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Wang C, Zhang L, Jaeger LA, Machaty Z. Store-Operated Ca2+ Entry Sustains the Fertilization Ca2+ Signal in Pig Eggs. Biol Reprod 2015; 93:25. [PMID: 26063872 DOI: 10.1095/biolreprod.114.126151] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 06/01/2015] [Indexed: 11/01/2022] Open
Abstract
The role of store-operated Ca(2+) entry (SOCE) in the maintenance of sperm-induced Ca(2+) oscillations was investigated in porcine eggs. We found that 10 μM gadolinium (Gd(3+)), which is known to inhibit SOCE, blocked Ca(2+) entry that was triggered by thapsigargin-induced store depletion and also caused an abrupt cessation of the fertilization Ca(2+) signal. In a similar manner 3,5-bis(trifluoromethyl)pyrazole 2 (20 μM), and tetrapandin-2 (10 μM), potent SOCE inhibitors, also blocked thapsigargin-stimulated Ca(2+) entry and disrupted the Ca(2+) oscillations after sperm-egg fusion. The downregulation of Stim1 or Orai1 in the eggs did not alter the Ca(2+) content of the intracellular stores, whereas co-overexpression of these proteins led to the generation of irregular Ca(2+) transients after fertilization that stopped prematurely. We also found that thapsigargin completely emptied the endoplasmic reticulum, and that the series of Ca(2+) transients stopped abruptly after the addition of thapsigargin to the fertilized eggs, indicating that the proper reloading of the intracellular stores is a prerequisite for the maintenance of the Ca(2+) oscillations. These data strengthen our previous findings that in porcine eggs SOCE is a major signaling cascade that is responsible for sustaining the repetitive Ca(2+) signal at fertilization.
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Affiliation(s)
- Chunmin Wang
- Department of Animal Sciences, Purdue University, West Lafayette, Indiana
| | - Lu Zhang
- Department of Animal Sciences, Purdue University, West Lafayette, Indiana
| | - Laurie A Jaeger
- Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana
| | - Zoltan Machaty
- Department of Animal Sciences, Purdue University, West Lafayette, Indiana
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Xu W, Longo FJ, Wintermantel MR, Jiang X, Clark RA, DeLisle S. Calreticulin modulates capacitative Ca2+ influx by controlling the extent of inositol 1,4,5-trisphosphate-induced Ca2+ store depletion. J Biol Chem 2000; 275:36676-82. [PMID: 10973951 DOI: 10.1074/jbc.m002041200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calreticulin (CRT) is a highly conserved Ca(2+)-binding protein that resides in the lumen of the endoplasmic reticulum (ER). We overexpressed CRT in Xenopus oocytes to determine how it could modulate inositol 1,4,5-trisphosphate (InsP(3))-induced Ca(2+) influx. Under conditions where it did not affect the spatially complex elevations in free cytosolic Ca(2+) concentration ([Ca(2+)](i)) due to InsP(3)-induced Ca(2+) release, overexpressed CRT decreased by 46% the Ca(2+)-gated Cl(-) current due to Ca(2+) influx. Deletion mutants revealed that CRT requires its high capacity Ca(2+)-binding domain to reduce the elevations of [Ca(2+)](i) due to Ca(2+) influx. This functional domain was also required for CRT to attenuate the InsP(3)-induced decline in the free Ca(2+) concentration within the ER lumen ([Ca(2+)](ER)), as monitored with a "chameleon" indicator. Our data suggest that by buffering [Ca(2+)](ER) near resting levels, CRT may prevent InsP(3) from depleting the intracellular stores sufficiently to activate Ca(2+) influx.
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Affiliation(s)
- W Xu
- Veterans Affairs Medical Center and Departments of Medicine and Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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3
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Machaca K. Reversible Ca gradients between the subplasmalemma and cytosol differentially activate Ca-dependent Cl currents. J Gen Physiol 1999; 113:249-66. [PMID: 9925823 PMCID: PMC2223373 DOI: 10.1085/jgp.113.2.249] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Xenopus oocytes express several different Ca-activated Cl currents that have different waveforms and biophysical properties. We compared the stimulation of Ca-activated Cl currents measured by two-microelectrode voltage clamp with the Ca transients measured in the same cell by confocal microscopy and Ca-sensitive fluorophores. The purpose was to determine how the amplitude and/or spatio-temporal features of the Ca signal might explain how these different Cl currents were activated by Ca. Because Ca release from stores was voltage independent, whereas Ca influx depended upon the electrochemical driving force, we were able to separately assess the contribution of Ca from these two sources. We were surprised to find that Ca signals measured with a cytosolic Ca-sensitive dye, dextran-conjugated Ca-green-1, correlated poorly with Cl currents. This suggested that Cl channels located at the plasma membrane and the Ca-sensitive dye located in the bulk cytosol were sensing different [Ca]. This was true despite Ca measurement in a confocal slice very close to the plasma membrane. In contrast, a membrane-targeted Ca-sensitive dye (Ca-green-C18) reported a Ca signal that correlated much more closely with the Cl currents. We hypothesize that very local, transient, reversible Ca gradients develop between the subplasmalemmal space and the bulk cytosol. [Ca] is higher near the plasma membrane when Ca is provided by Ca influx, whereas the gradient is reversed when Ca is released from stores, because Ca efflux across the plasma membrane is faster than diffusion of Ca from the bulk cytosol to the subplasmalemmal space. Because dissipation of the gradients is accelerated by inhibition of Ca sequestration into the endoplasmic reticulum with thapsigargin, we conclude that [Ca] in the bulk cytosol declines slowly partly due to futile recycling of Ca through the endoplasmic reticulum.
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Affiliation(s)
- K Machaca
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322-3030, USA
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Kuruma A, Hartzell HC. Dynamics of calcium regulation of chloride currents in Xenopus oocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:C161-75. [PMID: 9886932 DOI: 10.1152/ajpcell.1999.276.1.c161] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ca-activated Cl currents are widely expressed in many cell types and play diverse and important physiological roles. The Xenopus oocyte is a good model system for studying the regulation of these currents. We previously showed that inositol 1,4,5-trisphosphate (IP3) injection into Xenopus oocytes rapidly elicits a noninactivating outward Cl current (ICl1-S) followed several minutes later by the development of slow inward (ICl2) and transient outward (ICl1-T) Cl currents. In this paper, we investigate whether these three currents are mediated by the same or different Cl channels. Outward Cl currents were more sensitive to Ca than inward Cl currents, as shown by injection of different amounts of Ca or by Ca influx through a heterologously expressed ligand-gated Ca channel, the ionotropic glutamate receptor iGluR3. These data could be explained by two channels with different Ca affinities or one channel with a higher Ca affinity at depolarized potentials. To distinguish between these possibilities, we determined the anion selectivity of the three currents. The anion selectivity sequences for the three currents were the same (I > Br > Cl), but ICl1-S had an I-to-Cl permeability ratio more than twofold smaller than the other two currents. The different anion selectivities and instantaneous current-voltage relationships were consistent with at least two different channels mediating these currents. However, after consideration of possible errors, the hypothesis that a single type of Cl channel underlies the complex waveforms of the three different macroscopic Ca-activated Cl currents in Xenopus oocytes remains a viable alternative.
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Affiliation(s)
- A Kuruma
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322-3030, USA
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5
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Lomax RB, Herrero CJ, García-Palomero E, García AG, Montiel C. Capacitative Ca2+ entry into Xenopus oocytes is sensitive to omega-conotoxins GVIA, MVIIA and MVIIC. Cell Calcium 1998; 23:229-39. [PMID: 9681186 DOI: 10.1016/s0143-4160(98)90121-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have studied capacitative Ca2+ entry into Xenopus oocytes by depleting intracellular Ca2+ stores with inositol 1,4,5-trisphosphate or thapsigargin. Capacitative Ca2+ entry was evoked by hyperpolarisation and monitored via the Ca(2+)-activated Cl- current. Hyperpolarisation-evoked currents increased with extracellular [Ca2+] in the range 0.9-5 mM, and were reversibly inhibited by extracellular Mg2+ (0.1-10 mM) by up to 60%. Currents were decreased by the voltage-gated Ca2+ channel antagonists omega-conotoxin GVIA, MVIIA and MVIIC (0.3-10 microM) and the inhibition of Ca2+ entry in individual oocytes by omega-conotoxins GVIA and MVIIA was highly heterogeneous, but not additive. Flunarizine (10 microM) and the imidazoles SK&F 96365 (10 microM), miconazole (40 microM) and econazole (40 microM) partly blocked Ca2+ entry. Ca2+ entry was unaffected by calciseptine (300 nM) or alpha-bungarotoxin (1 microM). The possibility that these compounds might inhibit the Ca(2+)-activated Cl- current rather than capacitative Ca2+ entry itself was examined by recording the Cl- current activated by the increase in [Ca2+]i activated by the flash photolysis of caged Ca2+. Eicosatetraynoic acid (2-10 microM) markedly inhibited, and La3+ (1 mM but not 100 microM) potentiated the increase in Ca(2+)-activated Cl- current. In contrast, omega-conotoxins and Mg2+ had no effect on the Ca(2+)-activated Cl- current itself. These findings support the hypothesis that capacitative Ca2+ entry into Xenopus oocytes occurs through channels with a pharmacology similar to that of neuronal non-L type voltage-gated Ca2+ channels.
