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Ferrante C, Szappanos H, Csernoch L, Weisleder N. Analysis of osmotic stress induced Ca2+ spark termination in mammalian skeletal muscle. Indian J Biochem Biophys 2013; 50:411-418. [PMID: 24772962 PMCID: PMC4082817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Ca2+ sparks represent synchronous opening of the ryanodine receptor (RyR) Ca2+ release channels located at the sarcoplasmic reticulum (SR) membrane. Whereas a quantal nature of Ca2+ sparks has been defined in cardiac muscle, the regulation of Ca2+ sparks in skeletal muscle has not been well-studied. Osmotic-stress applied to an intact skeletal muscle fiber can produce brief Ca2+ sparks and prolonged Ca2+ burst events. Here, we show that termination of Ca2+ bursts occurs in a step wise and quantal manner. Ca2+ burst events display kinetic features that are consistent with the involvement of both stochastic attrition and coordinated closure of RyR channels in the termination of SR Ca2+ release. Elemental unitary transition steps could be defined with a mean deltaF/F0 of approximately 0.28. corresponding to the gating of 1-2 RyR channels. Moreover, the amplitude of the elemental transition steps declines at the later stage of the burst event. In tandem Ca2+ burst events where two Ca2+ bursts occur at the same position within a fiber in rapid succession, the trailing event is consistently of lower amplitude than the initial event. These two complementary results suggest that SR Ca2+ release may be associated with local depletion of SR Ca2+ stores in mammalian skeletal muscle.
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Affiliation(s)
- Christopher Ferrante
- Department of Physiology and Biophysics, Robert Wood Johnson Medical School, 675 Hoes Lane Piscataway, NJ 08854, USA
| | - Henrietta Szappanos
- Department of Physiology and Biophysics, Robert Wood Johnson Medical School, 675 Hoes Lane Piscataway, NJ 08854, USA
| | - László Csernoch
- Department of Physiology, Medical and Health Science Center, University of Debrecen, Nagyerdei krt. 98, Debrecen, Hungary
| | - Noah Weisleder
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W 12th Ave, Columbus, OH 43210, USA
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Szucs A, Szappanos H, Batta TJ, Tóth A, Szigeti GP, Panyi G, Csernoch L, Sziklai I. Changes in purinoceptor distribution and intracellular calcium levels following noise exposure in the outer hair cells of the guinea pig. J Membr Biol 2007; 213:135-41. [PMID: 17468959 DOI: 10.1007/s00232-006-0045-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2006] [Revised: 10/05/2006] [Indexed: 11/29/2022]
Abstract
Among the cells of the inner ear, the outer hair cells (OHCs) are the most important targets of noise-induced effects, being the most sensitive cell types. The aim of this study was to examine the effects of noise (50 Hz-20 kHz, 80 dB sound pressure level, 14 days) on intracellular calcium levels and on the expression pattern of purinoceptors in the membrane of the OHCs of the guinea pig and to measure the stiffness changes of the lateral membrane of these cells. In noise-exposed animals, the resting intracellular calcium concentration increased compared to nontreated animals and was slightly higher in the cells of the basal (219 +/- 29 nM: ) than in the apical (181 +/- 24 nM: ) turns of the cochlea. After application of 180 muM: adenosine triphosphate, the intracellular calcium level rose by 60 +/- 22 nM: in cells from the apical and by 44 +/- 10 nM: in cells from the basal turns, significantly less than in nontreated animals. Expression of the P(2X1), P(2X2), P(2X4), P(2X7), P(2Y1) and P(2Y4) receptor subtypes was suppressed, while expression of the P(2Y2) subtype did not decrease in either of the two preparations. In parallel with the increase in intracellular calcium concentration, the stiffness of the lateral wall of the OHCs was increased. Noise-induced changes in intracellular calcium homeostasis and subsequently in the calcium-dependent regulatory mechanisms may modify OHC lateral wall stiffness and may lead to reduction of the efficacy of the cochlear amplifier.
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Affiliation(s)
- Attila Szucs
- Department of Otolaryngology and Head and Neck Surgery, Medical and Health Science Center, Medical School, University of Debrecen, Nagyerdei krt. 98, 4012, Debrecen, Hungary.
