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1.

001-es BibID:BIBFORM049403
Első szerző:Almássy János (élettanász, biológus, angol-magyar szakfordító)
Cím:Investigation of ryanodine receptor using peptide toxins / J. Almassy, S. Sarkozi, I. Jona
Dátum:2010
ISSN:0231-424X 1588-2683
Megjegyzések:Action potential of the skeletal muscle surface membrane leads to Ca2+ release from the sarcoplasmic reticulum evoked by direct coupling between dihydropyridine receptor (DHPR) and Ca2+ release channel (RyR). The structural basis of the allosteric connection is the intracellular loop between the 2nd and 3rd transmembrane repeat of the DHPR ?1 subunit. We previously showed that a ?-scorpion toxin maurocalcine (MCa) that shares primary sequence homology with the amino acid residues of DHPR-loop peptide essential for RyR activation raises single RyR channel open probability and blocks RyR in long lasting subconductive states These long lasting subconductance events characterised by mean event duration, which is about 12 secs for the wild type toxin. Using peptide where one charged amino acid (at a time) were replased with a neutral one ? wew showed that the critical amino acid is the 24th. Furtehrmore the strength of the toxin effect is proportional witht the distance of the muatted and of the 24th AA. The aimed to of this study was to confirm the hypothesis that MCa shares common binding sites with the DHPR loop peptide on RyR, and to characterize the potential effects of other MCa-homologue toxins (such as charybdotoxin (ChTx) and iberiotoxin (IbTx)) on RyR gating. Using single channel electrophysiology we demonstrated a competitive interaction between the loop peptide ? Mca and MCa ? ChTx respectively. We also found that ChTx albeit increased RyR open probability, induced long channel closures in dose-, and membrane potential- and Ca2+-dependent manner, but not in a use dependent fashion, while IbTx in spite of the significant homology was ineffective.
Tárgyszavak:Természettudományok Biológiai tudományok idézhető absztrakt
calcium release
Megjelenés:Acta Physiologica Hungarica. - 97 : 3 (2010), p. 89. -
További szerzők:Sárközi Sándor (1966-) (élettanász) Jóna István (1948-) (élettanász, fizikus)
Pályázati támogatás:81923
OTKA
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2.

001-es BibID:BIBFORM049386
Első szerző:Almássy János (élettanász, biológus, angol-magyar szakfordító)
Cím:Effect of scorpion toxins on the CRC/RyR function / Janos Almassy, Balazs Lukacs, Sandor Sarkozi, Istvan Jona
Dátum:2012
ISSN:0006-3495
Megjegyzések:It was shown previously that maurocalcin (MCa) induces long lasting subconductance states (LLSS) investigating the RyR function by single channel electrophysiology. These LLSSs are polarity and potential dependent and caused by the distinct positively charged surface formed by 5 amino acids corresponding to the peptide A binding site. We tested the effect of beta scorpion toxins - having a similar structure - on the RyR1 function. Charibdotoxin (CHTX) elicits close state at 20 nM in an all or none and voltage dependent manner because of smaller surface charge. Smaller size makes it easier to reach the most inner toxin binding site (out of the three) which causes the closure of the channel. MCa and CHTX share a common binding site which is identical to the peptide A binding site. Noxiustoxin has a similar effect at slightly higher toxin concentration. At nanomolar concentration Kaliotoxin evokes "flickering" of the channel in subconductance state which is occasionally interrupted by long lasting closed states, while locks the channel in closed state at micromolar concentration. Iberiotoxin induces a slight increase of the open probability accompanied by normal gating while Slotoxin has no effect. With the exception of MCa all toxins are effective only at one side, at the preferred side. Iberiotoxin and Slotoxin - ion spite of similar structure - have no large positive surfaces, they exhibit random surface charge distribution. A model has been proposed for the possible mode of action which accounts for the above effect of the tested toxins. Supported by Hungarian Research Found OTKA 81923.1563-PosB333
Tárgyszavak:Természettudományok Biológiai tudományok idézhető absztrakt
calcium release
Megjelenés:Biophysical Journal. - 102 : 3 (2012), p. 306a-307a. -
További szerzők:Lukács Balázs (1978-) (élettanász) Sárközi Sándor (1966-) (élettanász) Jóna István (1948-) (élettanász, fizikus)
Pályázati támogatás:81923
OTKA
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3.

