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Léger C, Pitard I, Sadi M, Carvalho N, Brier S, Mechaly A, Raoux-Barbot D, Davi M, Hoos S, Weber P, Vachette P, Durand D, Haouz A, Guijarro JI, Ladant D, Chenal A. Dynamics and structural changes of calmodulin upon interaction with the antagonist calmidazolium. BMC Biol 2022; 20:176. [PMID: 35945584 PMCID: PMC9361521 DOI: 10.1186/s12915-022-01381-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 07/29/2022] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Calmodulin (CaM) is an evolutionarily conserved eukaryotic multifunctional protein that functions as the major sensor of intracellular calcium signaling. Its calcium-modulated function regulates the activity of numerous effector proteins involved in a variety of physiological processes in diverse organs, from proliferation and apoptosis, to memory and immune responses. Due to the pleiotropic roles of CaM in normal and pathological cell functions, CaM antagonists are needed for fundamental studies as well as for potential therapeutic applications. Calmidazolium (CDZ) is a potent small molecule antagonist of CaM and one the most widely used inhibitors of CaM in cell biology. Yet, CDZ, as all other CaM antagonists described thus far, also affects additional cellular targets and its lack of selectivity hinders its application for dissecting calcium/CaM signaling. A better understanding of CaM:CDZ interaction is key to design analogs with improved selectivity. Here, we report a molecular characterization of CaM:CDZ complexes using an integrative structural biology approach combining SEC-SAXS, X-ray crystallography, HDX-MS, and NMR. RESULTS We provide evidence that binding of a single molecule of CDZ induces an open-to-closed conformational reorientation of the two domains of CaM and results in a strong stabilization of its structural elements associated with a reduction of protein dynamics over a large time range. These CDZ-triggered CaM changes mimic those induced by CaM-binding peptides derived from physiological protein targets, despite their distinct chemical natures. CaM residues in close contact with CDZ and involved in the stabilization of the CaM:CDZ complex have been identified. CONCLUSION Our results provide molecular insights into CDZ-induced dynamics and structural changes of CaM leading to its inhibition and open the way to the rational design of more selective CaM antagonists. Calmidazolium is a potent and widely used inhibitor of calmodulin, a major mediator of calcium-signaling in eukaryotic cells. Structural characterization of calmidazolium-binding to calmodulin reveals that it triggers open-to-closed conformational changes similar to those induced by calmodulin-binding peptides derived from enzyme targets. These results provide molecular insights into CDZ-induced dynamics and structural changes of CaM leading to its inhibition and open the way to the rational design of more selective CaM antagonists.
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Affiliation(s)
- Corentin Léger
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris, 75015, France
| | - Irène Pitard
- Biological NMR and HDX-MS Technological Platform, CNRS UMR3528, Université Paris Cité, Institut Pasteur, Paris, 75015, France
| | - Mirko Sadi
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris, 75015, France
- Université Paris Cité, Paris, France
| | - Nicolas Carvalho
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris, 75015, France
- Université Paris Cité, Paris, France
| | - Sébastien Brier
- Biological NMR and HDX-MS Technological Platform, CNRS UMR3528, Université Paris Cité, Institut Pasteur, Paris, 75015, France
| | - Ariel Mechaly
- Plate-forme de Cristallographie-C2RT, Université Paris Cité, CNRS UMR3528, Institut Pasteur, Paris, France
| | - Dorothée Raoux-Barbot
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris, 75015, France
| | - Maryline Davi
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris, 75015, France
| | - Sylviane Hoos
- Plateforme de Biophysique Moléculaire, Université Paris Cité, CNRS UMR3528, Institut Pasteur, Paris, France
| | - Patrick Weber
- Plate-forme de Cristallographie-C2RT, Université Paris Cité, CNRS UMR3528, Institut Pasteur, Paris, France
| | - Patrice Vachette
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Dominique Durand
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Ahmed Haouz
- Plate-forme de Cristallographie-C2RT, Université Paris Cité, CNRS UMR3528, Institut Pasteur, Paris, France
| | - J Iñaki Guijarro
- Biological NMR and HDX-MS Technological Platform, CNRS UMR3528, Université Paris Cité, Institut Pasteur, Paris, 75015, France
| | - Daniel Ladant
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris, 75015, France.
| | - Alexandre Chenal
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris, 75015, France.
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Houchat JN, Cartereau A, Taillebois E, Thany SH. Calmidazolium induces a decrease in nicotine-induced currents and intracellular calcium levels after pulse application of nicotine onto insect neurosecretory cells. JOURNAL OF INSECT PHYSIOLOGY 2022; 139:104385. [PMID: 35315336 DOI: 10.1016/j.jinsphys.2022.104385] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 03/01/2022] [Accepted: 03/16/2022] [Indexed: 06/14/2023]
Abstract
Dorsal unpaired median (DUM) neurons, are a class of insect neurosecretory cells, which are involved in the control of several functions, such as excretion and reproduction, or the release of neurohormones. Previous studies demonstrated that they express different nicotinic acetylcholine receptor subtypes, in particular α-bungarotoxin-insensitive receptors, with nAChR1 and nAChR2 subtypes. Here, we demonstrated that pulse application of 1 mM nicotine (300 ms pulse duration) induced inward currents which were reduced under bath application of 15 µM calmidazolium, a calmodulin inhibitor. Bath application of 0.5 µM α-bungarotoxin had no effect on calmidazolium action, suggesting that it could have an indirect effect through α-bungarotoxin-insensitive receptors. Indeed, nicotine-evoked currents were reduced by 10 µM d-tubocurarine, and completely blocked by 5 µM mecamylamine, which affected nAChR1 and nAChR2 subtypes, respectively. Our results demonstrated that nAChR2 subtypes are involved in the indirect effect of calmidazolium. Moreover, we found that this calmidazolium effect was associated to a strong reduction in intracellular calcium levels after pulse application of 1 mM nicotine. Thus, compared to previous studies on mammalian cells, calmidazolium did not cause an increase in intracellular calcium levels in DUM neurons, suggesting that different calcium mechanisms are involved in the calmidazolium effect.
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Affiliation(s)
- Jean-Noël Houchat
- Université d'Orléans, LBLGC USC-INRAE 1328, 1 rue de Chartres, Orléans 45067, France
| | - Alison Cartereau
- Université d'Orléans, LBLGC USC-INRAE 1328, 1 rue de Chartres, Orléans 45067, France
| | - Emiliane Taillebois
- Université d'Orléans, LBLGC USC-INRAE 1328, 1 rue de Chartres, Orléans 45067, France
| | - Steeve H Thany
- Université d'Orléans, LBLGC USC-INRAE 1328, 1 rue de Chartres, Orléans 45067, France.
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3
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Byrne RD, Rosivatz E, Parsons M, Larijani B, Parker PJ, Ng T, Woscholski R. Differential activation of the PI 3-kinase effectors AKT/PKB and p70 S6 kinase by compound 48/80 is mediated by PKCα. Cell Signal 2007; 19:321-9. [PMID: 16942862 DOI: 10.1016/j.cellsig.2006.07.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 07/07/2006] [Accepted: 07/11/2006] [Indexed: 01/26/2023]
Abstract
The secretagogue compound 48/80 (c48/80) is a well known activator of calcium mediated processes and PKCs, and is a potent inducer of mast cell degranulation. As the latter process is a phosphoinositide 3-kinase (PI 3-kinase) mediated event, we wished to address whether or not c48/80 was an activator of PI 3-kinases. The data presented here reveal that c48/80 is an effective activator of PI 3-kinases as judged by the increased phosphorylation of PKB and p70(S6K) in fibroblasts in a PI 3-kinase dependent fashion. Compound 48/80 effectively translocates PKB to the plasma membrane and induces phosphorylation at serine 473 (S473), detected by fluorescence imaging of fixed cells. At higher concentrations the secretagogue is inhibitory towards PKB phosphorylation on S473. Conversely, p70(S6K) phosphorylation on T389 is unaffected at high doses. We provide evidence that the differential effect on the two PI 3-kinase effectors is due to activation of PKCalpha by c48/80, itself a PI 3-kinase dependent process. We conclude that compound 48/80 is an effective activator of PI 3-kinase dependent pathways, leading to the activation of effectors including PKB/Akt, p70(S6K) and PKCalpha. The latter is only activated by higher doses of c48/80 resulting in an inhibition of the c48/80 induced PKB phosphorylation, thus explaining the observed biphasic activation profile for PKB in response to this secretagogue.