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Deli T, Tóth BI, Czifra G, Szappanos H, Bíró T, Csernoch L. Differences in purinergic and voltage-dependent signalling during protein kinase Calpha overexpression- and culturing-induced differentiation of C2C12 myoblasts. J Muscle Res Cell Motil 2006; 27:617-30. [PMID: 17051344 DOI: 10.1007/s10974-006-9096-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Accepted: 08/03/2006] [Indexed: 10/24/2022]
Abstract
Differentiation of skeletal muscle cells both in vivo and in vitro is accompanied by the development of voltage-dependent processes and alterations in purinergic signalling. To date at least two independent methods have been used to induce differentiation in primary cultures, namely, appropriate modification of culturing conditions and overexpression of specific protein kinase C (PKC) isoenzymes. Here we characterize and compare the development of purinergic and depolarization-dependent alterations using these two methods to induce differentiation in C2C12 cells. We demonstrate that depolarization- and ATP-evoked Ca(2+) responses underwent functional development during differentiation, and the characteristics of this progress were dependent on the actual differentiation-promoting stimulus. Overexpression of PKCalpha anticipated the appearance of robust increases in the intracellular calcium concentration upon ATP administration but failed to do so after depolarizing stimuli. Moreover, the first phase of the biphasic ATP-induced response observed in differentiated myotubes induced by culturing was not present in differentiated PKCalpha-overexpressing cells, suggesting that although purinergic signalling developed very early, purinergic stimuli failed to activate the voltage-dependent mechanisms of these cells even at subsequent stages of differentiation. Disruption of the coupling of purinergic signalling to depolarization-activated mechanisms may be explained by our observations that PKCalpha-overexpression changed the purinergic receptor pattern of immature myoblasts differently from what was seen in the course of culturing-induced differentiation. PKCalpha-specific alterations were characterized by the lack of increase in the expression of P2X(7) receptors and the failure of P2Y(4) receptors to appear and P2Y(2) receptors to disappear. The effects of PKCalpha-overexpression were proven to be specific since the overexpression of the hyperproliferative isoenzyme PKCdelta failed to induce any of the changes promoted by PKCalpha. Our data suggest that the method of inducing differentiation in skeletal muscle cells modifies not only the course of development but also the interaction of depolarization-dependent and purinergic pathways.
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Affiliation(s)
- Tamás Deli
- Department of Physiology, Medical and Health Science Center, University of Debrecen, Nagyerdei krt. 98, 22, H-4012 Debrecen, Hungary
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Deli T, Szappanos H, Szigeti GP, Cseri J, Kovács L, Csernoch L. Contribution from P2X and P2Y purinoreceptors to ATP-evoked changes in intracellular calcium concentration on cultured myotubes. Pflugers Arch 2006; 453:519-29. [PMID: 17043813 DOI: 10.1007/s00424-006-0146-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Accepted: 08/28/2006] [Indexed: 10/24/2022]
Abstract
Although the alteration of purinoreceptor pattern on skeletal muscle is known to accompany physiological muscle differentiation and the pathogenesis of muscle dystrophy, the exact identity of and the relative contribution from the individual receptor subtypes to the purinergic signal have been controversial. To identify these subtypes in cultured myotubes of 5-10 nuclei, changes in intracellular calcium concentration and surface membrane ionic currents were detected and calcium fluxes calculated after the application of the subtype-specific agonists 2'3'-O-(benzoyl-4-benzoyl)-ATP (BzATP), 2-methyltio-ADP and UTP. The effectiveness of these agonists together with positive immunocytochemical staining revealed the presence of P2X(4), P2X(5), P2X(7), P2Y(1) and P2Y(4) receptors. siRNA-reduced protein expression of P2X(5), P2X(7) and P2Y(1) receptors was accompanied by reduction in the ATP-evoked calcium transients. Furthermore, anti-P2X(7) siRNA caused a significant drop in the early peak and delayed steady component of the calculated calcium flux. The use of its antagonist, oxidized ATP, similarly to transfection with anti-P2X(7) siRNA caused significant reduction in the agonist-elicited ionic currents I (ATP) and I (BzATP), with a greater drop in the latter. Our results demonstrate that the activation of ionotropic P2X(4), P2X(5) and P2X(7) and metabotropic P2Y(1) and P2Y(4) purinoreceptors participates in forming the calcium transients of multinucleated myotubes.