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Affiliation(s)
- R B Lomax
- Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Spain.
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Affiliation(s)
- F C Mooren
- Medizinische Klinik und Poliklinik B, Westfälische Wilhelm-Universität, Münster, Germany
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DeLisle S, Marksberry EW, Bonnett C, Jenkins DJ, Potter BV, Takahashi M, Tanzawa K. Adenophostin A can stimulate Ca2+ influx without depleting the inositol 1,4,5-trisphosphate-sensitive Ca2+ stores in the Xenopus oocyte. J Biol Chem 1997; 272:9956-61. [PMID: 9092535 DOI: 10.1074/jbc.272.15.9956] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Adenophostin A possesses the highest known affinity for the inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) receptor (InsP3R). The compound shares with Ins(1,4,5)P3 those structural elements essential for binding to the InsP3R. However, its adenosine 2'-phosphate moiety has no counterpart in the Ins(1,4,5)P3 molecule. To determine whether its unique structure conferred a distinctive biological activity, we characterized the adenophostin-induced Ca2+ signal in Xenopus oocytes using the Ca2+-gated Cl- current assay. In high concentrations, adenophostin A released Ca2+ from Ins(1,4, 5)P3-sensitive stores and stimulated a Cl- current that depended upon the presence of extracellular Ca2+. We used this Cl- current as a marker of Ca2+ influx. In low concentrations, however, adenophostin A stimulated Ca2+ influx exclusively. In contrast, Ins(1,4,5)P3 and (2-hydroxyethyl)-alpha-D-glucopyranoside 2',3, 4-trisphosphate, an adenophostin A mimic lacking most of the adenosine moiety, always released intracellular Ca2+ before causing Ca2+ influx. Ins(1,4,5)P3 could still release Ca2+ during adenophostin A-induced Ca2+ influx, confirming that the Ins(1,4, 5)P3-sensitive intracellular Ca2+ stores had not been emptied. Adenophostin- and Ins(1,4,5)P3-induced Ca2+ influx were not additive, suggesting that both agonists stimulated a common Ca2+ entry pathway. Heparin, which blocks binding to the InsP3R, prevented adenophostin-induced Ca2+ influx. These data indicate that adenophostin A can stimulate the influx of Ca2+ across the plasma membrane without inevitably emptying the Ins(1,4,5)P3-sensitive intracellular Ca2+ stores.
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Affiliation(s)
- S DeLisle
- Veterans Administration Medical Center, Department of Internal Medicine, and Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City, Iowa 52240, USA.
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8
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Hartzell HC, Machaca K, Hirayama Y. Effects of adenophostin-A and inositol-1,4,5-trisphosphate on Cl- currents in Xenopus laevis oocytes. Mol Pharmacol 1997; 51:683-92. [PMID: 9106635 DOI: 10.1124/mol.51.4.683] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Adenophostin-A, a novel compound isolated from cultures of Penicillium brevicompactum, has been shown to stimulate Ca2+ release from inositol-1,4,5-trisphosphate (IP3)-sensitive Ca2+ stores in microsomal preparations, permeabilized cells, and lipid vesicles containing purified IP3 receptor. The purpose of the current study was to compare the effects of adenophostin-A and IP3 on Ca2+ release from stores and Ca2+ influx in intact Xenopus laevis oocytes. Ca2+ influx though store-operated Ca2+ channels and Ca2+ release from stores were monitored by measuring two Ca2+ -activated Cl- currents that can be used as real-time indicators of Ca2+ release and Ca2+ influx (I(Cl-1) and I(Cl-2), respectively). We find that high concentrations (final intraoocyte concentrations of 5-10 microM) of adenophostin-A and IP3 stimulate a large Ca2+ release from stores (as measured by I(Cl-1)) followed by Ca2+ influx (as measured by I(Cl-2)). Low concentrations (approximately 50 nM) of IP3 stimulate oscillations in Ca2+ release without stimulating Ca2+ influx. In contrast, low concentrations of adenophostin-A can stimulate Ca2+ influx without stimulating a large Ca2+ release. However, Ca2+ influx did not occur in the complete absence of Ca2+ release. Therefore, it is unlikely that adenophostin-A directly stimulates store-operated Ca2+ channels. We hypothesize that adenophostin-A releases Ca2+ from a subpopulation of stores that is tightly coupled to store-operated Ca2+ channels.
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Affiliation(s)
- H C Hartzell
- Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322-3030, USA.
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9
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Wilson BA, Zhu X, Ho M, Lu L. Pasteurella multocida toxin activates the inositol triphosphate signaling pathway in Xenopus oocytes via G(q)alpha-coupled phospholipase C-beta1. J Biol Chem 1997; 272:1268-75. [PMID: 8995431 DOI: 10.1074/jbc.272.2.1268] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Pasteurella multocida toxin (PMT) has been hypothesized to cause activation of a GTP-binding protein (G-protein)-coupled phosphatidylinositol-specific phospholipase C (PLC) in intact cells. We used voltage-clamped Xenopus oocytes to test for direct PMT-mediated stimulation of PLC by monitoring the endogenous Ca2+-dependent C1- current. Injection of PMT induced an inward, two-component Cl- current, similar to that evoked by injection of IP3 through intracellular Ca2+ mobilization and Ca2+ influx through voltage-gated Ca2+ channels. These PMT-induced currents were blocked by specific inhibitors of Ca2+ and Cl- channels, removal of extracellular Ca2+, or chelation of intracellular Ca2+. Specific antibodies directed against an N-terminal, but not a C-terminal, peptide of PMT inhibited the toxin-induced currents, implicating that the N terminus of PMT is important for toxin activity. Injection with specific antibodies against PLCbeta1, PLCbeta2, PLCbeta3, or PLCgamma1 identified PLCbeta1 as the primary mediator of the PMT-induced Cl- currents. Injection with guanosine 5'-O-(2-(thio)diphosphate), antibodies to the common GTP-binding region of G-protein alpha subunits, or antibodies to different regions of G-protein beta subunits established the involvement of a G-protein alpha subunit in PMT-activation of PLCbeta1. Injection with specific antibodies against the alpha-subunits of G(q/11), G(s/olf), G(i/o/t/z), or G(i-1/i-2/i-3) isoforms confirmed the involvement of Gq/11alpha. Preinjection of oocytes with pertussis toxin enhanced the PMT response. Overexpression of G(q)alpha in oocytes could enhance the PMT response by 30-fold to more than 300-fold, whereas introduction of antisense G(q)alpha cRNA reduced the response by 7-fold. The effects of various specific antibodies on the PMT response were reproduced in oocytes overexpressing G(q)alpha.
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Affiliation(s)
- B A Wilson
- Department of Biochemistry and Molecular Biology, Wright State University School of Medicine, Dayton, Ohio 45435, USA.
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10
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Fukuda M, Mikoshiba K. Structure-function relationships of the mouse Gap1m. Determination of the inositol 1,3,4,5-tetrakisphosphate-binding domain. J Biol Chem 1996; 271:18838-42. [PMID: 8702543 DOI: 10.1074/jbc.271.31.18838] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Gap1(IP4BP), one of a member of Ras GTPase-activating proteins, has been identified as a specific inositol 1,3,4,5-tetrakisphosphate (IP4)-binding protein (Cullen, P. J., Hsuan, J. J., Truong, O., Letcher, A. J., Jackson, T. R., Dawson, A. P., and Irvine, R. F. (1995) Nature 386, 527-530). In this paper we describe Gap1(m), which is closely related to Gap1(IP4BP), to also be an IP4-binding protein and show that the pleckstrin homology domain (PH) is the central IP4-binding domain by expressing fragments of the mouse Gap1(m) in Escherichia coli as fusion proteins and examining their activities. However, in addition to the PH domain, an adjacent GAP-related domain and carboxyl terminus are required for high affinity specific IP4 binding. The PH domain is highly conserved in the Gap1 family and also has striking homology to the amino-terminal region of Bruton's tyrosine kinase. Substitution of Cys for Arg at position 628 in the PH domain corresponding to the mutation of Bruton's tyrosine kinase observed in X-linked immunodeficiency mice results in a dramatic reduction of IP4 binding activity as well as phospholipid binding capacity of Gap1(m). This mutant also showed the GAP activity against Ha-Ras to be similar to that of the wild type Gap1(m). Our results suggest that the PH domain of Gap1(m) functions as a modulatory domain of GAP activity by binding IP4 and phospholipids.