001-es BibID:BIBFORM049385
Első szerző:Csernoch László (élettanász)
Cím:Estimation of Pore Geometry of RyR1 using Lanthanide Ruler / Laszlo Csernoch, Janos Almassy, Sandor Sarkozi, Balazs Lukacs, Istvan Jona
Dátum:2012
ISSN:0006-3495
Megjegyzések:It was shown previously that the Ca analogue Gd inhibits RyR1 gating symmetrically with a Kd about 5.5 microM and Hill coefficient (nH) of 4 both on cis and trans side using single channel electrophysiology. We further tested the RyR1-lanthanide interaction using two lanthanides - having an ionic radii between Ca2+ and Gd3+ - by bilayer measurements and ryanodine binding experiments. Cis inhibition of RyR1 by Eu was characterized by a binding constant of Kd=167?5 nM and an nH of 2?0.1 while trans inhibition exhibits Kd=4.8?0.2 microM and nN of 5.2?1.2. The inhibition constants for Sm on the cis side are Kd=64.3?2.5 nM and nH=2.2?0.2 while on the trans side Kd=6.15?0.13 microM and nH=4.68?0.45. Inhibition by Eu and Sm are potential and polarity dependent in contrast to Gd due to the differences in ionic radii of these lanthanides. Increasing the ionic radius from 0.938 (Gd) to 0.964 (Sm) increased the binding affinity from 5.6 microM to 64.3 nM revealing that the size of Ca binding pocket is only slightly higher than the ionic radius of Sm. Ryanodine (Ry) binding experiments revealed that lanthanides bind - at least partially - to the regulatory Ca binding site because the dose response curve of 3H Ry binding starts with an increase of Ry binding, which amounts to about 40% for Eu and 70% for Sm of basic Ry binding. A model has been proposed for one possible spatial arrangement of lanthanide and calcium binding sites of the RyR1 pore based on the ionic radii of Ca and the tested lanthanides. Supported by OTKA 81923.1557-PosB327
Tárgyszavak:Természettudományok Biológiai tudományok idézhető absztrakt
calcium release
Megjelenés:Biophysical Journal. - 102 : 3 Supplement (2012), p. 305a. -
További szerzők:Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Sárközi Sándor (1966-) (élettanász) Lukács Balázs (1978-) (élettanász) Jóna István (1948-) (élettanász, fizikus)
Pályázati támogatás:81923
OTKA
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4.

001-es BibID:BIBFORM049379
Első szerző:Lukács Balázs (élettanász)
Cím:Effect of maurocalcine on the skeletal type ryanodine receptor / Lukacs B., Sarkozi S., Almassy J., Jona I.
Dátum:2012
Megjegyzések:Maurocalcine (MCa) is a 33 amino acid long scorpion toxin which shows high homology with dihydropyridine receptor constituent peptide-A (pepA). The latter is believed to directly interact with ryanodine receptor (RyR1) and plays important role in the electromechanical coupling. The position and the positive charge of given amino acids residues of MCa are determinative in this interaction.We studied the effect of pepA and potassium ion on the MCa evoked Long Lasting Subconductance State (LLSS) type RyR1 operation assuming that both of them may have access to MCa binding sites of the channel. To investigate the binding of these peptides to RyR1, we used heavy sarcoplasmic reticulum vesicles (HSR) and CHAPS solubilized ryanodine receptor complex of rabbit skeletal muscle. Gating of RyR1 was monitored on channels incorporated into a planar lipid bilayer under voltage clamp conditions. Ca2+-release measurements were performed on HSR, where changes in extravesicular Ca2+ concentration were followed as changes in the absorption of APIII Ca2+-sensitive dye (?=710 nm).In single channel experiments LLSS type RyR1 gating was evoked applying of 5 and 10 nM MCa in the cytoplasmic side of the channel. The length and frequency of the characteristic subconductance states gradually ceased by consecutively added K+. The half effective concentration of K+ was higher at 10 nM MCa concentration which refers to a possible competition between MCa and potassium ion in biding to the same site on RyR1. A similar competitive-like effect of pepA was observed, when in the presence of 26 ?M pepA, much higher concentration of MCa was able to evoke LLSSs. In Ca2+ release measurements 5 nM MCa induced Ca2+-release at 100 mM K+, but release was completely eliminated at 250 mM K+. High concentration of K+inhibited only the MCa induced Ca2+-release but had no effect on the 4-CMC induced Ca2+-release suggesting specific effect of K+ on MCa-RyR1 interaction. Suppression of release in the presence of 250 mM K+ was inhibited by addition of higher concentration of MCa suggesting charge driven interaction between MCa and RyR1.Our data put forward a possible mode of MCa action with 3 binding sites at the cytosolic side on RyR1. The first binding site located on the surface of the channel, and is responsible for the Po increase at low MCa concentration. The second binding site in the pore of the channel induces potential- and voltage dependent LLSS-s at higher toxin concentration. Occupy of third one which located presumably in the pore, close to the selectivity filter results in closed states of RyR1.Supported by: OTKA 81923
Tárgyszavak:Természettudományok Biológiai tudományok idézhető absztrakt
calcium release
Megjelenés:Acta Physiologica. - 205 : Suppl. 690 (2012), 26. p. -
További szerzők:Sárközi Sándor (1966-) (élettanász) Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Jóna István (1948-) (élettanász, fizikus)
Pályázati támogatás:81923
OTKA
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5.

