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Publications (30)

  • László Csernoch · János Fodor · Dána Al-Gaadi · [...] · Péter Szentesi
    Article · Feb 2017
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    [Show abstract] [Hide abstract] ABSTRACT: Marijuana was found to cause muscle weakness, but it is unknown whether it affects the muscles directly, or modulates only the motor control of the central nervous system. Although the presence of CB1 cannabinoid receptors (CB1R) - responsible for the psychoactive effects of the drug in the brain - have recently been shown in skeletal muscle, it is unclear how CB1R-mediated signalling affects the contraction and Ca²⁺ homeostasis of mammalian skeletal muscle. Here we demonstrate that in vitro CB1R activation increased muscle fatigability, decreased the Ca(2+) -sensitivity of the contractile apparatus, but did not alter the amplitude of single twitch contractions. In myotubes, CB1R agonists neither evoked or influenced IP3 -mediated Ca(2+) transients, nor altered excitation-contraction coupling. In contrast, in isolated muscle fibres of wild type mice, although CB1R agonists did not evoke IP3 -mediated Ca(2+) transients too, they significantly reduced the amplitude of the depolarization-evoked transients in a pertussis-toxin sensitive way, indicating a Gi/o protein dependent mechanism. Concurrently, on skeletal muscle fibres isolated from CB1R-knockout animals, depolarization-evoked Ca(2+) transients, Ca(2+) release flux via ryanodine receptors (RyRs), and total amount of released Ca(2+) was significantly greater than those from wild type mice. Our results show that CB1R-mediated signalling exerts both a constitutive and an agonist-mediated inhibition on the Ca(2+) transients via RyR, regulates the activity of the sarcoplasmic reticulum Ca(2+) ATPase, and enhances muscle fatigability, which might decrease exercise performance, play a role in myopathies, and should, therefore, be considered during the development of new cannabinoid drugs. This article is protected by copyright. All rights reserved.
    Full-text available · Article · Sep 2016 · The Journal of Physiology
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    [Show abstract] [Hide abstract] ABSTRACT: It is now widely recognised that changes of the intracellular calcium concentration have deep impact on the differentiation of various non-excitable cells including the elements of the vertebrate skeleton. It has become evident that purinergic signalling is one of the most ancient cellular mechanisms that can cause such alterations in the intracellular Ca2+-homeostasis, which are precisely set either spatially or temporally. Purinergic signalling is believed to regulate intracellular Ca2+-concentration of developing cartilage and skeletal muscle cells and suggested to play roles in the modulation of various cellular functions. This idea is supported by the fact that pluripotent mesenchymal cells, chondroprogenitors or muscle precursors, as well as mature chondrocytes all are capable of releasing ectonucleotides, and express various types of purinoreceptors and ectonucleotidases. The presence of the basic components of purinergic signalling proves that cells of the chondrogenic lineage can utilise this mechanism for modulating their intracellular Ca2+ concentration independently from the surrounding skeletal muscle and bone tissues, which are well known to release ectopurines during development and mechanical stress. In this review, we summarize accumulating experimental evidence supporting the importance of purinergic signalling in the regulation of chondrogenesis and during skeletal muscle formation.