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Affiliation(s)
- M Fukuda
- Molecular Neurobiology Laboratory, Tsukuba Life Science Center, The Institute of Physical and Chemical Research (RIKEN), 3-1-1 Koyadai, Tsukuba, Ibaraki 305, Japan
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Gillo B, Sealfon SC, Minke B. Pharmacology of a capacitative Ca2+ entry in Xenopus oocytes. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1996; 35:77-82. [PMID: 8823936 DOI: 10.1016/1011-1344(96)07303-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have characterized pharmacological properties of inositol trisphosphate (InsP3)-mediated calcium entry pathway in Xenopus oocytes via activation of Ca(2+)-dependent Cl- channels (ICl, Ca) as a sensitive indicator for increase in cytosolic [Ca2+]. This type of Ca2+ entry mechanism is known as a capacitative Ca2+ entry (CCE). Voltage-clamped oocytes were maintained in Ca(2+)-free medium and injected with InsP3 which depleted the InsP3-sensitive Ca2+ stores. 10-20 min later, the oocytes were exposed, at 2-3 min intervals, to 5 mM Ca(2+)-containing medium for 5-10 s which evoked repeated inward Cl- current. No effect of external Ca2+ was apparent before InsP3 injection. To determine the pharmacological characteristics of CCE, oocytes were incubated with various chemical agents in Ca(2+)-free solution and exposed to Ca2+ again in presence of the chemical. It was found that organic Ca2+ channel blockers were relatively ineffective in blocking CCE while the inorganic Ca2+ channel blocker La3+ was most efficient in blocking the current. Attempts to measure conductance increase when the Cl- channels were blocked during activation of Ca2+ influx were unsuccessful. Therefore we tested the hypothesis that the Ca2+ influx is mediated via a Ca-H transporter. Lowering the external pH (to pH 6.5) or application of the protonophore carbonylcyanide p-trifluoromethoxyphenyl hydrazone (EC50 = 2 x 10(-8) M) effectively blocked CCE. Since Ca-H countertransport in the plasma membrane is coupled to Ca2+ extrusion by Ca-ATPase in vascular smooth muscle we suggest that the capacitative Ca2+ entry in Xenopus oocytes may possibly arise from slippage of plasma membrane Ca-ATPase coupled to proton countertransport, a mechanism reported in a variety of cells. Ca2+ slippage may arise from the large Ca2+ gradient produced by the Ca2+ depletion protocol.
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Affiliation(s)
- B Gillo
- Department of Physiology, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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12
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Auld AM, Bawden MJ, Berven LA, Harland L, Hughes BP, Barritt GJ. Injection of rat hepatocyte poly(A)+ RNA to Xenopus laevis oocytes leads to expression of a constitutively-active divalent cation channel distinguishable from endogenous receptor-activated channels. Cell Calcium 1996; 19:439-52. [PMID: 8793184 DOI: 10.1016/s0143-4160(96)90117-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The expression of hepatocyte plasma membrane receptor-activated divalent cation channels in immature (stages V and VI) Xenopus laevis oocytes and the properties which allow these channels to be distinguished from endogenous receptor-activated divalent cation channels were investigated. Divalent cation inflow to oocytes housed in a multiwell plate was measured using the fluorescent dyes Fluo-3 and Fura-2. In control oocytes, ionomycin, cholera toxin, thapsigargin, 3-fluoro-inositol 1,4,5-trisphosphate (InsP3F) and guanosine 5'-[gamma-thio]triphosphate (GTP gamma S) stimulated Ca2+ and Mn2+ inflow following addition of these ions to the oocytes. Ionomycin-, cholera-toxin-, thapsigargin- and InsP3F-stimulated Ca2+ inflow was inhibited by Gd3+ (half maximal inhibition at less thari 5 microM Gd3+ for InsP3F-stimulated Ca2+ inflow). GTP gamma S-stimulated Ca2+ inflow was insensitive to 50 microM Gd3+ and to SK&F 96365. These results indicate that at least three types of endogenous receptor-activated Ca2+ channels can be detected in Xenopus oocytes using Ca(2+)-sensitive fluorescent dyes: lanthanide-sensitive divalent cation channels activated by intracellular Ca2+ store depletion, lanthanide-sensitive divalent cation channels activated by cholera toxin, and lanthanide-insensitive divalent cation channels activated by an unknown trimeric G-protein. Oocytes microinjected with rat hepatocyte poly(A)+ RNA exhibited greater rates of Ca2+ and Mn2+ inflow in the basal (no agonist) state, greater rates of Ca2+ inflow in the presence of vasopressin or InsP3F and greater rates of Ba2+ inflow in the presence of InsP3F, when compared with "mock"-injected oocytes. In poly(A)+ RNA-injected oocytes, vasopressin- and InsP3F-stimulated Ca2+ inflow, but not basal Ca2+ inflow, was inhibited by Gd3+. It is concluded that at least one type of hepatocyte plasma membrane divalent cation channel, which admits Mn2+ as well as Ca2+ and is lanthanide-insensitive, can be expressed and detected in Xenopus oocytes.
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Affiliation(s)
- A M Auld
- Department of Medical Biochemistry, School of Medicine, Flinders University, Adelaide, Australia
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13
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Takata Y, Kato H. Adrenoceptors in SHR: alterations in binding characteristics and intracellular signal transduction pathways. Life Sci 1995; 58:91-106. [PMID: 8606625 DOI: 10.1016/0024-3205(95)02213-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
There is much data on altered adrenoceptor function in the heart, blood vessel and kidney from spontaneously hypertensive rats (SHR). The enhancement of vascular and renal alpha-adrenoceptor function, i.e. vasoconstriction and retention of water and sodium, may contribute to the development and maintenance of the hypertension, whereas cardiac alpha1-adrenoceptor may be of minor physiological significance. Alpha1-adrenoceptor-mediated signal transduction as a whole is increased in SHR vascular tissues, but the intracellular signaling per receptor in the kidney seems to be decreased despite increased alpha1-adrenoceptor density. On the other hand, cardiac and vascular beta-adrenoceptor responsiveness is attenuated in SHR. Reduced vasorelaxation mediated by beta-adrenoceptors may also contribute to high blood pressure. The impaired cardiovascular beta-adrenoceptor function in SHR does not appear to be necessarily explained by alterations observed at receptor levels. Alterations in signal transduction should be also considered. Limited data on renal beta-adrenoceptor density and its signaling suggest decreased or unaltered cyclic AMP formation per receptor in SHR. We will review alterations in both binding characteristics and each component of intracellular signal transduction pathways in cardiovascular and renal adrenoceptors of SHR.
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Affiliation(s)
- Y Takata
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa, Japan
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14
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del Pilar Gomez M, Nasi E. Activation of light-dependent K+ channels in ciliary invertebrate photoreceptors involves cGMP but not the IP3/Ca2+ cascade. Neuron 1995; 15:607-18. [PMID: 7546740 DOI: 10.1016/0896-6273(95)90149-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The activation of light-dependent K+ channels in ciliary photoreceptors from Pecten was investigated using intracellular dialysis of putative messengers and modulators. Neither elevated [Ca2+] nor BAPTA changed the membrane current in the dark or the light response. IP3 and the antagonists heparin and decavanadate were similarly ineffective, indicating that in these cells the IP3/Ca2+ signaling pathway is not crucial for phototransduction. By contrast, 8-Br-cGMP and cGMP induced an outward current accompanied by an increase in membrane conductance; 8-Br-cAMP was ineffective. The identity between the cGMP-induced and the light-induced currents is suggested by the following: both are carried by K+ and blocked by 4-AP, and both show outward rectification. In addition, guanine cyclic nucleotides depressed the photoresponse and induced single-channel currents in excised patches of light-sensitive membrane. These light-dependent channels therefore appear to represent a link between the families of cyclic nucleotide-gated channels and voltage-dependent K+ channels.
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Affiliation(s)
- M del Pilar Gomez
- Department of Physiology, Boston University School of Medicine, Massachusetts 02118, USA
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15
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DeLisle S, Mayr GW, Welsh MJ. Inositol phosphate structural requisites for Ca2+ influx. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 268:C1485-91. [PMID: 7611369 DOI: 10.1152/ajpcell.1995.268.6.c1485] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To understand how inositol phosphates (InsP) cause Ca2+ influx, we injected 37 highly purified compounds containing a total of 49 InsP positional isomers into Xenopus oocytes. The eight InsP that stimulated Ca2+ influx were those that had the highest potency at releasing intracellular Ca2+, indicating that their common target was the inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] receptor. To cause Ca2+ influx, these InsP had to be injected in a much higher concentration than the minimal concentration required to release intracellular Ca2+. Such high InsP concentrations could inhibit ongoing oscillatory intracellular Ca2+ release. In addition, we found that InsPs could not elicit further intracellular Ca2+ release during the course of Ca2+ influx. Our data are consistent with the "capacitative Ca2+ entry" hypothesis, which states that InsP stimulate Ca2+ influx by depleting the InsP-sensitive intracellular Ca2+ store. In this context, we would suggest that to deplete the InsP-sensitive intracellular Ca2+ store, InsP may have to be present in a sufficiently high concentration to override the oscillatory Ca(2+)-refilling mechanisms of the stores.