001-es BibID:BIBFORM004115
Első szerző:Lukács Balázs (élettanász)
Cím:Charged surface area of maurocalcine determines its interaction with the skeletal ryanodine receptor / Balazs Lukacs, Monika Sztretye, Janos Almassy, Sandor Sarkozi, Beatrix Dienes, Kamel Mabrouk, Cecilia Simut, Laszlo Szabo, Peter Szentesi, Michel De Waard, Michel Ronjat, Istvan Jona, Laszlo Csernoch
Dátum:2008
Megjegyzések:The 33 amino acid scorpion toxin maurocalcine (MCa) has been shown to modify the gating of the skeletal-type ryanodine receptor (RyR1). Here we explored the effects of MCa and its mutants ([Ala(8)]MCa, [Ala(19)]MCa, [Ala(20)]MCa, [Ala(22)]MCa, [Ala(23)]MCa, and [Ala(24)]MCa) on RyR1 incorporated into artificial lipid bilayers and on elementary calcium release events (ECRE) in rat and frog skeletal muscle fibers. The peptides induced long-lasting subconductance states (LLSS) on RyR1 that lasted for several seconds. However, their average length and frequency were decreased if the mutation was placed farther away in the 3D structure from the critical (24)Arg residue. The effect was strongly dependent on the direction of the current through the channel. If the direction was similar to that followed by calcium during release, the peptides were 8- to 10-fold less effective. In fibers long-lasting calcium release events were observed after the addition of the peptides. The average length of these events correlated well with the duration of LLSS. These data suggest that the effect of the peptide is governed by the large charged surface formed by residues Lys(20), Lys(22), Arg(23), Arg(24), and Lys(8). Our observations also indicate that the results from bilayer experiments mimic the in situ effects of MCa on RyR1.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Biophysical Journal. - 95 : 7 (2008), p. 3497-3509. -
További szerzők:Sztretye Mónika (1981-) (élettanász, elektrofiziológus) Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Sárközi Sándor (1966-) (élettanász) Dienes Beatrix (1972-) (élettanász, molekuláris biológus) Mabrouk, Kamel Simut, Cecilia Szabó László (Románia) Szentesi Péter (1967-) (élettanász) De Waard, Michel Ronjat, Michel Jóna István (1948-) (élettanász, fizikus) Csernoch László (1961-) (élettanász)
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6.

001-es BibID:BIBFORM069230
035-os BibID:(WoS)000402119300013 (Scopus)85019695207
Első szerző:Sárközi Sándor (élettanász)
Cím:Lanthanides Report Calcium Sensor in the Vestibule of Ryanodine Receptor / Sárközi Sándor, Komáromi István, Jóna István, Almássy János
Dátum:2017
ISSN:0006-3495
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Biophysical Journal. - 112 : 10 (2017), p. 2127-2137. -
További szerzők:Komáromi István (1957-) (vegyész, molekuláris biológus, biokémikus) Jóna István (1948-) (élettanász, fizikus) Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító)
Pályázati támogatás:PD 112199
OTKA
81923
OTKA
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7.