    Full-text available · Article · Feb 2016 · Cell calcium
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    Adrienn Tóth 1☯ · János Fodor 1☯ · János Vincze · [...] · Ernő Zádor
    [Show abstract] [Hide abstract] ABSTRACT: The sarcoplasmic/endoplasmic reticulum Ca 2+ ATPases (SERCAs) are the main Ca 2+ pumps which decrease the intracellular Ca 2+ level by reaccumulating Ca 2+ into the sarco-plasmic reticulum. The neonatal SERCA1b is the major Ca 2+ pump in myotubes and young muscle fibers. To understand its role during skeletal muscle differentiation its synthesis has been interfered with specific shRNA sequence. Stably transfected clones showing significantly decreased SERCA1b expression (cloneC1) were selected for experiments. The expression of the regulatory proteins of skeletal muscle differentiation was examined either by Western-blot at the protein level for MyoD, STIM1, calsequestrin (CSQ), and calcineurin (CaN) or by RT-PCR for myostatin and MCIP1.4. Quantitative analysis revealed significant alterations in CSQ, STIM1, and CaN expression in cloneC1 as compared to control cells. To examine the functional consequences of the decreased expression of SERCA1b, repeated Ca 2+-transients were evoked by applications of 120 mM KCl. The significantly higher [Ca 2+ ]i measured at the 20 th and 40 th seconds after the beginning of KCl application (112±3 and 110±3 nM vs. 150±7 and 135±5 nM, in control and in cloneC1 cells, respectively) indicated a decreased Ca 2+-uptake capability which was quantified by extracting the maximal pump rate (454±41 μM/s vs. 144±24 μM/s, in control and in cloneC1 cells). Furthermore, the rate of calcium release from the SR (610±60 vs. 377±64 μM/s) and the amount of calcium released (843±75 μM vs. 576±80 μM) were also significantly suppressed. These changes were also accompanied by a reduced activity of CaN in cells with decreased SERCA1b. In parallel, cloneC1 cells showed inhibited cell proliferation and decreased myotube nuclear numbers. Moreover, while cyclosporineA treatment suppressed the proliferation of parental cultures it had no effect on cloneC1 cells. SERCA1b is thus considered to play an essential role in the regulation of [Ca 2+ ]i and its ab ovo gene silencing results in decreased skeletal muscle differentiation.
    Full-text available · Article · Apr 2015 · PLoS ONE
  • [Show abstract] [Hide abstract] ABSTRACT: The High-Mobility Group Box 1 protein (HMGB1) is a known nuclear protein which may be released from the nucleus into the cytoplasm and the extracellular space. It is believed that the mobilized HMGB1 plays role in the autoimmune processes as an alarmin, stimulating the immune response. In addition, muscle regeneration and differentiation may also be altered in the inflammatory surroundings. Biopsy specimens derived from patients with idiopathic inflammatory myopathies (IIM) such as polymyositis or dermatomyositis were compared to muscle samples from patients undergoing surgical interventions for coxarthrosis. The biopsy and surgery specimens were used for Western blot analysis, for immunohistochemical detection of HMGB1 in histological preparations and for cell culturing to examine cell proliferation and differentiation. Our data show lower HMGB1 expression, impaired proliferation and slightly altered fusion capacity in the primary cell cultures started from IIM specimens than in cultures of coxarthrotic muscles. The ratio of regenerating muscle fibres with centralised nuclei (myotubes) is lower in the IIM samples than in the coxarthrotic ones but corticosteroid treatment shifts the ratio towards the coxarthrotic value. Our data suggest that the impaired regeneration capacity should also be considered to be behind the muscle weakness in IIM patients. The role of HMGB1 as a pathogenic signal requires further investigation.
    Article · Mar 2015 · Journal of Muscle Research and Cell Motility
  • [Show abstract] [Hide abstract] ABSTRACT: TASK-3 (KCNK9 or K2P9.1) channels are thought to promote proliferation and/or survival of malignantly transformed cells, most likely by increasing their hypoxia tolerance. Based on our previous results that suggested mitochondrial expression of TASK-3 channels, we hypothesized that TASK-3 channels have roles in maintaining mitochondrial activity. In the present work we studied the effect of reduced TASK-3 expression on the mitochondrial function and survival of WM35 and A2058 melanoma cells. TASK-3 knockdown cells had depolarized mitochondrial membrane potential and contained a reduced amount of mitochondrial DNA. Compared to their scrambled shRNA-transfected counterparts, they demonstrated diminished responsiveness to the application of the mitochondrial uncoupler [(3-chlorophenyl)hydrazono]malononitrile (CCCP). These observations indicate impaired mitochondrial function. Further, TASK-3 knockdown cells presented reduced viability, decreased total DNA content, altered cell morphology, and reduced surface area. In contrast to non- and scrambled shRNA-transfected melanoma cell lines, which did not present noteworthy apoptotic activity, almost 50 % of the TASK-3 knockdown cells exhibited strong Annexin-V-specific immunofluorescence signal. Sequestration of cytochrome c from the mitochondria to the cytosol, increased caspase 3 activity, and translocation of the apoptosis-inducing factor from mitochondria to cell nuclei were also demonstrated in TASK-3 knockdown cells. Interference with TASK-3 channel expression, therefore, induces caspase-dependent and -independent apoptosis of melanoma cells, most likely via causing mitochondrial depolarization. Consequently, TASK-3 channels may be legitimate targets of future melanoma therapies.