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Affiliation(s)
- Richard D Byrne
- Division of Cell and Molecular Biology, Imperial College, London SW7 2AZ, United Kingdom.
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4
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Sunagawa M, Kosugi T, Nakamura M, Sperelakis N. Pharmacological Actions of Calmidazolium, a Calmodulin Antagonist, in Cardiovascular System. ACTA ACUST UNITED AC 2006. [DOI: 10.1111/j.1527-3466.2000.tb00044.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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5
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Argentaro A, Sim H, Kelly S, Preiss S, Clayton A, Jans DA, Harley VR. A SOX9 defect of calmodulin-dependent nuclear import in campomelic dysplasia/autosomal sex reversal. J Biol Chem 2003; 278:33839-47. [PMID: 12810722 DOI: 10.1074/jbc.m302078200] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During mammalian sex determination, SOX9 is translocated into the nuclei of Sertoli cells within the developing XY gonad. The N-terminal nuclear localization signal (NLS) is contained within a SOX consensus calmodulin (CaM) binding region, thereby implicating CaM in nuclear import of SOX9. By fluorescence spectroscopy and glutaraldehyde cross-linking, we show that the SOX9 HMG domain and CaM interact in vitro. The formation of a SOX9.CaM binary complex is calcium-dependent and is accompanied by a conformational change in SOX9. A CaM antagonist, calmidazolium chloride (CDZ), was observed to block CaM recognition of SOX9 in vitro and inhibit both nuclear import and consequent transcriptional activity of SOX9 in treated cells. The significance of the SOX9-CaM interaction was highlighted by analysis of a missense SOX9 mutation, A158T, identified from a XY female with campomelic dysplasia/autosomal sex reversal (CD/SRA). This mutant binds importin beta normally despite defective nuclear import. Fluorescence and quenching studies indicate that in the unbound state, the A158T mutant shows a similar conformation to that of the WT SOX9, but in the presence of CaM, the mutant undergoes unusual conformational changes. Furthermore, SOX9-mediated transcriptional activation by cells expressing the A158T mutant is more sensitive to CDZ than cells expressing WT SOX9. These results suggest first that CaM is involved in the nuclear transport of SOX9 in a process likely to involve direct interaction and second, that CD/SRA can arise, at least in part, from a defect in CaM recognition, ultimately leading to reduced ability of SOX9 to activate transcription of cartilage and testes-forming genes.
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Affiliation(s)
- Anthony Argentaro
- Human Molecular Genetics Laboratory, Prince Henry's Institute of Medical Research, Level 4 Block E, Monash Medical Centre, 246 Clayton Rd., Clayton, Victoria, 3168, Australia
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6
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Jorge RA, Menossi M, Arruda P. Probing the role of calmodulin in Al toxicity in maize. PHYTOCHEMISTRY 2001; 58:415-422. [PMID: 11557073 DOI: 10.1016/s0031-9422(01)00258-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The role of calmodulin on Al toxicity was studied in two maize (Zea mays L.) inbred lines, Cat 100-6 (Al-tolerant) and S 1587-17 (Al-sensitive). Increasing levels of Al induced the release of malate at similar rate by roots of both genotypes, while the exudation of citrate, a stronger Al-binding compound, was 3.5 times higher in Cat 100-6 seedlings exposed to 16.2x10(-6) Al(3+) activity. The calmodulin inhibitor trifluoperazine significantly reduced the root growth in both genotypes, mimicking the main effect of Al. However, when Cat 100-6 and S 1587-17 seedlings were challenged with Al in conjunction with trifluoperazine, no further reduction in root growth or any other effect of Al toxicity was observed. The rate of Al-induced citrate exudation by both genotypes was not affected by treatment with trifluoperazine or calmidazolium, another calmodulin inhibitor. The Al(3+) interaction with cytoplasmic CaM was estimated using models for the binding of Al(3+) and Mg(2+) with CaM and physiological concentrations of citrate, CaM, InsP(3), ATP, ADP, Al(3+) and Mg(2+). In this simulation, Al(3+) associated with citrate and InsP(3), but not with CaM. We conclude that calmodulin is not relevant to the physiological processes leading to the Al tolerance in maize, nor is it a primary target for Al toxicity.
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Affiliation(s)
- R A Jorge
- Universidade Estadual de Campinas, UNICAMP, Instituto de Química, Departamento de Físico-Química, SP, Campinas, Brazil.
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7
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Abstract
The structure-activity relationships of calmidazolium analogs with respect to intracellular calcium levels were investigated in HL-60 cells. Quaternized derivatives of miconazole and clotrimazole, known inhibitors of store-operated calcium (SOC) channels, were synthesized. The quaternary N-methyl derivatives of miconazole (3) and clotrimazole (6) had no effect on intracellular calcium levels, alone or after elevation of calcium induced by ATP. Calmidazolium alone induced a large increase in intracellular calcium levels in HL-60 cells (EC(50) 3 microM). Similar effects were observed for miconazole derivatives 1 (EC(50) 15 microM) and 2 (EC(50) 10 microM), wherein the diphenylmethyl group in calmidazolium was replaced by a 3,5-difluorobenzyl or cyclohexylmethyl group, respectively. The analogous clotrimazole derivatives 4 and 5 had no effect on intracellular calcium levels. The elevation of calcium levels by calmidazolium, 1, and 2 appears to be comprised of a calcium release component from inositol trisphosphate (IP(3))-sensitive stores followed by a large calcium influx component. Calcium influx was greater than that normally observed due to depletion of IP(3)-sensitive calcium stores and activation of SOC channels. In addition, only a small component of the calmidazolium-elicited influx was inhibited by the SOC channel blocker miconazole. Thus, certain quaternized imidazoles substituted with large residues at both nitrogens of the imidazole ring caused both release and influx of calcium, the latter in part through SOC channels but mainly through an undefined cationic channel. Quaternized imidazoles, unlike the parent nonquaternary imidazole miconazole, did not block SOC channels. Inhibitory effects on calmodulin-activated phosphodiesterase did not correlate with effects on calcium release and influx.
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Affiliation(s)
- J L Harper
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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8
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Xu A, Narayanan N. Reversible inhibition of the calcium-pumping ATPase in native cardiac sarcoplasmic reticulum by a calmodulin-binding peptide. Evidence for calmodulin-dependent regulation of the V(max) of calcium transport. J Biol Chem 2000; 275:4407-16. [PMID: 10660612 DOI: 10.1074/jbc.275.6.4407] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calmodulin (CaM) and Ca(2+)/CaM-dependent protein kinase II (CaM kinase) are tightly associated with cardiac sarcoplasmic reticulum (SR) and are implicated in the regulation of transmembrane Ca(2+) cycling. In order to assess the importance of membrane-associated CaM in modulating the Ca(2+) pump (Ca(2+)-ATPase) function of SR, the present study investigated the effects of a synthetic, high affinity CaM-binding peptide (CaM BP; amino acid sequence, LKWKKLLKLLKKLLKLG) on the ATP-energized Ca(2+) uptake, Ca(2+)-stimulated ATP hydrolysis, and CaM kinase-mediated protein phosphorylation in rabbit cardiac SR vesicles. The results revealed a strong concentration-dependent inhibitory action of CaM BP on Ca(2+) uptake and Ca(2+)-ATPase activities of SR (50% inhibition at approximately 2-3 microM CaM BP). The inhibition, which followed the association of CaM BP with its SR target(s), was of rapid onset (manifested within 30 s) and was accompanied by a decrease in V(max) of Ca(2+) uptake, unaltered K(0.5) for Ca(2+) activation of Ca(2+) transport, and a 10-fold decrease in the apparent affinity of the Ca(2+)-ATPase for its substrate, ATP. Thus, the mechanism of inhibition involved alterations at the catalytic site but not the Ca(2+)-binding sites of the Ca(2+)-ATPase. Endogenous CaM kinase-mediated phosphorylation of Ca(2+)-ATPase, phospholamban, and ryanodine receptor-Ca(2+) release channel was also strongly inhibited by CaM BP. The inhibitory action of CaM BP on SR Ca(2+) pump function and protein phosphorylation was fully reversed by exogenous CaM (1-3 microM). A peptide inhibitor of CaM kinase markedly attenuated the ability of CaM to reverse CaM BP-mediated inhibition of Ca(2+) transport. These findings suggest a critical role for membrane-bound CaM in controlling the velocity of Ca(2+) pumping in native cardiac SR. Consistent with its ability to inhibit SR Ca(2+) pump function, CaM BP (1-2.5 microM) caused marked depression of contractility and diastolic dysfunction in isolated perfused, spontaneously beating rabbit heart preparations. Full or partial recovery of contractile function occurred gradually following withdrawal of CaM BP from the perfusate, presumably due to slow dissociation of CaM BP from its target sites promoted by endogenous cytosolic CaM.