001-es BibID:BIBFORM049410
Első szerző:Sárközi Sándor (élettanász)
Cím:Effects of a calcium chelator TPEN on sarcoplasmic reticulum calcium release ryanodine receptor channel / S. Sarkozi, J. Almassy, C. Szegedi, I. Jona
Dátum:2005
Megjegyzések:The aim of the study was to determine the effects of a widely used calcium and zinc chelator TPEN (N,N,N?,N?-Tetrakis (2-pyridylmethyl) ethylendiamine) on skeletal muscle sarcoplasmic reticulum (SR) Ca2+ release channel (RyR). Investigations of TPEN-buffered glioblastoma cells resulted in controversial consequences raised the question if TPEN has any influence on the Ca2+ transport mechanisms of the SR. To clarify if RyRs are concerned in the putative action of TPEN isolated Ca2+ release channels were reconstituted into planar lipid bilayers and the gating behaviour of incorporated channels was studied. TPEN altered the RyR gating in a dose-, polarity- and voltage-dependent manners. These effects were proved to be dual:if the applied holding potential induced current was opposite of the direction occurring physiologically through the RyR TPEN closed the channel in potential dependent way. This result suggests that positively charged TPEN works as a plug and acting so directly blocks RyR's pore. Oppositely, when the direction of the current flowing through the incorporated RyR was of the same during Ca2+ release from SR TPEN slightly activated RyR by increasing the open probability of the channel.
Tárgyszavak:Természettudományok Biológiai tudományok idézhető absztrakt
calcium release
Megjelenés:Journal of Muscle Research and Cell Motility. - 26 (2005), p. 62. -
További szerzők:Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Szegedi Csaba Jóna István (1948-) (élettanász, fizikus)
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8.

001-es BibID:BIBFORM001050
Első szerző:Sárközi Sándor (élettanász)
Cím:Effect of natural phenol derivatives on skeletal type sarcoplasmic reticulum Ca2+ -ATPase and ryanodine receptor / Sárközi S., Almássy J., Lukács B., Dobrosi N., Nagy G., Jóna I.
Dátum:2007
Megjegyzések:The effect of natural phenol derivatives was studied on skeletal type sarcoplasmic reticulum Ca2+-ATPase and ryanodine receptor. The majority of the tested derivatives exerted inhibitory effect on the Ca2+-ATPase with an ascending sequence in regard to their effectiveness (IC50): cineole (3.33 mM) < ortho-vanillin (IC50 =1.13 mM) < 4-methyl-2-nitrophenol (1104 mu M) < vanillin (525 mu M) < thymol (224 mu M) < carvacrol (162 mu M). In two cases biphasic characteristic was observed: trans-anethole and meta-anisaldehyde first caused activation followed by inhibition (with IC50-s of 141 and 1903 mu M respectively) as their concentration was increased. In some cases (cineole, ortho-vanillin, meta-anisaldehyde) total inhibition of Ca2+-ATPase could not be reached as the result of the limited solubility of these drugs. Para-anisaldehyde and 6-amino-meta-cresol did not show any effect up to 3 mM. In Ca2+ release experiments drugs were applied on heavy sarcoplasmic reticulum vesicles isolated from skeletal muscle and actively loaded with calcium. Only thymol and carvacrol were able to evoke Ca2+ release with EC50 values of 158 +/- 16 and 211 +/- 55 mu M respectively. Futhermore the effect of thymol and carvacrol was tested on the isolated ryanodine receptor incorporated into artificial lipid bilayer. Both drugs activated the RyR when applied in concentrations identical to their EC50 values. These observations show that small differences in the structure of phenol derivatives sometimes have little impact on their effect on the sarcoplasmic reticulum Ca2+-ATPase or ryanodine receptor (thymol and carvacrol) whereas in certain cases they can completely abolish a particular effect (para- and meta-anysaldehide).
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
egyetemen (Magyarországon) készült közlemény
Megjelenés:Journal of Muscle Research and Cell Motility 28 (2007), p. 167-174. -
További szerzők:Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Lukács Balázs (1978-) (élettanász) Dobrosi Nóra (1981-) (molekuláris biológus) Nagy Georgina (1980-) (orvosbiológus) Jóna István (1948-) (élettanász, fizikus)
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9.