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MESH Headings
- Adenosine Triphosphate/analogs & derivatives
- Adenosine Triphosphate/pharmacology
- Animals
- Biological Transport/drug effects
- Blotting, Western
- Calcium/metabolism
- Cells, Cultured
- Fluorescent Antibody Technique
- Immunohistochemistry
- Membrane Potentials/drug effects
- Mice
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Patch-Clamp Techniques
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- Protein Isoforms/physiology
- RNA, Small Interfering/genetics
- Receptors, Purinergic P2/genetics
- Receptors, Purinergic P2/metabolism
- Receptors, Purinergic P2/physiology
- Receptors, Purinergic P2X
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Affiliation(s)
- Tamás Deli
- Department of Physiology, Medical and Health Science Centre, University of Debrecen, 98 Nagyerdei krt., P.O. Box 22, Debrecen, 4012, Hungary
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Szigeti GP, Szappanos H, Deli T, Cseri J, Kovács L, Csernoch L. Differentiation-dependent alterations in the extracellular ATP-evoked calcium fluxes of cultured skeletal muscle cells from mice. Pflugers Arch 2006; 453:509-18. [PMID: 17021795 DOI: 10.1007/s00424-006-0145-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Accepted: 07/28/2006] [Indexed: 10/24/2022]
Abstract
Although extracellular adenosine triphosphate (ATP) has been generally accepted as the regulator of cellular differentiation, the relative contribution of the various purinoreceptor subtypes to purinergic signalling at distinct stages of skeletal muscle differentiation is still poorly understood. Here we measured extracellular ATP-evoked changes in intracellular calcium concentration and surface membrane ionic currents (I (ATP)), calculated the calcium flux (FL) entering the myoplasmic space and compared these parameters at different stages of differentiation on cultured mouse myotubes. The ATP-evoked FL displayed an early peak and then declined to a steady level. With differentiation, the early peak became separated from the maintained component and was absent on mature myotubes. Repeated ATP applications caused desensitization of the response in both immature and differentiated myotubes, owing mainly to the reduction of the early peak of FL in the former and to a decline of both components in the latter group of cells. Depolarization of the cell or removal of external calcium suppressed the early peak. I (ATP) showed no inactivation, and its voltage dependence displayed strong inward rectification. The concentration dependence of I (ATP) can be fitted using a Hill equation, yielding an EC(50) of 56 microM. Results are consistent with the parallel activation of both P2X and P2Y receptors.
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Affiliation(s)
- Gyula Péter Szigeti
- Department of Physiology, Medical and Health Science Centre, University of Debrecen, P.O. Box 22, 98 Nagyerdei krt., Debrecen, 4012, Hungary
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Szappanos H, Szigeti GP, Pál B, Rusznák Z, Szucs G, Rajnavölgyi E, Balla J, Balla G, Nagy E, Leiter E, Pócsi I, Hagen S, Meyer V, Csernoch L. The antifungal protein AFP secreted by Aspergillus giganteus does not cause detrimental effects on certain mammalian cells. Peptides 2006; 27:1717-25. [PMID: 16500727 DOI: 10.1016/j.peptides.2006.01.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Revised: 01/12/2006] [Accepted: 01/17/2006] [Indexed: 11/15/2022]
Abstract
The antifungal protein AFP is a small, cystein-rich protein secreted by the imperfect ascomycete Aspergillus giganteus. The protein efficiently inhibits the growth of filamentous fungi, including a variety of serious human and plant pathogens mainly of the genera Aspergillus and Fusarium, whereas AFP does not affect the growth of yeast and bacteria. This restricted susceptibility range makes it very attractive for medical or biotechnological use to combat fungal infection and contamination. We, therefore, analyzed whether AFP affects the growth or function of a number of mammalian cells. Here we show that the protein neither provokes any cytotoxic effects on human endothelial cells isolated from the umbilical vein nor activates the immune system. Moreover, potassium currents of neurons and astrocytes do not change in the presence of AFP and neither excitatory processes nor the intracellular calcium homeostasis of cultured skeletal muscle myotubes are affected by AFP. Our data, therefore, suggest that AFP is indeed a promising candidate for the therapeutic or biotechnological use as a potential antifungal agent.