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Affiliation(s)
- S DeLisle
- Veterans Affairs Medical Center, Iowa City, Iowa, USA
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16
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Gilon P, Bird GJ, Bian X, Yakel JL, Putney JW. The Ca(2+)-mobilizing actions of a Jurkat cell extract on mammalian cells and Xenopus laevis oocytes. J Biol Chem 1995; 270:8050-5. [PMID: 7713906 DOI: 10.1074/jbc.270.14.8050] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Randriamampita and Tsien (Randriamampita, C., and Tsien, R. Y. (1993) Nature 364, 809-814) suggested that an acid-extracted fraction from a Jurkat cell line contains a messenger responsible for the coupling of calcium entry to the depletion of intracellular stores, i.e. capacitative calcium entry. We found that the extract, prepared as described by Randriamampita and Tsien, caused Ca2+ entry in 1321N1 astrocytoma cells which was not blocked by the D-myo-1,4,5-trisphosphate-receptor antagonist, heparin. In contrast to astrocytoma cells, when applied to mouse lacrimal acinar cells and rat hepatocytes the Jurkat extract always caused the release of intracellular Ca2+, followed by Ca2+ entry across the plasma membrane. This activity of the extract on lacrimal cells was blocked by either intracellular injection of heparin or extracellular atropine. Similarly prepared lacrimal cell extracts gave Ca2+ responses when applied to astrocytoma cells or lacrimal cells which were similar to those for Jurkat-derived extract. However, extracts from hepatocytes had no effect. In most Xenopus oocytes, the Jurkat extract had no effect, while in a few oocytes, the extract gave a [Ca2+]i response similar to that seen in lacrimal cells, that is, release of Ca2+ followed by Ca2+ entry. We conclude that the actions of the Jurkat cell extract are not consistent with its containing the long sought messenger for capacitative calcium entry. It is likely that this fraction contains a number of factors that mediate Ca2+ response in different cell types, possibly through receptor-mediated mechanisms.
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Affiliation(s)
- P Gilon
- Calcium Regulation Section, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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17
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Hennager DJ, Welsh MJ, DeLisle S. Changes in either cytosolic or nucleoplasmic inositol 1,4,5-trisphosphate levels can control nuclear Ca2+ concentration. J Biol Chem 1995; 270:4959-62. [PMID: 7890598 DOI: 10.1074/jbc.270.10.4959] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The free nucleoplasmic Ca2+ concentration ([Ca2+]n) may regulate many nuclear events, such as gene transcription. Since the nucleus may possess the enzymes necessary to generate the second messenger inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), and because the nuclear envelope may enclose an Ins(1,4,5)P3-releasable Ca2+ store, we tested the hypothesis that nuclear and/or cytosolic levels of Ins(1,4,5)P3 can control [Ca2+]n. To assay [Ca2+]n, we measured the fluorescence of the Ca2+ indicator fluo 3 in the nucleus of Xenopus oocytes by confocal microscopy. When we injected Ins(1,4,5)P3 into the cytosol, [Ca2+]n increased. This increase in [Ca2]n still occurred when heparin was present in the nucleus, but was abolished when heparin was present in the cytosol, indicating that cytosolic Ins(1,4,5)P3 levels could control [Ca2+]n. When we injected Ins(1,4,5)P3 directly into the nucleus, [Ca2+]n increased, even when heparin was present in the cytosol, indicating that Ins(1,4,5)P3 could control [Ca2+]n from within the nucleus. These results provide functional evidence for Ins(1,4,5)P3 receptors facing the nucleoplasm and raise the possibility that a phosphoinositide cycle situated at the nuclear membranes can control Ca(2+)-dependent nuclear functions.
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Affiliation(s)
- D J Hennager
- Veterans Administration Medical Center, Iowa City, Iowa
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18
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Tojyo Y, Tanimura A, Matsumoto Y, Sugiya H. Staurosporine enhances Ca2+ entry induced by depletion of intracellular Ca2+ stores in rat parotid acinar cells. Cell Calcium 1995; 17:32-40. [PMID: 7553779 DOI: 10.1016/0143-4160(95)90100-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effect of staurosporine on the Ca2+ signalling induced by the muscarinic receptor agonist carbachol (CCh) was studied in Fura-2-loaded rat parotid acinar cells. At concentrations > 1 nM, staurosporine dose-dependently enhanced the sustained increase in cytosolic free Ca2+ concentration ([Ca2+]i), but did not affect the peak [Ca2+]i seen just after stimulation. The enhancement of the sustained increase in [Ca2+]i was not attenuated by the protein kinase C activator, 4 beta-phorbol 12-myristate 13-acetate, and not mimicked by another inhibitor of protein kinase C, K-252a, suggesting that the effect of staurosporine on the CCh-induced Ca2+ signalling may be due to a mechanism independent of the inhibitory action on protein kinase C. Staurosporine also enhanced the increases in [Ca2+]i induced by the microsomal Ca(2+)-ATPase inhibitor thapsigargin (TG) and the Ca2+ ionophore ionomycin (Iono). When the cells were stimulated by CCh, TG, or Iono in the absence of extracellular Ca2+, a transient increase in [Ca2+]i due to Ca2+ release from intracellular stores was observed. This increase in [Ca2+]i was unaffected by preincubation with staurosporine. However, when Ca2+ was added to the extracellular medium after [Ca2+]i had returned to the resting level, the increase in [Ca2+]i was significantly enhanced by staurosporine. In addition, staurosporine accelerated the Mn2+ influx following the addition of CCh, TG, or Iono. These results suggest that staurosporine modulates the Ca2+ entry system activated by depletion of intracellular Ca2+ stores in rat parotid acinar cells.
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Affiliation(s)
- Y Tojyo
- Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Japan
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19
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Shirakawa H, Miyazaki S. Evidence for inositol tetrakisphosphate-activated Ca2+ influx pathway refilling inositol trisphosphate-sensitive Ca2+ stores in hamster eggs. Cell Calcium 1995; 17:1-13. [PMID: 7553776 DOI: 10.1016/0143-4160(95)90097-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
To identify the Ca2+ influx pathway responsible for maintaining Ca2+ oscillations in hamster eggs, changes in intracellular Ca2+ concentration ([Ca2+]i) were recorded using the Fura-2 fluorescent imaging technique during iontophoretic injection of inositol phosphates under voltage clamp. Both inositol 1,4,5-trisphosphate (InsP3) and 1,3,4,5-tetrakisphosphate (InsP4) caused repetitive Ca2+ transients when injected continuously into eggs, although the latter was much less effective. These Ca2+ transients were inhibited by the monoclonal antibody 18A10 to the InsP3 receptor/Ca2+ channel. In Ca(2+)-free medium, InsP4-induced Ca2+ transients were absent or much less frequent than in normal medium. A small but persistent increase in [Ca2+]i during InsP4 injection was revealed when Ca2+ uptake into InsP3-sensitive Ca2+ stores was suppressed by thapsigargin. This Ca2+ rise is due to Ca2+ entry, but not Ca2+ release, because it was: (i) increased by raising the extracellular Ca2+ concentration and abolished in Ca(2+)-free medium; (ii) larger at more negative membrane potentials which provide greater electrical driving force for Ca2+ entry; and (iii) not affected by 18A10. A moderate dose of InsP3 did not cause substantial Ca2+ entry, as tested in thapsigargin- and 18A10-treated eggs. InsP4 facilitated the restoration of Ca2+ stores after Ca2+ releases induced by pulsatile InsP3 injections. Thus, we obtained evidence for a Ca2+ influx pathway activated by InsP4 which provides Ca2+ to refill InsP3-sensitive Ca2+ stores in intact cells.
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Affiliation(s)
- H Shirakawa
- Department of Physiology, Tokyo Women's Medical College, Japan
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20
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Fukuda M, Aruga J, Niinobe M, Aimoto S, Mikoshiba K. Inositol-1,3,4,5-tetrakisphosphate binding to C2B domain of IP4BP/synaptotagmin II. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(19)62031-4] [Citation(s) in RCA: 143] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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21
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Parker I, Yao Y. Relation between intracellular Ca2+ signals and Ca(2+)-activated Cl- current in Xenopus oocytes. Cell Calcium 1994; 15:276-88. [PMID: 8055544 DOI: 10.1016/0143-4160(94)90067-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Activation of inositol 1,4,5-trisphosphate (InsP3) signalling in Xenopus oocytes causes intracellular Ca2+ mobilization and thereby activates a Ca(2+)-dependent Cl- membrane conductance. Measurements of cytosolic Ca2+ levels using fluorescent indicators, however, revealed little correspondence with Cl- currents. Intracellular photorelease of InsP3 from a caged precursor evoked transient currents that peaked while the Ca(2+)-fluorescence signal was rising, and subsequently declined within a few seconds, even though the Ca2+ signal remained elevated much longer. Also, Cl- currents evoked by agonist activation showed transient spikes while a wave of Ca2+ liberation swept across the cell, but then decreased when the Ca2+ signal attained a maximal level. Thus, the Cl- current corresponded better to the rate of rise of intracellular free Ca2+, rather than to its steady state level. Experiments using paired flashes to photolyse caged InsP3 and caged Ca2+ indicated that this relationship did not arise through desensitization or inactivation of the Cl- conductance. Furthermore, fluorescence measurements made at different depths into the cell using a confocal microscope revealed no evidence that a rapid decline of local Ca2+ levels near the plasma membrane was responsible for the decay of Ca(2+)-activated Cl- current. Instead, Cl- channels may show an adaptive or incremental response to Ca2+, which is likely to be important for the encoding and transmission of information by Ca2+ spikes.