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Affiliation(s)
- A Xu
- Department of Physiology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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9
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Ozawa T. Ryanodine-sensitive Ca(2+) release mechanism of rat pancreatic acinar cells is modulated by calmodulin. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1452:254-62. [PMID: 10590314 DOI: 10.1016/s0167-4889(99)00135-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The effects of calmodulin (CaM) and CaM antagonists on microsomal Ca(2+) release through a ryanodine-sensitive mechanism were investigated in rat pancreatic acinar cells. When caffeine (10 mM) was added after a steady state of ATP-dependent (45)Ca(2+) uptake into the microsomal vesicles, the caffeine-induced (45)Ca(2+) release was significantly increased by pretreatment with ryanodine (10 microM). The presence of W-7 (60 microM), a potent inhibitor of CaM, strongly inhibited the release, while W-5 (60 microM), an inactive CaM antagonist, showed no inhibition. Inhibition of the release by W-7 was observed at all caffeine concentrations (5-30 mM) tested. The presence of exogenously added CaM (10 microg/ml) markedly increased the caffeine (5-10 mM)-induced (45)Ca(2+) release and shifted the dose-response curve of caffeine-induced (45)Ca(2+) release to the left. Cyclic ADP-ribose (cADPR, 2 microM)-induced (45)Ca(2+) release was enhanced by the presence of ryanodine (10 microM). cADPR (2 microM)- or ryanodine (500 microM)-induced (45)Ca(2+) release was also inhibited by W-7 (60 microM), but not by W-5 (60 microM), and was stimulated by CaM (10 microg/ml). These results suggest that the ryanodine-sensitive Ca(2+) release mechanism of rat pancreatic acinar cells is modulated by CaM.
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Affiliation(s)
- T Ozawa
- Department of Physiology, Tohoku University School of Medicine Seiryocho 2-1, Aoba-ku, Sendai, Japan
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10
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Odermatt A, Kurzydlowski K, MacLennan DH. The vmax of the Ca2+-ATPase of cardiac sarcoplasmic reticulum (SERCA2a) is not altered by Ca2+/calmodulin-dependent phosphorylation or by interaction with phospholamban. J Biol Chem 1996; 271:14206-13. [PMID: 8662932 DOI: 10.1074/jbc.271.24.14206] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Earlier studies (Hawkins, C., Xu, A., and Narayanan, N. (1994) J. Biol. Chem. 269, 31198-31206) have suggested that the Vmax of Ca2+ uptake is enhanced up to 2-fold through phosphorylation of Ser38 in the cardiac Ca2+-ATPase (SERCA2a) by calmodulin-dependent protein kinase (CaM kinase). It is difficult, however, to determine whether stimulation is caused by phosphorylation of the Ca2+-ATPase or by phosphorylation of phospholamban in cardiac microsomes. We have expressed SERCA2a in HEK-293 cells in the presence or absence of phospholamban and measured the effects on Ca2+ uptake activity of phosphorylation of microsomal proteins by CaM kinase or protein kinase A (PKA). We found no effect on the Vmax of Ca2+ uptake following phosphorylation by CaM kinase or PKA in either the presence or absence of phospholamban. The K0.5 for Ca2+ dependence of Ca2+ transport, however, was shifted following phosphorylation by either CaM kinase or PKA in those microsomes containing both SERCA2a and phospholamban, but not in those expressing only SERCA2a. Thus, we cannot confirm earlier reports of stimulation of SERCA2a activity by CaM kinase II phosphorylation of Ser38. Our studies, however, emphasize the need for adequate controls for measurement of Vmax.
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Affiliation(s)
- A Odermatt
- Banting and Best Department of Medical Research, University of Toronto, Charles H. Best Institute, Toronto, Ontario M5G 1L6, Canada
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11
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Characterization and ultrastructural localization of a novel 90-kDa protein unique to skeletal muscle junctional sarcoplasmic reticulum. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)46936-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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12
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Antagonists and inhibitors of calcium accumulation do not impair gravity perception though they adversely affect the gravitropic responses of Coprinus cinereus stipes. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/s0953-7562(09)80512-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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13
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Pereira RS, Bertocchi AP, Vercesi AE. Protective effect of trifluoperazine on the mitochondrial damage induced by Ca2+ plus prooxidants. Biochem Pharmacol 1992; 44:1795-801. [PMID: 1449534 DOI: 10.1016/0006-2952(92)90074-s] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Isolated rat liver mitochondria undergo extensive swelling and disruption of membrane potential when they accumulate Ca2+ in the presence of a prooxidant such as diamide or t-butylhydroperoxide. The phenothiazinic drug trifluoperazine, at concentrations (15-35 microM) which do not inhibit respiration or the influx of Ca2+ into mitochondria, significantly protected mitochondria against the deleterious effects of Ca2+ plus a prooxidant. In contrast, at concentrations higher than 100 microM the drug potentiated these deleterious effects of Ca2+ and prooxidants and had a damaging effect per se on the inner mitochondrial membrane. It is proposed that the protection conferred by the drug is mediated by changes in membrane protein structure that decrease the production of protein thiol cross-linkings which occur when mitochondria accumulate calcium under oxidant stress conditions.
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Affiliation(s)
- R S Pereira
- Departamento de Bioquimica, Universidade Estadual de Campinas, SP, Brazil
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Stinemetz CL, Hasenstein KH, Young LM, Evans ML. Effect of calmodulin antagonists on the growth and graviresponsiveness of primary roots of maize. PLANT GROWTH REGULATION 1992; 11:419-427. [PMID: 11537498 DOI: 10.1007/bf00130651] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We examined the effect of calmodulin (CaM) antagonists applied at the root tip on root growth, gravity-induced root curvature, and the movement of calcium across the root tip and auxin (IAA) across the elongation zone of gravistimulated roots. All of the CaM antagonists used in these studies delayed gravity-induced curvature at a concentration (1 micromole) that did not affect root growth. Calmodulin antagonists (> or = 1 micromole) inhibited downward transport of label from 45Ca2+ across the caps of gravistimulated roots relative to the downward transport of 45Ca2+ in gravistimulated roots which were not treated with CaM antagonists. Application of CaM antagonists at the root tip (> or = 1 micromole) also decreased the relative downward movement of label from 3H-IAA applied to the upper side of the elongation zone of gravistimulated roots. In general, tip application of antagonists inhibited neither the upward transport of 45Ca2+ in the root tip nor the upward movement of label from 3H-IAA in the elongation zone of gravistimulated roots. Thus, roots treated with CaM antagonists > or = 1 micromole become less graviresponsive and exhibit reduced or even a reversal of downward polarity of calcium transport across the root tip and IAA transport across the elongation zone. The results indicate that calmodulin-regulated events play a role in root gravitropism.
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Affiliation(s)
- C L Stinemetz
- Biology Department, Rhodes College, Memphis, TN 38112
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15
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Weinstein L, Brik H, Rotmensch HH, Shainberg A. Characterization of sarcoplasmic reticulum in skinned heart muscle cultures. J Cell Physiol 1991; 148:124-32. [PMID: 1860892 DOI: 10.1002/jcp.1041480115] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The plasma membranes of rat heart muscle, grown in cell culture, were made permeable with saponin in a Ca-free solution. The cells were then supplied with a medium resembling the cytosol, and the adenosine triphosphate (ATP)-dependent Ca2+ sequestration was measured in the presence of oxalate. The nonmitochondrial component accounts for about 50% of the total Ca2+ uptake. The nonmitochondrial accumulation of Ca2+ within myocardial cells was found to be reversible by addition of the Ca2+ ionophore A23187. On the other hand, the Ca2+ antagonist D-600 (50 microM) had almost no effect on Ca2+ accumulation. Caffeine reduced Ca2+ accumulation in the skinned cardiomyocytes in a concentration-dependent manner. In addition, the anticalmodulin drug trifluoperazine (TFP) reduced Ca2+ accumulation in the skinned cells. Because of the analogy between nonmitochondrial ATP-dependent Ca2+ accumulation and the sarcoplasmic reticulum (SR) function with regard to the influence of various agents, it is assumed that we actually measure Ca2+ accumulation in the SR. The rate of Ca2+ accumulation into the SR measured during the development of the cardiomyocytes in culture shows an almost linear increase as a function of culture age. Amiodarone, a potent antiarrhythmic agent, and its metabolite, desethylamiodarone, inhibited Ca2+ accumulation into SR, which may explain their therapeutic effect.
