Maurocalcine interacts with the cardiac ryanodine receptor without inducing channel modification - Archive ouverte HAL Access content directly
Journal Articles Biochemical Journal Year : 2007

Maurocalcine interacts with the cardiac ryanodine receptor without inducing channel modification

Xavier Altafaj
  • Function : Author
Julien France
  • Function : Author
Janos Almassi
  • Function : Author
Istvan Jona
  • Function : Author
Daniela Rossi
  • Function : Author
Vincenzo Sorrentino
  • Function : Author
Kamel Mabrouk
  • Function : Author
Michel de Waard

Abstract

We have previously shown that maurocalcine (MCa), a toxin from the venom of the scorpion Maurus palmatus, binds to type 1 ryanodine receptor (RyR1) and induces strong modifications of its gating behaviour. In this study, we investigated the ability of MCa to bind on and modify the gating process of cardiac, type 2, ryanodine receptor (RyR2). By performing pull-down experiments we show that MCa directly interacts with RyR2 with an apparent affinity of 150 nM. By expressing in vitro different domains of RyR2, we show that MCa binds on two domains of RyR2 homologous to those previously identified on RyR1. The effect of MCa binding on RyR2 was then evaluated by three different approaches: i) [ 3}H]-ryanodine binding experiments, showing a very weak effect of MCa (up to 1 µM), ii) calcium release measurements from cardiac sarcoplasmic reticulum vesicles, showing that MCa up to 1 µM is unable to induce Ca 2+} release and, iii) single channel recordings, showing that MCa has no effect on the open probability or on 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 to 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.

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Dates and versions

hal-00478782 , version 1 (30-04-2010)

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Xavier Altafaj, Julien France, Janos Almassi, Istvan Jona, Daniela Rossi, et al.. Maurocalcine interacts with the cardiac ryanodine receptor without inducing channel modification. Biochemical Journal, 2007, 406 (2), pp.309-315. ⟨10.1042/BJ20070453⟩. ⟨hal-00478782⟩

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