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Affiliation(s)
- Henrietta Szappanos
- Department of Physiology, RCMM, MHSC, University of Debrecen, 98 Nagyerdei krt., Debrecen 4012, Hungary
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7
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Leiter É, Szappanos H, Oberparleiter C, Kaiserer L, Csernoch L, Pusztahelyi T, Emri T, Pócsi I, Salvenmoser W, Marx F. Antifungal protein PAF severely affects the integrity of the plasma membrane of Aspergillus nidulans and induces an apoptosis-like phenotype. Antimicrob Agents Chemother 2005; 49:2445-53. [PMID: 15917545 PMCID: PMC1140496 DOI: 10.1128/aac.49.6.2445-2453.2005] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The small, basic, and cysteine-rich antifungal protein PAF is abundantly secreted into the supernatant by the beta-lactam producer Penicillium chrysogenum. PAF inhibits the growth of various important plant and zoopathogenic filamentous fungi. Previous studies revealed the active internalization of the antifungal protein and the induction of multifactorial detrimental effects, which finally resulted in morphological changes and growth inhibition in target fungi. In the present study, we offer detailed insights into the mechanism of action of PAF and give evidence for the induction of a programmed cell death-like phenotype. We proved the hyperpolarization of the plasma membrane in PAF-treated Aspergillus nidulans hyphae by using the aminonaphtylethenylpyridinium dye di-8-ANEPPS. The exposure of phosphatidylserine on the surface of A. nidulans protoplasts by Annexin V staining and the detection of DNA strand breaks by TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) gave evidence for a PAF-induced apoptotic-like mechanism in A. nidulans. The localization of reactive oxygen species (ROS) by dichlorodihydrofluorescein diacetate and the abnormal cellular ultrastructure analyzed by transmission electron microscopy suggested that ROS-elicited membrane damage and the disintegration of mitochondria played a major role in the cytotoxicity of PAF. Finally, the reduced PAF sensitivity of A. nidulans strain FGSC1053, which carries a dominant-interfering mutation in fadA, supported our assumption that G-protein signaling was involved in PAF-mediated toxicity.
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Affiliation(s)
- Éva Leiter
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
| | - Henrietta Szappanos
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
| | - Christoph Oberparleiter
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
| | - Lydia Kaiserer
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
| | - László Csernoch
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
| | - Tünde Pusztahelyi
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
| | - Tamás Emri
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
| | - István Pócsi
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
| | - Willibald Salvenmoser
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
| | - Florentine Marx
- Department of Microbiology and Biotechnology, Faculty of Science, Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary, Biocenter, Division of Molecular Biology, Innsbruck Medical University, Innsbruck, Austria, Institute of Zoology and Limnology, Division of Ultrastructure and Evolutionary Biology, University of Innsbruck, Innsbruck, Austria
- Corresponding author. Mailing address: Biocenter, Division of Molecular Biology, Innsbruck Medical University, Fritz-Pregl Strasse 3, A-6020 Innsbruck, Austria. Phone: 43-512-5073607. Fax: 43-512-5079880. E-mail:
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Szappanos H, Smida-Rezgui S, Cseri J, Simut C, Sabatier JM, De Waard M, Kovács L, Csernoch L, Ronjat M. Differential effects of maurocalcine on Ca2+ release events and depolarization-induced Ca2+ release in rat skeletal muscle. J Physiol 2005; 565:843-53. [PMID: 15831537 PMCID: PMC1464547 DOI: 10.1113/jphysiol.2005.086074] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Maurocalcine (MCa), a 33 amino acid toxin obtained from scorpion venom, has been shown to interact with the isolated skeletal-type ryanodine receptor (RyR1) and to strongly modify its calcium channel gating. In this study, we explored the effects of MCa on RyR1 in situ to establish whether the functional interaction of RyR1 with the voltage-sensing dihydropyridine receptor (DHPR) would modify the ability of MCa to interact with RyR1. In developing skeletal muscle cells the addition of MCa into the external medium induced a calcium transient resulting from RyR1 activation and strongly inhibited the effect of the RyR1 agonist chloro-m-cresol. In contrast, MCa failed to affect the depolarization-induced Ca(2+) release. In intact adult fibres MCa did not induce any change in the cytosolic Ca(2+) concentration. However, when the surface membrane was permeabilized and calcium release events were readily observable, MCa had a time-dependent dual effect: it first increased event frequency, from 0.060 +/- 0.002 to 0.150 +/- 0.007 sarcomere(-1) s(-1), and reduced the amplitude of individual events without modifying their spatial distribution. Later on it induced the appearance of long-lasting events resembling the embers observed in control conditions but having a substantially longer duration. We propose that the functional coupling of DHPRs and RyR1s within a Ca(2+) release unit prevents MCa from either reaching its binding site or from being able to modify the gating not only of the RyR1s physically coupled to DHPRs but all RyR1s within the Ca(2+) release unit.
