Effects of S -Glutathionylation and S -Nitrosylation on Calmodulin Binding to Triads and FKBP12 Binding to Type 1 Calcium Release Channels

This study shows that the combination of glutathione (GSH) plus hydrogen peroxide (H₂O₂) promotes the Sglutathionylation of ryanodine receptor type 1 (RyR1) Ca²⁺ release channels, and confirms their joint S-glutathionylation and S-nitrosylation by S-nitrosoglutathione (GSNO). In addition, we show that ³⁵ S-labeled 12- kDa FK506-binding protein ([³⁵S]FKBP12) bound with a K _d of 13.1 nM to RyR1 present in triads or heavy sarcoplasmic reticulum vesicles; RyR1 S-nitrosylation by NOR-3 or GSNO, but not S-glutathionylation, specifically increased by four- to fivefold this K _d value. RyR1 redox modifications also increased the K _d of [³⁵S]calmodulin binding to triads without affecting B _max. RyR1 S-glutathionylation (induced by GSH plus H₂O₂) or RyR1 S-nitrosylation (produced by NOR-3) increased by approximately six- or twofold, respectively, the K _d of apocalmodulin (apoCaM) or Ca²⁺-calmodulin (CaCaM) binding to triads. Likewise, the combined Sglutathionylation and S-nitrosylation of RyR1 induced by GSNO increased by fourfold the K _d of CaCaM binding to triads and abolished apoCaM binding. As both FKBP12 and CaCaM inhibit RyR1, decreased FKBP12 binding to RyR1 and/or decreased CaCaM binding to either RyR1 or dihydropyridine receptor in triad preparations may cause the reported enhanced activation of Ca²⁺-induced Ca²⁺ release kinetics mediated by S-glutathionylation/S-nitrosylation. We discuss possible consequences of these redox modifications on RyR1-mediated Ca²⁺ release in physiological or pathological conditions. Antioxid. Redox Signal. 7, 870–881.