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001-es BibID:	BIBFORM049405
Első szerző:	Altafaj, Xavier
Cím:	The scorpion toxin maurocalcine; a tool to study the excitation-contraction coupling in skeletal muscle / X. Altafaj, K. Mabrouk, I. Jona, L. Csernoch, M. De Waard, M. Ronjat
Dátum:	2004
Megjegyzések:	Maurocalcine (MCa) ? isolated from the venom of the Scorpio Maurus Palmatus has been described as an extremely potent modulator of the sarcoplasmic reticulum calcium release channel (CRC/RyR). Using single channel bilayer electrophysiology and confocal laser scanning microscopy we have shown that MCa is capable of altering the open probability and the gating characteristics of CRC/RyR by inducing long lasting subconductance states (LLSS). LLSS can last for several seconds. In parallel MCa induces complex event of calcium release in line-scan images. Using mutants of MCa we have demonstrated that the surface charge and/or charge distribution is the most important single parameter of the MCa effect. Altering even a single amino acid which destroys the positively charged area overwhelmingly influences the effect of the toxin on CRC/RyR. The effectiveness of the mutants is roughly proportionally with the real distance from the critical 24 residue. Their effects on the isolated channel and on the calcium release events were between those of the wild type and the ineffective Arg24Ala mutant.
Tárgyszavak:	Természettudományok Biológiai tudományok idézhető absztrakt calcium release
Megjelenés:	Journal of Muscle Research and Cell Motility. - 26 (2004), p. 59. -
További szerzők:	Mabrouk, Kamel Jóna István (1948-) (élettanász, fizikus) Csernoch László (1961-) (élettanász) De Waard, Michel Ronjat, Michel
Internet cím:	Szerző által megadott URL Intézményi repozitóriumban (DEA) tárolt változat
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001-es BibID:	BIBFORM001016
Első szerző:	Altafaj, Xavier
Cím:	Maurocalcine interacts with the cardiac ryanodine receptor without inducing channel modification / Altafaj X., France J., Almássy J., Jóna I., Rossi D., Sorrentino V., Mabrouk K., De Waard M., Ronjat M.
Dátum:	2007
Megjegyzések:	We have previously shown that MCa (maurocalcine), a toxin from the venom of the scorpion Maurus palmatus, binds to RyR1 (type 1 ryanodine receptor) and induces strong modifications of its gating behaviour. In the present study, we investigated the ability of MCa to bind to and modify the gating process of cardiac RyR2. By performing pull-down experiments we show that MCa interacts directly with RyR2with an apparent affinity of 150 nM. By expressing different domains of RyR2 in vitro, we show that MCa binds to two domains of RyR2, which are homologous with those previously identified on RyR1. The effect of MCa binding to RyR2 was then evaluated by three different approaches: (i) [H-3]ryanodine binding experiments, showing a very weak effect of MCa (up to 1 mu M), (ii) Ca2+ release measurements from cardiac sarcoplasmic reticulum vesicles, showing that MCa up to 1 mu M is unable to induce Ca2+ release, and (iii) single-channel recordings, showing that MCa has no effect on the open probability or on the RyR2 channel conductance level. Long-lasting opening events of RyR2 were observed in the presence of MCa only when the ionic current direction was opposite to the physiological direction, i.e. from the cytoplasmic face of RyR2 to its luminal face. Therefore, despite the conserved MCa binding ability of RyR1 and RyR2, functional studies show that, in contrast with what is observed with RyR1, MCa does not affect the gating properties of RyR2. These results highlight a different role of the MCa-binding domains in the gating process of RyR1 and RyR2.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Biochemical Journal 406 (2007), p. 309-315. -
További szerzők:	France, Julien Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Jóna István (1948-) (élettanász, fizikus) Rossi, Daniela Sorrentino, Vincenzo Mabrouk, Kamel De Waard, Michel Ronjat, Michel
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001-es BibID:	BIBFORM049069
Első szerző:	Estève, Eric
Cím:	Critical Amino Acid Residues Determine the Binding Affinity and the Ca2+ Release Efficacy of Maurocalcine in Skeletal Muscle Cells / Eric Estève, Sophia Smida-Rezgui, Sandor Sarkozi, Csaba Szegedi, Imed Regaya, Lili Chen, Xavier Altafaj, Hervé Rochat, Paul Allen, Isaac N. Pessah, Isabelle Marty, Jean-Marc Sabatier, Istvan Jona, Michel De Waard, Michel Ronjat
Dátum:	2003
ISSN:	0021-9258 1083-351X
Megjegyzések:	Maurocalcine (MCa) is a 33 amino acid residue peptide toxin isolated from the scorpion Scorpio maurus palmatus. MCa and mutated analogues were chemically synthesized, and their interaction with the skeletal muscle ryanodine receptor (RyR1) was studied on purified RyR1, sarcoplasmic reticulum (SR) vesicles, and cultured myotubes. MCa strongly potentiates [3H]ryanodine binding on SR vesicles (7-fold at pCa 5) with an apparent EC50 of 12 nm. MCa decreases the sensitivity of [3H]ryanodine binding to inhibitory high Ca2+ concentrations and increases it to the stimulatory low Ca2+ concentrations. In the presence of MCa, purified RyR1 channels show long-lasting openings characterized by a conductance equivalent to 60% of the full conductance. This effect correlates with a global increase in Ca2+ efflux as demonstrated by MCa effects on Ca2+ release from SR vesicles. In addition, we show for the first time that external application of MCa to cultured myotubes produces a cytosolic Ca2+ increase due to Ca2+ release from 4-chloro-m-cresol-sensitive intracellular stores. Using various MCa mutants, we identified a critical role of Arg24 for MCa binding onto RyR1. All of the other MCa mutants are still able to modify [3H]ryanodine binding although with a decreased EC50 and a lower stimulation efficacy. All of the active mutants produce both the appearance of a subconductance state and Ca2+ release from SR vesicles. Overall, these data identify some amino acid residues of MCa that support the effect of this toxin on ryanodine binding, RyR1 biophysical properties, and Ca2+ release from SR.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Journal of Biological Chemistry. - 278 : 39 (2003), p. 37822-37831. -
További szerzők:	Smida-Resgui, Sophia Sárközi Sándor (1966-) (élettanász) Szegedi Csaba Regaya, Imed Chen, Li-Li Altafaj, Xavier Rochat, Hervé Allen, Paul Pessah, Isaac N. Marty, Isabelle Sabatier, Jean Marc Jóna István (1948-) (élettanász, fizikus) De Waard, Michel Ronjat, Michel
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