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Affiliation(s)
- L Weinstein
- Otto Meyerhoff Drug Receptor Center, Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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16
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Tuana BS, Sunahara RK, Murphy BJ, Pierce GN. Two major antigens of heart sarcolemma are Ca2(+)-binding glycoproteins that copurify with the dihydropyridine receptor. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1091:236-41. [PMID: 1847306 DOI: 10.1016/0167-4889(91)90067-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Ca2+ binding has been studied in isolated heart sarcolemmal membranes using the 45Ca overlay technique. 45Ca bound to two sarcolemmal polypeptides of 125 kDa and 97 kDa in preparations from dog, rabbit, cow and pig. During fractionation on DEAE ion-exchange and wheat-germ lectin affinity columns, the two Ca2(+)-binding polypeptides copurified with the dihydropyridine receptor associated with the voltage gated Ca2+ channel. These polypeptides were the major proteins in the isolated fraction as judged by silver staining in SDS-PAGE. Antisera raised against purified dog heart, sarcolemma indicated that the 125 and 97 kDa polypeptides were highly antigenic components of this membrane. The antisera cross-reacted with similar polypeptides in cardiac sarcolemmal preparations from rabbit, cow and pig, but not sarcoplasmic reticulum membranes. Purified antibodies against the 125 kDa polypeptide did not cross-react with the 97 kDa polypeptide, while antibodies against the 97 kDa polypeptide did not cross-react with the 125 kDa polypeptide. Both the 125 kDa and 97 kDa polypeptides bound wheat-germ lectin, suggesting both were glycoproteins. It is unlikely that these Ca2+ binding glycoproteins represent subunits of the dihydropyridine receptor-Ca2+ channel in this membrane.
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Affiliation(s)
- B S Tuana
- Department of Pharmacology, University of Ottawa, Canada
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17
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Vale MG. Effects of compound 48/80 on the Ca2+ release by reversal of the Ca2+ pump and by the Ca2+ channel of sarcoplasmic reticulum membranes. Arch Biochem Biophys 1990; 279:275-80. [PMID: 2161641 DOI: 10.1016/0003-9861(90)90491-g] [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: 12/30/2022]
Abstract
The effect of the calmodulin antagonist, compound 48/80, on the Ca2+ release from skeletal muscle sarcoplasmic reticulum was investigated. Both the Ca2+ release by reversal of the Ca2+ pump and the Ca2+ release by the Mg2(+)-controlled Ca2+ channel were studied. It was observed that, when reversal of the pump is inoperative and Mg2+ is not present in the reaction medium, 48/80 stimulates Ca2+ release from the vesicles. In contrast, in the presence of Mg2+, which blocks the Ca2+ channel, 48/80 inhibits Ca2+ release induced by ADP and Pi. This effect is strong at low concentrations of Pi (approximately 1 mM), whereas high concentrations (approximately 15 mM) protect the system against the drug. Furthermore, it was observed that 48/80 has a maximum effect on the channel-mediated Ca2+ release at concentrations of about 20 micrograms/ml, whereas maximal inhibition of the pump-mediated Ca2+ release occurs at concentrations of about 60-80 micrograms/ml. The results indicate that both the Ca2+ channel complex and the Ca2(+)-ATPase may be target systems for the effects of 48/80 on the Ca2+ transport activity of sarcoplasmic reticulum. However, the Ca2+ channel is more sensitive to the drug, suggesting an involvement of calmodulin on this mechanism of Ca2+ release.
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Affiliation(s)
- M G Vale
- Department of Zoology, University of Coimbra, Portugal
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18
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Loo G, Berlin E, Smith JT. Inhibition of mitochondrial palmitate oxidation by calmodulin antagonists. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1990; 22:631-4. [PMID: 2379666 DOI: 10.1016/0020-711x(90)90040-a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
1. The effect of calmodulin antagonists on the rate of palmitate oxidation by isolated rat liver mitochondria was studied. 2. In the presence of 100 microM amitriptyline, chlorpromazine, prenylamine, N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide or N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, palmitate oxidation was inhibited by 17, 34, 49, 31 and 37%, respectively. 3. The degree of inhibition of palmitate oxidation exerted by these chemical compounds did not appear to correlate appreciably with changes in mitochondrial membrane fluidity.
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Affiliation(s)
- G Loo
- Lipid Nutrition Laboratory, Beltsville Human Nutrition Research Center, MD 20705
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19
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Nagata A, Komoda T, Sakagishi Y. Relationship between the uptake of calcium or phosphorus and alkaline phosphatase activity induced by certain modulators in rat organs. Calcif Tissue Int 1989; 45:173-81. [PMID: 2505909 DOI: 10.1007/bf02556061] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The effects of phorbol ester or calmodulin on the calcium and phosphorus uptakes by rat tissues and their relationship to the alkaline phosphatase activity (ALP) were investigated in vivo. In rat tissues, ALP activity and calcium uptake in the duodenum and liver were clearly induced by phorbol ester treatment, whereas in the calvarium and ileum they were decreased. Phosphorus uptake was increased by the administration of phorbol ester only in the calvarium. In rats pretreated with an injection of indomethacin as an inhibitor of prostaglandin-synthesizing enzyme, the selective uptake of calcium by phorbol ester was eliminated in the duodenum and liver, as was the ALP activity. In contrast, rats showed a marked increase in ALP activity in the ileum after calmodulin treatment. Moreover, the increased uptake of calcium after calmodulin treatment was clearly seen in the ileum, calvarium, and kidney, and an increased uptake in phosphorus was seen in the duodenum, ileum, and calvarium, but not in kidney. Furthermore, prior injection of W-7 or calmidazolium as an antagonist of calmodulin, reduced the increased ALP activities and the uptake of calcium in all organs tested, but did not reduce the increased phosphorus uptake by the calvarium. Consequently, it is suggested that calcium uptake under the above conditions correlated well with changes in the ALP activity; however, phosphorus uptake seemed to be less in accord with ALP activity. The amount of tested other mineral metabolic markers suggests that the Ca uptake and ALP activity induced by certain effectors regulate 1,25(OH)2D3 level by the modulation of 25(OH)D3-1 alpha-hydroxylase activity.
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Affiliation(s)
- A Nagata
- Department of Biochemistry, Saitama Medical School, Japan
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20
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Brik H, Gamliel A, Shainberg A. Characterization of sarcoplasmic reticulum in skinned muscle cultures. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 980:273-80. [PMID: 2713406 DOI: 10.1016/0005-2736(89)90313-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The plasma membranes of chick or rat skeletal muscles, grown in cell culture, were made permeable with saponin in a solution lacking calcium. The cells were then supplied with a medium resembling the cytosol and the ATP-dependent Ca2+ sequestration was performed. Based on the low concentration of free Ca2+ in the medium (below 5 microM), the presence of mitochondrial inhibitors and the effect of drugs that interfere with sarcoplasmic reticulum (SR) function, we assume that the measured Ca2+ accumulation expresses SR function on the saponin-treated myotubes. The development of the SR in muscle cultures is augmented as myogenesis proceeds and depends on its occurrence. Whereas creatine kinase activity is elevated immediately following cell fusion, there is a delay of at least 1 day between myoblast fusion and the increase in Ca2+ accumulation in the SR. Thyroxine or triiodothyronine caused an inhibition of Ca2+ accumulation in rat or chick muscle cultures. This inhibition could explain some of the muscle abnormalities caused by excess of thyroid hormones. A comparison was made between a white-type (fast) and heterogeneous muscle, differentiated in cell culture. There was no significant difference in SR function, indicating the important role of innervation in specifying the properties of muscle fiber types.
