, Moreton RB, Stauderman KA, Murawsky MM, Bootman MD. Quantal Ca2+ mobilization by ryanodine receptors is due to all-or-none release from functionally discrete intracellular stores. Biochem J 1994; 301 ( Pt 3):879-83. [PMID: 8053911 PMCID: PMC1137068 DOI: 10.1042/bj3010879] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Low caffeine concentrations were unable to completely release the caffeine- and ryanodine-sensitive intracellular Ca2+ pool in intact adrenal chromaffin cells. This 'quantal' Ca2+ release is the same as that previously observed with inositol Ins(1,4,5)P3-induced Ca2+ release. The molecular mechanism underlying quantal Ca2+ release from the ryanodine receptor was investigated using fura-2 imaging of single chromaffin cells. Our data indicate that the intracellular caffeine-sensitive Ca2+ pool is composed of functionally discrete stores, that possess heterogeneous sensitivities to caffeine. These stores are mobilized by caffeine in a concentration-dependent fashion, and, when stimulated, individual stores release their Ca2+ in an 'all-or-none' manner. Such quantal Ca2+ release may be responsible for graded Ca2+ responses in single cells.
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Affiliation(s)
- T R Cheek
- Department of Zoology, University of Cambridge, U.K
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14
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Røtnes JS, Bogen B. Ca2+ mobilization in physiologically stimulated single T cells gradually increases with peptide concentration (analog signaling). Eur J Immunol 1994; 24:851-8. [PMID: 8149956 DOI: 10.1002/eji.1830240412] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have investigated Ca2+ mobilization in single T cells stimulated with their physiological ligand, i.e. antigenic peptide bound to major histocompatibility complex (MHC) molecules on antigen-presenting cells (APC). Fibroblasts expressing I-Ed class II molecules were pulsed with a peptide derived from the lambda 2(315) immunoglobulin light chain. Onto such antigen-pulsed fibroblasts were sedimented cloned Th1 cells loaded with Fura-2. Changes in cytosolic Ca2+ concentration in single T cells were continually monitored by use of an imaging system based on fluorometry. Ca2+ mobilization was both peptide-specific and MHC-restricted. Within seconds of the initial APC-T cell contact, a Ca2+ spike could be observed. The Ca2+ response gradually declined over a 25-min period, during which oscillations were noted. Various parameters characterizing the magnitude of the Ca2+ response (latency, increase rate, max and mean Ca2+ increase, frequency and period of oscillations) all correlated with the amount of peptide used for pulsing the fibroblasts. Thus, Ca2+ mobilization in single T cells appears not to be an all or none phenomenon. Rather, activation is incremental (analog signaling), the degree of Ca2+ mobilization probably being related to the number of stimulatory peptide-MHC complexes on the surface of the APC. The extent of calcium mobilization and lymphokine production (interleukin (IL)-2, IL-3, interferon-gamma) correlated, at least at the population level.
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Affiliation(s)
- J S Røtnes
- Institute of Physiology, University of Oslo, Norway
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15
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Missiaen L, De Smedt H, Parys J, Casteels R. Co-activation of inositol trisphosphate-induced Ca2+ release by cytosolic Ca2+ is loading-dependent. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37273-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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16
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Cheek TR, Moreton RB, Berridge MJ, Stauderman KA, Murawsky MM, Bootman MD. Quantal Ca2+ release from caffeine-sensitive stores in adrenal chromaffin cells. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74220-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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17
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Parys JB, Missiaen L, De Smedt H, Casteels R. Loading dependence of inositol 1,4,5-trisphosphate-induced Ca2+ release in the clonal cell line A7r5. Implications for the mechanism of quantal Ca2+ release. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74589-x] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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18
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Parys JB, Missiaen L, De Smedt H, Droogmans G, Casteels R. Bell-shaped activation of inositol-1,4,5-trisphosphate-induced Ca2+ release by thimerosal in permeabilized A7r5 smooth-muscle cells. Pflugers Arch 1993; 424:516-22. [PMID: 8255736 DOI: 10.1007/bf00374916] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