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Affiliation(s)
- I Parker
- Department of Psychobiology, University of California at Irvine
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22
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DeLisle S, Radenberg T, Wintermantel MR, Tietz C, Parys JB, Pittet D, Welsh MJ, Mayr GW. Second messenger specificity of the inositol trisphosphate receptor: reappraisal based on novel inositol phosphates. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 266:C429-36. [PMID: 8141257 DOI: 10.1152/ajpcell.1994.266.2.c429] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
To further understand how the second messenger D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] interacts with its intracellular receptor, we injected 47 highly purified inositol phosphate (InsP) positional isomers in Xenopus oocytes and compared their potency in releasing intracellular Ca2+. The potency of the Ca(2+)-releasing InsPs spanned four orders of magnitude. Seven compounds, including the novel inositol 1,2,4,5-tetrakisphosphate [D/L-Ins (1,2,4,5)P4] and D/L-Ins(1,4,6)P3, had a very high potency. All of these highly active InsPs shared the following structure: two D-trans-equatorial phosphates (eq-P) and one equatorial hydroxyl (eq-OH) attached to ring carbons D-4, D-5, and D-6 (or to the structurally equivalent D-1, D-6, and D-5 carbons). This permissive structure was not sufficient for Ca2+ release, because it was also found in two inactive compounds, Ins(1,6)P2 and Ins(1,3,6)P3. To be active, InsPs also required the structural equivalent of a D-3 eq-OH and/or a D-1 eq-P. Together, our data reveal how the structure of the InsP molecule affects its ability to release Ca2+.
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Affiliation(s)
- S DeLisle
- Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242
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23
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Igwe OJ. Modulation of substance P-ergic system in the rat spinal cord by an opioid antagonist. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1994; 21:263-73. [PMID: 7513375 DOI: 10.1016/0169-328x(94)90257-7] [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: 01/25/2023]
Abstract
Substance P- and opioid peptide-immunoreactive nerve terminals functionally interact in the spinal cord as two opposing systems in the regulation of the nociceptive pathway. In order to determine how SP-ergic system adapts to chronic opioid receptor blockade, the effects of naltrexone on SP level, SP receptor and the second messenger system coupled to the SP receptor were examined in the rat spinal cord. Male Sprague-Dawley rats were treated with naltrexone or vehicle for seven days by constant minipump infusion. Animals were sacrificed on day 8, spinal cords rapidly removed, segmentally sectioned and used to determine SP and inositol 1,4,5-trisphosphate [ins(1,4,5)P3] tissue contents, and to examine the regulation of their respective receptors in in vitro receptor binding assays. Following chronic naltrexone treatment, SP content in the lumbosacral segment of the spinal cord was increased by 53% over matched control values. The binding capacity (Bmax) of SP receptors, determined using [125I]BHSP, in lumbosacral synaptosomal membranes was significantly increased by 92%, but the binding affinity (Kd) remained unchanged. In addition, the concentration of [Sar9, Met(O2)11]SP, an NK-1 receptor-specific agonist, required to inhibit half of [125I]BHSP binding (IC50) in lumbosacral synaptosomal membranes was significantly decreased, but the IC50s for SP, the endogenous ligand for the SP receptor, and [Pro7]NK B, an NK-3 receptor-specific agonist, were unaltered by chronic blockade of opioid receptors. The data suggest that although naltrexone does not directly interact with tachykinin receptors, it acts indirectly on SP-ergic neurons to cause a change in the apparent affinity of NK-1 receptor (as reflected by a change in IC50 value). Formation of cellular ins(1,4,5)P3 in the lumbosacral cord, quantified by a highly sensitive and selective radioreceptor assay, was significantly increased by 34% relative to matched controls. A time course study indicated that increases in ins(1,4,5)P3 contents over the time studied corresponded qualitatively with increases in SP level in the lumbosacral cord. With [3H]ins(1,4,5)P3 as a ligand, Scatchard analyses of the concentration dependent saturation curves showed that the density of intracellular ins(1,4,5)P3 receptors was also increased by 119%, with no change in binding affinity. The data suggest that ins(1,4,5)P3 formation, possibly coupled to functional SP receptor activation, and ins(1,4,5)P3 receptors, which mediate ins(1,4,5)P3-induced alterations in intracellular Ca2+ flux, are increased in the lumbosacral cord by chronic blockade of opioid receptors. Taken together, the data support the concept of a role for endogenous opioids in the regulation of SP receptor activity in the spinal cord.
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Affiliation(s)
- O J Igwe
- Division of Pharmacology, School of Pharmacy, University of Missouri-Kansas City 64108-2792
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24
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Abstract
By virtue of their biological simplicity and widespread availability, platelets frequently have been used as a model system to study signal transduction. Such studies have revealed that changes in intracellular free calcium concentration are central to platelet functioning. The following article reviews current concepts of platelet structure and function, with particular emphasis on the mechanisms involved in platelet Ca2+ signalling.
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Affiliation(s)
- P Sargeant
- Physiological Laboratory, Cambridge University, U.K
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25
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Hashimoto Y, Watanabe T, Kinoshita M, Tsukamoto K, Togo M, Horie Y, Matsuda Y, Kurokawa K. Ca2+ entry pathways activated by the tumor promoter thapsigargin in human platelets. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1220:37-41. [PMID: 8268242 DOI: 10.1016/0167-4889(93)90094-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Thapsigargin-activated Ca2+ entry into platelets was examined in the presence of S-145, a thromboxane A2 receptor antagonist, to inhibit indirect effects by endogenously formed prostaglandin H2/thromboxane A2. With external Ca2+ present, 0.2 microM thapsigargin caused a prompt increase in intracellular Ca2+ concentration ([Ca2+]i) followed by a gradual increase. Pretreatment with 6 microM wortmannin, a specific inhibitor of myosin light chain kinase, partly inhibited the increase in [Ca2+]i. In Ca(2+)-free EGTA buffer, thapsigargin induced a smaller increase in [Ca2+]i, and subsequent addition of Ca2+ to the buffer caused a further prompt increase in [Ca2+]i, demonstrating external Ca2+ entry. Wortmannin only partly inhibited this entry of external Ca2+. The wortmannin-insensitive Ca2+ entry pathway remained open for more than 6 min in Ca(2+)-free buffer. On the other hand, when receptor agonists such as thrombin and U46619 were substituted for thapsigargin, activation of the wortmannin-insensitive Ca2+ entry was transient (Hashimoto et al., J. Biol. Chem (1992) 267, 17078-17081). In the presence of S-145 and wortmannin, thapsigargin stimulated phosphorylation of neither the 20-kDa myosin light chain nor the 47-kDa protein, a substrate of protein kinase C. These results suggest that thapsigargin induces external Ca2+ entry by two mechanisms: (1) a mechanism involving myosin light chain kinase; (2) a mechanism, not activated by receptor agonists, that is independent of the major protein kinases of platelets.
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Affiliation(s)
- Y Hashimoto
- First Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan
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26
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Cohen RW, Margulies JE, Coulter PM, Watson JB. Functional consequences of expression of the neuron-specific, protein kinase C substrate RC3 (neurogranin) in Xenopus oocytes. Brain Res 1993; 627:147-52. [PMID: 8293295 DOI: 10.1016/0006-8993(93)90758-f] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
RC3 (neurogranin) is a neuron-specific substrate of protein kinase C (PKC) that accumulates predominantly in dendritic spines of forebrain neurons and undergoes long-term potentiation (LTP)-associated increases in PKC-phosphorylation in hippocampal slices. Here the hypothesis that RC3 functions by modulating the IP3/DAG second messenger pathway after its phosphorylation by DAG-activated PKC was tested by heterologous expression in Xenopus oocytes. Acetylcholine-evoked inward chloride (Cl-) currents, dependent on both IP3 release and intracellular calcium (Ca2+), were 2- to 3-fold higher in RC3-injected oocytes than in uninjected control oocytes. RC3-oocytes did not exhibit enhanced currents when preincubated with the protein kinase inhibitor H-7 or when a glycine residue was substituted for serine, the PKC phosphorylation site of RC3. Activation of endogenous oocyte PKC by phorbol esters generated inward Cl- currents in RC3 oocytes but not in control oocytes. RC3-dependent Cl- currents were also elicited by phorbol ester in Ca(2+)-free media. We propose that PKC-phosphorylated RC3 is capable of enhancing the mobilization of intracellular Ca2+ in Xenopus oocytes and, by inference, may play a role in Ca2+ homeostasis in dendrites of forebrain neurons.
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Affiliation(s)
- R W Cohen
- Mental Retardation Research Center, Department of Psychiatry and Biobehavioral Sciences, UCLA School of Medicine 90024
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27
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Abstract
Cellular oscillations of cytosolic free Ca2+ ([Ca2+]i) have been observed in many cell types in response to cell surface receptor agonists acting through inositol 1,4,5-trisphosphate (InsP3). In a number of cases where appropriate spatial and temporal resolution have been used to examine these [Ca2+]i oscillations, they have been found to be organized as repetitive waves of Ca2+ increase that propagate through the cytosol of individual cells. In some cases Ca2+ waves also occur as a single pass through stimulated cells. This review discusses the factors underlying the spatial organization of [Ca2+]i signals in the form of Ca2+ waves. In addition, potential mechanisms for the initiation and subsequent propagation of these Ca2+ waves are described.