    Article · Oct 2014 · Archives for Dermatological Research
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    [Show abstract] [Hide abstract] ABSTRACT: Presence of the pituitary adenylate cyclase-activating polypeptide (PACAP) signalling has been proved in various peripheral tissues. PACAP can activate protein kinase A (PKA) signalling via binding to pituitary adenylate cyclase-activating polypeptide type I receptor (PAC1), vasoactive intestinal polypeptide receptor (VPAC) 1 or VPAC2 receptor. Since little is known about the role of this regulatory mechanism in bone formation, we aimed to investigate the effect of PACAP on osteogenesis of UMR-106 cells. PACAP 1-38 as an agonist and PACAP 6-38 as an antagonist of PAC1 were added to the culture medium. Surprisingly, both substances enhanced protein expressions of collagen type I, osterix and alkaline phosphatase, along with higher cell proliferation rate and an augmented mineralisation. Although expression of PKA was elevated, no alterations were detected in the expression, phosphorylation and nuclear presence of CREB, but increased nuclear appearance of Runx2, the key transcription factor of osteoblast differentiation, was shown. Both PACAPs increased the expressions of bone morphogenetic proteins (BMPs) 2, 4, 6, 7 and Smad1 proteins, as well as that of Sonic hedgehog, PATCH1 and Gli1. Data of our experiments indicate that activation of PACAP pathway enhances bone formation of UMR-106 cells and PKA, BMP and Hedgehog signalling pathways became activated. We also found that PACAP 6-38 did not act as an antagonist of PACAP signalling in UMR-106 cells.
    Full-text available · Article · Aug 2014 · Journal of Molecular Neuroscience
  • A. Toth · J. Fodor · J. Vincze · [...] · L. Csernoch
    Article · Aug 2014 · Acta Physiologica
  • Article · Aug 2014 · Acta Physiologica
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    Csaba Matta · János Fodor · Nicolai Miosge · [...] · Róza Zákány
    [Show abstract] [Hide abstract] ABSTRACT: Osteoarthritis (OA) is the most common form of chronic musculoskeletal disorders. A migratory stem cell population termed chondrogenic progenitor cells (CPC) with in vitro chondrogenic potential was previously isolated from OA cartilage. Since intracellular Ca(2+) signalling is an important regulator of chondrogenesis, we aimed to provide a detailed understanding of the Ca(2+) homeostasis of CPCs. In this work, CPCs immortalised by lentiviral administration of the human telomerase reverse transcriptase (hTERT) and grown in monolayer cultures were studied. Expressions of all three IP3Rs were confirmed, but no RyR subtypes were detected. Ca(2+) oscillations observed in CPCs were predominantly dependent on Ca(2+) release and store replenishment via store-operated Ca(2+) entry; CPCs express both STIM1 and Orai1 proteins. Expressions of adenosine receptor mRNAs were verified, and adenosine elicited Ca(2+) transients. Various P2 receptor subtypes were identified; P2Y1 can bind ADP; P2Y4 is targeted by UTP; and ATP may evoke Ca(2+) transients via detected P2X subtypes, as well as P2Y1 and P2Y2. Enzymatic breakdown of extracellular nucleotides by apyrase completely abrogated Ca(2+) oscillations, suggesting that an autocrine/paracrine purinergic mechanism may drive Ca(2+) oscillations in these cells. As CPCs possess a broad spectrum of functional molecular elements of Ca(2+) signalling, Ca(2+)-dependent regulatory mechanisms can be supposed to influence their differentiation potential.