001-es BibID:BIBFORM086075
035-os BibID:(cikkazonosító)102213 (Scopus)85084348337 (WOS)000533610200001 (PubMed)32408025
Első szerző:Skaliczki Marianna
Cím:4-chloro-orto-cresol activates ryanodine receptor more selectively and potently than 4-chloro-meta-cresol / Mariann Skaliczki, Balázs Lukács, Zsuzsanna É. Magyar, Tünde Kovács, Miklós Bárdi, Szabolcs Novák, Gyula Diszházi, Sándor Sárközi, Ildikó Márton, Judit Péli-Szabó, István Jóna, Péter Nánási, János Almássy
Dátum:2020
ISSN:0143-4160
Megjegyzések:In this study we performed the comprehensive pharmacological analysis of two stereoisomers of 4-chloro-meta-cresol (4CMC), a popular ryanodine receptor (RyR) agonist used in muscle research. Experiments investigating the Ca2+-releasing action of the isomers demonstrated that the most potent isomer was 4-chloro-orto-cresol (4COC) (EC50 = 55 ? 14 ?M), although 3-chloro-para-cresol (3CPC) was more effective, as it was able to induce higher magnitude of Ca2+ flux from isolated terminal cisterna vesicles. Nevertheless, 3CPC stimulated the hydrolytic activity of the sarcoplasmic reticulum ATP-ase (SERCA) with an EC50 of 91 ? 17 ?M, while 4COC affected SERCA only in the millimolar range (IC50 = 1370 ? 88 ?M). IC50 of 4CMC for SERCA pump was 167 ? 8 ?M, indicating that 4CMC is not a specific RyR agonist either, as it activated RyR in a similar concentration (EC50 = 121 ? 20 ?M). Our data suggest that the use of 4COC might be more beneficial than 4CMC in experiments, when Ca2+ release should be triggered through RyRs without influencing SERCA activity.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Skeletal muscle
Ryanodine receptor
SERCA
4-chloro-meta-cresol
Chloro-orto-cresol
3-chloro-para-cresol
Megjelenés:Cell Calcium. - 88 (2020), p. 102213. -
További szerzők:Lukács Balázs (1978-) (élettanász) Magyar Zsuzsanna Édua (1993-) (molekuláris biológus) Kovács Tünde (1990-) (biokémikus, molekuláris biológus) Bárdi Miklós Novák Szabolcs Diszházi Gyula (1992-) (gyógyszerész) Sárközi Sándor (1966-) (élettanász) Márton Ildikó (1954-) (fogszakorvos) Péli-Szabó Judit (1977-) (vegyész) Jóna István (1948-) (élettanász, fizikus) Nánási Péter Pál (1956-) (élettanász) Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító)
Pályázati támogatás:GINOP-2.3.2-152016-00040
GINOP
EFOP-3.6.2-16-2017-00006
EFOP
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10.

001-es BibID:BIBFORM001082
Első szerző:Szigeti Gyula (élettanász, elektrofiziológus)
Cím:Alterations in the calcium homeostasis of skeletal muscle from postmyocardial infarcted rats / Gyula Péter Szigeti, János Almássy, Mónika Sztretye, Beatrix Dienes, László Szabó, Péter Szentesi, Guy Vassort, Sándor Sárközi, László Csernoch, István Jóna
Dátum:2007
ISSN:0031-6768
Megjegyzések:In chronic heart failure, skeletal muscles develop a weakness that is not associated to an impaired circulatory function but rather to alterations in the skeletal muscle fibers themselves. To understand these changes, the steps in excitation-contraction coupling of rats that underwent a left anterior coronary artery occlusion were studied. About 24 weeks after the myocardial infarction, neither the total amount nor the voltage dependence of intramembrane charge were altered. In contrast, calcium release from the sarcoplasmic reticulum was considerably suppressed, and its voltage dependence shifted toward more positive voltages. Elementary calcium-release events showed altered morphology as the relative proportion of embers increased. Calcium sparks were smaller in amplitude and had larger time-to-peak values. Isolated ryanodine receptors (RyR) displayed an unusual rectification with increased single-channel conductance at positive (cis vs trans) voltages. In addition, the bell-shaped calcium dependence of channel activity was broader, with a slight shift of activation to lower and a larger shift in inactivation to higher calcium concentrations. These data indicate that the number of channels that open during a calcium-release event is decreased and that RyR function is altered; thus, calcium-release is suppressed after a myocardial infarction. These observations give an explanation for the impaired skeletal muscle function in these animals.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Pflügers Archiv. - 455 : 3 (2007), p. 541-553. -
További szerzők:Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Sztretye Mónika (1981-) (élettanász, elektrofiziológus) Dienes Beatrix (1972-) (élettanász, molekuláris biológus) Szabó László (orvos) Szentesi Péter (1967-) (élettanász) Vassort, Guy Sárközi Sándor (1966-) (élettanász) Csernoch László (1961-) (élettanász) Jóna István (1948-) (élettanász, fizikus)
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