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Affiliation(s)
- H Brik
- Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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21
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Das DK, Engelman RM, Prasad MR, Rousou JA, Breyer RH, Jones R, Young H, Cordis GA. Improvement of ischemia-reperfusion-induced myocardial dysfunction by modulating calcium-overload using a novel, specific calmodulin antagonist, CGS 9343B. Biochem Pharmacol 1989; 38:465-71. [PMID: 2917008 DOI: 10.1016/0006-2952(89)90386-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The present paper explores the mechanism of calcium-overloaded cardiac cell exocytosis during reperfusion of ischemic myocardium. A novel specific inhibitor of calmodulin, CGS 9343B, was used to pretreat an ischemic heart in an effort to enhance myocardial preservation. The experimental model employed an isolated in situ pig heart subjected to 120 min of ischemic insult by reversibly occluding the left anterior descending coronary artery, the last 60 min being superimposed with global hypothermic cardioplegic arrest. This ischemic episode was followed by 60 min of revascularization. CGS 9343B enhanced post-ischemic myocardial recovery, as judged by improved regional as well as global myocardial functions, better preservation of high-energy phosphate compounds, and reduced release of creatine kinase. Since this compound blocks calmodulin without inhibiting protein kinase C, the results of this study suggest that calmodulin-dependent kinase, rather than protein kinase C, is primarily involved in expressing calcium-overloaded cell exocytosis, and a specific calmodulin antagonist such as CGS 9343B can be used to salvage an ischemic heart from reperfusion injury.
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Affiliation(s)
- D K Das
- Department of Surgery, University of Connecticut School of Medicine, Farmington 06032
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22
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Smith JS, Rousseau E, Meissner G. Calmodulin modulation of single sarcoplasmic reticulum Ca2+-release channels from cardiac and skeletal muscle. Circ Res 1989; 64:352-9. [PMID: 2536303 DOI: 10.1161/01.res.64.2.352] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Sarcoplasmic reticulum (SR) contains a Ca2+-conducting channel that is believed to play a central role in excitation-contraction coupling by releasing the Ca2+ necessary for muscle contraction. The effects of calmodulin on single cardiac and skeletal muscle SR Ca2+-release channels were studied using the planar lipid bilayer-vesicle fusion technique. Calmodulin inhibited Ca2+-release channel opening by reducing the mean duration of single-channel open events without having an effect on single-channel conductance. Inhibition by calmodulin was dependent on Ca2+ concentration and occurred in the absence of ATP. The effects of calmodulin were reversed by mastoparan, a calmodulin-binding peptide. Two other calmodulin antagonists [calmidazolium and N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide] modified the gating behavior of the channel in the absence of exogenous calmodulin in a concentration- and Ca2+-dependent manner. Our results suggest that calmodulin can modulate excitation-contraction coupling by directly interacting with the SR Ca2+-release channel of cardiac and skeletal muscle.
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Affiliation(s)
- J S Smith
- Department of Biochemistry, School of Medicine, University of North Carolina, Chapel Hill 27599
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23
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de Boland AR, Massheimer V, Fernandez LM. 1,25 Dihydroxyvitamin D3 affects calmodulin distribution among subcellular fractions of skeletal muscle. Calcif Tissue Int 1988; 43:370-5. [PMID: 3146426 DOI: 10.1007/bf02553281] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
1,25 Dihydroxyvitamin D3 has been shown to stimulate calcium fluxes across skeletal muscle membranes. The involvement of calmodulin in the effects of the metabolite was investigated. Primary cultures of chick embryo skeletal muscle myoblasts and soleus muscles from vitamin D-deficient or 1,25 (OH)2D3-treated chicks were used. Culture of myoblasts and vitamin D-deficient soleus with 1,25 (OH)2D3 (0.05 ng/ml) for 24 and 1 hour, respectively, significantly increased 45Ca uptake by the preparations. In the presence of the calmodulin antagonists flufenazine or compound 48/80 in the uptake medium, no differences between control and treated cultures were observed. The calmodulin content of myoblasts and soleus homogenates and subcellular fractions derived therefrom was estimated by measuring their capacity to stimulate calmodulin-depleted cAMP phosphodiesterase. No changes in total calmodulin cellular content could be detected in response to 1,25(OH)2D3. However, the sterol produced an increase in calmodulin levels of microsomes, mitochondria, and crude myofibrillar fraction and a proportional decrease in cytosolic calmodulin concentration. The 1,25(OH)2D3-dependent changes in calmodulin distribution among subcellular fractions of soleus muscle were observed either in vivo or in vitro. The effects in vitro were already detectable after 5 minutes of treatment with the sterol and parallel 1,25(OH)2D3-dependent changes in tissue Ca uptake. The results suggest that changes in calmodulin intracellular distribution may underly part of the mechanism by which 1,25(OH)2D3 affects muscle calcium transport.
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Affiliation(s)
- A R de Boland
- Departmento de Biología, Universidad Nacional del Sur, Argentina
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24
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Taira Y, Ganguly PK, Panagia V, Dhalla NS. Increased SR phospholipid N-methylation in skeletal muscle of diabetic rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1988; 255:E347-52. [PMID: 3138915 DOI: 10.1152/ajpendo.1988.255.3.e347] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Phosphatidylethanolamine (PE) N-methylation was studied in skeletal muscle sarcoplasmic reticulum (SR) 6 wk after the induction of experimental diabetes in rats by an injection of streptozocin (65 mg/kg iv). A significant increase in the incorporation of radiolabeled methyl groups from S-adenosyl-L-methionine (AdoMet) into intramembranal PE was observed in diabetic preparations at 0.055 microM AdoMet, whereas the methylation activity was unaltered at 10 and 150 microM AdoMet concentrations. The increase in PE N-methylation activity was not evident until 28 days after streptozocin injection and was normalized by a 2-wk treatment of diabetic animals with insulin. In the presence of 10 microM of ATP and low concentrations of Ca2+ (0.1 microM), PE N-methylation was maximally activated, but the percent increase was similar in control, diabetes, and insulin-treated diabetes; at 100 microM Ca2+, however, N-methylation activity was depressed only in diabetic preparations. Calmodulin inhibitors such as compound 48/80 and calmidazolium (compound R24571) abolished the effect of Ca2+ and ATP on PE N-methylation in all three groups. Sarcolemmal (SL) PE N-methylation in diabetic skeletal muscle was also found to be increased at 0.055 microM AdoMet. The results suggest that intramembranal calmodulin may participate in regulating PE N-methylation in skeletal muscle membranes, but it may not be responsible for the high N-methylation activity in diabetic rats.
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Affiliation(s)
- Y Taira
- Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada
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25
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Affinity labeling of calmodulin-binding proteins in skeletal muscle sarcoplasmic reticulum. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)37642-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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26
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The multifunctional Ca2+/calmodulin-dependent protein kinase mediates Ca2+-dependent phosphorylation of tyrosine hydroxylase. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)76576-4] [Citation(s) in RCA: 69] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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27
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Lucchesi PA, Scheid CR. Effects of the anti-calmodulin drugs calmidazolium and trifluoperazine on 45Ca transport in plasmalemmal vesicles from gastric smooth muscle. Cell Calcium 1988; 9:87-94. [PMID: 3133116 DOI: 10.1016/0143-4160(88)90028-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The anti-calmodulin drugs calmidazolium (CMZ) and trifluoperazine (TFP) were shown to have a number of effects on 45Ca transport by plasmalemmal vesicles from gastric smooth muscle. Although these compounds produced the expected dose-dependent inhibition of the plasmalemmal ATP-dependent Ca2+ transport system, they also evoked a Ca2+ release comparable to that observed in the presence of the Ca2+ ionophore, ionomycin. This increased transmembrane Ca2+ flux was so large that it accounted for much of the apparent decrease in 45Ca uptake produced by these agents. Thus, direct effects of CMZ and TFP on ATP-dependent 45Ca uptake could only be reliably assessed for brief (less than or equal to 30 seconds) drug exposures. The explanation for the observed effects of CMZ and TFP on membrane Ca2+ permeability is unclear. The increased transmembrane Ca2+ flux may reflect nonspecific effects on membrane permeability or it may reflect a specific interaction of the anticalmodulin drugs with a Ca2+ release channel or with the Ca2+ transport ATPase. In any case, these results suggest the need for caution in the design and interpretation of studies using both CMZ and TFP as anticalmodulin agents.