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Affiliation(s)
- T A Rooney
- Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, PA
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28
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Tsunoda Y. Receptor-operated Ca2+ signaling and crosstalk in stimulus secretion coupling. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1154:105-56. [PMID: 8218335 DOI: 10.1016/0304-4157(93)90008-c] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In the cells of higher eukaryotic organisms, there are several messenger pathways of intracellular signal transduction, such as the inositol 1,4,5-trisphosphate/Ca2+ signal, voltage-dependent and -independent Ca2+ channels, adenylate cyclase/cyclic adenosine 3',5'-monophosphate, guanylate cyclase/cyclic guanosine 3',5'-monophosphate, diacylglycerol/protein kinase C, and growth factors/tyrosine kinase/tyrosine phosphatase. These pathways are present in different cell types and impinge on each other for the modulation of the cell function. Ca2+ is one of the most ubiquitous intracellular messengers mediating transcellular communication in a wide variety of cell types. Over the last decades it has become clear that the activation of many types of cells is accompanied by an increase in cytosolic free Ca2+ concentration ([Ca2+]i) that is thought to play an important part in the sequence of events occurring during cell activation. The Ca2+ signal can be divided into two categories: receptor- and voltage-operated Ca2+ signal. This review describes and integrates some recent views of receptor-operated Ca2+ signaling and crosstalk in the context of stimulus-secretion coupling.
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Affiliation(s)
- Y Tsunoda
- Department of Faculty Science, Hokkaido University, Sapporo, Japan
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29
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Hirata M, Watanabe Y, Yoshida M, Koga T, Ozaki S. Roles for hydroxyl groups of D-myo-inositol 1,4,5-trisphosphate in the recognition by its receptor and metabolic enzymes. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)36508-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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30
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Zerek-Mełeń G, Pawlikowski M, Winczyk K, Lachowicz-Ochedalska A, Legowska A, Kwaśny H, Przybylski J, Szadowska A. Effects of new somatostatin analogs on the cell proliferation of colonic crypts and colonic cancers in rats. Neuropeptides 1993; 25:57-60. [PMID: 8105412 DOI: 10.1016/0143-4179(93)90069-m] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The antiproliferative activity of two new somatostatin (SS) analogs: ASS-51 and ASS-52 have been tested in this study. We assessed their ability to inhibit the DNA synthesis in normal colon crypt cells and in the cells of chemically (dimethylhydrazine)-induced colon cancer in the rats. The incorporation of bromodeoxyuridine (BrDU) into appropriate cell nuclei was used as an index of DNA synthesis. It was found that: 1) Only ASS-51 significantly decreases the colon crypt cell proliferation in the rat when compared to controls. Since both analogs were previously shown to inhibit GH release, these data indicate that the antiproliferogenic effect of ASS-51 is independent of the inhibition of GH release. 2) Both examined analogs did not significantly effect the BrDU incorporation into cell nuclei of chemically-induced colon cancer.
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Affiliation(s)
- G Zerek-Mełeń
- Institute of Endocrinology, Medical University of Lódź, Poland
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31
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Girard S, Clapham D. Acceleration of intracellular calcium waves in Xenopus oocytes by calcium influx. Science 1993; 260:229-32. [PMID: 8385801 DOI: 10.1126/science.8385801] [Citation(s) in RCA: 138] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Many cell membrane receptors stimulate the phosphoinositide (PI) cycle, which produces complex intracellular calcium signals that regulate diverse processes such as secretion and transcription. A major messenger of this cycle, inositol 1,4,5-triphosphate (IP3), stimulates its receptor channel on the endoplasmic reticulum to release calcium into the cytosol. Activation of the PI cycle also induces calcium influx, which refills the intracellular calcium stores. Confocal microscopy was used to show that receptor-activated calcium influx, enhanced by hyperpolarization, modulates the frequency and velocity of IP3-dependent calcium waves in Xenopus laevis oocytes. These results demonstrate that transmembrane voltage and calcium influx pathways may regulate spatial and temporal patterns of IP3-dependent calcium release.
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Affiliation(s)
- S Girard
- Department of Pharmacology, Mayo Foundation, Rochester, MN 55905
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32
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Lo TM, Thayer SA. Refilling the inositol 1,4,5-trisphosphate-sensitive Ca2+ store in neuroblastoma x glioma hybrid NG108-15 cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 264:C641-53. [PMID: 8460669 DOI: 10.1152/ajpcell.1993.264.3.c641] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Bradykinin-induced increases in the intracellular free Ca2+ concentration ([Ca2+]i) were recorded in single NG108-15 cells with indo-1-based dual-emission microfluorimetry (50% effective concentration, 16 nM). A 1-min exposure to 30 nM bradykinin completely depleted the inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ store; refilling the store required extracellular Ca2+ (half time, 2 min). Refilling the IP3-sensitive store was completely blocked by 1 microM La3+ and 10 microM nitrendipine, but not 10 microM verapamil, 10 microM flunarizine, 1 microM nitrendipine, or 0.1 microM La3+. Thapsigargin irreversibly depleted the Ca2+ store and prevented its refilling (half-maximal inhibitory concentration, 3 nM). Influx of Ca2+ across the plasma membrane did not increase after depletion of the IP3-sensitive store by exposure to bradykinin, although maintained presence of the agonist produced significant Ca2+ influx. Similarly, Mn2+ and Ba2+ influx, as measured by indo-1 quenching and spectral shifts, did not increase following depletion of IP3-sensitive store. In contrast to depletion of the IP3-sensitive Ca2+ store by bradykinin, thapsigargin (10 nM) treatment produced Ca2+ and Ba2+ influx. We conclude that after Ca2+ mobilization, the IP3-sensitive Ca2+ store in NG108-15 cells is refilled with cytoplasmic Ca2+ via a thapsigargin-sensitive Ca(2+)-Mg(2+)-ATPase. Cytoplasmic Ca2+ is replenished by a persistent leak of Ca2+ across the plasma membrane. This leak is not modulated by the status of the intracellular Ca2+ store. In NG108-15 cells, agonist and thapsigargin-evoked Ca2+ entry are mediated by activation of plasmalemmal Ca2+ channels independent of the status of the IP3-sensitive intracellular Ca2+ store.
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Affiliation(s)
- T M Lo
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis 55455
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33
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Lupu-Meiri M, Beit-Or A, Christensen SB, Oron Y. Calcium entry in Xenopus oocytes: effects of inositol trisphosphate, thapsigargin and DMSO. Cell Calcium 1993; 14:101-10. [PMID: 8458074 DOI: 10.1016/0143-4160(93)90080-p] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Agonist- and inositol 1,4,5-trisphosphate (InsP3)-evoked responses in Xenopus oocytes utilize calcium mobilized from cellular stores as well as from the medium. We studied the effect of the status of Ca stores on InsP3-induced Ca entry. Thapsigargin (TG) caused a net increase of 45Ca2+ efflux from oocytes in a time and dose dependent manner (31 and 54% of total label, at 30 and 60 min, respectively). Incubation with TG (60 min) resulted in a complete loss of the response to InsP3 implying that InsP3-sensitive Ca stores were depleted. Challenge with 1.8 mM Ca2+ resulted in a large depolarizing chloride current (1231 +/- 101 nA) which was not further potentiated by InsP3. This suggested that extensive depletion of cellular Ca stores is sufficient to induce maximal entry of extracellular Ca (Cao). Following the injection of InsP3, a much more limited loss of cellular Ca was sufficient to produce large Ca entry. Dimethyl sulfoxide (DMSO) alone, the vehicle used to dissolve TG, did not cause increase in either efflux of 45Ca2+, nor in the Cao-evoked Cl- current. It did, however, markedly potentiate this current following the injection of InsP3. DMSO moderately inhibited InsP3-induced 45Ca2+ efflux from oocytes. Hence, apparent potentiation of Ca entry can be observed without additional depletion of cellular Ca. We conclude that Ca entry may be induced via either stimulation with InsP3 and limited Ca depletion or depletion of a specific and, possibly small, cellular Ca store alone. The mechanism of DMSO potentiation is unknown, but may be important in view of the universal use of this solvent as vehicle.
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Affiliation(s)
- M Lupu-Meiri
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel
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34
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Kleppisch T, Wobus AM, Hescheler J. Cation channels in oocytes and early states of development: a novel type of nonselective cation channel activated by adrenaline in a clonal mesoderm-like cell line (MES-1). EXS 1993; 66:297-303. [PMID: 7505660 DOI: 10.1007/978-3-0348-7327-7_24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The expression of receptors and ion channels alters during growth, maturation, and after fertilization of oocytes reflecting functional changes. Besides voltage-dependent ion channels, oocyte membranes possess an IP3-activated cation channel mediating a prolonged Ca2+ influx. The Ca2+ is thought to be involved in maturation and fertilization. Alternatively, mono- and divalent cations can enter oocytes via stretch-activated channels. The oocyte channel population is further modified during subsequent embryogenesis, suggesting that ionic channels obviously become expressed at specific states of embryological differentiation and in tissue-specific manner. The resulting differences in functional ion channel populations of adult cells underlie the large diversity of cells and their function. Conversely, differentiation and cell proliferation themselves depend on ion transport. Ca2+ ions have been shown to play a pivotal role in these processes. Nonselective cation channels represent one possible pathway for Ca2+ entry into the cell and, therefore, might be involved in the regulation of embryological development. Undifferentiated embryonal carcinoma cells (P19), visceral endoderm-like cells (END-2), epithelioid ectoderm-like cells (EPI-7), mesoderm-like cells (MES-1), and parietal yolk sac cells (PYS-2) have been used as a model to study the expression of ionic channels during early development. In MES-1 cells a nonselective cation current was activated by adrenaline. Interestingly, the intracellular pathway for activation of these channels involved the cascade of activation of the cAMP-dependent protein kinase (PKA) resulting in protein phosphorylation. This mechanism is well known for Ca2+ channel stimulation in cardiac and skeletal muscle both originating from the mesoderm.