    Full-text available · Article · May 2014 · Pflügers Archiv - European Journal of Physiology
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    [Show abstract] [Hide abstract] ABSTRACT: Myostatin, a member of the transforming growth factor β family was shown to be a potent negative regulator of skeletal muscle growth, as myostatin deficient mice have a great increase in muscle mass. Yet, the physical performance of these animals is not improved but suppressed. As an explanation, alterations in the steps in excitation-contraction coupling were hypothesized and tested for on mice with the 12-bp deletion in the propeptide region of the myostatin precursor (MstnCmpt-dl1Abc or Cmpt). In voluntary wheel running control C57/BL6 mice performed better than the mutant animals in both maximal speed and total distance covered. Despite the previously described lower specific force of Cmpt animals, the pCa-force relationship, determined on chemically permeabilized fibre segments did not show any significant difference between the two mouse strains. While resting intracellular Ca2+ concentration ([Ca2+]i) measured on single intact flexor digitorum brevis (FDB) muscle fibres using Fura-2 AM was similar to control (72.0±1.7 vs. 78.1±2.9 nM, n=38 and 45), the amplitude of KCl-evoked calcium transients was smaller (360±49 vs. 222±45 nM, n=22) in the mutant strain. Similar results were obtained using tetanic stimulation and Rhod-2 AM which gave calcium transients that were smaller (2.42±0.11 vs. 2.06±0.10 ΔF/F0, n=14 and 13, respectively) on Cmpt mice. SR calcium release flux, calculated from these transients showed a reduced peak (23.7±3.0 vs. 15.8±2.1 mMs-1) and steady level (5.7±0.7 vs. 3.7±0.5 mMs-1) with no change in the peak-to-steady ratio. The amplitude and spatial spread of calcium release events detected on permeabilized FDB fibres were also significantly smaller in mutant mice. These results suggest that reduced SR calcium release underlies the reduced muscle force in Cmpt animals.
    Full-text available · Article · Jan 2014 · The Journal of Physiology
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    János Fodor · Csaba Matta · Tamás Oláh · [...] · Róza Zákány
    [Show abstract] [Hide abstract] ABSTRACT: Chondrogenesis is known to be regulated by calcium-dependent signalling pathways in which temporal aspects of calcium homeostasis are of key importance. We aimed to better characterise calcium influx and release functions with respect to rapid calcium oscillations in cells of chondrifying chicken high density cultures. We found that differentiating chondrocytes express the α1 subunit of voltage-operated calcium channels (VOCCs) at both mRNA and protein levels, and that these ion channels play important roles in generating Ca(2+) influx for oscillations as nifedipine interfered with repetitive calcium transients. Furthermore, VOCC blockade abrogated chondrogenesis and almost completely blocked cell proliferation. The contribution of internal Ca(2+) stores via store-operated Ca(2+) entry (SOCE) seems to be indispensable to both Ca(2+) oscillations and chondrogenesis. Moreover, this is the first study to show the functional expression of STIM1/STIM2 and Orai1, molecules that orchestrate SOCE, in chondrogenic cells. Inhibition of SOCE combined with ER calcium store depletion abolished differentiation and severely diminished proliferation, suggesting the important role of internal pools in calcium homeostasis of differentiating chondrocytes. Finally, we present an integrated model for the regulation of calcium oscillations of differentiating chondrocytes that may have important implications for studies of chondrogenesis induced in various stem cell populations.