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Affiliation(s)
- P A Lucchesi
- Department of Physiology, University of Massachusetts Medical School, Worcester
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28
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De Meis L, Tuena de Gómez Puyou M, Gómez Puyou A. Inhibition of mitochondrial F1 ATPase and sarcoplasmic reticulum ATPase by hydrophobic molecules. EUROPEAN JOURNAL OF BIOCHEMISTRY 1988; 171:343-9. [PMID: 2892682 DOI: 10.1111/j.1432-1033.1988.tb13796.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The hydrophobic nature of the active site of two energy-transducing ATPases was explored by comparing interactions between Pi and each of three hydrophobic drugs in the absence and presence of organic solvents. The drugs tested were the Fe . bathophenanthroline complex and the anticalmodulin drugs, calmidazolium and trifluoperazine. All inhibit the Pi in equilibrium with ATP exchange reaction catalyzed by submitochondrial particles and the ATPase activity of both submitochondrial particles and soluble F1 ATPase. The inhibition by the three drugs is reversed by either raising the Pi concentration or by adding organic solvent (dimethylsulfoxide, ethyleneglycol or methanol) to the medium. The inhibition of the Pi in equilibrium with ATP exchange by trifluoperazine becomes more pronounced when the electrochemical proton gradient formed across the membrane of the submitochondrial particles is decreased by the addition to the medium of the proton ionophore carbonylcyanide p-trifluoromethoxyphenylhydrazone. The ATPase activity and the Ca2+ uptake by sarcoplasmic reticulum vesicles are inhibited by the Fe . bathophenanthroline complex, calmidazolium and trifluoperazine. Phosphorylation of the ATPases by Pi, synthesis of ATP from ADP and Pi and the fast efflux of Ca2+ observed during reversal of the Ca2+ pump are inhibited by the three drugs. The inhibition is reversed by raising the concentration of Pi or dimethylsulfoxide. The three drugs tested appear to compete with Pi for a common binding site on the Ca2+-ATPase. The data presented are interpreted according to the proposal that the catalytic site of an enzyme involved in energy transduction undergoes a hydrophobic-hydrophilic transition during the catalytic cycle.
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Affiliation(s)
- L De Meis
- Departamento de Bioquímica, Universidade Federal do Rio de Janeiro, Brazil
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29
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Breitbart H, Rubinstein S. Effect of calmodulin antagonists on calcium pump of ram spermatozoa plasma membrane. ARCHIVES OF ANDROLOGY 1988; 20:229-35. [PMID: 3142380 DOI: 10.3109/01485018808987077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Plasma membranes isolated from ram spermatozoa contain calmodulin, which represents approximately 0.03% of the total sperm calmodulin and 0.025% of the membrane protein. When membranes were isolated in the presence of ethylene glycol (beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA), the amount of calmodulin associated with the plasma membranes was reduced by only 20%. The ATP-dependent calcium transport activity of the isolated plasma membranes is not enhanced by adding calmodulin and not inhibited by the calmodulin antagonists trifluoperazinc (TFP), compound 48/80, or calmidazolium. In fact, there is an enhancement of calcium uptake by the calmodulin antagonists and this enhancement can be blocked by the Ca2+-channel blocker D-600. It is suggested that the ATP-dependent calcium transport activity in the plasma membrane of ram spermatozoa is not regulated by calmodulin.
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Affiliation(s)
- H Breitbart
- Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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30
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Kraus-Friedmann N, Fleschner CR, Zimniak P, Moore P. The hepatic microsomal Ca2+ sequestering system. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1988; 232:59-68. [PMID: 2975144 DOI: 10.1007/978-1-4757-0007-7_6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- N Kraus-Friedmann
- Dept. of Physiology and Cell Biology, University of Texas Medical School, Houston 77225
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31
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Chan KM, Delfert DM, Koepnick SL, McDonald JM. Effect of W7 on Ca2+ uptake and Ca2+-ATPase activities of the endoplasmic reticulum of rat liver. Arch Biochem Biophys 1987; 256:472-9. [PMID: 2956927 DOI: 10.1016/0003-9861(87)90604-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In an initial attempt to use calmodulin antagonists as probes to study the role of calmodulin in the modulation of Ca2+ uptake activity in the endoplasmic reticulum of rat liver, we noticed that W7 had a differential effect on the Ca2+ uptake and Ca2+-ATPase activities. To test the specificity of this effect and explore the underlying mechanism, we examined the effects of W7 on Ca2+ accumulation and release by endoplasmic reticulum in both permeabilized hepatocytes and a subcellular membrane fraction (microsomes) enriched in endoplasmic reticulum. W7 reduced the steady-state Ca2+ accumulation in both preparations in a dose-dependent fashion but the half-maximal inhibitory concentrations were different for Ca2+ accumulation (90 microM) and Ca2+-ATPase activity (500 microM). Kinetic analysis indicated that the inhibition of both Ca2+ uptake and Ca2+-ATPase activity by W7 was noncompetitive with respect to Ca2+ and ATP. Addition of W7 did not enhance the rate of Ca2+ efflux from microsomes after Ca2+ influx had been terminated. The effect of W7 was apparently not related to its calmodulin antagonist properties as the phenomenon could not be demonstrated with the other more specific calmodulin antagonists, calmidazolium or compound 48/80. A similar observation with W7 has also been reported with the endoplasmic reticulum of pancreatic islets (B. A. Wolf, J. R. Colca, and M. L. McDaniel (1986) Biochem. Biophys. Res. Commun. 141, 418-425). We concluded that the effects of W7 on microsomal Ca2+ handling were not the result of increased membrane permeability to Ca2+ but rather were due to dissociation of Ca2+ uptake from Ca2+-ATPase activity.
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32
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Imagawa T, Leung AT, Campbell KP. Phosphorylation of the 1,4-dihydropyridine receptor of the voltage-dependent Ca2+ channel by an intrinsic protein kinase in isolated triads from rabbit skeletal muscle. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)47568-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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33
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Okabe E, Kato Y, Sasaki H, Saito G, Hess ML, Ito H. Calmodulin participation in oxygen radical-induced cardiac sarcoplasmic reticulum calcium uptake reduction. Arch Biochem Biophys 1987; 255:464-8. [PMID: 3036009 DOI: 10.1016/0003-9861(87)90416-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of scavengers of oxygen radicals on canine cardiac sarcoplasmic reticulum (SR) Ca2+ uptake velocity was investigated at pH 6.4, the intracellular pH of the ischemic myocardium. With the generation of oxygen radicals from a xanthine-xanthine oxidase reaction, there was a significant depression of SR Ca2+ uptake velocity. Xanthine alone or xanthine plus denatured xanthine oxidase had no effect on this system. Superoxide dismutase (SOD), a scavenger of .O2-, or denatured SOD had no effect on the depression of Ca2+ uptake velocity induced by the xanthine-xanthine oxidase reaction. However, catalase, which can impair hydroxyl radical (.OH) formation by destroying the precursor H2O2, significantly inhibited the effect of the xanthine-xanthine oxidase reaction. This effect of catalase was enhanced by SOD, but not by denatured SOD. Dimethyl sulfoxide (Me2SO), a known .OH scavenger, completely inhibited the effect of the xanthine-xanthine oxidase reaction. The observed effect of oxygen radicals and radical scavengers was not seen in the calmodulin-depleted SR vesicles. Addition of exogenous calmodulin, however, reproduced the effect of oxygen radicals and the scavengers. The effect of oxygen radicals was enhanced by the calmodulin antagonists (compounds 48/80 and W-7) at concentrations which showed no effect alone on Ca2+ uptake velocity. Taken together, these findings strongly suggest that .OH, but not .O2-, is involved in a mechanism that may cause SR dysfunction, and that the effect of oxygen radicals is calmodulin dependent.
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34
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Enouf J, Giraud F, Bredoux R, Bourdeau N, Levy-Toledano S. Stimulation of the 23-Kd protein cAMP dependent phosphorylation by inositol 1,4,5 trisphosphate in human platelet membrane vesicles. Biochem Biophys Res Commun 1987; 145:139-45. [PMID: 3496086 DOI: 10.1016/0006-291x(87)91298-8] [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: 01/06/2023]
Abstract
The effect of inositol 1,4,5 trisphosphate (IP3) has been investigated on the cAMP-induced phosphorylation of the 23-Kd protein involved in platelet calcium fluxes by isolated membrane vesicles. The studies were conducted using the catalytic subunit of the cAMP-dependent protein kinase (C. Sub.). A dose-dependent stimulation of the 23 Kd protein phosphorylation induced by C. Sub. was initiated by IP3 with a half-maximal effect of 0.5 microM. The maximal effect was observed after 1-2 min. The effect was detected in the absence of Ca2+ and in the presence of phosphatase inhibitors. These results can suggest that the 23 Kd is an associated protein to the IP3 receptor in human platelets.
