Role of Cysteine-3602 in the Function and Regulation of the Cardiac Ryanodine Receptor

The cardiac Ca2+ release channel (ryanodine receptor type 2, RyR2) is modulated by sulfhydryl reactive agents, but the molecular basis of RyR2 modulation by sulfhydryl reagents is poorly understood. Cysteine-3635 in the skeletal muscle ryanodine receptor (RyR1) is one of the most hyperreactive sulfhydryls and is important for the redox and calmodulin regulation of the RyR1 channel. However, little is known about the role of the corresponding cysteine residue in RyR2 (C3602) in the function and regulation of the RyR2 channel. Here we assessed the impact of mutating C3602 (C3602A) on store overload induced Ca2+ release (SOICR) and the regulation of RyR2 by sulfhydryl reagents and calmodulin. We found that the C3602A mutation suppressed SOICR by raising the activation threshold and delayed the termination of Ca2+ release by reducing the termination threshold. As a result, C3602A markedly increased the fractional Ca2+ release. Furthermore, the C3602A mutation diminished the inhibitory effect of N-ethylmaleimide on Ca2+ release, but it had no effect on the stimulatory action of 4,4’-dithiodipyridine on Ca2+ release. In addition, C3602 mutations (C3602A or C3602R) did not abolish the effect of calmodulin on Ca2+ release termination. Therefore, RyR2-C3602 is a major site mediating the action of sulfhydryl alkylating agent N-ethylmaleimide, but not the action of the oxidant 4,4’-dithiodipyridine. Our data also indicate th...

Source: BJ Cell - January 21, 2015 Category: Biochemistry Authors: T Mi, Z Xiao, W Guo, Y Tang, F Hiess, J Xiao, Y Wang, J Z Zhang, L Zhang, R Wang, P P Jones, S Chen Tags: BJ Biomolecules Source Type: research