    Full-text available · Article · May 2013 · Cell calcium
  • C. Matta · J. Fodor · T. Juhász · R. Zákány
    [Show abstract] [Hide abstract] ABSTRACT: It is well established that Ca2+ signalling mediates the effects of mechano-transduction in chondrocytes of mature articular cartilage. However, little is known about the precise regulation of Ca2+ homeostasis in differentiating cells of developing hyaline cartilage. Therefore, our research group is committed to characterise the Ca2+ homeostasis and to map the 'Ca2+ toolkit' of differentiating chondrogenic mesenchymal cells. High density cell culture system (HDC) established from chondrogenic mesenchymal cells isolated from limb buds of 4-day-old chicken embryos is a well-known model of in vitro cartilage differentiation, in which a spontaneous cartilage formation occurs in 6 days. We measured cytosolic free Ca2+ concentration ([Ca2+ ]i) in cells of HDC on different days of culturing. After an initial value of 80 nM, a significant transient elevation was detected in Fura-2-loaded cells on day 3 of culturing, when the majority of cells differentiate into chondroblasts and chondrocytes. This 140 nM peak of cytosolic Ca2+ concentration is a result of increased Ca2+ influx and is found to be indispensable to proper chondrogenesis, because elimination of extracellular Ca2+ abolished the Ca2+ peak of day 3 and inhibited cartilage formation. Uncontrolled Ca2+ influx evoked by a Ca2+ ionophore (A23187) exerted dual effects on chondrogenesis in a concentration-dependent manner; low concentration of the ionophore increased [Ca2+ ]i up to 150 nM and facilitated cartilage formation, whereas high concentration of this compound elevated it over 250 nM and almost totally blocked cartilage formation. Proliferation of chondrogenic cells was more sensitive to modulation of [Ca2+ ]i then the viability of cells. Although chondrogenic cells express both IP3 and ryanodine receptors and can release Ca2+ from intracellular stores, these stores proved to play a minor role in the Ca2+ homeostasis of these cells. As the inhibition of the Ca2+ -calmodulin sensitive protein phosphatase calcineurin impeded the [Ca2+ ]i-peak in chondrogenic cells and reduced cartilage formation, we propose its contribution in the regulation of [Ca2+ ]i in these cells. We also found that chondrogenic cells secreted ATP and administration of ATP to the culture medium evoked Ca2+ transients exclusively in the presence of extracellular Ca2+ and on day 3 of culturing. Moreover, ATP caused elevated protein expression of the chondrogenic transcription factor Sox9 and also stimulated cartilage matrix production. ATP may exert these functions via acting through purinergic receptors; and indeed, expression of both ionotropic (P2X) and metabotropic (P2Y) purinergic receptors were detected. Metabotropic purinergic receptor agonist UTP caused a low level (60 nM) transient elevation of [Ca2+]i in 3-day-old HDC, without having an influence on cartilage matrix production. Application of suramin, which blocks all P2X receptors but not P2X4, did not impede the effects of ATP; furthermore, P2X4 appeared in the plasma membrane of differentiating cells only from day 3. In summary, chondrogenic cells possess a set of different molecules which enable them to modulate their Ca2+ homeostasis and [Ca2+ ]i was found to be kept in a narrow range during chondrogenesis. We present evidence on a significant new regulatory mechanism of chondrogenesis with revealing the role of Ca2+ influx of chondrogenic cells via P2X4 purinergic receptors.