There is no consensus about the different types of Ca2+ transport processes in the endoplasmic reticulum that are targeted by the sulphydryl reagent thimerosal. We have therefore investigated how thimerosal affects the various Ca2+ transport processes in permeabilized A7r5 smooth-muscle cells, using an unidirectional 45Ca2+ flux technique. Thimerosal up to a concentration of 32 microM did not have an effect on the passive 45Ca2+ leak from the stores, while higher concentrations increased this aspecific leak. Thimerosal inhibited the endoplasmic reticulum Ca2+ pump with an EC50 of 9 microM. Thimerosal exerted a biphasic effect on the Ca2+ release induced by inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] with a stimulation of the release at thimerosal concentrations below 10 microM, and an inhibitory effect at higher concentrations. Thimerosal (2.5-250 microM) did not exert an effect on the specific binding of [3H]Ins(1,4,5)P3 to its receptor, indicating that it probably did not act at the level of the binding site. This finding contrasts with the effect of the closely related sulphydryl reagent parachloromercuriphenylsulphonate, which, at high concentrations, inhibited [3H]Ins(1,4,5)P3 binding. The effects of thimerosal were largely prevented by the sulphydryl reducing agent dithiothreitol (3 mM). We conclude that thimerosal concentrations ranging from 0.32 to 1 microM can stimulate the Ins(1,4,5)P3-induced Ca2+ release without inhibiting the Ca2+ pumps or without increasing the passive Ca2+ permeability of the endoplasmic reticulum.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium Channels/metabolism
- Cell Line
- Cell Membrane Permeability
- Dithiothreitol/pharmacology
- Dose-Response Relationship, Drug
- Endoplasmic Reticulum/metabolism
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors
- Kinetics
- Mitochondria/metabolism
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Rats
- Receptors, Cytoplasmic and Nuclear/metabolism
- Sulfhydryl Compounds/pharmacology
- Thimerosal/pharmacology
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Affiliation(s)
- J B Parys
- Laboratorium voor Fysiologie, K. U. Leuven, Belgium
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19
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Abstract
Inositol trisphosphate is a second messenger that controls many cellular processes by generating internal calcium signals. It operates through receptors whose molecular and physiological properties closely resemble the calcium-mobilizing ryanodine receptors of muscle. This family of intracellular calcium channels displays the regenerative process of calcium-induced calcium release responsible for the complex spatiotemporal patterns of calcium waves and oscillations. Such a dynamic signalling pathway controls many cellular processes, including fertilization, cell growth, transformation, secretion, smooth muscle contraction, sensory perception and neuronal signalling.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium/physiology
- Calcium Channels
- Cell Cycle
- Cell Division
- Cell Transformation, Neoplastic
- Female
- Fertilization
- GTP-Binding Proteins/physiology
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate/physiology
- Inositol 1,4,5-Trisphosphate Receptors
- Male
- Models, Biological
- Neuronal Plasticity
- Protein-Tyrosine Kinases/metabolism
- Receptors, Cell Surface/physiology
- Receptors, Cholinergic/physiology
- Receptors, Cytoplasmic and Nuclear
- Ryanodine/pharmacology
- Ryanodine Receptor Calcium Release Channel
- Second Messenger Systems
- Signal Transduction
- Synapses/physiology
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Affiliation(s)
- M J Berridge
- AFRC Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge, UK
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20
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Missiaen L, Taylor CW, Berridge MJ. Luminal Ca2+ promoting spontaneous Ca2+ release from inositol trisphosphate-sensitive stores in rat hepatocytes. J Physiol 1992; 455:623-40. [PMID: 1484365 PMCID: PMC1175662 DOI: 10.1113/jphysiol.1992.sp019319] [Citation(s) in RCA: 117] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
1. Spontaneous Ca2+ release from the inositol 1,4,5-trisphosphate (InsP3)-sensitive stores in permeabilized hepatocytes was monitored using Fluo-3 to measure the free [Ca2+] of the medium bathing the cells. 2. Permeabilized cells rapidly sequestered Ca2+, reducing the [Ca2+] to 103 +/- 5 nM. Under conditions that depended critically upon cell density and the amount of Ca2+ in the medium, this was followed by a slow increase in [Ca2+] culminating in a substantial Ca2+ spike representing synchronous discharge from the InsP3-sensitive stores. 3. During the latency preceding the Ca2+ spike, the stores increased their sensitivity to InsP3. This sensitization seemed to be an all-or-none phenomenon. 4. Oxidized glutathione and thimerosal promoted the spontaneous release by sensitizing the InsP3 receptor. 5. An increase in the [Ca2+] within the stores was required for both the increased sensitivity to InsP3 and the subsequent spike. 6. Caffeine (6 mM) antagonized the effect of very low InsP3 concentrations and abolished the Ca2+ spike, without itself releasing Ca2+. 7. Our results suggesting that luminal Ca2+ may sensitive InsP3-sensitive stores leading to spontaneous Ca2+ mobilization will be discussed in the light of a modified version of the two-pool model for explaining cytosolic Ca2+ oscillations.