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35
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Enouf J, Giraud F, Bredoux R, Bourdeau N, Levy-Toledano S. Possible role of a cAMP-dependent phosphorylation in the calcium release mediated by inositol 1,4,5-trisphosphate in human platelet membrane vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 928:76-82. [PMID: 3030449 DOI: 10.1016/0167-4889(87)90087-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The addition of inositol 1,4,5-trisphosphate (IP3) to a 45Ca-preloaded human platelet membrane fraction (dense tubular system) induced a transient release of Ca2+. When the vesicle fraction was loaded with 45Ca2+ to isotopic equilibrium in the presence of the catalytic subunit of the cAMP-dependent protein kinase, the level of Ca2+ uptake was increased and the subsequent IP3-induced Ca2+ release was enhanced. The stimulation was observed regardless of the IP3 concentration used, and was maximal with an enzyme concentration of 5 micrograms/ml. The addition of the protein kinase inhibitor prevented the stimulatory effect of the catalytic subunit on IP3-induced calcium release, and also abolished the calcium release detected in the absence of added enzyme. It is concluded that a cAMP-dependent protein phosphorylation may be involved in the regulation of the IP3-induced Ca2+ release in human platelets.
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36
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Filipovic I, Buddecke E. Calmodulin antagonists suppress cholesterol synthesis by inhibiting sterol delta 24 reductase. Lipids 1987; 22:261-5. [PMID: 3037232 DOI: 10.1007/bf02533989] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Preincubation of hepatoma cells and human skin fibroblasts in the presence of the calmodulin antagonists trifluoperazine and N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide resulted in a dose-dependent suppression of [14C]mevalonolactone incorporation into cholesterol. At a calmodulin antagonist concentration of 25 mumol, the incorporation of [14C]mevalonolactone into cellular cholesterol was suppressed to about 30% (hepatoma cells) and 10% (human skin fibroblasts) of control values. When the total nonsaponifiable [14C]lipids were separated and analyzed by two-dimensional thin layer chromatography, an accumulation of [14C]desmosterol was observed along with reduced formation of [14C]cholesterol. However, when cells were preincubated in the presence of [14C]dihydrolanosterol, [14C]cholesterol formation was not inhibited by the calmodulin antagonists. About 25% of the cell-associated dihydrolanosterol radioactivity was converted to cholesterol in both control and calmodulin antagonist-pretreated cells. The data suggest that calmodulin antagonists prevent the conversion of desmosterol into cholesterol by inhibiting sterol delta 24 reductase and that the enzymes catalyzing sterol ring modifications are not affected by the inhibitors.
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Rapid calcium release from cardiac sarcoplasmic reticulum vesicles is dependent on Ca2+ and is modulated by Mg2+, adenine nucleotide, and calmodulin. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)61469-3] [Citation(s) in RCA: 181] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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38
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Chiesi M, Guerini D. Characterization of heart cytosolic proteins capable of modulating calcium uptake by the sarcoplasmic reticulum. 1. Isolation of a protein with protective activity and its identification as muscle albumin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 162:365-70. [PMID: 2948823 DOI: 10.1111/j.1432-1033.1987.tb10610.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A new type of regulation of the Ca-pumping activity of isolated sarcoplasmic reticulum membranes has been investigated. An inhibitory and an antagonistic fraction were obtained after (NH4)2SO4 fractionation of cardiac muscle cytosol according to a published procedure [Narayanan et al. (1983) Biochem. Biophys. Acta 735, 53-66]. The former fraction inhibited Ca uptake by sarcoplasmic reticulum vesicles in a concentration-dependent way. The inhibition could be prevented and even reversed by addition of the antagonistic fraction. The protein components of this latter fraction were resolved and separated using an anion-exchange chromatographic procedure (mono Q column in an FPLC system). A pure protein component with antagonistic properties was isolated. Biochemical (molecular mass, tryptic digestion pattern and antagonistic activity) and immunological (cross-reactivity with specific antibodies) analysis resulted in the identification of the purified antagonist protein as muscle albumin, a serum-albumin-like protein which is localized near the A/I junctions in the striated muscle cells. The protein may be involved in the regulation of Ca fluxes across the cisternal compartments of the sarcoplasmic reticulum.
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Wolf BA, Colca JR, McDaniel ML. Calmodulin inhibits inositol trisphosphate-induced Ca2+ mobilization from the endoplasmic reticulum of islets. Biochem Biophys Res Commun 1986; 141:418-25. [PMID: 2948504 DOI: 10.1016/s0006-291x(86)80189-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
IP3-induced Ca2+ release from the endoplasmic reticulum (ER) of islets is believed to be a key intracellular event in glucose-induced insulin secretion. Calmodulin was shown to increase ATP-dependent Ca2+ steady-state and inhibit by 57.2% IP3-induced Ca2+ mobilization from the ER. Conversely, the calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphtalene sulfonamide (W-7), induced Ca2+ release from the ER. The combination of W-7 (100 microM) and IP3 (10 microM), resulted in a greater release of Ca2+ from the ER than either W-7 or IP3 alone. W-7 was shown not to affect the structural integrity of the ER. Our results suggest that IP3-induced Ca2+ release from the ER is regulated by a calmodulin-dependent process.
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40
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Shenolikar S, Lickteig R, Hardie DG, Soderling TR, Hanley RM, Kelly PT. Calmodulin-dependent multifunctional protein kinase. Evidence for isoenzyme forms in mammalian tissues. EUROPEAN JOURNAL OF BIOCHEMISTRY 1986; 161:739-47. [PMID: 3539597 DOI: 10.1111/j.1432-1033.1986.tb10502.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Calcium/calmodulin-dependent multifunctional protein kinases, extensively purified from rat brain (with apparent molecular mass 640 kDa), rabbit liver (300 kDa) and rabbit skeletal muscle (700 kDa), were analysed for their structural, immunological, and enzymatic properties. The immunological cross-reactivity with affinity-purified polyclonal antibodies to the 50-kDa catalytic subunit of the brain calmodulin-dependent protein kinase confirmed the presence of common antigenic determinants in all subunits of the protein kinases. One-dimensional phosphopeptide patterns, obtained by digestion of the autophosphorylated protein kinases with S. aureus V8 protease, and two-dimensional fingerprints of the 125I-labelled proteins digested with a combination of trypsin and chymotrypsin, revealed a close similarity between the two subunits (51 kDa and 53 kDa) of the liver enzyme. Similar identity was observed between the 56-kDa and/or 58-kDa polypeptides of the skeletal muscle calmodulin-dependent protein kinase. The data suggest that the subunits of the liver and muscle protein kinases may be derived by partial proteolysis or by autophosphorylation. The peptide patterns for the 50-kDa and 60-kDa subunits of the brain enzyme confirmed that the two catalytic subunits represented distinct protein products. The comparison of the phosphopeptide maps and the two-dimensional peptide fingerprints, indicated considerable structural homology among the 50-kDa and 60-kDa subunits of the brain calmodulin-dependent protein kinase and the liver and muscle polypeptides. However, a significant number of unique peptides in the liver 51-kDa subunit, skeletal muscle 56-kDa, and the brain 50-kDa and 60-kDa polypeptides were observed and suggest the existence of isoenzyme forms. All calmodulin-dependent protein kinases rapidly phosphorylated synapsin I with a stoichiometry of 3-5 mol phosphate/mol protein. The two-dimensional separation of phosphopeptides obtained by tryptic/chymotryptic digestion of 32P-labelled synapsin I indicated that the same peptides were phosphorylated by all the calmodulin-dependent protein kinases. Such data represent the first structural and immunological comparison of the liver calmodulin-dependent protein kinase with the enzymes isolated from brain and skeletal muscle. The findings indicate the presence of a family of highly conserved calmodulin-dependent multifunctional protein kinases, with similar structural, immunological and enzymatic properties. The individual catalytic subunits appear to represent the expression of distinct protein products or isoenzymes which are selectively expressed in mammalian tissues.