    Chapter · Feb 2012
  • [Show abstract] [Hide abstract] ABSTRACT: Effects of TTX (60 nM) on cartilage matrix production of HDC. (A) 60 nM TTX was applied continuously from day 1. Metachromatic cartilage areas in 6-day-old high-density colonies were visualized with DMMB dissolved in 3% acetic acid. Optical density (OD625) was determined in samples containing toluidine blue extracted with 8% HCl dissolved in absolute ethanol. Scale bar, 500 µM. (B–C) Effects of TTX treatment on the mRNA expression of Sox9, type II collagen and aggrecan on day 3, and protein expression and phosphorylation level of Sox9 in HDC on day 3 of culturing. For RT-PCR reactions, GAPDH was used as a control. (TIF)
    File available · Data · Nov 2011
  • [Show abstract] [Hide abstract] ABSTRACT: Effects of TEA (2 mM) on cartilage matrix production and proliferation of HDC. (A) 2 mM TEA was applied continuously from day 1. Metachromatic cartilage areas in 6-day-old high-density colonies were visualized with DMMB dissolved in 3% acetic acid. Optical density (OD625) was determined in samples containing toluidine blue extracted with 8% HCl dissolved in absolute ethanol. Scale bar, 500 µM. (B–C) Effects of TEA treatment on the mRNA expression of Sox9, type II collagen and aggrecan on day 3, and protein expression and phosphorylation level of Sox9 in HDC on day 3 of culturing. For RT-PCR reactions, GAPDH was used as a control. (D) Effects of TEA treatments on cellular proliferation in HDC. Assays were carried out during the administration of TEA. (TIF)
    File available · Data · Nov 2011
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    [Show abstract] [Hide abstract] ABSTRACT: Background: Understanding the key elements of signaling of chondroprogenitor cells at the earliest steps of differentiation may substantially improve our opportunities for the application of mesenchymal stem cells in cartilage tissue engineering, which is a promising approach of regenerative therapy of joint diseases. Ion channels, membrane potential and Ca(2+)-signaling are important regulators of cell proliferation and differentiation. Our aim was to identify such plasma membrane ion channels involved in signaling during chondrogenesis, which may serve as specific molecular targets for influencing chondrogenic differentiation and ultimately cartilage formation. Methodology/principal findings: Using patch-clamp, RT-PCR and Western-blot experiments, we found that chondrogenic cells in primary micromass cell cultures obtained from embryonic chicken limb buds expressed voltage-gated Na(V)1.4, K(V)1.1, K(V)1.3 and K(V)4.1 channels, although K(V)1.3 was not detectable in the plasma membrane. Tetrodotoxin (TTX), the inhibitor of Na(V)1.4 channels, had no effect on cartilage formation. In contrast, presence of 20 mM of the K(+) channel blocker tetraethyl-ammonium (TEA) during the time-window of the final commitment of chondrogenic cells reduced K(V) currents (to 27±3% of control), cell proliferation (thymidine incorporation: to 39±4.4% of control), expression of cartilage-specific genes and consequently, cartilage formation (metachromasia: to 18.0±6.4% of control) and also depolarized the membrane potential (by 9.3±2.1 mV). High-frequency Ca(2+)-oscillations were also suppressed by 10 mM TEA (confocal microscopy: frequency to 8.5±2.6% of the control). Peak expression of TEA-sensitive K(V)1.1 in the plasma membrane overlapped with this period. Application of TEA to differentiated chondrocytes, mainly expressing the TEA-insensitive K(V)4.1 did not affect cartilage formation. Conclusions/significance: These data demonstrate that the differentiation and proliferation of chondrogenic cells depend on rapid Ca(2+)-oscillations, which are modulated by K(V)-driven membrane potential changes. K(V)1.1 function seems especially critical during the final commitment period. We show the critical role of voltage-gated cation channels in the differentiation of non-excitable cells with potential therapeutic use.
    Full-text available · Article · Nov 2011 · PLoS ONE
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    Tamás Oláh · János Fodor · Sarah Oddoux · [...] · László Csernoch
    [Show abstract] [Hide abstract] ABSTRACT: To date, four isoforms of triadins have been identified in rat skeletal muscle. While the function of the 95-kDa isoform in excitation-contraction coupling has been studied in detail, the role of the 32-kDa isoform (Trisk 32) remains elusive. Here, Trisk 32 overexpression was carried out by stable transfection in L6.G8 myoblasts. Co-localization of Trisk 32 and IP(3) receptors (IP(3)R) was demonstrated by immunocytochemistry, and their association was shown by co-immunoprecipitation. Functional effects of Trisk 32 on IP(3)-mediated Ca(2+) release were assessed by measuring changes in [Ca(2+)](i) following the stimulation by bradykinin or vasopressin. The amplitude of the Ca(2+) transients evoked by 20 μM bradykinin was significantly higher in Trisk 32-overexpressing (p < 0.01; 426 ± 84 nM, n = 27) as compared to control cells (76 ± 12 nM, n = 23). The difference remained significant (p < 0.02; 217 ± 41 nM, n = 21, and 97 ± 29 nM, n = 31, respectively) in the absence of extracellular Ca(2+). Similar observations were made when 0.1 μM vasopressin was used to initiate Ca(2+) release. Possible involvement of the ryanodine receptors (RyR) in these processes was excluded, after functional and biochemical experiments. Furthermore, Trisk 32 overexpression had no effect on store-operated Ca(2+) entry, despite a decrease in the expression of STIM1. These results suggest that neither the increased activity of RyR, nor the amplification of SOCE, is responsible for the differences observed in bradykinin- or vasopressin-evoked Ca(2+) transients; rather, they were due to the enhanced activity of IP(3)R. Thus, Trisk 32 not only co-localizes with, but directly contributes to, the regulation of Ca(2+) release via IP(3)R.
