OxyFile #252

Hydrogen peroxide stimulates the Ca2+ release channel from 
skeletal muscle sarcoplasmic reticulum.


Author:  Favero TG; Zable AC; Abramson JJ

Source:   J Biol Chem 1995 Oct 27; 270(43):25557-63

Abstract:

Hydrogen peroxide (H2O2) at millimolar concentrations induces 
Ca2+ release from actively loaded sarcoplasmic reticulum 
vesicles and induces biphasic [3H]ryanodine binding behavior. 
High affinity [3H]ryanodine binding is enhanced at concentrations 
from 100 microM to 10 mM (3-4 fold). At H2O2 concentrations 
greater than 10 mM, equilibrium binding is inhibited. H2O2 
decreased the kd for [3H]ryanodine binding by increasing 
its association rate, while having no effect on the rate 
of dissociation of [3H]ryanodine from its receptor. H2O2 
(1 mM) also reduced the EC50 for Ca2+ activation from 632 
nM to 335 nM. These effects were completely abolished in 
the presence of catalase, ruthenium red, and/or Mg2+ (Mm). 
H2O2-stimulated [3H]ryanodine binding is not further enhanced 
by either doxorubicin or caffeine. The direct interaction 
between H2O2 and the Ca2+ release mechanism was further 
demonstrated in single-channel reconstitution experiments. 
Peroxide, at submillimolar concentrations, activated the 
Ca2+ release channel following fusion of a sarcoplasmic 
reticulum vesicle to a bilayer lipid membrane. At millimolar 
concentrations of peroxide, Ca2+ channel activity was inhibited. 
Peroxide stimulation of Ca2+ channel activity was reversed 
by the thiol reducing agent dithiothreitol. Paralleling 
peroxide induced activation of ryanodine binding, Ca2+ 
transport, and single Ca2+ channel activity, it was observed 
that the ryanodine receptor formed large disulfide-linked 
protein complexes that dissociated upon addition of 
dithiothreitol.