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Szappanos H, Szigeti GP, Pál B, Rusznák Z, Szucs G, Rajnavölgyi E, Balla J, Balla G, Nagy E, Leiter E, Pócsi I, Marx F, Csernoch L. The Penicillium chrysogenum-derived antifungal peptide shows no toxic effects on mammalian cells in the intended therapeutic concentration. Naunyn Schmiedebergs Arch Pharmacol 2005; 371:122-32. [PMID: 15702351 DOI: 10.1007/s00210-004-1013-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Accepted: 12/01/2004] [Indexed: 11/24/2022]
Abstract
Certain filamentous fungi, such as the penicillin-producing strain Penicillium chrysogenum, secrete small, highly basic and cysteine-rich proteins with antifungal effects. Affected fungi include a number of important zoopathogens, including those infecting humans. Recent studies, however, have pointed to a membrane-perturbing effect of these antifungal compounds, apparent as a potassium efflux from affected fungal cells. If present on mammalian cells, this would severely hinder the potential therapeutic use of these molecules. Here we studied the effects of the P. chrysogenum-derived antifungal peptide (PAF) on a number of mammalian cells to establish whether the protein has any cytotoxic effects, alters transmembrane currents on excitable cells or activates the immune system. PAF, in a concentration range of 2-100 mug/ml, did not cause any cytotoxicity on human endothelial cells from the umbilical vein. Applied at 10 mug/ml, it also failed to modify voltage-gated potassium channels of neurones, skeletal muscle fibers, and astrocytes. PAF also left the hyperpolarization-activated non-specific cationic current (I(h)) and the L-type calcium current unaffected. Finally, up to 2 mug/ml, PAF did not induce the production of pro-inflammatory cytokines such as IL-6, IL-8, and TNF-alpha. These results suggest that PAF should have only minor, if any, effects on mammalian cells in the intended therapeutic concentration range.
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Affiliation(s)
- Henrietta Szappanos
- Department of Physiology, RCMM, MHSC, University of Debrecen, P.O. Box 22, Debrecen, Hungary
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10
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Szentesi P, Szappanos H, Szegedi C, Gönczi M, Jona I, Cseri J, Kovács L, Csernoch L. Altered elementary calcium release events and enhanced calcium release by thymol in rat skeletal muscle. Biophys J 2004; 86:1436-53. [PMID: 14990472 PMCID: PMC1303980 DOI: 10.1016/s0006-3495(04)74213-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The effects of thymol on steps of excitation-contraction coupling were studied on fast-twitch muscles of rodents. Thymol was found to increase the depolarization-induced release of calcium from the sarcoplasmic reticulum, which could not be attributed to a decreased calcium-dependent inactivation of calcium release channels/ryanodine receptors or altered intramembrane charge movement, but rather to a more efficient coupling of depolarization to channel opening. Thymol increased ryanodine binding to heavy sarcoplasmic reticulum vesicles, with a half-activating concentration of 144 micro M and a Hill coefficient of 1.89, and the open probability of the isolated and reconstituted ryanodine receptors, from 0.09 +/- 0.03 to 0.22 +/- 0.04 at 30 micro M. At higher concentrations the drug induced long-lasting open events on a full conducting state. Elementary calcium release events imaged using laser scanning confocal microscopy in the line-scan mode were reduced in size, 0.92 +/- 0.01 vs. 0.70 +/- 0.01, but increased in duration, 56 +/- 1 vs. 79 +/- 1 ms, by 30 micro M thymol, with an increase in the relative proportion of lone embers. Higher concentrations favored long events, resembling embers in control, with duration often exceeding 500 ms. These findings provide direct experimental evidence that the opening of a single release channel will generate an ember, rather than a spark, in mammalian skeletal muscle.
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Affiliation(s)
- Péter Szentesi
- Department of Physiology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
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Szücs A, Szappanos H, Tóth A, Farkas Z, Panyi G, Csernoch L, Sziklai I. Differential expression of purinergic receptor subtypes in the outer hair cells of the guinea pig. Hear Res 2004; 196:2-7. [PMID: 15464295 DOI: 10.1016/j.heares.2004.04.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2003] [Accepted: 04/06/2004] [Indexed: 12/21/2022]
Abstract
ATP acts as a neuro-modulator through purinoceptors in many different tissues. Many subtypes of these receptors have been identified in the inner ear, but so far only two types have been shown to be present in the membrane of the isolated outer hair cells (OHCs). The aim of this study was to detect and visualize the existence and distribution of purinoceptor subtypes as well as to study the [Ca(2+)](i) response of these cells in response to stimulation with ATP. Four P2X and three P2Y receptor subtypes were identified with different expression pattern in the membrane of guinea pig outer hair cells. Whereas intense labeling was observed for P2X1, P2X2, P2X4, P2Y1, P2Y2, and P2Y4, the labeling for the subtype P2X7 was weak. There was a marked difference in the distribution of the receptors along the surface of the cells with a homogenous distribution in cases of P2X1, P2X4, and P2Y1. In contrast, P2X2 and P2Y2 receptor density was high mainly at the apical, while P2X7 and P2Y4 at the basal pole of the cells. Similarly a heterogeneity was observed in the ATP-induced transient elevation in [Ca(2+)](i), which had either fast kinetics without desensitization or slow rise with desensitization.