    Full-text available · Article · Aug 2011 · Pflügers Archiv - European Journal of Physiology
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    Tamás Oláh · János Fodor · Olga Ruzsnavszky · [...] · László Csernoch
    [Show abstract] [Hide abstract] ABSTRACT: When the intracellular calcium stores are depleted, a Ca(2+) influx is activated to refill these stores. This store-operated Ca(2+) entry (SOCE) depends on the cooperation of several proteins as STIM1, Orai1, and, possibly, TRPC1. To elucidate this role of TRPC1 in skeletal muscle, TRPC1 was overexpressed in C2C12 cells and SOCE was studied by measuring the changes in intracellular Ca(2+) concentration ([Ca(2+)](i)). TRPC1 overexpression significantly increased both the amplitude and the maximal rate-of-rise of SOCE. When YM-58483, an inhibitor of TRPC1 was used, these differences were eliminated, moreover, SOCE was slightly suppressed. A decrease in the expression of STIM1 together with the downregulation of SERCA was confirmed by Western-blot. As a consequence, a reduction in maximal Ca(2+) uptake rate and a higher resting [Ca(2+)](i) following the Ca(2+) transients evoked by 120mM KCl were detected. Morphological changes also accompanied the overexpression of TRPC1. Differentiation of the myoblasts started later, and the myotubes were thinner in TRPC1-overexpressing cultures. For these changes the observed decrease in the nuclear expression of NFAT1 could be responsible. Our results suggest that enhanced expression of TRPC1 increases SOCE and has a negative effect on the STIM1-Orai1 system, indicating an interaction between these proteins.
    Full-text available · Article · Jun 2011 · Cell calcium
  • [Show abstract] [Hide abstract] ABSTRACT: TASK-3 channel overexpression was shown to facilitate the survival of malignantly transformed cells, possibly by providing greater hypoxia tolerance through a still unknown mechanism. Although it has been suggested previously that TASK-3 channels are expressed in the mitochondrial membranes, their role here remains elusive. In this study, a transient transfection of TASK-3 knockdown melanoma cell cultures was produced to show the significance of TASK-3 expression. Reduction of the TASK-3 protein biosynthesis induced characteristic changes in cell morphology, reduced the amount of DNA and decreased metabolic activity and mitochondrial function of melanoma cells when compared with control. These findings indicate that TASK-3 channel expression and function is indispensable for the proliferation and/or survival of the melanoma cells, as they seem to contribute to their mitochondrial functions. The significance is that, in this study, we have shown that TASK-3 channels are expressed in the mitochondria of melanoma malignum cells, and they are essential for maintaining cellular integrity and viability. The TASK-3 knockdown melanoma cell line had altered morphology, reduced DNA content, decreased metabolic activity and impaired mitochondrial function. These data indicate that TASK-3 channels are functionally present in the mitochondria of the melanoma cells, and their function is essential for the survival of these cells, thus TASK-3 channels may be the possible targets of future anticancer therapy.
    Article · Apr 2011 · Melanoma research
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    Full-text available · Article · Feb 2011 · Biophysical Journal