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41
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Alves EW, de Meis L. Effect of compound 48/80 and ruthenium red on the Ca2+-ATPase of sarcoplasmic reticulum. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)75966-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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42
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Zorzato F, Margreth A, Volpe P. Direct photoaffinity labeling of junctional sarcoplasmic reticulum with [14C]doxorubicin. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)69298-1] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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43
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Kim DH, Ikemoto N. Involvement of 60-kilodalton phosphoprotein in the regulation of calcium release from skeletal muscle sarcoplasmic reticulum. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67296-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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44
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Yen A, Freeman L, Powers V, Van Sant R, Fishbaugh J. Cell cycle dependence of calmodulin levels during HL-60 proliferation and myeloid differentiation. No changes during pre-commitment. Exp Cell Res 1986; 165:139-51. [PMID: 2940106 DOI: 10.1016/0014-4827(86)90539-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The putative role of Ca2+ and calmodulin in regulating cell proliferation and differentiation was tested in HL-60 human promyelocytic leukemia cells. The dependence of retinoic acid (RA)-induced terminal myeloid differentiation of HL-60 promyelocytic leukemia cells on calmodulin levels and calcium ion flux was ascertained. RA-treated and untreated control cells were stained for cellular DNA with a Hoechst dye. Populations of G1/0, S and G2 + M phase cells were isolated by fluorescence activated cell sorting (FACS). Cytosolic calmodulin levels were then measured as a function of cell cycle phase for RA-treated and untreated cells using a radioimmunoassay. RA-treated cells were measured at early times, corresponding to the pre-commitment state, and late times, when significant cell differentiation had occurred. Cellular calmodulin levels increased with progression through the cell cycle. In contrast, no difference in calmodulin levels was observed between RA-untreated or -treated cells in the same cell cycle phases at early or late times. RA-induced HL-60 terminal myeloid differentiation was thus apparently not regulated by cellular cytosolic calmodulin levels. These conclusions were supported by the effects of calmodulin antagonists and calcium flux inhibitors. The calmodulin antagonists trifluoperazine and compound 48/80 both retarded cell growth in a concentration-dependent manner. But at concentrations where cellular effect was evidenced by slight growth inhibition, neither antagonist inhibited RA-induced cell differentiation or G1/0 growth arrest. The same was true of the gated calcium channel inhibitors, verapamil and nitrendipene, and the passive calcium flux inhibitor, CoCl2. RA-induced HL-60 cell differentiation and arrest in G0 was thus apparently not strongly dependent on cellular calmodulin levels or calcium flux. This is in strong contrast to murine erythroleukemia cells. The results argue against a central regulatory role for calmodulin or calcium flux in control of HL-60 growth arrest or differentiation.
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Calmodulin antagonists stimulate LDL receptor synthesis in human skin fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 876:124-32. [PMID: 2418882 DOI: 10.1016/0005-2760(86)90325-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The LDL receptor synthesis of human skin fibroblasts in the presence of the specific calmodulin antagonists trifluoperazine, condensation product of N-methyl-p-methoxyphenethylamine with formaldehyde (compound 48/80) and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide) (W-7) was studied. Labelling of cells with [35S]methionine followed by immunoprecipitation of radioactive LDL receptor protein with monospecific antibodies revealed that calmodulin antagonists caused a 3-fold increase in the radioactivity of the LDL receptor protein as compared with values found in control cells. A corresponding increase of high-affinity binding and internalization of 125I-labelled LDL was observed. The drugs did not influence the overall protein synthesis or the half-life of the LDL receptor. A concomitant suppression of cholesterol synthesis from [14C]mevalonolactone was found to be an independent effect. The calmodulin antagonist-produced stimulation of LDL receptor synthesis could not be simulated by preincubation of cells with cyclic nucleotide analogues, cholera toxin or 3-isobutyl-1-methylxanthine, known as specific effectors of adenylate cyclase and cyclic nucleotide phosphodiesterase, respectively. Modulation of calcium concentration in the incubation medium had no reproducible effect on the rate of LDL receptor synthesis. The results implicate calmodulin as an intracellular suppressor of LDL receptor synthesis in human skin fibroblasts.
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46
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Comparison between calcium transport and adenosine triphosphatase activity in membrane vesicles derived from rabbit kidney proximal tubules. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)35654-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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47
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Fleschner CR, Kraus-Friedmann N. The effect of Mg2+ on hepatic microsomal Ca2+ and Sr2+ transport. EUROPEAN JOURNAL OF BIOCHEMISTRY 1986; 154:313-20. [PMID: 2935394 DOI: 10.1111/j.1432-1033.1986.tb09399.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The ATP-dependent uptake of Ca2+ by rat liver microsomal fraction is dependent upon Mg2+. Studies of the Mg2+ requirement of the underlying microsomal Ca2+-ATPase have been hampered by the presence of a large basal Mg2+-ATPase activity. We have examined the effect of various Mg2+ concentrations on Mg2+-ATPase activity, Ca2+ uptake, Ca2+-ATPase activity and microsomal phosphoprotein formation. Both Mg2+-ATPase activity and Ca2+ uptake were markedly stimulated by increasing Mg2+ concentration. However, the Ca2+-ATPase activity, measured concomitantly with Ca2+ uptake, was apparently unaffected by changes in the Mg2+ concentration. In order to examine the apparent paradox of Mg2+ stimulation of Ca2+ uptake but not of Ca2+-ATPase activity, we examined the formation of the Ca2+-ATPase phosphoenzyme intermediate and formation of a Mg2+-dependent phosphoprotein, which we have proposed to be an attribute of the Mg2+-ATPase activity. We found that Ca2+ apparently inhibited formation of the Mg2+-dependent phosphoprotein both in the absence and presence of exogenous Mg2+. This suggests that Ca2+ may inhibit (at least partially) the Mg2+-ATPase activity. However, inclusion of the Ca2+ inhibition of Mg2+-ATPase activity in the calculation of Ca2+-ATPase activity reveals that this effect is insufficient to totally account for the stimulation of Ca2+ uptake by Mg2+. This suggests that Mg2+, in addition to stimulation of Ca2+-ATPase activity, may have a direct stimulatory effect on Ca2+ uptake in an as yet undefined fashion. In an effort to further examine the effect of Mg2+ on the microsomal Ca2+ transport system of rat liver, the interaction of this system with Sr2+ was examined. Sr2+ was sequestered into an A23187-releasable space in an ATP-dependent manner by rat liver microsomal fraction. The uptake of Sr2+ was similar to that of Ca2+ in terms of both rate and extent. A Sr2+-dependent ATPase activity was associated with the Sr2+ uptake. Sr2+ promoted formation of a phosphoprotein which was hydroxylamine-labile and base-labile. This phosphoprotein was indistinguishable from the Ca2+-dependent ATPase phosphoenzyme intermediate. Sr2+ uptake was markedly stimulated by exogenous Mg2+, but the Sr2+-dependent ATPase activity was unaffected by increasing Mg2+ concentrations. Sr2+ uptake and Sr2+-dependent ATPase activity were concomitantly inhibited by sodium vanadate. In contrast to Ca2+, Sr2+ had no effect on Mg2+-dependent phosphoprotein formation. Taken together, these data indicate that Mg2+ stimulated Ca2+ and Sr2+ transport by increasing the Ca2+ (Sr2+)/ATP ratio.(ABSTRACT TRUNCATED AT 400 WORDS)
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Meissner G. Evidence of a role for calmodulin in the regulation of calcium release from skeletal muscle sarcoplasmic reticulum. Biochemistry 1986; 25:244-51. [PMID: 3754148 DOI: 10.1021/bi00349a034] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The effect of calmodulin and calmodulin inhibitors on the "Ca2+ release channel" of "heavy" skeletal muscle sarcoplasmic reticulum (SR) vesicles was investigated. SR vesicles were passively loaded with 45Ca2+ in the presence of calmodulin and its inhibitors, followed by measurement of 45Ca2+ release rates by means of a rapid-quench-Millipore filtration method. Calmodulin at a concentration of 2-10 microM reduced 45Ca2+ efflux rates from passively loaded vesicles by a factor of 2-3 in media containing 10(-6)-10(-3) M Ca2+. At 10(-9) M Ca2+, calmodulin was without effect. 45Ca2+ release rates were varied 1000-fold (k1 approximately equal to 0.1-100 s-1) by using 10(-5) M Ca2+ with either Mg2+ or the ATP analogue adenosine 5'-(beta,gamma-methylenetriphosphate) in the release medium. In all instances, a similar 2-3-fold reduction in release rates was observed. At 10(-5) M Ca2+, 45Ca2+ release was half-maximally inhibited by about 2 X 10(-7) M calmodulin, and this inhibition was reversible. Heavy SR vesicle fractions contained 0.1-02 micrograms of endogenous calmodulin/mg of vesicle protein. However, the calmodulin inhibitors trifluoperazine, calmidazolium, and compound 48/80 were without significant effect on 45Ca2+ release at concentrations which inhibit calmodulin-mediated reactions in other systems. Studies with actively loaded vesicles also suggested that heavy SR vesicles contain a Ca2+ permeation system that is inhibited by calmodulin.
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49
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Stull JT, Nunnally MH, Michnoff CH. 4 Calmodulin-Dependent Protein Kinases. ACTA ACUST UNITED AC 1986. [DOI: 10.1016/s1874-6047(08)60429-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
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50
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Gill DL, Chueh SH. An intracellular (ATP + Mg2+)-dependent calcium pump within the N1E-115 neuronal cell line. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)39365-1] [Citation(s) in RCA: 49] [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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