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Affiliation(s)
- T Kleppisch
- Institut für Physiologie, Humboldt-Universität zu Berlin, FRG
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35
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Lachowicz A, Stepień H, Kunert-Radek J, Pawlikowski M. Effects of somatostatin on inositol-1,4,5-trisphosphate content in mouse spleen lymphocytes. ACTA ACUST UNITED AC 1992; 101:661-4. [PMID: 1351438 DOI: 10.1016/0300-9629(92)90340-v] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. The effects of somatostatin-14 (SS) and diazepam in vitro on the content of inositol-1,4,5-trisphosphate (IP3) in mouse spleen lymphocytes were investigated. 2. It was found that the exposure of mouse spleen lymphocytes in vitro to SS sharply diminished their IP3 level. 3. Diazepam had no effect on lymphocytes IP3 content. 4. The inhibition of phosphatydyloinositol (PI) breakdown was suggested as one of the mechanisms of the physiological SS action.
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Affiliation(s)
- A Lachowicz
- Institute of Endocrinology, Medical Academy of Lódź, Poland
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36
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DeLisle S, Welsh M. Inositol trisphosphate is required for the propagation of calcium waves in Xenopus oocytes. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42391-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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37
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Shapira H, Lupu-Meiri M, Oron Y. The metabolism of microinjected inositol trisphosphate in Xenopus oocytes. J Basic Clin Physiol Pharmacol 1992; 3:119-38. [PMID: 1295570 DOI: 10.1515/jbcpp.1992.3.2.119] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Microinjection of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) into Xenopus oocytes evokes a complex physiological response composed of a transient and a slow depolarizing chloride current. We investigated the relationship between intracellular levels of Ins(1,4,5)P3 and the kinetics of the physiological response. Microinjected Ins(1,4,5)P3 was slowly degraded following first order kinetics of disappearance (t1/2 = 10 min). The degradation products were inositol bisphosphate (InsP2), inositol monophosphate (InsP) and inositol, as well as inositol tetrakisphosphate (InsP4). The rate of degradation of injected 3[H]-Ins(1,4)P2 was much greater (t1/2 = 3 min), indicating that the conversion of InsP3 to InsP2 may be the rate-limiting step in the degradation process. The slow degradation of 3[H]-Ins(1,4,5)P3 was not a result of its conversion to Ins(1,3,4)P3 since no accumulation of InsP3 was observed within 10 min of microinjection of 3[H]-Ins(1,3,4,5)P4. Activation of protein kinase C (PK-C) with a phorbol ester transiently increased the rate of conversion of 3[H]-Ins(1,4,5)P3 to InsP2. This, however, did not significantly affect the overall kinetics of 3[H]-Ins(1,4,5)P3 disappearance. Our results indicate that the kinetics of Ins(1,4,5)P3 degradation do not correlate well with the termination of both the rapid and the slow components of the physiological response. The termination of the slow component of the response, however, may be related to the decay of Ins(1,4,5)P3-induced 45Ca efflux, which lasted about 10 min.
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Affiliation(s)
- H Shapira
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel
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38
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Goldberg G, Shapira H, Oron Y. Inositol trisphosphate may access calcium from stores not coupled to muscarinic receptors in Xenopus oocytes. Pflugers Arch 1992; 420:313-8. [PMID: 1598187 DOI: 10.1007/bf00374464] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Oocytes of a large fraction of Xenopus females exhibit a complex response to acetylcholine (ACh) consisting of rapid, transient and prolonged, slow chloride currents. Frequent consecutive challenges or a single prolonged challenge with ACh result in a marked decrease in response amplitudes, i.e. refractoriness. In ACh-refractory oocytes, the response to injected inositol 1,4,5-trisphosphate (InsP3), the intracellular mediator of the ACh response, is not affected. Similarly, InsP3-evoked responses were obtained in oocytes that lacked muscarinic response or that lost their responsiveness as a result of progesterone-induced maturation. To investigate the mechanism of this phenomenon, we have depleted intracellular calcium stores by repeated challenges with ACh in calcium-free medium. Disappearance of the ACh response through depletion of the ACh-coupled calcium store did not prevent a subsequent response to InsP3. These results imply that InsP3 can mobilize calcium from other stores, not depleted by previous exposure to ACh. This finding is further reinforced by our results that demonstrate that ACh causes 45Ca efflux in responsive oocytes, while InsP3 in supramaximal concentrations does not induce 45Ca efflux. Indeed, InsP3 can induce 45Ca efflux only when more than 2 pmol/oocyte is injected. This is also the concentration of InsP3 that desensitizes the InsP3 response. These data suggest that InsP3 also releases cellular calcium from stores different from those mobilized by ACh.
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Affiliation(s)
- G Goldberg
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel
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39
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Hoth M, Penner R. Depletion of intracellular calcium stores activates a calcium current in mast cells. Nature 1992; 355:353-6. [PMID: 1309940 DOI: 10.1038/355353a0] [Citation(s) in RCA: 1353] [Impact Index Per Article: 42.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In many cell types, receptor-mediated Ca2+ release from internal stores is followed by Ca2+ influx across the plasma membrane. The sustained entry of Ca2+ is thought to result partly from the depletion of intracellular Ca2+ pools. Most investigations have characterized Ca2+ influx indirectly by measuring Ca(2+)-activated currents or using Fura-2 quenching by Mn2+, which in some cells enters the cells by the same influx pathway. But only a few studies have investigated this Ca2+ entry pathway more directly. We have combined patch-clamp and Fura-2 measurements to monitor membrane currents in mast cells under conditions where intracellular Ca2+ stores were emptied by either inositol 1,4,5-trisphosphate, ionomycin, or excess of the Ca2+ chelator EGTA. The depletion of Ca2+ pools by these independent mechanisms commonly induced activation of a sustained calcium inward current that was highly selective for Ca2+ ions over Ba2+, Sr2+ and Mn2+. This Ca2+ current, which we term ICRAC (calcium release-activated calcium), is not voltage-activated and shows a characteristic inward rectification. It may be the mechanism by which electrically nonexcitable cells maintain raised intracellular Ca2+ concentrations and replenish their empty Ca2+ stores after receptor stimulation.
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Affiliation(s)
- M Hoth
- Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany
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40
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Hansen C, Yang L, Williamson J. Mechanisms of receptor-mediated Ca2+ signaling in rat hepatocytes. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55101-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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41
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42
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Wahlestedt C. Strategies to detect heterologously expressed tachykinin receptors in Xenopus Oocytes. Ann N Y Acad Sci 1991; 632:116-22. [PMID: 1719860 DOI: 10.1111/j.1749-6632.1991.tb33100.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- C Wahlestedt
- Department of Neurology and Neuroscience, Cornell University Medical College, New York, New York 10021
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43
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Guse AH, Gercken G, Boysen H, Schwarz JR, Meyerhof W. Inositol tetrakisphosphates as second messengers induce Ca(++)-dependent chloride currents in Xenopus laevis oocytes. Biochem Biophys Res Commun 1991; 179:641-7. [PMID: 1715700 DOI: 10.1016/0006-291x(91)91420-h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Microinjection of inositol 1,3,4,5-tetrakisphosphate or inositol 1,4,5-trisphosphate induced distinct chloride membrane currents in defolliculated Xenopus laevis oocytes. To decide whether these Cl(-)-currents were due to the injected compounds or their metabolic products, [3H]Ins(1,3,4,5)P4 or [3H]Ins(1,4,5)P3 were injected into oocytes and their metabolites were analyzed by HPLC. Our results indicate that Ins(1,3,4,5)P4 itself or its metabolite Ins(1,3,4,6)P4 is able to induce Cl(-)-membrane currents, most likely by increasing the cytosolic Ca(++)-concentration.
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Affiliation(s)
- A H Guse
- Institut für Biochemie und Lebensmittelchemie, Abt. für Biochemie, Universität, Hamburg, FRG
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44
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Walseth TF, Aarhus R, Zeleznikar RJ, Lee HC. Determination of endogenous levels of cyclic ADP-ribose in rat tissues. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1094:113-20. [PMID: 1883849 DOI: 10.1016/0167-4889(91)90032-s] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cyclic ADP-ribose (cADPR) is a potent mediator of calcium mobilization in sea urchin eggs. The cADPR synthesizing enzyme is present not only in the eggs but also in various mammalian tissue extracts. The purpose of this study was to ascertain whether cADPR is a naturally occurring nucleotide in mammalian tissues. Rat tissues were frozen and powdered in liquid N2, followed by extraction with perchloric acid at -10 degrees C. [32P]cADPR was prepared and used as a tracer. The acid extracts were chromatographed on a Mono-Q column and cADPR in the fractions were determined by its ability to release Ca2+ from egg homogenates. That the release was mediated by cADPR and not inositol trisphosphate (IP3) in the extracts was shown by the fact that the homogenates, subsequent to Ca2+ release induced by active fractions, were desensitized to authentic cADPR but not to IP3. Furthermore, the Ca2+ release activity was shown to co-elute with [32P]cADPR. The endogenous level of cADPR determined in rat liver is 3.37 +/- 0.64 pmol/mg, in heart is 1.04 +/- 0.08 pmol/mg and in brain is 2.75 +/- 0.35 pmol/mg. These results indicate cADPR is a naturally occurring nucleotide and suggest that it may be a general second messenger for mobilizing intracellular Ca2+.