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Affiliation(s)
- L Missiaen
- AFRC Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge
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21
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Berman DM, Goldman WF. Stored calcium modulates inositol phosphate synthesis in cultured smooth muscle cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1992; 263:C535-9. [PMID: 1514595 DOI: 10.1152/ajpcell.1992.263.2.c535] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cytosolic Ca2+ concentrations ([Ca2+]cyt) and [3H]inositol phosphates ([3H]InsP) were correlated while varying the Ca2+ content of the sarcoplasmic reticulum (SR) in cultured A7r5 cells at rest and during activation with [Arg8]-vasopressin (AVP). Thapsigargin (TG) raised and superfusion with 0 Ca2+ lowered [Ca2+]cyt, but both treatments decreased SR Ca2+ and AVP-evoked Ca2+ transients. Neither TG nor 0 Ca2+ affected basal [3H]InsP, but both treatments increased AVP-evoked synthesis of [3H]InsP. Exposure for several minutes to 40 mM K+ solution, BAY K 8644, or low-Na+ solution all elevated [Ca2+]cyt and, thereby, increased SR Ca2+, as manifested by augmented AVP-evoked Ca2+ transients. In all three cases, AVP-evoked, but not basal, [3H]InsP were reduced. The inhibitory effect of 40 mM K+ on AVP-evoked [3H]InsP synthesis was blocked when SR Ca2+ uptake was prevented by TG. Brief (30-s) exposures to 40 mM K+, which elevated [Ca2+]cyt but not SR Ca2+ loading, did not modify AVP-evoked [3H]InsP synthesis or Ca2+ transients. These results demonstrate an inverse relationship between SR Ca2+ content and evoked [3H]-InsP synthesis. Moreover, they suggest that SR Ca2+ may serve as a signal that modulates sarcolemmal [3H]InsP formation.
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Affiliation(s)
- D M Berman
- Department of Physiology, University of Maryland School of Medicine, Baltimore 21201
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22
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Missiaen L, De Smedt H, Droogmans G, Casteels R. Ca2+ release induced by inositol 1,4,5-trisphosphate is a steady-state phenomenon controlled by luminal Ca2+ in permeabilized cells. Nature 1992; 357:599-602. [PMID: 1608471 DOI: 10.1038/357599a0] [Citation(s) in RCA: 219] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Low concentrations of inositol 1,4,5-trisphosphate (InsP3) evoke a very rapid mobilization of intracellular Ca2+ stores in many cell types, which can be followed by a further, much slower efflux. Two explanations have been suggested for this biphasic release. The first proposes that the Ca2+ stores vary in their sensitivity to InsP3, and each store releases either its entire contents or nothing (all-or-none release); the second proposes instead that the stores are uniformly sensitive to the effects of InsP3, but that they can release only a fraction of their Ca2+ before their sensitivity is somehow attenuated (steady-state release). Experiments using purified InsP3 receptor molecules reconstituted into lipid vesicles have shown heterogeneity of the receptors in their response to InsP3 under conditions in which the total Ca2+ level at both sides of the receptor is held constant. We now report that in permeabilized A7r5 smooth-muscle cells incubated in Ca(2+)-free medium, the amount of 45Ca2+ remaining in the stores after the rapid transient phase of release is independent of their initial Ca2+ levels, indicating that partially depleted stores are less sensitive to InsP3. Moreover, if the stores are reloaded with 40Ca2+ after the first stimulus, reapplication of the same low concentration of InsP3 will release further 45Ca2+. This recovery of InsP3 sensitivity is almost complete. Under these conditions, Ca2+ release must thus occur by a steady-state mechanism, in which the decreasing Ca2+ content of the stores slows down further release.
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Affiliation(s)
- L Missiaen
- Laboratorium voor Fysiologie, KUL Campus Gasthuisberg, Leuven, Belgium
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23
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Missiaen L, Taylor CW, Berridge MJ. Pyrophosphatase-induced Ca2+ release is unrelated to the spontaneous release from inositol 1,4,5-trisphosphate-sensitive Ca2+ stores. Biochem J 1992; 282 ( Pt 1):306-8. [PMID: 1311558 PMCID: PMC1130924 DOI: 10.1042/bj2820306] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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24
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Shuttleworth T. Ca2+ release from inositol trisphosphate-sensitive stores is not modulated by intraluminal [Ca2+]. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50561-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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25
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Oldershaw KA, Nunn DL, Taylor CW. Quantal Ca2+ mobilization stimulated by inositol 1,4,5-trisphosphate in permeabilized hepatocytes. Biochem J 1991; 278 ( Pt 3):705-8. [PMID: 1898359 PMCID: PMC1151403 DOI: 10.1042/bj2780705] [Citation(s) in RCA: 97] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In several cell types, including hepatocytes, submaximal concentrations of Ins(1,4,5)P3 stimulate an initial rapid mobilization of intracellular Ca2+ stores that is followed by either no further Ca2+ release or very much slower release. Further additions of Ins(1,4,5)P3 then evoke further Ca2+ mobilization. Such 'incremental' responses [Meyer & Stryer (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 3841-3845] could result from all-or-nothing emptying of stores that differ in their sensitivities to Ins(1,4,5)P3 or from partial emptying of stores that are more uniformly sensitive, but unable to release all of their Ca2+ because the response to Ins(1,4,5)P3 rapidly attenuates. By measuring unidirectional 45Ca2+ efflux from intracellular stores stimulated with Ins(1,4,5)P3 under conditions where they continue to sequester 40Ca2+, we provide evidence suggesting that Ins(1,4,5)P3 stimulates all-or-nothing emptying of stores that differ in their sensitivities to Ins(1,4,5)P3, a quantal response pattern.
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Affiliation(s)
- K A Oldershaw
- Department of Pharmacology, University of Cambridge, U.K
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