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Affiliation(s)
- Attila Szücs
- Department of Otolaryngology and Head and Neck Surgery, Medical and Health Science Centre, Medical School, University of Debrecen, 4012 Debrecen, Hungary.
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Szappanos H, Cseri J, Deli T, Kovács L, Csernoch L. Determination of depolarisation- and agonist-evoked calcium fluxes on skeletal muscle cells in primary culture. ACTA ACUST UNITED AC 2004; 59:89-101. [PMID: 15134910 DOI: 10.1016/j.jbbm.2003.12.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2003] [Revised: 12/04/2003] [Accepted: 12/06/2003] [Indexed: 11/30/2022]
Abstract
Changes in intracellular calcium concentration ([Ca2+]i) evoked by prolonged depolarisation (120 mM KCl) or by the application of 15 mM caffeine were measured on skeletal muscle cells in primary culture. The extrusion rate (PVmax) of calcium from the myoplasm was determined, which in turn enabled the calculation of the calcium flux (Fl) underlying the measured calcium transients. PVmax was found to increase during differentiation, from 107 +/- 10 microM/s at the early myotube stage to 596 +/- 36 microM/s in secondary myotubes. This was paralleled by a decrease in resting [Ca2+]i from 99 +/- 4 to 51 +/- 2 nM. The depolarisation-evoked Fl rose to peak and then ceased despite the continuous presence of KCl. In contrast, the caffeine-induced Fl showed a peak and a clear steady-level with a peak-to-steady ratio of 5.6 +/- 1.2. Removal of external calcium suppressed the depolarisation--induced flux by 88 +/- 5% indicating that both an influx and a release from the SR underlie the K(+)-evoked calcium transients. Subsequent applications of caffeine resulted in essentially identical fluxes indicating an efficient refilling of the internal stores. Moreover, if a depolarisation-induced calcium transient preceded the second caffeine-evoked release, the latter was significantly larger than the first suggesting that much of the calcium that entered was stored in the SR rather than extruded.
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Affiliation(s)
- Henrietta Szappanos
- Department of Physiology, Research Center for Molecular Medicine, Medical and Health Sciences Centre, University of Debrecen, Hungary
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Cseri J, Szappanos H, Szigeti GP, Csernátony Z, Kovács L, Csernoch L. A purinergic signal transduction pathway in mammalian skeletal muscle cells in culture. Pflugers Arch 2002; 443:731-8. [PMID: 11889570 DOI: 10.1007/s00424-001-0757-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2001] [Accepted: 10/31/2001] [Indexed: 11/29/2022]
Abstract
The effects of adenosine 5'-triphosphate (ATP) on human and mouse skeletal muscle fibres in primary culture were investigated. ATP-evoked changes in intracellular calcium concentration ([Ca(2+)](i)) were measured and compared with those induced by agonists of the nicotinic acetylcholine (Ach)- and P2X purinoreceptors. While ATP was effective on both myoblasts and multi-nucleated myotubes in the micromolar range, Ach failed to induce any change in [Ca(2+)](i) at early stages of development. In contrast, myofibres with peripheral nuclei showed little response to ATP but responded to Ach with a large change in [Ca(2+)](i). The responsiveness of the myotubes to Ach paralleled that to potassium. The removal of external calcium abolished the response to ATP. P2X receptor agonists mimicked the response to ATP with the order of potency being ATP>2',3'- O-(4-benzoyl)-benzoyl-ATP>beta,gamma-methylene-ATP>alpha,beta-methylene-ATP. Under voltage-clamp conditions ATP induced an inward current that showed little inactivation. These results are consistent with the existence of P2X receptor-mediated signal transduction pathway in cultured mammalian skeletal muscle cells.
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Affiliation(s)
- Julianna Cseri
- Department of Physiology, Medical and Health Science Centre, University of Debrecen, Debrecen, P.O.Box 22, 4012 Hungary
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