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Affiliation(s)
- T F Walseth
- Department of Pharmacology, University of Minnesota, Minneapolis 55455
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45
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Tohda M, Nomura Y. Biphasic effects of mianserin and desipramine on serotonin-evoked current and Cl- efflux in Xenopus oocytes. Eur J Pharmacol 1991; 200:305-10. [PMID: 1782991 DOI: 10.1016/0014-2999(91)90587-g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Serotonin (5-HT, 1 microM) elicited two phases of Cl- inward current in Xenopus oocytes injected with rat brain mRNA: a transient current (T-current), which was generated rapidly (within 1 min), and a sustained current (S-current), which persisted for 10 min. Each type of 5-HT-evoked response was time-dependent after mRNA injection. The T-current was generated at 20-30 h and the S-current at 30-40 h. Although mianserin at 0.1 microM completely inhibited the T-current, 10 microM mianserin was required to suppress the S-current. 5-HT also caused Cl- efflux from oocytes preloaded with 36Cl-. Cl- efflux during 1 min, corresponding to the T-current, was inhibited by 0.1 microM mianserin. A higher concentration of mianserin (10 microM) was required to block the efflux for 10 min, corresponding to the S-current, as well as the current response. Desipramine selectively inhibited the T-current and Cl- efflux for 1 min. The mechanisms underlying the different sensitivity to mianserin of oocytes injected with rat brain mRNA are discussed.
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Affiliation(s)
- M Tohda
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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46
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Bird GS, Rossier MF, Hughes AR, Shears SB, Armstrong DL, Putney JW. Activation of Ca2+ entry into acinar cells by a non-phosphorylatable inositol trisphosphate. Nature 1991; 352:162-5. [PMID: 1648669 DOI: 10.1038/352162a0] [Citation(s) in RCA: 165] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In many cell types, receptor activation of phosphoinositidase C results in an initial release of intracellular Ca2+ stores followed by sustained Ca2+ entry across the plasma membrane. Inositol 1,4,5-trisphosphate is the mediator of the initial Ca2+ release, although its role in the mechanism underlying Ca2+ entry remains controversial. We have now used two techniques to introduce inositol phosphates into mouse lacrimal acinar cells and measure their effects on Ca2+ entry: microinjection into cells loaded with Fura-2, a fluorescent dye which allows the measurement of intracellular free calcium concentration by microspectrofluorimetry, and perfusion of patch clamp pipettes in the whole-cell configuration while monitoring the activity of Ca(2+)-activated K+ channels as an indicator of intracellular Ca2+. We report here that inositol 1,4,5-trisphosphate serves as a signal that is both necessary and sufficient for receptor activation of Ca2+ entry across the plasma membrane in these cells.
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Affiliation(s)
- G S Bird
- Calcium Regulation Section, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
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47
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Abstract
This review focuses on the inositol phosphate/Ca2+ signalling pathway in Xenopus oocytes. The known characteristics of the individual elements of this cascade--from the membrane receptors to the intracellular Ca2+ stores--will be covered. Based on this knowledge, a simple model will then try to account for the behaviour of the newly recognized oscillations of free intracellular Ca2+ and propagated Ca2+ waves. Finally, some of the potential physiological functions of the inositol phosphate pathway will be summarized. Although there is no systematic attempt to contrast the findings in the oocyte to those in other cells, the readers of this journal will not fail to notice a high degree of similarity. Although this may seem unexciting at first, it suggests that the inositol phosphate signalling pathway may be strikingly conserved across species.
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Affiliation(s)
- S Delisle
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City
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48
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Thomas AP, Renard DC, Rooney TA. Spatial and temporal organization of calcium signalling in hepatocytes. Cell Calcium 1991; 12:111-26. [PMID: 1647873 DOI: 10.1016/0143-4160(91)90013-5] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Treatment of hepatocytes with agonists which act via the second messenger inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), results in increases of cytosolic free Ca2+ [( Ca2+]i) which are manifest as a series of discrete [Ca2+]i transients or oscillations. With increasing agonist dose [Ca2+]i oscillation frequency increases and the initial latent period decreases, but the amplitude of the [Ca2+]i oscillations remains constant. Studies of these [Ca2+]i oscillations at the subcellular level have indicated that the [Ca2+]i changes do not occur synchronously throughout the cell, but initiate at a specific subcellular domain, adjacent to a region of the plasma membrane, and then propagate through the cell as a [Ca2+]i wave. For a given ceil, the locus of [Ca2+]i wave initiation is constant for every oscillation in a series and is also identical when the cell is sequentially stimulated with different agonists or when the phospholipase C-linked G protein is activated directly using AIF4-. The kinetics of the [Ca2+]i waves indicate that a Ca(2+)-activated mechanism is involved in propagating the oscillatory [Ca2+]i increases throughout the cell, and the data appear to be most consistent with a process of Ca(2+)-induced Ca2+ release. It is proposed that the ability to propagate [Ca2+]i oscillations into regions of the cell distal to the region in which the signal transduction apparatus is localized could serve an important function in allowing all parts of the cell to respond to the stimulus.
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Affiliation(s)
- A P Thomas
- Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia
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49
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Ferguson JE, Han JK, Kao JP, Nuccitelli R. The effects of inositol trisphosphates and inositol tetrakisphosphate on Ca2+ release and Cl- current pattern in the Xenopus laevis oocyte. Exp Cell Res 1991; 192:352-65. [PMID: 1846334 DOI: 10.1016/0014-4827(91)90052-v] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We report that Ins(1,3,4,5)P4 releases calcium from intracellular stores of intact Xenopus laevis oocytes, as indicated by two different techniques, Ca2(+)-sensitive microelectrodes and a fura-2 imaging system. Ins(1,3,4,5)P4 releases only 20% as much Ca2+ as the same amount of Ins(1,4,5)P3. This effect is not due to the conversion of the injected Ins(1,3,4,5)P4 to Ins(1,4,5)P3, which is known to release Ca2+, because the amount of [3H]Ins(1,3,4,5)P4 that is converted to Ins(1,4,5)P3 is extremely small, as determined using HPLC. Examination of the different current patterns induced by Ins(1,4,5)P3 and Ins(1,3,4,5)P4, when injected into voltage-clamped oocytes, provided further evidence that the Ins(1,3,4,5)P4 was not being converted back to Ins(1,4,5)P3. We investigated the effects of four compounds, three inositol trisphosphates (Ins(1,4,5)P3, Ins(2,4,5)P3, and Ins(1,3,4)P3), and Ins(1,3,4,5)P4, on Cl- current conductance in order to examine (1) the possible role of Ins(1,3,4,5)P4 in cell activation and (2) the relationships between intracellular Ca2+ and the activation of Cl- currents. Immature stage VI Xenopus laevis oocytes were voltage-clamped and injected with Ins(1,4,5)P3, Ins(2,4,5)P3, and Ins(1,3,4)P3. Ins(1,4,5)P3 and Ins(2,4,5)P3 triggered Ca2(+)-dependent Cl- currents, but Ins(1,3,4)P3 did not trigger currents nor did it release intracellular Ca2+. Ins(2,4,5)P3 was fourfold less effective at inducing the immediate Cl- current pulse than Ins(1,4,5)P3. The Cl- current pattern was quite dependent on the amount of Ins(1,4,5)P3 injected into the oocyte. Low amounts of Ins(1,4,5)P3 triggered only an immediate single Cl- current pulse, whereas large amounts triggered the immediate single pulse, followed by a quiescent period, followed by oscillating Cl- currents. In contrast to the response of Ins(1,4,5)P3, injection of Ins(1,3,4,5)P4 triggered only oscillating Cl- currents whose magnitude, but not pattern, was dependent on the amount injected into the cell. The currents generated by Ins(1,3,4,5)P4 resemble the oscillating Cl- currents triggered by large amounts of Ins(1,4,5)P3 and Ins(2,4,5)P3. Ins(1,3,4,5)P4, unlike Ins(1,4,5)P3 and Ins(2,4,5)P3, rarely caused an immediate Cl- current pulse, but caused an immediate release of calcium. Therefore, we suggest that the oscillating currents are only indirectly dependent on calcium. These [Ca2+]i and conductance measurements suggest that both Ins(1,4,5)P3 and Ins(1,3,4,5)P4 have roles in intracellular Ca2+ regulation.
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Affiliation(s)
- J E Ferguson
- Department of Zoology, University of California, Davis, 95616
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50
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Lee HC. Specific binding of cyclic ADP-ribose to calcium-storing microsomes from sea urchin eggs. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52240-7] [Citation(s) in RCA: 44] [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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